Unified Analysis of Internal Flowfield in an Integrated Rocket Ramjet Engine. I: Transition from Rocket Booster to Ramjet Sustainer

Abstract

A comprehensive numerical analysis was conducted to study the internal flow development in an integrated rocket-ramjet (IRR) propulsion system. The study consists of two parts: transition from the rocket booster to the ramjet sustainer and combustion dynamics during ramjet operation. The physical model of concern includes the entire IRR flow path, extending from the leading edge of the inlet center body through the exhaust nozzle. The theoretical formulation is based on the Farve-averaged conservation equations of mass, momentum, energy, and species concentration in axisymmetric coordinates and accommodates finite-rate chemical kinetics and variable thermophysical properties. Turbulence closure is achieved using a low-Reynolds-number k-ɛ two-equation model. The governing equations are solved numerically by means of a finite-volume preconditioned flux-differencing scheme capable of treating a chemically reacting flow over a wide range of Mach numbers. Various important physiochemical processes involved in the transition from the booster to the sustainer phase are investigated systemically. Emphasis is placed on the flow interactions between the inlet diffuser and combustor. The effects of operation timing on the flow evolution, fuel spread, ignition, and flame development are studied.

A Numerical Analysis of Supersonic Intake Buzz in an Axisymmetric Ramjet Engine

“…Turbulent combustion is treated using a hybrid kinetic/eddy dissipation model [22]. For simulation of premixed condition, fuel is introduced into the flow path computationally by adding a source term at each cell on the fuel injector plane with a pre specified distribution, mimicking the fuel injection into the air stream from a chocked orifice on the wall [19]. Fuel injection plane locates about 0.23 m upstream of the leading edge of flame holders.…”

“…Hsieh and Yang [18] developed an integrated numerical framework for treating the flow and flame evolution in the entire flow path of an axisymmetric engine. Sung and Yang [19,20] later examined the ignition transient process and the key mechanisms for driving and sustaining the inlet shock and combustion oscillations. Low-frequency longitudinal pressure oscillations were observed due to the interactions between the inlet and combustor flow dynamics.…”

Unified Analysis of Internal Flowfield in an Integrated Rocket Ramjet Engine. II: Ramjet Sustainer

“…The present work extends from the companion paper Sung and Yang (2014), which deals with the transition from the rocket booster to the ramjet sustainer of an integrated rocket ramjet (IRR) engine to treat the internal flow evolution in the ramjet sustainer. Emphasis is placed on the interactions between the inlet and combustor dynamics, as well as the overall engine performance.…”

“…The physical domain of concern includes the entire engine flowpath, from the freestream in front of the inlet, through the combustor, to the exit of the exhaust nozzle. The flowfield obtained from Sung and Yang (2014) is used as the initial condition for the present analysis, so that the complete operation history of the IRR engine can be obtained.…”

“…The upstreamrunning wave then causes the shock wave in the inlet diffuser to oscillate periodically. This process, in turn, produces disturbances traveling or convecting downstream in the form of an acoustic or entropy wave, which subsequently reinforces the combustion oscillation in the flame zone Sung and Yang 2014). A feedback loop is thus formed for driving and sustaining flow oscillations in the engine.…”