This project will explore the application of large-eddy simulation to realistic three-dimensional turbo machinery configurations. Case studies will focus on the centrifugal compressor and low-pressure-ratio axial fan, with the additional geometries of interest being high- and low-pressure turbine. Centrifugal compressors are a key technology in many of UTC products: commercial chillers (Carrier), aircraft environmental control systems, aircraft auxiliary power units, and fuel pumps (Hamilton Sundstrand, Pratt & Whitney Rocketdyne), and in rotorcraft and business jet engines (Pratt & Whitney Canada). An efficient low-pressure-ratio axial fan is a key component for the geared turbofan architecture that Pratt & Whitney has developed for its next generation of commercial jet engines to enable lower fuel burn than traditional designs. Large-eddy simulation is particularly attractive for modeling turbulent flows in turbomachinery because these flows contain several features that have over the years proven to be a challenge for RANS turbulence models widely used in industry. These features include: strong rotational effects due to the high rotational speeds; strong curvature of the hub and shroud surfaces yielding highly 3-D flows in the indwell regions; large tip-clearance vortices that typically migrate downwards and occupy a significant portion of the flow passage; and the presence of flow separation, especially at off-design conditions. For flows that encounter transition from laminar to turbulent flow, such as is in the case of the low-pressure ratio fan, modeling is entirely based on tedious calibration with experiments for various modes of transition further reducing the predictive capability of RANS framework. Our ability to better understand the flow physics in these specific product components using wall-resolved large-eddy simulation on grids of sufficient resolution will help lead future design improvements and will be critical to improved energy efficiency of our products going forward.
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