Multiphase Modeling of Water Injection on Flame Deflector

Abstract

This paper describes the use of an Eulerian Dispersed Phase (EDP) model to simulate the water injected from the flame deflector and its interaction with supersonic rocket exhaust from a proposed Space Launch System (SLS) vehicle. The Eulerian formulation, as part of the multi-phase framework, is described. The simulations show that water cooling is only effective over the region under the liquid engines. Likewise, the water injection provides only minor effects over the surface area under the solid engines.Nomenclature constant pressure specific heat of fluid , J / kg-K constant pressure specific heat of particle species i, J / kg-K average particle diameter of particle species i, m total internal energy (thermal and kinetic energy) of particle species i, J /kg Nusselt equation correction factor of particle species i buoyancy force on particle species i, N interphase drag force on particle species i, N lift force on particle species i, N pressure gradient force on particle species i, N turbulent dispersion force on particle species i, N virtual mass force on particle species i, N Latent heat of evaporation of species i, J /kg rate of production of mass for particle species i, kg/ m 3 -s number density of particle species i, m- I. Introduct ionSince the retirement of the Space Shuttle, NASA has been developing a new heavy-lift capability, the Space Launch System (SLS). In conjunction with this development, NASA is re-assessing their launch site capabilities. One key component of particular interest is the Main Flame Deflector (MFD). The main purpose of the MFD is to minimize the plume impingement effects on the launch facility and to minimize the induced environmental effects on the vehicle. The MFD must be protected from harsh thermal environments generated by the plume impingement.Currently, the MFD is kept cool by water sprays from the nozzles mounted on the apex of the deflector (Figures 1). The MFD water is one of the many water suppression systems employed at the launch complex. There are also water nozzles mounted around the exhaust hole to reduce the ignition overpressures and water rainbirds mounted on the launch deck to suppress the launch acoustics. This study focuses only on the MFD water nozzles, which can deliver water flow rates up to 300,000 gallons per minute (gpm) on both sides of the deflectors (Figure 2).Recent advances in computational fluid dynamics (CFD) technique and computing resources have provided the necessary predictive capabilities during the MFD redesign. 1 • 2 However, these predictions often neglect multi-phase modeling to avoid model complexity and to reserve conservatism associated with uncooled or dry rocket plumes. Since the conservative results show severe thermal environments, it is prudent to know the effect of the water suppression system on the MFD in order to ensure that the MFD is not overdesigned.The interaction of water sprays with supersonic flow is a complex phenomenon as it involves condensation, evaporation, diffusion, and dispersion processes. In this paper, the...

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