The Study Of Flame Lift-off Length

The characteristics of the combustion in DI Diesel engines lead to high soot content in exhaust. The flame lift-off length in DI engines is known as one of the key parameters to influence Soot formation. Relatively static environment in Constant Volume Combustion Bomb help us changing a single parameter to study there influences on the lift-off length and the formation of Soot. In this paper, numerical study on the turbulent diffusion flame lift-off length in the direct injection diesel engine is going on. and the use of group-hole technology combined with EGR technology give us a way which may reduces soot and NOx emissions.In this paper, the constant volume bomb in Sandia National Laboratory and the 6NB-E diesel engine in YITUO company were used to built a three-dimensional simulation model with the STAR-CD software, and the validity of the model was verified by the experiment data. The nozzle diameter, the swirl ratio, the intake air temperature, the air density, the oxygen concentration and other parameters were changed, respectively, to study there influences on the flame lift-off length. And the use of group-hole technology combined with EGR technology was investigated, too.Simulation results show that the influence of the swirl ratio on the flame lift-off length is not significant. The influence of the initial intake air temperature and density are more visible. Little change in oxygen concentration lead to a very small change in flame lift-off length. Simulation also shows that: Small diameter group-hole technology can improve combustion and reduce soot emissions, but will bring a large number of generated NO_x. The use of group-hole technology combined with EGR technology give us a way which can reduce soot and NOx emissions.