| 摘要 |
PROBLEM TO BE SOLVED: To improve effect of noise reduction while improving air flow efficiency by forming a top end faced to the impeller of a spiral wall formed on the casing of a tangential fan into an elliptic curve surface. SOLUTION: A tangential fan means provided with an impeller having a rotor whose outer diameter is Do , a spiral wall 116 in which a clearance between top end of a top end part 116-1 and a rotor is dgap , and a rear surface wall on which a delivery part acting mutually with the spiral wall 116 is formed, the top end part of the spiral wall 116 is formed into an elliptic curve surface shape having two focuses F-1, F-2. The elliptic curve surface is formed having a long radius Rmajor and a short radius Rminor , which are formed so as to satisfy the relation of 1.1<=Rmajor /Rminor <=6.0, and 0.02<=Rminor /Do <=0.15. A minimum clearance dgap between the spiral wall 116 and the impeller is set within the range of 0.02<=dgap /Do <=0.15. |
