Study on the effect of rotor tip fillet edge in axial compressor

Abstract

The compressor flowfield is sensitive to the small geometry in the tip region. The blade tip edge, which was usually idealized as “sharp” edge in the numerical simulation, had been actually filleted during the process of machining, coating, and wearing. However, the fillet edge was completely neglected in the compressor performance estimation. Thus, in this paper, the effect of the fillet edge is evaluated by establishing several models with tip fillet edges as well as tip sharp edge in a transonic axial compressor. By the comparison of the flowfield between models with fillet edge and sharp edge, it was found that the tip fillet edge can eliminate the separation bubble at the pressure side of the tip clearance. Also, it can affect the tip clearance outflow by changing the reversed flow. As a result, the leakage flow is increased and the compressor performance is decreased in efficiency and pressure ratio. The local leakage mass flow rate along the camber line can be increased up to 40% when the fillet radius is as much as 20% of the tip clearance size. The flowfield in the downstream is also affected by the fillet edge. By the comparing among the models with different working conditions, it is found that the sensitivity of the performance to the fillet edge is different between design and off-design conditions. Furthermore, the effect of the tip fillet edge on the leakage flow is qualified and compared with the effect of the tip clearance.