Experimental study on aeroelasticity in linear oscillating compressor cascade. Part II: Tip-clearance effect

An experiment is carried out to enhance the understanding of three-dimensional(3D) blade aeroelastic mechanisms and to produce the experimental data for the validation of numerical methods. This is Part II of a two-part series. Part I describes the experimental study on the aeroelastic stability of the compress oscillating cascade. The emphasis of this part is to identify the tip-clearance effects on the aeroelastic response of the same oscillating cascade. The blades are aeroelastically destabilised as the tip gap is increased, and the destabilised region is seen to extend to almost the whole blade span, which is consistent with the strong spanwise unsteady interaction. This destabilising effect of tip-clearance is independent on inter-blade phase angle with the maximum effect at the least stable inter-blade phase angle. The chordwise trend in amplitude of unsteady pressure with increasing tip clearance is observed in the regions where the tip leakage flow has an obvious effect on the corresponding steady loading. The results clearly demonstrate that numerical methods without tip-clearance effect might over predict cascade stability.