Numerical simulation of flight effect on the afterburning plume exhausting from a solid rocket motor
Creators: name:  ADRIEN LANGENAIS 
name:   JULIETTE AUBREE 
name:   PIERRE DOUBLET 
name:   STEPHANE LANGLOIS 
name:   CLAIRE LAVIGNE 
name:   VALERIE RIALLAND 
Publisher: name: Proceedings of the Aerospace Europe Conference - EUCASS - CEAS - 2023
Year: 2023
Subjects: SOLID ROCKET MOTOR
PLUME AFTERBURNING
FIRING EXPERIMENTS
CFD
COMBUSTION MODELLING

description: The effect of a supersonic surrounding flow on the afterburning plume exhausting from a nonaluminized solid propellant rocket motor is numerically investigated. The motor is placed in the center of an annular channel generating a Mach 1.5 co-flow. Simulations of both cases with and without the surrounding flow are performed using an axisymmetric Reynold-averaged Navier-Stokes approach. The afterburning process between ambient air and burnt propellant gases is represented by a kinetic scheme associated with a partially stirred reactor model and a local flame extinction model. The comparison with experimental measurements shows that only the extinction model allows to capture the flame lift-off behavior. I. Introduction Exhaust plumes from solid propellant rocket motors are the main contributors to heat fluxes on the afterbody and to vehicle infrared signatures [1], which are major concerns for the design of space launchers, missiles or warning systems. The afterburning process occurs when the hot fuel-rich burnt propellant gases containing H2 and CO mix with 02 from the cold ambient air. The flame generated by the combustion reaction then contributes to increase convective and radiative heat transfers. Accurately characterizing plume afterburning is a challenging problem because of the numerous complex physical processes affecting the flow. For example, the shock cell structure and other compressibility effects may impact the mixing layer and thermal properties of the supersonic jet, as well as external flow features, flow heterogeneity and turbulence inside the motor chamber, or flow interactions with walls and particles. The numerical simulation can provide a reliable prediction of these phenomena in realistic flight conditions, at reasonable cost, with a plume modeling based on a compressible Reynolds-averaged Navier-Stokes solver and adequate models for turbulence, finite rate chemistry and radiative transfer [2, 3]. This approach have thus been employed in past and recent numerical studies to assess the effects of altitude, body interactions [4, 51, flight or motor operating conditions [6, 7] on the plume. However, these works sometimes suffer from a lack of validation data for the afterburning flame characterization. The turbulence-chemistry interactions in the jet mixing layer are also neglected despite the possible influence on the afterburning. Calhoon et al. [8, 9] show for example that it could explain the abrupt afterburning shutdown observed during the flight of many systems, with important consequences on the heat fluxes and the plume signature. The present paper aims aims to numerically investigate the effect of a supersonic surrounding flow on an afterburning plume exhausting from a non-aluminized composite solid propellant rocket motor. The case under study is introduced in Section 2. It matches a ground experiment [10, 11] where a rocket motor was placed in the center of an annular channel generating a supersonic air co-flow in order to mimic flight effects. Instrumented firing tests were carried out with and without the surrounding flow around the motor exhaust plume, respectively labeled as dynamic and static cases [12]. Corresponding simulations are performed using the numerical procedure described in Section 3, relying on an axisymmetric Reynold-Averaged Navier-Stokes (RANS) approach. A special attention is paid to the combustion and turbulence-chemistry interactions modeling as recommended. The afterburning process is represented by a skeletal kinetic scheme [13] associated with a Partially Stirred Reactor (PaSR) combustion model [14, 15] and a local Copyright 2023 by ONERA. Posted online by the EU CASS association with permission.