| 摘要 |
PURPOSE:To reduce noise by forming a stepped part onto a shroud so that the characteristic frequency of a vane wheel differs from the frequency of the fluid which flows in a volute pump and varying the characteristic frequency of the vane wheel and preventing the resonance by absorbing the vibration and pulsation of fluid. CONSTITUTION:A front-surface shroud 5 has a stepped part 5d between a center part 5b and an outer peripheral part 5c, and if the thickness of the center part 5b is t0 and that of the outer peripheral part 5c is (t), t/t0=0.6. When the relation between the pumping amount of a volute pump and noise level is measured, the characteristic shown by D in the figure is obtained. When the relation in the conventional volute pump is measured under the similar conditions, the characteristic shown by C in the figure is obtained. This comes from the fact that the characteristic frequency shifts largely and the resonance with the vibration of fluid can be prevented, since the stepped part 5d is formed onto the front surface shroud 5, and thus noise can be reduced markedly.
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