Comparison of aerodynamic characteristics between a novel highly loaded injected blade with curvature induced pressure-recovery concept and one with conventional design

This paper introduces a novel design method of highly loaded compressor blades with air injection. CFD methods were firstly validated with existing data and then used to develop and investigate the new method based on a compressor cascade. A compressor blade is designed with a curvature induced pressure-recovery concept. A rapid drop of the local curvature on the blade suction surface results in a sudden increase in the local pressure, which is referred to as a curvature induced 'Shock'. An injection slot downstream from the 'Shock' is used to prevent 'Shock' induced separation, thus reducing the loss. As a result, the compressor blade achieves high loading with acceptable loss. First, the design concept based on a 2D compressor blade profile is introduced. Then, a 3D cascade model is investigated with uniform air injection along the span. The effects of the incidence are also investigated on emphasis in the current study. The mid-span flow field of the 3D injected cascade shows excellent agreement with the 2D designed flow field. For the highly loaded cascade without injection, the flow separates immediately downstream from the 'Shock'; the initial location of separation shows little change in a large incidence range. Thus air injection with the same injection configuration effectively removes the flow separation downstream from the curvature induced 'Shock' and reduces the size of the separation zone at different incidences. Near the endwall, the flow within the incoming passage vortex mixes with the injected flow. As a result, the size of the passage vortex reduces significantly downstream from the injection slot. After air injection, the loss coefficient along spanwise reduces significantly and the flow turning angle increases.