Traçado de pás de rotores centrífugos usando critérios de carregamento aerodinâmico e técnicas de otimização

Abstract

In this work, a computational method for the blade shape design of centrifugal impellers is presented. The method is based on the use of aerodynamic loading criteria and optimization techniques. The flow model is considered two-dimensional, incompressible and irrotational and the corresponding solutions are obtained numerically by means of a straight panel method with linear vortex distributions. With the pressure an flow coefficients fixed, the shape design is carried out by means of the maximization of the local Richardson number subject to constrains over a shape factor, defined in this work. Both the maximum Richardson number and an optimum range for the shape factor are computed with the distributions of the relative velocities and pressures on the blade. A relatively narrow range was obtained for the shape factor (between 0,8 and 0,9) for pumps and fans with specific speeds between 100 and 400. In various examples, one verifies that the proposed method is able to recover the blade shape of actual centrifugal impellers of good performance and also to adequately modify the blade shape in response to required variations of the flow and pressure coefficients.