水中及び液体金属中流れ系におけるキャビテーション初生と壊食に関する基礎的研究

概要

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The cavitation erosion in liquid metals is important for the safety and reliability of nuclear reactors and industrial machinery. However, an evaluation method of cavitation erosion in liquid metal has so far not been established. This study clarifies the incipient condition of cavitation in a liquid metal. A cavitating liquid jet test apparatus in a liquid metal was developed. A cavitating liquid jet was issued from an orifice nozzle with a hole of 0.6mm diameter. PbBi-68 was used as liquid metal. The tests were carried out in water using various nozzles with different shapes to obtain the nozzle shape effect on the incipient number and the erosion rate. It was found that the incipient cavitation number in tap water and PbBi-68 is almost the same regardless of the flow velocity. When the cavitation number is defined by an equation as 2(pd-pv)/ρv2 (pd: downstream pressure, pv: vapor pressure, ρ: density, v: throat velocity), the incipient cavitation number becomes a constant regardless of the nozzle shape. Cavitation erosion tests were carried out with different nozzle shapes. It was concluded that the erosion rate can be qualitatively estimated by the output voltage of an acceleration sensor.