WO2008025975A1 - Impeller and blade therefor - Google Patents

Impeller and blade therefor Download PDF

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Publication number
WO2008025975A1
WO2008025975A1 PCT/GB2007/003256 GB2007003256W WO2008025975A1 WO 2008025975 A1 WO2008025975 A1 WO 2008025975A1 GB 2007003256 W GB2007003256 W GB 2007003256W WO 2008025975 A1 WO2008025975 A1 WO 2008025975A1
Authority
WO
WIPO (PCT)
Prior art keywords
impeller
blade
blades
tip
shaft
Prior art date
Application number
PCT/GB2007/003256
Other languages
French (fr)
Inventor
Philip Page
Original Assignee
PAGE Philip
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by PAGE Philip filed Critical PAGE Philip
Priority to GB0905202A priority Critical patent/GB2456084A/en
Publication of WO2008025975A1 publication Critical patent/WO2008025975A1/en

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/113—Propeller-shaped stirrers for producing an axial flow, e.g. shaped like a ship or aircraft propeller

Definitions

  • This invention relates to impellers, and in particular to an impeller blade for incorporation into an impeller for use in mixing fluids in a vessel.
  • Impellers and impeller blades thereof are well known and are of many differing designs. Their purpose is to produce a flow of the fluid around the vessel in order to mix or aerate the fluid whereby the fluid becomes homogeneous throughout the vessel.
  • the impeller blades of such impellers in their simplest form may be simple sheets of metal or plastics material, angled to the direction of motion of the impeller blade (the angle of incidence or chord angle). However, such impeller blades usually approximate to aerofoils in order to produce a higher fluid flow through the impeller at reduced power consumption.
  • An improved impeller blade of this type is disclosed in US 4147437.
  • the blade is formed of a sheet of material of constant thickness, trapezoidal in planform, curved from the leading edge to the trailing edge at all radial positions and with the chord angle continuously decreasing from the root to the tip of the blade.
  • the curvature of such blades creates a problem of mounting the blade on the shaft of the impeller.
  • Such mounting is usually by means of a cast or fabricated hub mounted on the shaft, the hub having for each blade a flat surface onto which the blade is secured by bolts. If this is not done accurately, it introduces shear loads on the bolts, which can fail.
  • the production of the curvature of the blades increases the cost of production of the impeller.
  • an impeller that is suitable for stirring fluids of relatively low viscosity such as water, at Reynold's Numbers in excess of 2000.
  • the invention provides an impeller blade formed of an initially flat sheet of material of constant thickness, the blade having a root, a tip, a leading edge and a trailing edge and a bend line extending from a leading position to a trailing position aft and radially outwardly of the leading position.
  • the leading position may be at between 67% of the root chord and 50% of the blade span at the leading edge, preferably at substantially 5% of the blade span at the leading edge.
  • the trailing position may be at between 33% of the tip chord and 36% of the blade span at the trailing edge, preferably at substantially 100% of the blade span at the trailing edge.
  • the included angle of the bend may be between 140° and 170°, and may be substantially 160°.
  • the blade may be trapezoidal in planform.
  • the angle of taper may be between 9° and 13°, and may be substantially 11°.
  • at least a part of the blade may taper towards the tip.
  • the sweepback angle of the leading edge may be between 9° and 13°, and may be substantially 11°.
  • the tapered part thereof may extend from between 25% and 50% of the blade span to the tip, and may extend from between 36% and 41 % of the blade span to the tip.
  • the blade may have a tip fence extending transversely of the blade.
  • the invention also provides an impeller assembly comprising a shaft and a plurality of impeller blades as aforesaid extending radially from the shaft.
  • the impeller may have three blades, and preferably the blades are disposed equi-angularly around the shaft.
  • the impeller assembly may comprise a hub mounted on the shaft, with the blades secured to the hub.
  • the blades may be secured by means of bolts. Alternatively, the blades may be secured to the hub by welding.
  • the blades may be secured to the hub at a root chord angle of between 20° to 60°, preferably substantially 36°, to a plane perpendicular to the axis of the shaft.
  • the impeller may be mounted in a vessel for a fluid to be mixed, and may be mounted to extend vertically downwards from a top of the vessel.
  • Fig. 1 is a plan view of an impeller blade
  • Fig. 2 is a section through a vessel with an impeller incorporating blades of Fig. 1.
  • a blade 10 of generally trapezoidal planform The blade 10 is formed of an initially flat sheet of material, e.g. of steel, aluminium alloy or plastics material.
  • the leading edge 11 has a sweepback angle A of between 9° and 13°, in this case 11°.
  • the trailing edge 12 is mainly perpendicular to the root chord 13, giving the blade 10 a taper angle of 11° over the majority of the blade span S.
  • the trailing edge 12 is cut away at the inboard end 14 so as to be parallel with the leading edge 11.
  • the dimension c may vary between 25% and 50% of the blade span S, in this case 36%.
  • the blade 10 has a bend line 15 extending from a leading position a to a trailing position b aft and radially outwardly of the leading position a.
  • the leading position a may be at between 67% of the root chord 13 (point a1) and 50% of the blade span S at the leading edge 11 (point a2), in this case at 5% of the blade span S at the leading edge 11.
  • the trailing position b may be at between 33% of the tip chord 16 (point b1) and 36% of the blade span S at the trailing edge 12 (point b2), in this case at the junction of the trailing edge 12 and the tip chord 16, i.e. at 100% of the blade span S at the trailing edge 12.
  • point b is always chosen to be aft and outboard of point a.
  • the angle through which the blade 10 is bent along the bend line 15 may be between 10° and 40°, giving an included angle of the bend between 140° and 170°, and in this case is 160°. To either side of the bend line 15, the blade 10 is flat.
  • a tip fence 17 is formed at the tip 16 by bending the blade 10 through 90 °.
  • the blade 10 has holes 18 for attachment to a hub of an impeller, as described below.
  • the impeller 21 has a shaft 22 on which is mounted a tubular hub 23.
  • the hub 23 may be of cast metal or fabricated.
  • the upper surface of each boss 24 is flat to enable mounting of a blade 10 by means of bolts 25.
  • the top surface of each boss 24 is inclined at an angle to a plane perpendicular to the axis of the shaft 22 to provide a root chord angle for the blade 10. This root chord angle is between 20° and 60°, in this case 36°, to a plane perpendicular to the axis of the shaft 22.
  • the tip chord angle lies between 0° and 44°, and with the abovementioned preferred dimensions and angles, is 16°.
  • Each blade 10 is attached to the respective boss 24 by means of three bolts 25, although the blade 10 may be secured to the boss 24 by more bolts 25 or by welding if preferred.
  • an impeller blade is provided that is simple and inexpensive to manufacture and to attach to the hub of an impeller.
  • Other embodiments of impeller and impeller blade therefor in accordance with the invention will be readily apparent to persons skilled in the art.
  • more or less than three blades may be mounted on the shaft of the impeller.
  • Blades may be mounted on the shaft at different axial positions along the shaft, particularly for relatively tall vessels.
  • the impeller may be mounted to extend from a side of the vessel laterally of the-vessel for certain applications.

Landscapes

  • Engineering & Computer Science (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

An impeller blade formed of an initially flat sheet of material of constant thickness, the blade having a root (13), a tip(16), a leading edge (11) and a trailing edge (12) and a bend line (15) extending from a leading position (a) to a trailing position (b) aft and radially outwardly of the leading position (a).

Description

IMPELLER AND BLADE THEREFOR
This invention relates to impellers, and in particular to an impeller blade for incorporation into an impeller for use in mixing fluids in a vessel.
Impellers and impeller blades thereof are well known and are of many differing designs. Their purpose is to produce a flow of the fluid around the vessel in order to mix or aerate the fluid whereby the fluid becomes homogeneous throughout the vessel. The impeller blades of such impellers in their simplest form may be simple sheets of metal or plastics material, angled to the direction of motion of the impeller blade (the angle of incidence or chord angle). However, such impeller blades usually approximate to aerofoils in order to produce a higher fluid flow through the impeller at reduced power consumption. An improved impeller blade of this type is disclosed in US 4147437. In that case, the blade is formed of a sheet of material of constant thickness, trapezoidal in planform, curved from the leading edge to the trailing edge at all radial positions and with the chord angle continuously decreasing from the root to the tip of the blade. The curvature of such blades creates a problem of mounting the blade on the shaft of the impeller. Such mounting is usually by means of a cast or fabricated hub mounted on the shaft, the hub having for each blade a flat surface onto which the blade is secured by bolts. If this is not done accurately, it introduces shear loads on the bolts, which can fail. In addition, the production of the curvature of the blades increases the cost of production of the impeller.
It is an object of the present invention to provide an impeller assembly, and an impeller blade therefor, that is simple and inexpensive to produce, and which can be simply mounted on the impeller shaft. In particular it is an object of the present invention to provide such an impeller that is suitable for stirring fluids of relatively low viscosity such as water, at Reynold's Numbers in excess of 2000.
The invention provides an impeller blade formed of an initially flat sheet of material of constant thickness, the blade having a root, a tip, a leading edge and a trailing edge and a bend line extending from a leading position to a trailing position aft and radially outwardly of the leading position.
The leading position may be at between 67% of the root chord and 50% of the blade span at the leading edge, preferably at substantially 5% of the blade span at the leading edge. The trailing position may be at between 33% of the tip chord and 36% of the blade span at the trailing edge, preferably at substantially 100% of the blade span at the trailing edge. The included angle of the bend may be between 140° and 170°, and may be substantially 160°.
The blade may be trapezoidal in planform. The angle of taper may be between 9° and 13°, and may be substantially 11°. Alternatively, at least a part of the blade may taper towards the tip. In either case, the sweepback angle of the leading edge may be between 9° and 13°, and may be substantially 11°. The tapered part thereof may extend from between 25% and 50% of the blade span to the tip, and may extend from between 36% and 41 % of the blade span to the tip.
The blade may have a tip fence extending transversely of the blade.
The invention also provides an impeller assembly comprising a shaft and a plurality of impeller blades as aforesaid extending radially from the shaft. The impeller may have three blades, and preferably the blades are disposed equi-angularly around the shaft. The impeller assembly may comprise a hub mounted on the shaft, with the blades secured to the hub. The blades may be secured by means of bolts. Alternatively, the blades may be secured to the hub by welding. The blades may be secured to the hub at a root chord angle of between 20° to 60°, preferably substantially 36°, to a plane perpendicular to the axis of the shaft.
The impeller may be mounted in a vessel for a fluid to be mixed, and may be mounted to extend vertically downwards from a top of the vessel.
The invention will now be described with reference to the accompanying drawings in which Fig. 1 is a plan view of an impeller blade, and Fig. 2 is a section through a vessel with an impeller incorporating blades of Fig. 1.
Referring now to Fig. 1 there is shown a blade 10 of generally trapezoidal planform. The blade 10 is formed of an initially flat sheet of material, e.g. of steel, aluminium alloy or plastics material. The leading edge 11 has a sweepback angle A of between 9° and 13°, in this case 11°. The trailing edge 12 is mainly perpendicular to the root chord 13, giving the blade 10 a taper angle of 11° over the majority of the blade span S. However, the trailing edge 12 is cut away at the inboard end 14 so as to be parallel with the leading edge 11. The dimension c may vary between 25% and 50% of the blade span S, in this case 36%.
The blade 10 has a bend line 15 extending from a leading position a to a trailing position b aft and radially outwardly of the leading position a. The leading position a may be at between 67% of the root chord 13 (point a1) and 50% of the blade span S at the leading edge 11 (point a2), in this case at 5% of the blade span S at the leading edge 11. The trailing position b may be at between 33% of the tip chord 16 (point b1) and 36% of the blade span S at the trailing edge 12 (point b2), in this case at the junction of the trailing edge 12 and the tip chord 16, i.e. at 100% of the blade span S at the trailing edge 12. However, within the ranges specified, point b is always chosen to be aft and outboard of point a. The angle through which the blade 10 is bent along the bend line 15 may be between 10° and 40°, giving an included angle of the bend between 140° and 170°, and in this case is 160°. To either side of the bend line 15, the blade 10 is flat.
To prevent or minimise flow of fluid around the tip 16, a tip fence 17 is formed at the tip 16 by bending the blade 10 through 90 °. The blade 10 has holes 18 for attachment to a hub of an impeller, as described below.
Referring now to Fig. 2, there is shown a vessel 20 in which an impeller 21 is mounted to extend in a vertical direction. The impeller 21 has a shaft 22 on which is mounted a tubular hub 23. The hub 23 may be of cast metal or fabricated. Formed with the hub 23 are bosses 24, three being shown in this case. The upper surface of each boss 24 is flat to enable mounting of a blade 10 by means of bolts 25. The top surface of each boss 24 is inclined at an angle to a plane perpendicular to the axis of the shaft 22 to provide a root chord angle for the blade 10. This root chord angle is between 20° and 60°, in this case 36°, to a plane perpendicular to the axis of the shaft 22. The tip chord angle lies between 0° and 44°, and with the abovementioned preferred dimensions and angles, is 16°. Each blade 10 is attached to the respective boss 24 by means of three bolts 25, although the blade 10 may be secured to the boss 24 by more bolts 25 or by welding if preferred.
By means of the invention, an impeller blade is provided that is simple and inexpensive to manufacture and to attach to the hub of an impeller. Other embodiments of impeller and impeller blade therefor in accordance with the invention will be readily apparent to persons skilled in the art. For example, more or less than three blades may be mounted on the shaft of the impeller. Blades may be mounted on the shaft at different axial positions along the shaft, particularly for relatively tall vessels. The impeller may be mounted to extend from a side of the vessel laterally of the-vessel for certain applications.

Claims

1. An impeller blade formed of an initially flat sheet of material of constant thickness, the blade having a root, a tip, a leading edge and a trailing edge and a bend line extending from a leading position to a trailing position aft and radially outwardly of the leading position.
2. An impeller blade as claimed in claim 1 , wherein the leading position is at between 67% of the root chord and 50% of the blade span at the leading edge.
3. An impeller blade as claimed in claim 2, wherein the leading position is at substantially 5% of the blade span at the leading edge.
4. An impeller blade as claimed in any one of claims 1 to 3, wherein the trailing position is at between 33% of the tip chord and 36% of the blade span at the trailing edge.
5. An impeller blade as claimed in claim 4, wherein the trailing position is at substantially 100% of the blade span at the trailing edge.
6. An impeller blade as claimed in any one of claims 1 to 5, wherein the included angle of the bend is between 140° and 170°.
7. An impeller blade as claimed in claim 7, wherein the included angle of the bend is substantially 160°.
8. An impeller blade as claimed in any one of claims 1 to 7, wherein the blade is trapezoidal in planform.
9. An impeller blade as claimed in claim 8, wherein the angle of taper is between 9° and 13°
10. An impeller blade as claimed in claim 9, wherein the angle of taper is substantially 11°.
11. An impeller blade as claimed in claim 9 or claim 10, wherein a part of the blade tapers towards the tip.
12. An impeller blade as claimed in any one of claims 8 to 11 , wherein the sweepback angle of the leading edge is between 9° and 13°.
13. An impeller blade as claimed in claim 12, wherein the sweepback angle of the leading edge is substantially 11°.
14. An impeller blade as claimed in any one of claims 9 to 13, wherein the tapered part of the blade extends from between 25% and 50% of the blade span to the tip, and may extend from between 36% and 41 % of the blade span to the tip.
15. An impeller blade as claimed in any one of claims 1 to 14, wherein the blade has a tip fence extending transversely of the blade.
16. An impeller comprising a shaft and a plurality of impeller blades as claimed in any one of claims 1 to 15 extending radially from the shaft.
17. An impeller as claimed in claim 16, having three blades.
18. An impeller as claimed in claim 16 or claim 17, wherein the blades are disposed equi- angularly around the shaft.
19. An impeller as claimed in any one of claims 16 to 18, comprising a hub mounted on the shaft, with the blades secured to the hub.
20. An impeller as claimed in claim 19, wherein the blades are secured by means of bolts.
21. An impeller as claimed in claim 19, wherein the blades are secured to the hub by welding.
22. An impeller as claimed in any one of claims 19 to 21 , wherein the blades are secured to the hub at a root chord angle of between 20° to 60° to a plane perpendicular to the axis of the shaft.
23. An impeller as claimed in claim 22, wherein the blades are secured to the hub at a root chord angle of substantially 36° to a plane perpendicular to the axis of the shaft.
24. An impeller as claimed in any one of claims 16 to 23, wherein the impeller is mounted in a container for a fluid to be mixed.
25. An impeller as claimed in claim 24, wherein the impeller is mounted to extend vertically downwards from a top of the container.
26. An impeller blade substantially as hereinbefore described with reference to and as illustrated in Fig. 1 of the accompanying drawing.
27. An impeller substantially as hereinbefore described with reference to and as illustrated in Fig. 2 of the accompanying drawing.
PCT/GB2007/003256 2006-08-29 2007-08-29 Impeller and blade therefor WO2008025975A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB0905202A GB2456084A (en) 2006-08-29 2007-08-29 Impeller and blade therefor

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0617041.9 2006-08-29
GBGB0617041.9A GB0617041D0 (en) 2006-08-29 2006-08-29 Impeller and blade therefor

Publications (1)

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WO2008025975A1 true WO2008025975A1 (en) 2008-03-06

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Family Applications (1)

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WO (1) WO2008025975A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9334874B2 (en) 2012-02-20 2016-05-10 Outotec (Finland) Oy Blade of axial flow impeller and axial flow impeller
US10105663B2 (en) * 2014-04-04 2018-10-23 Milton Roy Europe Stirring propeller with blades made of sheet bent along two longitudinal bends

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1600744A (en) * 1968-12-11 1970-07-27
WO1991011620A1 (en) * 1990-01-29 1991-08-08 Chemineer, Inc. High efficiency mixer impeller
US5297938A (en) * 1990-03-26 1994-03-29 Philadelphia Mixers Corporation Hydrofoil impeller
DE9418136U1 (en) * 1994-11-11 1994-12-22 Stelzer Rührtechnik GmbH, 34414 Warburg Stirrer
US5951162A (en) * 1997-03-14 1999-09-14 General Signal Corporation Mixing impellers and impeller systems for mixing and blending liquids and liquid suspensions having efficient power consumption characteristics

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1600744A (en) * 1968-12-11 1970-07-27
WO1991011620A1 (en) * 1990-01-29 1991-08-08 Chemineer, Inc. High efficiency mixer impeller
US5297938A (en) * 1990-03-26 1994-03-29 Philadelphia Mixers Corporation Hydrofoil impeller
DE9418136U1 (en) * 1994-11-11 1994-12-22 Stelzer Rührtechnik GmbH, 34414 Warburg Stirrer
US5951162A (en) * 1997-03-14 1999-09-14 General Signal Corporation Mixing impellers and impeller systems for mixing and blending liquids and liquid suspensions having efficient power consumption characteristics

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9334874B2 (en) 2012-02-20 2016-05-10 Outotec (Finland) Oy Blade of axial flow impeller and axial flow impeller
US10105663B2 (en) * 2014-04-04 2018-10-23 Milton Roy Europe Stirring propeller with blades made of sheet bent along two longitudinal bends

Also Published As

Publication number Publication date
GB2456084A (en) 2009-07-08
GB0617041D0 (en) 2006-10-11
GB0905202D0 (en) 2009-05-13

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