Effects Of Water On Combustion And Emission Of Engines

In-cylinder direct injection technology engine（GDI）has become a research hotspot at the present stage because it can reduce the emissions of unburned hydrocarbons（UHC）and increase fuel economy and power performance through efficient control injection strategy.As the compression ratio of GDI engine increases,a series of problems are brought about,the most important one is the abnormal combustion of engine-knock combustion.In those measure to restrain the knock,water spray can effectively inhibit knock,and the principle of water spray is simpler,on the one hand because of its larger latent heat,water temperature of combustion chamber mixture can have a good cooling effect,thus can effectively inhibit knock,on the other hand water involved in the combustion process of a series of chemical reactions,so the water in the combustion process is very important for the influence of chemical reaction.In order to study the physical and chemical role of water in the engine combustion,this paper takes the team set up four yuan gasoline substitute mixture agency/basis of diisobutylene,first through the ignition delay validation and different fuel HCCI engine verify its accuracy,the results show that the proposed and the experimental results have good consistency,the average temperature in cylinder is analyzed by numerical simulation,the heat release rate and combustion process in the important product of CH₂O,OH and H₂O with the change of the crankshaft Angle,the average temperature in cylinder and heat release rate and heat release rate,The mole fraction of CH₂O gradually decreases with the increase of water spraying ratio and the time of peak generation gradually moves backward,and the trend of consumption after peak generation is roughly consistent.There is a tendency to inhibit the spontaneous combustion of the end mixture.The temperature sensitivity analysis showed that the reaction which affected the formation rate of OH,CH₂O and water was relatively high,and the addition of water inhibited the decomposition of R156:H₂O₂ into OH.Promoted the reaction in the first stage of R141.The reaction with the highest rate of H₂O generation was always R119,which consumed the main chemical reaction of H₂O,R141.Then this paper establishes the three-dimensional model of the engine through contrived software.The grid independence is verified by comparing the average pressure in the engine cylinder with the average temperature in the engine cylinder.By comparing the experimental data and the simulated data in the combustion process of the engine,the experimental data and the simulated data are basically the same,and the error is relatively small,indicating the accuracy of the calculation model and selected the basic size of the grid.Then this paper will be proven TRF/DIB quaternary reaction mechanism and validated the three-dimensional model of coupling,simulate the pre-mixed water inlet1.5%inside the engine cylinder combustion and emission process,not the pre-mixed water conditions at-10°CA,points CH₂O high-concentration area under the left side of the consumption gradually,this time the mixture combustion phenomenon,at the end and pre-mixed water is 1.5%.-6°CA not pre-mixed water on the right side of the upper appeared when the consumption of large amount of CH₂O shows its spontaneous at this time.In the condition of unpremixed water,the main combustion stage appears earlier and the combustion stage ends earlier.The CO emission of unpremixed water and premixed water is similar to 1.5%.-8°CA,the former at the end of the right upper earlier mixture combustion phenomenon is more obvious.NO_X emission is better under the condition of 1.5%premixed water.Finally,the combustion and emission processes of the engine cylinder without spraying water and with different spraying ratios and at different spraying moments are simulated.The average pressure in the cylinder decreases gradually with the increase of the water spraying ratio and the time when the peak value is delayed.When comparing the spraying ratio of 0.5%with that of 1.5%,the moment of peak value is delayed.The spray ratio of 2.5%is better in inhibiting the spontaneous combustion of the end mixture,and the CO emission of spray ratio of 2.5%is more,and the NO_X emission of non-spray ratio is more.Hydraulic moment from-130°CA to-70°CA,average pressure and average temperature in cylinder peak is reduced,and the average pressure in cylinder and average temperature peak moment.Engine operation to 5°CA,hydraulic moment for-130°CA-100°CA and occurred on the edge of the center of the local temperature is higher,the water spray time is 130°CA and emerged-100°CA mixture combustion at the end of the trend,as the spraying time delay,delay the heat release rate peak time,hydraulic moment for-70°CA short time internal energy release more heat,not spray CH₂O generated,the earliest hydraulic moment-70°CA at the latest.NO_X emissions hydraulic moment-100°CA and moment-70°CA is better.