Multiphysics Modeling of Dynamic Combustion Processes

The objective of this effort is to develop a zonal, multi-physics modeling framework for dynamic combustion processes that can capture relevant local physics and simulate system behavior while significantly reducing computational cost. Presently, large eddy simulations (LES) of complete combustors with detailed kinetic sets are not practical for design studies and evaluating control strategies. The goal here is to obtain an order of magnitude reduction in current simulation time within acceptable solution error limits. In the proposed multi-zonal framework, the injector near field is computed with a flamelet/progress variable (FPV) formulation while the downstream region of the combustor is replaced with a reduced order model (ROM). The FPV formulation for the injector near field results in just three scalars even though the underlying kinetic mechanism on which the table is generated may be detailed with a large number of species; we will be demonstrating savings of a factor of ten relative to detailed finite rate kinetics as part of this effort. Furthermore, the FPV formulation has been shown to be accurate in modeling unsteady combustion dynamics and heat release with adequate fidelity for the present application. The downstream reduced order model (ROM) domain, is also computationally efficient and provides an accurate interface with upstream zone. The downstream ROM responds to fluctuations propagating in while simultaneously providing interface conditions for the upstream zone. The proposed Phase II program addresses these needs and builds upon the feasibility demonstrated in the Phase I effort. The two broad objectives of the Phase II effort are to: 1) Formulate multi-dimensional training procedures for ROMs – This set of tasks seeks the development of procedures to train ROMs to provide accurate responses to streamwise convective flow with spanwise variations, as well as transverse acoustic fluctuations that propagate through the interface, and 2) Mature the ROM/FOM multi-zonal framework and interface coupling – This set of tasks deals with a broad range of issues including the implementation of robust and efficient ROM formulations and porting to other CFD frameworks, improving the accuracy of flux exchange at the interface, development of API for multi-pressure FPV table look-up for interfacing with other CFD frameworks, coupling of oxidizer and fuel manifold to combustor near-field, and demonstration of the framework on 3D combustor configurations. The resulting product will be a predictive simulation tool for combustion dynamics that is computationally tractable for use in a design support role.