Influencing the Secondary losses in compressor cascades by a leading edge bulb modification at the endwall
R. Müller, H. Sauer, K. Vogeler, M. Hoeger
Recent investigations have shown a possible reduction of secondary losses in turbine cascades as well as compressor cascades using a bulb like modification of the profile at the endwall. This paper is focused on experimental and numerical work in comparison of a reference compressor cascade and its modification. The cascade is modified near the endwall with a similar bulb as the earlier investigated turbine cascades.
The investigations have been carried out on a profile developed from a 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 (V63) and a bulb configuration (V63.1) were tested in the Dresden Low Speed Wind Tunnel (LSWT). An intensified horse shoe vortex was suspected and observed counterrotating to the passage vortex with an influence on its propagation. This proves the authors' physical understanding of the horse shoe vortex and its mechanism of loss production in compressor cascades.
The suction side horse shoe vortex influences the interaction of the passage vortex and the suction side profile boundary layer. The superposition of both is minimized and the losses developing from this effect re significantly lower. One case shows a reduction in losses of 0.5-3 % in dependence of the blade turning. This equals a reduction of the isolated secondary losses up to 30 % with respect to the reference profile. Detailed results of total pressure measurements are presented for the reference and the modified cascades.
The measurement was followed by a numerical approach, using the DLR code TRACE at MTU. A comparison of experiments and numerical analysis was done. The numerical simulation was able to produce results which match the experiments qualitatively.
5th European Conference on Turbomachinery - Fluid Dynamics and Thermodynamics, Prague, Czech Republic, March 18 - 21, 2003, submitted for publication