CABIN BLOWER SYSTEM

Abstract

An aircraft cabin blower system is described having a hydraulic circuit comprising a first hydraulic device and a second hydraulic device. The first hydraulic device is mechanically coupled to a cabin blower compressor and the second hydraulic device is arranged in use to be mechanically coupled to a spool of a gas turbine engine. The first hydraulic device is capable of performing as a hydraulic motor and the second hydraulic device is capable of performing as a hydraulic pump. When, in use, the system is operating in a cabin blower configuration, a driving force supplied by the spool of the gas turbine causes the second hydraulic device to pump liquid provided in the hydraulic circuit and thereby to drive the first hydraulic device, which in turn rotates the cabin blower compressor.

Claims

1. An aircraft cabin blower system having a hydraulic circuit comprising a first hydraulic device and a second hydraulic device, wherein the first hydraulic device is mechanically coupled to a cabin blower compressor and the second hydraulic device is arranged in use to be mechanically coupled to a spool of a gas turbine engine and where further the first hydraulic device is capable of performing as a hydraulic motor and the second hydraulic device is capable of performing as a hydraulic pump, such that when, in use, the system is operating in a cabin blower configuration, a driving force supplied by the spool of the gas turbine causes the second hydraulic device to pump liquid provided in the hydraulic circuit and thereby to drive the first hydraulic device, which in turn rotates the cabin blower compressor.

2. An aircraft cabin blower system according to claim 1 where the first hydraulic device is capable of performing as a hydraulic pump and the second hydraulic device is capable of performing as a hydraulic motor such that when, in use, the system is operating in an engine start configuration, a driving force supplied by the cabin blower compressor acting as a turbine causes the first hydraulic device to pump the liquid provided in the hydraulic circuit and thereby to drive the second hydraulic device, which in turn rotates the spool of the gas turbine engine.

3. An aircraft cabin blower system according to claim 2 where the hydraulic circuit comprises a valve assembly actuatable between a first position when the system is in the cabin blower configuration and a second position when the system is in the engine start configuration, whereby the first and second positions give rise to different porting of liquid in the hydraulic circuit such that the flow direction through the second hydraulic device is the same regardless of whether the system is operating in the cabin blower configuration or the engine start configuration and such that the flow direction through the first hydraulic device reverses in dependence upon whether the system is operating in the cabin blower configuration or the engine start configuration.

4. An aircraft cabin blower system according to claim 3 where at least one of the valve assembly, the first hydraulic device and the second hydraulic device is controllable to vary the liquid flow rate around the hydraulic circuit.

5. An aircraft cabin blower system according to claim 2 where an array of variable exit guide vanes is provided adjacent the cabin blower compressor in the same flow path, the array being provided downstream of the cabin blower compressor in the sense of a gas flow flowing through the flow path when the system is operated in the cabin blower configuration and where further the variable exit guide vanes are arranged such that they are capable of directing gas driving the cabin blower compressor such that it rotates in the same direction regardless of whether it is serving as a compressor or as a turbine.

6. An aircraft cabin blower system according to claim 2 where the spool of the gas turbine engine is a low pressure spool and the system is selectively coupleable in a driving relationship to a high pressure spool of the gas turbine engine so as to be engaged when the system is in the engine start configuration.

7. An aircraft cabin blower system according to claim 2 where in use of the system operating in the engine start configuration, the cabin blower compressor is driven by an external gas supply, the cabin blower compressor thereby acting as a turbine.

8. An aircraft cabin blower system according to claim 1 where, in use of the system operating in the cabin blower configuration, the cabin blower compressor pumps air taken from a bypass duct of the gas turbine engine.

9. An aircraft cabin blower system according to claim 1 where the system comprises a cabin blower gearbox via which the mechanical coupling between the first hydraulic device and the cabin blower compressor is made.

10. An aircraft cabin blower system according to claim 1 where the second hydraulic device is arranged in use to be mechanically coupled to an accessory gearbox of the gas turbine engine via which the mechanical coupling to the spool of the gas turbine engine is made.

11. An aircraft cabin blower system according to claim 1 where at least one of the first and second hydraulic devices is a digital displacement device.

12. An aircraft comprising a cabin blower compressor system in accordance with claim 1.

13. An aircraft according to claim 12 where the hydraulic circuit is part of and is in fluid communication with a broader aircraft hydraulic circuit comprising additional hydraulically controlled components.

14. A method of operating a cabin blower system to supply gas to an aircraft cabin comprising using drive provided by a gas turbine engine to pump a liquid and using the liquid flow to drive rotation of a cabin blower compressor.

15. A method according to claim 14 where the cabin blower compressor is mechanically coupled to a first hydraulic circuit and a spool of the gas turbine engine is mechanically coupled to a second hydraulic circuit.

16. A method of operating a cabin blower system to rotate a spool of a gas turbine engine during start of the gas turbine engine comprising using drive provided by a cabin blower compressor acting as a turbine to pump a liquid and using the liquid flow to drive rotation of the spool.

17. A method according to claim 16 where the cabin blower compressor is mechanically coupled to a first hydraulic circuit and the spool of the gas turbine engine is mechanically coupled to a second hydraulic circuit.

Description

[0038] Embodiments will now be described by way of example only, with reference to the Figures, in which:

[0039] FIG. 1 is a sectional side view of a gas turbine engine;

[0040] FIG. 2 is a schematic depiction of an aircraft cabin blower system in accordance with an embodiment of the invention.

[0041] With reference to FIG. 1, a gas turbine engine is generally indicated at 10, having a principal and rotational axis 11. The engine 10 comprises, in axial flow series, an air intake 12, a propulsive fan 13, an intermediate pressure compressor 14, a high-pressure compressor 15, combustion equipment 16, a high-pressure turbine 17, an intermediate pressure turbine 18, a low-pressure turbine 19 and an exhaust nozzle 20. A nacelle 21 generally surrounds the engine 10 and defines both the intake 12 and the exhaust nozzle 20.

[0042] The gas turbine engine 10 works in the conventional manner so that air entering the intake 12 is accelerated by the fan 13 to produce two air flows: a first air flow into the intermediate pressure compressor 14 and a second air flow which passes through a bypass duct 22 to provide propulsive thrust. The intermediate pressure compressor 14 compresses the air flow directed into it before delivering that air to the high pressure compressor 15 where further compression takes place.

[0043] The compressed air exhausted from the high-pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines 17, 18, 19 before being exhausted through the nozzle 20 to provide additional propulsive thrust. The high 17, intermediate 18 and low 19 pressure turbines drive respectively the high pressure compressor 15, intermediate pressure compressor 14 and fan 13, each by suitable interconnecting shaft.

[0044] Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. By way of example such engines may have an alternative number of interconnecting shafts (e.g. two) and/or an alternative number of compressors and/or turbines. Further the engine may comprise a gearbox provided in the drive train from a turbine to a compressor and/or fan.

[0045] Referring now to FIG. 2 an aircraft cabin blower system is generally provided at 30. In use the cabin blower system 30 is associated with a gas turbine engine (which may be similar to that described with reference to FIG. 1) of an aircraft (not shown). The gas turbine engine has a low pressure spool (not shown) and a high pressure spool (not shown). The low pressure spool drives an engine accessory gearbox 32, which is used to deliver drive from the low pressure spool to various engine and aircraft systems. One way in which drive is delivered is via hydraulics. In the embodiment of FIG. 2, two aircraft system hydraulic pumps 34 are shown mechanically coupled to the accessory gearbox 32. The aircraft system hydraulic pumps 34 are driven by the low pressure shaft via the accessory gearbox 32 and pump hydraulic fluid for use in actuation of the aircraft landing gear, flaps and control surfaces.

[0046] Turning to the cabin blower system 30 itself, there is provided a hydraulic circuit 36 comprising a first hydraulic device 38 and a second hydraulic device 40 connected by circuit conduiting 42. The first 38 and second 40 hydraulic devices are both digital displacement pumps capable of acting both as hydraulic pumps (using mechanical inlet drive to pump a hydraulic fluid around the hydraulic circuit) and as hydraulic motors (extracting kinetic energy from the hydraulic fluid and converting it to rotational mechanical motion). The circuit conduiting 42 connects the first hydraulic device 38 to the rest of the hydraulic circuit 36 at first 44 and second 46 ports of the first hydraulic device 38. The circuit conduiting 42 connects the second hydraulic device 40 to the rest of the hydraulic circuit 36 at inlet 48 and outlet 50 ports of the second hydraulic device 40.

[0047] The second hydraulic device 40 is mechanically coupled to the accessory gearbox 32 in a driving relationship, and thereby indirectly to the low pressure shaft of the gas turbine engine. The first hydraulic device 38 is mechanically coupled to a cabin blower compressor 52 provided on the aircraft via an epicyclic gearbox 54. The epicyclic gearbox 54 is serviced with engine oil by an engine oil circuit 56 comprising an engine oil pump 58 which is driven via a mechanical connection to the accessory gearbox 32. Additionally the high pressure spool is mechanically coupled to the accessory gearbox 32 via a clutched (not shown) linkage capable under the influence of the EEC of selectively decoupling the high pressure spool and accessory gearbox 32.

[0048] The cabin blower compressor 52 is disposed in a duct system (not shown) connecting a scoop (not shown) on an outer wall of a bypass duct (not shown) of the gas turbine engine and aircraft cabin air conditioning outlets (not shown). Between the cabin blower compressor 52 and the air conditioning outlets in the duct system is a starter air shut off valve assembly (not shown). The shut-off valve assembly is arranged to be operable to alternatively allow one of two conditions. In a first condition the shut-off valve assembly permits the flow of air from the cabin blower compressor 52 towards the air conditioning outlets and seals communication between the duct system and a starter conduit (not shown). The starter conduit connects the duct system at the location of the shut-off valve assembly and a port to atmosphere. In a second condition the shut-off valve assembly permits flow from the starter conduit towards the cabin blower compressor 52 and prevents flow towards the air conditioning outlets.

[0049] Immediately adjacent and upstream of the cabin blower compressor 52 (between the cabin blower compressor and the scoop) are an array of variable inlet guide vanes 60. Immediately adjacent and downstream of the cabin blower compressor 52 (between the cabin blower compressor and the air conditioning outlets) are an array of variable exit guide vanes 62.

[0050] A valve assembly 64 is provided between the first 38 and second 40 hydraulic devices in the hydraulic circuit 36. The valve assembly 64 is actuatable between a first position and a second position. In the first position a first pair of valve assembly ports in the valve assembly 64 are aligned with the conduiting 42, one port connecting conduiting leading to the outlet port 50 and first port 44 and the other port connecting conduiting leading to the inlet port 48 and second port 46. When in its first position the valve assembly 64 therefore forms the hydraulic circuit 36 into a loop. In the second position a second pair of valve assembly ports in the valve assembly 64 are aligned with the conduiting 42, one port connecting conduiting leading to the outlet port 50 and second port 46 and the other port connecting conduiting leading to the inlet port 48 and first port 44. When in its second position the valve assembly 64 therefore forms the hydraulic circuit 36 into a figure of eight. As will be appreciated, with the valve assembly 64 in its different positions, the hydraulic fluid will flow through the first hydraulic device 38 in opposite directions. Control over actuation of the valve assembly 64 between its first and second positions is exercised by a processor (in this case an electronic engine control (EEC) 66 of the gas turbine engine) under the influence of an aircraft control system 68. The valve assembly 64 is also provided with throttling functionality allowing the EEC 66 to control the flow rate of the hydraulic fluid through its ports.

[0051] A hydraulic accumulator 70 is provided in the hydraulic circuit 36 connected by the conduiting 42. In use the hydraulic accumulator 70 is partially filled with hydraulic fluid and partially filled with a compressible gas. The hydraulic circuit 36 further comprises a heat exchanger 72 through which the hydraulic fluid in the hydraulic circuit 36 passes and is brought into heat exchange relationship with air passing through a bypass duct of the gas turbine engine.

[0052] In use the cabin blower system 30 has both a cabin blower configuration (which may be considered a forward configuration) and an engine start configuration (which may be considered a reverse configuration). The cabin blower configuration allows the system 30 to perform as a cabin blower while the engine start configuration allows it to perform as part of a starter system for the gas turbine engine.

[0053] When it is desired for the cabin blower compressor 52 to provide compressed air to an aircraft environmental control system, the EEC 66 actuates the valve assembly 64 to adopt its first position. The EEC 66 further actuates the starter air shut-off valve assembly (not shown) so as it is in its first condition, and actuates the clutched linkage to decouple the high pressure spool from the accessory gearbox 32.

[0054] In the cabin blower configuration the cabin blower compressor 52 is driven by the low pressure spool of the gas turbine engine. This drive is delivered by the closed circuit hydrostatic transmission described above with reference to FIG. 2. Specifically the spool of the gas turbine engine delivers drive to the accessory gearbox 32. The accessory gearbox 32 in turn delivers drive to the aircraft system hydraulic pumps 34 and the engine oil pump 58, which respectively pump hydraulic fluid and engine oil. The accessory gearbox 32 also drives the second hydraulic device 40 causing it to perform as a hydraulic pump. Pumped by the second hydraulic device 40, hydraulic fluid leaves the outlet port 50, passes through the valve assembly 64 and enters the first port 44 of the first hydraulic device 38. Thereafter the hydraulic fluid leaves the first hydraulic device 38 via its second port 46, passes through the valve assembly 64 and returns to the second hydraulic device 40 via its inlet port 48, before recirculating again. As the hydraulic fluid passes through the first hydraulic device 38 it causes it to perform as a hydraulic motor and to drive the cabin blower compressor 52 via the epicyclic gearbox 54. The epicyclic gearbox 54 is lubricated and cooled by the engine oil pumped from the engine oil pump 58.

[0055] The cabin blower compressor 52, driven by the low pressure spool of the gas turbine engine, compresses air collected by the scoop and delivered to the compressor via the duct system (not shown). Before and after compression the air is conditioned by the variable inlet guide vanes 60 and variable outlet guide vanes 62 respectively, the orientation of which are controlled by the EEC 66. Once compressed the air is delivered by the duct system for regulated use in the cabin of the aircraft via the air conditioning outlets. The rate at which the cabin blower compressor 52 is driven is controlled via the throttling functionality of the valve assembly 64 under the control of the EEC 66 which responds to demand for cabin air and pressurisation provided by the aircraft control system 68.

[0056] When it is desired for the cabin blower compressor 52 to perform as a turbine and rotate the low and high pressure spools of the gas turbine engine for engine start (ground or in-flight), the EEC 66 actuates the valve assembly 64 to adopt its second position. The EEC 66 further actuates the starter air shut-off valve assembly (not shown) so as it is in its second condition and actuates the clutched linkage to couple the accessory gearbox 32 and high pressure spool.

[0057] In the engine start configuration the cabin blower compressor 52 drives the low and high pressure spools of the gas turbine engine. This drive is delivered by the closed circuit hydrostatic transmission described above with reference to FIG. 2. Specifically an external source of gas (typically air) is supplied to the cabin blower compressor 52 via the starter conduit (not shown), causing it to perform as a turbine and rotate in an opposite sense by comparison with its rotational direction when it is operating in the cabin blower configuration. Conditioning of the externally sourced gas before and after its interaction with the cabin blower compressor 52 is performed by the variable outlet guide vanes 62 and variable inlet guide vanes 60 respectively under the control of the EEC 66. The rotation of the cabin blower compressor 52 delivers drive to the epicyclic gearbox 54. The epicyclic gearbox 54 in turn delivers drive to the first hydraulic device 38 causing it to perform as a hydraulic pump. Pumped by the first hydraulic device 38, hydraulic fluid leaves the first port 44, passes through the valve assembly 64 and enters the inlet port 48 of the second hydraulic device 40. Thereafter the hydraulic fluid leaves the second hydraulic device 40 via its outlet 50, passes through the valve assembly 64 and returns to the first hydraulic device 38 via second port 46, before recirculating again. As the hydraulic fluid passes through the second hydraulic device 40 it causes it to perform as a hydraulic motor and to drive the accessory gearbox 32, which in turn drives the low and high pressure spool of the gas turbine engine.

[0058] With the low and high pressure spools driven by the cabin blower compressor, sufficient airflow may be provided to a combustor of the gas turbine engine for engine light-up. In order to improve conditions for engine start, the valve assembly 64 may be used to adjust the rate of hydraulic fluid flow in the hydraulic circuit 36 and thereby the rate of rotation of the spools.

[0059] Regardless of whether the hydraulic circuit 36 is operating in the cabin blower or engine start configurations, the accumulator 70 operates to reduce fluctuations in hydraulic fluid pressure. Similarly the heat exchanger 72 operates to maintain the hydraulic fluid temperature within desired limits regardless of system operating configuration.

[0060] For simplicity, with respect to the embodiment described above, the engine start configuration is discussed in such a way as to principally contemplate a routine engine start (e.g. ground start using a source of external air as might be provided by a suitable compressed air rig). Nonetheless it will be appreciated that the source of external air need not be so limited. Further that in-flight windmill start may also be performed or at least assisted by operating the system in the engine start configuration. It may be for example that in some embodiments the source of external air is provided by a bleed from another running engine and/or an auxiliary power unit of the aircraft and/or another aircraft air system.

[0061] It is further noted that whilst the embodiment above describes only a single aircraft cabin blower system, one or more additional such systems may also be provided, and their hydraulic circuits may be selectively or otherwise linked. Additionally or alternatively the hydraulic circuit of the aircraft cabin blower system may be selectively or otherwise linked to a broader hydraulic system of the aircraft used for operation of aircraft systems and components. Such linking of systems may allow for enhanced redundancy in terms of cabin blower and/or aircraft hydraulic component operation in the event of one or more engine failures (i.e. an aircraft cabin blower system associated with one engine may be used to provide at least partial operation of another such system and/or a broader aircraft hydraulic system). Additionally such a system may provide enhanced engine start functionality (e.g. using an aircraft cabin blower system associated with one engine to drive one or more shafts of another during an in-flight engine start procedure). Additional components to those described with respect to the embodiment of FIG. 2 may be provided in order to facilitate and control such interlinking of systems. Such components may include additional interlinking and/or bypass conduits which may be valve controlled.

[0062] It will be understood that the invention is not limited to the embodiment above-described and various modifications and improvements can be made without departing from the concepts described herein. By way of specific example the epicyclic gearbox could be replaced with a Continuously variable transmission or a sequential shifting gearbox. Except where mutually exclusive, any of the features may be employed separately or in combination with any other features and the disclosure extends to and includes all combinations and sub-combinations of one or more features described herein.