Effect Of Natural Gas Injection Direction And Timing On Combustion Performance Of Dual-Fuel Engine

Today,as environmental pollution and energy crisis become more and more serious,emission regulations become more and more stringent.It is the latest trend to use clean and safe natural gas instead of traditional diesel as the main fuel of ships.But with natural gas as the main fuel,there is a problem that the propagation speed of natural gas and air mixture flame is slow and the charging efficiency is low.Therefore,studying how to inject natural gas can form a natural gas distribution that is beneficial to the rapid combustion and spread of natural gas at the end of the compression stage is a hot topic in the field of bi-fuel engines.Jet direction and jet timing directly affect the distribution of natural gas in the cylinder.In this paper,a three-dimensional numerical simulation method is used to study the influence of engine intake,compression and combustion stages on a dual-fuel diesel/natural gas engine to improve the power,economy and emission of the dual-fuel engine.This paper designed four kinds of natural gas injection direction of the program,respectively 0 degrees,30 degrees,45 degrees,90 degrees four inject direction.The effects of different inject directions on various stages of the engine are studied in detail.Choosing the right direction of the CH₄ injection will make the distribution of natural gas more conducive to improving the combustion performance of the engine,and make the various flow fields in the engine more favorable to the development of natural gas combustion,thereby improving the performance of the engine.For this dual-fuel engine model,the distribution of natural gas formed at 90°jetting is most favorable to the rapid combustion of natural gas at 100%load.The peak temperature and pressure in the cylinder are increased by 5.7%and 12.5%respectively%,But the corresponding NO emissions increasedBased on the optimal 90-degree nozzle assembly engine model,the effect of natural inject timing on the engine working process was studied.Inject timing has a significant effect on the engine intake process,and late injection Natural gas will make part of the natural gas can not enter the cylinder,resulting in natural gas waste,the formation of natural gas distribution is not conducive to engine combustion,dual-fuel engine power performance declined.Although the engine that Injecting natural gas at 360°CA has the highest performance values of temperature and pressure,the excessive peak pressure and pressure rise rate have a certain adverse effect on the life of the engine,and the NO emission in the cylinder is too large,and the engine emission is poor Taken together,the 370°CA injection timing is the best overall jet timing for this dual fuel engine.Finally,the simulation results of the influence of injection direction and injection timing on the intake process and the combustion process of the dual-fuel engine are provided,which provide the theoretical basis and optimization scheme for the later reform of the dual-fuel engine.