Study On Miller Cycle And Two Stage Turbocharged Of Diesel

Currently, with the deterioration of energy crisis and living environment becomingincreasingly severe, requirements are stricter with the economic performance and emissionsperformance of marine diesel engine. As the regulations of diesel engine emissions, especiallythe emission standards for NO_x of International Maritime Organization (IMO), are becomingmore and more stringent, how to reduce the NO_x emissions of diesel engines has become oneof the important research topics of related fields. It has been proved that NO_x emissions couldbe effectively reduced by the combination of using Miller Cycle and Two-StageTurbocharging. In this research, TBD234V12diesel engine is chosen as the research object,the GT-Power simulation software works as a platform, and the simulation model of the dieselengine has been established. To predict NO_x emissions, during the calculation of the cylinderworking process, the oil droplets evaporation combustion model and the quasi-dimensionalcombustion model based on extended Zeldovich mechanism are selected to perform asquasi-dimensional combustion model.Firstly, the original machine simulation results are compared to the experimental results,and the accuracy of the simulation model are verified. Then Miller Cycle research is appliedto the verified original machine model to study its influence on the diesel engine performanceand NO_xemissions. By the results of Miller Cycle simulation under different loads, it isproved that NO_xemissions could be reduced by30%in high load, and the best Miller valvetiming angles of diesel engine in different loads are settled. On such basis, according to thepropulsive characteristics ofN_c=Cn~3, two supercharged matching calculation has beencarried on diesel engine. By taking comparative analysis on the calculation results of differentprograms, it is finalized that the preferred high pressure stage is GT3788turbocharger, and thepreferred low pressure stage is GT4294turbocharger. By applying Two-Stage Turbocharging,in low load, the fuel consumption is reduced by10%; in high load, the NO_xemissions drops30%.Secondly, in order to better realize the Two-Stage Turbocharging arrangement on dieselengine, a three-dimensional model of TBD234V12diesel engine is established withPro/Engineer3D modeling software. On such basis, design of this machine’s Two-Stage Turbocharging system is carried out, and structural arrangement is taken on the diesel engine.According to diesel engine’s intake and exhaust structures, as well as the size of the selectedturbocharger, the intake and exhaust connecting pipe of Two-Stage Turbocharging system isdesigned. A solid model of the intake and exhaust connecting pipe is built with Pro/Engineersoftware. Under different loads of diesel propulsion characteristics, flow field calculation andanalysis of the intake and exhaust pipes are taken with Fluent software.Finally, a highly versatile Miller Cycle timing mechanism is designed based on the gasdistribution agencies of TBD234V12diesel engines, which can achieve continuously variablevalve timing of the intake valve. And the three-dimensional model of such Miller Cycleinstitutions is established with Pro/Engineer software.