Impact of Different Chemical Models on the Numerical Prediction of Dual-Bell Nozzle Transition

Kurzfassung

A numerical study was conducted at the German Aerospace Center in Lampoldshausen, to investigate the impact of various chemical models on reactive nozzle flow. Therefore, a chemical reaction mechanism for oxygen/methane combustion was implemented into DLR's flow solver TAU. Ignition delay simulations were conducted to demonstrate the validity of the implementation. The implemented baseline chemistry model was applied for generic nozzle flow simulations and the results were compared to frozen nozzle flow and approach. The baseline reaction mechanism was reduced to a basic configuration and applied to the generic nozzle flow. A good agreement with the baseline model was observed. Both approaches were aplied for dual-bell nozzle flow simulations. Validation data for the simulations were obtained during a hot flow test campaign. The experiments yielded a clear impact of the combustion chamber mixture ratio on the dual-bell transition nozzle pressure ratio. RANS simulations of the dual-bell nozzle flow were conducted and almost no deviation between baseline and reduced chemical approach was observed. A reduction of 93 % of the computational cost was reached with the reduced model. The dual-bell transition behavior at different values of combustion chamber mixture ratio was investigated, applying RANS simulations with reduced chemistry model. The impact of the mixture ratio on the transition NPR was clearly reproduced by the numerical approach. A good agreement with the experimentally obtained transition NPR values was reached.