Research On The Influence Of Injection Method On The Mixture Formation,combustion And Emission Of Hydrogen Internal Combustion Engine

The energy shortage and emission pollution caused by extensive application of automotive internal combustion engines have become the major headaches in the development of automotive powertrain for nearly half a century,which in turn promotes the development of new-type clean-energy vehicles.Hydrogen fuel has become an essential alternative fuel for internal combustion engines due to its clean,environmentally friendly and renewable characteristics.Hydrogen has a small molecular weight and extremely low density,which causes air supply binding owing to the rapid diffusivity during fuel supply.Hydrogen supply affects abnormal combustion and emission characteristics to a large extent,which has become a significant research subject of combustion system matching of hydrogen internal combustion engine.This paper studies the effects of injection mode on fuel-air mixtures,abnormal combustion,combustion and emission characteristics of the hydrogen engine based on JH600single-cylinder port injection hydrogen engine test bench and combined with CFD simulation,so as to provide theoretical foundation and feasible parameters for optimal control of the hydrogen internal combustion engine.The main research work and conclusions are as follows:1.A three-dimensional solid model is established based on the tested JH600single-cylinder four-valve port injection hydrogen internal combustion engine.The FIRE software platform is used to complete the CFD simulation model construction,which includes dividing the three-dimensional computational grid,setting initial conditions and boundary conditions,and committing the flow,combustion and emission models.The simulation model is verified based on the in-cylinder pressure and heat release rate curves obtained from experiments.The results indicate that the established CFD model has a high simulation accuracy.2.Based on the CFD model,the effects of different injection modes on the intake and mixing are simulated.It is found that the single injection mode with higher injection pressure does not have a significant effect on improving the blockage of intake port,while the single multiple injections and symmetric dual injection have a significant effect on improving the blockage of intake port.Using symmetric dual injection and multiple injections can not only improve the air intake,but also enhance the in-cylinder average turbulent kinetic energy and mixing uniformity.3.The study from simulation reveals that the hydrogen injection mode and phase have essential effects on the formation process of hot spots in the cylinder,hot spots surface area and high temperature duration.The use of symmetric dual injection can significantly reduce high temperature surface area,maximum temperature and high temperature duration compared with single injection.The hydrogen injection modes affect the amount of residual hydrogen in the intake port,which in turn affects the probability of backfire.The delay of injection phase has an inhibitory effect on the development of low-speed hot area.4.The injection mode plays an important role in the flame development of in-cylinder,heat release law,in-cylinder pressure,in-cylinder temperature and formation of NOx.The simulation results demonstrate that the symmetric dual injection is beneficial to improve the rate of flame propagation,obtain higher instantaneous heat release rate,enhance the in-cylinder pressure and temperature,and improve power and thermal efficiency.It is found that the use of symmetric dual injection will also increase NO mass fraction,leading to the deterioration of emission performance of the hydrogen internal combustion engine,which needs to be further optimized and compromised with power.