Influence of orifice thickness on the flow field of co-flow jets

Abstract

The present study analyses the numerical simulation results of subsonic flow through co-flow orifices. Analysis is done on the effects of modifying orifice thickness on the co-flow jet characteristics. The combined frontal area of the co-flow jet and central jet is maintained constant (20 mm2). The primary orifice diameter (D) is kept as 3mm and the orifice thickness, i.e the co-flow jet is formed as four segments of a concentric circle around the core jet, and the edge distance between them ranges from 0.16D to 0.5D. The 0.16D co-flow is shown to lengthen the potential core of the main jet at nozzle pressure ratios of 1.2, 1.4, 1.6, and 1.8, but the 0.33D co-flow and the 0.5D co-flow shorten the potential core length, enhancing mixing. The present study analyses the Mach numbers that correspond to the Nozzle Pressure ratios of 1.2, 1.4, 1.6, and 1.8, which are 0.517, 0.71, 0.84, and 0.96, respectively. The 0.5D annular gap is found to be more effective which boosts primary jet mixing.