PUMP OR COMPRESSOR UNIT

Abstract: A contra-rotating pump or compressor unit is made axially compact by moving the fluid along concentric annular flow path portions between which the flow direction is reversed. The unit can comprise concentric contra-rotating sleeves (31, 32, 35) provided with impeller vanes or blades and defining the flow path portions between them, or axially adjacent contra-rotating impeller assemblies each comprising concentric rings with impeller vanes between them. The flow direction reversal can be effected either by fixed housing portions co-operating with the sleeves or rings or by annular walls (34, 62) connecting alternate sleeves (31, 32, 35) or rings.

Description: PUMP OR COMPRESSOR UNIT The invention relates to a pump or compressor unit of the kind having impeller means rotatable about an axis for directing fluid received at a fluid inlet along a fluid flow path to a fluid outlet. Contra-rotating pump or compressor units of this kind, as shown for example in EP 0 217 847 (FD6) and U.S. Patent 2 234 733 to Jendrassik, have contra-rotating impeller blades shaped so as to induce fluid flow in the axial direction. Such units necessarily have substantial axial length. Also known from WO 91/04417 and EP-A-0 348 342 are pump or compressor units of this kind in which concentric rings of the blades or vanes are rotated in opposed directions, the blades or vanes being arranged to move a fluid in a direction generally radially of the axis of rotation. Such pumps or compressor units can provide advantages mechanically but have some disadvantages in respect of pressure generation. The present invention accordingly is concerned with providing a pump or compressor unit free of such disadvantages. The invention accordingly provides a pump or compressor unit of this kind in which the fluid flow path has portions extending axially or approximately axially and of which the directions alternate. The pump or compressor unit of the invention thus provides the advantages of an axial flow type of unit with the compactness in the axial direction of a radial flow unit. The directions of the flow path portions can depart substantially from the axial direction but will at least overlap along the axis to obtain the desired axial compactness. In a preferred construction, the flow path through the impeller means comprises any appropriate number of concentric annular flow path portions, having a generally zig-zag configuration as seen in radial cross-section. The impeller means conveniently comprises first and second co-operating sets of impeller blades or vanes which are preferably contra-rotating, being rotated about the axis in opposite directions in common, or by individually controllable drive means. The unit of the invention can thus have a plurality of concentric radially spaced drum or sleeve-like supports for impeller blades or vanes, the support being rotatably driven in opposed directions, and guide means for re-directing the flowing fluid through 180° or thereabout between the flow path sections. The guide means can be integrated with the supports so as to rotate with the impeller blades or can be stationary, in which event they can be part of the pump housing. Pump or compressor units of the invention can be employed to move liquids so as to have essentially only a pumping action, or a gas, or a mixture of liquid and gas, for example, in oil extraction applications where a multi-phase fluid has to be handled, when compression of the gas or the gaseous component of the mixture necessarily ensues. The drive means for contra-rotating impeller means of the invention can comprise separate electric, hydraulic or pneumatic motors axially spaced with the impeller means between them. Close coupled oil cooled electric motors can be used in a sealed or "canned" unit which is of special interest for installations where leakages to or from the unit can be critical, for example in subsea installations to prevent water ingress, and in topside applications to prevent pumped fluid leakage to the surroundings. A separate high pressure seal chamber can be provided, so that a lower pressure can be maintained in the actual motor chamber. The invention is further described below, by way of example, with reference to the accompanying drawings, in which like parts are indicated by like reference numerals and in which: Figure 1 is a schematic sectional side view of a first pump or compressor unit embodying the invention; Figure 2 is a like view of a second pump or compressor unit embodying the invention; Figure 3 is a like view of a third pump or compressor unit embodying the invention; and Figure 3A is a fragmentary view on a larger scale illustrating a sealing arrangement incorporated in the unit of Figure 3. The pump or compressor unit illustrated in Figure 1 comprises a housing 1 of generally cylindrical shape with a fluid inlet 2 and a fluid outlet 4 in respective opposed end walls 5 and 6. The end walls are annular and extend round respective co-axial drive shafts 10 and 11, aligned on an axis 12. Each shaft is rotatably driven by a respective electric motor (not shown), the drive shafts having opposed rotational directions. At their spaced inner ends, the drive shafts 10 and 11 mount respective rotor walls 14 and 15 at right angles to the axis 12. The fluid inlet 2 is constituted by the housing end wall 5 and by an inwardly tapering frusto-σonical internal wall 7 having a short sleeve 9 which is centred on the axis 12 and which concentrically surrounds a short sleeve 16 projecting outwardly from the rotor wall 14. Sealing means (not shown) operative between the sleeves 9 and 14 seals fluid entering the unit through the fluid inlet 2 from pressurised fluid in a working chamber 20 within the housing 1, outwardly of the sleeve 9. The chamber 20 is sealed also by sealing means operative between a sleeve 17 extending inwardly from the end wall 6 and an outwardly extending sleeve 19 on the rotor wall 15, the sleeves 17 and 19 being centred on the axis 12. The fluid inlet 2 communicates freely with an inlet chamber 21 between the two rotor walls 14,15 by way of apertures in the rotor wall 14 between the drive shaft 10 and the sleeve 16. At its outer edge, the rotor wall 14 supports radially spaced inner and outer concentric sleeves 31 and 32 which are connected together at the inlet end of the unit by an annular wall 34 of semi-circular radial cross-section. The rotor wall 15 carries at its outer end an intermediate sleeve 35 received radially midway between the sleeves 31 and 32. Annular rows of impeller vanes or blades 36 and 37 project towards each other from the outer surface of the sleeve 31 and from the inner surface of the sleeve 32. The blades 36 and 37 are received between and co-operate vanes or blades 40 and 41. The blades 36 and 40 co-operate to move fluid from the chamber 21 axially towards the inlet end of the housing and the blades 37 and 41 move the fluid again axially but in the contrary direction. The pressurised fluid thus enters the working chamber 20 from between the blades 37 and 41 and discharges from the unit through the fluid outlet 4. The unit of Figure 1 thus provides for two axial concentric flow path sections but more such sections can be provided. In the second form of pump or compressor unit according to the invention, shown in Figure 2, the housing 1 has sleeve portions 51 and 52 extending outwardly of the housing around the drive shafts 10 and 11 and annular seal means 54 and 55 between each drive shaft and the associated sleeve portion. At the outer side of the outer impeller sleeve 32, a seal 56 to the inner surface of the side wall of the housing is provided, to separate the housing interior into inlet and outlet chambers 57 and 59. The rotor wall 14 supports the impeller sleeves 31 and 32, not directly, but by means of an annular ring or set of impeller blades 61. The rotor wall 15 mounts the intermediate sleeve 35 again indirectly, by means of an annular end wall 62 and the wall also mounts an annular set of impeller blades 64 arranged to co-operate with the blades 61 to drive fluid entering the housing through the inlet 2 axially in the direction towards the outlet 4. The wall 62 corresponds generally to the annular wall 34, being semi¬ circular in cross-section and functioning to reverse the direction of the fluid flowing between the blades 61 and 64 whilst diverting the flows radially outwardly to between the blades 36 and 40. The unit of Figure 2 thus functions generally similarly to that of Figure 1, but provides for axial pump or compressor action on the incoming fluid in three concentric annular flow passage sections instead of only two. In the pump unit or compressor of the invention shown in Figure 3, the incoming fluid is moved axially in alternating directions along four concentric axial paths, so that the inlet and discharge directions are opposed, and radially spaced, instead of being aligned, or substantially aligned, as in the units of Figures 1 and 2. Moreover, whereas in the units of Figures 1 and 2, the flowing fluid is redirected from one axial flow path section to another by the axial guide means constituted by the annular end walls 34 and 62, which are secured to the blades to move with them, in Figure 3, the guide means are stationary and constituted parts of the housing of the unit. Thus, the housing 1 is again approximately in the shape of an axially short cylindrical drum, and fluid inlet 2 and outlet 4 are both provided in the end wall 5, with the inlet spaced radially inwardly of the outlet. Between the inlet and the outlet, the housing 1 includes an annular wall portion 71 which is approximately semi-circular in radial cross-section. The other end wall 6 is formed with an inner or an outer annular end wall portion 72 and 74 of similar, opposed, shapes, with the wall portion 71 radially midway between them. The contra-rotating impeller means of the unit of Figure 3 comprise innermost axially adjacent annular rows or sets of blades 75 and 76 extending outwardly from the rotor walls 14 and 15 respectively to surrounding rings 77 and 79 , from which extend a second adjacent pair of sets of blades 75a and 76a themselves surrounded by rings 77a and 79a . Third sets of impeller blades 75b , 76b surround the second sets and fourth sets 75c , 76b surround the third . Each impeller assembly, comprising four concentric annular rows or sets of blades , ends at its outer periphery with a respective outer ring 77c , 79c at the inner surface of the side wall of the housing. Each axially adjacent pair of contra-rotating blade sets is arranged to move f luid axially but in directions which alternate from one pair to the radially adjacent pair. Thus the blades 75 and 76 co-operate to urge fluid entering at the inlet 2 in the direction of the arrow. The flow is then turned in the opposite direction by the end wall portion 72 so as to be moved in the contrary axial direction by the radial ly ad j ac ent pair o f b lade s et s 7 5 a , 7 6 b . The pressurised fluid flow is then turned again by the housing wall portion 71 back to its original inlet direction through the next set of blades 75b , 76b and is finally turned once again by the wall portion 74 to be discharged from the housing through the outlet 4 after passage through the fourth and outermost set of blades 75c , 76c . Each of the outer concentric annular fluid flow path sections , containing the axially adjacent contra-rotating sets of blades , has to be sealed against fluid flow radially to the inwardly adjacent fluid flow path section which is at a lower pressure . A suitable sealing arrangement "A" , between the adjacent edges of the third pair of rings 77b, 79b is shown in Figure 3A and comprises interf itting seal elements 80 and 81 extending axially from the adjacent edges of the rings , the sealing elements being provided with interfitting configurations , here in the form of a triangular section ridge and groove . The rings must be sealed also to the housing wall portions and similar or other suitable seals are provided at appropriate positions in all the illustrated pump units of the invention. In this connection, reference may be made to the sealing arrangements described in WO 91/04417 and illustrated in Figures la and lb of that document which is incorporated herein by reference. The three pump units embodying the invention illustrated and described above can be modified in various ways within the scope of the invention. For example, the flow paths between the inlets 2 and outlets 4 can be of decreasing cross-section in the flow direction, where the fluid is substantially compressed during its passage through the unit. The fluid inlets and outlets can be differently located in the housing walls, for example, and the flow direction can be radially inwards instead of outwards. Thus, the inlet 2 of the unit of Figure 3 can be radially outwardly of the outlet 4 instead of as shown. The invention can thus be embodied in a variety of ways other than as specifically described.

Claims: CLAIMS 1. A pump or compressor unit comprising a housing (1) having a fluid inlet (2) and a fluid outlet (4), and impeller means (36,37,40,41;36.37,40,41,62,64;75-75c,76-76c) in the housing mounted for rotation about an axis (12) , rotation of the impeller means moving fluid from the inlet to the outlet along a fluid flow path having portions which overlap in the direction of the axis. 2. A unit as claimed in claim 1 wherein the flow path portions have alternating directions with at least a major component parallel to the axis. 3. A unit as claimed in claim 1 or 2 wherein each flow path portion comprises an annular portion of uniform of uniform cross-section. 4. A unit as claimed in claim 1, 2 or 3 wherein the impeller means comprises impeller means (36,37,40,41;36,37,40,41,62,64;75-75c,76-76c) carried by at least three radially spaced sleeves (31,32,35;79-79b) each sleeve being concentric with the axis, and guide means (34;34,62;71,72,74) for guiding fluid flowing between two radially adjacent sleeves to flow between one of the two radially adjacent sleeve and another, or the other, of the sleeves. 5. A unit as claimed in claim 4 wherein the guide means (34;34,62) connect alternate sleeves at one end thereof. 6. A unit as claimed in claim 4 wherein the guide means (71,72,74) is constituted by part or parts of the housing (1). 7. A unit as claimed in 5 or 6 wherein each sleeve carries impeller vanes which are received between and co¬ operate with impeller vanes carried by an adjacent sleeve, or by adjacent sleeves. 8. A unit as claimed in claim 4, 5, 6 or 7 wherein alternate ones of the sleeves are connected together to form two impeller assemblies rotatably driven in opposite directions. 9. A unit as claimed in claim 4, 5 or 6 wherein the impeller means comprise impeller vanes carried by at least three further radially spaced sleeves each axially aligned with a respective one of the first-mentioned radially spaced sleeves. 10. A unit as claimed in claim 9 wherein the first and second mentioned radially spaced sleeves constitute separate impeller assemblies which are rotatably driven in opposed directions. 11. A unit as claimed in 8 or 10 wherein each impeller assembly is mounted on a respective one of axially aligned drive shafts (10,11) extending from drive means into the housing. 12. A unit as claimed in any one of claims 4-11 wherein seals (54,55 between the housing and each drive shaft and a seal (56) between the housing and the outermost sleeve divide the housing interior into an inlet chamber (57) and an outlet chamber (59) . 13. A unit as claimed in any one of claims 1-11 wherein the inlet (2) and the outlet (4) are adjacent in a side wall of the housing, the flow path having an even number of portions. 14. A unit as claimed in any preceding claim wherein the flow path decreases in cross-section from the inlet to the outlet.

Inventors: MOHN FRANK, MOHN, FRANK
Applicants: FRAMO DEV LTD, FRAMO DEVELOPMENTS (UK) LIMITED
Application year: 1992
Main classification: F04D3
IPC codes: F04D3, F04D5, F04D19