Study and Numerical Simulation of Unconventional Engine Technology
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STUDY AND NUMERICAL SIMULATION OF UNCONVENTIONAL ENGINE TECHNOLOGY by ANJALI SHEKHAR B.E Aeronautical Engineering VTU, Karnataka, 2013 A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, Aerospace Engineering, College of Engineering and Applied Science, University of Cincinnati, Ohio 2018 Thesis Committee: Chair: Ephraim Gutmark, Ph.D. Member: Shaaban Abdallah, Ph.D. Member: Mark Turner, Sc.D. An Abstract of Study and Numerical Simulation of Unconventional Engine Technology by Anjali Shekhar Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Master of Science Degree in Aerospace Engineering University of Cincinnati December 2018 The aim of this thesis is to understand the working of two unconventional aircraft propul- sion systems and to setup a two-dimensional transient simulation to analyze its operational mechanism. The air traffic has nearly increased by about 40% in past three decades and calls for alternative propulsion techniques to replace or support the current traditional propulsion methodology. In the light of current demand, the thesis draws motivation from renewed inter- est in two non-conventional propulsion techniques designed in the past and had not been given due importance due to various flaws/drawbacks associated. The thesis emphasizes on the work- ing of Von Ohains thermal compression engine and pulsejet combustors. Computational Fluid Dynamics is used in current study as it offers very high flexibility and can be modified easily to incorporate the required changes. Thermal Compression engine is a design suggested by Von Ohain in 1948. The engine works on the principle of pressure rise caused inside the engine which completely depends on the temperature of working fluid and independent of rotations per minute. The design data has been provided for turbo-prop and turbo-jet engines, in the current study the design data for turbo-prop engine is used and geometric optimization study is conducted to obtain the required dimensions to setup a two-dimensional engine unit. The suggested RPM value is used to calculate the time required to complete the process. The sim- ulation is conducted and the results of simulation are verified using the basic thermodynamic equations. The vital parameters of the engine such as the thermal efficiency, energy output and thrust are calculated. A brief analysis of the performance is conducted to decide the applica- tion of this engine in current scenario. The similarities of the engine operation is compared to currently tested pressure gain devices. ii In the next research topic, Pulsejet combustor simulation study is set up by considering three different geometries. The dimensions of the combustion chamber are fixed, the tailpipe being short, medium and long are considered for the study. The simulation is designed to capture the pressure, temperature and the location of auto ignition. The results obtained from the simula- tion in current study are compared with the experimental results obtained from a separate study. The peak pressure, the pressure variation along then pulsejet, the location of auto ignition and the frequency of operation of each configuration is compared with experiment results and the observation is presented. The simulation is used to study the reasons for auto ignition, which is in turn used to establish a standard mechanism of operation for pulsejets. The results are also used to study the behavior of pulsejets with variation in geometry. Thesis Supervisor: Ephraim J Gutmark Title: Distinguished Professor and Ohio Eminent Scholar iii Copyright 2018, Anjali Shekhar This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. To my family and friends Acknowledgments I would like to take this opportunity to express my sincere gratitude to my professor and advisor, Dr. Ephraim Gutmark. He has provided me continuous support and motivation during my graduate studies. He is a great source of inspiration to me, his lectures on aircraft propulsion and aeroacoustics have helped me gain great insight into the world of aerospace. I am thankful to him for his time and for helping my out in each step i have taken towards my thesis. I would like to thank my committee members Dr Mark Turner and Dr Shaaban abdallah for taking time out of their busy schedules and for accepting to be part of my thesis committee. I owe special thanks to Dr. Villalva Rodrigo and my lab mates Vijay Anand, Alexander Zahn and William Stoddard for helping me start my research work and for continuous support during my tenure as graduate student at gas dynamics and propulsion laboratory at University of Cincinnati. This could not be possible without the support of my near and dear ones. I would like to thank my father Chandra Shekhar and mother Rama Devi for believing in my dreams and helping me pursue it. My extended family for being a pillar of strength. A special note of thanks to my friends back in India for their unconditional support.My colleagues and management team at Exel Composites deserve a special mention for supporting me and guiding me in the right career path. Finally, kudos to my friends and roommates at Cincinnati for putting up with me and un- conditionally supporting me through this journey. For being part of my ups and downs and making me feel at home :) Anjali Shekhar vi Contents Abstract ii Acknowledgments vi Contents vii List of Figures x List of Abbreviations xiii 1 Introduction 1 1.1 Motivation . 1 1.2 Objectives . 2 1.3 Contributions . 3 1.4 Organization of Thesis . 4 2 Aircraft Propulsion 5 2.1 Evolution of Aircraft Propulsion . 6 2.2 Development of Thermal Compression Engine . 12 2.3 Pressure Gain Combustors . 12 2.3.1 Rotating detonation Engines . 13 2.3.2 Pulse detonation Engines . 14 2.3.3 Wave Rotor Engines . 15 2.3.4 Comparison of TCE with other know processes . 16 2.4 Pulsejets . 18 2.4.1 History of pulsejets . 18 2.4.2 Working Mechanism of Pulsejets . 20 vii 2.4.3 Pulsejet behaviour . 22 2.4.4 Numerical Simulation of Pulsejets . 23 3 Construction and Working of Thermal Compression Engine 26 3.1 Construction of Thermal Compression Engine . 26 3.2 Working of Thermal Compression Engine . 28 3.3 Thermodynamic Cycle Analysis of TCE . 30 3.4 Geometric Optimization of TCE . 32 3.4.1 Cell Characteristics . 32 3.4.2 Nozzle and Diffuser Sizing . 34 3.4.3 Sector Area . 35 3.4.4 Timings . 36 4 Simulation study and performance analysis of thermal compression engine 38 4.1 Computation as an analytically approach . 38 4.2 Numerical Simulation . 39 4.2.1 Geometry . 39 4.2.2 Simulation Setup and Refinement Study . 40 4.2.3 Simulation Sequence . 41 4.2.4 Boundary Conditions and Sub-Process Simulation . 42 4.2.5 Simulation Results . 44 4.3 Performance Parameters . 50 4.4 Results and Discussion . 52 5 Design and Working of Pulsejet Combustors 55 5.1 Types of Pulsejets . 55 5.1.1 Valveless Pulsejets . 56 5.1.2 Valved Pulsejets . 58 5.1.3 Working of Pulsejet Combustor . 59 viii 6 Design, Numerical Computation and Analysis of Pulsejet Behaviour 62 6.1 Geometry . 63 6.2 Simulation Model . 64 6.3 Convergence Study . 65 6.4 Output Setup . 66 6.5 Simulation methodology . 67 6.6 Results and Discussions . 69 6.6.1 Comparison with Experimental Results . 72 6.6.2 Pulsejet behaviour as Helmholtz resonator or quarter wave tube . 80 6.6.3 Comparing with Vortex tube . 80 6.6.4 Conclusion . 81 7 Discussion and Future works 82 7.1 Thermal Compression Engine - Discussion . 82 7.2 Pulsejet Engine - Discussion . 83 8 Curricular Practical training - Report 84 8.1 Introduction . 84 8.2 Pultrusion process: . 85 8.3 Research Focus: . 86 8.3.1 Resin Bath . 86 8.3.2 Heat Transfer . 87 8.3.3 Design Capability . 88 9 Appendix 89 ix List of Figures 2-1 Bent bow propulsion . .6 2-2 Rubber Band propulsion . .6 2-3 Steam Powered Airship by Giffard . .7 2-4 Engine from wright Brother’s 1903 Airplane . .8 2-5 Curtiss Water Cooled 8-Cylinder Engine . .8 2-6 Pratt & Whitney’s Wasp Engine . .9 2-7 Conventional Subsonic Engines . 11 2-8 Conventional Supersonic Engines . 11 2-9 Rotating detonation Engine . 13 2-10 Pulse detonation Engine - working . 14 2-11 Wave Rotor . 15 2-12 The Flying Bomb V-1 . 19 2-13 Wave diagram of quarter wave tube . 22 3-1 Cell Rotor . 27 3-2 Sectional view of TCE . 27 3-3 Sector area for sub processes . 28 3-4 Four sub-processes of TCE . 29 3-5 P-V diagram for the engine process . 30 4-1 Simplified 2D Geometry Created for transient simulation using ANSYS FLUENT . 40 4-2 Boundary conditions for four sub-processes . 41 4-3 Static pressure plot - First Time-step . 44 4-4 Static temperature plot - First Time-step . 44 4-5 Static pressure plot - Nineteenth Time-step . 45 x 4-6 Static temperature plot - Nineteenth Time-step . 45 4-7 Static pressure plot - Thirty fifth Time-step . 46 4-8 Static temperature plot - Thirty fifth Time-step . 46 4-9 Static pressure plot - Forty seventh Time-step . 47 4-10 Static temperature plot - Forty seventh Time-step . ..