Controlled-endwall-flow blading for multistage axial compressor rotor

This research aims to develop an advanced technology of highly loaded axial compressor stages with high efficiency and sufficient surge margin. To improve endwall boundary layer flows which lead to energy loss and instability at an operation of low flow rate, the Controlled-Endwall-Flow (CEF) rotor blades were designed and tested in the low speed rotating cascade facility of Kyushu University. The CEF rotor blades have three distinctive features: the leading-edge sweep near hub and casing wall, the leading-edge bend near the casing, and the same exit metal angle of blade evaluated by a conventional design method. Mechanical strength of the blade was verified by a numerical simulation at a high speed condition. The baseline rotor blades were designed under the same design condition and tested to compare with the CEF rotor. The results showed that the maximum stage efficiency of the CEF rotor was higher by 0.7 percent and the increase in surge margin was more than 20 percent in comparison with the baseline rotor. The results of both internal flow survey and 3D Navier-Stokes analysis showed that improvement of the overall stage performance resulted from activation of the endwall boundary layers, and suggested that further improvement might be expected by combination of end-bend stator blades and a highly loaded axial compressor stage could be developed by use of the CEF rotor.