Role of blade rotational angle on energy performance and pressure fluctuation of a mixed-flow pump

The role of blade rotational angle in the energy performance and pressure fluctuation of a mixed-flow pump is investigated through an experimental measurement and numerical simulation. The mixed-flow pump head increases at a blade rotational angle of 4 degrees and decreases at a blade rotational angle of -4 degrees compared with a blade rotational angle of 0 degrees. Meanwhile, the highest efficiency decreases by 0.3% at a blade rotational angle of 4 degrees and increases by 0.8% at a blade rotational angle of -4 degrees. The pressure fluctuation characteristics in the mixed-flow pump at different blade rotational angles are also revealed. The dominant frequencies of pressure fluctuations in the impeller are the axis rotation frequency or six times this frequency corresponding to six guide vanes. The dominant frequencies of pressure fluctuations at the middle plane of impeller and guide vane are the blade-passing frequencies or twice this frequency. The maximum amplitude of pressure fluctuation in the impeller at a blade rotational angle of -4 degrees is greater than that of blade rotational angle 0 degrees and 4 degrees because of strong vortex intensity. The maximum amplitude of pressure fluctuation at the middle span of the impeller and vane occurs at a blade rotational angle of 4 degrees because of the largest pressure gradient.