Effects Of Intake Port Water Injection And Exhaust Gas Recirculation On Combustion And Emissions Of High Power Diesel Engine

At present,the maximum power density of the High Power Diesel Engine has reached 100k W/L,and the heat load is very high while obtaining high power.Intake port water injection and exhaust gas recirculation have strong application prospects as a technical measure to reduce the heat load of highly enhanced diesel engines and reduce emissions.This paper takes a domestic four-valve single-cylinder High Power Diesel Engine as the research object,and studies the effects of the combined action of Intake port water injection and exhaust gas recirculation on the combustion and emissions of the High Power Diesel Engine through simulation.Research demonstrates:Under the effect of Intake port water injection,with the increase of the water-to-oil ratio,the lag period of the High Power Diesel Engine increases,its maximum combustion temperature and the maximum combustion pressure in the cylinder increase first and then decrease.The reason is as follows.The heat absorption of water evaporation in the passage reduces the intake air temperature and the intake air density,while the injection of water prolongs the stagnation period and raises the proportion of premixed combustion.Therefore,the pressure in the cylinder increases suddenly after the start of combustion.Then the increase in oil ratio restrain combustion.At the time when the water-oil ratio is 0.6,the maximum combustion temperature in the cylinder decreases by 83K,the maximum explosion pressure decreases by 0.1 MPa,and NO_X decreases by 33%,while Soot increases slightly.Under the effect of exhaust gas recirculation,as the EGR rate increases,the maximum combustion temperature,the maximum burst pressure,the maximum pressure increase rate and the indicated power in the cylinder all decrease,the combustion in the cylinder decreases,the combustion center of gravity shifts backward,and the exhaust temperature increases,and this When NO_X emissions decrease,Soot increases.Therefore,by increasing the intake air pressure and changing the fuel injection quantity to keep the engine’s indicated power unchanged,the maximum combustion temperature in the cylinder decreases by13.7%,the maximum explosion pressure increases by 17%,and the exhaust temperature decreases by 55.1K.at the EGR rate of 20%,Therefore,it can effectively reduce the problem of high heat load of High Power Diesel Engines,Meanwhile NO_X is reduced by 84%,indicated fuel consumption increased by 3.17%.Under the combined action of water injection in the intake port and exhaust gas recirculation,the maximum combustion temperature and the maximum burst pressure in the cylinder are reduced and the trade-off relationship between NO_Xand Soot can be effectively improved when the water-oil ratio is 0.2.