Blade Bowing Effect on Aerodynamic Performance of a Highly Loaded Turbine Cascade

Abstract

A S ONE of the major measures to improve the aerodynamic performance of modern turbines, highly loaded blades (blades with a high-turning angle) have attracted much attention in the past two decades [1–7]. However, it is found that due to the high-turning angle, the highly loaded blades cause high loss because of the serious secondary flow and centralized vortices [1–7]. Blade bowing (compound leaning or curving) has been recognized as an effective way to reorganize the vortices, reduce the secondary flow loss, and improve the efficiency of turbines [4–8], and also the fundamental for the three-dimensional optimization of turbine blades [6,9–11]. It is therefore the primary motivation of this work to find out whether the blade bowing applies to improving the performance of the highly loaded turbine cascade (turning angle 113 deg). The second motivation of this paper is to carry out a systematic studywith a series of negatively and positively bowed highly loaded blades. (When the dihedral angle between the blade pressure side and cascade endwalls is acute, the bowed angle is positive and vice versa). Clearly there is a vacuum of such a systematic study in highly loaded turbine cascades, as only few certain bowing angles were investigated individually [4,5,8].