Design analysis methods for Stirling engines

Journal of Energy in Southern Africa • Vol 19 No 3 • August 2008 Abstract Worldwide attempts are being made to increase the use of our renewable energy sources as well as to use our current fossil fuel energy sources more efficiently. Waste heat recovery forms a substantial part of the latter and is the focus of this project. Stirling technology finds application in both the renewable energy sector and in waste heat recovery. Investigating the applicability of Stirling engines in the above-mentioned fields is relevant to develop more efficient external combustion units as well as to utilize our renewable energy sources. Developing a design analysis and synthesis tool capable of optimizing Stirling powered units forms the main objective of this project. The methodology followed to achieve this, involved the application of three different methods of analysis, namely the method of Schmidt, the adiabatic analysis and the simple analysis based on a five volume approach. The Schmidt analysis is used to obtain the internal engine pressure which is a required input for the adiabatic analysis while the simple analysis introduces pumping losses and regenerator inefficiencies. These methodologies are discussed briefly in this paper. Experimental verification of the analytical data was carried out on a Heinrici Stirling engine and both the analytical data and the experimental data are presented here. Shortcomings of these methods of analysis are highlighted and an alternative approach to solve particular shortcomings is presented.