Computational Analysis of Unsteady Tip Leakage Flow in an Isolated Axial Compressor Rotor Blade Row

Unsteady flow structure, particularly in blade tip clearance region of turbomachines, is one of the main resources of blade vibrations, undesirable noises and losses which may eventuate to severe rotating stall and surge. So, analysis of flow behavior in tip clearance region is more significant. In this paper, the unsteadiness which caused by blade row tip leakage flow in a low speed axial compressor, is investigated. Analyses are based on results obtained through numerical simulation of unsteady three dimensional viscous flows. Analyses are based on flow simulation utilizing computational fluid dynamic technique. Two different circumstances at design point and near stall condition are considered for investigation and discussion. Tip leakage flow frequency spectrum was studied through surveying instantaneous static pressure signals imposed on blades surfaces. Frequency spectrum Results showed existence of some pressure peaks at near stall conditions. In this case, interaction between main inflow and tip leakage flow lead to unsteadiness. By occurrence of unsteadiness, tip leakage vortex flow starts to fluctuate at a frequency about the blade passing frequency. However, at design condition, flow is more affected by the main inflow instead of the tip leakage flow.