Scale effect of gas injection into a supersonic crossflow

Abstract

This study focuses on the scale effect of transverse gas fuel injected into a Ma=2.95 supersonic flow. NPLS (Nanoparticle-based Planar Laser Scattering) and oil flow techniques were employed to obtain flow structures and jet penetration, while the RANS (Reynolds-averaged Navier-Stokes) model was utilized to investigate fuel mixing characteristics. In order to get the scale effect law, the diameters of jet orifice were chosen as D=2 mm and D=4 mm, and the jet-to-crossflow dynamic pressure flux ratio (J) were set as 2.3, 5.5, and 7.7. The jet penetration boundary could be extracted from NPLS images. By analyzing plenty of NPLS images, a corrected fitting formula was given, which could reflect the scale effect law of jet penetration. The oil flow experiments compared the shapes and the size of the V-shape recirculation zone of different scales. Results showed that the size of the recirculation zone amplifies proportionally with the diameter of the orifice growth. The RANS numerical simulations were conducted to study the mixing characteristics, and the detailed fuel mass fraction concentration and mixing efficiency analysis were given. It is concluded that the turbulent boundary layer plays an important role in the scale effect of the jet penetration and mixing characteristics, especially for the low jet-to-crossflow dynamic pressure flux ratio (J).