GB2260368A

GB2260368A - Pump having flow control jet nozzle.

Info

Publication number: GB2260368A
Application number: GB9220992A
Authority: GB
Inventors: Mark John Robbie
Original assignee: Dowty Defence and Air Systems Ltd
Current assignee: Dowty Defence and Air Systems Ltd
Priority date: 1991-10-10
Filing date: 1992-10-06
Publication date: 1993-04-14
Also published as: WO1993007390A1; GB9121559D0; GB9220992D0

Abstract

A regenerative pump comprises a housing (1) with a fluid inlet (19) and a fluid outlet, an impeller (12) having a plurality of vanes (13) spaced angularly around the axis of rotation of the impeller (12) and accommodated within a flow channel (4) extending between the inlet and outlet, an annular core (14) located in the flow channel (4) around the vanes (13) and in the plane of rotation of the impeller (12) so that the vanes serve to induce fluid flow around the core (14), and flow control means (21) comprising a nozzle (23) which is connectible to a fluid supply and opens into the flow channel (4) adjacent to the inlet (19) so as to produce a jet of fluid to selectively oppose or disturb the flow of fluid from the inlet (19) and thereby reduce the fluid pressure generated in the pump. The nozzle (23) is located on the opposite side of the impeller from the inlet (19). The supply of fluid to the nozzle (23) and/or the orientation of the nozzle (23) may be varied.

Description

PUMPS Technical Field This invention relates to regenerative pumps.

Regenerative pumps comprise a housing with a fluid inlet and a fluid outlet, and an impeller rotatably mounted within the housing and having a plurality of vanes spaced angularly around the axis of rotation of the impeller and accommodated within a flow channel within the housing extending between the inlet and outlet, the vanes serving to induce a spiral or helical flow of fluid along the length of the flow channel as the impeller is rotated. The spiral flow is induced by the centrifugal and frictional effects of the vanes on the fluid and causes the fluid to be re-circulated repeatedly across a plurality of the vanes between the inlet and outlet, thereby progressively increasing the fluid pressure.

In a known type of regenerative pump, an annular core is provided in the flow channel and the fluid flows in said spiral path about the core. The vanes project from the impeller into the flow channel and either terminate just short of a fixed core or are connected to the core so that the core rotates with the rotor. The vanes may have an aerofoil cross-section to enhance the fluid flow effects, and means may be provided to assist the initial spiral flow of fluid at the inlet. An example of such a regenerative pump is shown in British Patent No. 2068461.

Regenerative pumps are mechanically simple and reliable and are capable of operating at high speed and have low specific weight. Regenerative pumps are also capable of generating high pressures, the pressure generally being proportional to the square of the impeller speed.

However, in some applications, for example, as engine driven fuel pumps for aviation gas turbine engines, this pressure/speed characteristic can be a problem. Thus a regenerative fuel pump may be designed to produce a desired fuel pressure at low speed, engine light-up conditions, but the fuel pressure at maximum engine speed may then be excessive, resulting in fuel heating because of the high energy input of the pump.

Disclosure of the Invention An object of the present invention is to provide a regenerative pump in which the aforesaid problem of excess pressure at high speed can be avoided.

According to the present invention, a regenerative pump comprises a housing with a fluid inlet and a fluid outlet, an impeller rotatably mounted within the housing and having a plurality of vanes spaced angularly around the axis of rotation of the impeller and accommodated within a flow channel within the housing extending between the inlet and outlet, an annular core located in the flow channel around the vanes and in the plane of rotation of the impeller so that the vanes serve to induce fluid flow around the core, and flow control means which is selectively operable to vary the flow of fluid around the core and which comprises a nozzle which is connectible to a fluid supply and opens into the flow channel adjacent to the inlet so as to produce a jet of fluid to oppose or disturb the flow of fluid from the inlet and thereby reduce the fluid pressure generated in the pump.

Preferably, the nozzle is located on the opposite side of the impeller from the inlet and directs the jet towards the inlet to oppose or disturb the flow of fluid from the inlet.

Selective operation of the flow control means may involve variation of the supply of fluid to the nozzle and/or adjustment of the nozzle to vary the direction of the jet relative to the inlet. For example, a jet pipe may be rotatably supported in the housing and have a nozzle offset from the axis of rotation of the pipe.

Description of the Drawings The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is an axial section through a regenerative pump according to the invention, Figure 2 is an axial view of the inner face of the left hand section of the pump housing in Figure 1, Figure 3 is an axial section through the stripper means of the pump in Figure 1 passing through the line 3-3 in Figure 2, Figure 4 is a section through some of the vanes of the impeller along the line 4-4 of that part of the impeller shown in Figure 2, and Figure 5 is a graph showing the performance of the pump of Figures 1 to 4 with different angular settings of the flow control means.

Mode of Carrying Out the Invention The regenerative pump illustrated in Figures 1 to 4 comprises a housing 1 formed in the two sections 2, 3 which are connected face-to-face and define an internal cavity 4 therebetween to receive an impeller 5 which is mounted on a drive shaft 6 supported in the housing by combined journal and thrust bearings 7. One end of the shaft 6 is received in a blind bore 8 in an end plate 9, and the other end of the shaft 6 is sealed in the housing by a mechanical shaft seal 10 and is formed with internal splines 11 for driving connection to a power source.

The impeller 5 comprises an annular body 12 which carries a plurality of radially projecting vanes 13 around its outer periphery that are V-shaped in cross-section, as shown in Figure 4. A hollow toroidal ring 14 is connected to the outer edges of these vanes 13. The body 12 of the impeller is a close fit with the inner walls 15 of the cavity 4 in the housing 1, but the vanes 13 and toroidal ring 14 project radially into an enlarged peripheral portion of the cavity 4 in the form of a toroidal chamber 16 concentric with the shaft 6 and symmetrical with the impeller 15 about the radially extending dividing plane along which the housing sections 2, 3 meet.

Two stripper means 17 are provided within the toroidal chamber 16 at diametrically opposite locations, as shown in Figure 2, so as to divide it into two similar fluid flow channels 16', 16".

Each stripper means 17 comprises a pair of stripper blocks 18 which are secured in opposed recesses in the housing sections 2, 3 and have inner faces which cooperate to closely surround the vanes 13 and the toroidal ring 14, as shown in Figure 3. Each flow channel 16', 16" is provided with an inlet port 19 at one end thereof upstream of the direction of rotation R of the impeller as shown in Figure 2, and an outlet port 20 is provided at the other end of each flow channel.

These inlet and outlets ports 19, 20 are formed in the one housing section 2. Both the inlet ports 19 and the outlet ports 20 in each flow channel 16', 16" are formed diametrically opposite one another, as shown in Figure 2. The two flow channels 16', 16" can either be connected in series or in parallel by suitable interconnection of the inlet and outlet ports 19, 20.

In operation, the impeller 5 is rotated in the direction R and induces a flow of fluid in each flow channel 16', 16" between the inlet ports 19 and outlet ports 20 with a progressively increasing pressure, the vanes 13 being arranged so that the two portions of the V-section extend outwards and downstream in the direction R, as shown in Figure 4. The nature of the flow in each flow channel 16', 16", and the way in which it is influenced by flow control means 21 in each channel, will now be described.

The flow control means 21 comprises a jet pipe having a straight tubular body portion 22 which is rotatably mounted in the housing section 3 with its axis parallel to the axis of the shaft 6 and in alignment with the central region of the inlet port 19 in the housing section 2 on the opposite side of the impeller 12. The body portion 22 terminates in a nozzle portion 23 within the channel 16" which is set at an angle of 45 degrees to the axis of the body portion 22 and terminates in a restricted nozzle opening 24. A supply of fluid pressure is connected to the body portion 22 so as to produce a jet of fluid from the nozzle opening. The fluid pressure is supplied from the outlet port 20 via a pipe connection (not shown) to a drilling 25 through housing 3 and a gallery 26 concentric with the body portion 22.Radial drillings 27 in the body portion 22 connect the fluid pressure to the hollow interior of the body portion 22 and hence to the nozzle portion 23.

Toroidal sealing rings 28 are provided between the body portion 22 and the housing 3 to prevent leakage of the high pressure fluid.

An actuator 29 is provided to control the angular setting of the jet pipe 21 and comprises a rotary electric motor mount on the housing 3, with an output shaft 30 connected via a dog coupiing 31 to the body portion 22 of the jet pipe.

The actuator serves to set the jet pipe 21 in one or the other of two angular settings S, T, as shown in Figure 2, corresponding respectively to settings for maximum pump pressure and reduced pump pressure. The performance of the pump at these two settings S, T is demonstrated in Figure 5 in which the setting is measured in terms of the angle 0 between the direction of the nozzle portion 23 and the radius XX through the axis of the shaft 6 and the axis of the body portion 22.

Pump performance is measured in terms of the pressure differential P between the pump inlet and outlet. The parameter P is measured at 5 degree spaced settings of between 0 and 90 degrees.

Figure 5 clearly shows that there is a drop in pressure P at settings between 5 and 25 degrees.

Scttirg S is selected for minimum head pressure rise, typically within a range of 10 to 20 degrees, for example, at a setting of e = 15 degrees. Setting T is selected outside this range, for maximum head pressure rise, typically at a setting between 45 and 90 degrees, for example, at a setting of 2f= 45 degrees.

It will be appreciated that at the setting S with 0 = 15 degrees, the jet pipe 21 is directing a jet of fluid between the blades 13 of the impeller towards the inlet port 19, but that as angle 8- is increased, the jet is progressively directed tangentially of the blades 13 in their direction of rotation R away from the inlet port 19 consequently having less effect on the flow of fluid from the inlet port 19 and its flow around the ring 14.

Claims

1. A regenerative pump comprising a housing with a fluid inlet and a fluid outlet, an impeller rotatably mounted within the housing and having a plurality of vanes spaced angularly around the axis of rotation of the impeller and accommodated within a flow channel within the housing extending between the inlet and outlet, and an annular core located in the flow channel around the vanes and in the plane of rotation of the impeller so that the vanes serve to induce fluid flow around the core, characterised in that flow control means is provided which is selectively operable to vary the flow of fluid around the core and which comprises a nozzle which is connectible to a fluid supply and opens into the flow channel adjacent to the inlet so as to produce a jet of fluid to oppose or disturb the flow of fluid from the inlet and thereby reduce the fluid pressure generated in the pump.

2. A pump as claimed in claim 1 in which the nozzle is located on the opposite side of the impeller from the inlet and directs the jet towards the inlet to oppose or disturb the flow of fluid from the inlet.

3. A pump as claimed in claim 2 in which the nozzle is adjustable in position to vary the direction of the jet of fluid relative to the inlet.

4. A pump as claimed in claim 3 in which the flow control means comprises a jet pipe having a tubular body portion mounted in the housing to be rotatable about a longitudinal axis and a nozzle portion extending from one end of the body portion at an angle to the longitudinal axis of the body portion.

5. A pump as claimed in claim 4 in which the flow control means includes an actuator operable to adjust the position of the nozzle so as to turn the direction of the jet of fluid more or less in the direction of rotation of the impeller.

6. A pump as claimed in any one of the preceding claims in which fluid from the outlet of the pump housing is supplied to the nozzle to produce the jet of fluid.

7. A pump as claimed in any one of claims 3 to 6 in which the jet of fluid is turned through an angle as projected on the plane of rotation of the impeller between high and low pump fluid pressure positions.

8. A pump as claimed in any one of the preceding claims in which the supply of fluid to the nozzle that produces the jet of fluid is varied to vary the jet flow and thereby vary the flow of fluid from the inlet.

9. A pump as claimed in any one of the preceding claims in which the vanes are shaped so that they are symmetrical about the central plane of rotation of the impeller and are inclined in the direction of rotation of the impeller from said central plane of rotation towards their outer edges.

10. A pump as claimed in any one of the preceding claims in which two flow channels are formed in the housing each with a fluid inlet and fluid outlet and each with individual flow control means.

11. A regenerative pump substantially as herein described with reference to the accompanying drawings.