Numerical Simulation of Liquid Sheet Deformation Caused by Air Flow

Abstract

A liquid-fuel sheet injected into the combustor of gas turbine engines is deformed and atomized as a result of the complex interactions between the liquid and air flows. However, the effects of the fluid properties and velocities of the gas and liquid on liquid sheet oscillation have not been clarified yet. In this paper, we performed two-dimensional (2-D) numerical simulations of an oscillating liquid sheet using a volume tracking method to investigate the effects of densities, velocities, viscosities and momentums of the gas and liquid phases on the growth rate and wavelength of the liquid sheet oscillation. As a result, we obtained the following conclusions. The oscillation of a liquid sheet is suppressed by the atomizer lip, which forms a wake in its downstream. The gas velocity gradient at the gas-liquid interface is a dominant factor in the growth of liquid sheet oscillation, which depends not mainly on gas velocity but on liquid velocity due to the lip. Gas and liquid viscous forces slightly reduce liquid sheet oscillation. The wavelength of the oscillation is in inverse proportion to the square root of the momentum flux ratio.

Longitudinal oscillation of a liquid sheet by parallel air flows

“…However, the effects of fluid properties of gas and liquid on λ Lon were not investigated systematically in the previous studies, and we cannot understand the reason why the dominant length scale is D L within various dominant length scales including D Lip , δ G and δ L . Based on the numerical simulations with various V G , V L , ρ L , ρ G , µ L and µ G with constant D L and D Lip , the present authors [12] proposed the following correlation on λ Lon under the limited condition of constant D L and D Lip :…”

“…These correlations were proposed through the theoretical, experimental, or numerical studies under various operating conditions and fuel injector designs [2,[11][12][13][14].…”

“…Based on the inviscid linear instability analysis of a liquid sheet, Squire [2] takes surface tension effect into account in his correlation of λ Lon . In contrast, surface tension effect on λ Lon was not considered under the high Weber number or the thick boundary layer layer conditions [11,12,14].…”

“…The effects of fluid properties of gas and liquid and injector geometries as well as gas and liquid velocities and ambient pressures on f Lon and λ Lon have been discussed [5,6,11,12]. Lozano et al [11] investigated the effects of liquid and air thicknesses on λ Lon of the planar liquid sheet, and proposed a correlation based on their experimental result.…”

“…Lozano et al [11] investigated the effects of liquid and air thicknesses on λ Lon of the planar liquid sheet, and proposed a correlation based on their experimental result. The present authors [12] investigated the effects of fluid properties and velocities of gas and liquid on the oscillating characteristics of the liquid sheet by two-dimensional numerical simulations. We clarified that the oscillation of a liquid sheet is suppressed by the atomizer lip which forms a wake in its downstream, and proposed a correlation on λ Lon .…”