Investigation on the design and performance analysis methods of centrifugal turbomachines

Abstract

The present study has tested most of loss models previously published in the open literature and found an optimum set of empirical loss models for a reliable performance prediction of centrifugal compressors. In order to improve the prediction of efficiency curves, this study recommends a modified external loss model. Predicted performance curves by the proposed optimum set agree fairly well with experimental data for a variety of centrifugal compressors. The present study also modifies the optimum set of loss models for centrifugal compressors by removing the compressibility flow effects and includes the additional pump loss correlations in order to predict the performance of centrifugal pumps. The prediction method developed through this study can serve as a conceptual tool for preliminary design and assist the understanding of the operational characteristics of general purpose centrifugal compressors and pumps. An optimal design code for centrifugal pumps has been developed to determine geometric and fluid dynamic variables under appropriate design constraints. The optimization problem has been formulated with a nonlinear objective function to minimize one, two or all of the fluid dynamic losses, the net positive suction head required and the product price of a pump stage depending on the weighting factors selected as the design compromise. The optimal solution is obtained by means of the Hooke and Jeeves direct search method. The performance analysis is based on the mean streamline analysis using the present state-of-the-art loss correlations. The optimized efficiency and design variables of centrifugal pumps are presented in this study as a function of non-dimensional specific speed in the range of $0.5 ≤ N_s ≤ 1.3$. The diagrams presented herein can be used efficiently in the preliminary design phase of centrifugal pumps. And this study presents a systematic two-zone modeling for reliable performance prediction of centrifugal compressors. In order to impr...