US20160319836A1 - Axial flow fan with blades twisted according to a blade pitch ratio that decreases (quasi) linearly with the radial position - Google Patents

Axial flow fan with blades twisted according to a blade pitch ratio that decreases (quasi) linearly with the radial position Download PDF

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Publication number
US20160319836A1
US20160319836A1 US15/105,458 US201315105458A US2016319836A1 US 20160319836 A1 US20160319836 A1 US 20160319836A1 US 201315105458 A US201315105458 A US 201315105458A US 2016319836 A1 US2016319836 A1 US 2016319836A1
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United States
Prior art keywords
fan
hub
axis
blade
blades
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Abandoned
Application number
US15/105,458
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English (en)
Inventor
Karl Erik WIDELL
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DACS AS
Original Assignee
DACS AS
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Assigned to DACS A/S reassignment DACS A/S ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: WIDELL, Karl Erik
Publication of US20160319836A1 publication Critical patent/US20160319836A1/en
Abandoned legal-status Critical Current

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    • 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.
  • ⁇ ⁇ ⁇ ⁇ arc ⁇ ⁇ tan ( 1.2 ⁇ R r - 0.2 ⁇ ) - 50.4 ⁇ °
  • 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.
  • ⁇ ⁇ ⁇ ⁇ arc ⁇ ⁇ tan ( 1.2 ⁇ R r - 0.2 ⁇ ) - 41.7 ⁇ °
  • 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
  • ⁇ arctan [ 1 15 ⁇ ⁇ ⁇ 2 ⁇ Flow nD 3 [ 1.46 r R + 0.564 ⁇ r R - 0.77 ] ]
  • R is the radial distance from the axis and to the free tip end of the blade
  • r is the radial distance from the axis and to the radial position
  • Flow is the nominal flow for the fan given in [m 3 /h]
  • n is the nominal rotational speed of the fan given in [rpm].
  • the fan according to the second aspect of the present invention will, when operating near the nominal operational conditions 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.
  • 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. 2 a shows the tangential flow speed of a fan designed according to the invention
  • FIG. 2 b 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 .
  • 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.
  • h 1,h is the total enthalpy of the air immediately before the rotor 5
  • c p is the heat capacity of the air
  • t 1 is the temperature of the air immediately before the rotor 5
  • c 1 is the air speed immediately before the rotor 1
  • h 0 is the total enthalpy of the air at rest far upstream of the fan 1 .
  • 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 inclusion of a forced vortex flow at the core of the flow field after the rotor 5 is a novel design principle of a axial flow fan and provides advantages over the known prior art.
  • 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.
  • Flow is the nominal flow for the fan given in [m 3 /h]
  • n is the nominal rotational speed of the fan given in [rpm].
  • 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.
  • blades 2 of a rotor 5 designed according to the above design principle are provided below at a number of relative radial positions r/R, comprising the chord length, the profile type and the chord angles 0 as determined by means of the design principle, and for comparison the chord angles as calculated by means of equation 1 and equation 2.
  • 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 0 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 to be a temperature of 20° C., a pressure of 101300 Pa and a relative humidity of 80%.
  • 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%.
  • the three examples show that the deviation between designed chord angle ⁇ and the one calculated with the use of Equation 1 is less than 1° at relative radial positions r/R>0.4.
  • the deviation between designed chord angle ⁇ and the one calculated with the use of Equation 2 is somewhat larger in the region near the blade root but is for the overall blade 2 a better approximation, i.e. within about 2°.
  • FIG. 5 The assembly shown in FIG. 5 of a seating part 16 of the hub 3 , three blades 2 and three locking parts 18 for an axial flow fan according to an aspect of the present invention.
  • 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 18 a , 18 b , 18 c where the pin 20 a , 20 b , 20 c are arranged at different positions to define different pitch angles of the blade 2 .
  • the locking parts 18 a , 18 b , 18 c 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)
US15/105,458 2013-12-17 2013-12-17 Axial flow fan with blades twisted according to a blade pitch ratio that decreases (quasi) linearly with the radial position Abandoned US20160319836A1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DK2013/050432 WO2015090318A1 (fr) 2013-12-17 2013-12-17 Soufflante à écoulement axial à pales tournés selon un rapport de pas de pale qui diminue de façon (quasi)linéaire avec la position radiale

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US20160319836A1 true US20160319836A1 (en) 2016-11-03

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US (1) US20160319836A1 (fr)
EP (1) EP3084230A1 (fr)
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170234319A1 (en) * 2014-08-13 2017-08-17 Sectar Solutions Inc Centrifugal ceiling fan
US20170350402A1 (en) * 2014-12-17 2017-12-07 Ziehl-Abegg Se Axial Ventilator

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK179200B1 (en) * 2016-08-25 2018-01-29 Dacs As Improved wing for an axial flow fan
EP3622610A1 (fr) 2017-05-08 2020-03-18 Dacs A/S Système d'alimentation électrique pour soufflerie de ventilation

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5244347A (en) * 1991-10-11 1993-09-14 Siemens Automotive Limited High efficiency, low noise, axial flow fan
US5520515A (en) * 1995-05-23 1996-05-28 Bailsco Blades & Casting, Inc. Variable pitch propeller having locking insert
US5730583A (en) * 1994-09-29 1998-03-24 Valeo Thermique Moteur Axial flow fan blade structure
US5769607A (en) * 1997-02-04 1998-06-23 Itt Automotive Electrical Systems, Inc. High-pumping, high-efficiency fan with forward-swept blades
US6287078B1 (en) * 1998-12-31 2001-09-11 Halla Climate Control Corp. Axial flow fan
US6579063B2 (en) * 2000-11-08 2003-06-17 Robert Bosch Corporation High efficiency, inflow-adapted, axial-flow fan
US7186088B2 (en) * 2004-01-12 2007-03-06 Siemens Vdo Automotive, A Division Of Siemens Canada Limited Low pressure fan with high-flow

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US4569632A (en) * 1983-11-08 1986-02-11 Airflow Research And Manufacturing Corp. Back-skewed fan
US4900229A (en) * 1989-05-30 1990-02-13 Siemens-Bendix Automotive Electronic Limited Axial flow ring fan
DE69228189T2 (de) * 1991-08-30 1999-06-17 Airflow Res & Mfg Ventilator mit vorwärtsgekrümmten schaufeln und angepasster schaufelkrümmung und -anstellung
AU1177495A (en) * 1993-11-12 1995-05-29 Penn Ventilator Co. Inc. Air moving system with optimized air foil fan blades
US7249931B2 (en) * 2002-03-30 2007-07-31 University Of Central Florida Research Foundation, Inc. High efficiency air conditioner condenser fan with performance enhancements

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5244347A (en) * 1991-10-11 1993-09-14 Siemens Automotive Limited High efficiency, low noise, axial flow fan
US5730583A (en) * 1994-09-29 1998-03-24 Valeo Thermique Moteur Axial flow fan blade structure
US5520515A (en) * 1995-05-23 1996-05-28 Bailsco Blades & Casting, Inc. Variable pitch propeller having locking insert
US5769607A (en) * 1997-02-04 1998-06-23 Itt Automotive Electrical Systems, Inc. High-pumping, high-efficiency fan with forward-swept blades
US6287078B1 (en) * 1998-12-31 2001-09-11 Halla Climate Control Corp. Axial flow fan
US6579063B2 (en) * 2000-11-08 2003-06-17 Robert Bosch Corporation High efficiency, inflow-adapted, axial-flow fan
US7186088B2 (en) * 2004-01-12 2007-03-06 Siemens Vdo Automotive, A Division Of Siemens Canada Limited Low pressure fan with high-flow

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20170234319A1 (en) * 2014-08-13 2017-08-17 Sectar Solutions Inc Centrifugal ceiling fan
US10677250B2 (en) * 2014-08-13 2020-06-09 Sectar Solutions Inc. Centrifugal ceiling fan
US20170350402A1 (en) * 2014-12-17 2017-12-07 Ziehl-Abegg Se Axial Ventilator
US10975873B2 (en) * 2014-12-17 2021-04-13 Ziehl-Abegg Se Axial ventilator

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Publication number Publication date
EP3084230A1 (fr) 2016-10-26
WO2015090318A1 (fr) 2015-06-25

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