Abstract: To analyze the effects of the cascade pressure pulsation on the flow-induced noise, the regenerative pump was selected since its irregular cascades, the three-dimensional unsteady flow is simulated based on the RNG k-ε turbulence model. The pressure pulsation on the cascade surface is extracted as the sound source, after the accuracy of the numerical simulation method has been verified by the performance experiment. The indirect boundary element method is employed to solve the external field noise caused by the rotating dipole source. The results show that the pressure pulsation amplitude has the negative relationship with the flow rate, as well as it keeps same direction with the fluid energy increasing along the fluid movement direction, while its relative minimum appears on the position of the tongue region under non-design flow rate mode. The external sound field presents the character of strong dipole, the sound pressure level maintains it local minimum at the design operation, the sound lobes clockwise rotates as the shaft center is its rotating axis under the non-design condition, its magnitude increases in a radial manner, while the degree of the enhancement and rotation improves with the flow rate decreasing. Both the pressure pulsation and flow-induced noise main frequency are the rotation frequency, the secondary frequency of the pressure pulsation are the blade passing frequency and its harmonic frequency, while the secondary frequency of the sound is quite blurred, the sound pressure level curve decreasing tendency turn to slow, its oscillation tends to be more regularly starting at the blade passing frequency. Thus, much more attention should be paid to decrease the cascade flow-induced noise at its rotation frequency when the cascade noise reduction optimization designing.

Key words: cascade, flow-induced noise, pressure pulsation, the regenerative pump, the sound pressure level