Structures of Aerated-Liquid Jets in High-Speed Crossflows

Abstract

d0 = injector orifice diameter GLR = aerating gas-to-liquid mass ratio The structures of aerated-liquid jets injected into subsonic crossflows were studied experimentally. An aerated-liquid injector with a diameter of 0.5 mm was flush mounted on the bottom plate of a subsonic wind tunnel to provide normal injection. Freestream Mach numbers, M, of 0.2 and 0.3 were tested. Water at room temperature was used as the test injectant. Wide ranges of test conditions for jet-to-air momentum flux ratios, q0, and aeration levels, GLR, were tested. A phase Doppler particle analyzer (PDPA) was utilized to quantitatively measure droplet and spray plume properties. The obtained data was used to develop correlations for the properties of droplet and spray plume for aerated-liquid jets, using the least squares method. It was found that the atomization processes of a typical aerated-liquid jet are completed at a relatively short x/d0. The droplet size decreases as the GLR and M increase. The droplet velocity increases with GLR, x/d0, and M and has no significant dependence on q0. The cross-sectional area of the spray plume increases with GLR, q0, and x/d0 and decreases with M. As GLR increases, the increase in the cross-sectional area of spray plume, Aj, mainly comes from the increase in spray penetration height. The spray width, however, is fairly independent of GLR. The aspect ratio of the spray plume increases with GLR. It was also found that A70%/Aj and A30%/Aj of aerated-liquid jets increase with GLR and x/d0 and have values of 32.5 and 10.6, respectively. For the present study, the values of A70%/Aj and A30%/Aj for the pure-liquid jets are 29.3 and 8.5, respectively. h = spray penetration height L = nozzle passage length M = freestream Mach number Oh = Ohnesorge number, μL/(ρL(SMD) σ) Q = volumetric flow rate q0 = jet-to-freestream momentum flux ratio at GLR=0, ρLw0/ρ∞u∞ SMD = Sauter mean diameter, Σ di/Σ di, i for all droplets T = temperature u = velocity component in the x direction w = velocity component in the z direction; also spray width We = Weber number, ρL(SMD)(u∞-up)/σ x = distance in the freestream direction y = distance in the cross stream direction z = distance in the direction of liquid injection θ = jet injection angle