Effect of combustion on the economic operation of endoreversible Otto and Joule-Brayton engine

To simplify analysis of an internal combustion engine, air-standard cycles are conceived. Air is assumed to behave like an ideal gas. In practice, air-standard analysis provides useful indication of the trends that the engine is likely to follow. Air-standard Otto and Joule-Brayton cycles are bona fide assumption and cannot represent the complex combustion process occurring in the internal combustion engines. In this paper, the complex combustion process is represented by a parameter called fuel-flame temperature. The effect of combustion on the thermoeconomic performances of Otto and Joule-Brayton engines are studied. It is observed that the efficiency at maximum power is less than the Curzon-Ahlbom efficiency. The economic performance of the engine deteriorates due to combustion. The efficiency of the engine corresponds to maximum specific-power output, depends not only on the fuel-flame temperature, but also on the specific heats of the air and fuel. Ideal gas assumption of the working fluid is relaxed in this paper. Although somewhat idealized, the effect of combustion on the performance and economics of the internal combustion engines gives a reasonable design goal and better understanding of the real-heat engine. (C) 1998 , Ltd