EP0167554A1 - Diffuseur pour impulseur de fluide et son procede de fonctionnement - Google Patents

Diffuseur pour impulseur de fluide et son procede de fonctionnement

Info

Publication number
EP0167554A1
EP0167554A1 EP85900155A EP85900155A EP0167554A1 EP 0167554 A1 EP0167554 A1 EP 0167554A1 EP 85900155 A EP85900155 A EP 85900155A EP 85900155 A EP85900155 A EP 85900155A EP 0167554 A1 EP0167554 A1 EP 0167554A1
Authority
EP
European Patent Office
Prior art keywords
impeller
duct
tips
diffuser
blades
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP85900155A
Other languages
German (de)
English (en)
Inventor
Ulric Keith Gerry
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Gerry U K
Original Assignee
Gerry U K
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 Gerry U K filed Critical Gerry U K
Publication of EP0167554A1 publication Critical patent/EP0167554A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
    • F01P5/00—Pumping cooling-air or liquid coolants
    • F01P5/02—Pumping cooling-air; Arrangements of cooling-air pumps, e.g. fans or blowers
    • F01P5/06—Guiding or ducting air to, or from, ducted 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
    • F04D29/40—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
    • F04D29/547—Ducts having a special shape in order to influence fluid flow

Definitions

  • This invention relates to fluid flow diffusers of the type widely employed in association with axial flow impellers to convert kinetic energy in a fluid stream into static pressure.
  • the diffuser commonly has a conical form.
  • the efficiency of such a diffuser form varies with the angle of divergence of the cone, and an included angle of about 15° is regarded as the optimum for many applications. Smaller angles than this increase the length of the diffuser with little further gain in efficiency, while greater angles progressively reduce the efficiency and increase the risk of flow detachment from the wall of the diffuser accompanied by a big loss in diffuser effect- iveness.
  • a diffuser of 15° ' included angle in practice often proves to be a large structure which can be both expensive to manufacture and awkward to accommodate in a given installation.
  • the present invention consists in the provision of a structure upstream of the tips of the blades of an axial flow impeller so as partly to define a space in which a blade tip driven ring vortex turning so as to diffuse the flow which has passed through the said impeller can be established and be maintained in a stable condition.
  • Patent 3 447 741 which involves the action of the tips of the blades of an impeller but does not involve a standing ring vortex
  • British Patents 970 047 and 1 314 819 which concern diffusion by ring vortices but not in direct association with the tips of an impeller.
  • Fig. 1 is a sectional elevation of a bladed impeller mounted coaxially at the junction of two circular ducts of different diameters and showing a ring vortex developed at the tips of the blades of the impeller;
  • Fig. 2 is a sectional elevation of an embodiment of the invention applied to an axial flow fan
  • Figs. 3a, b, c, d are fragmentary sectional elevations of various structures which may be used to partly define a space in which the ring vortex develops; - _>-
  • Fig. 4 is a sectional elevation of an embodiment of the invention applied to a two-stage fan
  • Fig. 5 is a sectional elevation of an embodiment of the invention applied to a fan with upstream guide vanes
  • Figs. 6a, b are sectional elevations of embodi ⁇ ments of the invention applied to fans with downstream guide vanes;
  • Fig. 7 is a sectional elevation of a further example of the invention applied to a fan with down ⁇ stream guide vanes
  • Fig. 8 is a fragmentary partly sectional elevation of an embodiment of the invention applied to a fan for cooling an internal combustion engine
  • Fig. 9 is a sectional elevation of an embodiment of the invention applied to a ducted propeller for use in air
  • Fig. 10 is a fragmentary partly sectional elevation of an embodiment of the invention applied to a marine propeller
  • Figs. 11a, b, c and d are fragmentary sectional views of alternative duct arrangements
  • Figs. 12a, b and c are fragmentary sectional elevations showing alternative impeller blade tip shapes.
  • a bladed impeller 1 driven by a motor 2 is located coaxially at the junction between two ducts 3,4 of which the duct 4 is of larger diameter than the duct 3 and which are joined by an annular C-section member 5 concave towards the duct 4.
  • the diameter of the impeller 1 is slightly greater than that of the smaller duct 3 and the impeller 1 is arranged so that the tips of the blades 6 of the impeller 1 project into a space 7 within duct 4 which on its upstream face, as defined by the direction of the arrow 8, is bounded by the member 5.
  • an axial flow fan which consists of a bladed impeller 12 driven by a motor 13 the two being coaxially mounted, by means of stays or other structure (not shown) in a circular duct 14 which is of substantially greater diameter than that of the impeller 12.
  • the annular member 15 is arranged with its concave side facing the blade tips and the downstream portion of duct -14 as illustrated in the Figure.
  • the annular member behind which the ring vortex forms may have a cross-section other than C-shaped.
  • the annular member has an S-shaped or sinuous cross-section 18 extending inwardly from the duct initially in arcuate convex manner in a downstream facing, rightward, direction, inwardly to a reversely arcuately curved inner portion concave towards the downstream direction and terminating radially inwards of the impeller blade tips 16.
  • the annular member is formed with a linear cross- section 19 at an inclination 24 rearwardly and inwardly of the duct wall towards the blade tips 16.
  • the annular member has a cross-section 20 defined by two linear portions of which the outer extends inwardly at a steep angle and the inner at a less steep angle towards the blade tips 16. Whilst as shown in Figures 3b and 3c the blade tips 16 terminate slightly inwardly of the innermost portions of the annular members 19,20 it will be appreciated that in operation the flow of fluid past the annular member will be such as to cause a well developed vena contracta to form immediat- ely downstream of the annular member.
  • the blade tips 16 are arranged to project outwardly of the boundary of the vena contracta and they generate a free ring vortex as previously described.
  • the angle 24 may be a right -angle and in that of Figure 3c the outer section may be at right angles to the duct wall and to the inner section of the member 20.
  • the annular member has a section 21 of generally J-form with a radially outer section extending radially through the duct wall and being secured between flanges 23 to facilitate assembly and disassembly. The radially inner portion extends rearwardly in arcuate manner, concave towards the downstream direction.
  • the invention may be applied in the manner here- tofore described at each stage of a multistage fan -9-
  • impellers at each stage are shown mounted at the opposite ends of a pair of back-to-back motors 28,29.
  • the upstream impeller 26 is provided with a suitably shaped inlet 30 and an annular casing 31 encloses this impeller and extends rearwards over the motors.
  • the casing 31 Upstream of the second impeller 27 the casing 31 is provided with a short inward tapering conical section 32 which deflects the approaching stream inwards so that the tips of the second impeller 27 can produce a free ring vortex as in the previous examples.
  • a C-section annular member 33 is provided to locate this vortex as previously described.
  • Guidevanes are commonly employed in connection with axial flow fans and these may be placed upstream or downstream of the impeller.
  • the example shown in Figure 5 has vanes 34 upstream of the impeller, which are enclosed within a casing 35.
  • the vortex may be allowed to form outside this casing and behind a C-sectioned annular member 36.
  • a further C-sectioned annular member 37 (shown dashed) may be introduced into the space between the outside duct 38 and the inner casing 35 for the guidevanes 34.
  • the shape of the members 36 and 37 is not limited to C-section.
  • FIGs 6a and 6b two possibilities are illustrated and a third is shown in Figure 7.
  • the guidevanes are enclosed in a short annular duct 39 which is of smaller diameter than the impeller blades the tips 40 which generate a vortex outside the said short duct 39.
  • the short duct is omitted, the flow being free to pass radially outward between the vanes 41 according to the arrows 42.
  • the guidevanes 43 are placed further downstream after the process of diffusion has been largely completed. Combinations of these arrangements may be employed.
  • inlet ducting on the upstream side of the annular member 36 is omitted and it is to be understood that the outer, upstream surface of the annular member 36 which serves on its inner, downstream, side to define the vortex chamber, can serve as an inlet duct to the impeller, as in Figure 7, without the need for extended inlet ducting.
  • FIG 8 An advantageous application of the invention is shown in Figure 8 where a fan used to draw air through a radiator for cooling an internal combustion engine. This is particularly useful in a vehicle where commonly such a fan is mounted in a confined space between the engine and the radiator and there is insufficient room to install a diffuser for pressure recovery.
  • the fan When the fan is mounted directly on the engine it may not be practical to install a close fitting cowl or duct in the plane of the fan blades to prevent recirculation of air because of the differ ⁇ ential movement between the freely mounted engine and the rigidly mounted radiator. Due to these features such fans tend to be inefficient and wasteful of power.
  • the present invention can be applied to these fans due to the very short length of diffuser necessary and the elimination of wasteful recirculation through the main part of the fan disc.
  • a shaped member 44 is fitted behind the radiator 45 to provide an entry nozzle directing the flow into the fan 46 mounted on the engine 47.
  • a C-sectioned annular member 48 is mounted on the end of the shaped member 44 such that the inner lip 49 of the C-section directs the flow into the fan inside the path swept by the blade tips which generate a free ring vortex within the C-section.
  • the outer lip of the C-section is continued rearwards in the form of a short parallel duct 50 past the blades.
  • FIG. 9 an example of an installation suitable for a hovercraft is shown in which a propeller 51 mounted on a pylon 52 above a deck 53 is surrouned by a shroud 54.
  • the internal surface of the shroud is provided with an annular curved concave recess 55 into which the tips of the propeller blades 56 project and in which a blade-tip generated free ring vortex forms as previously described when the propeller rotates in a direction which drives the ambient air in the direction of the arrows 57.
  • the passage from the curved recess to the trailing edge of the shroud 58 may be parallel to or diverge from the common axis 59 of the propeller and shroud or it may converge, as shown at 60 in the drawing.
  • the lower part of the shroud may be attached to the pylon by means of a bracket 61 or otherwise and by radial stays (not shown) . If the propeller is of the variable pitch type sufficient clearance 62 must be provided between the blade tips 56 and the inner lip 63 of the recess to accommodate the movement and any deflect- tion the blade may suffer during operation.
  • FIG 10 a marine installation is shown.
  • the shroud 63 mounted between the underside of the stern S4 and the skeg 65 has an internal cut-out similar to that of the - previous example of Figure 8 with the tips 66 of the propeller blades projecting into it.
  • Shroud forms of this type allow a considerably greater rate of diffusion to be achieved over a given axial length than is possible with a conventional form and the substantial radial clearance between the blade tips and the inner surface of the shroud make installation and removal of the propeller with the shroud in place a good deal easier.
  • the shroud may be of considerably shorter axial length than a corresponding conventional shroud.
  • the invention not only provides improved diffusion but by protecting the tips of the blades provides a safety feature. Such an arrangement finds advantageous application in, for example, high power outboard motors where both performance and safety are important .
  • FIG. 11a The shape of the cross-section of the shroud is not confined to those of Figures 9 and 10 but may be adapted to the requirements of a particular installation for reasons of performance, strength or simplicity of construction.
  • FIGS 11a, b, c Some further examples of shroud cross-sections are shown in Figures 11a, b, c. in the shroud of Figure 11a a faired leading outer end 68 is provided from which an outer duct surface 67 extends rearwardly and inwardly at a shallow inclination, and a forward, upstream facing surface 69 extends inwardly and rearwardly at a steeper general inclination in arcuately convex manner.
  • Rearwardly of the surface 69 is formed the curved recess 55 defining the vortex chamber and merging in faired manner at 63 with the inner end of surface 69.
  • the upper surface of the recess 55 extends rearwardly and inwardly at a slight inclination as an inner duct surface 60 converging with the outer duct surface in faired manner.
  • the outer duct surface 67 extends rearwardly and inwardly in steeper manner than in Figure 11a to define a shorter duct length.
  • the duct 60 is of uniform diameter and at its forward end is formed with an inwardly projecting annular portion 69 of C-section, concave rearwardly.
  • the duct 60 extends rearwardly from a C-section annular member 69 inwardly inclined manner, and at a rear portion is formed with an internal step 73 from which an inner wall surface 74 extends rearwardly as a uniform internal diameter duct section.
  • the flow into the propeller may be far from uniform and it may be desirable to vary the cross-sectional shape of the shroud around its periphery.
  • Both the outside and inside profile may be varied, the former chiefly in relation to the local approach velocity of the fluid and the latter to control the motion of the core of the ring vortex.
  • the core of the vortex may cavitate and it may be desirable to vary the inside profile and in particular the cross-sectional shape or area of the recess to control the cavitation, for example to prevent it collapsing at any point within the shroud :
  • the ring vortex in addition to having the circulatory motion as illustrated by the ellipse 9 in Figure 1 will also have a further rotational motion in the plane of the impeller disc whereby all the fluid in the vortex rotates as an annulus in the same direction as the tips of the impeller blades but at a lower speed.
  • One of the results of this motion as an annulus will be to tend to maintain a vortex of uniform strength right round the periphery, which otherwise might not be the case if the impeller was working in a non-uniform fluid stream.
  • FIG. 12a a portion of the leading part 71 of the blade tip is cut away leaving only the rear part 70 of the tip to generate the vortex.
  • Such an arrangement may be useful with variable pitch blades and if the axis of rotation of the blades is along the radial line shown by the chain dotted line at the leading edge of the tip portion 70 the clearance between the moving and fixed parts will remain substantially constant.
  • Figure 12b the reverse arrangement is adopted with the rear part 70 of the tip cut away leaving only the leading part 71 to energise the vortex. This arrangement may help to reduce the axial distance occupied by the vortex, but it may allow some of the vorticity shed from the rear of the cut-away portion to pass into the diffusing stream.
  • An arrangement with a sloping tip 72 is shown in Figure 12c.
  • the fluid impeller diffuser of the invention can with advantage be used with relatively short diffuser duct length surrounding and extending downstream from the impeller, for example a duct length of between 20 and 50% of the swept diameter of the impeller may be used.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)

Abstract

Un impulseur à pales rotatives (1) est disposé dans l'espace de transition entre un passage d'admission (3) vers une conduite de diffusion (11) à diamètre élargi entourant l'impulseur (1). Une structure annulaire (5) est située en amont des pointes des pales et fait saillie à l'intérieur de la conduite (11) pour définir le passage d'admission et guider dans le cheminement rotatif des pointes des pales le fluide s'écoulant dans la conduite. Celle-ci (11) et la structure (5) définissent partiellement un espace annulaire (7) s'étendant au delà des pointes des pales dans la conduite (11), à l'intérieur de laquelle se forme un tourbillon annulaire (6) entretenu par les pointes des pales, tournant de manière à diffuser l'écoulement traversant l'impulseur (1). La surface en amont de la structure annulaire (5) peut être formée de manière à servir de conduite d'admission à l'impulseur, sans qu'il soit nécessaire d'utiliser une conduite d'admission étendue, et la conduite du diffuseur peut avoir une section transversale de forme autre que circulaire et peut également être courte, par ex. entre 20 et 50 % du diamètre balayé par l'impulseur.
EP85900155A 1983-12-21 1984-12-18 Diffuseur pour impulseur de fluide et son procede de fonctionnement Withdrawn EP0167554A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8334120 1983-12-21
GB838334120A GB8334120D0 (en) 1983-12-21 1983-12-21 Diffusers

Publications (1)

Publication Number Publication Date
EP0167554A1 true EP0167554A1 (fr) 1986-01-15

Family

ID=10553657

Family Applications (1)

Application Number Title Priority Date Filing Date
EP85900155A Withdrawn EP0167554A1 (fr) 1983-12-21 1984-12-18 Diffuseur pour impulseur de fluide et son procede de fonctionnement

Country Status (6)

Country Link
EP (1) EP0167554A1 (fr)
JP (1) JPS61501463A (fr)
AU (1) AU3786685A (fr)
GB (1) GB8334120D0 (fr)
IT (1) IT1179887B (fr)
WO (1) WO1985002889A1 (fr)

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4836148A (en) * 1988-06-13 1989-06-06 General Motors Corporation Shrouding for engine cooling fans
SE8802902L (sv) * 1988-08-16 1990-02-17 Flygt Ab Straalring foer omroerare
US5143516A (en) * 1989-02-06 1992-09-01 Paccar Inc. Recirculation shield and fan shroud assembly
US4927328A (en) * 1989-03-02 1990-05-22 Scoates William D Shroud assembly for axial flow fans
JPH04119395U (ja) * 1991-04-09 1992-10-26 日本サーボ株式会社 軸流フアン
KR980003248A (ko) * 1996-06-25 1998-03-30 구자홍 에어콘 실외기의 팬슈라우드
DE102006047236B4 (de) 2006-10-04 2017-06-29 Mahle International Gmbh Axiallüfter eingerichtet zur Förderung von Kühlluft einer Kühlvorrichtung eines Kraftfahrzeuges
CN106287993B (zh) * 2016-10-24 2021-01-26 北京小米移动软件有限公司 空气净化器及其风道结构
DE102018211808A1 (de) 2018-07-16 2020-01-16 Ziehl-Abegg Se Ventilator und Leiteinrichtung für einen Ventilator
DE102018128813A1 (de) 2018-11-16 2020-05-20 Ebm-Papst Mulfingen Gmbh & Co. Kg Diagonalventilator mit Drallreduzierung am Diagonallaufrad
JP2022546341A (ja) * 2019-08-19 2022-11-04 ホルツァップル マーク 強化された推力リフトおよび推進システム

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2393933A (en) * 1942-02-27 1946-01-29 Poole Ralph Enclosing casing of propellers or impellers
DE1428273C3 (de) * 1964-09-29 1973-01-04 Siemens Ag, 1000 Berlin U. 8000 Muenchen Flügelrad für einen geräuscharmen Axialventilator
US3635285A (en) * 1970-05-11 1972-01-18 Gen Motors Corp Cooling fan
DE2204507A1 (de) * 1972-02-01 1973-08-09 Bosch Gmbh Robert Axialgeblaese
US4329946A (en) * 1979-10-09 1982-05-18 General Motors Corporation Shroud arrangement for engine cooling fan

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8502889A1 *

Also Published As

Publication number Publication date
AU3786685A (en) 1985-07-12
WO1985002889A1 (fr) 1985-07-04
JPS61501463A (ja) 1986-07-17
IT8468274A0 (it) 1984-12-21
GB8334120D0 (en) 1984-02-01
IT1179887B (it) 1987-09-16

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Legal Events

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PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

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Effective date: 19851219

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Effective date: 19870122