GB1572167A

GB1572167A - Centrifugal pumps

Info

Publication number: GB1572167A
Application number: GB1337476A
Authority: GB
Original assignee: Lucas Industries Ltd
Current assignee: ZF International UK Ltd
Priority date: 1976-04-02
Filing date: 1976-04-02
Publication date: 1980-07-23
Also published as: IT1084838B; DE2714822A1; JPS52121801A; FR2346577A1

Description

(54) CENTRIFUGAL PUMPS (71) We, LUCAS INDUSTRIES LIMITED, a British Company of Great King Street, Birmingham, B19 2XF, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to centrifugal pumps, and in particular to centrifugal pumps for liquid fuels.

It is known, for example from British Patent No. 1,357,726, to provide a centrifugal fuel pump of the type which acts as a vapour separator, the denser liquid fuel being urged to a radially outer part of a pumping chamber and thence to an outlet which delivers this liquid to a fuel control system. An inner core of air and fuel vapour, together with a portion of the liquid fuel is returned to a tank.

It has been found to be a disadvantage of these pumps that the proportion of liquid fuel being returned to the tank may be sufficiently high as to reduce the efficiency of the pump below an acceptable level. It is accordingly an object of the invention to provide a centrifugal pump of the foregoing type, in which liquid and vaporous fuel which are present in a radially inner portion of the pumping chamber are urged to recombine, and the recombined fluid is then directed to join the liquid fuel already present in the radially outer portion of the pumping chamber.

According to the invention a centrifugal pump comprises a body having an inlet, a first outlet aligned with said inlet, and a second outlet, a rotor mounted in said body, said rotor including a central diffuser and a shroud surrounding a said diffuser to define, in conjunction therewith, a pumping chamber of annular section having an inlet opening communicating with said body inlet, a wall member extending axially of said pumping chamber to divide the latter into radially inner and outer portions, said inner and outer portions communicating respectively with said first and second outlets, a plurality of means located in said inner portion for acting on liquid and gas which are, in use, present in said inner portion, to cause said gas to recombine with the liquid, and said wall member including a plurality of perforations through which fluid may pass between said inner and outer portions.

An example of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal section through a centrifugal pump, and Figure 2 is a section, to an enlarged scale, on line 2-2 in Fignre 1.

The pump has a body 10 formed in two parts 11, 12. The part 11 has an opening which forms an inlet 13 for the pump, and the part 12 has an opening, aligned with the inlet 13, providing a first outlet 14 for the pump. The body part 12 includes a volute chamber 15 which communicates with a second outlet 16 of the pump. Mounted on the body 10 adjacent the inlet 13 are a plurality of guide vanes 17 past which fuel can flow to the inlet 13. The body 10 includes windings 18 and provides the stator of an electric induction motor.

Mounted within the body 10 by means of bearings 19, 20 is a rotor which has an outer, generally frusto-conical shroud 21.

Mounted on the shroud 21 are windings 22, whereby the rotor forms the moving part of the aforesaid electric induction motor.

Mounted within the shroud, for rotation therewith, is a hollow, generally conical diffuser 23 whose larger diameter lies adjacent the outlet 14 and whose apex is adjacent the inlet 13. The shroud 21 and diffuser 23 define between them an annular pumping-chamber 24 which communicates with the inlet 13 and whose internal and external diameters increase in a direction away from the inlet 13.

A generally frusto-conical wall member 25 is formed integrally with the shroud 21 and lies within the pumping chamber 24 to divide the latter into a radially inner portion 26 and a radially outer portion 27. Between the shroud 21 and the wall member 25 is a plurality of vanes 28 which define outlets for the portion 27, through which outlets fluid can pass to the volute chamber 15.

The diffuser 23 is supported on the wall member 25 by a plurality of vanes 29, and by a plurality of equi-angularlv spaced radial pins 30. The vanes 29 define a plurality of passages through which fluid can flow from the chamber portion 26 to the outlet 14.

As shown in Figure 2 each pin 30 has a longitudinally extending slot 31, each slot having its general plane inclined to the axis of the pump rotor and having a convergent cross-sectional shape so that fluid passing through the slot 31 is accelerated. Between the vanes 29 the wall member 25 is provided with perforations 32 by means of which fluid can pass between the inner and outer chamber portions 26, 27.

In use, rotation of the pump rotor causes fuel to be urged by centrifugal action along the inside of the wall of the shroud 21 and to be ejected between the vanes 28 into the volute chamber 15, and thence to the outlet 16. Centrifugal action causes the fuel within inlet - 13 to separate into an outer liquid zone adjacent the shroud 21, an inner zone of air and fuel vapour adjacent the wall of the diffuser 23, and an intermediate zone, adjacent both sides of the wall member 25, in which intermediate zone both liquid and gas are present. Centrifugal action on the contents of this intermediate zone causes a further separating action in which liquid tends to pass outwardly through the aperapertures 32 and gas to pass inwardly through these apertures.

Moreover, a relatively higher pressure, due to centrifugal action, exists on the leading side of vanes 29, in the direction of rotation thereof, than on the trailing side.

The bottom portions of the vanes 28, as seen in Figure 1, are further from the inlet 13 than the bottom portions of the vanes 29. The pressure at the leading edges of the vanes 29 is thus higher than that within the adjacent chamber portion 27. Thus liquid tends to be discharged outwardly through the apertures 32 adjacent the leading sides of vanes 29, and gas to pass inwardly through the apertures 32 adjacent the trailing sides of vanes 29.

As fluid passes through the pump it experiences, due to centrifugal action, an increase of pressure over that at the inlet 13.

Pins 30 impart a turbulence to a liquid/gas within the chamber portion 26, and this turbulence combines with the aforesaid pressure increase to cause fuel vapour to re-liquefy and a quantity of the free air to be re-dissolved in the liquid fuel. This action ensures that liquid fuel passing out ward'ly through the apertures 32 contains a substantial amount of dissolved air, and that a minimum amount of fuel vapour passes to the outlet 14.

It is generally advantageous, when hydrocarbon fuels are being pumped to fuel control systems, to maximise the amount of air in solution, while removing free air and vapour. As indicated above, the pump of the present invention tends to provide these desired effects.

Pumping action sets up a fluid vortex whose apex lies in the vicinity of the inlet 13.

To ensure that the apex of the vortex remains centrally within the pump, the diffuser 23 may have an elongated portion 33 which extends from the diffuser apex beyond the inlet 13.

WHAT WE CLAIM IS: 1. A centrifugal pump comprising a body having an inlet, a first outlet aligned with said inlet, and a second outlet, a rotor mounted in said body, said rotor including a central diffuser and a shroud surrounding said diffuser to define, in conjunction therewith, a pumping chamber of annular section having an inlet opening communicating with said body inlet, a wall member extending axially of said pumping chamber to divide the latter into radially inner and outer portions, said inner and outer portions communicating respectively with said first and second outlets, a plurality of means located in said inner portion for acting on liquid and gas which are, in use, present in said inner portion, to cause said gas to recombine with the liquid, and said wall member including a plurality of perforations through which fluid may pass between said inner and outer portions.

2. A pump as claimed in Claim I in which said means for acting on the liquid and gas comprises a plurality of members extending transversely of the direction of fluid flow through said inner portion, said members having through passages which are convergent in the direction of said fluid flow.

3. A pump as claimed in Claim 2 in which said members comprise pins extending radially of the axis of rotation of said rotor.

4. A pump as claimed in Claim 4 in which said pins are substantially equiangularly spaced.

5. A pump as claimed in Claim 3 or Claim 4 in which said through passages comprise longitudinal slots in said pins.

6. A pump as claimed in Claim 5 in which the general planes of said slots are inclined to the axis of said rotor.

7. A pumn as claimed in any preceding claim in which the internal and external diameters of said pumDing chamber increase in a direction away from said inlet.

8. A pump as claimed in any preceding

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. plurality of vanes 28 which define outlets for the portion 27, through which outlets fluid can pass to the volute chamber 15. The diffuser 23 is supported on the wall member 25 by a plurality of vanes 29, and by a plurality of equi-angularlv spaced radial pins 30. The vanes 29 define a plurality of passages through which fluid can flow from the chamber portion 26 to the outlet 14. As shown in Figure 2 each pin 30 has a longitudinally extending slot 31, each slot having its general plane inclined to the axis of the pump rotor and having a convergent cross-sectional shape so that fluid passing through the slot 31 is accelerated. Between the vanes 29 the wall member 25 is provided with perforations 32 by means of which fluid can pass between the inner and outer chamber portions 26, 27. In use, rotation of the pump rotor causes fuel to be urged by centrifugal action along the inside of the wall of the shroud 21 and to be ejected between the vanes 28 into the volute chamber 15, and thence to the outlet 16. Centrifugal action causes the fuel within inlet - 13 to separate into an outer liquid zone adjacent the shroud 21, an inner zone of air and fuel vapour adjacent the wall of the diffuser 23, and an intermediate zone, adjacent both sides of the wall member 25, in which intermediate zone both liquid and gas are present. Centrifugal action on the contents of this intermediate zone causes a further separating action in which liquid tends to pass outwardly through the aperapertures 32 and gas to pass inwardly through these apertures. Moreover, a relatively higher pressure, due to centrifugal action, exists on the leading side of vanes 29, in the direction of rotation thereof, than on the trailing side. The bottom portions of the vanes 28, as seen in Figure 1, are further from the inlet 13 than the bottom portions of the vanes 29. The pressure at the leading edges of the vanes 29 is thus higher than that within the adjacent chamber portion 27. Thus liquid tends to be discharged outwardly through the apertures 32 adjacent the leading sides of vanes 29, and gas to pass inwardly through the apertures 32 adjacent the trailing sides of vanes 29. As fluid passes through the pump it experiences, due to centrifugal action, an increase of pressure over that at the inlet 13. Pins 30 impart a turbulence to a liquid/gas within the chamber portion 26, and this turbulence combines with the aforesaid pressure increase to cause fuel vapour to re-liquefy and a quantity of the free air to be re-dissolved in the liquid fuel. This action ensures that liquid fuel passing out ward'ly through the apertures 32 contains a substantial amount of dissolved air, and that a minimum amount of fuel vapour passes to the outlet 14. It is generally advantageous, when hydrocarbon fuels are being pumped to fuel control systems, to maximise the amount of air in solution, while removing free air and vapour. As indicated above, the pump of the present invention tends to provide these desired effects. Pumping action sets up a fluid vortex whose apex lies in the vicinity of the inlet 13. To ensure that the apex of the vortex remains centrally within the pump, the diffuser 23 may have an elongated portion 33 which extends from the diffuser apex beyond the inlet 13. WHAT WE CLAIM IS:

1. A centrifugal pump comprising a body having an inlet, a first outlet aligned with said inlet, and a second outlet, a rotor mounted in said body, said rotor including a central diffuser and a shroud surrounding said diffuser to define, in conjunction therewith, a pumping chamber of annular section having an inlet opening communicating with said body inlet, a wall member extending axially of said pumping chamber to divide the latter into radially inner and outer portions, said inner and outer portions communicating respectively with said first and second outlets, a plurality of means located in said inner portion for acting on liquid and gas which are, in use, present in said inner portion, to cause said gas to recombine with the liquid, and said wall member including a plurality of perforations through which fluid may pass between said inner and outer portions.

8. A pump as claimed in any preceding

claim which includes a plurality of first vanes within said outer portion, said first vanes defining a plurality of passages through which fluid can flow from said outer portion to said second outlet.

9. A pump as claimed in Claim 8 which includes a plurality of second vanes within said inner portion, said second vanes defining a plurality of passages through which fluid can flow to said first outlet.

10. A pump as claimed in Claim 9 n which the portions of said second vanes nearest said inlet are spaced therefrom by a less distance than the corresponding portions of said first vanes.

11. A centrifugal pump substantially as hereinbefore described with reference to and as shown in the accompanying drawings.