1976-02-01

Engine Cycle Simulations and Comparisons to Real Engine Performance 760155

An analytical framework is assembled, suitable for the quantitative evaluation of engine performance (fuel consumption, WOT, NOx emissions) and the appreciation of engine performance sensitivities and trade-offs. Emphasis is placed on complete, conventional spark-ignition engines in production. The framework is assembled primarily from existing and well documented analyses that deal effectively with various specific aspects of the internal combustion engine. A new and non-conventional approach is followed in the treatment of engine breathing dynamics. The engine-manifold system is treated and documented as a sequence of many small but finite control volumes, each obeying individually the field form of conservation equations. The qualifications of the analytical framework are evaluated by an extensive comparison of analytical results to dynamometer test results of engines with fairly well known design and control parameters, which are also presented. Results of two production (one 8- and one 4-cylinder) engines are used over a wide range of loads and speeds. Extensive comparisons are illustrated of BMEP, BSFC, BSNOX and WOT air flow. Agreement ranging from good to fair is observed depending on operating conditions, with the comparison becoming poorer at very low loads and high EGR rates. Various factors, limiting the resolution of applications are discussed.

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