US2852915A - Improvements in pressure exchanger scavenging - Google Patents

Description

Sept. 23, 1958 G. JENDRASSIK 2,852,915

I IMPROVEMENTS IN PRESSURE EXCHANGER SCAVENG'LNG Filed May 8, 1952 3 Sheets-Sheet 2 COOLER aymmm w 4 Attorneys P 23, 1958 G. JENDRASSIK 2,852,915

IMPROVEMENTS IN PRESSURE EXCHANGER SCAVENGING Filed May 1952 s Sheets-Sheet :5

\] DR/V/NG 44070:; 9% 0 3A 20 oo o 2? 7 I2 5 2 l8 /9 I lo /5/6 E5040 9 v I INVENTOR B 050%; J'f/vomss/k ATTORNEYS 2,852,915 Patented Sept. 23, 1958 ROVEMENTS TN EXCHANGER SCAVENGING George Jendrassilr, London, England; Andre t T. Boszormenyi and Clara Jendrassils, executors of said George .lendrassiii, deceased, assignors, by mesne assignments, to .lendrassilt Developments Limited, Lon don, England Application May 8, 1952, Serial No. 286,847

Claims priority, application Great Britain May In, 15 Claims. (Cl. 6i3-39.45)

This invention relates to pressure exchangers of the kind comprising a ring of cells in which gas is compressed and expanded, ducting to lead gas to and from the cells, and means to effect relative rotation between ducting and cells, the operation of the pressure exchanger involving the existence of a low pressure zone in which scavenging takes place, and a high pressure zone in which scavenging may also take place if necessary.

For the scavenging of the cells at low pressure it has previously been considered necessary to employ mechanical blowers or fans to produce the required gas current. 3y scavenging is meant the discharge and replacement of at least part of the gas content of a cell. This discharge and replacement may take place simultaneously, so that a continuous current of gas flows through the cells.

An object of the present invention is to avoid or reduce the waste of power involved in driving such blowing machinery and in general in effecting the scavenging.

The present invention, according to one aspect, provides a pressure exchanger comprising a ring of cells in which gas is compressed and expanded, ducting to lead gas to and from the cells, and means to effect relaiive rotation between cells and ducting, the operation of the pressure exchanger involving the existence of a low pressure zone in which scavenging takes place and 1-. high pressure zone in which scavenging may also take place if necessary, characterized in that the cells between the high pressure and low pressure zones are placed in communication with an extraneous source of gas at a pressure above the low pressure scavenging pressure, so that when the cells register with the low pressure zone they are already charged to a pressure sufficient to initiate and maintain the scavenging flow.

The gas from the extraneous source may be taken from a compressor. Alternatively it may form at least part of the useful gas output supplied by the pressure exchanger; thus, the gas may be bled from an intermediate stage of expansion of an expansion machine, a gas turbine, or a piston engine, supplied with working fluid by the pressure exchanger. In an extreme case, the extraneously supplied gas may represent the whole of the exhaust output of an expansion machine supplied with working fluid by the pressure exchanger, and this exhaust may represent the whole useful output of the pressure exchanger. The extraneously supplied gas may from any source, extraneous to the pressure exchanger, of gas at a suitable pressure temperature.

gas from an extraneous source may be introduced by a plurality of ducts supplying gas at mutually different pressures.

Specific examples of pressure exchangers according to the invention will now be described with reference to the accompanying drawings in which:

Figure l is a circumferential development showing one embodiment according to the invention.

Figure 2 is a circumferential development of a second embodiment and Figure 3 is a diagram illustrating a system compris ng a pressure exchanger according to Figure 2 and a turbine supplied with working fluid by the pressure exchanger.

Figure 4 shows a modification of the embodiment of Figure l.

in Figure l the rotor 1 of the pressure exchanger is shown in circumferential development together with the associated non-rotary parts. The rotor provides a ring of cells defined by radial partitions 1A. In the figure, movement of a cell from left to right, as shown by the or ow 2, represents the rotation of the rotor.

The stationary ducting concerned with high pressure scavenging of the cells comprises a combustion chamber 3, flame tube 3A, a duct 4 on the other side of the rotor, and ducting 5 which interconnects 3 and 4 to form a circuit in which gas flows in the direction shown 7y the arrows. Liquid fuel is supplied by the pipe 6 and injected into the combustion chamber 3, where it is burnt.

The ducting concerned with low pressure scavenging consists of an inlet duct '7 supplying fresh gas (air in the present case) and an outlet duct 8 through which the exhaust gas from the cells is discharged e. g. to atmosphere. Channels or pipes 9 are provided for the purpose of establishing communication between cells which have left the high pressure zone and cells which have left the low pressure zone so that by means of the pipes 9 there is an approximate equalization of pressure between the cells thus connected, involving a fall in the pressure of one cell of an interconnected pair and a rise of pressure in the other cell of that pair. This effect will be more clearly understood by considering the operation of the pressure exchanger as a Whole. Considering a single cell initially registering with the combastion chamber 3 and the duct 4, it will be appreciated that the gas content of this cell will be swept out by the scavenging process and replaced by hotter gas at a somewhat higher pressure (sufficient to make up the losses) coming from the combustion chamber. The pressure difference produced by combustion in the flame tube 3A will normally be sufficient to promote scavenging of the cells in communication with the high pressure inlet duct, constituted by the combustion chamber 3,

and the high pressure outlet duct 4. However, it may be necessary to promote the scavenging by the use of a fan 43 driven, for example, by an electric motor 49. Gr: leaving the high pressure zone the cell in its motion from left to right advances to the position 10 in which it is placed in communication with a cell at a position by one of the pipes 9. The initial pressure in the cell at 19 is less than that in the cell at 10, so that as soon the connection between these two cells is established there is a so-called exchange of pressure between them involving approximate equalization of pressure in th cells at lit and 19 and the pipe 9 interconnecting them. This equalization of pressure involves a flow of referred to for convenience as transfer gas) from the cell at if) to the cell at 19 by Way of the pipe 9 as indicated by the arrows. The cell at 10 then advances to the position 11 in which by way of a further pipe 9 it is connected to a cell in the position 18, so that a further pressure exchange takes place resulting in the approximate equalization of the pressures in the cells at it and 13. The cell at 11 then advances to the position 12 at which it is connected to another cell at 17 by a further pipe 9 so that the so-called pressure exchange occurs again. There are as many pipes 9 as may be necessary, but for simplicity three are illustrated. Thus a cell leaving the high pressure zone and approach- M) ing the low pressure zone 1 has its pressure lowered by three successive steps in moving, through the positions 1t), 11, 12, while on the other side of the machine a cell which has left the low pressure zone undergoes three successive steps of pressure. increase in moving through the positions 17, 18, 19. In the low pressure zone the residual gas content ofthe cells is expelled as exhaust by a scavenging process and replaced by cool gas (air) and; the cells in continuing their motion have their pressureagain built up by steps in passing from 17 to 1.5.

In the present case the pressure exchanger is considered as an apparatus for supplying hot gas at high pressure for expansion in a turbine or other expansion prime moversueh as ,an expansion engine. The supply of gas forthis purpose is withdrawn by way of the duct 20.

t; is ,desirableto promote and maintain the necessary scavenging flow through theducts 7 and 8 and the cells e ster n With hem, W thQ lt; recourse to fans or blowers in the duets,7 on.-8, -except possibly when starting the machine.

In order; to achieve-this enda duct 21 is provided for theypurpose of establishing a connection with cells which have just left the-low pressure zone and introducing into them gas from an extraneous source at a pressure somewhat higher than that prevailing in the low pressure scayengingductsj, 1 8 or in the cell just severed from these ducts. The duct,- 21 may be supplied With gas from n mechanicalcornpressoror otherwise, diagrammatically illustrated at, 23 and driven by a motor 50. Thus a cell leaving the low pressure scavenging zone and reaching the position lS will have its pressure raised by the inflow of gas from the duct 21. Further increases in pressure take place through the normal pressure exchanging process, when the ,cell successively rea hes the positions 17, 18, 19, theserises in pressure being at the expense of successive falls, in pressure at the positions 10, 11, 12. However, whenthecell at 12 communicates by way of the pipe9 with the cell at 17, the pressure inthe latter cell has alreadybeen raised by influx of gas from the duct 21. Thus the residual pressure in the cell at 12 when it reaches 13 will be higher, so that whenthe cell reaches the position 154; its residual pressure is high enough to initiate a flow of gas, in the directionindicated by the arrow 14A, of sufticjent; velocity to etfect the scavenging gas current in the ducts 7 and 8. It will be observed that the cell in the course of its travel communicates first with the duct, 8..and then with the ;duct 7. This sequence of establishing communication withducts 8 and 7 will cause the contents of thecellat 14 to accelerate in the direction of the arrow14A. If the, severanceofuthe cell from the ducts, 8. and 7 is, eifected in the Opposite sequence (see Figure l) i. e.;the cell is firstclosed at its downstream end (duct 8) and then at; its upstream end (duct 7), then dueto the inertia of gases in the cell the pressure therein is raised, ausing a certain supercharging effect. The pressure in duct 21 must always be higher than the pressure in the cell after severance of the cell from the scavenging ducts. The effect of the gassupplied by the duct 21, will bethatthe pressure in the cells all around the rotor is stepped up. It may thus be possible to dispense with some of the pipes 9 and thus reduce the number of the, pressure exchangesinvolved in a complete rotation of the cell rotor.

In the;exampl e illustrated ;a secondduct 22 supplying extraneous gasis provided and the arrangement is such thatthe gas supplied by 22 is at a higher pressure than thatsupplied by 21; This may be conveniently done by leadingthe, duct. 22 from the final stage of the compressor 23 and 'the duct 21 from an intermediate stage or from corresponding stages of anexpansionmachine (note Figure. )j.

The supply of extraneousgas may alternatively be taken frornan expansionenginqe. g., a turbine supplied with working fiuidby theduct (see Figure 3).

When a cell arrives at the positionlS vand first. regis- '4': ters with the duct 21, an impulse wave is propagated through the gas in the cell, and travels to the further end. of the cell where it is reflected and returns towards the duct 21. Preferably, the communication between a cell and one of the extraneous gas ducts is of about the same duration as the time taken for such an impulse to return to the opening of the extraneous gas duct, after reflection from the other end of the cell. By proper timing it is possible to obtain in the cell a higher pressure than thatprevailing in duct 21 and/ or 22.

it is preferable that communication between a cell and the duct 21 or 22 should be severed before the other end of the cell is in effective communication with one of the pipes 9.

in practical operation it is sufiicient however if the severance of cell at 715 from ducts 21 or 22 is etfected before the impulse in that cell caused by the higher pressure in duct 9 reaches duct 21 or 22. Thus it is well possible that geometrically a cell may communicate simultaneously with duct 21 or 22 and with one of the pipes 9, but due to the speedof the rotor this will not matter.

Figure 4 shows a modification of Figure 1 in which, instead of introducing the extraneous gas through the ducts 21, 22, the extraneous gas is introduced into the cells beforethey have reached the low pressure zone,. by means of a duct 24 to which gas is supplied by the compressor 23. In this case the pressure of a cell in the position 13 is raised so that on reaching the position 14 the scavenging current may be initiated. The cell at position 13 should preferably cease to communicate efiiectively with the pipes 9 before it begins to register with the duct 24. The cell in the position 13 is; severed from effective communication with the duct 24 before that cell registers with the scavenging duct 8.. Thus, a duct may be in the position shown in Figure 1, while the duct 22 may be. located opposite, on the same side of the rotor as the duct 8.

Referring now to Figure 2, ,this illustrates the type of pressure exchanger embodying two oppositely rotating substantially coaxial cell rotors, the arrangement being such that channels which are equivalent to the pipes 9 in Figure l establish communicationubetween the cells of, one rotor and the cells of the other. rotor. Explaining this .in more detail with reference to the drawing it will be seen that the machine comprises twocontra-rotating rotors 25, 26 shown in circumferential development. The arrangements for high pressure scavenging and combustion, and the abstraction of the usefulgas output are-substantially similar to Figure 1 and need not be described. The rotors are scavenged in parallel at low'pressure by means of ducting 27, 28 associated with the rotor 25 and ducting 29, 30 associated with the rotor 26, the direction of the scavenging gas flow being indicated by the arrows. The passages 31 form the equivalents of the pipes 9 in Figure 1 and serve to connect the cells of rotor 25 with those of rotor 26. Consider for example the extreme left hand cell of rotor 25 which is coming from the high pressure zone. This cell on reaching the position A is placed into communication by way of a channel 31 with a cell .V in the other rotor 26 and the so-called.exchangc of pressure, occurs between the cells thus interconnected. By means of the channels 31 contact is successively made between pairs of cells BU, CT etc. so that in the rotor 25 a cell in moving from A to C undergoes a series of successive steps of pressure fall while. correspondingly a cell in rotor 26 in moving from position T to position V undergoes a series of successive steps of pressure rise. An exactly comparable process occurs on the other side of the rotors as between the cells EFG and PQR etc.

So far as the supply of gas from the extraneous source is concerned the arrangements are very similar to what is shown in Figure 1. In the present case gas from an extraneous source at a pressure higher than that prevailing in the low pressure scavenging zone is supplied to cells of each rotor which have just left that zone, this supply being by way of the duct 32 as regards the cells of the rotor 25 and by way of the duct 33 as regards the cells of rotor 26. The ducts 32 and 33 are both connected to a compressor such as 23 (Figure 1). Alternatively they are supplied with gas taken from an expansion engine supplied with working fluid by the pressure exchanger, e. g. as shown in Figure 3 or otherwise.

Figure 3 is a diagram of a pressure exchanger and a gas turbine arranged in combination according to the present invention. The pressure exchanger, which is indicated in external outline only, is substantially according to Figure 2 and comprises a pair of coaxial contra-rotating rotors 25, 26. The rotors are scavenged in parallel at low pressure; the scavenging gas e. g. air at atmospheric pressure enters at 27, 29 and the exhaust products from the rotors emerge by way of a twin exhaust 28, 3d. On the high pressure scavenging side each rotor is associated with ducts 35, 36 having combustion chambers 37, 38 which function independently of each other. The combustion chambers contain flame tubes 37A and 38A respectively, each with fuel supply pipes 6. The supply of useful gas is taken off by a duct 39 and supplied to a multi-stage gas turbine 40 from which shaft power is taken. The exhaust of this turbine is discharged mainly at 41, 'but a proportion of the working fluid is bled off at an intermediate stage of expansion by way of the pipe 42 which by way of further piping 43, 44 supplies the extraneous gas to rotors. The pipe 43 is connected to the duct 32' (Figures 2 and 3) and the pipe 44 to the duct 33. It is advantageous to cool the extraneous gas before introducing it into the ducts 32, 33 and therefore coolers are provided at 45 for this purpose. Throttle valves 46 are also provided in the pipes 43, 46.

What I claim is:

1. In a pressure exchanger comprising a first and a second element mounted coaxially for relative rotation, said first element defining a series of open-ended cells extending therethrough, said second element including first inlet means to allow the introduction of a low pressure fluid into said cells, outlet means defining a low pressure scavenging zone to allow scavenging of low pressure fluid from said cells and a second inlet means circumferentially displaced from said first inlet means to allow the introduction of a high pressure fluid to said cells, said elements so connected that the pressure of the low pressure fluid is raised and the pressure of the high pressure fluid is lowered in said cells during relative rotation of said elements, the improvement comprising further inlet means in said second element to introduce into a cell in the vicinity of said low pressure scavenging zone at a position where said cell is otherwise effectively closed, an extraneous fluid at a pressure in excess of the pressure prevailing in said low pressure scavenging zone.

2. In a pressure exchanger comprising a first and a second element mounted coaxially for relative rotation, said first element defining a series of open-ended cells extending therethrough, said second element including first inlet means to allow the introduction of a low pressure fluid into said cells, outlet means defining a low pressure scavenging zone to allow scavenging of low pressure fluid from said cells and a second inlet means circumferentially displaced from said first inlet means to allow the introduction of a high pressure fluid to said cells, said elements so connected that the pressure of the low pressure fluid is raised and the pressure of the high pressure fluid is lowered in said cells during relative rotation of said elements, the improvement comprising further inlet means in said second element to introduce into a cell before it is placed in communication with said low pres sure scavenging zone and at a position Where said cell is otherwise efiectively closed, an extraneous fluid at a pressure in excess of the pressure prevailing in said low pressure scavenging zone.

3. In a pressure exchanger comprising a first and a second element mounted coaxially for relative rotation,

said first element defining a series of open-ended cells are tending therethrough, said second element including first inlet means to allow the introduction of a low pressure fluid into said cells, outlet means defining a low pressure scavenging zone to allow scavenging of low pressure fluid from said cells and a second inlet means circumferentially displaced from said first inlet means to allow the introduction of a high pressure fluid to said cells, said elements so connected that the pressure of the low pressure fluid is raised and the pressure of the high pressure fluid is lowered in said cells during relative rotation of said elements, the improvement comprising further inlet means in said second element to introduce into a cell after it has been placed in communication with said low pressure scavenging zone and at a position where said cell is otherwise eliectively closed, an extraneous fluid at a pressure in excess of the pressure prevailing in said low pressure scavenging zone.

4. In a pressure exchanger comprising a first and a second element mounted coaxially for relative rotation, said first element defining a series of open-ended cells extending therethrough, said second element including first inlet means to allow the introduction of a low pressure fluid into said cells, outlet means defining a low pressure scavenging zone to allow scavenging of low pressure fluid from said cells and a second inlet means circumferentially displaced from said first inlet means to allow the introduction of a high pressure fluid to said cells, said elements so connected that the pressure of the low pressure fluid is raised and the pressure of the high pressure fluid is lowered in said cells during relative rotation of said elements, the improvement comprising further inlet means in said second element, said further inlet means defining a passage positioned in communication with said cells at a point where cells in communication with said passage are otherwise eflectively closed and circumferentially spaced from said low pressure scavenging zone so that a source of extraneous fluid at a pressure in excess of the pressure prevailing in the low pressure scavenging zone can be introduced into said cells as they come in communication with said passage.

5. In pressure exchanger as defined in claim 4 the further improvement of said passage being placed in communication with said cells before said cells enter said scavenging zone.

6. In a pressure exchanger as defined in claim 4 the further improvement of said passage communicating with said cells after said cells have left said scavenging zone.

7. in a pressure exchanger as defined in claim 1 the further improvement of said first inlet means and said outlet means being circumferentially staggered so that a cell will be placed in communication with said outlet means first.

8. A pressure exchanger combination comprising a first and a second element mounted coaxially for relative rotation, said first element defining a series of open-ended cells extending therethrough, said second element including first inlet means to allow the introduction of a low pressure fluid into said cells, outlet means defining a low pressure scavenging zone to allow scavenging of low pressure fluid from said cells and a second inlet means circumferentially displaced from said first inlet means to allow the introduction of a high pressure fluid to said cells, said elements so connected that the pressure of the low pressure fluid is raised and the pressure of the high pressure fluid is lowered in said cells during relative rotation of said elements, extraction means communicating with said cells for withdrawing from a cell fluid at a relatively high pressure, expansion means for performing useful work operable by fluid withdrawn through said extraction means, and means to return a portion of the fluid from said expansion means to a cell of said cell ring in the vicinity of said low pressure scavenging zone and at a position where said cell is otherwise effectively closed, the pressure of said returned fluid being in excess of the pressure prevailing in said low pressure scavenging zone.

9. The combination defined in claim 7 wherein said expansion means is constituted by a gas turbine.

10. The combination defined in claim 8 including the provision of a bleed channel connected at an intermediate expansion stage ofv said turbine to function as the means to return fluid to said cell ring.

11. The combination defined in claim 8 wherein said fluid is returned to a cell about to be placed. in communication with said low pressure scavenging zone and at a position where said cell is otherwise effectively closed.

12. The combination defined in claim 8 wherein said fluid is returned to a cell after it has been placed in communication with said low pressure scavenging zone and at a position Where said cell is otherwise efiiectively closed.

13. A pressure exchanger comprising a ring 01: ceils in each of which gas is compressed and expanded, heating means associated with cells containing gas undergoing compression, ducting to lead gas to and from the cells, part of the said ducting communicating with cells containing gas at a low pressure to constitute a low pressure scavenging zone, means to effect relative rotation between the cell-ring and the ducting, and passage defining means, forming part of the said, ducting, positioned in communication with the cell-ring in the vicinity of the said lowpressure scavenging zone and at a position where a cell registering with the said passage defining means is otherwise effectively closed and also positioned in communication with an extraneous source of gas at a pressure greater than that prevailing in the said low pressure scavenging zone.

14. Apressureexchanger comprising a ring of cells in each of which gas is compressed and expanded, heating means associated with cells containing gas undergoing compression, ducting to lead gas to and from the cells, part of the said ducting communicating with cells containing gas at a low pressure to constitute a low pressure scavenging zone, means to effect relative rotation between the cell-ring and the ducting, and passage defining means, forming part'of the said ducting, positioned in communication. with the cellring immediately before the said ducting of the low pressure scavenging zone in the direction ofthe saidrelative rotation, and at a position where a cell registering with the said passage defining means is otherwise eifectively closed, and-also positioned in communication with an extraneous source of gas at a pressure greater than that prevailing in the said low pressure scavenging zone.

l5. A" pressure exchanger comprising a ring of cells in each of which gas is compressed and expanded, heating means associated with cells containing gas undergoingcompression, ducting to lead gas to and from the cells, part of the said ducting communicating with cells containing gas at a low pressure to constitute a low pressure scavenging zone, means to effect relative rotation between the cell-ring and the ducting, and passage defining means, forming part of thesaid duct, positioned in communication with the cell-ring immediately after the said ducting of the low pressure scavenging zone in the direction of the said"relati've rotation, and at a position where a cell registering, with the said passage defining means is otherwise efiectively closed, and also positioned in communication with an extraneous source of gas at a pressure greater than that prevailing in the said low pressure scavengingz'one.

References Cited' 'in the file of this patent UNiTED STATES PATENTS 2,399,394 Seippel Apr. 30, 1946 2,461,186 Seippel Feb. 8, 1949 2,513,601 Traupel July 4, 1950 2,526,618 Darrieus Oct. 24, 1950 FOREIGN PATENTS 8,273" Great Britain Apr. 5; 1906'

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