Experimental Study Of Jet-to-Jet Interaction For GDI Spray Based On Visualization

Environmental pollution is becoming more and more serious,petroleum energy is becoming more and more scarce,and the emission regulations are becoming more and more strict,all of which put forward higher requirements for the gasoline direct injection engine(GDI).For a multi-hole GDI injector,spray jets interact with each other and converge to form spray collapses.The spray collapse will change the spatial distribution in the cylinder,affect the formation quality of the mixture,and then affect the combustion and emission of the engine.Therefore,it is necessary to conduct in-depth research on the spray characteristics of the multi-hole GDI injector.This dissertation studies the Jet-to-Jet interaction for GDI spray in two aspects,i.e.the influencing factors of the Jet-to-Jet interaction,the mechanism of the Jet-to-Jet interaction.This dissertation analyzes the influence of environmental factors on the spray characteristics,and analyzes the interaction mechanism of the Jet-to-Jet interaction based on the spray characteristics.The effects of fuel temperature,ambient pressure and ambient gas density on spray width and spray penetration distance were studied under non-flash-boiling conditions.The results show that the change of fuel temperature has little effect on spray width and spray penetration distance.The increase of ambient pressure and ambient gas density will enhance the Jet-to-Jet interaction and make the spray collapse heavier.Meanwhile,the increase of ambient pressure and ambient gas density will increase the resistance to spray development and decrease the penetration distance.Under non-flash-boiling conditions,spray collapse can be explained by Jet-induced interaction,and the key factor affecting Jet-induced interaction is the ambient gas density.The effects of fuel temperature,ambient pressure and ambient gas density on spray width and spray penetration distance were studied under flash-boiling conditions,the interaction mechanism of the Jet-to-Jet interaction was explored,and the contribution of Jetinduced interaction was summarized.The results show that increasing the fuel temperature and reducing the ambient pressure will make the fuel overheated,and the spray width will be increased due to the explosion of bubbles near the nozzle.With the increase of fuel temperature or the decrease of ambient pressure,the spray width decreases and the spray collapse increases.When the superheated degree of the fuel is the same,the spray collapse increases with the increase of the ambient gas density.When the ambient gas is He with low ambient pressure,the ambient gas density is very low,and the multi-hole GDI spray still collapses into a single jet.This indicates that Jet-induced interaction is not the essential cause of spray collapse under flash-boiling condition,but Jet-induced interaction has a positive effect on spray collapse.