Investigation Of The Natural Gas Injection Strategy Of A Diesel Natural Gas Dual Fuel Engine

The advantages of natural gas / diesel dual fuel engine, such as high compression, have been paid more attention. But now there are still some problems, such as low load high THC emission and high load engine knock. With the research team prior to the dual fuel engine research results, We aimed to study the strategy of natural gas injection, analyzing of the influence on the performance of dual fuel engine.In this paper, it includes the calculation of the experimental study and simulation. The part of experimental study is a combination of excess air coefficient, studying the influence of inject direction and inject time on performance of dual fuel engine. Simulation of the part is to analyze the impact of injection direction and injection time of natural gas micro field. Test and simulation research process include computing platform build, writing test and simulation program, analyzing of the key parameters in the late. The results are shown as follows:Natural gas inject time can get different gradient micro gas field. With the delay time of the jet, the gas concentration field gradually from top dilute and lower strong to top strong and lower dilute.Gas inject time has little effect on the torque. Just in time delayed or inject in advance, the parameters of performance deteriorate. Influence of injection time on cylinder pressure and heat release rate of the combustion parameters is relatively large. Under different excess air coefficients,the effect is different. Especially in the lower excess air coefficient is relatively small,these parameters change is especially obvious. In the low excess air coefficient, the inject time effect on emission is more obvious, especially in advance or postpone the inject time, and THC emissions will rise. Considering the choice of injection timing is 300 °CA BTDC, the combustion and emission is ideal.The inject direction of natural gas field has little effect on the micro. The axial concentration changes is little, and radial concentration change is strong. Influence of inject direction on the performance of the dual fuel engine is much smaller than the inject time. In the study of 45 degrees and 90 degrees with inlet axis on the performance of the dual fuel engine, we find that with the inlet axis into a larger angle, the mixture is more uniform, then they are the better the effect of combustion and emission. But some inject degrees will block form the interference angle of inlet and inlet shape,and these cause combustion and emissions worse.Influence of excess air coefficient on dual fuel engine is very obvious. With decreasing air coefficient, torque increases first and then decreases, and the maximum cylinder pressure increases first and then decreases, and THC emission increases first and then decreases. These mean that critical air concentration is important to combustion of natural gas and diesel. So in the air of different concentrations, the change of natural gas field will be important to combustion and emission effect. And changing the inject strategy can get different micro gas field.