Description: The innovation proposed here is a Pareto-Efficient Combustion (PEC) model for fidelity-adaptive combustion modeling capability implemented into the Loci-STREAM CFD code for use at NASA for simulation of rocket combustion. This work will result in a high-fidelity, high-performance multiphysics simulation capability to enhance NASA’s current simulation capability of unsteady turbulent reacting flows involving cryogenic propellants. The PEC model utilizes a combustion submodel assignment, combining flamelet-based combustion models (such as inert-mixing models, equilibrium chemistry, diffusion-flame Flamelet/Progress Variable (FPV) or premixed-flame models) for computationally efficient characterization of quasi one-dimensional, steady, and equilibrated combustion regimes, with combustion models of higher physical fidelity (such as thickened flame models, reduced/lumped chemistry models) for accurate representation of topologically complex combustion regions (associated with flame-anchoring, autoignition, flame-liftoff, thermoacoustic coupling, and non-equilibrium combustion processes) that are not adequately represented by flamelet models. In PEC, the selection of a combustion submodel from a set of models available to a CFD-combustion solver is based on user-specific information about quantities of interest and a local error control. With this information, the PEC model performs an identification procedure for an optimal combustion submodel assignment from the available combustion models that. This simulation capability will have direct impact on NASA’s ability to assess combustion instability of rocket engines.

Benefits: (a) High-fidelity simulations of unsteady turbulent reacting flows involving cryogenic propellants (LOX, LH2, LCH4, RP-1, etc.) (b) Simulation of H2 and CH4 flare stacks (c) Simulation of afterburning fuel-rich H2/RP-1/CH4 rocket exhaust plumes inside supersonic & subsonic rocket diffusers and flame acceleration (d) LOX/GH2 multi-element combustor modeling (e) Hot-hydrogen combustor design for total containment of Nuclear Thermal Propulsion testing (f) Design improvements for J-2X and RS-68 injectors to be used in the SLS (g) High-fidelity simulations of upper stage propulsion systems of SLS

(a) Fast and accurate simulation for a wide range of reacting flows in a variety of engineering applications. (b) Improved analysis of unsteady turbulent combusting flow fields in gas turbine engines, diesel engines, etc. leading to design improvements.