Validation of an Aerothermochemical Model for Graphite Nozzle Recession and Heat-Transfer Processes

Abstract

Abstract-An aerothermochemical model for graphite nozzle recession and heat-transfer processes in solid-propellant rocket motors has been developed. The model considers the turbulent boundary-layer flow in the nozzle, heterogeneous reactions at the nozzle surface, and transient heat-conduction processes in the nozzle material. Mass transfer across the highly-accelerated turbulent boundary layer shows only a weak dependence on the Schmidt number of the diffusing species. Both frozen and chemical equilibrium boundary-layer assumptions were considered. H₂O is found to be the dominant oxidizing species, with CO₂ being of secondary importance. Concentration profiles of H₂O across the boundary layer are not significantly affected by gas-phase reactions, implying that the graphite recession process is relatively independent of gas-phase reactions. The model has been verified with experimental data. Good agreement has been obtained for both recession and temperature measurements.