Influence Of Hydrogen On Combustion And Emission Performance Of Gasoline Engine At Medium And High Speed

Growing energy demand and stringent emissions regulations have led researchers to explore more efficient and environmentally friendly alternative fuels,and prompt the transformation of traditional engines.Hydrogen has the advantages of low ignition energy,fast diffusion speed,fast flame propagation speed,wide ignition limit,etc.Adding hydrogen in gasoline engine can improve the performance of the engine to some extent.In this paper,the composite injection method of hydrogen injection in the inlet and gasoline injection in the cylinder is adopted.By combining numerical simulation and theoretical analysis,the influence of hydrogen energy fractions on combustion performance and emission performance of the engine under the coupling of medium and high speed and high load is explored.That is to say,the effects of the addition of0%,5%,10%,15%and 20%of hydrogen energy fraction in gasoline on the cylinder velocity field,the distribution of hydrogen in the cylinder,the combustion characteristics,as well as the power,economy and emission of gasoline engines under the conditions of 100%load rate,90%load rate and 80%load rate of 3500r/min,4500r/min and 6000r/min are investigated.The results show that the combustion performance of the engine is the best when the hydrogen energy fraction is 10%at the 100%and 90%load rates of 3500r/min,4500r/min.At 80%load rate of 3500r/min,the combustion characteristics of the engine are slightly improved when the hydrogen energy fraction is 10%,and the power and economy are close to those of pure gasoline engines when the hydrogen ratio is 10%and 15%.At a load rate of 80%of 4500r/min,addition of hydrogen cannot improve the power and economy of the engine.At 6000r/min,dynamic is best when the hydrogen energy fraction is 10%,and economy is best when the hydrogen energy fraction is 15%under 100%loading rate;dynamic is best when the hydrogen energy fraction is 20%,and economy is best when the hydrogen energy fraction is15%under 90%loading rate;the combustion performance is the best when the hydrogen energy fraction is 10%under 80%loading rate.In terms of emissions,the overall CO mass fraction is at a very low level.Under the same working condition,the mass fraction of CO₂ gradually decreases with the increase of hydrogen energy fraction.Under the 100%and 90%load rates of 3500r/min and 100%load rates of4500r/min,the mass fraction of NO is higher than that of pure gasoline engine when the hydrogen energy fraction is 5%and 10%.Under the 80%load rate of 3500r/min,the mass fraction of NO is higher than that of pure gasoline engine when the hydrogen energy fraction is 5%,10%and 15%.Under the 90%and 80%load rates of4500r/min,when the hydrogen energy fraction is 10%,the mass fraction of NO is larger than that of pure gasoline engine.At 100%and 80%load rates of 6000r/min,with the increase of hydrogen energy fraction,the mass fraction of NO first increases and then decreases,and both are larger than that of pure gasoline engine.