46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit AIAA-2010-6846 25-28 July 2010, Nashville, TN 1 Numerical Simulation of Graphite Nozzle Erosion with Parametric Analysis Ragini Acharya 1 and Kenneth K. Kuo 2 Dept. of Mechanical and Nuclear Engineering, The Pennsylvania State Univ., University Park, PA 16802 Nozzle throat erosion is a major problem for solid rocket motors since it causes the degradation in the propulsive performance of solid rocket motors. The AP/HTPB composite propellants used in the rocket motors generate high concentrations of oxidizing species such as H 2 O, OH, and CO 2 in the combustion products at temperatures ranging from 2,700 to 3,200 K for non-metalized propellants. Earlier, the authors utilized a comprehensive numerical program called graphite nozzle erosion minimization code for prediction of graphite nozzle throat erosion rates as a function of pressure and propellant composition. From these studies, it was established that various parameters affect the nozzle thermo- chemical erosion rate including oxidizing species concentrations, flame temperature, and operating pressure. In addition, the thermal properties of graphite could also affect the nozzle throat erosion rate since these are directly related to the surface temperature at the nozzle throat. In order to assess the relative importance of these parameters in terms of their impact on the nozzle throat erosion rate, a parametric analysis was performed in this study. Each of these parameters was systematically varied while keeping all the remaining parameters constant. Based upon this research, it is concluded that flame temperature can affect the thermochemical erosion rate most, followed by chamber pressure and major oxidizing species concentrations. The mechanisms associated with the influence of these parameters are explored and described. A comparison of predicted results with the available experimental data shows match within 20%. The parametric analysis performed in this research provides an in-depth understanding of the thermochemical erosion process and the controlling steps in the nozzle erosion phenomena. Nomenclature Symbols Description A s,j Pre-exponential factor in the Arrhenius reaction rate expression for j th reaction C Thermal capacity C p Specific heat at constant pressure C * Characteristic velocity of a rocket E a,s,j Activation energy in the Arrhenius reaction rate expression for j th reaction D Nozzle diameter f Friction factor h c Convective heat-transfer coefficient H Total enthalpy of the mixture ( ) 2 2 1 1 2 N i i i Yh u v = + + ∑ k Specific reaction rate constant M Mach number Mw Molecular weight e m  Diffusion-limited mass erosion rate = , ced r ρ  N Number of gas-phase oxidizing species at the solid-gas interface Ns Number of major gas-phase species in the combustion products Pr Prandtl number p c Average combustor pressure 1 Post Doctoral Research Associate, Dept. of Mechanical & Nuclear Engineering, 134 Research Building East, Member AIAA. 2 Distinguished Professor, Dept. of Mechanical & Nuclear Engineering, 140 Research Building East, Fellow AIAA. 46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit 25 - 28 July 2010, Nashville, TN AIAA 2010-6846 Copyright © 2010 by Ragini Acharya and Kenneth K. Kuo. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.