| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a ventilating cover which is capable of reducing noises made by an air flow passing through the ventilating cover. <P>SOLUTION: The ventilating cover 7 is provided with crossbars 6, and the crossbars 6 are each formed into a shape nearly like an airfoil in a cross section in parallel with the flow direction of the air flow, so that the air flow separates less from the crossbars 6, and noises made by the air flow passing through the ventilating cover 7 can be reduced. As to the cross sectional shape of the airfoil (crossbar), a cross-sectional side-length ratio D/H (ratio of chord length D to thickness H) is set at 3 to 5 : 1. The ratio of the thickness H of the crossbar 6 to a space S between the crossbars 6 is set at 1.5 to 3 : 1. The trailing edge angle β of the airfoil is set at 25° or below. The leading edge angle α of the airfoil is set larger than the trailing edge angle β and twice or less as large as the trailing edge angle β. By this setup, large air eddies hardly occur in a rear stream, so that noises caused by the air flow can be reduced. <P>COPYRIGHT: (C)2004,JPO |
