A comparative study on the reducing flow rate design method for a desalination energy recovery pump as turbine

The energy recovery and utilization of high-pressure brine are the key to reduce the cost. Reducing flow rate method (RFM) was put forward firstly to adapt pump as turbine (PAT) to a wide range of operating conditions in this paper. In order to validate advantages of the new method, three different designs of PAT were obtained, respectively, based on three different methods, which were, respectively, selection design method, forward curved method and RFM. Based on numerical method, the external energy characteristics, axial force and internal flow patterns of PATs were analyzed. Results show that matching of the blade inlet angle and flow angle at the blade leading edge has a great influence on the turbine flow patterns which are directly related to the efficiency of PAT. A PAT designed by the new design method RFM improves both the hydraulic efficiency and shaft power under design and partial load conditions. Moreover, the axial force of the PAT designed by RFM is reduced, which can improve the reliability of the PAT operation with high rotating speed.