DOCSLIB.ORG

Imece2014‑36413

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Imece2014‑36413 Proceedings of the ASME 2014 International Mechanical Engineering Congress and Exposition IMECE2014 November 14-20, 2014, Montreal, Quebec, Canada IMECE2014-36413 A STUDY OF THE SCAVENGING PROCESS IN A TWO-STROKE FREE PISTON LINEAR ENGINE USING CFD SIMULATION Nguyen Ba Hung Ocktaeck Lim Graduate school of Mechanical and Automotive Department of Mechanical and Automotive Engineering, University of Ulsan Engineering, University of Ulsan Ulsan, South Korea Ulsan, South Korea ABSTRACT [1,2]. The variation of compression ratio in the FPLE also It is widely known that scavenging process is of allows the engine to operate with various kinds of fuels and importance in the performance and thermal efficiency of two- homogeneous charge compression ignition (HCCI) [3,4]. For stroke engines. Unlike the conventional two-stroke engine, a the conventional two-stroke engines, the power output is two-stroke free piston linear engine can change compression dependent on the mass of air and fuel trapped inside the ratio due to free motion of a piston in a cylinder. The free combustion chamber prior to combustion. The trapped contents motion of the piston directly affects the gas exchange process are effected by the gas exchange process as well as scavenging or scavenging process of the free piston engine. In this study, a process. Further, in the combustion chamber of a two-stroke numerical simulation using computational fluid dynamics engine, a large amount of unburned HC emissions and residual (CFD) is conducted to examine the scavenging process taking gas can be produced if the scavenging process is inefficient [5]. place in a two-stroke free piston linear engine. The motion of It can be seen that the scavenging process in two-stroke the free piston is built first based on a dynamic model to define engines plays an important role for improving the power the motion profiles of the piston, and afterwards the piston’s output and the residual exhaust gas. Although two-stroke free motion profiles are imported into a commercial CFD software piston engines have no a crankshaft, the scavenging process in (Ansys Fluent v.14) to simulate the scavenging process. To the free piston engine is similar to conventional two-stroke provide information for this study, some key parameters such engines. For the two-stroke free piston engines, the scavenging as operating frequency of the piston, effective stroke length process is considered to be key to realizing the combustion and inlet pressure are changed to find out their effects on the efficiency and emissions potential of the engine [6]. Due to trapping efficiency. The simulation results show that the difficulties associated with the measurement techniques, CFD trapping efficiency has a maximum value of 83% at optimal (Computational Fluid Dynamics) is a very useful tool to operating frequency f=33Hz. Besides, by increasing effective analyze the scavenging process. Goldsborough and Blarigan stroke length and reducing inlet pressure, the trapping [6] presented a study for optimizing the scavenging system of a efficiency is increased two-stroke free piston engine using KIVA-3V code. Zhu et al. [7] presented a numerical simulation of gas exchange process in a two-stroke free piston engine using 3D CFD method. Yu et INTRODUCTION al. [8] used a commercial CFD software AVL FIRE to simulate the gas flow of a hydraulic free piston engine during the A two-stroke free piston linear engine (2S-FPLE) is scavenging process. considered to be a crankless internal combustion engine with In this paper, the scavenging process is numerically studied free motion of a piston in a cylinder. Unlike conventional using a commercial CFD software Ansys Fluent v.14. This engines with a crankshaft mechanism, the FPLE can optimize study is conducted on a two-stroke free piston linear engine the combustion process through variable compression ratios using loop scavenging type. The dimensional parameters are 1 Copyright © 2014 by ASME chosen based on a real FPLE. In order to simulate the connecting rod to move back and forth. This stage is called the scavenging process in the FPLE, this study is organized as firing mode. The movement of the connecting rod will follows. At first, the motion of the free piston is built based on generate current in the wires due to the changing magnetic a dynamic model to calculate the piston’s motion profiles. flux linked with the wire in the stator. Then, the piston’s motion profiles are used as input variables for CFD model to simulate the scavenging process. The motion SIMULATION SETUP profiles of the piston are adjusted depending on the operating Dynamic model frequency and piston stroke. In this study the key parameters Due to the fact that the piston motion profile of the FPLE is such as operating frequency, effective stroke length and inlet different from conventional engines, a dynamic model is pressure are changed to find out their effects on the trapping established to describe the piston motion. Fig. 2 shows a free efficiency, which relates directly to the output power of the body diagram in motoring mode. The motion of the piston engine. obeys Newton’s second law, and the piston acceleration is determined by: OPERATION OF THE FPLE The FPLE is a combination of two main components including 2 xd mFFFAPAPF (1) a free piston engine and a linear alternator, as shown in fig. 1. srslfrlm dt 2 Reed where, F is a motoring force provided by the linear alternator Valve Spring Coil Permanent m magnet (N), Pl, Pr is the pressure to the left and right of the cylinder Charge 2 (Pa), respectively, A is the area of the piston crown (m ), Ff is Flow SN friction force (N), m is reciprocating mass (kg), x is the 2 2 Intake port displacement of piston (m), d x/dt is the acceleration of piston Free piston (m/s2), while F and , F are respectively, the spring force to engine sl sr the left and right (N). These spring forces are calculated by: sl . xkF l (2) Spark plug sr . xkF r (3) Exhaust port N S where, k is the spring stiffness, Δxl and, Δxr are, respectively, the deformation of the left and right spring. Compressor Linear Alternator Fig. 1: The operating model of FPLE. Fsl Fsr Fm The free piston engine consists of a dual piston connected by a N S rod system. Spark plugs are arranged at each cylinder head to ignite the air/fuel mixture at the end of the compression Ff process. In order to increase intake pressure, the engine is designed with two compressors on each side of the engine, as shown in fig. 1. Each compressor also includes a dual piston, Pl A Pr A which is connected by a connecting rod system. A spring is arranged at each cylinder of the compressor as a damping device. In order to provide an intake mixture to the cylinder of the FPLE, a reed valve is arranged at each cylinder head of the N S compressor. The second component is the linear alternator with a permanent magnet mounted on the connecting rod as the translator. In the stator of the linear alternator, copper wires are wrapped around the back iron made of silicon steel. To start the engine, the linear alternator will operate to 0 x drive the free piston engine through connecting rod system. Fig. 2: Free body diagram of FPLE. This stage is called the motoring mode. After certain frequencies, spark plugs are activated, and the combustion The velocity and displacement of piston are calculated by process will occur alternatively at each cylinder, forcing the equations: 2 Copyright © 2014 by ASME dx dx 2 xd t 2 (4) dt dt 0 dt 2 xd t 2 Le dx dt 2 xx t (5) 0 dt 2 where x0 is the initial position of piston, which is the middle position (x0=0) of maximum stroke xm, as shown in fig. 3. 0 x -x 0 +x -x 0 +x m m m m Fig. 4: Geometry of the FPLE. Fig. 3: The engine model with the piston at the mid position. Parameters Values The dynamic model is calculated continuously by a program Bore (mm) 30 written in Fortran. However, the obtained result is only a time Effective stroke length L (mm) 18, 19, 20, 21 notation since the free piston engine does not have a e crankshaft. To get a crank angle notation, it is necessary to Width of exhaust port (mm) 20 convert from time to equivalent crank angle (ECA). Here, the Height of exhaust port (mm) 15 equivalent crank angle is defined by [6]: ECA=(t-t0).f.360, in Width of intake port (mm) 15 which t is time, f is operating frequency of the piston, t0 is Height of intake port (mm) 13 initial time. Reciprocating mass m (kg) 0.8 Compression ratio Variable CFD model Inlet pressure Pin (bar) 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 The motion curves obtained from the dynamic model will be Inlet temperature T (K) 293 provided as an input for computational fluid dynamic (CFD) in model to calculate the trapping efficiency. In two-stroke free Tab. 1: Engine specifications and operating conditions piston engines, the trapping efficiency is defined as follows [6]: The geometry of the FPLE is imported into a commercial CFD Trapping efficiency: the ratio of the trapped fresh charge to the software Ansys Fluent v.14 to define the calculating surfaces total delivered fresh charge. and volumes as well as to generate mesh. After generating The trapping efficiency is calculated by a program written in mesh in the Ansys software, a picture of the engine mesh is Microsoft Visual C++ before importing into the Ansys shown in fig.
Load more

Recommended publications
  • Modernizing the Opposed-Piston, Two-Stroke Engine For
    Modernizing the Opposed-Piston, Two-Stroke Engine 2013-26-0114 for Clean, Efficient Transportation Published on 9th -12 th January 2013, SIAT, India Dr. Gerhard Regner, Laurence Fromm, David Johnson, John Kosz ewnik, Eric Dion, Fabien Redon Achates Power, Inc. Copyright © 2013 SAE International and Copyright@ 2013 SIAT, India ABSTRACT Opposed-piston (OP) engines were once widely used in Over the last eight years, Achates Power has perfected the OP ground and aviation applications and continue to be used engine architecture, demonstrating substantial breakthroughs today on ships. Offering both fuel efficiency and cost benefits in combustion and thermal efficiency after more than 3,300 over conventional, four-stroke engines, the OP architecture hours of dynamometer testing. While these breakthroughs also features size and weight advantages. Despite these will initially benefit the commercial and passenger vehicle advantages, however, historical OP engines have struggled markets—the focus of the company’s current development with emissions and oil consumption. Using modern efforts—the Achates Power OP engine is also a good fit for technology, science and engineering, Achates Power has other applications due to its high thermal efficiency, high overcome these challenges. The result: an opposed-piston, specific power and low heat rejection. two-stroke diesel engine design that provides a step-function improvement in brake thermal efficiency compared to conventional engines while meeting the most stringent, DESIGN ATTRIBUTES mandated emissions
    [Show full text]
  • 2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke
    inventions Article 2-Stroke Scavenging in Conventional and Minimally-Modified 4-Stroke Engines for Heavy Duty Applications at Low to Medium Speeds Dirk Rueter Institute of Measurement and Sensor Technology, University of Applied Sciences Ruhr-West, D-45479 Muelheim an der Ruhr, Germany; [email protected] Received: 14 June 2019; Accepted: 7 August 2019; Published: 9 August 2019 Abstract: The transformation of a standard 4-stroke cylinder head into a torque-improved and gradually more efficient 2-stroke design is discussed. The concept with an effective loop scavenging via an extended inlet valve holds promise for engines at low- to medium-rotational speeds for typical designs of conventional 4-stroke cylinder heads. Calculations, flow simulations, and visualizations of experimental flows in relevant geometries and time scales indicate feasibility, followed by a small engine demonstration. Based on presumably long-forgotten and outdated patents, and the central topic of this contribution, an additional jockey rides on the inlet valve’s disk (facing away from the combustion chamber) and reshapes the in-cylinder flow into a reverted tumble. A quick gas exchange with a well-suppressed shortcut into the open exhaust is approached. For overall mechanical efficiency, the required charge pressure for scavenging is of paramount importance due to the short scavenging time and the intake’s reduced cross-section. Herein, still acceptable charging pressures are reported for scavenging periods equivalent to low or medium rotational speeds, as characteristic for heavy-duty applications. Using widely available components (charger, direct injection, variable camshaft angles) an increased engine efficiency is suggested due to the 2-stroke’s downsizing effect (relatively less internal friction as well as the promise of more torque and a decreased size).
    [Show full text]
  • Jennings: Two-Stroke Tuner's Handbook
    Two-Stroke TUNER’S HANDBOOK By Gordon Jennings Illustrations by the author Copyright © 1973 by Gordon Jennings Compiled for reprint © 2007 by Ken i PREFACE Many years have passed since Gordon Jennings first published this manual. Its 2007 and although there have been huge technological changes the basics are still the basics. There is a huge interest in vintage snowmobiles and their “simple” two stroke power plants of yesteryear. There is a wealth of knowledge contained in this manual. Let’s journey back to 1973 and read the book that was the two stroke bible of that era. Decades have passed since I hung around with John and Jim. John and I worked for the same corporation and I found a 500 triple Kawasaki for him at a reasonable price. He converted it into a drag bike, modified the engine completely and added mikuni carbs and tuned pipes. John borrowed Jim’s copy of the ‘Two Stoke Tuner’s Handbook” and used it and tips from “Fast by Gast” to create one fast bike. John kept his 500 until he retired and moved to the coast in 2005. The whereabouts of Wild Jim, his 750 Kawasaki drag bike and the only copy of ‘Two Stoke Tuner’s Handbook” that I have ever seen is a complete mystery. I recently acquired a 1980 Polaris TXL and am digging into the inner workings of the engine. I wanted a copy of this manual but wasn’t willing to wait for a copy to show up on EBay. Happily, a search of the internet finally hit on a Word version of the manual.
    [Show full text]
  • Modeling Scavenging for a Hydraulic Free-Piston Engine
    Macalester Journal of Physics and Astronomy Volume 8 Issue 1 Spring 2020 Article 6 May 2020 Modeling Scavenging for a Hydraulic Free-Piston Engine Nathan Davies Macalester College, [email protected] Follow this and additional works at: https://digitalcommons.macalester.edu/mjpa Part of the Astrophysics and Astronomy Commons, and the Physics Commons Recommended Citation Davies, Nathan (2020) "Modeling Scavenging for a Hydraulic Free-Piston Engine," Macalester Journal of Physics and Astronomy: Vol. 8 : Iss. 1 , Article 6. Available at: https://digitalcommons.macalester.edu/mjpa/vol8/iss1/6 This Capstone is brought to you for free and open access by the Physics and Astronomy Department at DigitalCommons@Macalester College. It has been accepted for inclusion in Macalester Journal of Physics and Astronomy by an authorized editor of DigitalCommons@Macalester College. For more information, please contact [email protected]. Modeling Scavenging for a Hydraulic Free-Piston Engine Abstract The hydraulic free-piston engine at the University of Minnesota offers a solution to improve the hydraulic efficiency andeduce r emission output of off-road vehicles. We developed a MATLAB Simulink model to track the pressure, temperature, and mass profile of the fuel within the cylinder during operation. By varying different initial conditions of our model, we found that a higher intake manifold pressure and larger bottom dead center location results in higher scavenging efficiency. These results can be used to improve the controller of this engine and better maintain stable operation. Keywords Scavenging Hydraulic Free-Piston Engine Cover Page Footnote I would like to thank the Center for Compact and Efficient Fluidower P at the University of Minnesota for providing me with this research experience.
    [Show full text]
  • Analysis of the Scavenging Process of a Two-Stroke Free-Piston Engine Based on the Selection of Scavenging Ports Or Valves
    energies Article Analysis of the Scavenging Process of a Two-Stroke Free-Piston Engine Based on the Selection of Scavenging Ports or Valves Boru Jia 1,2,* ID , Yaodong Wang 1, Andrew Smallbone 1 and Anthony Paul Roskilly 1 1 Sir Joseph Swan Centre for Energy Research, Newcastle University, Newcastle upon Tyne NE1 7RU, UK; [email protected] (Y.W.); [email protected] (A.S.); [email protected] (A.P.R.) 2 School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, China * Correspondence: [email protected] or [email protected]; Tel.: +44-07547839154 Received: 1 December 2017; Accepted: 24 January 2018; Published: 2 February 2018 Abstract: The free-piston engine generator (FPEG) is a linear energy conversion device with the objective of utilisation within a hybrid-electric automotive vehicle power system. In this research, the piston dynamic characteristics of an FPEG is compared with that of a conventional engine (CE) of the same size, and the difference in the valve timing is compared for both port scavenging type and valve scavenging type, with the exhaust valve closing timing is selected as the parameter. A zero-dimensional simulation model is developed in Ricardo WAVE software (2016.1), with the piston dynamics obtained from the simulation model in Matlab/SIMULINK (R2017a). For the CE and FEPG using scavenging ports, in order to improve its power output to the same level as that of a CE, the inlet gas pressure is suggested to be improved to above 1.2 bar, approximately 0.2 bar higher than that used for a CE.
    [Show full text]
  • 19FFL-0023 2-Stroke Engine Options for Automotive Use: a Fundamental Comparison of Different Potential Scavenging Arrangements for Medium-Duty Truck Applications
    Citation for published version: Turner, J, Head, RA, Chang, J, Engineer, N, Wijetunge, RS, Blundell, DW & Burke, P 2019, '2-Stroke Engine Options for Automotive Use: A Fundamental Comparison of Different Potential Scavenging Arrangements for Medium-Duty Truck Applications', SAE Technical Paper Series, pp. 1-21. https://doi.org/10.4271/2019-01-0071 DOI: 10.4271/2019-01-0071 Publication date: 2019 Document Version Peer reviewed version Link to publication The final publication is available at SAE Mobilus via https://doi.org/10.4271/2019-01-0071 University of Bath Alternative formats If you require this document in an alternative format, please contact: [email protected] General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Download date: 27. Sep. 2021 Paper Offer 19FFL-0023 2-Stroke Engine Options for Automotive Use: A Fundamental Comparison of Different Potential Scavenging Arrangements for Medium-Duty Truck Applications Author, co-author (Do NOT enter this information. It will be pulled from participant tab in MyTechZone) Affiliation (Do NOT enter this information. It will be pulled from participant tab in MyTechZone) Abstract For the opposed-piston engine, once the port timing obtained by the optimizer had been established, a supplementary study was conducted looking at the effect of relative phasing of the crankshafts The work presented here seeks to compare different means of on performance and economy.
    [Show full text]
  • Basic 2 Stroke Tuning
    Basic 2 stroke Tuning Changing the power band of your dirt bike engine is simple when you know the basics. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. The most common mistake is to choose the wrong combination of engine components, making the engine run worse than stock. Use this as a guide to inform yourself on how changes in engine components can alter the powerband of bike's engine. Use the guide at the end of the chapter to map out your strategy for changing engine components to create the perfect power band. TWO-STROKE PRINCIPLES Although a two-stroke engine has less moving parts than a four-stroke engine, a two- stroke is a complex engine because it relies on gas dynamics. There are different phases taking place in the crankcase and in the cylinder bore at the same time. That is how a two- stroke engine completes a power cycle in only 360 degrees of crankshaft rotation compared to a four-stroke engine which requires 720 degrees of crankshaft rotation to complete one power cycle. These four drawings give an explanation of how a two-stroke engine works. 1) Starting with the piston at top dead center (TDC 0 degrees) ignition has occurred and the gasses in the combustion chamber are expanding and pushing down the piston. This pressurizes the crankcase causing the reed valve to close. At about 90 degrees after TDC the exhaust port opens ending the power stroke. A pressure wave of hot expanding gasses flows down the exhaust pipe.
    [Show full text]
  • A Three-Zone Scavenging Model for Large Two-Stroke Uniflow Marine
    energies Article A Three-Zone Scavenging Model for Large Two-Stroke Uniflow Marine Engines Using Results from CFD Scavenging Simulations Michael I. Foteinos 1,* , Alexandros Papazoglou 1, Nikolaos P. Kyrtatos 1, Anastassios Stamatelos 2,* , Olympia Zogou 2 and Antiopi-Malvina Stamatellou 2 1 Laboratory of Marine Engineering, National Technical University of Athens, GR-15780 Athens, Greece; [email protected] (A.P.); [email protected] (N.P.K.) 2 Laboratory of Thermodynamics & Thermal Engines, University of Thessaly, GR-38334 Volos, Greece; [email protected] (O.Z.); [email protected] (A.-M.S.) * Correspondence: [email protected] (M.I.F.); [email protected] (A.S.) Received: 17 April 2019; Accepted: 4 May 2019; Published: 7 May 2019 Abstract: The introduction of modern aftertreatment systems in marine diesel engines call for accurate prediction of exhaust gas temperature, since it significantly affects the performance of the aftertreatment system. The scavenging process establishes the initial conditions for combustion, directly affecting exhaust gas temperature, fuel economy, and emissions. In this paper, a semi-empirical zero-dimensional three zone scavenging model applicable to two-stroke uniflow scavenged diesel engines is updated using the results of CFD (computational fluid dynamics) simulations. In this 0-D model, the engine cylinders are divided in three zones (thermodynamic control volumes) namely, the pure air zone, mixing zone, and pure exhaust gas zone. The entrainment of air and exhaust gas in the mixing zone is specified by time varying mixing coefficients. The mixing coefficients were updated using results from CFD simulations based on the geometry of a modern 50 cm bore large two-stroke marine diesel engine.
    [Show full text]
  • Effects and Advantages of Gasoline Direct Injection System Vishwanath M*, S
    Journal of Chemical and Pharmaceutical SciencesISSN: 0974-2115 Effects and Advantages of Gasoline Direct Injection System Vishwanath M*, S. Madhu Department of Automobile Engineering, Saveetha School of Engineering, Chennai-602 105 *Corresponding author: E-Mail: [email protected] ABSTRACT Gasoline direct injection process is a form of gas give procedure used in current developments of vehicle. The gasoline financial system and the stringent exhaust emission norms has led to the transmission in the gasoline process from carburetor direct injection method. Probably the most predominant international initiative of the automobile industry is to improve an immediate-injection fuel engine. Four technical aspects that make up the groundwork applied sciences in direct injection methods. a) Air waft into the cylinder is improved. b) The form of the piston with curved high controls the combustion by way of mixing the air-gasoline combination. c) The stress of gas injection is accelerated by the excessive strain gas Pump. d) The vaporization and dispersion of the gas spray is managed by means of the excessive stress swirl injector Gasoline financial system will also be acquired by using adjusting air fuel ratio situated on the performing load. It presents a right estimation of the nice of gasoline required at right time and supplies manipulate over combustion. Gasoline in this paper advantages and effects of fuel direct injection procedure is reviewed. KEY WORDS: Gasoline direct injection (GDI), High Pressure Fuel Pump, Carburetor. 1. INTRODUCTION The fundamental goals of the automotive enterprise is to acquire a excessive energy, low precise fuel consumption, low emissions, low noise and higher drive relief cars.
    [Show full text]
  • A Numerical Investigation of a Two-Stroke Poppet-Valved Diesel Engine Concept
    A NUMERICAL INVESTIGATION OF A TWO-STROKE POPPET-VALVED DIESEL ENGINE CONCEPT Philip Robert Teakle BE MEngSc Tribology and Materials Technology Group Mechanical, Manufacturing and Medical Engineering Queensland University of Technology Submitted for the degree of Doctor of Philosophy 2004 v Keywords Two-stroke, poppet valves, KIVA, thermodynamic modelling, zero-dimensional modelling, multidimensional modelling, engine modelling, scavenging models, scavenging simulations. Executive Summary Two-stroke poppet-valved engines may combine the high power density of two - stroke engines and the low emissions of poppet-valved engines. A two-stroke diesel engine can generate the same power as a four-stroke engine of the same size, but at higher (leaner) air/fuel ratios. Diesel combustion at high air/fuel ratios generally means hydrocarbons, soot and carbon monoxide are oxidised more completely to water and carbon dioxide in the cylinder, and the opportunity to increase the rate of exhaust gas recirculation should reduce the formation of nitrogen oxides (NOx). The concept is being explored as a means of economically modifying diesel engines to make them cleaner and/or more powerful. This study details the application of two computational models to this problem. The first model is a relatively simple thermodynamic model created by the author capable of rapidly estimating the behaviour of entire engine systems. It was used to estimate near-optimum engine system parameters at single engine operating points and over a six-mode engine cycle. The second model is a detailed CFD model called KIVA- ERC. It is a hybrid of the KIVA engine modelling package developed at the Los Alamos National Laboratory and combustion and emissions subroutines developed at the University of Wisconsin-Madison Engine Research Center.
    [Show full text]
  • Multiobjective Optimization of the Breathing System of an Aircraft Two Stroke Supercharged Diesel Engine
    Available online at www.sciencedirect.com ScienceDirect Energy Procedia 82 ( 2015 ) 31 – 37 ATI 2015 - 70th Conference of the ATI Engineering Association Multiobjective optimization of the breathing system of an aircraft two stroke supercharged Diesel engine Antonio Paolo Carluccia,*, Antonio Ficarellaa, Domenico Laforgiaa, Gianluca a Trullo aDepartment of Engineering for Innovation, University of Salento, Via per Monteroni, Lecce 73100, Italy Abstract One of the factors limiting the utilization of piston internal combustion engines for aircraft propulsion is the performance decrease increasing the altitude of operation. This is due to the negative effect of air density reduction increasing the altitude on cylinder filling. A solution to this problem is represented by the engine supercharging. Unfortunately, in two stroke engines, the cylinder filling efficiency is antithetical to the cylinder scavenging efficiency. With the aim of guaranteeing an optimal balance between engine performance and specific consumption, an engine breathing system optimization is needed. In this work, the results obtained running a multi-objective optimization procedure aiming at performance increase and fuel consumption reduction of an aircraft two stroke supercharged diesel engine at various altitudes are analyzed. During the optimization procedure, several geometric parameters of the intake and exhaust systems as well as geometric and operating engine parameters have been varied. Then, a multi-objective optimization algorithm based on genetic algorithms has been run to obtain the configurations optimizing the engine performance at Sea Level (take-off conditions) and fuel consumption at 10680 m (cruise conditions). © 20152015 The The Authors. Authors. Published Published by Elsevier by Elsevier Ltd. This Ltd. is an open access article under the CC BY-NC-ND license (Selectionhttp://creativecommons.org/licenses/by-nc-nd/4.0/ and/or peer-review under responsibility).
    [Show full text]
  • Scavenging Ports' Optimal Design of a Two-Stroke Small Aeroengine Based on the Benson/Bradham Model
    energies Article Scavenging Ports’ Optimal Design of a Two-Stroke Small Aeroengine Based on the Benson/Bradham Model Yuan Qiao, Xucheng Duan, Kaisheng Huang * , Yizhou Song and Jianan Qian State Key Laboratory of Automotive Safety and Energy, Department of Automotive Engineering, Tsinghua University, Beijing 100084, China; [email protected] (Y.Q.); [email protected] (X.D.); [email protected] (Y.S.); [email protected] (J.Q.) * Correspondence: [email protected]; Tel.: +86-138-0123-7852 Received: 27 September 2018; Accepted: 11 October 2018; Published: 12 October 2018 Abstract: The two-stroke engine is a common power source for small and medium-sized unmanned aerial vehicles (UAV), which has wide civil and military applications. To improve the engine performance, we chose a prototype two-stroke small areoengine, and optimized the geometric parameters of the scavenging ports by performing one-dimensional (1D) and three-dimensional (3D) computational fluid dynamics (CFD) coupling simulations. The prototype engine is tested on a dynamometer to measure in-cylinder pressure curves, as a reference for subsequent simulations. A GT Power simulation model is established and validated against experimental data to provide initial conditions and boundary conditions for the subsequent AVL FIRE simulations. Four parameters are considered as optimal design factors in this research: Tilt angle of the central scavenging port, tilt angle of lateral scavenging ports, slip angle of lateral scavenging ports, and width ratio of the central scavenging port. An evaluation objective function based on the Benson/Bradham model is selected as the optimization goal. Two different operating conditions, including the take-off and cruise of the UAV are considered.
    [Show full text]