The flow field around the injection port for secondary injection of a gas normal to a supersonic stream has been studied in a series of wind-tunnel experiments. The experiments 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 parameter has been calculated, based on a
simple, inviscid model of the flow 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 agreement with existing rocket motor test results.

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Secondary injection of gases into a supersonic flow

This paper is concerned with the analytical prediction of the behavior of gaseous jets issuing transversely through a surface into an otherwise uniform stream. Primary emphasis is placed upon the case of a supersonic main stream. The work falls into three major areas. First, the use of a "solid body" drag model to describe the jet trajectory is re-examined, extended to include a supersonic main stream, and modified to alleviate the most untenable of the assumptions common to previous work. With this, good agreement between experiment and theoretical prediction is achieved. Second, the important general case of "underexpande d" injection is treated. A new model is adopted to permit the analysis of this extremely complicated flow problem. Briefly stated, an analogy is made between this and the simpler and well-understood situation of an underexpanded jet issuing into a quiescent medium. The key to this model is the notion of an "effective back pressure." Lastly, the analysis developed is applied to a configuration study of a combustion chamber for a hypersonic ramjet with supersonic combustion on a representative flight trajectory.

Penetration of gaseous jets injected into a supersonic stream.

A Unified Analysis of Gaseous Jet Penetration

Structure of highly underexpanded transverse jets in a supersonic stream.

Analysis of the fluid mechanics of secondary injection for thrust vector control

Data are presented on side forces generated by secondary gas injection in a 15° conical rocket exhaust nozzle. The side force was measured directly with a force transducer and the data examined in terms of an amplification factor I8/I8*9 where Is is the measured effective specific impulse of injectant, and Is* is the specific impulse of injectant for sonic flow into a vacuum. Injection was normal to the axis of the nozzle through a single circular orifice at a fixed point in the diverging portion of the nozzle. A variety of ambient temperature gaseous injectants (H2, He, He + Ar, N2, CO2, and Ar) and orifice diameters were carefully studied. Injectant flow rate was varied for each configuration. The main propellant was hot gas (catalytically decomposed 90% H2O2), and motor conditions were held essentially constant. Aj = A\ = CD = FN = F =

Secondary gas injection in a conical rocket nozzle

: Data are presented on interference forces resulting when a gas at ambient temperature is laterally injected through a single circular orifice in the conical portion of a rocket nozzle into hot supersonic propellent gases. Variables examined are injectant orifice size and associated pressure ratio change and effect of injectant molecular weight and specific heat ratio. Other parameters remain essentially constant during these tests. Simple theoretical arguments can predict relative effects of intrinsic injectant properties, but pressure ratio effects are not adequately described. Effectiveness of secondary injection depends on injectant orifice size, which was not treated in any theoretical modes.

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Secondary gas injection in a conical rocket nozzle. 1. effect of orifice diameter and molecular weight in injectant

: Data are presented on side forces generated by (1) lateral injection of sonic gas jets and (2) probe immersion into constant area supersonic duct flow (M = 1.9 or 2.9) provided by a rocket motor exhaust. For gas injection studies, a variety of cold injectants, injectant orifice sizes and 'tailpipe' lengths were studied. Data also are reported for inert and potentially reactive hot gas injection. Side force and probe drag were measured for various 'tailpipe' lengths and probe immersion depths and diameters. A simple analytical model is introduced which is adaptable to probe thrust vector control (TVC).

A. R. Stone

Papers

Secondary gas injection in a conical rocket nozzle

Secondary gas injection in a conical rocket nozzle. 1. effect of orifice diameter and molecular weight in injectant

Basic tvc experiments with gas injection and probes