Conference Program (Pdf)

Abstracts

SiC Ceramics Heater for Free Piston Type of Stirling Engine ...... 10 A 2-Dimensional Computational Fluid Dynamics Approach to the Analysis of the Working Process of a Wankel-Type Stirling Machine ...... 10 Numerical study of the friction losses in Stirling engine heat exchangers ...... 11 A CFD Analysis of the Air Flow through the Matrix Regenerator of Stirling Engines ...... 11 Experimental and Theoretical Study of a 90-K Beta-Type Stirling Cooler with Rhombic-Drive Mechanism ...... 12 A non-conventional double acting Stirling Engine design methodology ...... 13 Figure of Merit Analysis of a Stirling Engine Regenerator Matrix through Experimental Studies ...... 13 Design, simulation, manufacture and testing of a free-piston Stirling engine electric generator ...... 14 Hybrid Stirling Engine-Adsorption Chiller for Truck APU Applications ...... 15 Mechanical design and first test results of an Ericsson engine ...... 15 Parametric optimization of a Gamma type Stirling engine ...... 16 New configuration of Medium Temperature Difference (MTD) Free-Piston Stirling Engine for Power Generation ...... 16 Assessment of the Performance of IC and Stirling engine based Micro Combine Heat and Power systems in UK residential conditions ...... 17 Regenerative Heat to Mechanical Energy Converter with Dense Working Fluid ...... 17 Design and building of a Stirling engine for microgeneration as a learning experience for future Industrial Engineers ...... 18 An Optimization Algorithm of Stirling Engine Performance for Low-Grade Heat Recovery ...... 19 How to start researching in thermoacoustics ...... 20 The Myth about Dead Volume in Stirling Engines ...... 20 Experiment of a Single-Piston Stirling Engine and its Simple Analysis ...... 21 Development of 150W at 70K Split Stirling Cryocooler for High-temperature Superconductors ...... 21 Analysis and Experiment on Exhaust Heat Recovery of a Gasoline Engine by a Stirling Engine ...... 22 A new heat driven compressor for heat pump application ...... 23 Modeling of the thermodynamic, kinematic and dynamic of a beta Stirling engine ...... 23 Which is better for regenerator matrix, metal gauze or smooth channel? ...... 24 Operating Characteristics of a Laboratory-Scale, Convertible Stirling-Vuilleumier-Hybrid CHP System Including a Reversed-Rotation Stirling Mode ...... 25 Performance of Heat-powered Unconstrained 4 Cylinder Double-acting Alpha-type Liquid Piston Stirling Cooler ...... 26 Numerical and Experimental Investigation of a MILD Combustion Burner for Stirling Engines ...... 26 A Novel Solar Cooling system Based on a Fluid Piston Convertor ...... 27 An evaluation of energy saving potentials for districts served by distributed Stirling m-CHP units ...... 28 Performance monitoring of Stirling CHP units in an industrial district in Poland ...... 29 A medium temperature solar powered Stirling engine – a case of project based learning ...... 29 Development of a Stirling engine powered by parabolic trough collectors ...... 30 Setup of an integrated Stirling Engine - Fluidized Bed (SE-FB) experimental system ...... 31 Portable solar cooker that can also generate electric power ...... 32 Characterisation and simulation of a restored V160 Stirling engine ...... 33

Performance testing of a Stirling engine, with implementation of high speed pressure measurements in the working gas channel ...... 34 Research results of the characteristics in the Stirling engine regenerator ...... 34 Analytical Modeling of Appendix Gap Losses in Stirling Cycle Machines ...... 35 Tribological study of different sealing solutions for a Stirling engine ...... 35 Numerical Analysis of Stirling Engines Using Advanced Thermodynamic Quasi-steady Approaches ...... 36 Performance Characteristics of the Vuilleumier Heat Pump ...... 37 A small-scale co-generation system fueled by wood pellets ...... 38 Preliminary design criteria of Stirling engines taking into account real gas effects ...... 39 Numerical Modelling of Free Piston Stirling Cycle Machines ...... 40 Concept of modified crank mechanism, characteristics and thermodynamic processes within the Stirling engine ...... 41 Heat exchange model in Stirling engine regenerator ...... 41 The passive generation system combined wood chip boiler and Stirling engine ...... 42 Proposal of the Performance Analysis for Stirling Engine ...... 42 Application of a transient model for simulation of a Stirling-Based CHP system ...... 43 A Meeting between Robert Stirling and Sadi Carnot in 1824 ...... 44 Tools for a Real Stirling Engine Cycle Thermodynamic Analysis ...... 45 Dynamic balance design technology for a V-type Stirling engine ...... 45 Development of a 500-W Beta-Type Stirling Engine by a Modified Non-Ideal Adiabatic Model ...... 46 Optimum design of piston rod used in Wobble Member Transmission Mechanism ...... 46 Design of an onboard auxiliary power and desalination unit powered by a Stirling engine ...... 47 Novel Auxuliary Power Unit Concept for Heavy Trucks ...... 47 Metallic materials for high temperature operation in Stirling engines ...... 47 STIRLING machine design with supplementary regenerators ...... 47 Experimental apparatus to test supplementary regenerators in STIRLING machines ...... 47

SiC Ceramics Heater for Free Piston Type of Stirling Engine

Teruyuki Akazawa a *, Koichi Hirata b, Takeshi Hoshino c and Kazuhito Fujiwara d a e-stir Co., Ltd., 3-113-1 Shimotara, Maibara City, Shiga 521-0016, JAPAN b National Maritime Research Institute,6-38-1, Shinkawa, Mitaka-shi, Tokyo 181-0004, JAPAN c Japan Aerospace Exploration Agency,7-44-1 Jindaiji Higashi-machi, Chofu-shi, Tokyo 182-8522, JAPAN d Kumamoto University Graduate School of Science and Technology,2-39-1 Kurokami, Kumamoto 860-8555, JAPAN

Abstract

Free piston Stirling engines with integrated linear alternators have the compact size and high conversion efficiency for the sake of the simplicity of mechanical movements. These engines have been developed with the conversion efficiency of 25%. The material property of ceramics heater is critical in order to achieve such high efficiency. In this paper, the successful design process of the ceramics heater is described. Temperature and stress of the ceramic heater have been calculated by the method of thermo-fluid dynamical analysis and the proper dimensions were decided. Several types of test products have also been designed and manufactured for the evaluation of actual efficiency. Heater efficiency of 63% was estimated from the analysis and the actual test data on free piston engine. It was concluded that the use of ceramics heater in Stirling engine is promising and the high performance of the engine can be realized.

*Corresponding author, e-mail address: [email protected] , tel.81:.749-53-3741

A 2-Dimensional Computational Fluid Dynamics Approach to the Analysis of the Working Process of a Wankel-Type Stirling Machine

A. Alexakis a, K. Mahkamov a * a Department of Mechanical and Construction Engineering, Faculty of Engineering and Environment, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK Abstract

The implementation of computational fluid dynamics (CFD) significantly extends capabilities for modelling of Stirling engines and allows conduction of the detailed analysis of complex heat transfer and gas dynamics processes which occur in the internal gas circuit of Stirling machines with complex configurations. In this paper a successful implementation of 2-D CFD modelling of a Wankel-type rotary Stirling machine is described. In this type of machines, unlike conventional Stirling machines, there is no fixed coupling of expansion and compression spaces. An expansion space in the Wankel type Stirling machine may be connected to different compression spaces during its operation. The standard k-ε turbulence model, with a dynamic mesh, reflecting the planetary motion of the kinematical mechanism in the Wankel machine, has been implemented for the analysis of its working process. The gas temperature and pressure variations and their distributions have been recorded during the modelling process and pressure-volume diagrams have been produced. The preliminary results of the simulation reveal that the particular mechanical configuration, which was under consideration in this paper, operates as a refrigerator/heat-pump and further work is required in order to explore the geometrical features that will result in this design arrangement functioning as an engine. It is shown that CFD can be used as the conclusive method for analyzing the operation characteristics of machines with a challenging complexity such as a Wankel-type Rotary Stirling Machine.

*Corresponding author, e-mail address: [email protected] , tel.: +44 191 2347510

Numerical study of the friction losses in Stirling engine heat exchangers

I. Barrenoa*, S.C. Costaa, M. Cordona, M. Tutar b,c, I. Urrutibeascoab, X. Gomezb, G. Castillod a CS Centro Stirling S. Coop, Aretxabaleta, Spain b Mechanical and Manufacturing Department, Engineering Faculty, Mondragon University, Spain c IKERBASQUE, Basque Foundation for Science, Bilbao, Spain d Civil Engineering, Materials and Manufacturing department, University of Malaga, Spain

Abstract

New time dependent correlation equations, to be valid for the friction coefficient calculation under the transitional reciprocating flow encountered in Stirling heat exchangers are numerically derived. Laminar and Reynolds-Averaged Navier-Stokes (RANS) equations based turbulence models are used to analyse laminar to turbulent reciprocating flow, focusing on the onset of turbulence and transitional reciprocating flow regime. The relative performance of these models in more accurately capturing the characteristics of the flow of interest is assessed in relation to overcoming the problems identified in previous numerical studies. The simulation results are compared with published and well-known experimental data for reciprocating pipe flows, indicating that the effects of the turbulence anisotropy need to be taken into account in order to accurately predict the laminar to turbulent transition. The anisotropic Reynolds stress turbulence model is selected as a best choice among the tested turbulence models for analysis of this transitory phenomenon based on the comparative qualitative and quantitative results. This model is used to evaluate the onset of turbulence in a range where the Stirling engine heat exchangers work. In the identified laminar and transitional regions, frictional losses are studied as a qualitative parameter of Stirling heat exchangers indicated power, and hence electrical power output performance to develop time dependent correlation equations. It is believed that the validated numerical model can be used with confidence for studying the transitional reciprocating flow and the obtained correlations, can be applied as a cost effective solution for the development of Stirling engine heat exchangers.

*Corresponding author, e-mail address: [email protected] , tel.: +34 943 037 948

A CFD Analysis of the Air Flow through the Matrix Regenerator of Stirling Engines

a a b b a, * Felice BELLO , Annarita VIGGIANO , Emanuele FANELLI , Giacobbe BRACCIO and Vinicio MAGI a School of Engineering, University of Basilicata, viale dell’Ateneo Lucano 10, 85100 Potenza, ITALY b ENEA, Technical Unit for Trisaia Technologies (UTTri), SS Jonica, Rotondella, ITALY

Abstract

In this paper, a thermo-fluid dynamic 3-D numerical model of the air flow through the stacked woven matrix of Stirling engines regenerators has been used to characterize the pressure drop and heat transfer through the regenerator. Firstly, an isothermal flow, at 293 K, through the porous media has been analyzed. Four different matrices have been considered, two aligned and two misaligned and the simulations have been carried out over a range of Reynolds numbers from 5 to 2000. Two friction factor correlations have been obtained for the aligned and the misaligned matrices, respectively, and the results are compared with experimental data in the literature. Following this, heat transfer between the air flow and the matrix has been considered by varying the inlet gas temperature, i.e. 500-750 K, and keeping the wall temperature of the regenerator at 300 K. In this case, the simulations have been carried out over a Reynolds number ranging from 8 to 1700 by using the misaligned matrix. The regenerator efficiency and the Nusselt number as function of Re are given. A correlation equation for Nusselt number is given and compared with experimental results in the literature.

*Corresponding author, e-mail address: [email protected] , tel.: +393293178371

Simulation of a latent heat thermal storage system within a Stirling based microCHP residential installation

Álvaro CAMPOS-CELADOR a, *, Iker GONZÁLEZ-PINO b, Tatyana BANDOS b and Luis María LÓPEZ-GONZÁLEZ c a ENEDI Research Group, Department of Thermal Engineering, Faculty of Engineering of Eibar, University of the Basque Country UPV/EHU, Avenida Otaola 29, 20600 Eibar, Spain. b ENEDI Research Group, Department of Thermal Engineering, Faculty of Engineering of Bilbao, University of the Basque Country UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao, Spain. c GI-TENECO Research Group, Area of Thermal Engineering of the Department of Mechanical Engineering, University of La Rioja, Luis de Ulloa 20, 26004 Logroño, Spain.

Abstract In this paper an innovative compact plate-based latent heat thermal energy storage system of 7.5 kWh and 0.315 m3 is integrated in a microCHP installation where the Stirling Whispergen unit runs as the prime mover. The phase change material used as the storage medium in the system is the commercially available paraffin RT60 whose phase change temperature is in the 53-61ºC range of temperature. The Whispergen unit presents a nominal thermal power of 8 kW and an electric power of 1 kW. The application whose energy loads are covered by that installation is a single-family house placed in Burgos (Spain). The paper assesses the physical integration of the storage systems and the performance of the plant and the microCHP unit using TRNSYS as the evaluation tool. The results were compared with a conventional hot water storage tank of the same volume. It is obtained that the latent heat thermal energy storage system increases the efficiency of the microCHP unit when compared to a conventional storage system, reaching up to 88.8%. Moreover, it reduces the number of ON-OFF cycles of the microCHP unit extending its life. When conventional hot water storage is considered, it was observed that the best results are obtained when the unit is arranged in series in the returning flow. In this case the efficiency of the microCHP reaches 86.7%.

*Corresponding author, e-mail address: [email protected] , tel: +34 943033053

Experimental and Theoretical Study of a 90-K Beta-Type Stirling Cooler with Rhombic-Drive Mechanism

Chin-Hsiang CHENG a *, Chu-Yin HUANG a, and Hang-Suin YANG a a Institute of Aeronautics and Astronautics, National Cheng Kung University, No.1, Ta-Shieh Road, Tainan, Taiwan 70101, R.O.C.

Abstract

In this study, a 90 K beta type Stirling cooler with rhombic drive mechanism and using pressurized helium as working fluid has been developed. In parallel, a thermodynamic model is also built. In the model, pressure drop, effectiveness of regenerator, effect of porosity, conductivity variations of working gas and cold head due to temperature change are taken in account. Heat losses by axial conduction, friction of working fluid, and shuttle loss due to displacer motion are also included in the energy equation for cold head. A parametric study under different operating and geometrical parameters such as charged pressure, operating speed, instantaneous speed fluctuation, and thermal inertia has been performed. On the other hand, experiments are conducted to measure the performance of the cooler and verify the thermodynamic model. In this study, the cooling capacity is supplied by an electric resistance heater. Results show that the cooler is able to reach 90 K no-loading temperature in ten minutes at operating speed of 1000 rpm, as using 3-atm helium as the working fluid.

*Corresponding author, e-mail address: [email protected] , tel.: 886-6-2757575 (ext. 63627)

A non-conventional double acting Stirling Engine design methodology

Marta CORDON a *, Igor BARRENO a, Germán CASTILLO b, Idoia URRUTIBEASCOA c and Xabier GOMEZ c a CS Centro Stirling S.Coop, Avda. Alava 3, 20550 Aretxabaleta, SPAIN b Civil Engineering, University of Málaga, Doctor Ortiz Ramos s/n, 29010 Málaga, SPAIN c Mechanical and Manufacturing Department, Mondragon University, Loramendi 4, 20500 Mondragón, SPAIN

Abstract Scaling rules based on dimensional analysis appears to be a useful method in order to design a new Stirling engine from another whose performance is known. Similarity concepts introduced in different publications rely on keeping invariable several dimensionless parameters, such as the temperature ratio NT, swept volume ratio k, phase angle α and normalized dead spaces µd between the prototype and the derivative, which assures that the fractional fluid mass distribution within the cycle is the same function of crank angle in both cases. In this paper, a non-conventional double acting Stirling engine has been scaled in power by means of different scaling proposals. A preliminary method, including the influence of the number of pistons, and therefore the phase angle between compression and expansion volumes has been proposed and compared with Strict Dynamic Similarity and Functional Similarity techniques developed by Organ. This preliminary design method makes both the derivative and the prototype not to be equivalent from the functional similarity point of view, which has been demonstrated by means of mass particle trajectory maps. However, it could be the starting point for those engineers who want to design a Stirling engine with different piston number than the known prototype

*Corresponding author, e-mail address: [email protected] , tel.: +34 943 037 948

Figure of Merit Analysis of a Stirling Engine Regenerator Matrix through Experimental Studies

S.C. COSTA a *, I. BARRENO a, J.A ESNAOLA b and M. TUTAR b,c a CS Centro Stirling S.Coop, Avd. Alava 3, 20550 Aretxabaleta, SPAIN b Mechanical and Manufacturing Department, Mondragon University, Loramendi 4, 20500 Mondragón, SPAIN c IKERBASQUE, Basque Foundation for Science, Bilbao, Spain

Abstract

The figure of merit is a powerful tool to evaluate and compare the performance of different Stirling engine regenerator matrices. The figure of merit is usually defined as the ratio between the heat transfer performance and the pressure drop losses through the regenerator matrix. Depending on the considerations to define this ratio, different expressions for this figure are obtained as found in the literature. The aim of this study is to compare three different figures of merit for different Stirling engine regenerator matrices and their agreement with experimental efficiency results in a micro-CHP Stirling engine. As the compared figures of merit do not correspond well with the obtained experimental results, a new preliminary figure of merit is proposed. The qualitative prediction performance for the proposed new figure of merit is not fully validated. Further experimental tests are required to confirm its validity for other types of Stirling engine regenerator matrix and configurations.

*Corresponding author, e-mail address: [email protected] , tel.:+34 943 037 948

Design, simulation, manufacture and testing of a free-piston Stirling engine electric generator

I.N. DEETLEFS a and R.T. DOBSON a a University of Stellenbosch Department of Mechanical and Mechatronic Engineering, Corner of Banghoek and Joubert Streets, 7600, Stellenbosch, WESTERN CAPE, South Africa

Abstract

Free-piston Stirling engine (FPSE) electric generators are still uncommon in the world and practical knowledge of these machines is very limited. FPSEs, unlike kinematic Stirling engines which have been researched in much greater detail, do not require a mechanism to physically link the piston and displacer. FPSEs do not exert side loads on the piston which generally means that lubrication is not required, operate at constant frequency and can achieve selfstarting. A FPSE however requires a linear electric generator as opposed to the more well known rotary electric generator. The Department of Electrical and Electronic Engineering at the University of Stellenbosch is in the process of designing a tubular, transverse flux, reciprocating linear electric generator for short stroke, high frequency applications - specifically with resonant FPSEs. The Department of Mechanical and Mechatronic Engineering at the University of Stellenbosch is currently conducting a master's degree program to manufacture a FPSE to be used with the aforementioned electric generator. This paper considers the design, theoretical simulation, manufacture and testing of a FPSE. The FPSE was manufactured around the piston and displacer of the Beale B-10B demonstrator engine by Sunpower Inc., but incorporates a linear electric generator. The theoretical simulation numerically solves the mass and energy equations for a one-dimensional network of nodes and control volumes spanning the working space of the engine. The pressure of the working fluid is assumed to be a function of time only and not its position in the working space. The equations of motion are solved to determine the motion of the piston and displacer. Force terms include pressure forces, spring forces, forces from the load and friction. Physical issues identified are the requirement of a close fit of the piston and displacer to ensure good sealing, low friction coefficient for the piston and displacer to ensure smooth motion, thermal isolation of the hot and cold spaces of the engine, adequate wear pairing materials to avoid seizing and effective heat exchangers to induce the required temperature variation of the working fluid.

*Corresponding author, e-mail address: [email protected] , tel.:+27 21 808 4268

Hybrid Stirling Engine-Adsorption Chiller for Truck APU Applications

Barry FLANNERY a *, Robert LATTIN b, Harald BERRESHEIM c and Rory F. D. MONAGHAN a a Department of Mechanical Engineering, National University of Ireland, Galway, Ireland b Bloomington, Minnesota, Minneapolis, United States c Department of Physics, National University of Ireland, Galway, Ireland, Ireland

Abstract This paper presents a feasibility study on the potential benefits of replacing conventional diesel engine- vapour compression cooling systems (DEVC) with a free-piston Stirling engine (FPSE) coupled to a zeolite- water adsorption chiller system (Z-WACS) in heavy truck auxiliary power unit (APU) and cabin A/C applications. The zeolite-water adsorption chiller in the hybrid system is driven via waste heat from the Stirling engine cooling jacket. A reduced order model of how a coupled system would perform is made based on experimental data. This study shows that, when compared to the incumbent DEVC technology, a hybrid free-piston Stirling engine system would offer lower fuel consumption, higher electrical and cooling efficiency, lower maintenance, low noise, greater fuel flexibility and lower emissions without the need for expensive exhaust after treatment. An adsorption chiller would eliminate the need for conventional refrigerants and, if appropriately designed, could utilize waste heat from the main truck engine and operate independently of the free-piston Stirling engine. A sensitivity analysis reveals that the important variables governing a Stirling- adsorption system (SAS) are capital cost, fuel cost and chiller COP. Due to the fact that no such system is currently commercially available, there are large uncertainties associated with the values used. Future work will seek to lower these uncertainties through experimental work and more detailed sub-models.

*Corresponding author, e-mail address: [email protected]

Mechanical design and first test results of an Ericsson engine

Alejandro FULA a, Luc DANDO b and Pascal STOUFFS c * a LaTEP, Université de Pau et des Pays de l’Adour, IUT, Avenue de l’Université, F-64000 Pau, France b Ingénieur conseil, Salbaget, route de Montredon, F-09240 Alzen, France c LaTEP, Université de Pau et des Pays de l’Adour, IUT, Avenue de l’Université, F-64000 Pau, France

Abstract

The “hot air engines” family includes two subgroups: the Stirling engines, which have no valves, and the Ericsson engines with valves in order to close the cylinders during the compression or the expansion processes. So, an Ericsson engine is an external heat supply engine working according to a Joule thermodynamic cycle. It is based on reciprocating piston-cylinder machines. Such engines are especially interesting for low power solar energy conversion and micro-CHP from conventional fossil fuels or from biomass. A prototype has been designed to work with air in open cycle as the working fluid. The nominal pressure ratio is 3 and the maximum operating temperature is 650 °C. The prototype expansion cylinder capacity is 0.65 dm3. The expansion cylinder bore is 80 mm, the piston stroke is 129 mm and the maximum rotation speed is 750 rpm. While designing the prototype, it has been chosen to have a single cylinder with a double- acting piston. The upper face of the piston closes the expansion space, while the lower face of the piston delimits the compression space. The double-acting piston is connected to a double contra-rotating crankshaft. Different innovative solutions have been introduced in the mechanical design of the prototype. The main difficulty in the design of a high temperature difference Ericsson engine consists in the hot part of the engine with the inlet and exhaust valves of the expansion cylinder. The technology used to guide the valves rods with a high degree of accuracy, the method used to cool different parts of the engine and to cope with differential dilatation are reported. Some preliminary experimental results are presented.

*Corresponding author, e-mail address: [email protected] , tel.: +33 5 59 40 71 24

Parametric optimization of a Gamma type Stirling engine

Ramla GHEITH a *, Fethi ALOUI b and Sassi BEN NASRALLAH a a Université de Monastir, École Nationale d’Ingénieurs de Monastir, Laboratoire LESTE, Avenue Ibn El Jazzar 5019, Monastir, TUNISIE b GEPEA UMR-CNRS 6144, École des Mines de Nantes, Département Systèmes Énergétiques et Environnement, 4 rue Alfred KASTLER BP20722 44307 Nantes Cedex 03 – France c Université de Valenciennes et du Hainaut-Cambrésis, ENSIAME, Lab. TEMPO - EA 4542, DF2T, Le Mont Houy 59313 Valenciennes Cedex 9, France

Abstract

A gamma Stirling engine using compressed air as a working fluid was experimented. It endures a charge pressure of 10 bar, provide a maximal rotation speed around 600 rpm for a maximum mechanical shaft power of 500W. The purpose of this experimental work is to determine the influencing parameters on a Gamma type Stirling engine heat exchangers. A special care was gives to the engine heat exchangers. The regenerator material and porosity are experimentally determined. Three operation parameters are choosing: heating temperature (300°C – 500°C), initial filling pressure (3bar- 8bar) and cooling water flow rate (0.2l/m – 3 l/mn). The influence of the previous parameters are presented and explained. All heat exchangers parameters are critical to the performance of the Stirling engine. The regenerator performances are the most significant for the engine. The heating temperature is the parameter that greatly affects performances of heat exchangers. The cooling water flow rate is quite affecting the Cooler but has a slight influence on other exchangers. The initial filling pressure is significant for the regenerator and for the heater.

*Corresponding author, e-mail address: [email protected] , tel.:+21650375202

New configuration of Medium Temperature Difference (MTD) Free- Piston Stirling Engine for Power Generation

Salem GHOZZI a * and Rabah BOUKHANOUF a a Department of Built Environment, University of Nottingham, Nottingham, UK.

Abstract

This papers describes the design of a low temperature Free Piston Stirling Engine (FPSE). The design uses a special fabricated bellows as mechanical springs for both the displacer and power piston. The design parameters were modelled using a second-order mathematical models that considering heat and pressure loss in the heat exchangers of the engine. The parts of a prototype model are being manufactured, yet has not been tested waiting for some accessories in request. The computer model shows that the overall thermal efficiency of the engine for a heater head temperature of 300oC will be about 10%.

*Corresponding author, e-mail address: [email protected] , tel.:+21650375202

Assessment of the Performance of IC and Stirling engine based Micro Combine Heat and Power systems in UK residential conditions

G. Gkounis a, A. Alexakis a, K. Mahkamov a *, C. Underwood a a Department of Mechanical and Construction Engineering, Faculty of Engineering and Environment, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK Abstract

Two mCHP units based on Stirling and IC engines, respectively, have been tested under transient and steady state operation conditions. The experimental results obtained on efficiencies, taking into account start-up and run down phases, were used for dynamic thermal simulations of a residential house using EnergyPlus software. A typical semi-detached house with average UK thermal and electric domestic demands was considered in simulations and the economic and ecological advantages over the application of a conventional heating system with a condensing domestic boiler were estimated. The introduction of economic incentives in the form of the government feed-in tariff scheme significantly improved the economical feasibility of the deployment of mCHP systems. The analysis carried out also demonstrates that the noticeable reduction in the carbon footprint of the house can be achieved.

*Corresponding author, e-mail address: [email protected] , tel.: +44 191 2347510

Regenerative Heat to Mechanical Energy Converter with Dense Working Fluid

Maxim GLUSHENKOV a, Martin SPRENKELER a and Alexander KRONBERG a * a Encontech B.V. P.O. Box 217, 7500 AE Enschede, The Netherlands Abstract

Regenerative heat to mechanical energy converter with a dense working fluid is proposed as a simple and economical alternative to state-of-the-art types of heat engines. Being an external combustion engine the converter can use heat sources typical of not only Stirling engines but Organic Rankine Cycle (ORC) engines as well. Various safe and environmentally friendly liquid working fluids such as water or carbon dioxide can be used in the engine. The engine is noiseless and can be fully balanced. The operation of the engine is based on a unique cycle having the same efficiency as the Carnot cycle. The engine has very simple, reliable and inexpensive design. As a result cost per kW of the engine can be much lower compared with that for contemporary Stirling and Rankine engines. The engine is more versatile than any other known prime mover and has very broad application area.

*Corresponding author, e-mail address: [email protected]

Design and building of a Stirling engine for microgeneration as a learning experience for future Industrial Engineers

Alvaro GONZALEZ a *, Amaia GOMENDIO a and Jaime GROS c a Mondragon University, Loramendi 4, 20500 Mondragón (Gipuzkoa), Spain c Member of the Circe Foundation, Mariano Esquilor Gómez, 15, 50015 Zaragoza, Spain

Abstract

The University of Mondragon has developed a Stirling Engine as a way to introduce the students into the Stirling cycle and educate them in industrial engineering. The Polytechnic School of Mondragon implements the PBL (Problem or Project Based Learning) approach [1] during the first semester of the Industrial Engineering Master Degree. This is based on a multidisciplinary project that integrates courses from different areas of knowledge: Thermal and Fluids Engineering, Electric Technology, Energetic Engineering and Industrial Safety. The main objective is to design and build a model of Stirling gamma engine for microgeneration. Students form teams to develop this project, which consists of two main parts: one academic, in which we assess the scientific-technological knowledge competence, and the second which includes a competition that encourages students´ motivation [2] to reach deep and effective learning [3]. The most efficient engine is the winner which will be displayed in the ISEC 2014 congress showroom. To begin with the project, the theoretical cycle has been analyzed in order to understand properly why the engine works. The following task has been to design and build the Stirling engine in the workshop of the university with the resources provided. This experience has been highly educative as to reach the targeted learning in this PBL [4]. We finally succeeded in building a Stirling engine consisting of a steel cylinder containing a steel displacer and a steel cylinder in which an aluminum piston moves. The final step is to set a series of sensors so that all the working parameters of the engine can be obtained and visualized. In this way, the real working cycle can be calculated, providing a more real comprehension of the engine. At the same time a generator has been connected to the engine´s crankshaft to measure the energy which can be generated and therefore its efficiency.

*Corresponding author, e-mail address: [email protected] , tel.: 658748378

An Optimization Algorithm of Stirling Engine Performance for Low- Grade Heat Recovery

Raffaele Davide GORGA a, *, Annarita VIGGIANO a, Emanuele FANELLI b, Giacobbe BRACCIO b and Vinicio MAGI a a School of Engineering, University of Basilicata, viale dell’Ateneo Lucano 10, 85100 Potenza, ITALY b ENEA,Technical Unit for Trisaia Technologies (UTTri), SS Jonica 106, km 419 + 500,75026 Rotondella (MT), ITALY

Abstract

This paper deals with the optimization of the performance of Stirling engines for power generation by recovering low-enthalpy sources. A thermodynamic model, together with a Single Objective Genetic Algorithm (SOGA) to optimize the engine performance in terms of efficiency and specific power output, has been employed. The second order Simple Analysis model has been improved by including both heat transfer through the cylinder walls and mechanical losses. The new Improved Simple Analysis (ISA) model has been validated by considering the performance of the GPU-3 engine. The overall accuracy of the simulations is satisfactory with respect to measurements available in the literature. Two cases have been studied with a temperature gap between thermal sources of 80 and 60 K, respectively. The results show that the Gamma configuration is the best choice for the recovery of low-enthalpy energy sources, since it provides, for both cases, a higher specific power output than the other configurations, with a comparable efficiency. The geometry details of the optimal engines are given, thus providing guidance for the engine design. Finally, the engine performance has been analysed by varying the hot source temperature and engine mean pressure.

*Corresponding author, e-mail address: [email protected] , tel.: 658748378

How to start researching in thermoacoustics

Jaime GROS a a CIRCE, Mariano Esquillor Gomez nº 15, 50018, Zaragoza

Abstract

This paper is intended as technical suggestions to help students starting the research in thermoacoustics. The next step after have produced sound with a glass test tube, an alcohol burner and a rudimentary stack made from steel wool, is frightening thinking in a stainless steel device with 40 bars pressurized helium inside. But it is possible to start researching thermoacoustics with air at atmospheric pressure, using standard cooper fittings, flexible plastic pipes and glass test tubes. Some low cost pressure sensors connected to a cheap microcontroller like Arduino or similar, allow you understand what happened inside your device. To encourage students to make practical devices, a variety of models of standing and traveling wave thermoacoustic engines have been developed and a serial of experiments have been written. In the firsts experiments, drawings and pictures with all the dimensions are given, and easy suggestions allow start to understand what is happend inside. In the following, a complete description of each device is presented in a DeltaEC model, and now the suggestions introduce the way to compare the results of a theoretic model with reality. With manual tools it is possible to build different layout of the engines. For example in the case of a traveling wave thermoacoustic model, making different feedback forms, different thermoacoustic cores and finally using the pressure sensors and a PC connected to the Arduino, it is possible to measure the power wasted in the resonator, the power supplied to a variable RC load and the power circulating in the feedback pipe. With these power measurements the student can optimize the engine and test the behavior of each part of the engine. All of the experiments have been written in English and Spanish and a small video in each one will be uploaded at Youtube.

*Corresponding author, e-mail address: [email protected] , tel.:34 695201304

The Myth about Dead Volume in Stirling Engines

Michael GSCHWENDTNER a, b *and George BELL c a Auckland University of Technology, Private Bag 92006, Auckland 1142, NEW ZEALAND b TS-dot Engineering Limited, Auckland 0604, NEW ZEALAND c Auckland University of Technology, Private Bag 92006, Auckland 1142, NEW ZEALAND

Abstract

The effect of dead volume on the power output and efficiency of an alpha-Stirling engine is investigated in the form of an exploratory parameter study using the 3rd order simulation software Sage. This paper aims at identifying the underlying mechanisms in order to better understand the resulting design implications of this phenomenon that is in clear contradiction to what can be found in the literature. It turns out that additional ‘passive’ dead volume that does not even take part in the heat transfer processes leads to a phase shift of the pressure, resulting in increased pV-work output, especially at lower heat source temperatures. Of even greater significance, dead volume has a positive effect on the efficiency at lower heat source temperatures by reducing the temperature swing in the heat exchangers and by bringing the gas temperatures closer to the wall temperatures of the respective heat exchangers, and thus increasing the effective temperature difference. Furthermore, to a large extent the beneficial effects of dead volume can also be achieved by changing the phase angle.

*Corresponding author, e-mail address: [email protected] , tel.: + 64 9 921 9999 (ext. 8079)

Experiment of a Single-Piston Stirling Engine and its Simple Analysis

Kazuhiro HAMAGUCHI a *, Yu ITOU, Shinji OKAMOTO a and Shunsuke FUJII a a Department of Mechanical Engineering, Meisei University, 2-1-1Hodokubo, Hino, Tokyo, 191-8506, JAPAN

Abstract

Generally, Stirling engines have either two pistons in two cylinders or two pistons in a single cylinder, and a heater, regenerator, and cooler are installed between the pistons (except for the double-acting type engine). A single-piston Stirling engine, on the other hand, consists of a single piston in a single cylinder, a cooler, a regenerator, a heater, and a gas damper. The gas damper has a role equivalent to the expansion piston or the displacer piston. Therefore, a simple prototype engine has been fabricated using air at normal atmospheric pressure as the working gas. The basic characteristics of this engine have been examined experimentally. Additionally, in the performance analysis of this engine, a simple cycle simulation using an isothermal model has been performed and compared with the experimental results. Using this simulation method, the performance of an actual single-piston Stirling engine has also been estimated. The feasibility of this actual engine has been verified experimentally and analytically.

*Corresponding author, e-mail address: [email protected]

Development of 150W at 70K Split Stirling Cryocooler for High- temperature Superconductors

Yoshikatsu Hiratsuka a * , Kyosuke Nakano a and Kenta Yumoto a a Technology Research Center, Sumitomo Heavy Industries, Ltd., 2-1-1, Yato-cho, Nishitokyo-city, Tokyo 188-8585 Japan

Abstract

Sumitomo Heavy Industries, Ltd. previously developed a high-power stirling-type pulse tube cryocooler (SPTC) designed for cooling capacity of 150 W at 70 K for the purpose of cooling high-temperature superconductor (HTS) devices, such as superconductor motors, Superconducting Magnetic Energy Storage (SMES), and current fault limiters. The experimental results of a prototype SPTC were reported in September 2013. For a U-type expander, the cooling capacity was 151 W at 70 K with a compressor input power of 4 kW [1]. Accordingly, Coefficient Of Performance (COP) was about 0.038. Pulse tube cryocoolers are more attractive for their higher reliability than other small cryocoolers, e.g., Gifford- McMahon (GM) and Stirling cryocoolers, because they have no moving parts in the expander. However, the efficiency of the cryocooler is required to be COP > 0.1, and it was found that, theoretically, it is difficult to further improve the efficiency of a STPC because the work-flow generated from the hot-end of the pulse tube cannot be recovered. Therefore, we decided to change the expander to a free-piston type from a pulse tube type. A prototype Stirling cryocooler (STC) was developed and preliminary experiments were conducted. The cooling capacity was 120 W at 70 K with a compressor input power of 2.15 kW, and COP was about 0.056. We also estimated that the cooling performance is affected by environmental factors such as the effect of the cryocooler inclination, temperature, and flowing quantity of cooling water. The detailed results are reported in this paper.

*Corresponding author, e-mail address: [email protected] , tel.+8142(468)4474

Analysis and Experiment on Exhaust Heat Recovery of a Gasoline Engine by a Stirling Engine

Yu Huang a, Wenzhi Gao a *, Guanghua Li a a StateKey Laboratory of Engines, Tianjin University, Weijin Road 92, Nankai District, Tianjin 300072, PR China

Abstract

Stirling engine is famous for its characters of clean, quiet and high efficiency and has been studied and used in certain situations, like solar thermal generation, combined heat and power generation (CHP), vehicle power engine, and radioactive power generation. With a growing demand of vehicle efficiency for regulatory constraints of CO2pollution, on-board waste heat recovery system is attracting people’s attention increasingly, and Stirling Engine is regarded as one of the most potential ways to recover waste heat efficaciously from an internal combustion engine, especially from a gasoline engine which has lower efficiency and higher exhaust gas temperature. The aim of this paper is to set up an Otto-Stirling combined cycle test bench to examine and analyzethe potential of Stirling Engine usage in waste heat recovery system (WHR). At first a mathematical model based on adiabatic analysis method and some power loss models for Stirling Engine wasprogramed for performance prediction, combined with exhaust gas parameters calculated in other model. Afterwards a test bench wasset up with the first prototype of a 0.5L expansion space rhombic Stirling Engine driven by exhaust gas of a 2.0L NA gasoline engine under certain working conditions. The gasoline engine wasset on a hydraulic dynamometer which can provide steady status and the Stirling Engine wasplaced on a position of downstream the 3-way catalyst of the gasoline engine. A maximum electric power of about 250w wasrecovered when exhaust gas reaches over 700℃, gasoline engine operatedat about 3000rpm and 90% load. Some Stirling Engine operating parameters weremonitored during experiment by placing three pressure sensors at different positions of Stirling Engine for pressure monitor and 34thermocouples are welded on heater of Stirling Engine for temperature observation. It shows great possibility for Stirling Engine usagein WHR and there are still some work remained to do for future application.

*Corresponding author, e-mail address: [email protected] , tel. +86 22 27404244

A new heat driven compressor for heat pump application

Rabah IBSAINE a, Jean-Marc JOFFROY b and Pascal STOUFFS a * a LaTEP, Université de Pau et des Pays de l’Adour, IUT, Avenue de l’Université, F-64000 Pau b boostHEAT, FUTUROPOLIS, 4 rue Maryse Hilsz, F-31500 Toulouse, France

Abstract

A new concept of thermal compressor has been designed by boostHEAT. This compressor uses thermal energy provided through the heater instead of mechanical energy to increase the pressure of the heat pump working fluid. The compressor is made up of the following parts: a cylinder with a displacer piston, a heater, a regenerator and a cooler. The heater is connected to the hot part of the cylinder on the one hand and to the regenerator on the other hand. The cooler is connected to the regenerator on the one hand and to the cold part of the cylinder on the other hand. The cold part of the cylinder is connected to the low pressure branch of the heat pump (evaporator) through an automatic inlet valve, and to the high pressure branch of the heat pump (gas cooler) through an automatic exhaust valve. The compressor is intended to replace the conventional mechanical compressor in a CO2 heat pump for the residential heating or combined heat and power market. The principle of the new thermal compressor and its advantages for heat pump application will be briefly presented. The focus will then be on a simulation model of the compressor. Several modelling results will be presented. It will be shown that due to the piston rod and the valves in the cold part of the cylinder, some mechanical energy is produced by the working fluid, so that the displacer piston of the compressor does not need to be mechanically driven by an external motor but it can be free. The importance of the regenerator and the instantaneous temperature evolution of the matrix and the fluid will also be highlighted.

*Corresponding author, e-mail address: [email protected] , tel.: +33 5 59 40 71 24

Modeling of the thermodynamic, kinematic and dynamic of a beta Stirling engine

Alexandre JACQUOT a, *, Driss KENFAUIb, Anne DAUSCHERb a Bürgerschaft 8, 79271 Sankt Peter, GERMANY b Institut Jean Lamour, CP2S, Parc de Saurupt, CS 50840 UMR 7198 CNRS - Université Lorraine, 54011 Nancy Cedex - France

Abstract

A beta Stirling engine is a rather complex thermodynamic system that is not at the thermal equilibrium. The working piston is driven by the change of pressure in the cylinder. The change of pressure itself is the result of the change of temperature of the inert working gas and enclosed in the cylinder. The temperature change of the working gas can only be calculated by accounting for the heat transfer in gas and solid phases and if the motions of the displacer and working piston are known. The challenge lies in the modelling of a Stirling engine involving multiple physical models that are coupled. The challenge is today to study these physical models in interaction. In this work, a model of a free piston beta Stirling engine developed using COMSOL Multiphysics is presented. The model is composed of a conjugate heat transfer module and a module for the mechanical system dynamic (COMSOL Multibody Dynamics Module). Conjugate heat transfer corresponds to the combination of heat transfer in solids and gases. The model is used to provide some guideline on the materials requirement and for improving the dynamics of the Stirling engine.

*Corresponding author, e-mail address: [email protected]

Which is better for regenerator matrix, metal gauze or smooth channel?

Yohei KATO a and Yoshihiko MARAMURA a* a Kanagawa University, 3-27-1 Rokkakubashi, Kanagawa-ku, 221-8686 Yokohama, JAPAN

Abstract

To reveal which is more suitable smooth channel or metal gauze for the regenerator material, experimental study was conducted. To compare material with the different dependency of length scale and flow velocity both on flow resistance and heat transfer, we first looked for the condition where pressure drop along the regenerator is the same using a single smooth channel and metal gauzes with three mesh size. We found that pressure drop for smooth channel is the same as that for #30 metal gauze at reciprocal frequency f=6.3Hz, and #16 at f=31.5Hz. As to the output work, indicated work and shaft work were both measured. Since there is a possibility that indicated work contains larger error due to the determination of phase, the shaft work for source temperature of 600°C was used to draw the conclusion. The conclusion is that smooth channel is better structure of regenerator than metal gauze.

*Corresponding author, e-mail address: [email protected] , tel.:+81-45-481-5661

Operating Characteristics of a Laboratory-Scale, Convertible Stirling- Vuilleumier-Hybrid CHP System Including a Reversed-Rotation Stirling Mode

Hans-Detlev KUEHL a *, Jens PFEIFFERb and Jan SAUERc a TU Dortmund University, Lehrstuhl für Thermodynamik, Emil-Figge-Str. 70, 44227 Dortmund, GERMANY

Abstract

A γ-Stirling engine, a Vuilleumier heat pump and a third, so-called hybrid cycle featuring both a mechanical power output and a heat pump (or refrigeration) effect can be realized in a single, convertible machine, which may profitably serve as a variable micro-CHP/heat pump system, preferably in smart grids due to its adjustable power-to-heat ratio. To first realize such a machine at a reduced experimental effort, a similarity- based scaling procedure was applied to an initial, full-scale design. Switching from Vuilleumier operation to hybrid mode is performed by disconnecting the cylinder volume on the “warm” side of the cold displacer from the cycle, and transition from hybrid to Stirling mode was initially realized by adapting the cold (supposedly ambient) temperature level to the warm level of the assumed heating circuit, leaving the cold regenerator and its adjacent heat exchangers in place for simplicity reasons, and accepting the performance degradation caused by their dead volume and flow resistance. The machine was extensively tested experimentally in these three modes, and the results could generally be well reproduced by numerical simulations, provided that some anticipated corrections were applied for the mechanical friction and thermal insulation losses, which are disproportionately increased due to the limitations of the scaling theory. Since Stirling mode operation as described above suffers from the deficiencies mentioned, a fourth operating mode, the so-called “reversed rotation Stirling mode”, was conceived and realized experimentally in this machine. In this mode, the above-mentioned cylinder volume on the warm side of the cold displacer remains connected to the cycle, and instead, the entire cold section of the Vuilleumier cycle, including the cold regenerator and the adjacent heat exchangers, is disconnected. Thus, a γ-Stirling cycle is created without the negative impact by the additional dead volume and flow resistance of these. However, to operate this cycle as an engine, the direction of crank rotation must be reversed. This could be easily realized experimentally, and a Stirling cycle featuring a significantly increased pressure amplitude and power density was obtained and investigated. These new experimental results will be presented in comparison to those obtained before. Experimental problems caused by the increased pressure amplitude unfortunately affected the brake power recording and confined the experimental schedule to reduced mean pressures.

*Corresponding author, e-mail address: [email protected] , tel.: +49-231-755-2674

Performance of Heat-powered Unconstrained 4 Cylinder Double-acting Alpha-type Liquid Piston Stirling Cooler

Samuel LANGDON-ARMS a *, Michael GSCHWENDTNER b and Martin NEUMAIER c a AUT University, 55 Wellesley St E, Auckland, 1010, NEW ZEALAND b TS-dot Engineering Limited, Auckland, 0604, NEW ZEALAND c Hochschule Rosenheim, Hochschulstraße 1, 83024 Rosenheim, GERMANY

Abstract

Presented in this paper are the preliminary results of a combined theoretical and experimental investigation into the feasibility of a heat-powered, 4-cylinder, double-acting, alpha-type, Stirling cooler utilising liquid pistons. The investigation is primarily focused on the potential for solar cooling applications. A computer model of the complex unconstrained system was constructed using the modelling software MATLAB. This was employed to predict system behaviour and was validated by experimental results from a test-rig. The results have shown the system to be self-starting at relatively low heat input temperatures and low pressures. Observed trends in operating frequency and other performance indicators are presented with their dependence on different operating configurations. Current limitations imposed by piston instability and the presence of water vapour in the gas spaces are also discussed.

*Corresponding author, e-mail address: [email protected] , tel.: +4915732482958

Numerical and Experimental Investigation of a MILD Combustion Burner for Stirling Engines

Tian Lu a *, Zhao Liu a, Yongxing Jing a, Genxiang Gu a a Shanghai Stirling Engine Engineering Technology Research Center, Shanghai, China

Abstract

An industrial oxy-fuel burner for Stirling engine operating in the MILD combustion regime through internal combustion gases recirculation (CGR) has been characterized numerically and the results of 3- D CFD was validated against experimental data on speciesratio of CGR. In the MILD combustion mode, the burner was found more homogeneous temperature distribution and dramatic decrease of temperature peak value, in compare with the characters in conventional combustion mode. The experimental results indicated the effect efficiency of Stirling engine wasalso improved in MILD combustion mode, which proved the application possibility of MILD combustion technology in Stirling engine.

*Corresponding author, e-mail address: [email protected]

A Novel Solar Cooling system Based on a Fluid Piston Convertor

Khamid Mahkamov a *, Gamal Hashem a , Basim Belgasim b, Irina Makhkamovaa

a Department of Mechanical and Construction Engineering, Faculty of Engineering and Environment, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK b Mechanical Engineering Department, Benghazi University, Benghazi, Libya

Abstract

About 15% of the global electricity production is used to actuate different kinds of conventional cooling systems. Numerous solar cooling systems are commercially available but their market penetration level is relatively low due to the high capital cost and R & D activities are ongoing to reduce these costs. Operational principles of the systems for solar water pumping and dynamic water desalination were described previously which had been built around the fluid piston converter with a simple design and made of low cost materials. In water pump and desalination systems the fluid piston converter works as an engine driven by solar thermal energy accumulated by flat- plate or evacuated tube collectors. The fluid piston converter can function as a cooling machine if the fluid piston oscillations are induced by an external source. The solar cooling system which is under investigation in this research project is made of two separate parts which are coupled together. In the first part the fluid piston converter is driven by the thermal energy accumulated by a solar collector. The kinetic energy of oscillations of the fluid piston in the engine is used to maintain oscillations of the second fluid piston converter which operates as a cooling machine in the second part of the system. Calculations carried out using a computational code in MATLAB/Simulink environment demonstrate that temperatures considerably below ambient can be achieved in the cooling part of such coupled system. The developed code can also be used to determine the rational set of design parameters of the cooling section. Preparations are underway for experimental testing and evaluation of performance of the solar cooling system.

*Corresponding author, e-mail address: [email protected] , tel.: +44 191 2347510

An evaluation of energy saving potentials for districts served by distributed Stirling m-CHP units

Emmanouil MALLIOTAKIS a *, George VOURLIOTAKIS a, Ricardo MARIN b, Alonso VICENTE b, Dimitrios GIANNOPOULOS a, Maria FOUNTI a aSchool of Mechanical Engineering, National Technical University of Athens, 9 Heroon Polytechniou Str., 15780, Athens, Greece b Ikerlan S. Coop., Paseo J.M. Arizmendiarrieta 2, 20500 Mondragon, Spain

Abstract

Achieving sustainable development in the energy sector in general and in building energy consumption in particular, requires the reduction of non-renewable primary energy input and greenhouse gas emissions. One possible developmental path is decentralization of the electricity system. The paper presents the results of an energy balance study for an innovative energy management concept for districts. According to this concept, the buildings in a district are interconnected by thermal and electric micro-grids. Heat and power are produced within district limits by a “swarm” of centrally controlled micro-CHP Stirling engines. The balance between district energy production and demand is maintained by power imports/exports to the central grid and appropriate back-up boilers. The performance of the “micro-CHP” case (gas boilers and Stirling units/back-up gas boilers) is compared to a conventional “Reference” case (individual gas boiler per building). In order to acquire realistic energy (heat) balance data, a detailed energy demand and supply simulation at district level has be performed on an hourly basis. Two district types have been considered: Residential (including Single Family Houses - SFHs) and Financial Center (including office buildings and hotels). Each district features a different heat demand profile: The residential load fluctuates intensively, while the financial district features a smoother heat load profile, with heat demand even in summer months and with a higher total thermal energy demand. The in-house developed, Matlab based, DEPOSIT software has been utilized in the present work. The importance of heat-led control is shown, especially under fluctuating demand. A clear Primary Energy Consumption (PEC) reduction potential has been identified for all cases examined, ranging from 6% up to 35%.

*Corresponding author, e-mail address: [email protected] , tel.:210-7724062

Performance monitoring of Stirling CHP units in an industrial district in Poland

Emmanouil MALLIOTAKIS a, George VOURLIOTAKIS a, Ricardo MARIN b *, Alonso VICENTE b, Dimitrios GIANNOPOULOS a, Maria FOUNTI a, Juliusz ZACH c, Bartosz STAROSIELEC c a School of Mechanical Engineering, National Technical University of Athens, 9 Heroon Polytechniou Str., 15780, Athens, Greece b Ikerlan S. Coop., Paseo J.M. Arizmendiarrieta 2, 20500 Mondragon, Spain c Mostostal Warszawa S.A., Ul Konstruktorska 11A, 02673 Warszawa, Poland, [email protected]

Abstract

The present work presents monitoring results obtained from the operation of three natural gas-fed Stirling micro-CHP engines integrated into an assembly of three interconnected industrial buildings in Warsaw, Poland. One unit with 1 kWel and 7 kWth nominal production, has been installed in each separate building. A back-up central boiler, a central heat storage tank and insulated district heating pipes are used to dynamically exchange heat between the buildings and cogeneration units, thus establishing thermal balance between heat production and consumption. Within the context of the present work, an advanced management and control system has been developed for the optimal operation of the Stirling units. User interfaces for the units have been developed, as well as new control strategy algorithms. An extensive monitoring campaign has been designed based on the measurement of several variables in the district heating installation. Monitoring took place during several months and the collected data allows for the real time calculation of the generated electrical power, the heat produced by any unit and the heat transferred to each zone/building. Analysis of the new control strategy shows the performance of the different components, of the management software and their impact on the overall operation.

*Corresponding author, e-mail address: [email protected]

A medium temperature solar powered Stirling engine – a case of project based learning

Ronald MANGION a and Martin MUSCAT a a Department of Mechanical Engineering, University of Malta, Malta

Abstract

This paper describes the design, construction and testing of a small solar powered gamma type Stirling engine within the context of a final year degree project. The main aim was to engage the student in using theoretical and practical aspects he or she had learned in various engineering topics. The objective of the project was to size, design and construct a paraboloidal dish concentrator connected to a solar powered Stirling engine. The paraboloidal dish concentrates the sun’s energy on the hot expansion side of the engine. The engine has a capacity of 196 cubic centimetres and is tested at atmospheric pressure. Variations of its torque, power and efficiency with rotational speed are presented. A comparison between the actual and the theoretically predicted performance is also made in an attempt to validate the basic equations used for the mathematical model of the engine. At the end it is concluded that the project has provided the student with a good insight of the theory and construction of a solar powered Stirling Engine.

* Corresponding author, email address: [email protected] , tel: +356 2340 2392

Development of a Stirling engine powered by parabolic trough collectors

Ronald MANGION a *, Martin MUSCAT a, Robert GHIRLANDO a, Tonio SANT a, Charles YOUSIF b and Sinan VURAL c

a Department of Mechanical Engineering, University of Malta, Msida MSD2080, Malta b Institute for Sustainable Energy, University of Malta, Malta c Sirius Systems Ltd., Lija, Malta

Abstract

Stirling engines are regaining their importance due to alternative energy challenges. In fact, they are currently being used in solar paraboloidal dish systems. Such systems are relatively bulky and therefore rather difficult to be implemented for domestic roof top purposes. In this paper a lower profile system consisting of a Stirling engine coupled to solar parabolic trough collectors was developed. The system has several advantages over a paraboloidal dish system that heats the engine directly. One such advantage is thermal storage potential which stores heat energy that can alternatively be used to generate electricity or provide auxiliary heating, depending on what is desired. The specifically designed prototype Stirling engine, SE-15, consists of a 150 mm square engine which is capable of developing 18W at an expansion space temperature of 220 °C and compression space temperature of 30 °C. This power output is quoted at a compression ratio of 1.34 and at atmospheric pressure conditions. Thermal energy is supplied to the engine by two parabolic trough collectors having an aperture of 1 m and a length of 3.2 m with a concentration ratio of 12.7.

* Corresponding author, e-mail address: [email protected] , tel: 00356 2340 2392

Setup of an integrated Stirling Engine - Fluidized Bed (SE-FB) experimental system

Francesco Saverio MARRA a *, Francesco MICCIO a, Roberto SOLIMENE a, Massimo URCIUOLO a, Riccardo CHIRONE a, Gaetano CONTINILLO b, Simone LOMBARDI b and Giorgio FUSCO c a Istituto di Ricerche sulla Combustione – CNR, P.le Tecchio 80, 80125 Napoli, ITALY b Università degli Studi del Sannio, Facoltà di Ingegneria, Piazza Roma 21, 82100 Benevento, ITALY c Aerosoft Spa, Centro Direzionale Is. E7, 80143 Napoli, ITALY

Abstract

This paper presents a new concept for the integration of a combustion chamber based on renewable fuels and a Stirling Engine (SE). Biomass is adopted as fuel to be burned in a fluidized bed (FB) combustor in the preferred form of wood pellets. This combustion technology has proven to be flexible, efficient and clean in a variety of configurations. The heat generated by combustion is used as source for the Stirling engine that converts part of the heat into mechanical and then electric energy. The novelty of the proposed setup consists in placing the heat exchanger directly into the sand bed of the fluidized combustor. This choice is motivated by the very high heat exchange coefficients attainable with the fluidized bed and by the absence of fouling due to the cleaning action exerted by the fluidized sand. A prototype system has been built to prove these concepts. The fluidized bed combustor has a square section of 290x290 mm2 in the bottom and 390x390 mm2 in the top; the total height is 1850 mm. All components are made in stainless steel. The combustor is equipped with an electric pre-heater, devices for temperature, pressure and flow measurements as well as a dedicated gas analyzer. The thermal power can be varied in the range 15-40 kW by changing the operating conditions of the fluidized bed and the fuel feeding rate. The typical operation temperature of the bed is in the range 800-850 °C. The heater of the Stirling Engine, produced by El.Ma. Srl, is immersed in the bed section of the combustor. A specifically designed support and connector, able to dump the engine oscillations and to allow the same engine to follow the movements of the insertion point determined by the thermal expansion of the combustor, has been constructed. First tests of heating-up, combustion and co-generation were performed, providing positive confirmations about the technical solutions adopted for the prototype and the possibility to achieve better performance when the SE heater is placed in contact with the hot flue gases. The system is the core of a larger research project named MEGARIS, aimed at developing a micro- cogeneration system, which is exclusively based on renewable energy sources and able to guarantee heat and electric power continuously 24 hours a day.

*Corresponding author, e-mail address: [email protected] , tel.+390815704105

Portable solar cooker that can also generate electric power

Juan Antonio MARTINEZ a *, Jaime GROS b a Navarro Santafe Technical Institute, Paraje San Benito s/n , 03400, Villena b CIRCE, Mariano Esquillor Gomez nº 15, 50018, Zaragoza, [email protected]

Abstract

Nowadays many people in the underdeveloped Countries use solar cooker to cook. The most powerful cooker among all the devices available in the market, has around a bit more than a squared meter of solar receiver, and once it is deployed it results very difficult to be moved. In addition to it, if the appliance were not going to be used for cooking forseveral hours in a day, you would waste an important amount of very usable heat. Once this issue was introduced to some students of the Navarro Santafe Technical Institute of Villena (Spain), their professor and them made the decision of both, designing and constructing a portable solar cooker, on the basis of a static standard appliance to be modified. The modified appliance has been designed to use two different heat areas where you can place different types of meal on. As a way of taking advantage of the heat surplus produced in the non cooking time, they have decided to generate electric power. The way to produce electrical power is to use a push pull double standing wave thermoacoustic engine that has been designed in partnership with CIRCE , a Research Institute part of Zaragoza University (Spain). This thermoacoustic engine uses two 125mm long ceramic stack from a car catalyst, with a 93 mm diameter each. The dimensions of the engine have been designed to allow moderate pressurization, and to make it possible to test several types of electric generators (from a commercial loudspeaker to a new design made from cheap piezoelectric transducer).

*Corresponding author. E-mail address: [email protected]

Characterisation and simulation of a restored V160 Stirling engine

Iván MESONERO a *, Susana LOPEZ a, Francisco J. GARCIA−GRANADOS b, Francisco J. JIMÉNEZ-ESPADAFOR b, David GARCIA c and Jesús-Ignacio PRIETO c a IK4-TEKNIKER,Iñaki Goenaga 5,20600 Eibar, SPAIN b Departamento de Ingeniería Energética, Escuela Técnica Superior de Ingeniería de Sevilla, Camino de los Descubrimientos s/n, 41092 Sevilla, SPAIN c University of Oviedo, Campus de Viesques, 33204Gijón, SPAIN

Abstract

The systems based on Stirling engines have the ability to use various energy sources, including multi-fuel hybrid systems, with chemical and noise pollution levels that have little competition. The potential benefits justify the competition of the Stirling engine with other technologies over the past three decades for applications such as cogeneration on industrial and domestic scales, underwater systems and air-independent propulsion of submarines, solar thermal energy conversion, and space vehicles. Despite that Stirling machines appear to have proven technological potential for some applications, they generally have not demonstrated economic potential, most likely because there are few prototypes with a variety of performance characteristics and commercial availability. The barriers that have prevented penetration of Stirling machines include cost-effectiveness, technical barriers, and market barriers. In order to overpass these barriers it is quite important to have installations and procedures able to characterise the subsystems which variables are not usually accessible. These subsystems are related mainly with the gas circuit and the drive mechanism. The IK4-TEKNIKER research centre and the University of Oviedo have collaborated since 2007 on the development of Stirling engines capable of being used for solar energy conversion and micro combined heat and power (micro-CHP). Since the beginning of this collaboration, it was considered interesting to analyse the performance of engines potentially useful for these applications. In the same way, since 2013, IK4- TEKNIKER is working in collaboration with Francisco J. García Granados, the developer of the simulation software GGSISM®, in order to evaluate his software by comparison with the experimental values obtained by IK4-TEKNIKER from the BEMS (in Spanish, the acronym means Stirling Engine Test Bench) facility, located in the Thermal Conversion Processes Area of CEDER-CIEMAT in Soria, Spain. Historically, one of the most commercially successful engines for cogeneration and solar applications was the V160, developed by United Stirling AB-Stirling Power Systems Corporation, and its updated version, the V161 (also known as SOLO161). The authors have published some independent works based mainly on experimental data obtained by other authors with these objectives: (a) to describe general procedures for internal subsystem analyses from thermal and electrical power measurements of inlet-outlet sections; (b) to obtain power and efficiency characteristic curves, and (c) to validate thermodynamic simulation programs. With similar objectives, in the present article results from the experimental characterisation work done along 2012 by IK4-TEKNIKER in the BEMS test bench are provided. The measurements were conducted on a recently restored V160F Stirling engine. This engine came from a project in the 1990s that was run by CEDER-CIEMAT in collaboration with the German company SOLO. Restoration and sensorisation related issues are described for the characterised V160F engine. From the function and operation point of view the relevant trends of the system are presented. The results from comparison between the experimental results and the simulation predictions allow enlarging the characterisation of aforementioned prototypes.

*Corresponding author, e-mail address: [email protected] , tel.:+34 943206744

Performance testing of a Stirling engine, with implementation of high speed pressure measurements in the working gas channel

Martin NILSSON a *, Patrik Wåhlin b and Anders Mattsson b a Cleanergy, Theres Svenssons Gata 15,417 55, Göteborg, SWEDEN b Chalmers University of Technology, Department of Applied Mechanics, Combustion Division, Hörsalsvägen 7, 412 96, Göteborg, SWEDEN

Abstract

A Cleanergy C9G Stirling engine genset is tested and characterized with instrumentation sufficient to perform energy balances over the system and also to investigate the gas processes in the working gas channels. Instrumentation includes both pressure and temperature sensors, the latter being both internal and external. The purpose of the test campaign was twofold. The first purpose was to characterize the engine regarding performance, energy flow and overall system efficiency. The second was to provide detailed data from the working gas channel, both pressure and temperature. This data will later be used to validate a state-of-the-art Stirling specific simulation code written in partnership by Cleanergy and Chalmers. It was concluded that the maximum local efficiency for each shaft speed appears in a specific range of mean working gas pressure common to all speeds and that shaft speed is inversely proportional to efficiency. It is also shown that the engine is better characterized by its heat input than mean working pressure.

*Corresponding author, e-mail address: [email protected]

Research results of the characteristics in the Stirling engine regenerator

Hao Peng a, Gang Xiao a, Umair Sultan a, Bingwei Shi a, Zhongyang Luo a, Kefa Cenf, Mingjiang Ni a* a State Key Laboratory of Clean Energy Utilization, Zhejiang University, 38 Zheda Road, Hangzhou 310027, China Abstract

The regenerator is one of the key parts of Stirling engine. It is useful for optimizing the design of Stirling engines and to have a comprehensive understanding of regenerators. In this work a test rig with 4kw motor has been built to investigate the flow characteristic of the regenerator under oscillating flow. Effects on oscillating flows are investigated and discussed, including oscillating frequencies (1~8Hz), gas species, gas pressures (0~4bar) and phase angles between the pistons. We found that, the phase angles do have some effect on the flow characteristics of the regenerator. Three correlation equations of maximum friction factor under oscillating flow were obtained. The friction factor obtained in this experiment is at least 2.4 times of the steady flow at the same Reynolds number.

*Corresponding author, e-mail address: [email protected]

Analytical Modeling of Appendix Gap Losses in Stirling Cycle Machines

Jens PFEIFFER a * and Hans-Detlev KUEHL a a TU Dortmund University, Lehrstuhl für Thermodynamik, Emil-Figge-Str. 70, 44227 Dortmund, GERMANY

Abstract

The design of Stirling cycle machines requires high-accuracy modeling. Recent experimental results indicate that the thermal losses associated with the cylinder system, particularly those caused by the annular gap around the displacer, have been underestimated in their influence on the engine performance. Therefore, existing models for these thermal losses, which are commonly referred to as appendix gap losses, have been reviewed. The analytical, closed form approaches are of major importance, as they may allow the derivation of practically applicable design formulas for the gap geometry. The previously available models appear to be partly based on too gross simplifications. Therefore, a new enhanced analytical model was developed and published recently. It is directly derived from the conservation laws and implies analytical solutions for the flow pattern and the temperature profile. This work discusses the previously available analytical models with regard to their underlying assumptions and accuracy, and compares them with the new modeling approach. Furthermore, the new model reveals that the diverse loss mechanisms in the cylinder system vary in magnitude along the gap, and a curved cylinder wall temperature profile is obtained, which corresponds well to former temperature measurements and numerical simulations. Therefore, the simplifying assumption of constant wall and gas temperature gradients along the gap, which is made in all previous models, is found to be inappropriate.

*Corresponding author, e-mail address: [email protected] , tel.: +49-231-755-3008

Tribological study of different sealing solutions for a Stirling engine

Bihotz PINEDO a *, Marcello CONTE b, Francesco PAGANO a, Marta CORDON c, and Amaya IGARTUA a a IK4-Tekniker, Calle Iñaki Goenaga 5, 20600 Eibar, SPAIN b Anton Paar, Rue de la Gare 4, CH-2034 Peseux, SWITZERLAND c Centro Stirling S.Coop., E-20550 Aretxabaleta, SPAIN

Abstract

In this work, three different sealing solutions for a double-acting Stirling engine were evaluated tribologically. The main objective was to characterize the seals and to compare them in terms of friction, wear and leakage. To this aim, rod seals were tested in a suitable test rig explicitly designed for sealing system characterization, reproducing as close as possible actual working conditions of a specific Stirling engine. The characterization was carried out setting up accelerated life tests, leakage tests and friction measurements. Tests were carried out at room temperature, 30 bar nitrogen supply pressure and different linear reciprocating velocities. Moreover, surface inspections were carried out after each test in order to investigate worn surfaces and identify the main wear mechanisms.

*Corresponding author, e-mail address: [email protected] , tel.: +34943206744

Numerical Analysis of Stirling Engines Using Advanced Thermodynamic Quasi-steady Approaches

Emmanouil ROGDAKIS a, Georgios ANTONAKOS a, Irene KORONAKI a and Georgios DOGKAS a* a Thermal Engineering Section, Mechanical Engineering Department,National Technical University of Athens, 9 Heroon Polytechniou St., Zografou Campus, 15773 Athens, Greece

Abstract

Stirling engines, as external combustion engines, can be powered using a variety of heat sources achieving significantly reduced emissions. Energy systems using Stirling Engines optimize their performance in specific operating conditions. Their capacity depends on the geometric characteristics of the machine, the design of the unit, the environment in which it works as well as the size of the load. Therefore, the numerical analysis of each Stirling Engine using more realistic independent variables is crucial for predicting the actual indicated power and efficiency for given engine speed, mean pressure and heater and cooler metal temperatures. The numerical model that was developed in this study is a time-dependent model of nodal analysis. The variation of the working medium temperature depends not only on time but also on pressure change, on medium mass mixture as they move between the working spaces. The analysis also takes into account the heat transfer by convection between the gas and the walls, the metal matrix temperature of the regenerator which varies spatially and temporally, the variation of the working medium pressure and the pressure drop due to friction losses. The buffer space includes working medium in high pressure and heat is transferred by conduction and excreted through the walls of the machine and to the mass of the metal matrix of the regenerator. The engine working space consists of the expansion space, the heater, the regenerator, the cooler and the compression space and it is represented by thirteen control volumes. Each of the thirteen gas control volumes is a special case of the generalized control volume. The differential equations are solved by using the leap frog technique. The computer code could be used for any type of Stirling Engine if the geometric characteristics of the specific engine, the characteristics of the working medium and the driving mechanism of the engine are considered. Initially, the convergence of the code with the GPU-3 engine was achieved while more engine types are simulated. The power at the crankshaft, the thermal load to the heater, the losses in the driving mechanism and in the regenerator are some of the variables that are investigated.

*Corresponding author, e-mail address: [email protected] , tel.:+30 210 7723671

Performance Characteristics of the Vuilleumier Heat Pump

Emmanouil ROGDAKIS a and Georgios DOGKAS a *

Thermal Engineering Section, Mechanical Engineering Department, National Technical University of Athens, 9 Heroon Polytechniou St., Zografou Campus, 15773 Athens, Greece

Abstract

The Vuilleumier Heat Pump can be viewed as a combination of two Stirling engines. The first engine operates as a refrigerator driven mechanically and thermodynamically by the second engine, which is a thermal motor. The refrigerator produces the cooling effect (i.e. it absorbs heat at low temperature), while heat is supplied to the thermal motor from an external source at high temperature. Both engines reject the total absorbed heat to the environment. The Vuilleumier Heat Pump is composed of two cylinders with displacers, two thermal regenerators, four heat exchangers, connecting passages and a mechanism to drive the displacers in the proper sequence. The development of the Vuilleumier Heat Pump has been an ongoing process aiming at the design of a well operated residential heat pump for cooling and heating. Although many prototypes have been produced, they still exhibit low performance due to inherent thermodynamic and heat transfer losses such as pumping loss, regenerator losses, heat generated by friction between displacer and cylinder, heat transfer through the cylinder wall, heat transfer through displacer and shuttle loss. An accurate description and understanding of these highly transient phenomena is required, so that different engine losses, optimal performance and design parameters can be determined. In this work the focus has been on the development of an adiabatic model taking into account complex phenomena related to compressible fluid mechanics, thermodynamics and heat transfer. A first analysis assumes ideal heat exchangers and regenerators and the effects of the mean working pressure, engine frequency and heat exchanger temperature were investigated. A case study illustrates the operation of the Vuilleumier Heat Pump according to the proposed model. For this analysis, a MathCAD© program was developed as an effective tool in the design of Vuilleumier Heat Pumps. The MathCAD© code calculates all the data at one time step for all the position steps. The flow and heat transfer characteristics of the regenerator materials are also investigated. Comparing the results obtained by this code with experimental data, an acceptable agreement can be deduced for the predicted performance of the Vuilleumier Heat Pump. Next, considering non ideal exchangers and regenerators, convection in the heat exchangers and regenerators was studied. Spatial temperature profiles for the gas inside the regenerators and the matrix were obtained. Regenerators’ effectiveness heat input and gain and C.O.P. of the heat pump were also provided by the code. Additionally, the effects of the parameters of pressure and frequency, others than that of the case study machine, were analyzed and all values are shown in suitable figures. Extra simulations for evaluating conductivity and its effect on C.O.P. were investigated. Finally, the effect of pressure drop and dissipation for conditions where the C.O.P. is maximum were also examined and illustrated.

*Corresponding author, e-mail address: [email protected] , tel.: +30 210 7723671

A small-scale co-generation system fueled by wood pellets

Takeshi SAITO a *, Kenjiro KUSU b, Yutaka MOMOSE c and Kazuhiro HAMAGUCHI a a Meisei University 2-1-1, Hodokubo, Hino, Tokyo,191-8506, JAPAN b KSK co.,Ltd, 37, Higashi-Shinkiri, Nesaki, Anjyo, Aichi, 444-1211, JAPAN c momoseMD, 1-16-9,Nihongishinmachi, Anjyo, Aichi, 446-0075, JAPAN

Abstract

The utilization of woody biomass in Japan is relatively low, and domestic energy generation techniques have not yet been established. Here, a combined heat and power system based on a Stirling engine with no external power supply was used to generate electricity and heat a greenhouse. A model of the co-generation system performance and the requirements for the greenhouse heating system is described. A combined heat and power system based on a Stirling engine was developed, and the performance was investigated by measuring the combustor exit temperature, the electricity generation, the O2 concentration, and the mass of ashes when three different types of wood pellets were used as fuel.

*Corresponding author, e-mail address: [email protected] , tel.+81-42-591-9614

Preliminary design criteria of Stirling engines taking into account real gas effects

Fernando SALA a, Constante INVERNIZZI a, David GARCIA b, Miguel−Angel GONZALEZ b and Jesús−Ignacio PRIETO b * a University of Brescia, Via Branze 38, 25123 Brescia, ITALY, [email protected] b University of Oviedo, Campus de Viesques, 33204 Gijón, SPAIN, [email protected]

Abstract

The gas circuit and the drive mechanism are the main subsystems of a Stirling engine. Models can be used to study these subsystems. The numerical computing power currently available allows the development of models with fewer simplifying assumptions than was possible decades ago. Because all models must be validated experimentally, the benefit of the advanced models is not greater accuracy but the ability to analyse physical phenomena dependent on variables whose experimental measurement is practically impossible. For now, simple models are needed at the preliminary design stage, while the advanced models can be appropriate for optimisation tasks. Beale and West numbers were probably the most commonly used criteria for sizing of engines at the preliminary design stage. Without prejudice to its historical importance, it should be recognized that both concepts are experimental correlations where great simplifications have been made. So far it has hardly been highlighted that these dimensionless numbers have two important limitations, namely: (a) do not provide criteria of independent design for the gas circuit and the drive mechanism, because they refer to brake power; and (b) do not allow to accurately estimate the maximum brake power, since there is no correlation or design criteria generally accepted to estimate the speed corresponding to the maximum brake power. In previous publications, more complete preliminary design criteria have been proposed by means of dimensional analysis, considering separately the gas circuit and the drive mechanism. In this method, the concept of quasi-static simulation and characteristic Mach number are essential for dimensioning the gas circuit, while the characteristic Stirling number is important from the standpoint of mechanical efficiency. In this article we update a database that contains the main geometric parameters, operating variables and experimental results of power and efficiency corresponding to engines of different size and characteristics. The database also includes simulation results. Since recent investigations claims that a Stirling machine operating at very high pressure and moderate maximum temperature allows the realization of small engines with significant useful power, with advantages in structural problems and the seals realization, the simulations also consider operating conditions for which the working fluid may evidence real gas effects.

The concept of dimensionless quasi-static indicated power (!0) introduced in previous work using the ideal gas model, is now substituted by the analogous concept that results from an equation of state for real gases (!!!). Both values are compared with the approximation (!!!) derived from the model of Schmidt, in order to evaluate separately how the mechanism simplification and the equation of state affect. We analyse the ratio between the dimensionless value of the maximum indicated power (a sort of ‘indicated’ Beale number) and !!!. The procedure to estimate the maximum brake power can be completed by analysing the ratio between the dimensionless rotation frequencies at the operating points of maximum brake power and maximum indicated power, as well as the values of the mechanical efficiency at the point of maximum brake power.

* Corresponding author, e-mail address: [email protected] , tel.:+34 985182081

Numerical Modelling of Free Piston Stirling Cycle Machines

Ayodeji Sowale a, Khamid Mahkamov a * a Department of Mechanical and Construction Engineering, Faculty of Engineering and Environment, Northumbria University at Newcastle, Newcastle Upon Tyne, NE1 8ST, UK Abstract

Due to their relative simplicity, higher specific power and efficiency together with a long operational life free-piston Stirling Cycle machines have been successful in progression towards commercial applications (MCHP and cooling). The work is under way at Northumbria University on a feasibility study of application of CFD modelling for the above machines. Multi-dimensional CFD modelling requires significantly longer computational times. The number of variable design and operational parameters is increased in free-piston machines due to coupling of the working process and piston dynamics and therefore it is highly desirable to derive the initial set of these parameters as accurate as possible using thermodynamic models. This work describes activities at the first stage or research work, namely the development of first and second-order thermodynamic models of free piston machines using experience acquired by one of the authors in 1980s. The first-order model is based on a combination of the Schmidt model and equations of forced harmonic oscillations of mass-spring systems. Such approach allows us to rapidly estimate the set of design and operational parameters which can then be further refined during modelling with the use of a second order technique. In the second order modelling stage differential equations of the working process and of piston dynamics solved simultaneously using Runge-Kutta 4th order method in MATLAB environment. A special attention is paid to analysis of each cycle where minimum and maximum values of such parameters as piston displacements, gas pressure, temperatures and frequency are monitored in order to determine whether a stable operation of the machine was reached during simulations. In future work, the second order model will be coupled with GA code for rapid optimisation of the machine.

*Corresponding author, e-mail address: [email protected] , tel.: +44 191 2347510

Concept of modified crank mechanism, characteristics and thermodynamic processes within the Stirling engine

Jakub STEMPKA a*, Lukasz KUBAN a, Zdzislaw KORDECKI a and Marcin KACZMARSKI a a Geocarbon Ltd., Dunikowskiego 12-14, 40-127 Katowice, POLAND, [email protected]

Abstract

The ideal Stirling cycle does have high work output, although one can observe a huge discrepancy between performance of theoretical and real engines. The power output of the real Stirling engine is relatively low. This is due to the fact that the real and the theoretical thermodynamic cycles do not overlap. The main purpose of this work is to investigate limitations that occur in different types of kinetic drive mechanisms and their impact on the single cycle. First stage of analysis is comparison of classical, harmonic (SIN) piston motion with the ideal volume variation (IVV) motion. In the following few steps a conceptual design of dual-crank mechanism is introduced (DSIN). The idea behind the dual-crank concept is to use an additional crank element that affects motion of the piston in the intended way. The solution proposed in this work reduces potential inefficiencies which come from mechanical limitations of typical drive mechanism. The dual-crank mechanism causes the thermodynamic processes of the working fluid to follow closer to the theoretical, ideal Stirling cycle. Analysis of the dual-crank mechanism performance is carried out in a course of extensive numerical simulations. The obtained results are verified and compared to the theoretical/ideal concepts and to the traditional drive mechanism. The main purpose of this paper is to present the potential and perspectives of modern aided design tools such as Computational Fluid Dynamics (CFD).

*Corresponding author, e-mail address: [email protected] , tel.:(+48) 668 338 354

Heat exchange model in Stirling engine regenerator

S.P. STOLYAROV a and R.I. KONOVAL a a STATE MARINE TECHNICAL UNIVERSITY OF St. PETERSBURG, RUSSIA

Abstract

Criterion correlations for calculation of heat exchange intensity in the matrix of Stirling engine regenerators that are made of screens or wires are presented below. Comparison of various criterion dependences for calculation of heat exchange between porous structure and working medium was carried out. Dependence for calculation of average hydraulic diameter of porous structure of regenerator matrix in the form of isotropic wire structure was derived. The method of determining heat emission ratio in regenerator matrix was offered on the basis of correlations for external wire flow-around and inner flow in the channels of irregular shape.

*Corresponding author, e-mail address: [email protected]

The passive generation system combined wood chip boiler and Stirling engine

Makoto TAKEUCHI a *, Shinji SUZUKI a and Yutaka ABE a a SUCTION GAS ENGINE MFG. CO., LTD., 6-10-4 Higashisuna Koto-ku Tokyo, 136-0074, Japan

Abstract

Wood biomass is glowing important renewable energy worldwide. Combustion efficiency of burning wood tip, pellet and fire wood has been improved remarkably. It is required that small scale power generation system can be passively worked with a high performance wood biomass boiler. In this situation, we developed a 10 kW class Low Temperature Difference Stirling Engine using thermal oil heat transfer as an indirect heating. To get sufficient power on thermal oil temperature, it uses an alpha plus type mechanism we invented specialized for a low temperature difference engine. Recently, this engine was installed into a community center of a small town. The system provide hot water and electricity on grid connection on normal period, and it is automatically changed to independent operation on a commercial power failure. This paper describes development of the engine, heat control system and electrical control system.

*Corresponding author, e-mail address: [email protected]

Proposal of the Performance Analysis for Stirling Engine

Fujio TODA a *, Shoichi IWAMOTO b a Utsunomiya University 350 Minemachi Utsunomiya,321-8505, Japan,Professor b Saitama University ,3-3-13 Tokyo Minato Ward siba 105-0014, Japan,professor Emeritus

Abstract

This paper propose new equation of indicated power which allow the rapid and accurate calculation of flow friction losses in to the heat exchanger ( heater, regenerator, cooler ) in crank-driven Stirling engine, basis of Schmidt cycle that an isothermal thermodynamic model. These equation can be calculated flow losses given to the only main dimension of engine. These formulate are derived for frictional losses in the three heat exchangers, taking in to account the variation in fluid resistance, gas flow and shaft power over the cycle. By comparing these expression with calculations quasi steady flow model, it was confirmed coincide roughly to the 10W class low-temperature difference Stirling engine.

*Corresponding author, e-mail address: [email protected] , tel.:.81-028-649-5330

Application of a transient model for simulation of a Stirling-Based CHP system

Carlos ULLOA a *, José Luis MÍGUEZ b, Jacobo PORTEIRO b, Pablo EGUÍA b, Antón CACABELOSb and Guillermo REY a a Defense University Center, The Naval Academy, Plaza de España s/n, 36920 Marín, SPAIN b Industrial Engineering School, University of Vigo, Lagoas Marcosende s/n, 36310 Vigo, SPAIN

Abstract

The Stirling engine was developed in 1816 but this heat engine still continues to be investigated due to the variety of energy sources that can be used to power it (e.g., solar energy, fossil fuels, biomass, and geothermal energy). To study the performance of these systems, it is necessary to develop their mathematical models and simulate their work under different operating conditions. In this paper, we use a one-dimensional dynamic model of a Stirling engine based micro-CHP system. The model is, principally, based on a lumped mass and a heat exchanger and it was calibrated using GenOpt. The transient model can be used to simulate the machine both under steady-state operation and during a transient response. The simulations of the micro CHP system are carried out using a specific methodology. They were conducted in the Trnsys simulation environment for different European locations comparing steady state and transient behaviour in a mobile home: a recreational sailing boat. The micro-CHP system is a unique source of heat for the mobile home, while the produced electricity is stored in batteries and used whenever it is needed. A domestic hot water (DHW) tank, a heating installation and a bank of batteries are included in the simulations. Such systems demand energy from the cogeneration system. The study was performed for the whole year in different European locations. The different heating demand profiles for different cities induce variation in the electricity production. As a result, a comparison of the expected power generation in two different European locations is presented. Results for steady state and transient behaviour are also compared, from heating loads to electricity produced. The conclusions of this work are based on the annual system performance.

*Corresponding author, e-mail address: [email protected] , tel.: 986 804 917

A Meeting between Robert Stirling and Sadi Carnot in 1824

Israel Urieli a * a Associate Professor Emeritus Mechanical Engineering, Ohio University

Abstract

This meeting never occurred, however the timing is feasible. In 1824 Carnot published his famous theoretical treatise “Réflexions sur la Puissance Motrice du Feu” (Reflections on the Motive Power of Fire). This was 8 years after Stirling had published his famous patent on the Stirling engine. Consider the possibility that Stirling was intrigued with Carnot’s treatise and invited him to Glasgow, Scotland, mainly in order to obtain a theoretical validation of the importance of the regenerator in the Stirling engine, which no one seemed to understand. I believe that had this meeting occurred it could have resulted in a significant difference both in the future of Stirling engine development and acceptance, and in the teaching of thermodynamics. Consider for example the famous Schmidt analysis done in 1871, 55 years after Stirling’s patent. There is no mention of a regenerator in the analysis, and apparently the Lehman machine on which it was based did not have a regenerator. Furthermore, in all the thermodynamics textbooks that I am aware of, the main example of an ideal heat engine described is the so-called “Carnot” engine, which is a totally impractical machine, even though the ideal Stirling engine with a perfect regenerator has the identical ideal thermal efficiency.

*Corresponding author

Tools for a Real Stirling Engine Cycle Thermodynamic Analysis

Jiri VAVRA a *, Libor CERVENKA a and Michal TAKATS a a Czech Technical University, Faculty of Mechanical Engineering, Vehicle Center of Sustainable Mobility, 166 07, Prague, Czech Republic

Abstract

The paper presents a combined experimental and modelling approach to a real alpha-Stirling engine performance and thermodynamic investigations. The main objective of the experimental part was an acquisition of fast changing pressures in working spaces of the engine. The experiments were performed at the Stirling engine prototype at the test laboratory of the engine manufacturer. The instantaneous pressure traces in a compression and expansion cylinder and the pressure traces in a buffer space were recorded and post-processed using the purposely (in-house) developed software. An angular position of a crankshaft and the compression piston distance from the cylinder head were sensed simultaneously with the pressure data allowing a correct evaluation of a mean indicated pressure and derived quantities. The experimental results have been used as a calibration data for a mathematical model of the tested engine. The second, modelling part of the paper describes a development and validation of a 1-D differential model of the tested Stirling engine prototype. The model was built in a commercial thermodynamic simulation software package GT Suite. The sub-models of heat exchangers and a regenerator have been built and tuned separately by the experimental data provided by the engine manufacturer. The system model is currently being used for design optimizations, sensitivity analyses and engine performance predictions. As a demonstration a comparison of engine performance for helium and hydrogen used as a working gas at various engine speeds is presented.

*Corresponding author, e-mail address: [email protected] , tel.: +420 246 003 706

Dynamic balance design technology for a V-type Stirling engine

Wang Lintao a *, Jin Yongxing a, Liang Pengfei a, Liu Jiawei a, Zeng Jia a, Guo Xiaoning a a Shanghai Stirling Engine Engineering Technology Research Center, Shanghai 201203, PR China

Abstract

In this paper, a dynamic balance mechanism for V-type Stirling engine was presented, and theoretical balance research for the balance design technology was given. It proved that the dynamic balance design method was reasonably practicable.

*Corresponding author, e-mail address: [email protected]

Development of a 500-W Beta-Type Stirling Engine by a Modified Non- Ideal Adiabatic Model

Hang-Suin YANG a * and Chin-Hsiang CHENG b a Institute of Aeronautics and Astronautics, National Cheng Kung University, No.1, Ta-Shieh Road, Tainan, Taiwan 70101, R.O.C. b Institute of Aeronautics and Astronautics, National Cheng Kung University, No.1, Ta-Shieh Road, Tainan, Taiwan 70101, R.O.C.

Abstract

The present study is aimed at developing a 500-W beta-type Stirling engine with a rhombic drive mechanism. A prototype engine and a theoretical model are established simultaneously to perform a thorough study of the performance of the engine. A modified non-ideal adiabatic model is built to predict transient variation of thermal physical quantities in each working space, such as pressure, temperature, mass, mass flow rate, heat transfer rate of working fluid as well as the temperature in regenerator matrix. Eventually, indicated power and thermal efficiency of the engine can be further determined. An empirical formula of the mechanical loss of the engine due to friction is also presented based on the experimental data. As 8-atm helium is charged into the cylinder and a No. 50 wire mesh is used in the regenerator, the maximum shaft power of the engine can reach 556 W at 800 ℃ heating temperature. It is found that the simulation results are rather close to the experimental data.

*Corresponding author, e-mail address: [email protected] , tel.: 886-6-2757575 (ext. 63627)

Optimum design of piston rod used in Wobble Member Transmission Mechanism

Jianming ZHOU a, b *, Weiming PAN b, Sheng ZHOU c and Yongxing JIN c a Shanghai Jiao Tong University, Shanghai 200240, PR China b Shanghai Marine Diesel Engine Research Institute, Shanghai 201203, PR China c Shanghai Stirling Engine Engineering Technology Research Center, Shanghai 201203, PR China

Abstract

The purpose of this study is to optimize the design of piston rod which is used in Wobble Member Transmission Mechanism for small-scale Stirling Engine. At first, the trajectory of the lower endpoint of piston rod is obtained through kinematic analysis, and the force loaded on the top endpoint of the piston rod is calculated through dynamic analysis. With the result of kinematic and dynamic analysis, the stress distributions of piston rod in different load cases are simulated through static analysis. Furthermore, the fatigue life and the buckling load of piston rod are obtained by fatigue analysis and buckling analysis. Through a comprehensive consideration of the results above, the optimum piston rod parameters for Wobble Member Transmission Mechanism is obtained.

*Corresponding author, e-mail address: [email protected] , tel: +8621 61693567

Posters

Design of an onboard auxiliary power and desalination unit powered by a Stirling engine

L. Cioccolanti * a, A. Savoretti a, G. Comodi a, F. Caresana a, C.M. Bartolini a a DIISM: Dipartimento di Ingegneria Industriale e Scienze Matematiche, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona, Italy

*Corresponding author, e-mail address: [email protected]

Novel Auxuliary Power Unit Concept for Heavy Trucks

Barry Flannery * a, Robert Lattin b, Harald Berresheim c, Rory F. D. Monaghan a a Department of Mechanical Engineering, National University of Ireland, Galway b Department of Physics, National University of Ireland, Galway c Bloomington, Minnesota, Minneapolis, United States

*Corresponding author, e-mail address: [email protected]

Metallic materials for high temperature operation in Stirling engines

S. Sainz * a, F. Castro a, M. Cordón b, M. Eskubi b and A. Etxeberria b a CEIT, P Manuel Lardizábal 15, 20018, San Sebastian, Spain b CS Centro Stirling S. Coop., Avda. Álava 3, 20550, Aretxabaleta, Spain

*Corresponding author, e-mail address: [email protected]

STIRLING machine design with supplementary regenerators

Thierry RABALLAND * a a 28 rue Maurice BERTEAUX 33400 TALENCE, FRANCE

*Corresponding author, e-mail address: [email protected]

Experimental apparatus to test supplementary regenerators in STIRLING machines

Thierry RABALLAND * a a 28 rue Maurice BERTEAUX 33400 TALENCE, FRANCE

*Corresponding author, e-mail address: [email protected]

Distribution mechanism design methodology for Ericsson machines

Eugenio Sangüesa Subiron * a, Jaime Gros Bañeres b , Javier Aranceta Aguirre c a Centro Stirling, S. Coop., 20550, Atretxabaleta, Guipuzcoa, España b CIRCE, Calle Mariano Esquilor Gomez, (Edif. Circe Campus Rio Ebro) 15, 50015,Zaragoza c Mondragón Componentes MCC, S. Coop., 20550, Aretxabaleta, Guipuzcoa, España

* Corresponding author, e-mail address: esanguesaentrostirling.com

Design and building of a Stirling engine for microgeneration as a learning experience for future Industrial Engineers

A. Gonzalez * a, A. Gomendio a, J. Gros, K. Odriozola a a Mondragon Unibertsitatea Loramendi, 4. Apartado 23 20500 Arrasate - Mondragón

* Corresponding author, e-mail address: [email protected]