Conjugate heat transfer simulation of a subscale rocket thrust chamber using a timescale based frozen non-adiabatic flamelet combustion model

With the goal of supporting the industrial rocket thrust chamber development process, numerical simulation tools must be able to deliver a high fidelity prediction regarding the wall heat transfer and performance characteristics. In order to achieve this for the propellant combination methane-oxygen, a non-adiabatic flamelet combustion model extended by reaction timescale effects is employed. The newly developed model extends the validity domain of the flamelet modeling concept to fully cover the spectrum observed in rocket thrust chambers. By incorporating kinetic rate effects into the flamelet formulation, it enables a transition between the fluid dynamic and reaction rate dominated combustion regimes depending on the local Damkoehler number of the numerical solution field. This research work presents the respective modeling strategy together with a first application to a subscale rocket thrust chamber operating with gaseous methane and oxygen. The analysis of this test case is done using a 3D RANS conjugate heat transfer setup resolving both the hot gas and coolant flow together with the surrounding copper structure. The application of the new modeling strategy provides accurate predictions of the wall heat transfer and wall pressure distributions validated against experimental data. This presents a significant improvement compared to the existing modeling approaches.