Session: 31-10 Flow Control

Paper Number: 152653

The Design of Aspirated Stators for Compressor Bleed 

The operation of gas turbines requires air to be removed from the primary compressor flow path for a variety of purposes including turbine cooling and off-design stage matching.  This “bleed” air is typically extracted through the compressor casing either using a continuous circumferential slot, or by large discrete holes, each with a diameter on the order of a blade pitch.  In this paper, the benefits of extracting air through an array of small holes on the stator blade suction surface, each with a diameter on the order of one percent of blade chord, are identified.  Such blades are referred to as aspirated compressor blades.  Using a combined experimental and computational approach, two findings are described.  First, the operating range of the aspirated compressor blade is widened by the control of corner separations.  The aspiration reduces the streamline curvature of the surface limiting streamlines, inhibiting corner separation formation.  It is shown that such control is sensitive to the removal of air from the blade surface very close to the endwall where the separation is expected to occur, and that robustness is increased by employing more aspiration holes in this region compared to mid-span.  The second finding is that the total loss of the bleed system can be reduced with the removal of air via a combined circumferential bleed slot and aspirated compressor blade approach.  This integrated approach combines the beneficial control of blade separations at high loading from the aspiration, with the low extraction loss of the circumferential bleed slot.  Both findings are demonstrated in experiments and simulations of a low-speed research compressor and also in computations of a high-speed compressor design representative of a modern industrial gas turbines. 

Presenting Author: Jonathan Waldren University of Cambridge

Presenting Author Biography: Jonathan is a researcher at the Whittle Laboratory in the University of Cambridge. His current research focuses on the design and testing of aspirated compressor blades. He has also previously researched counter-rotating turbomachinery.

Authors:

Jonathan Waldren University of Cambridge
Ryosuke Seki Research and Innovation Center, Mitsubishi Heavy Industries Ltd
Sam Grimshaw University of Cambridge
Graham Pullan University of Cambridge