Study on flow-induced noise characteristics of multistage depressurization valve in the nuclear power plant

In this study, the flow-induced noise generated by the second-loop main feedwater regulating valve in a nuclear power plant is analyzed. Based on the Ffowcs Williams and Hawkings acoustic analog equation and internal flow characteristics, the noise level and characteristics under monopole, dipole, and quadrupole noise sources are numerically investigated. The results show that the cavitation noise under a monopole noise source, water hammer impact noise under a dipole noise source, and turbulence noise under a quadrupole noise source have a certain influence on the generation and propagation of valve core noise. The maximum noise level is located in the turbulence generation region after the hedge and is about 188 dB. The frequency characteristics of the turbulence noise are obtained through spectrum and octave analyses. The results show that the low and middle frequency bands are narrow, and the sound pressure level (SPL) gradually increases with increasing frequency. The wider the high frequency, the lower the SPL. The continuous broadband frequency characteristics are dominated by the middle and high frequencies. The study results provide some reference for investigating valve noise and designing active noise reduction.