超临界环境下的雾化过程中表面张力变化对射流稳定性的影响

Effects of Change in Surface Tension on Jet Stabilities in Atomization Process under Supercritical Environments

通过考虑由于气液界面上存在传热过程而导致的表面张力随空间分布的变化规律,并将此影响耦合加入线性稳定性理论中,研究燃油射流在进入跨临界环境后的稳定性及破碎行为.结果表明,随温度的增加,表面张力减小的梯度逐渐增大,并非线性分布;当气液界面温度接近临界点时,表面张力快速衰减为零;考虑传热效应和表面张力变化时,最不稳定波的增长率随波的发展是变化的.分析结果将有助于理解跨临界环境下射流破碎的机理,进一步扩展现有雾化模型在实际工况下的适用性.

Linear theory model has been applied for the investigation on the instability and breakup of fuel spray insupercritical or subcritical environment since it has considered the spatial variation of surface tension at the liquidgasinterface.The spatial variation of surface tension is obtained from the states of real-fluid thermodynamics thatis upon both surface tension and transient heat-transfer between the surrounding gas and the liquid column,viawhich the classical interface breakup theory and the effects of the real fluid thermodynamic state are coupled.Asthe results show,the gradient of the surface tension gets larger along with the increase of temperature in a nonlineardistribution.When the temperature at the gas-liquid interface is close to critical point,the surface tensionrapidly reduces to zero.When the heat transfer effect and the surface tension changes are taken intoconsideration,the growth rate of the dominant wave is a changing value.Such an analysis method could provide agreat help to the understanding of fuel spray breakup mechanisms under supercritical or subcritical conditions,consequently a significant guide to the understanding of actual operation conditions in advanced diesel engines.