Aerodynamic Experiment on an Ejector-Jet

Abstract

Characteristics of an ejector-jet were investigated experimentally. Evaluation of a new, one-dimensional model of suction performance under the aerodynamic choking condition and observation of mixing conditions through the pseudo-shock were primary subjects of study. Supersonic primary rocket exhaust was simulated by air, and secondary airflow was simulated by nitrogen. Parameters were the ratio of the total pressure of the secondary flow to that of the primary flow, the ratio of the entrance area of the secondary flow to that of the primary flow, and the Mach number of the primary flow. A throttling valve downstream of the mixing region simulated subsonic combustion and subsequent choking, and the throttling created a pseudo-shock ahead of the valve. The suction performance increased with increased total pressure of the secondary flow, the increase of the Mach number of the primary flow, or the increase of the area of the secondary flow. The calculated results on the suction performance agreed well with these measured values. When the gases became subsonic due to throttling, the primary and secondary fluids mixed well through the pseudo-shock and became almost uniform ahead of the downstream choking position. The mixing progressed quickly in the pseudo-shock. Nomenclature A = cross section H = height M = Mach number ˙ m = mass flow rate P = pressure Pt = total pressure r = ratio of the mass flow rate of the secondary flow to that of the primary flow T = temperature Tt = total temperature u =v elocity x = streamwise coordinate from the entrance of the test section y =v ertical coordinate from the primary-flow sidewall z = spanwise coordinate from the center plane of the test section γ = ratio of specific heats ρ = density ω = mass fraction of the secondary flow