キャビテーション噴流による非衝突面の壊食実験

（テーパ加工試験片の結果）

抄録

Cavitation erosion is normally occurred on the surface which the jet impinges; however, cavitation also erode the non-impinged surface, such as the side of the flow passages. To examine whether changing the shape of the flow channels reduce the cavitation erosion, we varied the shape of inner wall of specimens and standoff distance that is the distance between the edge-face of the nozzle outlet and upstream-side end surface of specimens. The experiment was conducted using four types of hollow cylindrical specimens formed tapered bore made of aluminum alloy and a chamber filled hydraulic oil. In addition, the stand-off distance is varied from 10 to 20 mm to investigate the influence of jet length for erosion. In this study, we investigated the cavitation erosion which occurred the inner wall of specimens discharged oil jet using a 3D laser scanning confocal microscope. As a result, in divergent tapered specimens, there was no eroded site in the inner surfaces of them at the all of stand-off distance. In contrast, inner surfaces at the downstream-side end were eroded in the convergent tapered specimens.