Parametric study and scaling of Mach 1.5 jet manipulation using steady fluidic injection

Abstract

We present the experimental investigation conducted to study the mixing characteristics of a Mach 1.5 jet manipulation using steady fluidic injection. Two important parameters are investigated, namely, the number of injectors, N, and the mass flow rate ratio of the injector jet to the main jet, Cm, along with the expansion ratio of the main jet, pe/pa, where pe and pa are the nozzle exit and atmospheric pressures, respectively. The jet mixing quantified as a measure of supersonic core length, Lc*, strongly depends on N, Cm, and pe/pa. Two distinct regions behind the jet manipulation are identified, and a physical reasoning based on pe/pa is presented using Pitot pressure measurements and Schlieren images. Empirical scaling analysis conducted on the experimental data for Lc* = f1(N, Cm, Ui/Uj, pe/pa) is reduced to Lc* = f2(MRNγMj2pe/pa), where MRN is the momentum ratio of the individual injector jet to the main jet, expressed as MRN = Cm,NUiUj and Cm,N = Cm/N. Here, U is the velocity, and suffixes “i” and “j” represent the injector and the main jet, respectively. Discussion conducted based on the scaling laws provides important insight into the optimal choice of injector diameter and the injection pressure ratio for practical utility.