| 摘要 |
PURPOSE:To reduce the sectional area of a penetrating part of a blast duct through a beam part by providing, in the front and rear of the piercing part, inclined parts and the diameters of which are made smaller toward the piercing part to produce a coander spiral flow at the penetrating part. CONSTITUTION:A blast duct 2 pierces through a beam 1, and inclined parts 4 and 5 are provide so as to make smaller the diameter of the blast duct toward a piercing part 3. In order to produce a spiral flow, it may be sufficient to normally set the taper of a slit 6 to approximately 1/20-1/3, and to send air into the duct 2. The pressure of compressed air may be set to 1-10kg/cm<2>. Thus, it is possible to make minimum the through sectional area of the blast duct piercing through the beam part. It is, a mater of course, to remarkably reduce a pressure loss by 1/3 or more.
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