A New Design Concept of Highly-Loaded Axial Flow Compressor by Applying Boundary Layer Suction and 3D Blade Technique

Abstract

A new design concept of highly-loaded axial flow compressor by applying boundary layer suction and 3D blade technique was proposed in this paper. The basic idea of this design concept was that low reaction was adopted as while as increasing the rotor’s geometry turning angle, so that the boundary layer separation of a rotor could be eliminated and the rotor was kept working in high efficiency. This design concept would greatly increase the stator’s geometry turning angle, so boundary layer suction on stator cascades was adopted in order to restrain the boundary layer separation. In some situations, 3D blade technique was also applied in order to control the boundary layer separation more efficiently. The advantages of the above design concept were: the compressor’s pressure ratio was increased remarkably; boundary layer suction was only adopted in stator cascades so as to reduce the complexity of boundary layer suction structure. The key techniques of the new design concept were also explained in this paper. In order to increase the compressor’s pressure ratio, the geometry turning angle of rotor was increased greatly, and the rotor inlet was prewhirled to reduce the rotor’s reaction so as to restrain the rotor’s boundary separation. Boundary layer suction was carried out in the stator cascades (mainly on suction side), hub and shroud in order to control the flow separation. 3D blade technique could be adopted if necessary. The limitation of the application of this design concept was also pointed out through the analysis of the Mach number at rotor inlet, the prewhirl angle of rotor, the work distribution along span wise and the control method of stator separation. Numerical simulation was carried out on a single low-reaction compressor stage with IGV in order to demonstrate the new design concept. By using boundary layer suction and 3D blade technique, the energy loss in stator cascades was greatly reduced and the whole stage’s isentropic efficiency was about 90%. The low-reaction stage’s aerodynamic load was double than conventional design. The boundary layer separation could be effectively controlled by proper combination of boundary layer suction and bowed or twisted blade. The numerical result proved that the new design concept was feasible and had a wide application area.