Michael T. Barton

Numerical Designed Experiment to Optimize a Ported Shroud to Extend the Operability Margin of a Centrifugal Compressor

This paper describes the Computational Fluid Dynamic (CFD) numerical optimization of a modern centrifugal compressor impeller with a ported shroud for increased surge margin. The vent configuration selected was a full circumference, constant-width slot. A multiblock, steady flow three dimensional (3D) viscous RANS model (ADPAC) is used with parallel processing capability to increase computational speed. Grid generation is performed in an automated fashion to enable the timely optimization of the ported shroud configuration. A designed experiment (DoE) approach is used to minimize the number of vent configurations to be modeled, to ensure that factor interaction effects are captured, and to facilitate the definition of an optimum vent configuration. The DoE is a 2 factor, 2 level full factorial experiment with a center point included to detect possible curvature in the solution surface. The factors optimized are slot width and the flow-wise location of the slot. The numerical technique verifies the ability of the ported shroud to extend compressor stall margin at the part-speed operating condition, while maintaining acceptable high speed performance, in good agreement with test data for a similar impeller with a ported shroud. The use of a DoE method coupled with CFD modeling identified an optimized vent configuration with a minimum of time and effort. The CFD results also provide enhanced understanding of the device physics.Copyright

Numerical Optimization of a Vaned Shroud Design for Increased Operability Margin in Modern Centrifugal Compressors

This paper describes the computational fluid dynamics (CFD) approach coupled with an automated grid generation technique utilized for the numerical optimization of a modern centrifugal compressor with an inducer vaned shroud for increased operability margin. The grid generation process was automated to permit rapid optimization of the impeller and vaned shroud geometry. A three dimensional (3D), viscous, steady flow, mixing-plane approach was utilized to numerically analyze the impeller and vaned shroud in a coupled fashion to capture the interaction effects. The numerical technique verifies the ability of the vane shroud to extend compressor surge margin at the part-speed operating condition, while maintaining acceptable high-speed performance. CFD analyses confirm that the aerodynamics of the vaned shroud match expectation, and are consistent with the mass-averaged compressor speedline characteristics generated from the CFD results.Copyright