Effect of Component Proportions on Phase Change Induced Shock Wave Width in Flash Boiling Jets
The under-expansion of flash boiling jets and the ensuing shock interaction are the main reasons for spray collapse of the gasoline direct injection(GDI)engine,but lack of investigations on the effects of component proportions on shock waves in flash boiling jets.High-speed microscopic Schlieren photography was used to investigate the influence of varying ethanol/n-hexane blending ratios on shock width.Tests were carried out in a constant volume vessel with ambient pressures(Pamb)from 10 to 200 kPa,and fuel injection temperatures(Tinj)from 30 to 150℃.For all studied liquids,increasing Tinj and/or decreasing Pamb causes an increase in shock width.For given Tinj and Pamb,shock width varies non-monotonically with increasing ethanol blending ratio,mainly caused by the non-monotonical change in △G(Gibbs energy difference during phase change)of the fluids.Further analysis to corelate shock width with △G showed that shock width has a strong linear correlation with △G·P-0.5amb,indicating that phase change and ambient resistance contribute to the radial expansion of shock waves in flash boiling jets.
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