Three-dimensional turbulent flow field in the tip region of an axial-flow fan rotor passage

Turbulent flow field in the tip region of an axial-flow fan rotor was measured using a 3-D LDV(Laser Doppler Velocimetry). The flow was surveyed across the entire passage at seven axial locations (leading edge, 1/6'chord, 1/3 chord, 1/2 chord, 2/3 chord, 5/6 chord and trailing edge) and eight radial locations(0.983, 0.967, 0.942, 0.917, 0.883, 0.833, 0.750 and 0.667 span). The data derived include all three components of mean velocity and turbulence intensity. The measurement results indicated that the tip leakage vortex produces very near the leading edge, and it becomes strongest at the half-chord, then decays rapidly. At the exit of the rotor passage, the leakage vortex exists in mid-passage. In the corner between the casing wall and the pressure surface, the scraping vortex becomes stronger with the flow downstream, leading to more substantial turbulence and blockage. The tip leakage vortex plays a leading role in the tip flow field of the rotor passage, producing most flow turbulence and blockage.