Influence of injection angle on liquid jet in crossflow

Abstract

The influence of changing the injection angle of a liquid jet injected into airstream in crossflow was investigated. The injection angles from 90 to 30 degrees were considered. Based on liquid velocity and air speed, liquid and gas Weber numbers from 8 to 600 and 0.2 to 27 were considered, respectively. Many flow parameters such as: Rayleigh-Taylor wavelengths, liquid jet trajectories, breakup lengths and penetration lengths by means of high-speed photography and shadowgraph technique were measured and reported. Based on the relative importance of the aerodynamic forces of the crossflow to the liquid momentum and surface tension forces different breakup regimes occurred. Using gas Weber number, the following liquid jet breakup regimes: column breakup, arc breakup, bag breakup and multimode breakup were observed at various injection angles. It was found that at lower injection angles the required gas Weber number to transition between regimes was slightly increased.At lower gas Weber number flows, increasing the injection angle caused the liquid jet to penetrate farther into the airstream and this process was gradual. However, at higher gas Weber number flows, there was a bifurcation in behavior: At the lower injection angles, the behavior was the same, but at the higher injection angles, the penetration behavior reversed and the penetration of liquid jet into airstream decreased as the injection angle was increased. We believe this phenomenon was due to switching of the breakup mechanism from Rayleigh-Taylor instability to shear breakup mechanisms at higher injection angles.Theoretical models for prediction of liquid jet trajectory and its breakup point taking the effect of injection angle into account were developed and presented. The models’ predictions were compared with our measurements and other published data resulting in good agreements.