Editorial

Abstract

This volume contains eight papers on turbomachinery covering CFD applications, detailed flow measurements on unsteady flow, new design methods and control devices, and conventional empirical approaches. Shi and Tsukamoto succeeded in predicting pressure fluctuations caused by the interaction between a centrifugal impeller and diffuser vanes, using a Navier-Stokes code with standard k−ε turbulence model. Using a commercial code, Gu et al. succeeded in predicting the performance of a single-stage centrifugal compressor and studied the volute/diffuser flow in detail at design and off design conditions. By combining a scheme called the Single-Sweep Method with an algebraic eddy viscosity model, Kochevsky made a parametric study of the energy loss in annular diffusers with a rotating hub and inlet flow swirl, with the purpose of minimizing the loss in annular diffusers. These papers suggest that CFD is now becoming capable of predicting not only steady flows under design flow conditions, but also unsteady flows and off-design flows. Sinha, Pinarbasi and Katz, using PIV and pressure fluctuation measurements, made detailed observations of unsteady flow process during the onset and developed stages of rotating stall within a vaned diffuser of a centrifugal pump. This work is useful for refining CFDs so that they can predict local flow process, as well as for obtaining a physical understanding of the stalling process. The combination of those efforts in CFD and detailed flow measurements will lead CFDs to more useful design tools that require less experience and fewer empirical factors, and also to methods for clarifying the flow physics in turbomachinery.