2013 年 8 巻 1 号 p. 120-135
The main steam stop valve (MSV) in thermal or nuclear power plants is liable to undergo excitation by sound having a specific frequency. The purposes of this article are to clarify the mechanism of the sound generation in the MSV using numerical analysis and to propose a suppression method for the sound generation. The analysis results were validated experimentally using a 1/5-scale model of a typical MSV. The analysis results showed good agreement with the experimental data. From the analysis results, it was clarified that the sound of the MSV was generated by the hole-tone in the opening and the acoustic resonance in the vertical direction of the MSV. A method was proposed to install triangular or slanted tabs at the inlet seat of the MSV in order to prevent formation of vortex rings in the opening which leads to the hole-tone. Effects of the proposed method were tested experimentally. Eight triangular tabs having a height of 15% of the inner diameter in the seat reduced the peak value of the sound pressure by 60%. Eight slanted tabs having a height of 7.5% of the inner diameter in the seat suppressed generation of the hole-tone in the MSV. These results showed that the slanted tabs are effective in suppression of the hole-tone compared with the triangular tabs.
