The operating range of a compressor is usually limited by the rapid growth of 3D separations in the endwall flow region. By contrast, the freestream region is not usually close to its diffusion limit and has little effect on overall range. In light of these two distinct flow regions, this paper considers how velocity triangles in the endwall region should be designed to give a more balanced spanwise failure across the blade span. In the first part of the paper, the sensitivity of 3D separations in a single blade row to variations in realistic multi-stage inlet conditions and endwall geometry is investigated. It is shown that a blade’s 3D separation size is largely controlled by the dynamic pressure within the incoming endwall ‘repeating stage’ boundary layer and not the detailed local geometry within the blade row. In the second part of the paper the traditional design process is ‘flipped’. Instead of redesigning a blade’s endwall geometry to cope with a particular inlet profile into the blade row, the endwall region is redesigned in the multi-stage environment to ‘tailor’ the inlet profile into downstream blade rows, giving the designer a new extra degree of freedom. This extra degree of freedom is exploited to balance freestream and endwall operating range, resulting in a compressor having an increased operating range of ~20%. If this increased operating range is traded with reduced blade count, it is shown that a design efficiency improvement of ~0.5% can be unlocked.
DESIGN OF COMPRESSOR ENDWALL VELOCITY TRIANGLES
2016
Aufsatz (Zeitschrift)
Englisch
Design of Compressor Endwall Velocity Triangles
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