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Defense Technical Information Center Compilation Part Notice ADP 014799 TITLE : Unstructured LES of Reacting Multiphase Flows in Realistic Gas Turbine Combustors

As part of the Accelerated Strategic Computing Initiative (ASCI) program, an accurate and robust simulation tool is being developed to perform high-fidelity LES studies of multiphase, multiscale turbulent reacting flows in aircraft gas turbine combustor configurations using hybrid unstructured grids. In the combustor, pressurized gas from the upstream compressor is reacted with atomized liquid fuel to produce the combustion products that drive the downstream turbine. The Large Eddy Simulation (LES) approach is used to simulate the combustor because of its demonstrated superiority over RANS in predicting turbulent mixing, which is central to combustion. CDP is the flagship LES code being developed by the combustor group to perform LES of reacting multiphase flow in complex geometry. CDP is named after the late Charles David Pierce (1969-2002) who made several lasting contributions to the LES of reacting flows and to this ASCI program. CDP is a parallel unstructured finite-volume code developed specifically for LES of variable density low Mach-number flows. It is written in Fortran 90, uses MPI, and has integrated combustion and spray modules. In the first five years of ASCI (1997-2002), the principle focus of the combustor group was the development and validation of an entirely new numerical method with the characteristics necessary for simultaneously accurate and robust LES on unstructured grids. These competing ends were both achieved by developing a method around the principle of discrete kinetic energy conservation (Mahesh et al. 2003). This numerical algorithm has now been extended to variable density, low-Mach number multiphase reacting flows. In March of 2003, with the underlying numerics established and validated in a variety of flows, a major redesign and rewrite of the code was initiated. Called CDP-α, this new version of the code will have all the capabilities of the current code along with considerable improvements, all of which are considered critical to achieving the stated ASCI goal of a “major advance in engine simulation technology.” This paper summarizes the accomplishments of the combustor group over the past year, concentrating mainly on the two major milestones achieved this year: • Large scale simulation: A major rewrite and redesign of the flagship unstructured LES code has allowed the group to perform large eddy simulations of the complete combustor geometry (all 18 injectors) with over 100 million control volumes. • Multi-physics simulation in complex geometry: The first multi-physics simulations including fuel spray breakup, coalescence, evaporation, and combustion are now being performed in a single periodic sector (1/18) of an actual Pratt & Whitney combustor geometry.