Modeling And Parameter Optimization Of Flue Gas Waste Heat Recovery System For A Marine Dual-Fuel Engine

With the globalization of the economy and the booming of the ship industry,the marine engine has caused emission problems and thermal pollution problems that need to be solved.To meet the strict requirements of domestic and international emission regulations,dual-fuel engines are attracting attention for their low emissions.Natural gas is considered one of the best alternative fuels for dual-fuel engines due to its large global reserves and low combustion emissions.Dual-fuel engines have the same waste heat problem as traditional diesel engines,and the relatively high flue gas temperature of dual-fuel engines is more conducive to waste heat recovery and utilization of flue gas.To study the recovery and utilization of flue gas waste heat of a marine four-stroke MAN 51/60 DF dual-fuel engine,a waste heat boiler is used to recover the flue gas waste heat.To study the recovery and utilization of exhaust gas waste heat of a marine four-stroke MAN 51/60 DF dual-fuel engine,a waste heat boiler is used to recover the exhaust gas energy.Based on the modular modeling principle,the mathematical models of the diesel engine and the waste heat boiler were established,respectively.Based on the GTPower simulation modeling tool,the one-dimensional model of the dual-fuel engine was established.Before the optimization study of the dual-fuel engine,the calibration of simulation data is with a maximum error of 1.96% in the gas mode.Then the main parameters of the waste heat boiler were designed,and the Simulink simulation model was established.And then the power generation of waste heat from flue gas was calculated based on the mathematical model of the turbine.The effects of intake temperature,geometric compression ratio and pilot fuel injection timing on the engine performance and the power generation from flue gas waste heat in the gas mode of the dual-fuel engine were investigated.The objective is to obtain the maximum possible engine power and flue gas waste heat generation power with a small fuel consumption rate;Multi-Objective Genetic Algorithm(MOGA)and Multi-Objective Golf Grey Wolf Optimizer(MOGWO)are used to obtain the optimal parameter settings.The optimal solution set is obtained by algorithmic optimization,and the fuel consumption rate is used as the main reference factor to artificially select the optimal solution.The result showed that the best optimal solution is obtained when the intake temperature is 309.25 K,the geometric compression ratio is 14.86,and the pilot fuel injection timing is-16.97°CA after the top dead center.The corresponding fuel consumption rate was 155.39 g/kWh,reduced by 3.01%,and the power was 8026.41 kW,increased by 0.33%.At the same time,285.98 kW of flue gas waste heat generation was obtained.Thermal efficiency was 47.73%,an improvement of 4.24%.In conclusion,this study provides a method for modeling and optimizing the waste heat recovery system of a four-stroke marine dual-fuel engine.The results contribute to a better understanding of the effects of operating parameters on performance and flue gas waste heat utilization.RSM is applied to engine performance and flue gas waste heat utilization,combined with MOGA and MOGWO,respectively,to calculate the engine parameter settings through algorithmic optimization while satisfying the conditions of performance and flue gas waste heat recovery.