Tip leakage flow of a vibrating airfoil in a linear compressor cascade

Abstract

In turbomachinery, understanding the interaction between blade vibrations and the tip flow is of great interest due to current trends, which tend to thinner airfoils with higher loading and higher efficiencies. The present paper experimentally investigates the unsteady tip leakage flow/vortex (TLF/V) of a vibrating airfoil in a compressor cascade with a large tip gap subjected to bend-mode controlled oscillations. Tip wall pressure distribution and secondary tip flow in the blade channel were studied using high-response pressure measurements and stereoscopic particle image velocimetry. The effects of blade vibrations on the TLF field and the TLV wandering characteristics are explored. The experimental results demonstrate that the TLF field is dominated by the TLV, and the TLV synchronously wanders with the displacement of the blade. Besides, the vortex intensity, the vortex wandering intensity, and turbulence fluctuations are phase-shifted by π/2 concerning the displacement of the blade. In contrast, the velocity deficit in the vortex core is not influenced by blade vibrations. This study provides the phase-resolved tip flow field of a vibrating airfoil with tip gaps in a linear compressor cascade, which is a necessary step toward compressor blade vibration prediction.