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This paper addresses issues associated with the accurate determination of gross heat release energy. The magnitude of analysis and measurement errors has been quantified using simulated and measured gasoline engine pressure data. This has revealed that calculated gross heat release is very sensitive to the assumed ratio of specific heats, charge to wall heat transfer and pressure data errors. Two improved heat release models have been proposed and further investigated and shown to generally give good performance for specific applications although further work is required to fully quantify their accuracy.

This paper addresses issues associated with the accurate determination of mass fraction burned (MFB) in gasoline engines. Items covered include an evaluation of the accuracy of alternative MFB models and the effects of errors in the absolute pressure referencing, crank angle phasing and assigned compression ratio. The implications of using crank angle averaged pressure data and varying the crank angle resolution and number of engine cycles are also covered. The well known Rassweiler and Withrow MFB model was found to produce the best results in comparative tests with simulated and experimental pressure data. Absolute pressure referencing offset caused the largest error in the calculated MFB and burn angles, particularly at low engine load. Calculated data at the extreme ends of the MFB curve were shown to be most sensitive to measurement errors and noise.

This paper addresses issues associated with the accurate determination of indicated mean effective pressure (imep) for internal combustion engines. Items covered include a comparison of alternative imep equations and the effects of crank angle resolution, signal noise, thermal shock, crank angle phasing and connecting rod length errors. The best imep equation to use has been identified and the magnitude of errors under a wide range of conditions quantified. The results show that inaccuracy in the calculated imep will mainly be caused by thermal shock and errors in the crank angle phasing and transducer sensitivity. In contrast, the effects of coarse crank angle resolution, incorrectly specified connecting rod length, signal noise and integration period error should be relatively small.