Influencing the Secondary Losses in Compressor Cascades by a Leading Edge Bulb Modification at the Endwall
R. Müller, H. Sauer, K. Vogeler, M. Hoeger
abstract:
Recent investigations have shown a significant reduction of secondary losses in turbine cascades using a modification of the blade at the endwall, a so called bulb. This paper deals with the same objective but is focussed on experimental and numerical work in compressor cascades. The cascades are modified near the endwall with a similar bulb as the earlier turbine cascades.
The investigations have been carried out on a modified profile hub section of the Dresden Low Speed Research Compressor (LSRC) rotor blade, a compressor profile with a nominal turning of 18 degree. A datum configuration and a bulb configuration were tested in the Dresden Low Speed Cascade Wind Tunnel. An intensified suction side branch of the horse shoe vortex by a bulb was expected counterrotating to the passage vortex with an influence on its propagation. The interaction of the passage vortex and the boundary layer on the blade suction side is influenced. The superposition of both is decreased and the losses developing by this effect are significantly lower. The cases show a reduction in losses of 0.5 - 1.5 % as a function of the blade turning. This equals a reduction of the isolated secondary losses by 15 - 25 % with respect to the reference profile. It supports the physical understanding of the role of the horse shoe vortex in the loss production due to the passage vortex in compressor cascades.
Detailed results of total pressure measurements are presented for both cascades.
reference:
ASME Turbo Expo 2002 Amsterdam, GT-2002-30442.