||Numerical predictions of thermodynamic cycle and thermal efficiency of thermal-lag Stirling engine
||Department of Aeronautics & Astronautics
This study is aimed at development of a numerical model for predicting thermodynamic cycle and thermal efficiency of thermal-lag Stirling engine. Thermal-lag Stirling engine is working through the principle of thermal-lag instability phenomenon. In thermal-lag engine, piston is the only moving part. So, the configuration of this engine is simpler when compared to other traditional Stirling engine. A computational fluid dynamics (CFD) numerical simulation method is used to predict the transient variations of pressure, temperature and working fluid mass in the individual working spaces of the engine. A parametric study of the effect of working gas pressure, heating temperature, cooling temperature, regenerator porosity and rotation speed on the performance of thermal-lag Stirling engine is carried out. Also, the numerical simulation of engine power output, torque and the thermal efficiency has been computed with the different operating speed, heating temperature, cooling temperature and the working gas pressure. The optimum engine speed at which the engine can reach the maximum power output and thermal efficiency has been determined. With the help of numerical simulation, the thermal-lag engine performance was analyzed with the different operating conditions.
TABLE OF CONTENTS
LIST OF TABLES VI
LIST OF FIGURES VII
CHAPTER - I INTRODUCTION 1
1.1 Thermal-lag Stirling engine configuration 2
1.2 Thermal-lag Stirling engine principle 3
1.3 Importance of numerical simulation of Stirling engine design 4
1.4 Literature review 5
CHAPTER - II NUMERICAL METHODS 11
2.1 Introduction to simulation software 11
2.1.1 Preprocessing 11
2.1.2 Solver 11
2.1.3 Post-processing 12
2.2 Numerical model description 12
2.3 Grid generation method 13
2.4 The governing equations 14
2.5 Fluent setup and solving method 17
2.5.1 Solver type 17
2.5.2 Turbulent model 17
2.5.3 Solution methods 20
2.5.4 Porous zone condition 20
2.5.5 Boundary conditions 22
2.6 Solution initialization method 23
2.7 Power, torque and thermal efficiency 23
2.8 Piston position equation 24
CHAPTER - III RESULTS AND DISCUSSION 25
3.1 Masses of the working fluid in individual working spaces 26
3.2 Temperature distribution in different working spaces 26
3.3 Static gauge pressure and absolute pressure distribution 27
3.4 Volume variation and piston position 28
3.5 P-V diagram 28
3.6 Heat flux in high temperature working space 29
3.7 Power output, thermal efficiency and torque 30
3.7.1 The effect of heating temperature on engine performance 30
3.8 Effect of operating pressure on engine performance 31
3.9 Effect of cooling temperature on engine performance 32
3.10 Effect of regenerator porosity on engine performance 33
CHAPTER - IV CONCLUSIONS 35
 Chen NCJ, West CD. A single-cylinder valveless heat engine. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1987.
 Tailer PL. External combustion Otto cycle thermal lag engine. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1993;1:943-947.
 Tailer PL. Thermal lag test engines evaluated and compared to equivalent Stirling engines. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1995;3:353-357.
 West CD. Some single-piston closed-cycle machines and Peter tailer's thermal lag engine. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1993;2:673-679.
 Wicks F, Caminero C. Tail PL. External combustion thermal lag piston/cylinder engine analysis and potential applications. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1994;2:951-954.
 Arques P. Theoretical and numerical study, improvement of the Wicks-Tailer cycle. Proceedings of the Intersociety Energy Conversion Engineering Conference. 1995;3:407-412.
 Carlos FAA, Michel DP, Sebastian V, Juan GB. Control volume energy based model for a thermal lag engine. International Conference on Renewable Energy, Energy Saving and Energy Education.2009;78:565-573.
 Organ, Allan J. The air engine: Stirling cycle power for a sustainable future. Elsevier, 2007.
 Hamaguchi K, Futagi H, Yazaki T, Hiratsuka Y. Measurement of work generation and improvement in performance of a pulse tube engine. Journal of Power and Energy Systems. 2008;2:1267-1275.
 Yoshida T, Yazaki T, Futaki H, Hamaguchi K, Biwa T. Work flux density measurements in a pulse tube engine. Applied Physics Letters. 2009;95: 044101.
 Moldenhauer S, Holtmann C, Stark T, Thess A. Theoretical and experimental investigations of the pulse tube engine. Journal of Thermophysics and Heat Transfer.2013;27:534-541.
 Moldenhauer S, Stark T, Holtmann C, Thess A. The pulse tube engine: A numerical and experimental approach on its design, performance, and operating conditions. Energy.2013;55:703-715.
 Moldenhauer S, Thess A, Holtmann C, Fernandez-Aballi C. Thermodynamic analysis of a pulse tube engine. Energy Conversion and Management.2013;65:810-818.
 Ki T, Jeong S. Design and analysis of highly effective pulse tube engine. Applied Thermal Engineering. 2013;53:31-36.
 Cheng CH, Yang HS. Theoretical model for predicting thermodynamic behavior of thermal-lag Stirling engine. Energy. 2013;49:218-228.
 Cheng CH, Yang HS, Jhou BY, Chen YC, Wang YJ. Dynamic simulation of thermal-lag Stirling engines. Applied Energy. 2013;108:466-476.
 Cheng CH, Yang HS. Analytical model for predicting the effect of operating speed on shaft power output of Stirling engines. Energy. 2011;36:5899-5908.
 Thombare DG, Verma SK. Technological development in the Stirling cycle engines. Renewable and Sustainable Energy Reviews. 2008;12:1-38.
 Cheng C-H, Yu Y-J. Combining dynamic and thermodynamic models for dynamic simulation of a beta-type Stirling engine with rhombic-drive mechanism. Renewable Energy. 2011;37:161-173.
 Cheng CH, Yu YJ. Dynamic simulation of a beta-type Stirling engine with cam-drive mechanism via the combination of the thermodynamic and dynamic models. Renewable Energy. 2011;36:714-725.
 Boroujerdi AA, Esmaeili M. Characterization of the frictional losses and heat transfer of oscillatory viscous flow through wire-mesh regenerators. Alexandria Engineering Journal.2015;54:787-794.
 Costa SC, Tutar M, Barreno I, Esnaola JA, Barrutia H, García D. , González MA, Prieto JI. Experimental and numerical flow investigation of Stirling engine regenerator. Energy.2014;72:800-812.
 Feldman Jr KT. Review of the literature on Sondhauss thermoacoustic phenomena. Journal of Sound and Vibration. 1968;7:71-82.
 Feldman KT, Carter RL. A study of heat driven pressure oscillations in a gas. Journal of Heat Transfer. 1970;92:536-540.