Numerical investigation on fuel injection into a multicomponent gaseous environment under trans/supercritical condition

Abstract

Large eddy simulation is performed on trans/supercritical fuel injection into a multispecies supercritical environment, where the pressure and temperature exceed the fuel critical point. The real equation of state Peng-Robinson is employed and thermodynamic nonideality and anomalies in transport properties of the fluid mixture are considered. The dissolution of the surrounding gas has an important influence on the thermodynamic and transport properties. Much larger density-gradients are formed in the transcritical case, which has an effect of stabilizing the flow field and inhibiting the development of unstable waves. In contrary, in the supercritical case eddies tend to grow up and roll into a series of circular vortices, and the injected n-heptane tends to mix with the surrounding gas leading to a shorter penetration. In addition, conditional averages performance indicate that the critical parameters of mixture are closer to that those of n-heptane. In the transcritical injection, a dense “liquid core” region still exists, while this phenomenon does not appear in the supercritical case. A mixing layer thickness based on the density gradient is suggested to quantify the mixing characteristics. In the supercritical injection, a significantly larger mixing layer thickness is predicted than the transcritical injection condition.