Structure Characteristic Of Transverse Liquid Jet In Supersonic Crossflow

The structure and spatial distribution characteristics of transverse liquid jet injection into mach 2 cold supersonic crossflow were investigated experimentally. In the present research, the optical measurements such as high speed photography, shadowgraphy, Particle Image Velocimetry(PIV), Malvern and Phase Doppler Particle Analyzer(PDA) were employed to obtain the structure characteristics of the jet and the supersonic crossflow.Different penetration curves in the same test condition were obtained and compared using five optical measurements mentioned above. The corresponding image process methods were introduced as well. It can be obtained that the penetration gained by PIV and Malvern are similar to each other, but they are about 90 percent as high as PDA results. PIV methodology can be used to capture the boundary and transient structure of the liquid jet at the same time. The velocity and diameter of the droplets were measure by Malvern and PDA in the current research. Experimental results show that droplets with high speed and large size are mainly near the boundary of the jet.The effects of two factors, more exactly the pressure drop of the liquid jet and the diameter of the injector, on the penetration height and lateral extension were investigated by PIV and high speed photography in detail. The experimental results indicate that with the pressure drop getting lager, the penetration and lateral extension of the jet increase. At the same time, enlarging the diameter of injector would increase the penetration height and broaden the lateral extension of the jet. Besides, the diameter of the injector has more obvious impact on the penetration and lateral extension. The experiential correlations of penetration height and lateral extension were proposed with the injection ratio and orifice diameter based on the experimental data obtained.The instability of the liquid jet was investigated by high speed photography and there are two typical fluctuations in different areas of the liquid jet. One kind of small scale is generated from the exit of injector while the other of large scale is attributed to the breakup of liquid column. Large droplets with great difference in velocity will also make contribution to this phenomenon. These two kinds of fluctuation get stronger with the development of the liquid jet. In the upwind area of the jet, there is a weak interaction between the jet and the bow shock wave. With the development of the liquid jet(where x>7mm) the instability of liquid has less and less effect on the bow shock.