Influence Of Fuel Temperature On Gasoline Spray Characteristics

The effect of fuel atomization is very important to improve the thermal efficiency and emission performance of gasoline direct injection engine.Injecting high even ultra-high-temperature fuel into the cylinder for combustion has become a research hotspot gradually,but the relevant fuel atomization mechanism is still in the blank.Therefore,this paper research the influence of fuel temperature,injection pressure and number of nozzle holes on the spray characteristics systematically.Based on the principle of Mie scattering,a test system for ultra-high temperature pure liquid gasoline spray was built,based on the schlieren principle,a test system for ultra-high temperature gas-liquid gasoline spray was built,and the development characteristics of pure liquid and gas-liquid gasoline spray were systematically explored.The influence of fuel temperature on the phase transition characteristics of gasoline spray was analyzed by the comparison between pure liquid and gas-liquid spray images.The droplet size of spray was measured by phase Doppler test equipment under different fuel temperature and injection pressure.The result shows that with the increase of fuel temperature,the spray morphology of multi-hole pure liquid gasoline changing from plump flocs to collapsing to color fading.The penetration decrease first and then increase with the increase of fuel temperature.When the fuel temperature is above 170 C,the fluctuation ranges of spray cone angle increase.The overall change trend of the spray expansion angle is basically unchanged in the low temperature area,and increase rapidly through the middle temperature zone.The cone angle of single hole pure liquid gasoline spray increase with the increase of fuel temperature firstly,and the curve of spray cone angle decrease gradually.However,the spray cone angle decrease with the increase of fuel temperature at high injection pressure,which is slower than that of low injection pressure.The Mach Disk phenomenon is observed in the nearfield images of single hole spray.The dimensionless Mach Disk size increase with the increase of fuel temperature overall.The dimensionless Mach Disk position is independent of fuel temperature and affected only by injection pressure.The multi-hole gas-liquid gasoline spray also have plume floc structure and collapse stage in the middle and low temperature region,and the image gradually become transparent in the high temperature zone,and the schlieren changes caused by spray in the ultra-high temperature region are further reduced.In the ultra-high temperature region,the penetration,cone angle and expansion angle keep the fluctuating trend.The development of dimensionless Mach Disk parameters is consistent with that of pure liquid spray.The area and penetration of gas-liquid fuel spray are larger than that of pure liquid fuel spray.With the increase of fuel temperature,the change rate of spray area of gas-liquid fuel is increasing.The droplet size of spray decrease with the increase of fuel temperature,and influence of fuel temperature is much greater than injection pressure.Large droplets appeared at the beginning of the development of fuel spray at 25 C,but there is no large droplet in high temperature fuel spray.