Coupled Simulations of Finite-Rate Ablation with Pyrolysis in Rocket Nozzles

Abstract

An ablation model based on finite-rate heterogeneous reactions is incorporated into a conjugate flowfield/ablation analysis framework, relaxing the assumption of equilibrium ablation made in previous studies using this conjugate analysis methodology. Fully coupled, conjugate, two-dimensional simulations modeling the ablation of pyrolyzing carbon–phenolic material in the HIPPO nozzle test case are presented; comparisons are made between equilibrium and finite-rate surface chemistry assumptions. The finite-rate surface chemistry method provides substantially improved agreement with experimental measurements. The difference in the surface recession predictions obtained with the equilibrium and finite-rate models is larger than expected. This suggests that finite-rate surface chemistry effects may be important for temperatures above the 2000–2500 K threshold that is typically assumed for equilibrium surface chemistry. Additional studies investigate the effects of finite-rate gas-phase reactions and radiative heat transfer on the predicted ablation response.