GB858808A - Radial-flow fan or pump - Google Patents

Abstract

858,808. Centrifugal fans and pumps. AMME, W., AMME, P., and SELBACH, A., [trading as POLLRICH & CO., P.]. March 6, 1958 [March 12, 1957], No. 7284/58. Class 110 (1). In a centrifugal fan or pump, leakage of fluid through the gap 7, Fig. 4, between the impeller shroud 8 and the inlet nozzle 6 is reduced by retarding the velocity of the boundary layer so as to increase its static pressure at the gap. For this purpose, the inlet nozzle 6 is formed adjacent the gap 7 as a surface of revolution 5 of arcuate cross-section, the chord s of the arc being between 6 and 8 times its height h. The tangent 15 to the end of the arc is at an obtuse angle to the tangent 13 to the arcuate portion 14 of the impeller shroud 8. Tangent 13 is approximately parallel to the impeller axis and is located at the narrowest part of the gap 7. This construction prevents detachment of the turbulent boundary layer from the surface 5 by shifting the place at which it would have detached to a point slightly downstream of the gap 7, to ensure that the maximum pressure increase due to retardation of the boundary layer flow occurs at the gap. The required turbulence in the boundary layer may, if necessary, be promoted by a wire ring 2 or a weld seam. It is stated that the profile of meridional velocities C m , with minimum values adjacent the shroud 8, remains essentially unaltered until the fluid leaves the impeller, and that the profile is such that flow disturbance in the casing 11 is prevented. The leakage through the gap 7 can be further reduced by providing a projection 12, Fig. 5, the position of which can be adjusted by axial displacement of the nozzle 6.