Viscous Throughflow Modelling of Axial Compressor Bladerows Using a Tangential Blade Force Hypothesis

Abstract

This paper describes the modelling of axial compressor blade rows in an axisymmetric viscous throughflow method. The basic method, which has been reported before, includes the effects of spanwise mixing, using a turbulent diffusion model, and endwall shear within the throughflow calculation. The blades are modelled using a combination of existing two-dimensional blade performance predictions for loss and deviation away from the annulus walls and a novel approach using tangential blade forces in the endwall regions. Relatively simple assumptions about the behaviour of the tangential static pressure force imposed by the blades allow the secondary deviations produced by tip clearance flows and the boundary layer flows at fixed blade ends to be calculated in the axisymmetric model. Additional losses are assigned in these regions based on the calculated deviations. The resulting method gives realistic radial distributions of loss and deviation across the whole span at both design and off-design operating conditions providing a quick method of estimating the magnitudes of these effects in the preliminary design process. Results from the method are compared to measured data in low and high speed compressors and multistage three-dimensional viscous CFD predictions.