Effects of mixing assumptions and models for LES of Hydrogen-fueled Rotating Detonation Engines

Large Eddy Simulations (LES) are a powerful tool to analyze the flow in Rotating Detonation Engines, but their implementation is not straightforward. Many groups use simplifications (perfect premixing, geometrical 2D representations of the chamber) and numerical high-fidelity analysis comparing mixing assumptions in full scale configurations are not commonly found in literature. In this work a 3D LES of a full RDE tested at TU Berlin is performed and the influence of mixing assumptions (fully premixed vs. non-premixed) and sub-grid scale models on the detonation propagation are investigated. Simulations show that premixed RDEs burn more fuel in a detonation regime, resulting in a faster detonation wave than in the non-premixed case, while a change in the sub-grid scale model does not lead to significant changes. LES reveals that all cases lose a high amount of fuel to non-detonative combustion. These results show, that mixing plays a significant role in the LES of RDEs and has to be included to increase the accuracy of the simulations. The importance of deflagration in the overall RDE combustor implies, that chemistry models need to account for deflagration properties as well as for detonation to capture the efficiency of RDEs.