Method and a device for a conditioning for an aircraft cabin

Abstract

The invention relates to a method and a device for air conditioning for an aircraft cabin (30) comprising at least two distinct turbomachines (1, 2), at least one of which is motorised. When the pressure difference between the cabin and the atmosphere is greater than an upper pressure difference threshold, an economy mode is activated, in which the second turbine stage (23) is supplied exclusively by an air output obtained from the cabin (30). When the pressure difference is lower than a lower pressure difference threshold, a cold mode is activated, in which the compression stages (11, 21) of the turbomachines (1, 2) are connected in series. The drive speed of at least one motor (12, 22) is adjusted such as to adjust the refrigerating power supplied.

Description

[0001] The invention relates to a method and a device for air conditioning to control the temperature and pressure of the air in an aircraft cabin from an external source of air, and in particular the air collected under dynamic pressure by at least one air intake mouth provided in the outer wall of the aircraft.

[0002] Until now, the air conditioning systems used for the cabins of aeroplanes have been of the so-called pneumatic energy type, i.e. they are supplied by the pressurised air collected from the compression stages of the main drive turbojets of the aeroplane. This compressed air is cooled in at least one turbine stage. Very many different systems of this type have been proposed hitherto. For example, CA-687 482 describes a device comprising two assemblies, each of which comprises a turbine stage and a compression stage which are connected to one another by a shaft. In many known systems, a heat exchanger is interposed between a compression stage and the turbine stage in order to form a unit of the so-called boot-strap type.

[0003] However, these known pneumatic energy air conditioning systems are designed and optimised substantially in order to have the best performance in conditions of maximal cooling, such that they are relatively complex, heavy and energy-consuming in order to make it possible to obtain this maximal cooling, when necessary. However, this maximal cooling must be provided only for a small fraction of the duration of use, in general only when the aircraft is on the ground or at a low altitude.

[0004] From the point of view of the design of the aircraft drive turbojets, these known air conditioning systems affect the functioning and overall performance of the turbojets, and are to the detriment of their fuel consumption and dimensions. For most operating ranges of the aircraft, the air collected at one point which makes it possible to obtain the maximum cooling gives rise to wastage of energy.

[0005] Furthermore the air conditioning systems themselves must be oversized, and have downgraded performance levels for most of their operating range.

[0006] The concept has already been proposed of air conditioning systems with non-pneumatic energy, i.e. of which the air compression means are driven by drive means with non-pneumatic energy, and in particular electrical, hydraulic or internal combustion energy. However, these systems face the same problems as that previously described, i.e. the drive means must be designed and optimised in order to be able to provide the maximum cooling, and their performance and output is downgraded in the most common operating range of the aircraft. Moreover, the addition of specific drive means in relation to the power which the latter must provide in maximum operating conditions represents a substantial weight, such that hitherto, air conditioning systems with non-pneumatic energy have been considered non-competitive compared with those with pneumatic energy, and are not commonly used in practice.

[0007] Thus, FR-2 609 686 or U.S. Pat. No. 4,419,926 describe motor-driven air conditioning systems which make it possible to recuperate the energy obtained from the pressurisation of the cabin. FR-2 609 686 describes the use of a specific turbine which is dedicated to the recuperation of pressurisation energy from the cabin, and is interposed between the two air conditioning devices of an aircraft (two similar cooling units are provided). This specific turbine gives rise to an installation cost and is not incorporated in the pneumatic supply circuits of the cabin (the air output from this turbine does not supply the cabin). U.S. Pat. No. 2,479,991 describes a similar system with use of an internal combustion engine. Nevertheless these systems have a single point of optimised operation, and the pneumatic energy recuperation alone, which requires use of a specific turbocompressor assembly, is not realistic, taking into account the increases in weight and cost created by this specific turbocompressor assembly, and in any case the small increase in energy which does not compensate for the additional weight represented by the specific engines necessary for the functioning.

[0008] The object of the invention is in general to eliminate these disadvantages by providing a method and a device for air conditioning with non-pneumatic energy which are competitive compared with the known air conditioning systems with pneumatic energy.

[0009] More particularly, the object of the invention is to provide a method and a device for air conditioning which represent several functioning points which are optimised from the point of view of energy consumption and correspond to different conditions of functioning of the aircraft, and in particular functioning on the ground and functioning in flight.

[0010] For this purpose, the invention relates to a method for air conditioning to control the temperature and pressure of the air in an aircraft cabin from at least one source of air, implemented in an air conditioning device comprising:

[0011] at least one turbine stage for depressurisation/cooling comprising at least one air intake and at least one outlet for depressurised and cooled air, each turbine stage being connected to means for mechanical compression of air, such as to participate in the driving of these means;

[0012] drive means with non-pneumatic energy which are connected to the means for compression, such as to participate in the driving of these means;

[0013] a pneumatic supply circuit for the cabin with pipes and controlled valves, which is designed to be able to supply the means for compression from a compressed air output obtained from the source of air, to supply at least one turbine stage from an air output obtained from the means for compression, and to supply at least one air intake of the cabin with the air obtained from the air outlet of at least one turbine stage, and wherein the controlled valves of the pneumatic supply circuit of the cabin are controlled in order to configure the circuit according to an operating mode selected from amongst different operating modes, each of which corresponds to specific characteristics of output and/or temperature and/or pressure of the output of air supplied to the cabin, wherein the air conditioning device comprises:

[0014] at least two distinct turbomachines each comprising a compression stage and a turbine stage connected to the compression stage, at least one of the turbomachines being motorised and comprising a motor with non-pneumatic energy connected to the compression stage;

[0015] at least one parameter which is representative of the pressure difference between the air in the cabin and the external atmosphere is measured;

[0016] when the pressure difference measured (represented by the parameter(s) measured) is greater than an upper pressure difference threshold, an operating mode known as economy mode is activated, in which:

[0017] the turbine stage, known as the second turbine stage, of at least one of the turbomachines, known as the second turbomachine, is supplied exclusively via means, known as second supply means, by an air output obtained from an air outlet of the cabin, and the pressure of which is, with the exception of losses of load, that of the air pressure which exists in the cabin; and

[0018] the air outlet of the second turbine stage is isolated from the pneumatic supply circuit of the cabin, such that no output of air supplied in the cabin is obtained from the air outlet of the second turbine stage;

[0019] when the pressure difference measured is lower than a lower pressure difference threshold, an operating mode known as cold mode is activated, in which the compression stages of the turbomachines are connected in series from the source of air, and the drive speed of at least one turbomachine motor is adjusted such as to adjust the refrigerating power supplied by the air conditioning device, and wherein the second turbine stage is incorporated in the pneumatic supply circuit of the cabin.

[0020] Advantageously and according to the invention, in economy mode the second turbine stage is supplied by an air output obtained from the cabin directly via a pipe and a controlled valve, such as to enter the second turbine stage at least substantially at the pressure and temperature of the air which exists in the cabin, with the exception of circulation losses.

[0021] More particularly, advantageously and according to the invention, in cold mode the second turbine stage is supplied by an air output obtained from the air outlet of at least one other turbine stage, known as the first turbine stage, this air output reaching the intake of the second turbine stage at least substantially at the same pressure as at the outlet of the first turbine stage, with the exception of losses of load, and the cabin is supplied with at least a fraction of the output of air obtained from the air outlet of the second turbine stage.

[0022] Advantageously and according to the invention, since the second turbomachine is motorised, the first turbine stage belongs to a first motorised turbomachine comprising a motor distinct from the motor of the second turbomachine.

[0023] Advantageously and according to the invention the drive speed of a single turbomachine motor is adjusted.

[0024] Advantageously and according to the invention, in cold mode, the second turbine stage is not supplied by air obtained from the cabin. In fact, the air output from the second turbine stage is at a pressure which is reduced in comparison with the pressure which exists inside the cabin.

[0025] Advantageously and according to the invention, the lower pressure difference threshold and/or the upper pressure difference threshold are adjusted such as to adjust the refrigerating power supplied by the air conditioning device.

[0026] In fact, the pressure difference thresholds are represented by values of the representative parameter(s) of the pressure difference, which can be fixed and predefined, or on the other hand can be variable, determined and adjusted according to at least one other parameter, in particular according to the refrigerating power necessary in the cabin. These thresholds can be different in order to create a hysteresis, or on the other hand they can be equal.

[0027] Advantageously and according to the invention, in economy mode, at least one fraction of the air output from the second turbine stage is used as a cold source of at least one heat exchanger.

[0028] Advantageously and according to the invention, the method is characterised in that, at least in cold mode, the compressed air supplied by the compression stages is cooled by passing it through a cooling circuit of at least one heat exchanger, known as the intermediate exchanger, before it is supplied to the air intake of at least one turbine stage incorporated in the pneumatic supply circuit of the cabin, and in that, in economy mode, at least one fraction of the air output from the second turbine stage is used as a cold source for this intermediate exchanger.

[0029] As a variant or in combination, advantageously and according to the invention, at least in economy mode, the second turbine stage is connected to at least one rotary load, and in particular a rotary air compressor and/or a fan of the device.

[0030] Throughout the text the term “connected” designates the fact of making rotary units integral in rotation, directly or indirectly, mechanically, electrically, magnetically or by another means, such that one drives the other. Thus, the invention makes it possible to recuperate the mechanical drive energy of rotation of the second turbine stage in order to motorise and drive a rotary load.

[0031] The invention extends to a device which permits implementation of the method according to the invention. The invention thus also relates to an air conditioning device which is designed to control the temperature and pressure of the air in an aircraft cabin from at least one source of air comprising:

[0032] at least one turbine stage for depressurisation/cooling comprising at least one air intake and at least one outlet for depressurised and cooled air, each turbine stage being connected to mechanical means for compression of air, such as to participate in driving the latter;

[0033] drive means with non-pneumatic energy which are connected to the means for compression, such as to participate in driving the latter;

[0034] a pneumatic circuit to supply the cabin, with pipes and controlled valves, which is designed to be able to supply the means for compression from an air output obtained from the source of air, to supply at least one turbine stage from a compressed air output obtained from the means for compression, and to supply at least one air intake of the cabin with air obtained from the air outlet of at least one turbine stage;

[0035] automatic means to control the controlled valves of the pneumatic circuit, which means are designed to configure the pneumatic supply circuit of the cabin according to different operating modes, each corresponding to specific characteristics of output and/or temperature and/or pressure of the air output supplied to the cabin, wherein the device comprises:

[0036] at least two distinct turbomachines each comprising a compression stage and a turbine stage connected to the compression stage, at least one of the turbomachines being motorised and comprising a motor with non-pneumatic energy connected to the compression stage;

[0037] means for measurement of at least one parameter which is representative of the difference, known as the pressure difference, between the air pressure in the cabin and the external atmospheric pressure;

[0038] and wherein the means for automatic control and the pneumatic circuit for supply of the cabin are designed such as:

[0039] when the pressure difference measured is higher than an upper pressure threshold, to activate an operating mode, known as the economy mode, in which:

[0040] the turbine stage, known as the second turbine stage, of at least one of the turbomachines, known as the second turbomachine, is supplied exclusively via means, known as second supply means, by an air output obtained from an air outlet of the cabin, and the pressure of which is, with the exception of losses of load, that of the air pressure which exists in the cabin; and

[0041] the air outlet of the second turbine stage is isolated from the pneumatic supply circuit of the cabin, such that no output of air supplied in the cabin is obtained from the air outlet of the second turbine stage;

[0042] when the pressure difference measured is lower than a lower pressure difference threshold, an operating mode known as cold mode is activated, in which the compression stages of the turbomachines are connected in series from the source of air, and the drive speed of at least one turbomachine motor is adjusted such as to adjust the refrigerating power supplied by the air conditioning device, and wherein the second turbine stage is incorporated in the pneumatic supply circuit of the cabin.

[0043] Advantageously and according to the invention, the second supply means consist of a pipe which connects the air outlet of the cabin to an air intake of the second turbine stage and of a controlled valve which is interposed on this pipe, the air supplied to the second turbine stage by the second supply means in economy mode being, with the exception of circulation losses, at least substantially at the pressure and temperature of the air which exists in the cabin.

[0044] In a device according to the invention, the air output from the second turbine stage in economy mode does not participate in the supply of air to the cabin.

[0045] Advantageously in an air conditioning device according to the invention, in cold mode, the second turbine stage is supplied via means, known as first supply means, by an air output obtained from the air outlet of at least one other turbine stage, known as the first turbine stage, and the pneumatic circuit for supply to the cabin supplies the cabin with at least one fraction of the air output obtained from the air outlet of the second turbine stage.

[0046] Advantageously and according to the invention, the second turbomachine is motorised and the first turbine stage belongs to a first motorised turbomachine comprising a motor which is distinct from the motor of the second turbomachine.

[0047] Advantageously and according to the invention, the second turbomachine is motorised and the automatic means for control are designed to adjust the drive speed of a single turbomachine motor.

[0048] Advantageously and according to the invention, in cold mode, the second turbine stage is not supplied by the second supply means.

[0049] In addition, advantageously and according to the invention, the first supply means are designed to supply in cold mode to the intake of the second turbine stage an air output which is at least substantially, with the exception of losses of load, at the air pressure at the outlet of the first turbine stage.

[0050] Advantageously and according to the invention, the means for automatic control are designed to adjust the lower pressure difference threshold and/or the upper pressure difference threshold such as to adjust the refrigerating power supplied by the air conditioning device.

[0051] Advantageously and according to the invention, the device comprises means which are designed to supply in economy mode at least one fraction of the air output obtained from the air outlet of the second turbine stage, to a cold source circuit of at least one heat exchanger. After passing into this heat exchanger, the air output which is used as a cold source can be expelled to the atmosphere. In a particularly advantageous embodiment and according to the invention, the air conditioning device is characterised in that it comprises:

[0052] a heat exchanger, known as an intermediate heat exchanger, which is associated thermally with a cold source, this intermediate exchanger comprising a cooling circuit with an air intake which is connected to the air outlet of the mechanical means for compression of air and an outlet for cooled air;

[0053] means to supply the output of cooled air obtained from the cooled air outlet of the intermediate exchanger to the air intake of at least one turbine stage incorporated in the pneumatic supply circuit of the cabin; and

[0054] means which, in economy mode, are designed to supply at least one fraction of the output of air obtained from the air outlet of the second turbine stage, to a cold source circuit of the intermediate exchanger.

[0055] In addition, advantageously and according to the invention, the air conditioning device comprises thermal exchange means, and in particular a heat exchanger known as a cabin exchanger, comprising a cold source circuit which is designed to be interposed, at least in one operating mode, between the air outlet of the first turbine stage and the air intake of the second turbine stage, such as to have an output of refrigerating air passing through it, these thermal exchange means also being designed to create a flow of calories from the cabin air to the cold source circuit. Thus, accelerated cooling of the cabin temperature can be obtained, for example when the latter is particularly high, for example after the aircraft has been left in the sun on the ground.

[0056] Advantageously and according to the invention, the turbine stages are disposed such that the pressure of the air supplied by these turbine stages is lowest at the outlet of the second turbine stage, known as the second low-pressure turbine stage.

[0057] In an advantageous embodiment and according to the invention, the air conditioning device is characterised in that a compression stage of a motorised turbomachine, known as the low-pressure compression stage, comprises an air intake which is connected to the external source of air, and at least one other compression stage of another motorised turbomachine, known as the high-pressure compression stage, comprises an air intake which is designed to be able to be connected, in at least one operating mode, to an air outlet of the low-pressure compression stage, such that at least one fraction of the air output obtained from the air outlet of the low-pressure compression stage is supplied to the intake of the high-pressure compression stage, and in that the second turbine stage belongs to the motorised turbomachine comprising the low-pressure compression stage, and participates in driving of the latter in economy mode and in cold mode.

[0058] An air conditioning device according to the invention comprises the same number of compression stages as turbine stages, each turbine stage being connected to one of the compression stages such as to participate in driving the latter, and each compression stage being connected to one of the turbine stages. In one advantageous embodiment, the air conditioning device according to the invention comprises two turbomachines, i.e. two compression stages and two turbine stages.

[0059] In addition, advantageously, the air conditioning device according to the invention comprises means for condensation of the water interposed between the air outlet of the mechanical means for compression of air and the air intake of the first turbine stage. Advantageously and according to the invention, the means for condensation comprise a heat exchanger which is designed to have an air output passing through it, obtained from the air outlet of the second turbine stage.

[0060] The air output obtained from the air outlet of the second turbine stage can be used as a cold source for the means for condensation in cold mode or in economy mode.

[0061] In addition, even though it has been proposed theoretically to use a turbomachine which is motorised by a non-pneumatic energy source, and in particular with an electric motor, in order to be able to obtain directly the external air as a source of air rather than the air obtained from a compression stage of the drive turbojets of the aircraft, these proposals are not implemented in practice since they would give rise to the use of motors with high power levels leading to technological solutions which would be non-competitive compared with the conventional solutions which use the pneumatic energy of the main turbojets. However, the energy gains obtained by means of the invention now make it possible to envisage the use of drive means with non-pneumatic energy, which are specific to the air conditioning device, in order to drive the mechanical means for compression of air. In particular, by means of the invention, it becomes advantageous to use electrical energy for the motorisation of the means for compression.

[0062] Thus, advantageously and according to the invention, the drive means of the turbomachines consist of at least one electric motor. In one embodiment of the invention which is particularly advantageous, the device according to the invention is characterised in that it comprises two electric turbomachines each comprising an electric motor, a compression stage and a turbine stage, including a low-pressure turbomachine comprising the second turbine stage.

[0063] The invention also relates to the method implemented in an air conditioning device according to the invention. The invention also extends to a method and a device characterised in combination by some or all of the characteristics described previously or hereinafter.

[0064] The combination of the characteristics of the invention provides a method and a device which are particularly economical, giving adjusted performance levels with a good output for the most common operating ranges of the aircraft, in particular in flight, but also substantial cooling capacities when necessary, in particular on the ground, with use of electric energy, i.e. without collecting air (or with minimal collection of air) from the compression stages of the main drive turbojets of the aircraft. In particular, all the turbomachines of the device according to the invention can be motorised, each with an electric motor which is specific to it. As a variant, only some of the turbomachines, in particular at least the second turbomachine, is motorised. In addition, the recuperation of pressurisation energy of the cabin is obtained by means of the air of the turbine stages of the cold unit, which is incorporated in cold mode into the pneumatic supply circuit of the cabin. Furthermore it is not necessary to provide a turbomachine, the turbine of which is dedicated solely to this recuperation of energy.

[0065] It should be noted that a device according to the invention forms only one of the air conditioning devices of an aircraft, with supply of refrigerated air to an air intake of the cabin. In general the aircraft comprises two similar air conditioning devices according to the invention which supply refrigerated air to the cabin.

[0066] In a device according to the invention, one of the turbomachines can be designed, have dimensions, and be regulated specifically for flight conditions at a high altitude in which a small quantity of kilogram calories is necessary, and the supply can be provided by this machine alone. The other turbomachine comprising the second turbine stage makes it possible to recuperate the pneumatic energy obtained from the pressurised cabin air. In fact, a certain quantity of air must be discharged from the cabin, in particular in order to renew the oxygen in the latter. On the other hand, in conditions of functioning on the ground or at a low altitude, a large quantity of kilogram calories must be supplied, and this can be obtained in cold mode by combined use of the two turbomachines, and in particular of the two turbine stages, in series. The speed of one and/or the other of the turbomachines can be piloted in order to adjust the power consumed strictly to the kilogram calorie load required in the cabin.

[0067] Other objects, characteristics and advantages of the invention will become apparent from reading the following description provided with reference to the attached figures which represent a preferred embodiment of the invention, and in which:

[0068] FIG. 1 is a general block diagram of an air conditioning device according to the invention;

[0069] FIG. 2 is a block diagram of the device in FIG. 1 illustrating the circulation of the air in cold operating mode;

[0070] FIG. 3 is a block diagram of the device in FIG. 1 illustrating the circulation of the air in economy operating mode;

[0071] FIG. 4 is a block diagram of the device in FIG. 1 illustrating the circulation of the air in turbo-cold operating mode;

[0072] FIG. 5 is a block diagram of the device in FIG. 1 illustrating the circulation of the air in an operating mode known as defrosting mode;

[0073] FIG. 6 is a diagram illustrating an example of a command for selection of an economy mode; and

[0074] FIG. 7 is a diagram illustrating an example of a command for selection of a turbo-cold mode.

[0075] The air conditioning device represented in FIG. 1 constitutes an autonomous assembly (pack) which can supply air in all the operating modes of an aircraft (civilian or military aeroplane, helicopter, etc.) in order to control the temperature and pressure of the air in the closed and pressurised cabin 30 of this aircraft from a source 15 of external air under dynamic pressure. In practice this source 15 is formed by an air collection mouth provided in the flight deck of the aircraft, and thus makes it possible to collect air from the atmosphere. In general the aircraft comprises two similar air conditioning devices in order to prevent a total breakdown of the air conditioning in flight.

[0076] The air conditioning device substantially comprises two motorised turbomachines 1, 2 with an electric motor, respectively 12, 22, i.e. a high-pressure turbomachine 1 and a low-pressure turbomachine 2. The first, high-pressure turbomachine 1 comprises a compression stage 11, known as the first compression stage, and a turbine stage 13, known as the first turbine stage 13, which are connected to one another by a drive shaft to which an electric motor 12 is coupled. These compression 11 and turbine 13 stages can comprise one or a plurality of rotary compression or turbine elements, i.e. respectively one or a plurality of compressors and one or a plurality of turbines. These stages can be provided in the form of axial or centrifugal or combined turbomachines.

[0077] The second turbomachine 2 can be identical to the first, and can comprise a compression stage, known as the second compression stage 21, and a turbine stage, known as the second turbine stage 23, which are coupled and connected to one another by a drive shaft to which an electric motor 22 is coupled.

[0078] Throughout the text the terms “first” and “second” or their derivatives are used solely to distinguish the elements of one turbomachine from those of another turbomachine; they must therefore not be understood as imposing any order of the elements, in particular relative to the direction of circulation of the air, the variations of pressure or variations of temperature.

[0079] In each turbomachine 1, 2, the drive shaft renders the electric motor 12, 22 integral in rotation with the turbine stage 13, 23 and with the compression stage 11, 21. The coupling thus provided is therefore preferably mechanical, the compression stage 11, 21, the turbine stage 13, 23 and the electric motor 12, 22 having a single common rotor. As a variant, this coupling can nevertheless be provided in electric form, the turbine stage 13, 23 driving an electric generator which supplies the electric motor 12, 22 which drives the compression stage 11, 21 on a different rotor. As a variant, the coupling can also be provided according to any other distinct operating mode, for example magnetic, hydraulic, etc.

[0080] In FIG. 1, the arrows represent the possible directions of circulation of the air. The external air under dynamic pressure obtained from the source 15 is supplied by a pipe 40 via a first outlet of a distribution valve V14 on an air intake 41 of the second compression stage 21. A second outlet of the valve V14 is connected by a pipe 79 to an air intake 44 of the first compression stage 11 in order to supply the latter directly with air obtained from the source 15, without going via the second compression stage 21. The compressed air discharged from this second compression stage 21 via an air outlet 42 of the latter is supplied via a pipe 43 to an air intake 44 of the first compression stage 11. A pipe 18 is connected in parallel to the pipe 43 via a distribution valve V9 between the two compression stages 11, 21 in order to be able to supply compressed air to an auxiliary device 16 which is for example a defrosting system. An air outlet 45 of the first compression stage 11 is connected by a pipe 46 to the intake 47 of a cooling circuit 3b of a heat exchanger 3, known as the intermediate exchanger, which makes it possible to cool the compressed air obtained from the compression stages 11, 21 in series. The intermediate exchanger 3 comprises a cold source circuit 3a which is supplied from the source 15 of external air which acts as a cold source, by means of a fan 4. The air which thus circulates in the cold source circuit of the intermediate exchanger 3 is then expelled to the atmosphere. The output of air which enters the air intake 47 of the cooling circuit of the exchanger 3 obtained from the compression stages 11, 21 is discharged from the cooling circuit of the intermediate exchanger 3 by an air outlet 48 of the latter, at a lower temperature but in the compressed state.

[0081] The pipe 49 which is connected to the air outlet 48 of the cooling circuit of the intermediate exchanger 3 makes it possible to supply compressed air to one of three branched pipes 50, 51, 52. Via the branched pipe 52 the air is supplied to a condensation loop 5. Another branched pipe 51 comprises a valve V1, and makes it possible to supply the air directly to an air intake 57 of the first turbine stage 13 without passing via the condensation loop 5. When the valve V1 is closed, the air passes via the branched pipe 52 through the condensation loop 5, then returns to the branched pipe 51 in order to be supplied to the air intake 57 of the first turbine stage 13.

[0082] The condensation loop 5 comprises a first cooler exchanger 6 which is connected via a pipe 53 to a second cooler exchanger 7, which itself is connected via a pipe 54 to a liquid water extractor 8. The extractor 8 supplies cold air as a cold source to the first exchanger 6 for the first cooling of the air supplied via the branched pipe 52 in the condensation loop 5. The extractor 8 is thus connected to the cold source circuit of the first exchanger 6 via a pipe 55, and the outlet of this cold source circuit is connected via a pipe 56 downstream from the valve V1 to the branched pipe 51 which is connected to the air intake 57 of the first turbine stage 13. The second cooler exchanger 7 operates at a lower temperature and there passes through it the air obtained from the second turbine stage 23 which acts as a cold source for this second cooler exchanger 7. At the outlet of the condensation loop 5, the compressed air is thus at least substantially at the same pressure and the same temperature which it had at the intake of the condensation loop 5, but all traces of water vapour or liquid water have been cleared from it.

[0083] After depressurisation and cooling through the first, high-pressure turbine stage 13, the air is discharged via an air outlet 58 of this first turbine stage 13, which is connected by a pipe 59 to an air intake 60 of a cold source circuit 9a (forming a refrigerating air circuit 9a) of a heat exchanger 9, known as the cabin exchanger 9, in which this air obtained from the first turbine stage 13 acts as a cold source. This cabin exchanger 9 also comprises a cooling circuit 9b which is associated in heat exchange with the cold source circuit 9a. There passes through this cooling circuit 9b air obtained from the cabin 30 via an outlet 31 of this cabin 30, a motorised fan 32, a valve V10 and a pipe 76 which leads to the intake of the cooling circuit 9b of the cabin exchanger 9. The air is discharged from the cooling circuit 9b of the cabin exchanger 9 via a pipe 77 in which it is in the cooled state. The cabin exchanger 9 thus makes it possible to create a flow of calories from the cabin air which circulates in the cooling circuit 9b, to the refrigerating air which passes through the cold source circuit 9a. The air outlet 61 of the cold source circuit 9a of the cabin exchanger 9 is connected to a main pipe 64 upstream from an outlet valve V6 which connects this main pipe 64 to a supply pipe 78 of the cabin which leads to an air intake 33 of the cabin 30. The supply pipe 78 is also provided with a discharge valve V13, which makes it possible if necessary to disconnect the air conditioning device completely from the cabin by supplying the air obtained from this device to a pipe 79, the outlet of which discharges to the external atmosphere 17.

[0084] In addition, the main pipe 64 can be supplied by the hot compressed air obtained from the compression stages via a pipe 19 which connects the outlet pipe 46 of the compression stages 11, 21 to the main pipe 64 by means of a valve V5. This valve V5 thus makes it possible to supply the cabin 30 at least partially with hot compressed air, and to regulate the temperature TE in the supply pipe 78.

[0085] Another branched pipe 50 is connected to the pipe 49 by means of a valve V7, and this branched pipe 50 leads directly downstream from the outlet valve V6 of the main pipe 64 but upstream from the discharge valve V13, such as also to permit supply of the cabin 30 by compressed air obtained from the cooling circuit of the intermediate exchanger 3, without passing via the turbine stages 13, 23, i.e. without passing via the cold unit of the air conditioning device.

[0086] The main pipe 64 is also connected via a pipe 65 comprising a valve V3 to an air intake 66 of the second turbine stage 23. In addition, the air outlet 58 of the first turbine stage 13 can be connected directly to the main pipe 64 by means of a pipe 63 comprising a valve V2. This pipe 63 and this valve V2 make it possible to disconnect the cold source circuit of the cabin exchanger 9 from the pneumatic supply circuit of the cabin.

[0087] The two turbine stages 13, 23 can be connected in series, the air output from the air outlet 58 of the first turbine stage 13 being supplied to the air intake 66 of the second turbine stage 23, either directly via the valves V2 and V3 and the pipes 63, 64, 65; or indirectly, if the valve V2 is closed, via the cold source circuit 9a of the cabin exchanger 9 and the pipes 59, 62, 64 and 65, and the valve V3.

[0088] The air outlet 71 of the second turbine stage 23 is connected via a pipe 72 to the cold source circuit of the second cooler exchanger 7 of the condensation loop 5, from which it is discharged via a pipe 73 which leads to a distribution valve V8. This distribution valve V8 is connected on one side by a pipe 74 to the supply pipe 78 for the cabin downstream from the valve V6 of the main pipe 64, but upstream from the discharge valve V13. This pipe 74 thus connects a first outlet V8a of the valve V8 to the supply pipe 78. The valve V8 has a second outlet V8b which is connected by a pipe 75 to the cold source circuit 3a of the intermediate exchanger 3, the cooling circuit 3b of which is disposed downstream from the compression stages 12, 21. Thus, at least a fraction of the depressurised cold air output from the second turbine stage 23 can be used as a cold source mixed with the external air, or in the place of this external air, in order to cool the compressed air downstream from the compression stages 11, 21. This air supplied by the pipe 75 to the intermediate exchanger 3 is then expelled to the external atmosphere by means of the fan 4.

[0089] The cabin 30 comprises a valve V12 for pressurisation and discharge which makes it possible to discharge the surplus air in the cabin into the external atmosphere 17 via a discharge pipe 70 and a valve V11 for closure of the discharge. This valve V12 for pressurisation and discharge is connected in parallel upstream from the closure valve V11 to a pipe 68 which makes it possible to supply air obtained from the cabin 30 to an intake 67 of the second turbine stage 23, by means of a valve V4. When this valve V4 is open and the cabin 30 is pressurised, an output of air is thus discharged via the valve V12 for pressurisation and discharge and is supplied to the second turbine stage 23 at the air intake 67, by means of the pipe 68.

[0090] The conditioning method implemented in this device is illustrated by FIGS. 2 to 5 which represent respectively different operating modes. In these figures, the path of the air is represented by arrows, the absence of arrows signifying that the air is not circulating in the pipes. Depending on the operating mode, the two turbine stages 13, 23 are connected in series in order to supply the maximum cold, or on the other hand the second turbine stage 23 is disconnected from the cabin supply circuit 30, only the first turbine stage 13 supplying cold air to the cabin 30. In this last case, the second turbine stage 23 is supplied by the pipe 68 by air obtained from the cabin, the pneumatic energy of which is recuperated either in mechanical form by driving the first compression stage 21 (and/or any other rotary unit which can be connected to the rotor of the second turbomachine 2, for example one of the fans 4, 32) and/or in refrigerating form by using the cold air obtained from the second turbine stage 23 as a cold source in the exchanger 3.

[0091] FIG. 2 represents a first operating mode, known as the cold mode, in which the two turbine stages 13, 23 are in series and both supply the supply pipe 78 of the cabin 30. In a variant embodiment of the cold mode, the valve V2 is open such that the air obtained from the first turbine stage 13 is supplied directly to the intake 66 of the second turbine stage 23, without passing via the cabin exchanger 9. All of the cold air output which reaches the valve V8 is supplied to the intake 33 of the cabin 30. It should be noted that in cold mode it is possible to use or not to use a fraction of the output obtained from the outlet 71 of the second turbine stage 23, not to supply the cabin 30 directly but to supply the cold source circuit 3a of the intermediate exchanger 3, according to the temperature which exists inside the cabin 30. If this temperature is already sufficiently cold, it is thus possible to use a fraction of the cold output supplied by the turbine stages 13, 23 in order to cool the intermediate exchanger 3, by means of the distribution valve V8 which will be able to direct a fraction of this output to its outlet V8b via the pipe 75 returning to the cold source circuit of the intermediate exchanger 3.

[0092] In the operating mode known as the economy mode shown in FIG. 3, the valve V3 is closed and the valve V6 is open, such that the air obtained from the first turbine stage 13 is supplied directly to the cabin 30 by the supply pipe 78, without passing via the second turbine stage 23, the latter being disconnected from the air supply circuit of the cabin 30. The valve V4 is open and the pipe 68 supplies the air intake 67 of the second turbine stage 23 with air obtained from the cabin 30. The cold air obtained from the second turbine stage 23, at a pressure lower than that of the cabin 30, is supplied entirely by means of the distribution valve V8 to the supply pipe 75 of the cold source circuit of the exchanger 3.

[0093] FIG. 4 represents a mode, known as the turbo-cold mode, in which the cooling of the cabin 30 is the greatest and which can be used for example when the temperature inside the cabin 30 is very high, as is the case after the aircraft has been left for a long time on the ground in the sun. In this case the fan 32 at the outlet of the cabin 30 is activated such as to make a high output of air obtained from the cabin 30 pass through the cooling circuit 9b of the cabin exchanger 9. This high air output, which is for example approximately 80% of the total air output which enters the cabin 30, returns to the cabin 30 via the supply pipe 78 after being cooled by passage into the cooling circuit 9b of the cabin exchanger 9. For the cooling of this large output of air, the cold source circuit 9a of the cabin exchanger 9, which is interposed between the outlet 58 of the first turbine stage 13 and the intake 66 of the second turbine stage 23, is supplied by the cold air obtained from the first turbine stage 13. This therefore creates a high flow of calories from the cabin air 30 to the air which circulates in the cold source circuit 9a, the temperature of the air at the intake of this cold source circuit 9a being lower than that of the air obtained from the cabin 30 which enters the cooling circuit 9b. Otherwise the diagram is similar to that in FIG. 2 which corresponds to the cold mode. The output of cold air obtained from the second turbine stage 23 can be supplied only partially (for example 20%) to the supply pipe 78 of the cabin, the other part (for example 80%) being supplied to the cold source circuit 3a of the intermediate exchanger 3. In fact, in this turbo-cold mode, the cooling is obtained mainly via the cabin exchanger 9, and the low temperature of the air at the outlet of the second turbine stage 23 (obtained with a lower output than that which circulates in the cooling circuit of the cabin exchanger 9) has lower cooling efficiency.

[0094] FIG. 5 represents another possible operating mode, known as the defrosting mode. In this operating mode, the two compression stages 11, 21 are supplied in parallel from the external air source 15, via the distribution valve V14 which supplies the two pipes 40, 79. In addition, the compressed air obtained from the second compression stage 21 is supplied not to the first compression stage 11, but by the pipe 18 and the distribution valve V9, to an auxiliary device 16 which is for example a defrosting device. Instead of being supplied directly from the external air source 15, the second compression stage 11, 21 can be supplied by the air discharged from the outlet of the cold source circuit 3a of the intermediate exchanger 3, i.e. downstream from the fan 4. This air is in fact heated, such that the air supplied to the auxiliary device 16 will be warmer. In the variant represented in this operating mode, the second turbine stage 23 is totally disconnected from the air conditioning device, put into free-wheeling mode, and is no longer used. The cold air which reaches the supply pipe 78 is supplied only by the first turbine stage 13, via the valve V2 and the valve V6.

[0095] Table 1 hereinafter represents the state of the different valves of the device according to the invention depending on the operating modes.

[0096] Table 2 hereinafter shows the orders of magnitude, by way of example, of the temperatures and pressures which can be obtained at different points of the circuit represented by upper case letters in the diagrams, according to the different operating modes. The pressure values are static pressures (i.e. such that they could be displayed by an absolute pressure sensor connected to a wall sampling tube).

[0097] It should be noted that in the tables, it has been taken into account in the defrosting mode that the two turbine stages 13, 23 are in series, unlike the variant represented in FIG. 5. In economy mode, at high altitude, the valve V1 can be opened when the condensation loop is not useful, or otherwise closed. 1 TABLE 1 MODE V1 V2 V3 V4 V5 V6 V8a V8b V9 V10 V11 V14 Cold closed open open closed Variable closed open closed open closed open open for towards towards temperature 11 21 control Economy closed open closed open closed open closed open open closed closed open or towards towards open 11 21 Turbo-cold closed closed open closed closed closed partly partly open open open open open open towards towards (for (for 11 21 example example 20%) 80%) Defrosting closed open open closed Variable closed open closed open open open open for towards towards temperature 16 11 and control 21

[0098] 2 TABLE 2 MODE A B C D E F G H I J K L M N O P Q R cold ° C. 15 100 200 40 25 20 20 35 −5 −5 −5 −5 −35 10 — 25 10 20 to 20 105 1 2 4 4 4 4 4 4 2 2 2 2 (V4 1.2 1.2 — 1.1 1.1 1.0 Pa is closed) economy ° C. −30 90 230 40 40 40 40 40 0 0 0 24 −50 −50 30 15 0 24 to 20 105 0.2 0.6 1.5 1.5 1.5 1.5 1.5 1.5 0.9 0.9 0.9 0.75 0.15 0.15 0.8 0.8 0.85 0.75 Pa (V4 is open) turbo-cold ° C. 40 150 250 50 30 25 25 45 0 35 35 35 −10 20 45 25 20 45 105 1 2 4 4 4 4 4 4 2 2 2 2 (V4 1.2 1.2 1.2 1.1 1.1 1.0 Pa is closed) defrosting ° C. −20 60 150 40 20 20 20 40 5 5 5 5 −20 20 20 20 20 20 to 20 105 0.7 1.5 3 3 3 3 3 3 1.5 1.5 1.5 1.5 (V4 1.1 1.1 1.1 1.0 1.0 0.9 Pa is closed)

[0099] The valves of the pneumatic circuit can consist of any device which can make the output vary (variable injection cross-sections; solenoid valves; butterfly valves; plug valves; guillotine valves, etc).

[0100] The conditioning device according to the invention additionally comprises an automatic electronic device to control the state of the different valves. It should be noted that the two valves V3, V4 which permit selective supply of air to the second turbine stage 23 are valves of which only one can be open (and not both at once). The valve V3 is closed in economy mode and open in cold mode. This valve V3 can be an all-or-nothing valve. The valve V4 is closed in cold mode and open in economy mode. The opening of the valve V4 can be varied in economy mode in order to modulate the power supplied by the second turbine stage 23. In this case, the valve V4 is an adjustable opening modulation valve.

[0101] Otherwise, the remaining valves must be modulation valves which are or are not regulated, or all-or-nothing valves. Preferably, solenoid valves which are controlled electrically by the automatic control device are used.

[0102] This automatic control device selects or does not select the economy mode on the basis of the measurement of at least one parameter which represents the pressure difference between the pressure in the cabin and the external atmospheric pressure, which corresponds to the altitude of the aircraft. In fact, the principle of recuperation of energy by the second turbine stage 23 becomes useful and efficient only when the pressure which exists inside the cabin 30 is greater than the external atmospheric pressure, by a sufficient value. This pressure difference is directly associated with the altitude, i.e. in practice with the external atmospheric pressure measured. It is therefore sufficient to measure the external atmospheric pressure as a parameter which is representative of the pressure difference. However, as a variant or in combination, any other parameter(s) representative of this pressure difference can be measured, i.e. air pressure in the cabin; altitude of the device; pressure difference (measured directly by a differential pressure sensor).

[0103] If necessary, the automatic control device can be adapted to have a hysteresis (FIG. 6), i.e. the upper pressure difference threshold &Dgr;Psup, which permits triggering of the economy mode, can be greater (corresponding to a greater altitude Zsup) than the lower pressure threshold &Dgr;Pinf, starting from which the cold mode is selected once more. In fact the economy mode is selected when the pressure difference is greater than the upper pressure difference threshold and on the other hand the cold mode is selected when the pressure difference is lower than the lower pressure difference threshold. As a variant these pressure difference thresholds can be equal. Preferably, the difference between the thresholds &Dgr;Psup−&Dgr;Pinf is selected such as to be constant and sufficient to prevent switching from one mode to the other for small variations of altitude of the aircraft.

[0104] In the example represented in FIG. 6, the economy mode ME is selected when the aircraft ascends (solid lines) when &Dgr;Psup is reached. Starting from this altitude Zsup, V3 is closed and V4 is modulated in order to relieve the motor 22 of the second turbomachine 2. In descent (dotted lines), the cold mode MF is triggered only when &Dgr;Pinf is reached, at the altitude Zinf, when V3 is open and V4 is closed.

[0105] For example, the upper pressure difference threshold &Dgr;Psup which permits selection of the economy mode, and corresponds to flights at a high altitude, can be selected to correspond to an altitude of approximately 22,000 feet (6,700 metres). At an altitude lower than this value, the mode selected can be either the cold mode or the turbo-cold mode (on the ground in order to cool the aircraft if the temperature measured in the cabin is too great), or the defrosting mode on the ground or at low altitude if the need for defrosting is detected and/or ordered by the crew.

[0106] Each pressure difference threshold &Dgr;Pinf and &Dgr;Psup can be a predefined fixed value, or on the other hand it can be determined and adjusted according to the kilogram calorie power PF to be supplied to the cabin.

[0107] The device comprises means for measurement of at least one parameter which is representative of the kilogram calorie requirement of the cabin, i.e. of the kilogram calorie power which is necessary in order to maintain the required thermal environment in the cabin. In particular, at least the temperature of the air in the cabin TC is measured. The kilogram calorie power PF supplied to the intake 33 of the cabin is:

PF=C×Q(TE−TC)

[0108] in which:

[0109] C is the calorific capacity of the air,

[0110] Q is the output supplied,

[0111] TE is the temperature of the air at the intake 33 of the cabin 30.

[0112] The automatic control device is designed to adjust the refrigerating power PF in order to minimise the difference TC−TSEL, in which TSEL is the set temperature, which can be regulated by the crew, required in the cabin.

[0113] According to the invention the speed of at least one of the motors 12, 22 is adjusted and therefore so is that of at least one corresponding compression stage 11, 21, which makes the values of TE and Q vary, and therefore that of PF. The position of valves can also advantageously be varied in order to vary TE and Q.

[0114] For example TC and Q are measured, the speed of the motor 22 of the second turbomachine 2 is piloted in order to obtain a required output (predefined in order to obtain renewal of air and minimum pressurisation in the cabin), and the position of the valve V5 is regulated such as to maintain the temperature TC equal to the set temperature TSEL. In this example, the speed of the motor 12 of the first turbomachine 1 is maintained permanently constant. Also by way of example, the thresholds &Dgr;Pinf and &Dgr;Psup are dependent on the measurement of the external atmospheric temperature (thus making it possible to estimate the need for kilogram calories to be supplied to the cabin): they are all the higher, the higher the external atmospheric temperature measured.

[0115] The thresholds which permit triggering and interruption of the turbo-cold mode can also be distinct, in order to have a hysteresis as previously described for the pressure difference thresholds, or on the contrary they can be equal.

[0116] For example the hysteresis for selection of the turbo-cold mode is that represented in FIG. 7. In this example, if the temperature difference TC−TSEL is greater than the upper temperature difference threshold &Dgr;T (for example approximately 10° C.), the turbo-cold mode is selected, and remains active (A; dotted lines) until the set temperature TSEL is obtained in the cabin (TC−TSEL=0, in this example corresponding to the lower temperature difference threshold). Starting from this point the turbo-cold mode is deactivated (I) and a normal mode is selected, for example the cold mode. In order to prevent untimely activation of the turbo-cold mode, the latter can be selected when TC−TSEL increases, only starting from the upper threshold &Dgr;T (solid lines).

[0117] The method for control used can form the basis of many variant embodiments compared with the above-described example, according to the constraints and applications specific to each aircraft.

[0118] An automatic control device of this type can be produced in a well-known conventional manner in order to provide the above-described functions, and does not need to be described in greater detail.

[0119] The invention can form the basis of very many variant embodiments in comparison with the non-limiting examples described above and represented in the figures. For example the condensation loop 5 can be produced in a very different manner, or can even be eliminated if this is possible. The second turbine stage 23 which makes it possible to recuperate the energy can also be coupled to a fan.

[0120] Similarly, the conditioning device can comprise more than two turbine stages and/or more than two compression stages, i.e. more than two turbomachines 1, 2. In any case, the turbine stage with the lowest supply pressure will be used as a second turbine stage for recuperation of energy by supply by air obtained from the cabin 30 as previously described, in economy mode.

[0121] In addition, the air extracted from the cabin 30 via the pipe 68 and supplied to the intake 67 of the second turbine stage 23 can optionally be processed, and in particular cleaned, disinfected, filtered etc, and even heated or cooled before passing into the second turbine stage 23. For example it can be used in order to pass through a heat exchanger before reaching the intake 67 of the second turbine stage 23.

[0122] In addition, in cold mode, contrary to the example previously given in table 1, it is possible to close the valve V2 and open the valve V10, and to activate the recirculation fan 32 such as to use the cabin exchanger 9 partially, with a reduced output (for example approximately 50% of the total output which enters the cabin 30) which is lower than the high output used with the turbo-cold mode. The flow of calories which passes from the cabin air to the refrigerating air circuit 9a is smaller in cold mode than the high flow created in turbo-cold mode. The cold mode is thus a mode which is known as a normal mode, in comparison with the turbo-cold mode. The same applies for the economy mode and the defrosting mode, each being qualified as a normal mode in comparison with the turbo-cold mode. In economy mode and in defrosting mode, the output which circulates in the cooling circuit 9b of the cabin exchanger 9 is zero, the circulation fan 32 being deactivated. In addition, in place of a single cabin exchanger 9, use can be made of more complex heat exchange means between the refrigerating air circuit 9a incorporated in the pneumatic circuit which supplies the cabin and the cooling circuit 9b. For example, two distinct heat exchangers can be provided, connected by a common calorific transport circuit comprising a fluid which is refrigerating (with intermediate means for refrigeration) or non-refrigerating, one of these exchangers comprising the refrigerating air circuit 9a whereas the other comprises the cooling circuit 9b, the latter being able to be incorporated totally in the cabin 30.

[0123] As a variant it is also possible to adjust the speed of the two motors 12, 22, for example by making the speed of the motor 12 dependent on that of the motor 22. In other variants, one of the two motors 12 or 22 can be eliminated.

[0124] Finally, the air which supplies the air conditioning device is preferably obtained (directly) entirely from the source 15 of external atmospheric air (which is not previously compressed mechanically or obtained from the turbojets). As a variant, a fraction of the air can nevertheless be obtained from the compression stages of the turbojets or means for prior mechanical compression other than those of the two above-described turbomachines.

Claims

1. A method for air conditioning to control the temperature and pressure of the air in an aircraft cabin (30) from at least one source of air (15), implemented in an air conditioning device comprising:

at least one turbine stage (13, 23) for depressurisation/cooling comprising at least one air intake and at least one outlet (58, 71) for depressurised and cooled air, each turbine stage (13, 23) being connected to means (11, 21) for mechanical compression of air, such as to participate in the driving of these means;

drive means (12, 22) with non-pneumatic energy which are connected to the means (11, 21) for compression, such as to participate in the driving of these means;

a pneumatic supply circuit for the cabin with pipes and controlled valves, which is designed to be able to supply the means (11, 21) for compression from an air output obtained from the source of air (15), to supply at least one turbine stage (13) from a compressed air output obtained from the means (11, 21) for compression, and to supply at least one air intake (33) of the cabin (30) with the air obtained from the air outlet (71) of at least one turbine stage (23), and wherein the controlled valves of the pneumatic supply circuit of the cabin are controlled in order to configure the circuit according to an operating mode selected from amongst different operating modes, each of which corresponds to specific characteristics of output and/or temperature and/or pressure of the output of air supplied to the cabin (30),

wherein the air conditioning device comprises:

at least two distinct turbomachines (1, 2) each comprising a compression stage (11, 21) and a turbine stage (13, 23) connected to the compression stage (11, 21), at least one of the turbomachines being motorised and comprising a motor (12, 22) with non-pneumatic energy connected to the compression stage (11, 21);

at least one parameter which is representative of the pressure difference between the air in the cabin and the external atmosphere, known as the pressure difference, is measured;

when the pressure difference measured is greater than an upper pressure difference threshold, an operating mode known as economy mode is activated, in which:

the turbine stage, known as the second turbine stage (23), of at least one of the turbomachines, known as the second turbomachine (2), is supplied exclusively via means, known as second supply means (68, V4), by an air output obtained from an air outlet (V12) of the cabin (30), and the pressure of which is, with the exception of losses of load, that of the air pressure which exists in the cabin (30); and

the air outlet (71) of the second turbine stage (23) is isolated from the pneumatic supply circuit of the cabin (30), such that no output of air supplied in the cabin (30) is obtained from the air outlet (71) of the second turbine stage (23);

when the pressure difference measured is lower than a lower pressure difference threshold, an operating mode known as cold mode is activated, in which the compression stages (11, 21) of the turbomachines (1, 2) are connected in series from the source (15) of air, and the drive speed of at least one turbomachine (1, 2) motor (12, 22) is adjusted such as to adjust the refrigerating power supplied by the air conditioning device, and wherein the second turbine stage (23) is incorporated in the pneumatic supply circuit of the cabin (30).

2. A method as claimed in claim 1, wherein in economy mode the second turbine stage (23) is supplied by an air output obtained from the cabin (30) directly via a pipe (68) and a controlled valve (67), such as to enter the second turbine stage (23) at least substantially at the pressure and temperature of the air which exists in the cabin (30), with the exception of circulation losses.

3. A method as claimed in claim 1 or claim 2, wherein in cold mode the second turbine stage (23) is supplied by an air output obtained from the air outlet (58) of at least one other turbine stage, known as the first turbine stage (13), this air output reaching the intake (66) of the second turbine stage (23) at least substantially at the same pressure as at the outlet (58) of the first turbine stage (13), with the exception of losses of load, and the cabin (30) is supplied with at least a fraction of the output of air obtained from the air outlet (71) of the second turbine stage (23).

4. A method as claimed in claim 3, wherein, since the second turbomachine (2) is motorised, the first turbine stage (13) belongs to a first motorised turbomachine (1) comprising a motor (12) distinct from the motor (23) of the second turbomachine (2).

5. A method as claimed in any one of claims 1 to 4, wherein the drive speed of a single turbomachine motor (12, 22) is adjusted.

6. A method as claimed in any one of claims 1 to 5, wherein in cold mode, the second turbine stage (23) is not supplied by air obtained from the cabin (30).

7. A method as claimed in any one of claims 1 to 6, wherein the lower pressure difference threshold and/or the upper pressure difference threshold are adjusted such as to adjust the refrigerating power supplied by the air conditioning device.

8. A method as claimed in any one of claims 1 to 7, wherein in economy mode, at least one fraction of the air output from the second turbine stage (23) is used as a cold source of at least one heat exchanger (3).

9. A method as claimed in any one of claims 1 to 8, wherein at least in cold mode, the compressed air supplied by the compression stages (11, 21) is cooled by passing it through a cooling circuit of at least one heat exchanger, known as the intermediate exchanger (3), before it is supplied to the air intake of at least one turbine stage (13, 23) incorporated in the pneumatic supply circuit of the cabin (30), and wherein, in economy mode, at least one fraction of the air output from the second turbine stage (23) is used as a cold source for this intermediate exchanger (3).

10. An air conditioning device which is designed to control the temperature and pressure of the air in an aircraft cabin (30) from at least one source of air (15) comprising:

at least one turbine stage (13, 23) for depressurisation/cooling comprising at least one air intake and at least one outlet (58, 71) for depressurised and cooled air, each turbine stage (13, 23) being connected to mechanical means (11, 21) for compression of air, such as to participate in driving the latter;

drive means (12, 22) with non-pneumatic energy which are connected to the means (11, 21) for compression, such as to participate in driving the latter;

a pneumatic circuit to supply the cabin, with pipes and controlled valves, which is designed to be able to supply the means (11, 21) for compression from an air output obtained from the source of air (15), to supply at least one turbine stage (13) from a compressed air output obtained from the means (11, 21) for compression, and to supply at least one air intake (33) of the cabin (30) with air obtained from the air outlet (71) of at least one turbine stage (23);

automatic means to control the controlled valves of the pneumatic circuit, which means are designed to configure the pneumatic supply circuit of the cabin (30) according to different operating modes, each corresponding to specific characteristics of output and/or temperature and/or pressure of the air output supplied to the cabin (30),

wherein the device comprises:

at least two distinct turbomachines (1, 2) each comprising a compression stage (11, 21) and a turbine stage (13, 23) connected to the compression stage (11, 21), at least one of the turbomachines being motorised and comprising a motor (12, 22) with non-pneumatic energy connected to the compression stage (11, 21);

means for measurement of at least one parameter which is representative of the difference, known as the pressure difference, between the air pressure in the cabin (30) and the external atmospheric pressure;

and wherein the means for automatic control and the pneumatic circuit for supply of the cabin are designed such as:

when the pressure difference measured is higher than an upper pressure threshold, to activate an operating mode, known as the economy mode, in which:

the turbine stage, known as the second turbine stage (23), of at least one of the turbomachines, known as the second turbomachine, is supplied exclusively via means, known as second supply means (68, V4), by an air output obtained from an air outlet (V12) of the cabin (30), and the pressure of which is, with the exception of losses of load, that of the air pressure which exists in the cabin (30); and

the air outlet (71) of the second turbine stage (23) is isolated from the pneumatic supply circuit of the cabin (30), such that no output of air supplied in the cabin (30) is obtained from the air outlet (71) of the second turbine stage (23);

when the pressure difference measured is lower than a lower pressure difference threshold, an operating mode known as cold mode is activated, in which the compression stages (11, 25) of the turbomachines (1, 2) are connected in series from the source of air (15), and the drive speed of at least one turbomachine (1, 2) motor (12, 22) is adjusted such as to adjust the refrigerating power supplied by the air conditioning device, and wherein the second turbine stage (23) is incorporated in the pneumatic supply circuit of the cabin (30).

11. A device as claimed in claim 10, wherein the second supply means (68, V4) consist of a pipe (68) which connects the air outlet (V12) of the cabin (30) to an air intake (67) of the second turbine stage (23) and of a controlled valve (V4) which is interposed on this pipe (68), the air supplied to the second turbine stage (23) by the second supply means (68, V4) in economy mode being, with the exception of circulation losses, at least substantially at the pressure and temperature of the air which exists in the cabin (30).

12. A device as claimed in claim 10 or claim 11, wherein in cold mode, the second turbine stage (23) is supplied via means, known as first supply means (59, 62, 63, 64, 65, V2, V3), by an air output obtained from the air outlet (58) of at least one other turbine stage, known as the first turbine stage (13), and the pneumatic circuit (V2, 63, 64, V6, V13, 65, V3, 72, 73, V8, 78) for supply to the cabin supplies the cabin (30) with at least one fraction of the air output obtained from the air outlet (71) of the second turbine stage (23).

13. A device as claimed in claim 12, wherein the second turbomachine (2) is motorised and the first turbine stage (23) belongs to a first motorised turbomachine (1) comprising a motor (12) which is distinct from the motor (23) of the second turbomachine (2).

14. A device as claimed in any one of claims 10 to 13, wherein the second turbomachine (2) is motorised and the automatic means for control are designed to adjust the drive speed of a single turbomachine motor (12 or 22).

15. A device as claimed in any one of claims 10 to 14, wherein in cold mode, the second turbine stage (23) is not supplied by the second supply means (68, V4).

16. A device as claimed in any one of claims 10 to 15, wherein the first supply means (59, 62, 63, 64, 65, V2, V3) are designed to supply in cold mode to the intake (66) of the second turbine stage (23) an air output which is at least substantially, with the exception of losses of load, at the air pressure at the outlet (58) of the first turbine stage (13).

17. A device as claimed in any one of claims 10 to 16, wherein the means for automatic control are designed to adjust the lower pressure difference threshold and/or the upper pressure difference threshold such as to adjust the refrigerating power supplied by the air conditioning device.

18. A device as claimed in any one of claims 10 to 17, wherein the device comprises means (V8, 75) which are designed to supply in economy mode at least one fraction of the air output obtained from the air outlet (71) of the second turbine stage (23), to a cold source circuit of at least one heat exchanger (3).

19. A device as claimed in any one of claims 10 to 18, wherein it comprises:

a heat exchanger, known as an intermediate heat exchanger (3), which is associated thermally with a cold source, this intermediate exchanger (3) comprising a cooling circuit with an air intake (47) which is connected to the air outlet (45) of the mechanical means (11, 21) for compression of air and an outlet (48) for cooled air;

means (49, 5) to supply the output of cooled air obtained from the cooled air outlet (48) of the intermediate exchanger (3) to the air intake (57) of at least one turbine stage (13) incorporated in the pneumatic supply circuit of the cabin; and

means (8, 75) which, in economy mode, are designed to supply at least one fraction of the output of air obtained from the air outlet (71) of the second turbine stage (23), to a cold source circuit (3a) of the intermediate exchanger (3).

20. A device as claimed in any one of claims 10 to 19, wherein it comprises thermal exchange means (9), comprising a cold source circuit (9a) which is designed to be interposed, at least in one operating mode, between the air outlet (58) of the first turbine stage (13) and the air intake (66) of the second turbine stage (23), such as to have an output of refrigerating air passing through it, these thermal exchange means (9) also being designed to create a flow of calories from the cabin air (30) to the cold source circuit (9a).

21. A device as claimed in any one of claims 10 to 20, wherein the turbine stages (13, 23) are disposed such that the pressure of the air supplied by these turbine stages (13, 23) is lowest at the outlet (71) of the second turbine stage (23), known as the second low-pressure turbine stage.

22. A device as claimed in any one of claims 10 to 21, wherein the drive means (12, 22) consist of at least one electric motor.

23. A device as claimed in any one of claims 10 to 22, wherein a compression stage (4) of a motorised turbomachine (2), known as the low-pressure compression stage (21), comprises an air intake (41) which is connected to the external source of air (15), and at least one other compression stage (11) of another motorised turbomachine (2), known as the high-pressure compression stage (11), comprises an air intake (44) which is designed to be able to be connected, in at least one operating mode, to an air outlet (42) of the low-pressure compression stage (21), such that at least one fraction of the air output obtained from the air outlet (42) of the low-pressure compression stage (21) is supplied to the intake (44) of the high-pressure compression stage (11), and wherein the second turbine stage (23) belongs to the motorised turbomachine (2) comprising the low-pressure compression stage (21), and participates in driving of the latter in economy mode and in cold mode.

24. A device as claimed in claims 12 and 23, wherein the first turbine stage (13) belongs to the motorised turbomachine (1) comprising the high-pressure compression stage (11), and participates in driving of the latter.

25. A device as claimed in any one of claims 10 to 24, wherein it comprises means (5) for condensation of the water interposed between the air outlet (45) of the mechanical means (11, 21) for compression of air and the air intake (57) of the first turbine stage (13).

26. A device as claimed in claim 25, wherein the means (5) for condensation comprise a heat exchanger (7) which is designed to have an air output which passes through it, obtained from the air outlet (71) of the second turbine stage (23).