US1989636A - System for producing refrigeration - Google Patents

Description

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-H. i5. EDWARDS SYSTEM, FOR PRODUCING REFRIGERATION Filed Nov. 20, 1933 Patented Jan. 29, 1935 I I I UNITED STATES PATENT OFFICE 1,989,636 SYSTEM FOR PRODUCING REFRIGERATION Harry D. Edwards, Larchmont, N. Y., assignor to The Linde Air Products Company, New York, N. Y., a corporation of Ohio Application November-.20, 1933, Serial No. 698,794 In Cuba April 23, 1932 17 Claims. (01. 62-123) This invention relates to a system for producplified in the construction hereinafter set forth ing refrigeration, and more particularly to an and the scope of the application of which will be improved method and apparatus for producing indicated in the claims.

refrigerating effects by compressing and expand- For a fuller understanding of the nature and ing air to be separated into oxygen and nitrogen objects of the invention, reference should be had 5 constituents by rectification. to the following detailed description taken in con- The invention has for its object generally an nection with the accompanying drawing, in improved construction and'arrangement of parts which: in gaseous cooling and/or separating systems Fig. 1 is a schematic view partly in section and which are eflicient, economical and readily manupartly in elevation showing means for accom- 1'0 factured. plishing thermodynamic operations on a gaseous More specifically, the invention has for its obmedium used in producing refrigeration in acject the provision of an arrangement, in which a cordance with the invention. gaseous medium is compressed, cooled and ex- Fig. 2 is a fragmentary view showing in detail panded, for utilizing the expansion to do external regulating mechanism of a character employed 15 work for driving compression machinery in a in conjunction with certain expansion machinery manner which is advantageously reliable, efiishown in Fig. 1; and cient and economical in operation. Fig. 3 is a fragmentary sectional view taken Another object is to separate the compression on the line 3-3 in Fig. 2.

machinery which preliminarily compresses the The use of expansion engines for producing low 20 gaseous medium to be supplied to refrigerating temperatures is well known in the art of refrigapparatus, such as that in which a liquefied gas eration, and it has heretofore been proposed to is produced, into main compressing stages and utilize the energy made available-by the expanboosting compressing stages and utilize expansion sion of the medium supplied to such engine. No

of at least a part of the compressed medium by satisfactory arrangement, however, has been doing external work to operate the boosting stages heretofore proposed for employing such engines in a manner which tends to accommodate itself in gas liquefaction systems of the present type, tochanging loads without undue strain and waste. because the proper power distribution was not It is also an object to provide a system for proclearly recognized. In general, either the motive 0 ducing refrigeration having both throttling and power available was not properly'accommodated engine expanding devices so constructed, related to variations in load, or a proper proportion of and proportioned that, when there is a tendency the load was not allocated to the expansion for the refrigeration effects of the throttling and engine.

engine expanding devices to become unbalanced In the production of gases separated from the and supply refrigeration in disproportionate atmosphere, particularly in the production of amount, there is inherent capability in the sysoxygen,- expansion engines, geared to various tem of restoring the balance, whereby t system fixed loads, have been tried to provide some reprovided is self-regulating. frigeration. Changing conditions in the refrig- S ill an h Obj is 11 p v a system of eration to be provided, however, made the operathe character indicated with expansion means tion of uch engines irregular and interruptions 4 arranged to accomplish a p O t expansion by and cessation of service not infrequently occurred. d in ter W h o tling and the balance Two different methods of gearing such engines to y doing external Work in a predetermined ratio the load were, in general, practiced; for example, to the former; arr m n eing made to vary the engine was geared or belted to a compressor the xpan n doing external w ti ly which was positively driven or assisted by an elec- 45 as als man l y, to eeeemmedate it to v n tric motor, or similar prime mover, so as to be run refri erati n a refrigeration requirements at a constant speed, or it was geared to drive an Other Obje ts of t invention Will in P he electric generator which was connected to a bank. obvious and w in Part appear he einaft of lamps or other resistance load. which wasted This application is a continuation in part of or dissipated the energy of expansion.- In cases 50 my eepending application which issued y 29, where the first method was practiced, the varia- 1934 as Pate o. 1,960,623- tions in the load imposed such service stresses on The invention acc r in y p i es the fea-. the gearing or belting that it'was'relat'ively short tures of construction, combination of elements, lived. In practice, the second method was genand arrangement of parts, which will be exemerally preferred. 5;,

In the practice of the present invention, the compressing machinery is divided into a main part which does the main work of compression and into a boosting part which compresses to a still higher pressure than in the main part and has an expansion engine geared to drive the latter part, or booster; the energy for driving the main part being independently supplied. This permits the regulation of the expansion engine to respond to variations in the refrigeration load as well as avoiding undue strains in the connection gearing. Also, in the preferred form, it is proposed to expand a part of the gas at high pressure by throttling at low temperatures to produce a high quality refrigerating eflect under the Joule-Thomson principle, and to expand the balance through the expansion engine with external work usefully applied in the booster, to give a lower quality but large quantity refrigerating effect. In the system where the two effects are utilized, arrangements are provided to control the ratio between the volumes separately expanded, the two expansion means being operated in parallel.

The present invention provides means for counteracting tendencies toward variation in speed of the booster-expander and to maintain a substantially constant refrigerating effect in the gases delivered by the system to a rectifying column. It also provides a balance in both respects automatically and in spite of variations in the conditions affecting the system. The. factors which effect the accomplishment of these ends include, in the embodiment shown, a substantially constant rate of delivery from the main compressing means to the booster, the operation of the booster by other means, namely, an expansion engine device coupled to the booster and driven by the power produced in the expansion of a portion only of the booster output, a ratio of expansion in the expansion engine substantially greater than the ratio of compression in the booster, and themaintenance of open and communicating passages from the outlet of the booster to the throttling valve and to the intake of the expansion engine, so that the pressure will rapidly equalize between these points.

There are inherent difficulties in obtaining the desired equalization in a system using a throttling valve, as here proposed, since the throttling valve may clog and interfere with the desired flow of gas into the rectifying column. Pressure within the passages which communicate with the throttling valve, in consequence, tends to rise and produce a slight increase in the power available to the expander. This tends to cause the expansion engine 'to' increase its speed. However, the mechanical coupling would cause an equal tendency to increase the speed of the booster, which would tend to diminish the pressure in the gas which is'being supplied to the booster at a constant rate and increase the ratio of booster compression. Thus the added work imposed upon the booster would absorb the tendency of the expander to increase speed and quickly and automatically restore the desired normal balance.

If, on the other hand, the flow of throttled gas is increased as, for example, by the removal of an obstruction, the first result is a reduced pressure in the lines which are connected with the throttling valve, and a slight reduction in the power available to the expander with a tendency for the latter to reduce its speed. Again, this tendency is offset by the mechanical connection to the booster and the reduction in booster compression ratio which always results when the speed of the booster is so reduced as to increase the pressure in the gas which is being supplied to the booster from the constant speed compresors.

In either case, the effect -is to counteract any tendency toward a continuance of a departure from desirably balancedconditions. It is also seen that the system automatically adapts itself during these variations to deliver a desired predetermined refrigerating effect to the'rectifying column. For example, any reduction in volume of throttled gas admitted to the column at high pressure is offset by increased pressure both in the throttled gas and-in the expanded gas delivered from the expansion engine. The converse is equally true when the volume of throttled gas is increased.

Referring now to the drawing and particularly to Fig. 1, 10 denotes a first stage cylinder of a main compressor which effects a portion of the preliminary compression of the gaseous medium to be supplied to a gas liquefying and rectifying apparatus, shown generally at 30, the gaseous medium being supplied to the cylinder 10 by way of an inlet conduit 11 which conveys the gaseous medium from any suitable source, for example, from the atmosphere when filtered and cleaned. The gaseous medium when compressed in the cylinder 10 is discharged intoa second stage compression cylinder 12, where the gaseous medium is further-compressed, after which it is discharged to a third cylinder 13, where another stage of preliminary compression is accomplished, and finally to a cylinder 14 where a still further stage of compression is accomplished, the gaseous medium being thereby raised to'a desired high pressure, for example, to 140 atmospheres, or approximately 2100 pounds gage pressure in the case of air. The pistons for the several stages of compression preferably have the same stroke but progressively decreased diameters, and are here shown on a common crank shaft 15, which has a fly-wheel 16 belted or otherwise geared to be driven from an electric. motor 1'7. Interstage cooling is preferably practiced in connection with the conduits, which convey the compressed medium from one stage to another. For example,

conduit 18 is shown as leading from the outlet a coil 22 provides the cooling surface in the con.-

duit 21, which leads from the outlet chamber of cylinder 12 to the inlet chamber of cylinder 13. Similarly, a coil 24 provides cooling surface in the conduit 23, which leads from the cylinder 13 to the cylinder 14. A conduit 25 having a cooling coil 26 is arranged to convey the gaseous medium now at the desired pressure and temperature tov the second part of the compression machinery.

The compression machinery to which the conduit 25 leads comprises a cylinder 27 for accomplishing further compression of the gaseous medium and boosts the pressure to a still higher value, for example, to a pressure of 200 atmospheres or approximately 3000 pounds gauge in the case of air. The compressed medium at this highwhile the other is conveyed through conduit 31 to a cylinder 32, where expansiontakes place by doing external work and is then supplied through the conduit 33 in parallel with that portion supplied through conduit 29 to the column 30. The desired quantity ratio to be generally maintained between the two portions is determined firstly, by the displacement of the expan sion engine; secondly, by the time during which the inlet valve of this engine is open; and thirdly, by the opening of the expansion valve 29". For example, in the case of air, it is usually preferable that the expansion engine be of such capacity that it will expand of the compressed air from the pressure of 3000 lbs. gage to the column pressure of '75 lbs. gage for the production of the desired relatively large quantity of relatively lower quality refrigeration and that therefore 60% of the air will pass through conduit 29 to be precooled to a relatively low temperature by exchanger 29' and expanded through the expansion valve 29" to obtain the desired high quality refrigeration within the column 30. The expansion means which thus does internal work with the compressed medium and the expansion engine which does external work, operate in parallel and finally expand the medium to a relatively low pressure, for example, to a pressure of 5 atmospheres in the case of air, i. e., the medium thus expanded is supplied to column 30 at approximately '75 pounds gage pressure. It will be noted that the gaseous medium is here expanded in the expansion engine to a pressure materially lower than thepressure at which it is Supplied to the compression cylinder 2'7.

in order that the expansion engine having cylinder 32 may do useful work, in accordance with the invention, this engine is coupled to drive the boosting compressor at 2'7. Any suitable mechanical connections that allow the expansion cylinder to operate expansively after admission cut ofi may be employed, for example, a system in which the pistons of the expansion engine and boosting compressor are connected by connecting rods 34 and 35, respectively, to a common crank 36, which has a fly-wheel 3'7. By this arrangement, the external work which the gaseous medium does in driving the expansion engine is transmitted to the boosting compressor 2'7. Column 30 is shown as provided with outlet connections 39 and 40, from which liquid and gaseous products are withdrawn, respectively, for example,

, ated. In this manner, substantially all the work done by, the engine 32 is usefully employed in accomplishing the elevation of the gaseous medium to a higher pressure.

Where the refrigeration load tends to vary between very wide limits or where changes inthe load to be normally carried are to be accommodated, it may be desirable also to provide manual adjustment for the admission valve mechanism. This may be conveniently provided in connection with the valve gear on shaft 41, that connects the crank 36 with the flywheel 3'7. This gear is shown in Fig. 2 as comprising a cam 42 that actuates a reciprocating rod 43 having a cam wheel or roller 44 mounted in its end and bearing on the cam 42. The other end of this reciprocating rod has an articulated portion 45 which makes variable engagement with a valve operating lever 46, the latter being pivoted at 47 to operate a spring closed poppet valve 48 mounted in the head of the expansion engine to control the admission of the compressed medium to be expanded. A valve 49 is also shown in the head of cylinder 32 for controlling the outflow into the conduit 33, and

is actuated in any manner desired. In order that the articulated portion 45 may make variable engagement with the actuating lever 46, a cam roller 50 is pivoted in its end which bears against 32, and has an operating rod 54 which is moved in response to variations in such load; this movement may be eifected manually or automatically, a manually manipulated nut 55 being here shown for locking the rod. 54 in place.

In operation, it is seen that the gaseous medium which is to be compressed, cooled and expanded, is drawn in from the atmosphere through the conduit 11 to the main compressing stages, where a desired high pressure is obtained, the energy for driving these compressing stages being delivered by the motor 1'7. The compressed gaseous medium which has been subject to interstage cooling then passes through conduit 25 to the boosting compressor 27, after which it is divided into two portions, in accordance with the predetermined ratio, one portion passing by way of the conduit 29 through heat exchanging means 29' where it is pre-cooled by thermal contact with a cold product and through the throttling valve "29" into the column 30, while the other portion is passedby way of conduit 31 to the expansion engine 32, where the compressed gaseous medium delivers its energy to do external work and drive the boosting compressor 27, after which it is supplied through conduit 33 to the column 30; these portions being utilized together to accomplish the liquefaction and/ or separation of gas in an economical manner in the column 30. Here, it is seen that the two expansion means, the first of which does internal work on the gas, while the second does external work, operate inparallel.

The proportion of high quality refrigeration to low quality-large quantity refrigeration may be changed through a relatively moderate range by adjusting the degree of opening of the inlet valve 48 on the expansion cylinder. Thus to effect an increase of this ratio, the articulated portion of the-rod at 45 is moved outwardly from the cylinder head by causing the rod 54 to move inwardly. Thus, it is seen that the actuating stroke of the lever 46 is reduced, so that the inlet valve 48 admits less compressed medium to be expanded. Consequently, less power is generated in the expansion. cylinder, so that the engine will slow down slightly until a new balanced condition is reached. In practice, it is seldom necessary to adjust the ratio by means of the adjusting rod 54, as the fine adjustments to the demand for reirigeration are obtainable with the valve 29", as well as automatically, as above described.

In a system of the present invention,. a bal-' anced condition is always automatically reached both when the proportions of air flowing are changed as described above and when there is any change in the refrigeration load such as would be caused 'by slight obstructions at the expansion valve 29". It will be readily seen that a new balanced condition is automatically reached, since by reason of the mechanical coupling of booster to expander, the constant rate at which gas is delivered from the initial compression to the boostenand the greater ratio of variation in booster work as compared with expander power with any given change in speed, any tendency for the speed of the expansion engine to change is immediately taken up by the booster so that it adjusts itself and the power produced is equal to the power consumed. In the case of air, the ratio of expansion in the engine is the ratio of compression in the booster is a proximately v If the throttlingvalve 29" should be closed slightly as by a slight obstruction, there is a tendency for the pressure in conduit 31 to rise. If, for example, this pressure rises from 3000 to 3100, slightly more air will expand through a slightly increased expansion ratio, i. e.

Consequently, the power output increases slightly and the speed would tend to increase. But at the booster cylinder, the mass per unit of time of air handled is constant while the compression ratio change is at first booster will tend to fall off at a greater rate, thus preventing the slowing down. Friction can be neglected as it is practically constant within the range of operating conditions considered.

-I The inherent balancing tendency is the more positive when all the air passes through the booster cylinder and only apart of the air is expanded in the expansion-engine, for then the expansion ratio can be sufflciently greater than the compression ratio ofthe; booster. For exis thrown upon the main compressor.

- cooling and is not far from ample, when the proportion of air expanded through the expansion valve is 60% to 40% expanded in the engine, the inherent stability of the system :is very great.

When the power output of the engine is de- 6 creased-by decreasing the degree of opening of the expansion cylinder inlet valve, i. e., by providing an earlier cut-off, the engine tends to slow down, thus decreasing the displacement of the booster cylinder so that it can handle only 10 a smaller volume of air, but since the quantity or mass per unit of time of air being delivered by the main compressor is practically constant, the pressure in conduit 25 of air entering the booster will rise so that its volume is decreased to a value equal to the decreased displacementv of the booster. Compression, therefore, occurs through -a smaller compression ratio and less power is used by the booster, while more work The use of a coupled booster-expander as here proposed permits more economical starting. At the beginning of ,operation, it is desirable to speed up the cooling of the apparatus and the condensing of considerable air which are prerequisite to rectification. Therefore, at the beginning it is necessary to provide a relatively great refrigerating eflfect even at the expense of high quality. This is accomplished in practice by passing a relativelylarge quantity of air through the engine until the apparatus reaches the exhaust temperature of the engine, then switching to the ratio of engine expanded to throttled air which gives a desired Joule-Thomson the usual operating point.

Since the dimensions of the expansion engine are fixed, increasing the amount of air to the engine results in lowering the ratio of expansion and increasing the pressure and temperature at 40 the point of exhaust, and the temperature of the exhaust gas leaving the engine. In the'boosterexpander the speed increases with the "larger cut-off, so that the cut-01f does not have to be quite so great to handle a definite increase in volume. Consequently, the exhaust temperature of the booster-expander engine is lower than that of av constant speed engine. Thus, during the first period of starting up, more heat is removed per pound of gas processed, and also the first period is continued to slightly lower temperature which is more economical because en- 'gine cooling is more efiicient than Joule-Thomson cooling.

The stabilization effect operates to neutralize substantially any disturbance arising because of the fact that the opening at the orifice of valve 29" changes slightly from hour to hour. Such changes are produced by carbon dioxide snow and possibly some water snow forming on .and 0 then flaking off the valve. When, due to flaking off of such snow, a slight additional opening of the valve 29 occurs in a cycle in which an expansion engine runs at constant speed, the

head pressure falls, and since the amount of 5 air through the expansion engine is directly proportional to the suction pressure and the speed, it also fails. Thus the ratio of the amount of engine expanded air to throttled air may fall markedly. However, in the case of the selfgoverning booster-expander, a drop in the high pressure, causes the'engine to speed up since the ratio of compression is decreased more than the ratio of expansion. This increase in speed compensategfor the decrease in pressure. Both paths for the air, that is, those through conduits 31 and 29 respectively, are opened, and the ratio of engine expanded to throttled air is maintained more nearly constant. This constant ratio of high to expanded air which is obtained by the use of the booster-expander has a marked efiect in securing a stable operation.

The boosting compressor and expansion engine may be designed from the engineering data generally applicable to machines of their kind. The volume of gaseous medium to be handled through the two machines being assumed, together with the pressure change across each, the boosting, compressor and expansion engine can be built of such size as to run at any predetermined speed. The highest pressure in the system, which is reached between the boosting compressor and the expansion engine, is an important datum, and must be of the proper degree in order that the system may operate as intended. The system has been proved to be inherently stable, and if the piston displacement of the boosting compressor, and that of the expansion engine are of the proper magnitude, all pressures and speeds remain substantially constant at their intended values. I

Since certain changes may be made in, the above construction and difierent embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is: 1. The method of compressing and expanding a gaseous medium to produce a liquefied gas which ternal work in effecting said further compres sion, and automatically maintaining the volume of the medium liquefied substantially constant when the ratio of the portion expanded internally to that expanded externally changes.

2. The method of compressing and expanding a gaseous medium to produce a liquefied gas which comprises compressingthe gaseous medium at a substantially constant rate by means of energy independently supplied, further compressing the compressed medium at a rate which may vary, cooling the compressed medium by heat exchange, engine expanding at least a portion of the compressed medium, utilizing the energy obtained from said engine expansion to do the work of saidfurther compression, throttle expanding the remaining portion of the compressed medium, and counteracting the efiect of an interference with the rate of throttle expansion to change the volume of gaseous medium liquefied by changing the rate at which said work is done.

3. The method of compressing and expanding a gaseous medium to produce a liquefied gas .which comprises compressing the gaseous medium at a change, dividing said cooled compressed medium into two parts in accordance with a desired ratio, effecting throttling expansion of one of said parts, engine expanding the other part, utilizing the energy obtained from said engine expansion to do the work of said further compression, and automatically changing the rate at which said external work is utilized in response to changes in the rate at which said throttling expansion takes place whereby the volume of the medium liquefied remains substantially constant.

4. The method of compressing and expanding air in a system having compression devices arranged in series and expansion devices arranged in parallel for producing a refrigerating efiect .which comprises compressing the air drawn from the atmosphere at a substantially constant rate, cooling the same by heat exchange, further compressing the cooled compressed air at a rate determined by a predetermined pressure difierential in the system, further cooling the same by heat exchange, dividing said further cooled compressed air into two portions in accordance with a predetermined ratio, further cooling one of said portions by causing the same to expand and to do internal work, further cooling the other of said portions by expanding the same and causing the same to do external work, the ratio of expansion for said last-mentioned portion being substantially greater than the ratio of compression accomplished when effecting said step of further compression, supplying energy independently to accomplish the compression at said constant rate,

applying the energy released by having one of said portions do external work for accomplishing the step of said further compression, and compensating any tendency to change the ratio of the portion expanded by doing internal work by a correlated tendency in the portion expanded by doing external workwhereby the volume of liquefied medium produced remains substantially constant. g 1

5. The method of compressing and expanding a gaseous medium to produce a refrigerating effect which comprises supplying independently the energy for efiecting the step of initially raising the pressure of a gaseous medium from an initial low-pressure to a relatively high pressure, cooling the same by heat exchange, boosting the pressure of said compressed medium to a still higher pressure, again coolingv the medium by heat exchange, dividing said compressed medium into two portions and expanding the same in parallel by causing the same to do internal and external work respectively, applying the energy released in doing external work to accomplish the step of boosting the medium to said higher pressure, and utilizing a variation in pressure which is a function of said boosting compression to determine the relative amounts of energy to be applied in efi'ecting said boosting compression with respect to said initial compression whereby tendencies to variation in the efiect desired'are counteracted.

6. The method of delivering compressed cooled air to a rectifying column, which comprises preliminarily compressing and cooling input air, further compressing at least a portion of said input air, indirectly cooling said further compressed air, expanding at least a portion of said input air with internal work through a throttle valve into the column, expanding at least a portion of said input air with external work through an expansion engine intothe column, utilizing said external work for said further compressingqmd automatically maintaining the volume and refrigerating effect of input air to the column substantially constant despite fluctuation in the ratio of input throttled air to total input, air.

7. The method of producing refrigeration in a system having compression devices and engine expansion and throttling expansion devices in parallel for processing air supplied to a rectifying column, which comprises compressing air drawn from the atmosphere to a desired high pressure by means of energy obtained from an external source, boosting the pressure of said compressed air by means of energy obtained from the engine expansion of a portion of said compressed air, eifecting throttling expansion of the remaining portion of said boosted compressed air, and proportioning the expansion ratio by which said engine expanded air is expanded to the compression ratio by which the boosting of said compressed air is efiected to have a value such that any tendency for the total air and refrigeration input to the column to vary, on account of some interferences with the free flow of throttled air to the column, is compensated for and a self-balancing system is obtained.

8. The method of producing refrigeration in a system having compression and expansion devices arranged to process air supplied to a rectifying column, which comprises initially compressing air to a desired high pressure, thereafter boosting all of said compressed air to a still higher pressure, dividing said boosted compressed air into a plurality of portions, causing one of said portions to expand and do internal work, causing another of said portions to expand and do external work, utilizing said external work to effect said boosting compression, and proportioning the expansion ratio of doing external work to the ratio of the boosting compression so as to have a value such that any tendency for the total air and refrigeration input-to the column to vary, on account of interference with internal work, is compensated for over the range of normal operation.

' 9. The method of producing refrigeration in a system having compression devices arranged in series and expansion devices arranged in parallel to process air supplied to a rectifying column,

which. comprises compressing the air in said se-- ries of compression devices to successively higher pressures, providing independently the energy for ation input to the column to change, dueto changes in the expansion accomplished by said internal work expansion devices over the normal range of operation is compensated for, and manually adjusting the external work expansion devices to accommodate changes which are beyond the range of normal operation.

10. The method of producing refrigeration in a system having compression devices and engine expansion and throttling expansion devices in parallel for; processing air, which comprises compressing the air to a desired high pressure by -means of energy obtained from an external source, boosting the pressure of all of said compressed air by means of energy obtained from expansion of said compressed air, initially cooling said system by engine-expanding a greater than Y stantially normal proportion of said boosted compressed air, and when cooled to a desired low temperature simultaneously expanding in nomal proportion different portions of said boosted compressed air by engine expansion and throttling expansion respectively.

11. The method of producing refrigeration in a system having compression devices and engine expansion and throttling expansion devices in parallel for processing air, which comprises compressing the air to a desired high pressure by means of energy obtained from an external source,

boosting the pressure of all of said compressed air by means of energy obtained from expansion of said compressed air, initially cooling said system by engine expanding a greater than normal proportion of said boosted compressed air, and when said system is sufilciently cooled, switching to normal proportions the respective portions of said boosted compressed air to be expanded by throttling expansion and engine expansion in parallel.

12. In a system for producing refrigeration by processing atmospheric air, the combination comprising means for compressing intake air at a substantially constant rate, a booster compressor arranged for operation at a variable speed for further compressing the compressed air, a throttling valve for expanding a portion of said further compressed air, an expansion engine for expanding another portion of said further compressedair in parallel to that expanded in said throttling valve, said expansion engine having a ratio of expansion substantially greater than the ratio of compression in said booster compressor, and a mechanical coupling connecting said expansion engine to drive said booster compressor whereby said booster compressor and said expansion engine are able to absorb any tendencies to variation in the power requirements of said booster compressor when the flow of air through said throttling valve is interfered with.

13. In a system for producing refrigeration by processing atmospheric air, the combination comprising main compressing means for compressing air drawn from the atmosphere, means for driving said main compressor,-an additional compressor connected in series with said main compressor for boosting the pressure of all of the air compressed in said main compressor to a higher pressure, a throttling expansion device and an engine expansion device disposed in parallel, each arranged to receive a portion of the air compressed to said higher pressure and supplying the same to a common place where said refrigerating effect is produced, means for coupling the engine expansion'device as the sole driving means to drive said boosting compressingmeans, and means responsive to a pressure variation which is a function of said boosting compressor for determining the energy to be supplied respectively to said first named and to said second named driving means whereby to maintain subconstant a desired effect at the place of use.

14. In a system for producing refrigeration, the combination with an apparatus for processing atmospheric air, having a main compressing means for initially compressing the air to a desired high pressure, of additional compressing means for boosting air compressed-in said main engine means for expanding said air compressed in said system by doing external work and decreasing the pressure to a value less than said desired high pressure, means for conveying the air subsequent to compression through said heat exchanger to a place of use, means for applying the work or said engine expanding means to drive said additional compressing means, means for regulating the speed of said engine expanding means, and power means for independently supplying energy to drive said main compressing means.

15. In a system for producing refrigeration, the combination with an apparatus for processing atmospheric air having a main compressing means tor initially compressing the air to a desired high pressure, of boosting compressing means for raising the compressed air to a higher pressure,

throttling expansion means, engine expansion means, means for dividing and conveying the air at said higher pressure from said boosting compressing means to said throttling expansion means and to said engine expansion means respectively into portions in accordance with a predetermined ratio, means vifor mechanically coupling said boosting compressing means to said engine expansion means for utilizing the work done by expansion, said engine expansionmeans having a relatively large expansion ratio and said -boosting compressing-means a relatively small compression ratio, whereby said coupled boosting compressing means and the engine expansion means are inherently capable of absorbing tendencies for speed variation due to variation of pressure on the intake side or saidboosting compressing means. 7

16. In a system for producing refrigeration, the combination with an apparatus for processing atmospheric air having a main compressing means for initially compressing the air to a desired high pressure, of boosting compressing means for raising the compressed air to ahigher pressure, a heat exchanger for receiving the air from said boosting compressing means, engine expansion means for expanding a portion of said boosted compressed air, throttling expansion means for expanding another portion of said boosted compressed air, means for dividing the air received from said heat exchanger into two portions in accordanceiwith a predetermined ratio, engine expansion means for expanding one or said portions, throttling expansion means for expanding the otherot said portions, means tor mechanically coupling said engine expansion means to drive said boosting compressing means, said coupled boosting compressing means and engine expansion means having their respective displacement ratios relatively proportioned so as to provide a system capable oi compensating for any tendency to variation v due to changes in the amount of air being processedby, throttling expansion over the normal operating range, means for regulating the speed of said engine expansion means beyond the normal range ot'variation, and

power means for independently supplying energy' to drive said main compressing means.

17. In a system for producing refrigeration by processing air, the combination comprising a main compressing means for compressing air at a substantially constant rate, additional compressing means for boosting the pressure operating at a variable rate, means for effecting throttling expansion or a portion of the air, the pressure of which has been boosted, means for eiIecting engine expansion of another portion or said boosted compressed air arranged to operate in parallel with said throttling expansion means. said engine expansion means normally effecting expansion by 'a greater ratio than the ratio oi compression in said additional compressing means, and a coupling arranged to transmit driving energy from saidengine expansion means to said additional compressing means whereby the coupled means absorbs any tendency to variation in the power requirements of said additional compressing means when additional resistance develops to the flow of air through said throttling-expansion means. I

. HARRY D. EDWARDS.

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