Influence of Gap Shape on Flow Characteristics of Highly Loaded Compressor Tandem Cascades

Abstract Gap shape is an important factor affecting the tandem cascade performance. This paper uses the gap expansion angle (Kb−b) to define gap shape and studies the effect of Kb−b on the two-dimensional flow field and flow characteristic near the endwall in a highly-loaded subsonic tandem cascade. By changing the incidence angle from −20 to 10°, the Kb−b value increases, and the two-dimensional tandem cascade performance improves at positive incidence angles, while it descends at zero and negative incidence angles. Due to the influence of Kb−b on the camber of front and rear blades (RB), the optimal Kb−b should provide appropriate load distribution and sufficient gap flow strength. The corner stall more likely appears on the front blade near the endwall, which can suppress the flow separation on the rear blade to a certain extent. The Kb−b value near the endwall should be slightly larger than in the midspan to ensure a sufficient operating range for the front blade. For a highly loaded subsonic tandem cascade, the overall optimal range of Kb−b is between −12 and 0°.