One-Dimensional Simulation Performance Optimization Study Of Marine Medium-Speed Diesel Engine Based On Multiple Injectors

Marine Medium-Speed Diesel Engines are widely used in marine power units because of their high thermal efficiency,fast braking,good reliability and adaptability.Due to the requirement of energy saving and emission reduction,it is important to further improve the effective thermal efficiency and reduce NOx emission of marine medium-speed engines.Traditional marine medium-speed diesel engines use central single injector injection with larger injectors and more fuel injection,when fuel and air are mixed for combustion,combustion usually occurs near the combustion chamber walls and squeeze area,resulting in low utilization of fresh air in the center of the combustion chamber.In recent years,a multi-injector system has been proposed,in which multiple injectors are installed on a conventional direct injection diesel engine.In the multi-injector system,by adjusting the arrangement angle and fuel ratio of multiple injectors,not only can spray interference and wall impact be minimized,but also the air utilization near the center of the combustion chamber can be improved to promote mixture formation.However,at present,there are few studies on marine medium-speed diesel engines for multi-injector system.In this paper,the effective thermal efficiency and NOx emission of a marine medium-speed diesel engine are optimized based on multi-injector system through one-dimensional simulation.In this paper,a marine medium-speed diesel engine of the China Shipbuilding Power Research Institute is taken as the research object.Firstly,a one-dimensional simulation model of a medium-speed diesel engine with single injector is established by using the simulation software GT-Power,and the calibration of the single injector simulation model is completed based on the experimental data of the single-cylinder test platform,while a multi-injector system model is established on the basis of the central single-injector model,after which two side injectors are added on the basis of this model to establish The multi-injector system simulation model is then added to this model to establish the multi-injector system simulation model,and then the calibration of the multi-injector is completed using the test data of the fully validated CFD simulation model.Then,based on the single-injector marine medium-speed diesel engine model,the effect of injection timing and intake and exhaust timing on engine performance is studied,and then multi-objective optimization is carried out through the DOE method.Then,based on the multi-injector marine medium-speed diesel engine model,the effect of different fuel ratios of side and central injectors and different injection timing on the diesel engine performance is studied.Finally,the intelligent optimization of diesel engine performance is carried out by coupling GT-Power and Simulink with genetic algorithm.The study shows that:single injector diesel engine by properly advancing the injection timing and adjusting the intake and exhaust timing at the same time,the NOx emission decreases by 1.062(g/kw·h)and the thermal efficiency increases by 0.168%;multi-injector system,when the fuel ratio of side and central injector is smaller,the thermal efficiency is higher,but the NOx emission is also larger,and when the fuel ratio exceeds 0.5,the thermal efficiency decreases instead.With proper injection strategy(injection timing and fuel ratio),the multi-injector system can improve the thermal efficiency of diesel engine while reducing NOx emission.Combined with genetic algorithm for optimization calculation,the effective thermal efficiency of diesel engine is increased by 0.71%,and NOx emission is decreased by 1.458(g/kw·h).