ABSTRACT

This paper deals with the application of Computational Fluid Dynamics (CFD) to the analysis of the aerodynamic characteristics of symmetrical airfoil blades in 2-Dimensional cascade flow. The model was used to compare a proposed blade profile for the Wells Turbine with the NACA 0015 blade by analysing the aerodynamic forces and the compressibility effects. The objective is to increase the working angle of attack range by postponing the compressibility effects. This proposed profile was analysed as inviscid flow at the same settings as the NACA 0015 blade. The paper presents the results of the numerical investigation, while the differences in the profile geometry and the resulting differences in the blade characteristics are also discussed.

INTRODUCTION

Experimental, theoretical and computational work pertaining to the Wells Turbine has traditionally focused on the NACA four digit series blades with profile thickness of 12, 15, 18 and 21 percent of the chordlength, e.g.; Raghunathan et. al. (1989), Gato et. al. (1991), Raghunathan (1995) and Watterson and Raghunathan (1996). In order to improve the operating range of the Wells Turbine at large flow rates, Gato and Henriques (1996) used a panel method based flow methodology to optimise the blade profiles. The aim of this optimisation method was to postpone separation and stall by controlling the pressure distribution around the airfoil, resulting in modified profiles based on the NACA four and five digit series blades. The main problems with this panel method methodology were the assumptions of incompressibility and inviscid flow. This paper describes the use of computational fluid dynamics to analyse the effects of compressibility for one of these blade profiles in cascade flow and to compare with the NACA 0015 blade profile. The model was first run at a low freestream Mach number to compare with the incompressible results of Gato and Henriques (1996).

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