抄録
In our previous reports on underwater gas cutting in various cutting positions, it was suggested that the most important factor having influence on the maximum cut thickness of thick steel plate was the flow velocity of cutting oxygen jet in the kerf. In this report, the velocity of cutting oxygen jet was measured using pitot-tube method under water and in air, for making clear the difference of velocity of jet among those in various cutting positions.
The results obtained are summarized as follows.
(1) The velocity of oxygen jet (U m/s) decreased with the increase of the distance from the cutting tip (X mm), and the relation between U and X was shown as U=kXα (α: decrease coefficient of velocity of jet, k: constant). In case of the free jet, the value of α under water wsa -1.6 in flat position, and -1.3 in horizontal position respectively. The other side, that value in air was -1.0 in the both positions.
(2) The velocity of oxygen jet in the kerf was simulatively measured in the kerf of the acrylic resin model. The value of a was -0.73 in air. And also, it was -0.78 in horizontal and in vertical up position, -0.91 in vertical down position and -0.95 in flat position respectively under water.
(3) It was shown that decrease coefficient of velocity of jet was closely connected with the value of the maximum cut thickness in each cutting position.
