ID 47

Effect of Nozzle Geometry on Aerated-Liquid Injection in Supersonic Crossflow

 

Abstract:

The injection of liquid jets in supersonic crossflow is investigated experimentally motivated by their applications to fuel atomization in high-speed air-breathing propulsion systems. Near-field structures of pure- and aerated-liquid jets in supersonic crossflows (M = 2) are explored with inline digital holographic microscopy. The setup consists of two frequency-doubled Nd:YAG lasers and 29-Mpixel interline-transfer, charge-coupled device (CCD) camera, operating in double-exposure mode. Measurements, including penetration height and plume width, droplet SMD, and end of the liquid core, are obtained in the near injector region (x/d0 ≤ 50), where most of the droplets are not spherical and thus are not accessible for measurement techniques that rely upon the sphericity criterion. The use of droplet equivalent diameter for the quantification of ligament/droplet sizes provides a valid approach to characterize the spray structure in this region. The injectors tested include convergent-divergent nozzles with variable length/diameter ratio as well as injector intrusion. Different liquid flow rates, and gas-to-liquid ratio by mass (GLR) are used to compare the results of aerated liquid jets to pure liquid jets. The results are correlated with GLR, down-stream distance, x, and the rinjector geometrical parameters.