The outcome of the proposed Phase 1 and Phase 2 research and development activities will be a powerful and advanced version of a CFD-based multiphase combustion code (called Loci-STREAM) for propulsion engines at NASA. This code is envisioned to be a powerful design and analysis tool for propulsion devices including full rocket engine simulations, injector design, etc. This tool will have a direct impact on development of propulsion systems relevant to the SLS by enabling design improvements of injectors involving liquid propellants such as LOX, LH2, LCH4, RP1, etc. Specific applications at NASA of this capability will include: (a) Fast and accurate simulation of turbulent combustion in existing or new/modified liquid space propulsion engines including J-2X, RS-68, F-1, etc., (b) Fast and accurate 3D unsteady simulations of multi-element injectors coupled with fuel and oxidizer feed lines and manifolds which will yield high-fidelity information for combustion instability models, (c) Prediction of stability and stability margins, (d) Design of acoustic cavities for combustion stability, etc. The computational tool resulting from this project will have wide-ranging commercial applications. The Hybrid RANS-LES (HRLES) methodology can be used for a wide variety of engineering applications involving unsteady turbulent flows. The high-fidelity turbulent combustion simulation capability will lead to improved analysis of unsteady turbulent reacting flow fields in gas turbine engines, diesel engines, etc. leading to design improvements. The real-fluids methodology can be used in a large number of industrial flow situations involving both chemically inert and reacting flows. With additions of multi-phase combustion modeling capability, the applicability of this tool can be further broadened.