FR2537663A1 - Rotary piston compressor and pressure-reducing valve - Google Patents

Abstract

Rotary piston compressor comprising two pistons 2, 4 mounted on parallel shafts and forced to turn at equal speeds in opposite directions, applied against one another and against a housing to form a tight seal. A fixed hollow shaft extends axially inside the first piston 2 and has an axial slot 13 which passes through its side wall. The pistons 2, 4, the second aperture 24 and the slot 13 are arranged in such a way that the radially inner edge of the front face 17 of the first piston 2 and the radially outer edge of the rear face of the other piston 4 meet just at the moment when the axial slot 13 and the second aperture 24 begin to coincide. This compressor virtually eliminates all the dead spaces by reason of its geometry and it has an improved efficiency.

Description

 The present invention relates to machines with rotary pistons with positive displacement of the compressor or expansion valve type and it relates more particularly to improvements made to the efficiency of these machines as well as to the use of machines of this type in refrigeration circuits with cycle. air or steam.

 The devices which are considered to be the most advanced are described in US Pat. Nos. 3,790,315, 3,799,712 in English Patent 1,321,485, and in US Patents 3,472,445, 3,535,060 and 4,224,016.

All these compressors deliver compressed air through orifices made in the parallel side walls of a compression chamber having the shape of the figure eight, orifices which are exposed by the rotation of the main rotary piston. The air to be compressed moves parallel to the side wall until it is expelled through these orifices.
These, which should normally be relatively small to give a reasonable compression ratio and must be sharp edges. This inevitably implies that the air is subjected to a sudden change of direction at 90g when passing through the sharp orifices, usually small, which determines turbulence and pumping losses which increase markedly with the speed of rotation.

 In addition to the above problems, these compressors must laterally deliver the last part of the compressed air trapped between the rotary pistons at an extremely high speed, at least if the rotary pistons must have a reasonable width and they must rotate at the high speeds that are desirable to ensure efficient operation. The result is that there tends to occur in the chamber, at the end of the delivery, a rapid increase in pressure and generating losses, which was mitigated by practicing notches in the main rotor, at the base of the teeth. .

These notches which effectively reduce these losses by rolling unfortunately have the effect of introducing into the geometry of the compressor dead spaces in which the compressed working fluid is transferred to the low side near
sion, in which he relaxed without doing useful work
and dissipates the energy of compression in the form of cha
their. Another solution was to give a weak thick
the rotors forming the pistons of the compressor, which alleviates these rolling problems but at the cost of a proportional reduction in the fluid displacement capacity of the
compressor. For example, the capacity of the compressors mentioned above is of the order of a third of that of a machine of the same size constructed in accordance with the present invention.

An additional consequence of this same rolling effect is that this type of compressor tends to be
very sensitive to the presence of liquids in the vein of fluid, liquids which produce a destructive liquid shock at the end of the delivery, unless a certain part of the active piston is hollowed out by the formation of notches or by chamfering. This again raised the problem of liquid shock but, here again, at the cost of losses in dead spaces or per-
your by leaks.

An alternative embodiment of the above compressor consists in using a main rotary piston mounted on a
hollow tree. Compressed fluid is delivered through holes
or slots in the wall of the main rotary piston, at the base of the active tooth or active teeth. This configuration effectively solves the problems posed by the forced lateral displacement of the fluid at the end of the delivery, but
at the cost of dead spaces contained in the orifices of the wall of the main rotary piston, where pockets of compressed fluid
are transported to the low pressure side to the compressor, causing losses. A compressor of this kind, or which is described in US Pat. No. 3,545,895, would also be affected by losses by rolling in the holes or slots made in the shaft of the rotor, which are necessarily restricted in
cross-sectional area by the nature of the compressor geometry as well as by structural considerations.

 A solution to the problems posed by the inherent limitations of the size of the slots in the wall of the main rotor shaft is implicitly contained in the proposal consisting in providing a projection on the distributor rotor which penetrates into the slot in the wall. of the hollow main rotor and effectively blocks this slot.

However, in this document (US Patent 3,945,777), there is no description or indication which suggests to the mans the application of this idea to a compressor or expander having no dead space and having a continuous flow fluid at all points. These features are essential elements of the present invention.

In the present invention, the projections formed on the obturator rotor piston penetrate into the slots of the pa king of the rotary piston and pass through these slots, which gives a greater seal area between the protrusions of the obturator rotor and the fixed shutter plug. This characteristic does not exist in the prior art
The aims of the present invention have several aspects, the first of which consists in producing a compressor or expander with rotary pistons with parallel axes which, (1) does not contain oil in its active area; (2) has no dead space; (3) does not force the active fluid to undergo a sudden change of direction; (4) does not present any point which hinders the regular flow of the active fluid, (5) is capable of accepting relatively large proportions of liquid in mixture with the compressible fluid without undergoing liquid shock, even with high rotational speeds; (6) has an improved sealing geometry.

To obtain the maximum performance in thermal cycle applications of the machines in question, a second aspect of the invention consists in incorporating into the machine itself a separator for the elimination of the liquid entrained in the active fluid. When a mixture of compressed fluid and liquid is delivered into the valve plug located inside the hollow shaft of the. main piston, this mixture is entered in vortex movement by the internal shape of the plug The compressed fluid in vortex movement, and while it is still inside the liner, is then transferred through a groove smooth profile which, by a well-known cyclone effect, increases the rotational speed of the fluid and separates the liquid droplets from the gas in the form of a vapor flow. The compressed fluid in rapid vortex movement is then transferred through an appropriately shaped chamber to recover most of the energy of the vortex movement. The Applicant has not been aware of previous attempts to incorporate such a liquid separator in a rotary piston compressor
A third aspect of the invention, which relates to the adjustment of the flow rate in a rotary piston machine, relates to one or more discs or rotary rings, disc segments or rotary rings, housed in the end walls of a compressor. US patents 3,723,031, 3,468,294 and 3,108,740 describe such discs which all regulate the flow in the piston compressors by letting part of the fluid trapped in the O - compression chamber escape 2 through a hole or a slot in the disc or the discharge ring to reach a duct situated behind the disc and thereby return to the inlet of the compressor. The invention makes it possible to dispense with this return duct by using a ring or a thick discharge disc, which has a groove in its surface opposite the compression chamber The fluid escapes from the front of the tooth of the main rotor passing through the groove and it returns to the low pressure chamber passing behind era the tooth. The quantity of fluid thus discharged is adjusted by turning the ring or the discharge disc by means of a suitable device such as a pinion secured to a lever or an adjustment wheel.

 The aspects of the invention which have been described above combine with each other to improve the total efficiency and the total practical usability of the rotary piston machine and this is achieved by combining two such machines in such a way to make an improved refrigeration apparatus. A fourth aspect of the present invention therefore resides in the mounting of a compressor and of a pressure reducing valve of this type on the same pair of parallel shafts, by supplementing them with a heat exchanger, by appropriate piping and setting, to form an open cycle air refrigeration unit or a closed cycle gas or steam refrigeration unit.

 As in any Joule cycle heat engine, the overall efficiency of such a refrigeration unit is extremely sensitive to the individual efficiency of its compressor and its expansion valve. It is only when these efficiencies reach a value of l '' 95% order that the open cycle air refrigerator can begin to compete in energy efficiency with vapor compression devices and this only for certain applications. In addition, it is only when the air cycle machines are very simple and inexpensive by their very nature and that there are no mechanical or fluid dynamic dynamics restrictions on the flow of the fluid at high rotational speeds. , that these machines can compete with vapor compression machines from the point of view of capital investment. No positive displacement machine already known in the art fully satisfies these criteria The closest solution found in the already existing technique is represented by the machines and groups with compressor-regulator with oscillating vanes described in the patents US 3 686 893 and 4 088 426, which function on a principle different from that of the present invention.

 The high yields of the machines according to the invention and their ability to work with liquid / vapor mixtures makes them particularly well suited for use in closed cycle vapor compression refrigerators, an application which constitutes a fifth aspect of the present invention. It is well known to increase the. efficiency and capacity of a conventional vapor compression refrigeration cycle - which includes a compressor, a condenser, a throttle tensioner, an evaporator and reyling and bypass devices - by replacing the throttle expansion device, isenthalpic, by means capable of recovering the work of the trigger. The means of this kind can be composed on the basis of heat transmission devices (US Pat. No. 4,304,099) or quasiisentropic mechanical expansion devices I1 has already been proposed continuous flow as well as positive displacement devices. A positive displacement semiisentropic expansion device which rotates in conjunction with the compressor has two advantages: it precisely regulates the flow rate of the liquid; at the same time it increases the amount of refrigeration and reduces the amount of labor consumed. However, devices of this kind are rarely used in practice because the modest gains they bring are more than offset by the increase in cost and by the disadvantage of having a separate regulator. In US Pat. No. 4,235,079, the expansion devices described therein involve either the use of a separate regulator, comprising a separate casing and several movable elements, or the use of vane-bone vane pumps, with compression. of steam on one side and the expansion of a liquid on the other side with the same mass flow rate for steam as for liquid This inevitably implies that the compressor must be undersized or that the regulator is oversized, this due to the difference in density between the liquid phase and the vapor phase, a difference which amounts to several orders of magnitude.

 The expansion device proposed in this patent simply comprises a second pair of pistons constituted by a thin ring or by a thin disc, each bolted to the end of a respective compressor piston and which rotates in a chamber formed for this purpose at inside a spacer. Additional holes are formed in the plug and in the distributor plate to allow the liquid to penetrate and extract the expanded liquid / vapor mixture.

A simple mechanism of this kind, which is only more costly than that of an expansion valve, represents a sandstone wall which is important in the art, both with regard to increasing the efficiency of the refrigeration and with regard to its contribution to the control device which will be described below
The performance of a vapor compression refrigeration cycle can be changed by affecting the refrigeration temperature and the refrigeration capacity.

The present invention provides the possibility of acting on the cycle by injecting liquid, the combination of a positive displacement liquid holder and a device serving to inject metered quantities of liquid into the vapor. which enters the compressor forming a very sensitive temperature control device A small increase in the proportion of liquid injected leads to a significant reduction in the refrigeration temperature.

 The temperature control devices of the prior art which use adjustable liquid flow rates introduced in mixture with the steam which enters the compressor or which are injected directly into the compressor, are mainly devices intended to cool and regulate or regulate the temperature of the oil injected into the rotary screw compressors, for example in re-issued US patent 38,869, A "liquid back" device intended to mix a liquid in a quantity metered with steam which penetrates into the compressor has already been described in US Pat. No. 4,261,180, but this device mainly uses the addition of liquid as an artifact to improve the sealing of the compressor, to cool the compressor components and to cool the vapor compressed by an evaporation phenomenon. The invention does not suggest the use of a proportioned proportion of liquid as the main means of regulating or regulating the temperature of the refrigeration cycle. Likewise, it does not specify the use of a positive displacement regulator or of another form of regulator in which the flow rate varies very little with the differences in pressure.

 It has already been proposed to mix a quantity of liquid determined by thermostatic route with the steam entering the compressor to limit the overheating of the steam delivered by the compressor. This is in US Pat. No. 4,049,410. This patent suggests regulating the temperature by a thermostatic valve.

 Various refrigeration devices are already known in which proportioned proportions of liquids are mixed with the gas to be compressed, for example the device described in US Pat. No. 4,258,553, but these devices are part of a device intended for regulating production overall thermal and not that of the refrigeration temperature.

These devices have not been proposed in combination with positive displacement regulators and
Finally, according to another aspect, the invention proposes a refrigeration unit in which the compressed and condensed liquid is expanded in a positive displacement expansion valve which operates at the same speed as the compressor and in which the refrigeration temperature is adjusted by modifying the proportion of liquid mixed at the inlet of the compressor and / or injected into the compressor.

Other characteristics and advantages of the invention will emerge during the description which follows. In the accompanying drawings, given solely by way of example,
- Fig. 1 is a sectional view of a rotary piston compressor, the section being taken in the plane of the axes of the shafts of this compressor;
- Fig. 2 is a sectional view of the compressor of the
Fig. 1, taken in plane II-II of Fige 1
- Figs. 3 and 4 are respectively axial and transverse sections of a variant of the valve or shutter means to the compressor of FIGS. 1 and 2, FIG. 4 being a section taken along the line IV-IV of FIG. 3 and FIG. 3 a section along line III-III of FIG. 4
- Fig. 5 is a partial section of a compressor of the type shown in FIGS. 1 and 2, which shows an adjustment device intended to regulate the flow rate of the compressor
- Fig. 6 is a sectional view taken along the plane
VI-VI of FIG. 5,
- Fig. 7 is a sectional view of the valve plug, taken along the line Vil-Vil of FIG. 5
- Fig. 8 is an axial section of a combined compressor-regulator machine which uses the compressor of the
Fig. 1 and 2
- Fig. 9 is a section along the line IX-IX of FIG. 8,
Fig. 10 is a section along line XX of FIG. 8
- la.Fig. 11 is a schematic view similar to the
Fig. 8 and which shows a variant of the intermediate valve or shutter means,
Figs. 12 and 13 are detail views in section of the liner valve or shutter means of FIG. 11, taken respectively along lines XII-XII and XIII-XIII ;;
- Fig. 14 shows in axial section the compressor-expansion unit in its application to a steam refrigeration cycle
- Figs. 15, 16 and 17 show cross sections of the machine, taken respectively along the lines
XV-XV, XVI-XVI and XVII-XVII.

 Fig. 1 and FIG. 2 show two views of the same basic rotary piston machine, which in this case works as a compressor at a relatively constant compression ratio. The moving parts of the compressor are the main shaft 1 which receives or transmits the torque and on which the main rotor (2) is mounted, and a secondary shaft (3) on which the shutter rotor (4) is mounted. Straight toothed wheels (5) are mounted on the two shafts and force the latter to rotate at identical speeds and in opposite directions. The two rotors rotate by applying a tight seal against each other, and against the casing 6 and a shutter jacket or plug 7 which is located inside the hollow main rotor 2.A device intended for injecting a liquid 8 in the fluid to be compressed and to mix it with this fluid can be attached to the inlet of the compressor. This injection of liquid improves the sealing of the compressor and further improves the operating efficiency by eliminating part or almost all of the heat of compression of the working fluid during compression.

 The active fluid is sucked into the compressor through the retracted orifice 9, in the direction indicated by the arrows 10. In the position shown in FIG. 2, the fluid trapped in the compression chamber 11 has just started to compress. When the two pistons have rotated approximately 1300 in the direction indicated by the arrows 12, the transfer lumen 13 formed in the wall of the plug opens and the compressed fluid, with the liquid which may accompany it, is transferred to the high pressure line 14 and expels from the compressor. (The compression compression ratio of the compressor shown in Figs i and 2 is about 6: 1).

The main gold rot profile is defined by two teeth 15, the end faces 16 of which rotate by applying a seal in the casing 6. The front faces 17 of these teeth are scrolls exactly defined by the evolution of the edges 18 of the protruding teeth 19 of the distributor rotor. The rear faces 20 of the teeth of the main rotor have a profile designed to facilitate manufacture and which gives the teeth sufficient thickness to ensure adequate sealing. These teeth are followed by cylindrical segments 21 which rotate with a tight seal against the cylindrical segments 22 of the shutter rotor. If the segments 21 of the main rotor and segments 22 of the shutter rotor have equal diameters, as in the case shown in Fig. 2, they rotate by establishing a rolling contact between them which improves the sealing. Following the cylindrical segments 21 with the shutter rotor, there are double curves 23 having an exactly defined profile which terminate in openings 24 formed in the wall of the hollow main rotor e The double curves 23 of the main rotor turn with a tight seal against the double curves 25, of an exactly defined profile, formed on the front teeth 19 of the shutter rotor 4. Cavities 26 formed at the base of the teeth 19 of the shutter rotor 4 form clearances which give passage to the teeth 15 of the rotor main 2.The teeth 19 of the shutter rotor 4 penetrate only slightly into the openings 24 of the main rotor (up to about 2% of the radius of the tips 18 of the teeth 19), thereby enlarging the sealing surface between the peripheries 27 of the teeth 19 of the shutter rotor and a plug 7 located inside the hollow shaft of the main rotor. The thickness of the teeth 19 of the shutter rotor is determined by the compression ratio, which determines the width of the lights 24 of the main rotor0
The main rotor 2 and the shutter rotor 4 have parallel sides which rotate in contact with the casing 6 to form tight seals. The width of the rotors is limited by structural and manufacturing considerations rather than by considerations of handling of the flui de.

 Fig. 3 and FIG. 4 represent a variant of the plug valve which differs from the valve 7 shown in use in the compressor of Fig0 1 and 2o The function of this valve consists in separating the droplets of liquid from the compressed gas. This bushel passes the incoming compressed fluid through a profiled groove 30 to impart a swirling motion to the mixture of compressed gas and liquid droplets in the interior volume 31, of cylindrical shape, of the bushel. This vortex movement causes some separation of the liquid droplets from the gas.

The swirling movement is considerably amplified when the swirling compressed gas is passed through a narrow groove 32, which separates most of the rest of the liquid droplets from the gauze. The liquid droplets are collected in a channel 33 and evacuated by a tube 34.

Most of the energy of the gas-printed vortex movement can be recovered in a vortex or vortex chamber 35.

 A similar effect can be obtained by simply extending the parallel-walled tube 31 of the plug to a sufficient extent so that the small droplets have time to migrate to the walls of the tube and from there reach the channel 33.

 Figs. 5, 6 and 7 show a discharge device incorporated in the same schematic compressor shown in FIGS. 1 and and 20. An end wall of the casing 6 is replaced by a grooved disc 40 and by a device which can rotate it up to at 180. In this embodiment, the device is a shaft-pinion assembly 41 the teeth of which mesh with teeth 42 formed in the periphery of the groove disc 40 One face of the disc 40 is kept applied with a tight seal against one face of the main piston 2 and of the obturator piston 4. In this face of the disc, a groove 43 of suitable shape is made to allow the active or working fluid, which would be trapped and compressed in the compression chamber 11 by the advancing tooth 16 of the main piston, of s 'escape by bypassing the tooth, passing through the groove 43 to return to the part of the casing 10 of the compressor in which this fluid is not subjected to compression. The proportion of the working fluid charge which is thus released depends on the angular position of the grooved disc.

 As seen in Figure 6, the profile of the groove 43 is defined by two arcs of circles 45 and 44, by a curve 46 which approximately follows the curve 17 of the front of the tooth 15 of the rotor forming the piston principal, and by a curve 47 whose shape does not have to be exactly defined.

The angle subtended by the groove on the center of the main shaft is normally less than 180. The plugs used in this discharge compressor can be adjustable plugs or hybrid devices composed of a plug 48 and a valve 49, as shown in section in FIG. 7. Such a hybrid, which works like a manual bushel under full load, eliminates most of the reflux of compressed fluid in the compression chamber under reduced load, reflux which would normally occur in such a compressor which would only be equipped with a simple bushel.

 Figs. 8, 9 and 10 show three sections of an open cycle air refrigeration machine which may include water injection means and which comprises a compressor, a regulator equipped with an adjustable intake valve, an exchanger heat and a water separator.

 The compressor-expansion machine consists of a pair of rotary piston machines of the type shown in FIGS. 1 and 2, which are mounted side by side on the same pair of rotating shafts, which are the shaft 51 of the rotor. main and the shaft 52 of the shutter rotor The rotations of these two shafts are precisely coordinated by two toothed wheels 53 of the same diameter. Inside the pair of hollow main rotors 54, 55, is placed a double bushel 56, 57 provided with a partition 58 which separates the heated compressed air containing water, which leaves the compressor, from the cooled air, free of water which enters the regulator.

The quantity of compressed air admitted to the tensioner can be varied by moving the part of the plug 59 of the tensioner, movement which is carried out by means of a dea7ltee wheel and a pinion and lever assembly 60.

 The air supplied to the refrigerator is atmospheric air 61 and it enters the inlet 62 of the compressor, in which it is mixed with water droplets 63. The mixture of air and water is drawn into the chamber. compression 64, in which it is compressed and heated by this means. The extent to which this mixture is heated depends on the compression ratio and the proportion of water mixed with air. Another path that can be adopted to inject the water into the compressor is made up of holes made in the periphery of the casing 65 of the compressor. The compressed mixture of air and water droplets is transferred to the interior volume of the bushel 56 from the compressor then into a duct 67 and it is evacuated from the bushel in a duct 68 which sends it to a heat exchanger 69 and to a water separator 70. If a sufficient quantity of calf has been injected , the heat exchanger is superfluous. The compressed air freed from water and which has approximately the ambient temperature is returned by a conduit 71 to the conduit 72 which introduces it into the adjustable plug 57 of the pressure reducer. The compressed air expands in the expansion chamber 73, where it provides work for the shafts 52, 51 and where it is cooled. The cooled air 74 is sent to the refrigerated volume through the outlet 75. The compression pressure and, consequently, the refrigeration temperature of the cycle are determined by the setting 60 of the adjustable bushel 59 of the regulator. When the volume d is reduced compressed air admitted to the expansion valve, the cycle pressure increases and the refrigeration temperature drops. A variant of a plug which can be used for this machine and which comprises a water separator is shown in FIGS. 11, 12 and 13. This water separator works in accordance with the principles illustrated in Figs. 3 and 4 and which have been described above. The mixture of compressed air and water droplets penetrates into the bushel 76 of the compressor in a tangential direction, which gives it a vortex movement in the direction represented by the arrow 77. This swirling movement forces the droplets of water to migrate towards the internal wall of the plug and to gather in the channel 78 of evacuation of the batten. The speed of the vortex movement is considerably increased, and the remaining water droplets are then separated, when the compressed air enters, through the groove 79, in the adjustable plug 80 in which the speed of the vortex movement is reduced, and a part of the energy of this movement is recovered.

 The compressed air is then ejected into the expansion chamber through the adjustable lumen 81 of the plug. The water which is under pressure is discharged through the tube 82. This pressurized water can be used to lubricate the bearings 83, 84 (Fig.8).

 Figs. 14, 15, 16 and 17-illustrate the incorporation of the compressor, the control disc and the expansion valve in a vapor compressor refrigeration circuit. The refrigeration unit includes a compressor 90 and a fluid injection device 91, a discharge disk 92, a pressure reducer 93, a condenser 94, a liquid separator 95D An evaporator 96, as well as the necessary adjustment Q not shown). This particular machine illustrates a combination of a compressor, a control disc and an expansion valve to show how simple these types of adjusting discs and expansion devices can be added to compressors. Actual refrigeration machines can include compressor-expanders or discharge compressors or single compressors. The injection of fluid necessary to improve the tightness of the compressor, cool the compressor and improve the overall efficiency of the cycle, as well as for the adjustment function which will be described in detail below.

 The machine shown in Figs. 14, 15, 16 and 17 comprises a main shaft 97 which is driven by a motor, electric or other. The hollow main rotor 98 of the compressor is fixed to the main shaft, which is of the same type as that shown in FIG. 2. At the end of the main rotor is fixed a sleeve 99 on which is mounted the main rotor 100 of the regulator, Inside the hollow main rotor are arranged two fixed plugs mounted on the same sleeve, the plug 101 of the compressor and the valve 102 of the regulator.

The compressor plug may be of the type shown in the
Fig. 7. At one end of the rotor in the part 108d of the casing, the compressor discharge disk 92 is placed, the actuation mechanism of which is not shown. The shaft 103 of the obturator rotor rotates on a fixed axis. 104 at the same speed as the main rotor and in the opposite direction, under the effect of the gears 105. The obturator rotor 106 of the compressor and the obturator rotor 107 of the regulator are mounted on this shaft 103. It should be noted that '' there are no protruding teeth on the obturator rotor 107 of the regulator, this in order to confine the entire flow of expanded vapor / liquid mixture on the side of the casing which comprises the main rotor and to facilitate the flow of the liquid To improve the penetration of the compressed liquid into the expander, a volume (not shown) may be provided near the inlet of the expander, this volume containing a vapor or other compressible substance.

The housing 108 which contains the rot ors is made up of six parts which correspond to the different parts of the machine, that is to say the part 108a, which contains the motor and its bearings, the part 108b which contains the gears, the part 108c which contains the compressor rotors, the discharge disc 108d, the regulator rotors 108e and the part 108 f which forms the end cover and the mounting of the hunchback bucket
When the refrigeration unit is in operation, the compressed steam is heated, mixed with a certain quantity of liquid, leaves the duct 109 formed inside the valve plug 101 of the compressor (the machine must be in an orientation of nature to prevent the liquid from accumulating in the plug) and it enters the duct 110 which sends it to the condenser 94, from where the condensed liquid returns via a duct 111 to the inlet valve 102 of the regulator.

In the regulator, the liquid is cooled and a certain part of this liquid evaporates to give rise to a mixture of liquid and vapor at low pressure. The mixture is sent via the tube 112 to the liquid separator 95 (liquid separator which can be incorporated in the casing 108e in the regulator). At the outlet of the separator, a liquid part is sent through the tube 113 to the mixer 91 and the rest of the liquid-vapor mixture is sent through the tube 114 to the evaporator 96.

From the evaporator, the steam is sent through the tube 115 to the mixer 91, in which it is mixed with a proportion proportioned of liquid The proportion of liquid mixed with the vapor is used to regulate the refrigeration temperature of the cycle. For a given value of the displacement of the compressor, an increase in the proportion of liquid introduced into the compressor considerably reduces the pressure of the evaporator and the refrigeration temperature. The fact that this type of compressor can admit large proportions of liquid into the working fluid without malfunction allows it to process more than half of the working fluid in liquid form, and thereby ensure a considerable discharge compressor e

Claims (11)

R E V E N D I C A T I O N S  1 - Rotary piston compressor comprising two pistons (2, 4) mounted on parallel shafts and forced to rotate at equal speeds, one in opposite direction to the other, applying a tight seal against each other other and against a casing, a first orifice being provided in the casing for the entry of a fluid, a second orifice being provided in one of the pistons to allow the fluid to exit in a radial direction, the first piston (2 ) also having a radially outwardly extending tooth formed over the length of this piston, the tooth having a front face and a rear face, and the second orifice being formed at the radially inner end of the front face of the tooth, while the other rotary piston (4) carries a tooth which extends radially outwards and has a front face and a quarry face, and a blind cavity formed at the base of the front face to receive the tooth of the first rotary piston, a fixed hollow shaft extending axi alement inside the first piston and having an axial slot (13) which passes through its side wall, characterized in that the pistons (2, 4), the second orifice (24) and the slot (13) are arranged in such a way so that the radially inner edge of the front face (17) of the first piston (2) and the radially outer edge of the rear face of the other piston (4) meet just when the axial slot (13) and the second orifice (24) begin to coincide.  2 - Rotary piston compressor according to claim 1, characterized in that the axial slot (13) is arranged to lead tangentially into the internal volume of the hollow shaft to impart a swirling movement to the working fluid.  3 - Rotary piston compressor according to claim 2, characterized in that a groove (32) is provided in the hollow shaft and a longitudinal channel (33) is formed in the internal surface of the wall of the shaft to collect the particles of liquid which have been separated from a gaseous or vapor working fluid.  4 - Rotary piston compressor according to claim 1, characterized in that at an axial end of said first piston, there is provided a rotary disc (40) mounted in the flowering of the housing, the disc being provided with a curved groove (43 ) having a length greater than the thickness of the tooth of said first piston.  5 - Compressor according to claim 4, characterized in that the disc (40) has gear teeth (42) formed on a part of its periphery and can be rotated selectively by means of a drive pinion.  6 - Compressor according to claim 1, characterized in that the second orifice is provided with an elastic valve (49).  7 - Air cycle refrigeration machine, characterized in that it comprises a rotary piston compressor according to claim 1 and a rotary piston expansion valve mounted on the same pair of parallel shafts (51, 52), l the compressor inlet being equipped with means (62) for mixing a liquid with the working fluid, the working fluid being sent to a heat exchanger and to a liquid separator, and the working fluid then being sent to the pressure reducer, passing through a hollow shaft (57) and an inlet port, the regulator being approximately the same size and configuration as the compressor but working in reverse and delivering through an outlet port (75) provided in the machine housing.  8 - Air cycle refrigeration machine according to claim 7, characterized in that liquid is mixed with the working fluid in sufficient quantities to extract almost all of the heat generated by compression and in that the mixture of working fluid and liquid is separated in a vortex separator mounted entirely in the hollow shaft on which one of the compressor rotors and one of the regulator rotors are mounted, the vortex separator comprising a first and a second approximately coaxial cylindrical plugs (76, 80) which are located respectively in the rotor of the compressor and the IO tor of the regulator and which are connected by a groove (79), the first chamber comprising a longitudinal channel collecting manifold water (78) which leads to a discharge conduit (82).  9 - Steam cycle refrigeration apparatus, comprising a compressor according to claim 1, and characterized in that it comprises a pressure reducer mounted on the same pair of parallel shafts as the compressor and which rotate in chambers distinct from that of the compressor inside the same casing, the compressed vapor being sent from the compressor to a condenser through a hollow shaft and the condensed working fluid returning to the regulator through the same hollow shaft, the regulator being of reduced dimensions compared to to those of the compressor and comprising a first rotor (100) which has a certain number of teeth which extend radially outwards and a second rotor (107) which has an equal number of corresponding cavities, the fluid condensed working material being admitted to the regulator through orifices formed at the base of the teeth of the first rotor, the expanded fluid being sent from the regulator to a liquid separator (95) and the vapor being sent th thence to an evaporator (96) and returning to the inlet of the compressor, part of the separated liquid being mixed with steam at the inlet (91) of the compressor or in the compression chamber.  10 - Steam cycle refrigeration machine according to claim 9, characterized in that the compressor has a variable compression ratio.  11 - Steam cycle refrigeration machine according to claim 9 or claim 10, characterized in that the quantity of liquid mixed with the steam is used to regulate the refrigeration temperature.