Analysis of self-cooling with infiltrated porous tungsten composites

Abstract

With the advent of solid rocket engines utilizing high-energy aluminized propellants, the need for a noneroding nozzle-throat insert material has become acute. The wall temperatures attained at the throat are above even the maximum practical operating temperature of tungsten. However, by infiltrating a porous tungsten insert with a second material, which is subject to gasification by boiling, sublimation, or decomposition, it is possible to reduce the wall temperature to a tolerable value. This paper presents an analysis of the behavior of this so-called self-cooling process with infiltrated porous tungsten composites. A one-dimensional, finite thickness, flat plate model is specified. As gasification of the infiltrant proceeds, the gaseous/liquid or solid infiltrant interface recedes from the surface. The transient partial differential equations describing the model consist of the continuity, momentum, and energy relations. The effect of transpiration is included. The equations are solved by a numerical finite-difference solution that was programed for the IBM 7094. Typical results of the computer program are presented for a number of organic and inorganic infiltrants at typical high-pressure solid rocket nozzle-throat conditions to illustrate the effects of certain variables such as porosity and permeability of the porous tungsten.