| 摘要 |
PURPOSE:To reduce the pressure loss of a fan, by preventing leakage and back- flow of fluid by locating outlet ports of an impeller in the vicinity of inlet ports of return passages to oppose with each other, and increasing the sectional area of the return passages gradually from the inlet port toward the outlet port. CONSTITUTION:Since the inner and the outer peripheral portions of an outlet port 13 of an impeller are located in the same plane and the portions of an upper plate 15 for return passages 20 where no opening is formed are juxtaposed in parallel with each other, the velocity distribution of fluid at the outlet port 13 is rendered substantially uniform. The fluid is introduced separately into a plurality of inlet ports 18 formed in the upper plate 15 and passed through divided return passages 20 communicated with respective inlet ports 18. Here, since the sectional area of the return passages 20 is increased gradually in the direction of the fluid flow and guide vanes 17 for defining the return passages 20 are curved substantially in an arcuate form in the direction of rotation of the impeller 7, it is prevented that the flow of fluid introduced from the inlet ports 18 is deflected or curved in a forced manner. |
