Modeling And Combustion Characteristics Of Marine Diesel/Natural Gas Dual Fuel Engine Based On MATLAB/Simulink

In recent years,environmental pollution and energy shortage have become two major obstacles to human development,so the dual fuel engine has been paid more and more attention because of its advantages of cleanness,high efficiency and good economy.Compared with pure diesel engine,the combustion process of Diesel / dual fuel engine is more complicated,The traditional marine diesel engine adopts the diffusion based combustion mode,while the marine diesel / natural gas dual fuel engine uses natural gas to replace most of the diesel,which changes the energy ratio and chemical reaction rate released in the premixing and diffusion combustion stage of the original diesel engine.Therefore,the research on modeling technology and combustion characteristics of Diesel / natural gas engine has become a hot and difficult point.Based on the MATLAB / Simulink software platform,taking the Yuchai 6K marine diesel / natural gas engine as the research object,this paper adopts the modular modeling concept,the comprehensive use of charging and discharging method,the average value method,the combination of map and empirical formula to establish the dual fuel engine model.Through the comparison and repeated correction of simulation results and test results,the control model error is about 0.5%.The effects of three different operation modes of the dual fuel engine on the combustion process in the cylinder under different working conditions are studied.The results show that the dual fuel engine is suitable to operate in the pure diesel operation mode or the dual fuel mode with low natural gas substitution rate,while the maximum gas mode and the dual fuel mode with high substitution rate are more suitable to operate in the medium and high conditions Load condition: the influence of the intake parameters of the dual fuel engine cylinder on the working process in the cylinder is studied.The results show that the intake pressure of the cylinder is increased by 1 bar,the maximum explosion pressure of the engine is increased by 22 bar,and the maximum average temperature is decreased by 21%,while the intake temperature of the cylinder is increased by 60 K,The maximum average temperature in the cylinder is increased by 14%.Therefore,increasing the intake pressure of the cylinder and reducing the intake temperature of the cylinder are conducive to improving the overall performance of the engine and reducing the emissions of pollutants.The characteristics of the two injection strategies of single injection and two injection of the fuel system of dual fuel engine are studied.The results show that increasing the injection timing properly in a single injection can improve the performance of the engine Pressure and temperature to optimize the combustion process.When two times of injection,proper increase of pre injection timing and pre injection quantity can optimize the parameters of cylinder pressure and temperature and improve the overall performance of the engine.The results of this study reveal the influence of the intake parameters of the engine cylinder,the fuel injection strategy of the fuel supply system and the operation of the engine with different natural gas substitution rate under different load and different speed conditions on the combustion characteristics of the dual fuel engine,providing basic research data for improving the performance of the marine dual fuel engine.