Multi-Parameter Optimization of Marine Diesel Engine Turbo-Assisted EGR System
To determine the matching law of coupled optimization of diesel engine,exhaust gas recirculation(EGR)system and turbocharging system,a one-dimensional(1-D)model based on two-stage turbocharged SC7H diesel engine is built and verified in GT-Power,and the 1-D model of the turbo-assisted EGR(TA EGR)coupled two-stage turbocharged diesel engine is reconstructed.A three-step matching framework based on the demand of λ and EGR rate is proposed to address the matching problem of TA EGR coupled two-stage turbocharging system.The matching law shows that,the high-pressure/EGR turbine mass flow ratio and the high-pressure/low-pressure stage pressure ratio are linear basically.The inlet and outlet pressure difference of the TA EGR increases and then decreases with increasing pressure ratio,taking the optimum around the pressure ratio of 1,which is 35.35 kPa higher than the high-pressure EGR.The TA EGR has a better pumping process than the high-pressure EGR.The NSGA Ⅱ algorithm is used to perform the multi-parameter multi-objective optimal matching study of the coupled system through the fully connected neural network as the agent model of the 1-D model.The optimized matching results show that TA EGR has a better BSFC-NOx emissions.The TA EGR has a better fuel economy with 5.20 g/(kW·h)lower than the HP EGR at the Tier Ⅲ weighted NOx emission limits.
diesel engineexhaust gas recirculation(EGR)two-stage superchargedmatching methodfuel consumption and emissions
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