GB2226081A

GB2226081A - Fluid friction pump or turbine

Info

Publication number: GB2226081A
Application number: GB8829126A
Authority: GB
Inventors: Stuart James Kirby
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1988-12-14
Filing date: 1988-12-14
Publication date: 1990-06-20
Also published as: GB8829126D0

Abstract

Known shear force pumps and turbines comprise a number of very thin, separately manufactured plates, mounted on a hollow spindle with spaces between each pair of adjacent plates. Apertures are provided in the wall of the spindle to allow a flow of fluid from the spindle interior to atmosphere or vice versa, via the spaces between the plates. The present invention obviates the separate plates, their spacers and the spindle by forming a corresponding part which is a continuous helix. The helix is formed by flanks 22 in a tubular body 10 mounted for rotation in a casing 16. By means of studs or bolts 32 (Fig 3) the helix is strengthened and its pitch may be adjusted. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO SHEAR FORCE FLUID DEVICES This invention relates to a shear force fluid device wherein a shear force is generated either to mdve a fluid through the device or to move the device as a result of passage of the fluid through the device.

More specifically the invention relates to shear force pumps and turbines.

Shear force pumps and turbines of a particular general construction are well known, ie the construction consists of a number of separately constructed discs co-axially mounted on a tubular axle for rotation therewith. The discs are axially spaced from each other by spacers and the resulting spaces therebetween are in flow communication with the bore of the axle. The whole is rotatably mounted in a casing which has a fluid passage which is also in communication with the spaces between the discs.

If the device is to be used as a pump, the assembly is immersed in a fluid to be pumped and the discs are rotated at a high speed. A shear force is thus generated by the movement of the flanks of the discs through the fluid, which is thrown from between the discs and into the fluid passage in the casing, to be replaced by fluid from the fluid source which is induced into the bore of the axle.

If the device is to be used as a turbine, the fluid flow is reversed, by forcing a fluid out of the fluid passage in the casing onto and between the opposing faces of the discs, and therefore into the bore of the axle. The shear force generated by the action of the fluid on the flanks of the discs, effects rotation of the discs and associated axle, which can be connected to drive a compressor or some other device.

The present invention seeks to provide a shear force fluid flow device of improved construction.

According to the present invention a shear force fluid device comprises a tubular body having a helical portion intermediate its ends and being rotatably mounted in a casing, said casing having a fluid passage therein which in operation is in fluid flow communication with the bore of said tube via said helix, and wherein in one mode of operation, said casing and body are immersed in a' fluid with said bore exposed thereto and said body is rotated so that the flanks of said helix generate a shear force on the fluid and drive it into said passage in said casing and, in another mode of operation, fluid is driven into said helix via said passage in said casing, and generates a shear force on the flanks of said helix which effects rotation of the body.

The invention will now be described, by way of example and with reference to the accompanying drawings in which: Figure 1 is a part cross sectional view of a shear force pump and casing in accordance with the present invention.

Figure 2 is a pictorial view of the shear force pump of figure 1.

Figure 3 is a part view of a further embodiment of the present invention.

Figures 4 to 6 are further embodiments of the present invention.

Referring to figure 1. A shear force pump body 10 is in the form of a cylindrical tube. Each end 12, 14 of the body is reduced and projects through a respective end of a casing 16 within which the body 10 resides.

In operation, the body 10 rotates about its own axis, so a bearing arrangement (not shown) is provided at each of its ends, which bearings are supported (not shown) by the casing 16. Further, as the pump is intended to move fluids, appropriate seals are provided, though not shown. Neither the seals or bearings are considered as part of the present invention, and may be conventional structure.

A helix 18 is formed in the pump body 10 over a distance intermediate its ends. The depth of the helix is sufficient to break into the bore 20 of the body 10. The pitch of the helix 18 is fine and in one embodiment of the invention, its profile is over square ie the tool which is used to form the helix 18 is moved into the body 10 only in a direction radially thereof, for a distance which ensures break through into the bore 20. This distance is considerably greater than the pitch of the helix and provides faces 22.

The breakthrough of the root of the helix 18 into the bore 20 enables communication between the bore 20 and the casing 16 via the passages which are defined by the opposing flanks 22 of the helix 18.

In operation, a fluid to be pumped is brought into communication with the bore 20, either by conduits (not shown) being connected to the ends of the pump body 10 and to fluid, or by immersion of the pump 10 and casing 16 in the fluid.

The pump body 10 is then rotated at a selected speed, by any convenient power means (not shown). There results a flow of fluid from the supply source into the bore 20, through the helix 18 in an effectively radial direction, into the casing 16 and out of the casing 16 via a diffusing passage 24. The shear force which the pump body 10 exerts on the fluid, is generated by the flanks 22 of the helix 18 as they rotate therein.

The helix 18 will also impart an axial component of force on the fluid, the axial direction of which will depend on the direction of rotation of the pump body 10. In order to maintain the dynamic head which is imported by the shear force to the fluid on its way through the helix 18, it may be necessary to position the diffuser 24 at or near that end of the casing 16 towards which the fluid is driven.

Referring to figure 2. The helix 18 is seen as a structure which is similar to a flat section coil spring.

The bore 20 is represented by thin lands 20a and the helical opening created by the break through of the forming tool into the bore 20, is indicated by the numeral 26.

The flow of fluid is indicated by the arrows 28 and 30.

Referring now to figure 3. A further advantage which the helix 18 affords by virtue of its springlike form, is the ability to vary the spacing of the faces 22 ie the pitch of the helix, to take account of varying viscosity in the fluid to be pumped. The magnitude of the adjustment will depend on the material from which the pump body 10 is made, but in any event can be brought about by the provision of bolts 32, at least three of which are passed through the pump body 10 in the manner shown. The bolts 32, should also be spaced equiangularly about the axis of rotation of the body 10. Tightening of nuts 34 on the ends of the bolts 32 will cause the helix 18 to close up ie reduce the pitch to achieve desired spacing of the faces 22 of the helix 18.

Alternatively, but not shown, the helix could be extended from a minimum setting, by the substitution of studs, the head ends of which would screw into one end of the body 10, and landed portions of which would pass through the helix 18, to abut the last face 22 which is formed on the opposing end of the pump body ;0. Screwing of the studs inwardly of the body 10, would force the opposing end axially away and thus extend the helix 18.

The bolts 32 or the studs (not shown) if used, will also serve to stiffen the helix 18 against bending under operating loads. If the studs (not shown) are used, the free ends of the landed portions should be recessed into the last face 22, so as to abut the bottom of the recess, rather than abut the last face 22.

Further alternative arrangements of the present invention provide (a) a helix produced entirely as an internal thread which does not break through the outer diameter. The diameter (i.e. land 36) however, has radial perforations therein, to allow compressed fluid therethrough.

(b) a helix which does not break into the bore, but the remaining wall thickness of the bore has perforations therethrough for the passage of expanding fluid into the bore.

(c) an internal helix and an external helix, seperated by a land which has perforations therethrough. This arrangement could act as both compressor, and turbine, as desired.

In each of Figures 4 to 6, the lands are identified by the numeral 36. The lands 36 could replace the pins 32 or studs (not shown).

In the event that the adoption of pins 32 or the studs (not shown) in order to achieve variation in helix pitch proves unsatisfactory as regards rigidity of the assembly, then by sacrificing the pitch variation ability and instead fixing the pins 32 or studs (not shown) to the helix along its axial length, the appropriate rigidity will be achieved.

Further, the positioning of the pins or studs close to the bore or close to the periphery will depend on whether the device is used as a pump or as a turbine, since each use applies the loads differently.

In the case of a shear force turbine, fluid is pumped by an external source, through the casing 16 and into the helix 18. The momentum of the fluid as it strikes the flanks 22 of the helix 18 before passing into the bore 20, generates a shear force which rotates the body 10, which in turn, may eg be coupled to drive a compressor.

Claims

Claims:

1. A shear force fluid flow device comprising a tubular body having a helical portion intermediate its ends and being rotatably mounted in a casing, said casing having a fluid passage therein which in operation is in fluid flow communication with the bore of said tube via said helix, and wherein in one mode of operation, said casing and body are immersed in a fluid with said bore exposed thereto and said body is rotated so that the flanks of said helix generate a shear force on the fluid and drive it into said helix via said passage in said casing and, in another mode of operation fluid is driven into said helix via said passage in said casing, and generates a shear force on the flanks of said helix which effects rotation of the body.

2. A shear force fluid flow device as claimed in claim 1 wherein the helix is springlike in form, in that its roots break into the bore so as to enable said flow communication between the bore and said passage via helix.

3. A shear force fluid flow device as claimed in claim 1 wherein the helix is formed with lands between its flanks, which lands have local perforations drilled through so as to enable said flow communication between the bore and said passage via said helix.

4. A shear force fluid flow device as claimed in any of claims 1 to 3 and including stiffening means which extend through the helix and are located via their ends in the end portions of said body.

5. A shear force fluid flow device as claimed in claim 4 wherein the stiffening means comprises at least three bolts which are equi-angularly spaced about the axis of rotation of the body, the heads of the bolts protruding through the other end face of said body, each bolt being retained by a respective nut.

6. A shear force fluid flow device as claimed in claim 5 when dependant from claim 2 wherein said nut and bolt arrangement enables adjustment of the magnitude of the pitch of said helix from a maximum.

7. A shear force fluid flow device as claimed in claim 4 when dependant from claim 2 wherein the stiffening means comprises at least three landed studs each of which is screwed into one end of the body and has its land extending through the helix and terminating in abutting engagement with the bottom of a respective recess in the end face of the helix at the other end of the body.

8. A shear force fluid flow device as claimed in claim 7 wherein said landed stud arrangement enables adjustment of the pitch of said helix from a minimum to a maximum.

9. A shear force fluid flow device substantially as described in this specification and with reference to the accompanying drawings.

10. A shear force pump substantially as described in this specification and with reference to the drawings.

11. A shear force turbine substantially as described in the specification.