Experimental Study on Linear Compressor Cascade with Three-Dimensional Blade Oscillation

An experiment is carried out to enhance the understanding of three-dimensional blade aeroelastic mechanisms and to produce test data for validation of numerical methods. A compressor cascade test rig developed consists of seven prismatic controlled diffusion blades with the middle blade being oscillated in a three-dimensional bending/flapping mode. Steady and unsteady pressure measurements are performed at six spanwise sections for three reduced frequencies and two tip-clearance gaps. Off-board pressure transducers are utilized with a transfer-function method correcting tubing errors. The tuned cascade results are constructed by using the influence coefficient method. The results illustrate fully three-dimensional unsteady behaviour. The blades are aeroelastically destabilized as the tip gap is increased, and the destabilizing effect of the tip-clearance influences most of the span. The total aerodynamic damping at the least stable interblade phase angle is reduced by 27% when the tip gap is increased from nearly 0 to 2% span.