Experimental investigation of the effects of Miller timing on performance, energy and exergy characteristics of two-stage turbocharged marine diesel engine

In order to analyze and improve the thermodynamic process of marine diesel engines and improve energy efficiency, the experimental study of the influence of Miller timing on the performance, energy and exergy of marine diesel engines was realized by redesigning the camshaft and adjusting the two-stage turbocharging system. The research results shown that with the increase of Miller timing, the average pumping loss decreased, the peak HRR and the maximum combustion temperature decreased, and the crank angle corresponding to the peak HRR was delayed backward, resulting in a backward delay of the 50% point, the 10?90% combustion duration was extended, and the EER, EEE and BTE first increased and then decreased. Secondly, the Miller cycle combined with two-stage turbocharging could make marine diesel engines reduced NOx emissions by more than 25% with a small effect on the BSFC. In addition, as the Miller timing increased, the proportion of exhaust energy, heat transfer energy to coolant, mechanical loss, and combustion loss all decreased, while the proportion of brake output work first increased and then decreased. The change trends of exergy terms with load and Miller timing were similar to their corresponding energy. It was worth noting that the exhaust exergy accounted for about 40% of the exhaust energy, while the heat transfer exergy to coolant accounted for only 13% of the heat transfer energy to coolant, indicating that the exhaust energy quality was higher, the utilization potential was greater, and the efficient utilization interval was concentrated in the high load area.