Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/34—Blade mountings
  • F04D29/36—Blade mountings adjustable
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D19/00—Axial-flow pumps
  • F04D19/002—Axial flow fans
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/38—Blades
  • F04D29/384—Blades characterised by form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/26—Rotors specially for elastic fluids
  • F04D29/32—Rotors specially for elastic fluids for axial flow pumps
  • F04D29/38—Blades
  • F04D29/384—Blades characterised by form
  • F04D29/386—Skewed blades
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
  • F04D29/00—Details, component parts, or accessories
  • F04D29/40—Casings; Connections of working fluid
  • F04D29/52—Casings; Connections of working fluid for axial pumps
  • F04D29/54—Fluid-guiding means, e.g. diffusers
  • F04D29/541—Specially adapted for elastic fluid pumps
  • F04D29/545—Ducts

Definitions

• the present invention relates to an axial flow fan having an advantageous design of the rotor blades.
• Axial flow fans are well known in the art and many different designs have been proposed and manufactured in order to improve the performance of the fan, in particular with respect to generation of noise and improved power efficiency. It is an object of the present invention to provide an improved fan design to improve the efficiency of the fan.
• R is the radial distance from the axis and to the free tip end of the blade and r is the radial distance from the axis and to the radial position.
• Such blade has a steeper chord angle ⁇ at the region near the hub and tends to drive the core of the flow right after the rotor in a so-called forced vortex, which appear to improve the efficiency of the fan.
• the angle ⁇ deviates less that 4°, preferably less than 2° from the curve defined by the equation.
• the angle ⁇ deviates less that 4°, preferably less than 2° from the curve defined by the equation.
• an axial flow fan comprising a hub rotatable about an axis, an annular shroud extending concentric with said axis in a radial distance from said hub, a plurality of fan blades connected at a root end to said hub and having a free tip end extending radially towards said shroud, fan driver coupled to said hub and arranged for driving the rotation of said hub around the axis, wherein the angle ⁇ between a direction of rotation of the blades and the chord of the blade at all positions along the radial extent of the blade substantially follows the curve defined as
• an axial flow fan comprising a hub rotatable about an axis, an annular shroud extending concentric with said axis in a radial distance from said hub, a plurality of fan blades connected at a root end to said hub and having a free tip end extending radially towards said shroud, fan driver coupled to said hub and arranged for driving the rotation of said hub around the axis, wherein the blades are designed so that the fan when in operation at nominal operating conditions generates a fluid flow in the immediate vicinity after the blades which comprises a core flow that substantially is a forced vortex flow where the tangential flow speed component is proportional with the radial distance from the axis.
• the existence of such core flow is readily detectable by means of standard fluid flow measurement techniques, such as hot wire anemometry, laser-doppler velocimetry or particle image velocimetry.
• the core flow extends preferably to a radial distance of at least 0.2 times the radial distance from the axis to the tip of blades, preferably the core flow extends in the range of 0.2 to 0.3 times said radial distance.
• the fluid flow in the immediate vicinity after the blades outside the core flow is preferably substantially a free vortex flow where the tangential flow speed component is inversely proportional with the radial distance from the axis to the radial position, whereas the axial flow speed component is substantially constant.
• the inner radius of the annular shroud is in the range of 600 to 1500 millimetres.
• the radius of the hub is preferably in the range of 50 to 75 millimetres which surprisingly has shown to improve the efficiency of the fan considerably, probably due to the reduced disturbance of the wake of the hub.
• a fan according to the present invention preferably comprises a diffuser arranged concentric with said axis at a downstream position of the annular shroud.
• the diffuser has a conical shape with a diffusion angle in the range of 2 to 15° to the axis of rotation of the rotor, preferably in the range of 6 to 10°.
• a fan according to the present invention comprises an inlet part provided with a bellmouth arranged concentric with said axis at an upstream position of the annular shroud.
• an axial flow fan comprising a hub rotatable about an axis, and at least one fan blade connected at a root end to said hub and having a free tip end extending radially away from said axis, the hub comprising a seating part allowing the blade or blades to be arranged in a plurality of blade pitch angles and blade locking part for locking the blade pitch angle of the at least one blade into a specific blade pitch angle, wherein said locking part is designed to lock said blade into one specific blade pitch angle only.
• a loose locking pin is inserted into one of a plurality of openings in the blade root or in the seating part in order to lock the blade pitch in one of a plurality of possible pitch angles.
• the fan comprises one locking part for each of the blades, and in a particularly preferred embodiment, the blades each comprises a recess cooperating with a corresponding pin of the locking part.
• Fig. 1 is a longitudinal schematic cross-section of an axial flow fan
• Fig. 2a shows the tangential flow speed of a fan designed according to the invention
• Fig. 2b shows the axial flow speed of a fan designed according to the invention
• Fig. 3 shows a blade of an axial flow fan according to the invention
• Fig. 4 illustrates a cross-section of a blade together with the flow direction, the direction of blade movement and the angle ⁇ between the blade chord and the direction of movement
• Fig. 5 is a perspective view of a hub part, three blades and three locking parts for an axial flow fan according to an aspect of the present invention.
• Fig. 6 shows three different designs of the locking parts of Fig. 5. DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION
• the axial flow fan 1 of the present invention may be equipped with any convenient number of blades 2.
• a fan 1 having three blades 2 is shown, but it is generally preferred that the rotor 5 of the fan comprises from 3 to 6 blades.
• the axial flow fan 1 as illustrated in Fig. 1 comprises a number of blades 2 connected to a hub 3.
• the rotor 5, i.e. the hub 3 and the blades 2 is rotated about an axis 4 by means of a motor (not shown) arranged in the hub 3 or next to the hub 3 and connected thereto by means of a drive arrangement, e.g. a belt drive.
• the rotor 5 is arranged inside a cylindrical shroud 6 which is concentric arranged about the axis 4 to that there is a clearance between the tip 7 of the blades 2 and the shroud 6.
• the rotation of the rotor 5 drives a flow of air axially through the fan 1 in the direction of the arrow A in Fig. 1.
• the flow path through the fan 1 is illustrated by streamlines 8 indicated in Fig. 1.
• the shroud 6 is preceded by an inlet part 9 arranged upstream of the shroud, i.e. in the direction against the driven flow A, where the inlet part 9 also is concentric with the axis 4 and comprises a bellmouth to smoothen the flow at the inlet part 9 in order to avoid separation of the flow.
• the passage of the air flow through the rotor 5 causes a pressure increase which is further increased by regained part of the as kinetic energy present in of the air flow immediately after the rotor due to the axial velocity component by means of a diffuser 10 arranged downstream of the shroud 6 and concentric with the axis 4.
• the diffuser 10 has a conical shape with an diffusion angle of 8.5° to the centre line, i.e. to the axis 4 of rotation of the rotor 5.
• the blades 2 are attached by their root end 11 to the hub 3, preferably in a manner discussed later.
• the air is accelerated in the inlet part 9 from rest far upstream of the fan 1 to the flow condition immediately before the rotor 5.
• the design of the blades 2 of the fan 1 has the aim and task of forming a rotor 5 which is characterised in that it during operation of the fan 1 generates an air flow immediately after the air flow passage of the rotor 5, which is a combination of two so-called Beltrami flows, i.e. cylindrical flows with constant total enthalpy, see e.g. Michael H. Vavra, Aero-Thermodynamics and Flow in Turbomachines, John Wiley & Sons, Inc. 1960.
• the design principle according to the present invention causes the change in total enthalpy and thereby the work performed by the blades 2 of the rotor 5 on the air flow to be substantially constant over the whole cross-section of the rotor 5 which is advantageous for the efficiency of the rotor 5.
• a forced vortex flow at the core of the flow field after the rotor 5 preferably with a core radius r c in the range of 0.2 to 0.3 the maximum tangential speed in the wake of the rotor 5 is reduced as well as the force of the whirl formed after the hub 3 which have a disadvantageous effect on regaining kinetic energy in the downstream diffuser 10.
• the blades of a fan may be designed by the use of standard fan design tools when design parameters as fan diameter, flow rate and rotational speed of the rotor.
• a cross section of a fan blade 2 is shown in Fig. 4 with indication of the leading edge 12 of the blade 2 as well as the trailing edge 13 and the chord line 14 extending there between, the length of the chord of the blade 2 being the distance between the leading edge 12 and the trailing edge 13. The blade 2 is moved in the direction indicated as M on Fig.
• the Flow is designed to be 45000 m 3 /h, the nominal rotational speed n is 425 rpm and the radius R of the rotor 5 is 1.5 m.
• the condition of the air is taken to be a temperature of 20 °C, a pressure of 101300 Pa and a relative humidity of 80%.
• the first five columns of the table provide the parameters of the blade 2 as found by standard design tools, whereas the last two columns are the chord angles ⁇ found by means of equation 1 and equation 2, respectively.
• the Flow is designed to be 16000 m 3 /h, the nominal rotational speed n is 970 rpm and the radius R of the rotor 5 is 0.5 m.
• the condition of the air is taken temperature of 20 °C, a pressure of 101300 Pa and a relative humidity of
• the Flow is designed to be 22500 m 3 /h, the nominal rotational speed n is 950 rpm and the radius R of the rotor 5 is 0.5 m.
• the condition of the air is taken to be a temperature of 20 °C, a pressure of 101300 Pa and a relative humidity of 80%. r/R R ⁇ Chord Profile ⁇ Eq. (1) ⁇ Eq. (2)
• the blades 2 are at the root end 11 equipped with a projection 15 that allows the individual blade 2 to be seated in a blade seating opening 17 of the seating part 16 at any pitch angle of the blade 2 as desired, the projections 15 being rotatable in the U-shaped seating openings 17.
• the blade root protections 15 being equipped with a recess (not visible) designed for cooperating with a pin 20 having a rectangular cross-section, the pin 20 being extending from the body of a locking part 18 which is suited to the inserted into the blade seating opening 17 when the blade root projection 15 is in place so as to lock the pitch angle of the blade 2 to a specific blade pitch angle defined by the locking part 18.
• Fig. 6 is shown three different locking parts 18a, 18b, 18c where the pin 20a, 20b, 20c are arranged at different positions to define different pitch angles of the blade 2.
• the locking parts 18a, 18b, 18c are provided with side tracks 19 to accommodate the edges of the blade seating opening 17 of the seating part 16 of the hub 3.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)

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• 2013
  • 2013-12-17 US US15/105,458 patent/US20160319836A1/en not_active Abandoned
  • 2013-12-17 WO PCT/DK2013/050432 patent/WO2015090318A1/en active Application Filing
  • 2013-12-17 EP EP13811779.1A patent/EP3084230A1/de not_active Withdrawn

Patent Citations (2)

Non-Patent Citations (1)

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