Optimization of Loss Models for Centrifugal Compressor Performance Prediction Based on Numerical Analysis Results

An optimization of loss models for performance prediction of centrifugal compressors has been conducted in this paper. A centrifugal compressor with vaneless diffuser (VLD) and vaned diffuser (VD) is selected for the present study. The study begins with a numerical analysis, using commercial software ANSYS CFX. The numerical result is used to modify mean streamline analysis loss models. Matlab optimization toolbox is used for this purpose. Also, a matlab program is compiled to calculate the off-design performance of the centrifugal compressor. The results show that after optimizating the loss models, mean streamline analysis has a better accuracy than before.

Performance Prediction of Cross-Flow Fans Using Mean Streamline Analysis

This paper presents the mean streamline analysis using the empirical loss correlations for performance prediction of cross-flow fans. Comparison of overall performance predictions with test data of a cross-flow fan system with a simplified vortex wall scroll casing and with the published experimental characteristics for a cross-flow fan has been carried out to demonstrate the accuracy of the proposed method. Predicted performance curves by the present mean streamline analysis agree well with experimental data for two different cross-flow fans over the normal operating conditions. The prediction method presented herein can be used efficiently as a tool for the preliminary design and performance analysis of general-purpose cross-flow fans.

Mean streamline performance analysis of mixed-flow fan impellers covering the low flowrate characteristics

The mean streamline analysis using the empirical loss correlations has been developed for performance prediction of industrial mixed-flow fan impellers in the present study. New simple, but effective, models for the additional Euler input work characteristic and a suction recirculation loss due to internal flow reversal under the low flowrate conditions are proposed in this paper. Comparison of overall performance predictions with six sets of test data of mixed-flow fans is accomplished to demonstrate the accuracy of the proposed models. Predicted performance curves by the present set of loss models agree fairly well with experimental data for a variety of mixed-flow fan impellers over the entire operating conditions. The prediction method presented herein can be used efficiently in the conceptual design phase of mixed-flow fan impellers.

Conceptual design optimization of mixed-flow pump impellers using mean streamline analysis

A conceptual design optimization code for mixed-flow pump impellers has been developed to determine the geometric and fluid dynamic variables under appropriate design constraints. In the present study the optimization problem has been formulated with a non-linear objective function to minimize the fluid dynamic losses. The optimal solution is obtained by means of the Hooke-Jeeves direct search method. Computations are performed using mean streamline analysis and the present state-of-the-art loss correlations. Changes in the optimized efficiency and design variables of mixed-flow pump impellers are presented in this paper as a function of non-dimensional specific speed in the range 1.9 ≤ Ns ≤ 2.5. The diagrams presented herein can be used efficiently in the preliminary design phase of mixed-flow pump impellers.

Performance prediction of mixed-flow pumps

This paper presents the mean streamline analysis using the empirical loss models for performance prediction of mixed-flow pumps with high specific speeds. A new internal loss model to describe the effect of flow separation on the characteristic head-capacity curve with a dip in the low flow range is developed and a modified recirculation loss model for calculation of parasitic loss due to flow recirculation at the impeller exit is suggested in this study. The prediction performance of the proposed method here is tested against four sets of measured total heads and efficiencies of mixed-flow pumps, and it is also compared with that based on two-dimensional cascade theory. Predicted results by the present set of loss models agree very well with experimental data for a variety of mixed-flow pumps over the normal operating conditions.

Experimental and Theoretical Analysis of the Flow in a Centrifugal Compressor Volute

Detailed measurements of the swirling flow in a centrifugal compressor volute with elliptical cross section are presented. They show important variations of the swirl and throughflow velocity, total and static pressure distribution at the different volute cross sections and at the diffuser exit. The basic mechanisms defining the complex three dimensional flow structure are clarified. The different sources of pressure loss have been investigated and used to improve the prediction capability of one-dimensional mean streamline analysis correlations. The tangential flow loss model under decelerating flow conditions and the friction loss model are confirmed. New empirical loss coefficients are proposed for the exit cone loss model and the tangential flow loss model for the case of accelerating flow in the volute.

Experimental and Theoretical Analysis of the Flow in a Centrifugal Compressor Volute

Detailed measurements of the swirling flow in a centrifugal compressor volute with elliptical cross section are presented. They show important variations of the swirl- and throughflow velocity, total and static pressure distribution at the different volute cross sections and at the diffuser exit. The basic mechanisms defining the complex 3D flow structure are clarified. The different sources of pressure losses have been investigated and used to improve the prediction capability of one dimensional mean streamline analysis correlations. The tangential flow loss model, under decelerating flow conditions, and friction loss model are confirmed. New emprical loss coefficients are proposed for the exit cone loss model and the tangential flow loss model for the case of accelerating flow in the volute.