Extracting Meanline Modeling Parameters for Radial Turbomachinery From CFD

Abstract

Abstract Meanline performance models have a long history of use in the design of radial flow pumps and compressors. Most data used to create correlations are point data such as static pressures and temperature measurements at walls with occasional traverses for more details of the flow field. These point measurements along with limited traverses, while very useful, do not provide details of specific flow characteristics internal to the machine. The Two-Zone model, developed by Japikse and others, is a meanline model based on point measurements that enables prediction of machine performance. The model assumes that the flow at the impeller exit is composed of a primary zone that is isentropic and a secondary zone where losses exist. The Two-Zone model can accurately predict power when the fraction of mass flow in the secondary zone (χ) and the deviation angle in the primary (δ2p) and secondary (δ2s) zones are correctly inferred from the available data. However, it is difficult to ensure that the parameters inferred from the Two-Zone flow model structure are uniquely correct. In this paper, the specific details of the impeller exit flow fields required to generate an accurate prediction using the Two-Zone model are extracted from CFD simulations. Using CFD, flow fields at the impeller exit are obtained and analyzed to calculate the model parameters for 10 radial flow machines. The derived two zone parameters are then used to predict the power for each machine. The Two-Zone predictions match the experimental data with an average error of 3.5%.