GB2310005A - Apparatus for energy transfer - Google Patents

Abstract

A pump has a bore (12) for the passage of a high energy pumping fluid (14), a passage for low energy fluid (15) to be pumped, and an annular duct (4) for the passage of a combined pumped stream of the high and low energy fluids (14,15), spiral passages (13) to provide a swirling motion to the high energy fluid stream (14) relative to the low energy fluid stream (15). A rotor (5) is provided for interacting the low energy and high energy fluid streams (14,15) in rotation to form a combined yet unmixed flow with substantially non-dissipative transfer of energy from the high energy fluid (14) to the low energy fluid (15) thereby causing the pumping of said low energy fluid (15) through the annular duct (4).

Description

APPARATUS FOR ENERGY TRANSFER FIELD OF THE INVENTION This invention relates to apparatus for effecting energy exchange between a high energy stream of fluid and a low energy stream of fluid. Here the term fluid refers to either gas or liquid or both, and energy refers to enthalpy plus kinetic energy, gravity effects being insignificant in this case.

BACKGROUND OF THE INVENTION There are a number of known devices for transferring energy from a high energy driving fluid to a low energy driven fluid. One example is the jet pump or ejector in which the high energy fluid is injected at high velocity along the centre of a mixing tube causing the driven fluid to be entrained between the high velocity jet and the walls of the tube. Energy is transferred between the two streams as they progress along the mixing tube, the exchange being effected due to the action of shear forces at the jet/entrained fluid interface.

This process is highly dissipative and consequently the efficiency of the jet pump is low.

There are a variety of other mechanisms where energy is transferred indirectly.

Typically energy is extracted from one flow through a turbine which drives a compressor and this in turn imparts energy to a second flow. Such turbine/compressor or engine/pump combinations are much more efficient than the jet pump. They are, however, much more expensive to construct and maintain and are usually bulky which is a disadvantage in some situations.

Foa (UK Patent 860,073; US Patents 3,046,732, 3,216,649 and 4,239,155) has proposed a variety of means to effect high efficiency energy transfer directly between a driving fluid and a driven fluid. In particular, a stream of driving fluid is typically injected into a space occupied by the driven fluid and is desired to be translated in another direction causing energy to be mechanically transferred from the driving fluid to the driven fluid.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pumping method and apparatus which combines efficient and substantially non-dissipative energy transfer between the pumping and pumped streams whilst being of relatively simple construction.

According to the invention there is provided a pump comprising first ducting means for passage of high energy pumping fluid, second ducting means for passage of low energy fluid to be pumped, third ducting means for passage of a combined pumped stream of said high and low energy fluid, means to provide a swirling motion to the high energy fluid stream relative to the low energy fluid stream, and rotor means for interacting the low energy and high energy fluid streams in rotation to form a combined yet unmixed flow with substantially non-dissipative transfer of energy from the high energy fluid to the low energy fluid thereby causing the pumping of said low energy fluid through said third ducting means.

Preferably the rotor means is provided with separate passageways for the high and low energy fluid. The passageways lead to the third ducting means for the combined yet unmixed flow formed on mutual deflection of the high and low energy fluid streams at the passageway exits during rotation of the rotor means.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the present invention will now become apparent from the following description of preferred embodiments thereof taken with reference to the accompanying drawings in which: Fig 1 is a side view in perspective of a device according to one embodiment of the invention, partially in section and broken away for convenience; Fig 2 is a cross sectional view along the line X-X of Fig 1; Fig 3 is a cross sectional view along the line Y-Y of Fig 1; Fig 4 is a side view in perspective of a device according to a further embodiment of the invention shown partially in section and broken away for convenience; Fig 5 is a cross sectional view along the line X-X of Fig 4; and Fig 6 is a cross sectional view along the line Y-Y of Fig 4.

PREFERRED EMBODIMENTS OF THE INVENTION Before the device according to the invention is described, it will be instructive to review the behaviour of two fluid streams A and B interacting and mutually deflecting to form a third combined yet unmixed stream C.

Ignoring gravitational forces, the energy per unit mass, e, is defined e = h + 1/2(u +v2 +w2) (1) where h is the enthalpy per unit mass and u, v and w are velocity components in a cylindrical polar coordinate system (r, 8,z) fixed in space with respect to the device.

The mass flow rates of streams A, B and C aremA ,mB and mc respectively such that by continuity of mass C mc = mA + ms (2) The power available in the uniform input stream A is PA= mA eA (3) where eA is the energy unit mass of the stream A.

Similarly for stream B PB = MB eB (4) Considering stream C Pc =mc ec = mA ec + mB ec by(2) (5) Consequently the power given up by the power fluid stream A is PA - Pc(A)A (eA ec) (6) and that gained by the pumped stream B is Pc(B) = MB (eC-eB ) (7) where Pc(A)andPc(B) represents the fractions of the power in stream C due to the component streams A and B.

Now a second orthogonal coordinate system (rm, #m, zm) may be considered which is fixed with respect to the aforementioned rotor and which rotates with angular velocity co in the #m direction relative to the fixed coordinate system (r, O,z) such that U.. =U,V =v-#r and wm = w, (8) The fluid flow is assumed to be steady in this coordinate system so that by Bernoulli's equation (which must include the potential of the centrifugal force) h + (u + v + wm) - # r = constant (9) In terms of the fixed coordinates this becomes h+12(u2+(v-arY+w2)-Ia)2r2 = constant (10) Consequently, equation (1) simplifies to e = arv+ constant (11) From (6) and (7) above the new expressions for the power lost by fluid stream A and the power gained by fluid stream B become PA Pc(A)=mA #(rAvA-rcvc) (12) and pC(B)-P9 = mB #(rc#c - rB#B) (13) where VA xVa, VC are the components of velocity in the e direction of the undisturbed streams A, B, C respectively, at radial distances rA ,rB,rC from the axis of rotation respectively.

In the ideal case, the power lost by fluid A is equal to that gained by fluid B so that the above equations combine to give mArA#d + mBrB#B= mCrC#C (14) which is the equation for conservation of angular momentum.

From equations (12), (13) and (14) it is clear that either VA or VB (and hence vc) must be non zero if there is to be any transfer of power from stream A to stream B (at least by non-dissipative means). This is also intuitively clear as work will only be done when there is both a mutual deflection of the streams A and B and a movement through a distance of the forces effecting the deflection.

A device according to the invention making use of the above theory is depicted in the drawings. The device as will be more fully described below, incorporates a spinning rotor to effect interaction between the driving and driven fluid streams A and B to achieve the desired result in combined stream C.

The theory of itself makes no reference to rotor design. The theory, however, assumes that the entire flow is irrotational and the rotor may be appropriately designed for this to be so. In particular, the rotor may be configured such that the fluid streams A, B and C are confined to separate ducts, communication taking place by means of connecting passages in the rotor. Thereby it is possible substantially to achieve both irrotational flow with streams A, B and C having different angular components of velocity. In general it will be desirable to have the high energy fluid stream A swirling faster than the rotor and consequently the orientation of the entrance to the passages conducting the high energy fluid is an important factor.

Referring to the drawings, a device according to a first embodiment of the invention is shown in Figs 1, 2 and 3, and comprises a stationary cylindrical inner housing 1 mounted coaxially with an exterior cylindrical casing 2 (mountings not shown) so as to form an annular duct 3, 4 between the outer surface of the housing 1 and the inner surface of the casing 2.

The inner housing 1 carries a free spinning rotor 5 (bearings not shown) in which are provided a number of openings 6 equally spaced around the periphery of the rotor 5. The outer surface of the rotor 5 is flush with the surface of the cylindrical housing 1 and the axis of rotation of the rotor 5 is coincident with the axes of the housing 1 and casing 2.

The inner surface of the rotor 5 faces an annular groove 7 formed in the outer surface of the housing 1 to define an internal annular chamber 8 in communication with the annular space 4 through the openings 6.

The openings 6 in the rotor 5 are partially surrounded by shrouds or vanes 9 extending outwardly between the annular spaces 3, 4 to meet, except for a small clearance, the inner surface of the casing 2. The spaces between and exterior to the shrouds 9 thus form moving passages 10 which connect annular duct 3 with annular duct 4.

The inner surface of the shrouds or vanes 9 and the interior surface of the casing 2 form passages 11 leading from the openings 6 which move with the rotor 5.

The inner housing 1 is provided with a centrally located blind bore 12. Spiral passageways 13 are formed in the housing 1 at the end of the bore 12 to communicate the bore 12 with the chamber 8.

In operation high energy fluid 14 is delivered to the bore 12 from whence it enters the spiral passages 13 which are so shaped as to direct the high energy fluid 14 tangentially into the chamber 8 thereby imparting to it a desired angular velocity with respect to the zero angular velocity of the low energy fluid 15 carried by the annular duct 3.

The high energy stream 14 then traverses the rotor openings 6 and shroud passages 11 into the annular space 4. The reaction of the fluid 14 entering the passages 11 causes the rotor 5 to rotate in the same direction as the circulation of driving fluid 14 in the chamber 8. The entrances to these passages 11 from the chamber 8 are shaped so that the rotor velocity at those entrances is less than the angular component of velocity of the high energy fluid 14 at the point of entry to passages 11.

Upon exit from passages 11, the high energy fluid 14 meets the low energy fluid 15 emerging from passages 10. At this point the flows deflect each other and flow thereafter as a combined, but unmixed, stream 16 through the annular duct 4 exiting into a diffuser (not shown) where a small rise in energy will occur as the velocity of the stream 16 is reduced. Alternatively, the stream 16 may exit into another stage of the device.

A further embodiment of the invention is shown in Figs 4, 5 and 6 The devices shown in these figures comprise an outer cylindrical casing 17 and an inner cylindrical block 18.

The inner cylindrical block 18 has an up-stream portion 19 of smaller diameter than a down-stream portion 20 thereof.

The transitional surface 21 of the inner block 18 between the portions of smaller and larger diameter 19, 20 is smoothly concaved as shown.

An annular chamber 22 for high energy fluid 14 is formed in the outer casing 17 at the up-stream end of the device between the wall of the outer casing 17 and a parallel annular inner wall portion 23 joined thereto by a vertical annular wall 24.

Tangentially directed passageways 25 for high energy fluid 14 are formed through the wall of the outer casing 17 leading to the chamber 22 as shown.

The annular surface 26 of the inner wall portion 23 is spaced from the annular surface 27 of the smaller diameter portion 19 of the inner block 18 to form an annular duct 28 for low energy energy fluid 15 extending to the extremity of the inner wall portion 23.

The annular space between the larger diameter portion 20 of the inner block 18 and the inner wall of the outer casing 17 down-stream of the annular duct 28 forms a further annular duct 29 for a combined stream 16 of high and low energy fluid 14, 15.

A rotor 30 is mounted for rotation around the inner block 18 over the transition between the smaller and larger diameter portions 19, 20.

The rotor 30 is provided with peripheral vane formations 31 which provide intercommunicating passageways 32 between the duct 22 and the duct 29 on the exterior side of the rotor 30 and intercommunicating passageways 33 between duct 28 and duct 29 on the interior side of the rotor 30. These passageways 32 and 33 rotate with the rotor 30, and on exit from the passageways 32 there is a deflection of the flow of both the high and low energy streams 13 and 14 before they continue as a combined flow in duct 29.

The passageways 32 and 33 are configured so as to maintain the flow of the fluid streams 14, 15, 16 substantially irrotational.

In operation high energy fluid 14 is delivered to the chamber 22 through tangentially directed passageways 25. By this means a swirling motion is imparted to the high energy fluid in the chamber 22.

Interaction of the high energy swirling fluid 14 with the rotor 30 in the passageways 32 causes the rotor 30 to turn in the same direction as the swirling fluid 14.

Steady state pumping conditions are thereafter attained wherein the low and high energy fluid streams 14, 15 pass as a combined but unmixed stream 16 in the duct 29 with substantially non-dissipative transfer of energy between the two fluid streams 14, 15.

In general, fluid velocities in the embodiments of the device according to the invention as described above will be relatively low. Consequently, energy losses due to friction will also be relatively low. The device, however, may typically operate with relatively high rotor speeds and so the angular velocity of the power fluid within the swirl chambers 8 and 22 will also be relatively high.

There will, therefore, be significant losses due to friction where the high energy fluid 14 flows against the side walls of the swirl chambers 8, 22. There will also be losses in the regions where the low energy fluid 15 flows against the outer walls of the rotor 5, 30 and shrouds 9, 31.

Finally, there will be frictional losses associated with any bearings supporting the rotor 5, 30 and any seals between the rotor 5, 30 and inner housing 1 or outer casing 17. Liquid films between the rotor 5, 30 and inner housing 1 or block 30, and between the shrouds 9, 31 and casing 2, 17, may be utilised as an alternative to solid bearings and seals. In this alternative there will be an energy loss due to leakage of the high energy stream 14 and into the annular region 3, 4 and 28, 29.

The energy losses just detailed also occur in conventional compressor/turbine combinations. The total moving surface area, however, in the proposed device is much less than that for a compressor/turbine and so much higher rotational speeds should be possible before frictional losses become a limiting factor.

Consequently only one, as above, or two stages will be needed to effect the energy exchange. The device according to the invention will thus be extremely compact, highly efficient and particularly well suited, but not limited, to oil field pumping operations.

Claims (11)

1. A pump comprising first ducting means for passage of high energy pumping fluid, second ducting means for passage of low energy fluid to be pumped, third ducting means for passage of a combined pumped stream of said high and low energy fluid, means to provide a swirling motion to the high energy fluid stream relative to the low energy fluid stream, and rotor means for interacting the low energy and high energy fluid streams in rotation to form a combined yet unmixed flow with substantially non-dissipative transfer of energy from the high energy fluid to the low energy fluid thereby causing the pumping of said low energy fluid through said third ducting means.

2. A pump as claimed in claim 1 wherein said rotor means is provided with separate passageways for said high and low energy fluid streams from said first and second ducting means respectively and leading to said third ducting means such that on leaving the passageways the streams are mutually deflected during rotation of the rotor means to form said combined yet unmixed flow, said passageways being configured so as to maintain the flow of said high and low energy fluid streams substantially irrotational.

3. A pump as claimed in claim 2 wherein said separate passageways are formed around the periphery of the rotor means.

4. A pump as claimed in claim 3 wherein the separate passageways are formed on the one hand as by the spaces between vanes of the rotor means and on the other hand as by passageways in said vanes.

5. A pump as claimed in claim 4 wherein said first and third ducting means comprise a unified annular duct in communication through the spaces between the vanes of the rotor means such that the low energy fluid combines with the high energy fluid exiting the passageways in the vanes during rotation of the rotor means.

6. A pump as claimed in claim 5 wherein the first ducting means is a cylindrical bore surrounded by the second ducting means in the form of an annular duct.

7. A pump as claimed in any preceding claim wherein said means to provide a swirling motion to the high energy fluid comprises a series of spiral passageways for the high energy fluid between said first ducting means and said passageways in the rotor means.

8. A pump as claimed in any one of claims 1, 2 or 3 wherein said means to provide a swirling motion to the high energy fluid comprises an annular swirl chamber to which the high energy fluid is directed through tangentially directed passageways constituting said first ducting means.

9. A pump as claimed in claim 8 wherein said second ducting means is in the form of an annular duct surrounded by the annular swirl chamber.

10. A pump as claimed in claim 9 wherein said rotor means is arranged between the swirl chamber and the annular duct and the third ducting means in the form of an annular duct for the combined flow of high and low energy fluid streams.

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