Secondary injection of gases into a supersonic flow

The How field around the injection port for secondary injection of a gas nor:mal to a super-sonic stream has been studied in a series of wind-tunnel experiments. The experiD1ents were conducted at freestream Mach numbers of 1.38 to 4.54. Gaseous nitrogen, argon, and helium were used as injectants. New information concerning pressure fields, concentration fields, and shock shapes was obtained. A scale pal'ameter has been calculated, based on a simple, inviscid model of the How field. This scale parameter gives a good general correlation of the data. Use of this scale parameter allows prediction of a simple scaling law for the side forces generated by secondary injection. This side-force scaling law is in approximate agree-ment with existing rocket motor test results. NOlllenclature Ai injector area c discharge coefficient Cp pressure coefficient, {(P- p co)!tp",v co)2) d hole diameter F i force on body surface in i direction Fi thrust of a sonic injectant jet F p total axial thrust F 3 total side thrust h penetration height KA mass fraction of argon K He mass fraction of helium M i Mach number m mass flow rate mLi molecular weight of ith species P static pressure Po stagnation pressure Ri gas constant for species i Re L Reynolds number based on distance between leading edge of plate and injector centerline T static temperature To stagnation temperature V velocity x, y, z = coordinate axes, see Fig. 1 "Ii specific heat ratio f1F F.- Fi dimensionless pressure integral, defined in Eq. (7)