Exergy and energy analysis during cold-start and warm-up engine operation

Cold-start is an inevitable part of the daily driving operation for most vehicles. Given that exergy analysis can evaluate the sources of losses qualitatively and quantitatively using the first and second laws of thermodynamics, this study investigated the impact of engine temperature on energy and exergy parameters during engine warm-up. Using a turbocharged Cummins engine, the performance and emissions data were measured, and energy and exergy parameters were formulated from the experimental data. Engine warm-up period was divided into seven phases, including official hot-start and cold-start, and some phases which are not considered as cold-start or hot-start by regulations. This study evaluated different parameters related to energy analysis (brake power, friction mean effective pressure [FMEP], brake specific fuel consumption [BSFC] and brake thermal efficiency [BTE]), exergy analysis (fuel input exergy, exhaust heat loss, exergy destruction and exergetic efficiency) and their correlations. Results showed that as the engine warmed up, the fuel exergy, exhaust heat losses, and exergy destruction decreased by 2.3, 34.1 and 34.1%, respectively; while, the exhaust exergy loss increased by 43.5%. The FMEP and BSFC decreased by 56.7% and 14.9% as the engine warmed up, while BTE and the exergetic efficiency increased by 5.6% and 5.3%, respectively.