Calculation And Experimental Research With EGR System For V Type Diesel Engine

With the energy crisis and the environmental protection consciousness enhancement, thediesel engine performance and emissions are increasingly high requirements. As one of themost effective means which reduce NOxemissions of diesel engines， exhaust gasrecirculation technology (EGR) in foreign countries has become a relatively maturetechnology and has been successfully applied in diesel engines.Based on a TBD234V12dieselengine, This thesis completes the design of turbocharged diesel engine EGR system, andstudy the different EGR system on diesel engine performance and emission effect.This thesis discusses the system of diesel engine NOx generating mechanism and a moredetailed analysis. For turbocharged diesel engine under high load average intake pressure ishigher than the average exhaust pressure, exhaust gas is difficult to recycle to the intake pipe,this thesis designs a set of a Venturi tube structure EGR system. In smaller influence under thepremise of inlet pressure, the system can make the exhaust introduced into the intake pipe,realize the exhaust mixed. And by using CFD software and its calculation model andsimulation analysis of the flow field in the different state of the EGR rate, verify the venturitube design.Stand on the basis of the original turbocharged diesel engine, this thesis selects of thesuitable EGR valve and the exhaust gas cooler, and completes the design of theV-turbocharged diesel engine EGR system test bench and structures. The experimentalscheme selected different operating points in EGR test, by adjusting the EGR valve to controlthe rate of EGR.To ensure the test of diesel engine working stability, The EGR rate is limitedin15%range. Sum up experience. Based on the test results were analyzed, the thesis sum upthe influence in cylinder and emission characteristics of EGR on diesel engine performance.Comprehensive parameters with EGR rate change trend, this thesis draws the best rate ofEGR test conditions.The research applies the GT-Power software to establish a V-turbocharged diesel engineEGR system simulation model. In accordance with the diesel engine standard propellercharacteristics, the research selects different simulation conditions. This thesis analyzes thecompression ratio and injection timing on diesel engine performance, and for differentoperating points to determine the optimal compression ratio and injection timing. Based on the load of75%cylinder three instantaneous moments of the flame zone are analyzed in detail,this thesis studies the NOxand Soot formation mechanism.For the study of different EGR system on diesel engine performance, this thesis usessimulation model of EGR parallel system and series system simulation calculation. Based onthe simulation results are compared and analyzed, the research shows that parallel EGRsystem can achieve higher EGR rate, while the series EGR system can reduce NOxemissionsat the same time of the diesel engine power performance and the economy performanceproduced smaller effects. In general, the use of EGR system with parallel system is moresuitable for the diesel engine.