| With the upcoming emission legislation IMO Tier III, the research of exhaust gasrecirculation will have important theoretical significance and engineering guiding role toresearch and develop marine diesel engine which could meet Tier III emission legislation.The simulation research of EGR effects on performance and emission characteristics wereinvestigated on a medium speed marine single cylinder diesel engine in this paper. In order toreduce emissions and keep the brake specific fuel consumption(BSFC) lowest at the same time,the EGR diesel parameters such as injection timing、injection pressure、 intake pressure andMiller timing had been changed. Based on the simulation results, experiments were carried out atlast.The simulation results show that when increasing EGR ratio of different load points withD2test cycle, the ignition delay been longer, the maximum heat release rate decreased, and theweighted NOXemission of diesel engine decreased to1.87g/kWh which could meet the IMOTier III emission legislation, but the combustion of the diesel engine deteriorated, Soot emissionwent up, and the weighted BSFC increased4.07%at the same time. With the optimization ofinjection timing, the weighted NOXemission of EGR diesel engine rose to1.98g/kWh while theweighted BSFC only increased2.62%. Continuing optimizing the injection pressure of EGRdiesel engine, the weighted NOXemission increased to2.10g/kWh while the weighted BSFConly increased1.37%. Futher optimizing the intake pressure and Miller timing respectively,when the weighted NOXemission rose to2.22g/kWh and2.21g/kWh respectively, the weightedBSFC only increased0.77%and0.53%respectively, and the BSFC was optimized observably.Compared to the experimental results, it shows that the DIJet combustion model which hasbeen calibrated gives enough calculation precision to predict the performance and emission ofthe diesel engine, and this study validates the simulation model and the conclusions of parameteranalysis. |
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