Internal Flow Field and Loss Structure of a Stator in an Axial Compressor at Windmilling Conditions

Abstract

The windmilling condition occurs when the air flowing through an unlit engine drives the rotor blades, similar to a turbine. In this study, the internal flow field of stators is investigated both experimentally and numerically. The pressure surface separation vortex on a stator can be classified into two types with legs on the tip and hub. In the free windmilling condition, where the load at rotor blades was equal to zero, the two vortices merge and collapse, and the collapsed components accumulate at mid span, forming a single point where the loss at the exit of stators reaches maximum. On the other hand, in the highly loaded windmilling condition, where the load on the rotor blades is negative, the influence of the flow from the tip to mid span is reduced, and the two vortices do not accumulate in one place, resulting in two loss maxima in the radial direction.