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This paper presents preliminary data and results for a system mathematical model for a proposed Otto Cycle / Stirling Cycle hybrid-engine-based power generation system. The system is a combined cycle system with the Stirling cycle machine operating as a bottoming cycle on the Otto cycle exhaust. The application considered is that of a stationary power generation scenario wherein the Stirling cycle engine operates as a waste heat recovery device on the exhaust stream of the Otto cycle engine. This paper is primarily concerned with the development of a model for a suitable Stirling cycle engine capable of running on the high grade thermal energy present in the exhaust stream of the industrial Otto cycle engine under consideration. The Otto cycle engine is not modelled, with the relevant engine exhaust and performance parameters taken from published data. This was deemed a suitable step as the Otto cycle engine is an established technology and the engines on which the model is to be based are commercially available. Therefore use of the published data in this manner was favourable as it limited the extent of the model required and allowed focus on the Stirling cycle engine requirements. The modelling procedure for the Stirling engine follows the traditional sequence of Zero Order, First Order, Second Order as suggested in the classical literature. Zero Order analysis is completed in the form of the Beale analysis, First Order analysis utilises a Schmidt style method while the Second Order analysis utilises the Direct Method model. Modelling is based on data available for an industrial Otto engine system operating on natural gas, with the input variables being specified as the exhaust recoverable energy content and temperature at a constant speed of 1500rpm.
Cullen, B., McGovern, J., Feidt, M., Petrescu, S.: Preliminary modelling results for an Otto Cycle/Stirling Cycle hybrid-engine-based power generation system. 22nd International Conference on Efficiency, Cost, Optimisation, Simulation and Environmental Impact of Energy Systems (ECOS), Brazil, 2009.