Experimental investigation of the influences of Miller cycle combined with EGR on performance, energy and exergy characteristics of a four-stroke marine regulated two-stage turbocharged diesel engine

Abstract

In order to explore the technical route to meet the Tier III emission regulations, the experimental study of the influence of Miller cycle combined with EGR on the performance, energy and exergy of a four-stroke marine regulated two-stage turbocharged diesel engine was achieved by redesigning the camshaft and EGR system. The results shown that Miller cycle combined with EGR increased the peak HRR of premixed combustion period, decreased the peak HRR during the main combustion period, and delayed the crank angle corresponding to the peak HRR, resulting in longer combustion duration and a later 50% combustion position. In the 75% load, the combination of medium Miller timing and medium EGR rate can not only meet the NOx emission requirements of Tier III, but also far superior to only high EGR rate in terms of fuel economy, opacity performance and COVIMEP. As the EGR rate increased, heat transfer energy to coolant, BTE and ITE dropped significantly, while exhaust energy and combustion loss increased significantly. The change trends of exergy terms with EGR rate and Miller timing were similar to their corresponding energy. It should be noted that the exhaust energy was about 2.5 times larger than the exhaust exergy while the heat transfer energy to coolant was about 8 times larger than the heat transfer exergy to coolant, which indicated that the recoverable potential of heat transfer energy to coolant is much smaller than exhaust energy.