Coupling of transient thermal and mechanical stresses computations in graphite nozzle materials

In this work, a numerical simulation of the structural response of the graphite nozzle materials to the flow during the ignition transient of a solid rocket motor is considered. The measured pressure– time trace within the combustion chamber was used as an input parameter in the graphite-nozzle erosion minimization (GNEM) code to calculate gas-phase pressure, temperature, velocity, etc. in the graphite nozzle. The calculated pressure and convective heat flux from GNEM were applied as loading conditions in an associated thermo-structural model to obtain response of graphite nozzle materials to the transient pressure and thermal loading. The combined aero–thermo–structural response of the graphite rocket nozzle showed that the thermal stresses were significantly higher than the mechanical stresses. The radial displacements of inner nozzle surface showed that the nozzle diameter increases in the beginning due to thermo-mechanical stresses. The axial displacements of several points on the inner nozzle surface showed that the surface tends to displace toward the entrance plane.