Mixing Analysis of Like Doublet Injectors in High Pressure Environments for Gelled Propellant Simulants

Abstract

Effect of ambient pressure on the mixing efficiency of impinging doublets is experimentally investigated for similar and dissimilar orifice diameter impinging jets with non-gelled and gelled propellant simulants. For similar orifice diameter impingement, the ambient pressure increase above atmospheric pressure enhances mixing for both gelled and non-gelled fluid. However, the mixing efficiencies stop increasing at and remain constant above a certain ambient pressure. Gelled simulant generally results in poorer mixing than the non-gelled simulant, suggesting the momentum carried by jets and pre-impingement jet conditions are the determining factor in mixing efficiency. For dissimilar orifice-diameter impingement cases, the mixing is generally constant over all ambient pressures. The equal jet velocity cases (momentum ratio = 0.5) produce better mixing than equal momentum ratio cases (momentum ratio = 1.0) or equal jet volumetric flow rate cases (momentum ratio = 2.0). The equal jet volumetric flow rate cases (momentum ratio = 2.0) results in worst mixing, regardless of ambient pressure and jet velocity for the range of pressures and velocities tested. For some optimized operating conditions, the dissimilar orifice-diameter impingement case can produce better mixing than the similar orifice diameter impingement case.