Radial impeller for a drum fan and fan unit having a radial impeller of this type

Abstract

An impeller has an inlet and outlet. A bottom disc has an external diameter. A top disc concentric to the bottom disc at an axial distance therefrom has a suction opening for the inlet. A plurality of forward-curved blades are arranged between the bottom disc and the top disc. A flow channel has an inner inlet side and an outer outlet side formed between adjacent blades. The channel is curved convexly viewed in the running direction of the impeller. The external diameter of the bottom disc is at least 20% greater than the internal diameter of the suction opening. The top disc forms a guiding surface and an angle is formed between a tangent on the guiding surface at the inlet to the suction opening and a tangent on the guiding surface at the outlet from the flow channel on the air outlet side is at least 30°.

What is claimed is: 
     
         1 . A radial impeller having an axial air inlet and an air outlet over an impeller circumference, preferably for use in a spiral housing, the radial impeller comprising:
 a bottom disc which has an external diameter,   a top disc which is arranged concentrically to the bottom disc at an axial distance therefrom and has a circular suction opening with an internal diameter for the axial air inlet, and   a plurality of forward-curved, profiled blades arranged between the bottom disc and the top disc, a flow channel having a radially inner air inlet side and a radially outer air outlet side being formed between two adjacent blades in each case, which channel is curved convexly, viewed in the running direction of the radial impeller, wherein   the external diameter, of the bottom disc, based on the internal diameter of the suction opening, is at least 20% greater than the internal diameter of the suction opening, in that the top disc forms a top guiding surface for the flow channel, an angle which opens towards the inlet opening and is formed between a tangent on the top guiding surface at the inlet to the suction opening of the top disc and a tangent on the top guiding surface at the outlet from the flow channel on the radially outer air outlet side thereof, being at least 30°.   
     
     
         2 . The radial impeller according to  claim 1 , wherein the external diameter of the bottom disc, based on the internal diameter of the suction opening, is at least 50%, but at most 90% greater than the internal diameter of the top disc. 
     
     
         3 . The radial impeller according to  claim 1 , wherein in the profiled blades, a profile thickness ratio of maximum profile thickness to profile overall length is at least 0.15, in particular at least 0.2 and more preferably at least 0.25, the profile thickness ratio being at most 0.5 and in particular 0.4, more preferably 0.35. 
     
     
         4 . The radial impeller according to  claim 1 , wherein an inner radius on the leading edge of the blades in the vicinity of the top disc is greater than or equal to the inner radius of the suction opening in the top disc. 
     
     
         5 . The radial impeller according to  claim 1 , wherein an outlet diameter of the blades on the top disc is less than or equal to the external diameter of the top disc and/or is less than or equal to the external diameter of the bottom disc. 
     
     
         6 . The radial impeller according to  claim 1 , wherein a number of blades is at least 19 and at most 54 and is preferably within a range of 22 to 46. 
     
     
         7 . The radial impeller according to  claim 1 , wherein the top disc, the blades and the bottom disc are configured as a composite body consisting of two parts, in particular of two plastics injection-moulded parts which are integrally bonded. 
     
     
         8 . The radial impeller according to  claim 1 , wherein the bottom disc forms a bottom guiding surface in the flow channel. 
     
     
         9 . The radial impeller according to  claim 1 , wherein the top guiding surface and/or the bottom guiding surface of the flow channel have a constant curvature. 
     
     
         10 . The radial impeller according to  claim 1 , wherein in each case the leading edges of the blades on the radially inner air inlet side and/or the trailing edges of the blades on the radially outer air outlet side are rounded. 
     
     
         11 . The radial impeller according to  claim 1 , wherein the cross section of the flow channel tapers from the radially inner air inlet side to the radially outer air outlet side, in particular a shortest distance between the bottom disc and the top disc decreasing in the flow direction. 
     
     
         12 . The radial impeller according to  claim 1 , wherein an impeller outlet width on the radially outer air outlet side of the flow channel has a value which is at most 70% of an overall width of the radial impeller. 
     
     
         13 . The radial impeller according to  claim 1 , wherein the overall width thereof is within a range of 25% to 70%, based on the external diameter of the bottom disc. 
     
     
         14 . The radial impeller according to  claim 1 , wherein the angle which opens out towards the inlet opening and is formed between a tangent on the top guiding surface at the inlet to the suction opening of the top disc and a tangent on the top guiding surface at the outlet from the flow channel on its radially outer air outlet side is at most 90°, preferably at most 75°. 
     
     
         15 . A fan unit, in particular a drum fan, having a radial impeller according to  claim 1 , wherein the radial impeller is arranged in a housing, in particular in a spiral housing. 
     
     
         16 . The fan unit according to  claim 15 , wherein an inlet of the housing for the radial impeller is nozzle-shaped, the inlet of the housing in particular dipping into the suction opening in the top disc. 
     
     
         17 . The fan unit according to  claim 15 , wherein a ratio of a width of the housing at the air inlet opening thereof into an air guiding channel to an impeller outlet width of the radial impeller at the radially outer air outlet side of the flow channel has a value within a range of 1.0≦V B ≦1.4. 
     
     
         18 . The fan unit according to  claim 15 , wherein the radial impeller is arranged in the housing coaxially with an electric drive motor, an outer contour of the drive motor engaging positively in a motor receiving opening in the bottom disc or being covered by a full-surface bottom disc, and the bottom disc, preferably together with the contour of the motor received in the motor receiving opening thereof, having a dome-shaped formation. 
     
     
         19 . The fan unit according to  claim 15 , wherein the housing has an air guidance channel, wound spirally around the radial impeller, with an oval cross section which increases constantly from the side of the radial impeller.