Experimental Study On Heat And Exergy Balance Of Compound Injection Gasoline Engine

In recent years,with the increasing global energy shortage,energy conservation has attracted widespread attention.Because internal combustion engines(ICEs)occupy a large part of fossil fuel consumption,it is necessary to adopt some new technologies and methods to reduce energy consumption in the development and analysis of ICEs.Compound injection technology,as a newly developed technology,combines the advantages of port fuel injection and direct injection,and has good performance.It is a trend of future development of ICEs.As an ideal alternative fuel,hydrogen has many advantages,such as wide source,renewable and so on.Moreover,its unique properties have high application potential for improving engine power,economy and reducing pollutant emissions.In the field of thermodynamics,it is a scientific and comprehensive idea to synthesize the first and second laws of thermodynamics,because it not only considers the relationship between energy "quantity",but also makes a thorough analysis from the aspect of "quality".Based on the hardware of a compound injection engine,combined with hydrogen mixing technology,and combined with the first and second laws of thermodynamics,the effects of mixing ratio,engine speed,load and excess air coefficient on the heat balance and exergy balance of a compound injection engine were compared and analyzed.According to the "Surrounding Analysis Method",the engine is built into a control body to build heat and exergy balance models.Based on the models,the heat and exergy balance equations are established.When the error is as small as possible,some empirical or semi-empirical formulas are used to solve the equations.Finally,the calculation results are analyzed,the main conclusions are as follows:1)Under the selected working conditions,the heat carried by the cooling water occupies most of the heat generated by the engine.The proportion of the heat taken by the exhaust and the effective work is approximately the same,and the uncounted loss is the least.Due to the different physical and chemical properties of hydrogen and gasoline,with the increase of mixing ratio,thechange trend of heat proportion of each part in GDI model and HDI model is basically opposite.2)The engine speed has a great influence on heat ratio of exhaust and cooling water,but the effective thermal efficiency is insensitive to the change of engine speed.With the increase of engine speed,the change trend of heat proportion of cooling water in GDI mode is different from that in HDI mode.The influence of load on the two modes is identical.Load plays a dominant role in energy distribution,and the effect of fuel differences is masked.3)Generally speaking,with the increase of excess air coefficient,the change trends of the two modes are basically the same: the break power ratio is decreasing,the exhaust heat ratio is decreasing,but the heat ratio of cooling water and the uncounted loss are increasing gradually.4)Under the same working conditions,the results of the first and second laws of thermodynamics are quite different.In heat balance analysis,the energy proportion of cooling water is the largest,while in the exergy balance analysis,the energy proportion of cooling water is the least,and the exergy destruction proportion accounts for more than half of the total energy.5)In GDI mode,the exhaust exergy ratio increases with the increase of mixing ratio,the break power ratio decreases,and the cooling water exergy and exergy destruction ratios are not sensitive to the change of mixing ratio.In terms of the trend,the results of exergy analysis and heat analysis are roughly the same.There is little numerical difference between HDI model and GDI model,but the trends of exergy change are not the same.In HDI mode,the difference between heat balance and exergy balance is that the change trend of exhaust ratio with mixing ratio is different.6)Under GDI mode,the exhaust exergy ratio increases with the increase of engine speed,the exergy ratio of cooling water decreases,and the break power ratio is not sensitive to the change of engine speed,and the ratio of exergy destruction decreases.In HDI mode,except for cooling water,the other three trends are basically consistent with GDI mode.The change trends of exergy balance with load in the two modes are basically the same: as the load increases,the exergy proportion of exhaust gradually increases,the exergy proportion of cooling water decreases,the brake power ratio increases obviously,and the proportion of exergy destruction is greatly reduced.7)In exergy analysis,the change trends of brake power ratio with excess air coefficient inGDI and HDI modes are basically the same as those of heat analysis,but a slight difference in value due to the calculation methods.Compared with the results of heat analysis,the decrease of exhaust exergy ratio is more obvious due to the decrease in energy quantity and quality.The exergy proportion of cooling water decreases accordingly,which is contrary to the results of heat analysis.The two modes have the same trend of exergy destruction,showing a gradual upward trend.