Measurements for Reynolds stresses under different inlet prewhirl in centrifugal compressor

The effects of inlet guide vanes (IGV) prewhirl angles on Reynolds stresses in radial gap between impeller and vane diffuser in a centrifugal compressor are experimentally investigated under design condition by X-type hot-film anemometry. The results show that the levels of the turbulence intensity and the Reynolds stresses in the radial gap get the highest under -20° of prewhirl angle, while they are moderate at 0° and the lowest at 20° of prewhirl angles. High levels of Reynolds shear stresses look to be related with high levels of turbulence kinetic energy, or vice versa. In the lengths of 10% and 50% spanwise, at three prewhirl angles, the time-average Reynolds stresses in the radial direction are obviously larger than that in the tangential direction to indicate the significant anisotropy of turbulence. At the impeller outlet, the time-average Reynolds stresses in the radial direction are above 1.5 times larger than those in the tangential direction, and this ratio decreases to 1.25 at the diffuser inlet. However, in the length of 90% spanwise, the turbulence is close to isotropy since the difference of the Reynolds stresses in two directions is less than 10%. The degree of turbulence anisotropy at 0° of prewhirl angle is higher than those under other two prewhirl angles.