Experimental investigation on vortical type flow in compressor cascades

A series of experiments to investigate the vortical flow in compressor cascades have been completed with a measuring and visualizing system. The phenomena observed include the generation of corner vortexes and the interaction between corner vortexes and boundary layers on the blade suction surface in the compressor cascades. Based on these experimental results, the flow topology and vortex structure related to the flow pattern have been deduced at moderate incidences. However, at high incidences some important changes for the flow pattern appear and vortex breakdown and reversed flow represent the main characteristics of the vortical flow. Furthermore, the dynamic effects in the compressor cascade, such as the effects of the vortical flow on loading and losses, have been investigated. The results obtained are as follows: (1) At moderate incidences, a high loss region in the corner appears along with the formation of the corner vortex system. The principal loss mechanism comprises: (a) the three-dimensional seperation of the corner vortex and secondary vortexes; (b) mixing of fluids with low and high momentum in the corner vortex system. (2) At high incidences, the reversed flow caused by vortex breakdown and strong adverse pressure gradient makes an important contribution to the loss increase. Other results are also reported.