Effects Of Hydrogen Doping At Low And Medium Speeds On Combustion And Emissions Of Direct Injection Gasoline Engines

The impact of internal combustion engine emissions on the environment is intensifying,and reducing emissions is imperative.As a promising energy source,hydrogen will play an important role in internal combustion engines by virtue of its excellent physical and chemical properties.Pure hydrogen internal combustion engines mainly have the problems of insufficient power and storage difficulties,and need more time to develop.In contrast,gasoline is the main fuel.By adding hydrogen to the traditional in-cylinder direct injection gasoline engine,changing the proportion of hydrogen-added energy can effectively use the advantages of hydrogen fuel to improve some problems caused by pure oil fuel.Considering that the common speed of the vehicle is in the middle and low speed;and the lean burn limit range of gasoline determines that the load interval is medium and high load.In summary,this paper explores the effects of different hydrogen-doped energy ratios on the combustion and emissions of direct-injection gasoline engines at low and medium speeds and medium and high loads through numerical simulation.The main work of this article is:firstly,based on the measured engine structural parameters,Solid Works was used to establish a three-dimensional model of the engine;then AVL-FIRE was used to calculate the simulation;finally,by comparing and analyzing the differences in power,economy,and emissions after hydrogenation and before hydrogenation The effect of hydrogen on the direct injection gasoline engine in the cylinder.At the same time,through comprehensive analysis and evaluation of power,economy,and emissions,it provides theoretical guidance for the hydrogenation strategy at low and medium speeds and high and medium loads.In this paper,hydrogen is injected in the intake port,and gasoline is directly injected in the cylinder.Under the same load,the total energy is fixed,and as the hydrogen-doped energy ratio increases,the gasoline energy will decrease accordingly.The research results show that:compared with the original machine,under the same speed and the same load,when the energy ratio of hydrogen is gradually increased,the introduction of high and low heating value fuel makes the cylinder temperature and cylinder pressure increase significantly,the highest temperature and highest in the cylinder The pressure value increases first and then decreases.Among them,most working conditions reach the maximum temperature and pressure in the cylinder at a hydrogen energy ratio of 10%.By blending hydrogen,the indicated power and indicated thermal efficiency of the direct injection gasoline engine in the cylinder are significantly improved,and the power and economy of the engine are significantly improved.At the same time,as the proportion of hydrogen doping increases,the content of C atoms decreases and CO₂ emissions continue to decrease.Although the maximum temperature in the cylinder and the maximum pressure in the cylinder increase first and then decrease,the overall temperature does not change much,so the temperature-type NO_X emissions change little.In the case of relatively stable CO emissions,overall emissions have also been improved to a certain extent.Finally,a dimensionless process is used to linearly weight the engine’s power,economy,and emissions.The results show that compared with the original machine,the combined working condition with better overall performance is obtained after hydrogen mixing.At the same time,the improvement of comprehensive emission performance in most operating conditions also shows the excellent effect brought by hydrogen doping,which provides a theoretical reference for the overall optimized hydrogen doping strategy.