Design analysis methods for Stirling engines

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 effi-ciently. 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 opti-mizing Stirling powered units forms the main objec-tive of this project. The methodology followed to achieve this, involved the application of three differ-ent 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 intro-duces pumping losses and regenerator inefficien-cies. These methodologies are discussed briefly in this paper. Experimental verification of the analyti-cal data was carried out on a Heinrici Stirling engine and both the analytical data and the experi-mental data are presented here. Shortcomings of these methods of analysis are highlighted and an alternative approach to solve particular shortcom-ings is presented.

<p>Design, Operation, and Analysis of a Floating Water Fountain System Using Renewable Energy Technology</p>

“…Shortcomings of the Stirling cycle have hindered its wider application in competition with steam, electric, and internal combustion. These shortcomings include the complexity of design and a relatively low power output per size and weight (Beale, 1984;Der Minassians & Sanders, 2009;Karabulut, Yucesu, & Koca, 2000;Snyman et al, 2008).…”

“…Both pistons are mechanically connected to a common flywheel and crankshaft. Typically, the phase angle is 90° (Senft, 2002;Snyman et al, 2008).…”

“…A feature consisting of layers or coils of heat-absorbent material located on the internal surfaces of working fluid conduits or passageways. This feature is used to increase the efficiency of the cycle by (a) accumulating excess heat from the expanding working fluid, which can then be transferred to the fluid during subsequent cycles, and (b) reducing the amount of heat that must be accommodated by the external heat sink through the cold workspace (Snyman et al, 2008).…”

“…However, gases with lighter molecular weight (i.e., helium or hydrogen) provide thermodynamic advantages over air. The working fluid is not consumed in the cycle (Snyman et al, 2008).…”

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“…is the wetted area in the regenerator. From an energy balance (i.e., setting the change of the gas enthalpy equal to the heat transfer between the gas and the regenerator), we obtain the regenerator effectiveness to be [14] e = NTU 1+NTU…”