Simulation Research On EGR And Multiple Injection To The Performance Of A Marine Diesel Engine

In order to solve environmental problems and realize the slogan of "green ship,green shipping",countries have formulated increasingly stricter emission regulations.EGR and multiple injection strategy are in-engine emission reduction measures which have great application potential to reduce emission effectively of Marine diesel engines.In this paper,a one-dimensional simulation model of a Marine low-speed two-stroke diesel engine was established by using GT-Power,and a high-EGR system was added.The influence of EGR and post-injection on the power,fuel economy and emissions of diesel engine are studied.Firstly,the effects of EGR rate and EGR temperature on the performance and emission of diesel engine were studied under the single injection.The EGR tremperature was fixed at 450K,and the EGR rate was changed appropriately by changing the opening of the EGR valve.The sinulation results show that the displacement of NOx reduced rapidly with the increasing of EGR rate while the power and fuel economy of diesel engine are reduced.The displacement of Soot is increased.When the EGR rate reaches a certain value,the displacement of Soot increases rapidly.Then the effect of EGR temperature on the performance of diesel engine was studied under the EGR rate is 20%.The results show that high EGR temperature could lead to the increasing of the displacement of NOx and Soot,and result in the reduction of the power and the increasing of BSFC of diesel engine.Therefore,the EGR temperature should be reduced as much as possible.Secondly,under the premise of constant circulating fuel injection,the influence of the interval between post injection and main injection and post injection quantity on the performance and emission of diesel engine is studied under full load working condition.The brake power decreases and the BSFC increases as the interval is larger.The displacement of Soot decreases,and the displacement of NOx increases at first and then decreases.Therefore,the interval should not too large or too small.The displacement of Soot and NOx deerease while the power and economy of diesel engine decrease as the quantity of post injection is larger.For this reason,the quantity of post injection should not too large.Finally,this paper studies the effects of EGR coordinated post injection on performance and emissions of diesel engines.EGR rate was set to 20%,interval between post injection and main injection was set to 15oCA and the quantity of post injection was set to 10%of circulation injection.Compared to using EGR under single injection,using EGR coordinated post injection can reduce the displacement of NOx and the displacement of Soot is reduced by about 55%,which perfectly solves the problem of increasing of Soot caused by using EGR.However,the brake power is reduced by 5.33%and the BSFC increase by 5.65%.