Patent Description:
Pumping systems are used in aircraft to pump a variety of fluids including oils and fuel. Such pumping systems may be mechanically driven or electrically driven.

Mechanical pumping systems may have pumping pressures and flow rates constrained by the mechanical drive input conditions from an external system, such as an engine of the aircraft. It is not possible to turn the pump any faster than the engine is driving it, without accelerating the engine, and this limits the pressures that can be generated and the flow rates that can be passed through the system. The wider engine systems must be designed cognisant of these constraints.

Electric pumping systems are prone to pumping failures due to electrical drive system and coil arrangement failures. Additionally, to drive an accessory such as a pumping element from an engine of an aircraft fully electrically, that electrical power first has to be generated from chemical energy in the fuel which undergoes conversion to mechanical shaft energy, to then go through an energy conversion to electrical energy, to then go through a further energy conversion to mechanical energy to turn the pumping element at the desired speed. Every energy conversion involves efficiency losses. It would be beneficial to reduce the number of energy conversions, and to reduce the magnitude of those energy conversions needed in the system.

European Patent Application Publication <CIT> relates to an aircraft cabin blower system. The system comprises a cabin blower include a compressor configured to provide air to a cabin of the aircraft; a variable drive system configured to drive the compressor and including an electric variator and a summing gearbox; and a main transmission. When operating in a blower mode, it receives mechanical power from a gas turbine engine and inputs mechanical power to the summing gearbox in a forward direction. In a start mode, it receives mechanical power from the summing gearbox and inputs mechanical power to the gas turbine engine. The system further includes a one-way rotation device to permit free rotation of the main transmission in the forward direction and to prevent rotation of the main transmission in a reverse direction.

United States Patent Application Publication <CIT> relates to a bowed rotor prevention system for turbomachinery.

According to a first aspect, there is provided a blower system according to appended claim <NUM>. Such a blower system for supplying air to an aircraft system, comprises:
an air compressor for compressing air for delivery to an aircraft system; and a transmission having an input mechanically couplable with a gas turbine engine spool and an output mechanically coupled with the air compressor. The transmission comprises a variable speed pumping system comprising: a first electrical machine comprising an electrical machine rotor shaft mechanically couplable to a shaft of an engine of the aircraft and electrical machine stator coils, the first electrical machine being a motor-generator; an electric pump motor-generator, the electric pump motor-generator comprising an electric pump rotor shaft mechanically connected to the electrical machine rotor shaft via a one way drive arrangement and electric pump stator coils; wherein the electric pump rotor shaft is mechanically connected to a fluid pumping system.

The fluid pumping system may be suitable to pump any suitable fluid, which may incompressible (e.g. a liquid) or compressible (e.g. a gas), such as, for example, fuel, hydraulic fluids, oil or coolants.

The variable speed pumping system may be connected to a power management system (i.e. an electrical power system). The power management system may be operable to transfer electrical power to or receive electrical power from the stator coils of the first electrical machine and the stator coils of the electric pump motor-generator. The power management system may include a storage device such as a battery or a capacitor configured to store electrical power.

The one-way drive arrangement may be configured such that the electrical machine rotor shaft and the electric pump rotor shaft can rotate relative to each other in only one direction. The one-way drive arrangement may be configured such that the electrical machine rotor shaft can only drive the electric pump rotor shaft in one direction, whilst providing minimal resistance to relative rotation in the other direction.

Any suitable one-way drive arrangement may be used such as, for example, a sprag clutch arrangement or a ratchet and pawl arrangement.

The fluid pumping system may comprise any suitable type of pump, for example, a gear pump, a vane pump, a gerotor pump, a centrifugal pump, a piston pump or a compressor (e.g. a centrifugal compressor, an axi-centrifugal compressor or a scroll compressor).

The electric pump rotor shaft may be mechanically connected to a fluid pumping system via a geared arrangement. For example, the electric pump rotor shaft may comprise a gear wheel arranged to interengage with a further gear wheel. The gear wheel of the electric pump rotor shaft and further gear wheel may comprise a plurality of teeth configured to interengage such that rotation of the gear wheel may cause rotation of the further gear wheel. Any suitable number of further gear wheels may be mechanically connected to the gear wheel and/or any further gear wheels present.

The gear wheel of the electric pump rotor shaft and/or the further gear wheel may be mechanically connected to a remote fluid pumping system such that the gear wheel and/or further gear wheel may provide mechanical power to the remote pumping system.

The gear wheel of the electric pump rotor shaft and/or the further gear wheel may directly form part of a fluid pumping system such as a positive displacement gear pump assembly.

The first electrical machine may be any suitable type of electrical machine. Likewise, the electric pump motor-generator may be any suitable type of electrical machine and may the same type or a different of electrical machine to the first electrical machine. In one specific embodiment, one or both of the electrical machines are permanent magnet electrical machines with stator coils arranged to at least partially surround a portion of the rotor shaft. However other types and configurations are possible, including outrunner radial flux machines, axial flux machines, transverse flux machines, switched reluctance machine and wound-field machines, and other machine types and configurations which will occur to those skilled in the art.

In a first mode, the electrical machine rotor shaft may be mechanically rotated by power received from the engine. The electrical machine rotor shaft may be mechanically connected to the engine through an accessory gearbox, for example. Rotation of the electrical machine rotor shaft may drive rotation of the electric pump rotor shaft via the one-way drive arrangement.

Rotation of the electrical machine rotor shaft by the engine may allow for electrical power generation through the electrical machine stator coils. In this way, in the first mode, the first electrical machine may be configured to operate as a generator. The electrical power generated by the first electrical machine may then be used by other electrically connected systems. The electrical power generated by the first electrical machine may be transmitted to the power management system.

Rotation of the electric pump rotor shaft by the electrical machine rotor shaft via the one-way drive arrangement may allow for electrical power generation through the electric pump stator coils. In this way, in the first mode, the electric pump motor-generator may be configured to operate as a generator. The electrical power generated by the electric pump motor-generator may then be used by other electrically connected systems. The electrical power generated by the electric pump motor-generator may be transmitted to the power management system.

Rotation of the electric pump rotor shaft by the electrical machine rotor shaft via the one-way drive arrangement may drive the fluid pumping system. In the first mode, the speed of the electric pump rotor shaft may be dictated by the speed of the electrical machine rotor shaft.

As such, in the first mode, the first electric machine and electric pump motor-generator may both be operated as generators. In the first mode, both the electric machine rotor shaft and electric pump rotor shaft may be mechanically driven.

In some circumstances, it may be beneficial for the electric pump rotor shaft to turn faster than the electrical machine rotor shaft.

In a second mode, the electrical machine rotor shaft may be mechanically rotated by power received from the engine.

Rotation of the electrical machine rotor shaft by the engine may allow for electrical power generation through the electrical machine stator coils. In this way, in the second mode, the first electrical machine may be configured to operate as a generator. The electrical power generated by the first electrical machine may then be used by other electrically connected systems. The electrical power generated by the first electrical machine may be transmitted to the or a power management system.

In the second mode, the electric pump motor-generator may be configured to operate as a motor. Electrical power from the power management system may be transmitted to the electric pump stator coils, in order to operate the electric pump motor-generator as a motor and not as a generator.

When operating as a motor, the electric pump motor-generator may be operable to cause the electric pump rotor shaft to overrun the first electric machine rotor shaft and therefore rotate faster than the first electric machine rotor shaft. In the second mode, the electric pump rotor shaft may be rotated electrically and may drive the fluid pumping system. As such, the electric pump rotor shaft may rotate at a speed that is not limited by the speed of rotation of the electrical machine rotor shaft.

The electric pump motor-generator, when run as a motor, may be configured such that the electric pump motor-generator is operable to electrically rotate the electric pump rotor shaft at variable speeds. In this way, the fluid pumping system may be driven to meet demand where the electrical machine rotor shaft is not rotating fast enough to meet said demand.

The variable speed pumping system may be operable to switch between the first mode and the second mode. Switching between the first mode and the second mode may be dependent on a variety of factors such as, for example, engine speeds and fluid pumping system demands.

The second mode may be used during, for example, starting the engine. During a starting mode of the engine, the first electrical machine may be operated as a generator. During a starting mode of the engine, the electrical machine rotor shaft may be rotating relatively slowly, but may be generating a lot of heat, because it may not be designed to be efficient in these operating conditions. In the second mode, the electric pump motor-generator may be operated as a motor to overrun the one-way drive arrangement to the desired rotation speed, which may provide the pumping of sufficient pumping fluid (e.g. oil) around the circuit to provide adequate cooling to the coils and rotors of the first electrical machine and/or the electric pump motor-generator.

The variable speed pumping system may be configured to switch from the first mode to the second mode at any suitable time during operation. The variable speed pumping system may be configured to switch from the first mode to the second mode when additional pumping flow rates or pumping pressures are required. Such conditions may include when greater flow rates of cooling fluids, such as oil, are required.

By providing a means for increasing the flow of cooling fluids the rates of temperature change experienced by components, such as components in one or more oil cooling circuits, may be reduced.

In a third mode, the electrical machine rotor shaft may be driven electrically. The electric motor stator coils may receive power from the or a power management system which may cause the first electrical machine to operate as a motor. The electrical machine rotor shaft may be used as the prime mover to turn the accessory gearbox.

The third mode may be used at engine start up. In the third mode, the first electrical machine operating as a motor may only rotate the electrical machine rotor shaft relatively slowly. This in turn may only mechanically rotate the electric pump rotor shaft relatively slowly via the one-way drive arrangement.

As such, in the third mode, the electric pump motor-generator may be configured to also operate as a motor. Electrical power from the or a power management system may be transmitted to the electric pump stator coils in order to operate the electric pump motor-generator as a motor.

When operating as a motor, the electric pump motor-generator may be operable to cause the electric pump rotor shaft to overrun the first electric machine rotor shaft and therefore rotate faster than the first electric machine rotor shaft. In the third mode, the electric pump rotor shaft may be rotated electrically and may drive the fluid pumping system. As such, the electric pump rotor shaft may rotate at a speed that is not limited by the speed of rotation of the electrical machine rotor shaft.

The electric pump motor-generator, when run as a motor, may be configured such that the electric pump motor-generator is operable to electrically rotate the electric pump at variable speeds. In this way, the fluid pumping system may be driven to meet demand where the electrical machine rotor shaft is not rotating fast enough to meet said demand.

The variable speed pumping system may be operable to switch between the first mode, the second mode and/or the third mode. Switching between the first mode, the second mode and/or the third mode may be dependent on a variety of factors such as, for example, engine speeds and fluid pumping system demands.

In the third mode, the first electric machine and the electric pump motor-generator may both be configured to operate as motors and both the electric machine rotor shaft and the electric pump rotor shaft may be electrically driven.

The third mode may be used during, for example, barring of the engine. During barring of the engine, the first electrical machine may be operated as a motor. When operated as a motor the electrical machine rotor shaft may be rotating relatively slowly but may be generating a lot of heat, because it may not be designed to be efficient in these operating conditions. In the third mode, the electric pump motor-generator may be operated as a motor to overrun the one-way drive arrangement to the desired rotation speed, which may provide the pumping of sufficient pumping fluid (e.g. oil) around the circuit to provide adequate cooling to the coils and rotors of the first electrical machine and/or the electric pump motor-generator.

Upon loss of electrical power to the electric pump motor-generator the pump may remain operational through its mechanical drive mechanism.

The blower system is configured to supply air to an aircraft system for one or more pressurisation purposes. The pressurisation purposes may include, for example, wing anti-icing, fuel tank inerting, cargo bay smoke eradication and/or aircraft cabin pressurisation. If the blower system is configured to supply air for aircraft cabin pressurisation, it may be referred to as a cabin blower system.

The transmission may comprise a continuously variable transmission (CVT).

The transmission is configured to receive mechanical power from the spool of the gas turbine engine in the form of a first transmission input.

The blower system may comprise: an electrical circuit comprising the first electrical machine; a second electrical machine; and a power management system, wherein, when operating in a blower mode, the first electrical machine is configured to receive mechanical power from the spool of the gas turbine engine and act as a generator to provide electrical power to the power management system, and the second electrical machine is configured to act as a motor providing mechanical power to the transmission in the form of a second transmission input, the second electrical machine being driven by electrical power from the power management system.

An output of the transmission is configured to drive the blower compressor when operating in the blower mode, a speed of the output of the transmission being determined by a function of a speed of the first and second transmission inputs.

The blower system may further have an engine starting mode. In the engine starting mode the transmission may be configured to drive rotation of the spool of the gas turbine engine via the first transmission input. In this case the transmission may be driven to rotate by the blower compressor, which may be operated as an air turbine using a supply of pressurised air (e.g. from ground equipment or an auxiliary power unit as is known in the art). Additionally or alternatively, the first electrical machine may be configured to operate as a motor to drive rotation of the spool of the gas turbine engine.

The blower system may further comprise a disconnect arrangement for selectively disconnecting the blower compressor from the spool of the gas turbine engine. The disconnect arrangement, or one or more additional disconnect arrangements, may additionally or alternatively connect the transmission and/or variator from the gas turbine engine. Providing a disconnect arrangement, for example a clutch arrangement or an electromechanical disconnect arrangement, allows isolation of blower system components in case of faults or operational issues.

The transmission may comprise a summing gearbox, more specifically a summing epicyclic gearbox.

According to a second aspect there is provided a gas turbine engine according to appended claim <NUM>. Such a gas turbine engine comprises a blower system according to the first aspect.

According to a third aspect there is provided an aircraft according to appended claim <NUM>. Such an aircraft comprises a blower system according to the first aspect, or a gas turbine engine according to a second aspect.

As noted elsewhere herein, the present disclosure relates to a gas turbine engine. Such a gas turbine engine comprises an engine core comprising a turbine, a combustor, a compressor, and a core shaft connecting the turbine to the compressor.

The person skilled in the art will appreciate that except where mutually exclusive, a feature described in relation to any one of the above aspects may be applied mutatis mutandis to any other aspect. However, the invention and the corresponding scope of protection is soley defined by the appended claims.

Examples are described below with reference to the accompanying drawings, in which:.

The engine core <NUM> comprises, in axial flow series, a low-pressure compressor <NUM>, a high-pressure compressor <NUM>, combustion equipment <NUM>, a high-pressure turbine <NUM>, a low-pressure turbine <NUM> and a core exhaust nozzle <NUM>. The fan <NUM> is attached to and driven by the low-pressure turbine <NUM> via a shaft <NUM> and an epicyclic gearbox <NUM>.

In use, the core airflow A is accelerated and compressed by the low-pressure compressor <NUM> and directed into the high-pressure compressor <NUM> where further compression takes place. The compressed air exhausted from the high-pressure compressor <NUM> is directed into the combustion equipment <NUM> where it is mixed with fuel and the mixture is combusted. The resultant hot combustion products then expand through, and thereby drive, the high-pressure and low-pressure turbines <NUM>, <NUM> before being exhausted through the nozzle <NUM> to provide some propulsive thrust. The high-pressure turbine <NUM> drives the high-pressure compressor <NUM> by a suitable interconnecting shaft <NUM>.

The low-pressure turbine <NUM> (see <FIG>) drives the shaft <NUM>, which is coupled to a sun wheel, or sun gear, <NUM> of the epicyclic gear arrangement <NUM>.

Note that the terms "low-pressure turbine" and "low-pressure compressor" as used herein may be taken to mean the lowest pressure turbine stages and lowest pressure compressor stages (i.e. not including the fan <NUM>) respectively and/or the turbine and compressor stages that are connected together by the interconnecting shaft <NUM> with the lowest rotational speed in the engine (i.e. not including the gearbox output shaft that drives the fan <NUM>). In some literature, the "low-pressure turbine" and "low-pressure compressor" referred to herein may alternatively be known as the "intermediate pressure turbine" and "intermediate pressure compressor".

Other gas turbine engines to which the present disclosure may be applied may have alternative configurations. For example, such engines may have an alternative number of compressors and/or turbines and/or an alternative number of interconnecting shafts. By way of further example, the gas turbine engine shown in <FIG> has a split flow nozzle <NUM>, <NUM> meaning that the flow through the bypass duct <NUM> has its own nozzle <NUM> that is separate to and radially outside the core engine nozzle <NUM>. However, this is not limiting, and any aspect of the present disclosure may also apply to engines in which the flow through the bypass duct <NUM> and the flow through the core <NUM> are mixed, or combined, before (or upstream of) a single nozzle, which may be referred to as a mixed flow nozzle. One or both nozzles (whether mixed or split flow) may have a fixed or variable area. Whilst the described example relates to a turbofan engine, the disclosure may apply, for example, to any type of gas turbine engine, such as an open rotor (in which the fan stage is not surrounded by a nacelle) or turboprop engine, for example. In some arrangements, the gas turbine engine <NUM> may not comprise a gearbox <NUM>.

Referring now to <FIG>, an example of an aircraft blower system <NUM> is shown in schematic form. The blower system <NUM> is configured to supply air to one or more aircraft systems for one or more pressurisation purposes. The pressurisation purposes may include, for example, wing anti-icing, fuel tank inerting, cargo bay smoke eradication and/or aircraft cabin pressurisation. If the blower system is configured to supply air for aircraft cabin pressurisation, it may be referred to as a cabin blower system. In the following description the blower system <NUM> will be referred to as a cabin blower system, though it should be understood this is not intended to be limiting.

The cabin blower system <NUM> includes a cabin blower compressor <NUM> and a power source, which in this specific example is in the form of an intermediate-pressure shaft <NUM> of an intermediate-pressure compressor <NUM> of a gas turbine engine. The intermediate-pressure compressor <NUM> powers an accessory gearbox <NUM> of the gas turbine engine, which, in turn, provides power to a transmission <NUM> of the cabin blower system <NUM>. The accessory gearbox <NUM> may however be powered by the low-pressure shaft, intermediate-pressure shaft, or the high-pressure shaft of any gas turbine engine.

The transmission <NUM> comprises a summing epicyclic gearbox <NUM> with two inputs. A first transmission input <NUM> of the epicyclic gearbox <NUM> is provided mechanically from the accessory gearbox <NUM> to a part of the epicyclic gearbox <NUM>. The accessory gearbox <NUM> also provides mechanical power to a first electrical machine <NUM> which, in a blower mode of the cabin blower system <NUM>, operates as a generator to convert the mechanical power received from the accessory gearbox <NUM> to electrical power. A second transmission input <NUM> of the epicyclic gearbox <NUM> is provided from a second electrical machine <NUM> which, in the blower mode of the cabin blower system <NUM>, operates as a motor to convert electrical power to mechanical power, which is provided to the epicyclic gearbox <NUM>.

A power management system <NUM> interconnects the first electrical machine <NUM> and second electrical machine <NUM>. In the blower mode being described here, the power management system <NUM> receives electrical power from the first electrical machine <NUM> and sends said power to the second electrical machine <NUM>. Thus, despite in this embodiment both the first electrical machine <NUM> and the second electrical machine <NUM> being 80kW motor-generators, the second electrical machine <NUM> can be driven as a motor at a different speed from the speed of the first electrical machine <NUM> acting as a generator at that time. Moreover, the power management system <NUM> can provide a continuously-variable difference between the power received from the first electrical machine <NUM> and the power output to the second electrical machine <NUM>. It should be appreciated that the power outputs of the electrical machines can differ from 80kW and will depend on the application requirements. Furthermore, the power outputs of the first and second electrical machines <NUM>, <NUM> can be different.

The power management system can include electrical storage, in the form for example of one or more batteries, capacitors or similar, that enables the power management system to output more power than is being received by the power management system at any moment.

The epicyclic gearbox <NUM>, as previously mentioned, is a summing epicyclic gearbox configured to have an output that is a function of the speeds of the first input <NUM> and the second input <NUM>. In the present embodiment, the first input <NUM> is always positive, resulting in operation of the compressor <NUM>. The second input <NUM>, which can be rotated either positively or negatively by the second electrical machine <NUM>, acts to provide either a positive or negative input to the epicyclic gearbox <NUM>. Thus, the output of the epicyclic gearbox <NUM> that feeds to the compressor <NUM> can be adjusted continuously by the operation of the second electrical machine <NUM> such that the output is greater or less than that which would be provided were the only input to the epicyclic gearbox <NUM> to be the first input <NUM>. The function of the epicyclic gearbox <NUM> may result in the output being the sum of the first and second inputs <NUM>, <NUM> or may otherwise be related to the difference by way of a ratio provided by the epicyclic gearbox <NUM>, for example.

The operation of a summing epicyclic gearbox <NUM> will be known to the person skilled in the art and therefore alternative implementations will be apparent. Moreover, other forms of summing gearbox may also be used, in addition to or as a replacement for the epicyclic gearbox <NUM> depicted.

In addition to operation in the blower mode, the cabin blower system <NUM> can also be operated in a starter mode in order to provide mechanical input to the gas turbine engine to facilitate a start operation of the gas turbine engine. The cabin blower compressor <NUM> can operate in reverse as an expander to provide drive to the epicyclic gearbox <NUM> from a supply of compressed air.

The second electrical machine <NUM> can then be held still such that the transmission <NUM> transmits the mechanical power from the compressor <NUM> to the accessory gearbox <NUM>. The accessory gearbox <NUM> will in turn cause the intermediate-pressure compressor <NUM> to rotate, which facilitates starting of the gas turbine engine. The remaining steps required for the successful ignition of a gas turbine engine will be known to the person skilled in the art and are therefore not discussed in the present disclosure.

In addition to the input from the compressor <NUM>, the first electrical machine <NUM>, which operated in the blower mode as a generator, can be powered by the power management system <NUM> such that the first electrical machine <NUM> acts as a motor, in the starter mode. The mechanical power generated by the first electrical machine <NUM> can therefore be added to that provided by the compressor <NUM>, both the compressor <NUM> and the first electrical machine <NUM> causing rotation of the accessory gearbox <NUM> and thus intermediate-pressure compressor <NUM>. As such, the present embodiment both provides a variable speed compressor <NUM> and an electrically-assisted starting operation for a gas turbine engine.

The first electrical machine <NUM> forms part of a variable speed pumping system <NUM>. The variable speed pumping machine <NUM> comprises the first electrical machine <NUM>, where the first electrical machine <NUM> comprises an electrical machine rotor shaft <NUM> mechanically connected to the gas turbine engine <NUM> of the aircraft via the accessory gearbox <NUM>. Electrical machine stator coils <NUM> are, in this example, arranged to at least partially surround a portion of the electrical machine rotor shaft <NUM> but will be understood this may not be the case in other electrical machine types and configurations within the scope of the present disclosure.

The electrical machine rotor shaft <NUM> and electrical machine stator coils <NUM> are configured such that rotation of the electrical machine rotor shaft using mechanical power from the engine allows for electrical power generation through the electrical machine stator coils <NUM>. The electrical machine rotor shaft <NUM> and electrical machine stator coils <NUM> are also configured such that passing an electric current through the electrical machine stator coils <NUM> can cause rotation of the electrical machine rotor shaft <NUM>.

The variable speed pumping machine <NUM> further comprises an electric pump moto-generator <NUM>. The electric pump motor-generator <NUM> comprises an electric pump rotor shaft <NUM> mechanically connected to the electrical machine rotor shaft <NUM> via a one way drive arrangement <NUM>. Electric pump stator coils <NUM> are, in this example, arranged to at least partially surround a portion of the electric pump rotor shaft <NUM> but will be understood this may not be the case in other electrical machine types and configurations within the scope of the present disclosure.

The electric pump rotor shaft <NUM> and electric pump stator coils <NUM> are configured such that rotation of the electrical machine rotor shaft using mechanical power from the electrical machine rotor shaft <NUM> allows for electrical power generation through the electric pump stator coils <NUM>. The electric pump rotor shaft <NUM> and electric pump stator coils <NUM> are also configured such that passing an electric current through the electric pump stator coils <NUM> can cause rotation of the electric pump rotor shaft <NUM>.

The electric pump rotor shaft <NUM> is mechanically connected to a fluid pumping system <NUM>. In some embodiments, the fluid pumping system <NUM> is configured to pump fuel, hydraulic fluids, oil or coolants. The fluid pumping system <NUM> may be configured to pump any suitable fluid.

In <FIG> and <FIG>, an embodiment where the fluid pumping system <NUM> comprises a geared pumping system <NUM> is shown. In other embodiments, the fluid pumping system <NUM> may comprise any suitable type of pump, for example, a gear pump, a vane pump, a gerotor pump, a centrifugal pump, or a piston pump.

In the embodiment shown in <FIG> and <FIG>, the electric pump rotor shaft <NUM> is mechanically connected to the fluid pumping system <NUM> via a geared arrangement. The electric pump rotor shaft <NUM> comprises a driver gear wheel <NUM> mechanically connected to a driven gear wheel <NUM>. The driver gear wheel <NUM> and driven gear wheel <NUM> comprise cooperating gear teeth arranged to mesh together such that rotation of the driver gear wheel <NUM> causes rotation of the driven gear wheel <NUM>. In this way, driver gear wheel teeth <NUM> are arranged to mesh together with driven gear wheel teeth <NUM> such that rotation of the driver gear wheel <NUM> causes rotation of the driven gear wheel <NUM>.

The driver gear wheel <NUM> and driven gear wheel <NUM> may form part of a positive displacement gear pump assembly. The driven gear wheel <NUM> may be mechanically connected to a remote pumping system such that the driven gear wheel <NUM> is operable to provide mechanical power to the remote pumping system. As such, the driver gear wheel <NUM> and/or driven gear wheel <NUM> may directly form part of a pumping system or may be operable to provide mechanical power to a remote pumping system. The one-way drive arrangement <NUM> is disposed between the electrical machine rotor shaft <NUM> and the driver gear wheel <NUM>.

The one-way drive arrangement <NUM> is configured such that the electrical machine rotor shaft <NUM> and the electric pump rotor shaft <NUM> can rotate relative to each other in only one relative direction.

In <FIG> and <FIG>, a sprag clutch arrangement <NUM> is shown as an example of a one-way drive arrangement <NUM>. In other embodiments, any suitable one-way drive arrangement may be used, for example, a ratchet and pawl arrangement. In this way, the one-way drive arrangement <NUM> is configured such that the electrical machine rotor shaft <NUM> can only drive the electric pump rotor shaft <NUM> in one direction.

<FIG> shows a different example embodiment of the variable speed pumping system <NUM>.

In the example shown in <FIG>, the electric pump rotor shaft <NUM> and the electric pump stator coils <NUM> are disposed substantially to a side of the first electrical machine <NUM>.

In the example shown in <FIG>, the electric pump rotor shaft <NUM> and the electric pump stator coils <NUM> are arranged to extend around the circumference of the electrical machine rotor shaft <NUM>.

In both <FIG> and <FIG>, the electrical machine rotor shaft <NUM> and the electric pump rotor shaft <NUM> are configured to rotate concentrically.

In use, the variable speed pumping machine <NUM> is configured to operate in at least three modes including; a first mode, a second mode and a third mode.

In a first mode, the electrical machine rotor shaft <NUM> is rotated using mechanical power received from the gas turbine engine <NUM>. The electrical machine rotor shaft <NUM> is mechanically connected to the gas turbine engine <NUM> through the accessory gearbox <NUM>. In other embodiments, the electrical machine rotor shaft is mechanically connected to the gas turbine engine <NUM> but not through the accessory gearbox <NUM>. In other embodiments, the electrical machine rotor shaft <NUM> is configured to receive mechanical power from the gas turbine engine <NUM> via any suitable arrangement.

Rotation of the electrical machine rotor shaft <NUM>, using mechanical power from the gas turbine engine <NUM>, mechanically drives rotation of the electric pump rotor shaft <NUM> via the one-way drive arrangement <NUM>. Upon rotation of the electrical machine rotor shaft <NUM> the one-way drive arrangement <NUM> engages with the electric pump rotor shaft <NUM> such that the electric pump rotor shaft <NUM> rotates at the same speed as the electrical machine rotor shaft <NUM>. As such, in the first mode the electrical machine rotor shaft <NUM> and the electric pump rotor shaft <NUM> are both driven by mechanical power from the gas turbine engine <NUM>.

Rotation of the electrical machine rotor shaft <NUM>, using mechanical power from the gas turbine engine <NUM>, allows for electrical power generation through the electrical machine stator coils <NUM>. In this way, in the first mode, the first electrical machine <NUM> is configured to operate as a generator. The electrical power generated by the first electrical machine <NUM> is transmitted to the power management system <NUM>. In some embodiments, electrical power generated by the first electrical machine <NUM> may be transferred to any other suitable power management system or electrical energy storage device.

Rotation of the electric pump rotor shaft <NUM>, driven mechanically by the electrical machine rotor shaft <NUM> via the one-way drive arrangement <NUM>, allows for electrical power generation through the electric pump stator coils <NUM> in the first mode. In this way, in the first mode, the electric pump motor-generator <NUM> is configured to operate as a generator. The electrical power generated by the electric pump motor-generator <NUM> is transmitted to the power management system <NUM>. In some embodiments, electrical power generated by the electric pump motor-generator <NUM> may be transferred to any other suitable power management system or electrical energy storage device.

In the first mode, electrical power generated by the first electrical machine <NUM> and the electric pump motor-generator <NUM> and transmitted to the power management system <NUM> may be used to electrically power the second electrical machine <NUM> when present.

Rotation of the electric pump rotor shaft <NUM> by the electrical machine rotor shaft <NUM> via the one-way drive arrangement drives a fluid pumping system <NUM>. In the first mode, the speed of the electric pump rotor shaft <NUM> is dictated by the speed of the electrical machine rotor shaft <NUM>. As such, in the first mode, the first electric machine <NUM> and the electric pump motor-generator <NUM> are both be operated as generators.

In a second mode, the electrical machine rotor shaft <NUM> may be mechanically rotated by power received from the gas turbine engine <NUM> in the same way as in the first mode.

Similarly to the first mode, rotation of the electrical machine rotor shaft <NUM> driven by the engine <NUM> allow for electrical power generation through the electrical machine stator coils <NUM>. In this way, in the second mode, the first electrical machine <NUM> is configured to operate as a generator. The electrical power generated by the first electrical machine <NUM> is transmitted to the power management system <NUM>.

In the second mode, the electric pump motor-generator <NUM> is operated as a motor. Electrical power from the power management system <NUM> is transmitted to the electric pump stator coils <NUM> in order to operate the electric pump motor-generator <NUM> as a motor and not a generator.

When operating as a motor in the second mode, the electric pump motor-generator <NUM> is operable to cause the electric pump rotor shaft <NUM> to overrun the first electric machine rotor shaft <NUM> and therefore rotate faster than the first electric machine rotor shaft <NUM>. In this way, in the second mode the electric pump rotor shaft <NUM> is rotated and drives the fluid pumping system <NUM>, using electrical power. As such, the electric pump rotor shaft <NUM> is operable to rotate at a speed that is not limited by the speed of rotation of the electrical machine rotor shaft <NUM>. The fluid pumping system <NUM> may therefore be driven using electrical power to meet demand where the electrical machine rotor shaft <NUM> is not rotating fast enough to meet said demand.

In a third mode, the electrical machine rotor shaft <NUM> is driven electrically. The third mode may be used during starting or barring modes of the gas turbine engine <NUM>. The electric motor stator coils <NUM> receive power from the power management system <NUM> which causes the first electrical machine <NUM> to operate as a motor. The electrical machine rotor shaft <NUM>, in the third mode, may be used as the prime mover to turn the accessory gearbox <NUM>.

In the third mode, the electric pump motor-generator <NUM> is configured to also operate as a motor. Electrical power from the power management system <NUM> is transmitted to the electric pump stator coils <NUM> in order to operate the electric pump motor-generator <NUM> as a motor.

When operating as a motor, the electric pump motor-generator <NUM> is operable to cause the electric pump rotor shaft <NUM> to overrun the first electric machine rotor shaft <NUM>, similarly to the second mode, and therefore rotate faster than the first electric machine rotor shaft <NUM>. In the third mode, the electric pump rotor shaft <NUM> is rotated using electrical power from the power management system <NUM> drives the fluid pumping system <NUM> at a speed that is not limited by the speed of rotation of the electrical machine rotor shaft <NUM>.

In the third mode, the first electric machine <NUM> and electric pump motor-generator <NUM> are both configured to operate as motors and both the electric machine rotor shaft <NUM> and electric pump rotor shaft <NUM> are electrically driven.

The variable speed pumping system <NUM> is operable to switch between the first mode, the second mode and/or the third mode. The variable speed pumping system <NUM> may be controlled by an electronic controller or the like. The electronic controller may form part of the variable speed pumping system <NUM> or may be part of a wider aircraft system.

<FIG> shows schematically an aircraft <NUM>. The aircraft <NUM> has a fuselage <NUM> with a cabin <NUM> therein. A first wing <NUM> and a second wing <NUM> extend away from the fuselage <NUM> in opposite directions. A first gas turbine engine <NUM> is connected to the first wing <NUM>. A second gas turbine engine <NUM> is connected to the second wing <NUM>. The first gas turbine engine <NUM> and/or the second gas turbine engine <NUM> are any gas turbine engine for an aircraft. For example, the first gas turbine engine <NUM> and/or the second gas turbine engine <NUM> may be similar to or the same as the gas turbine engine <NUM> disclosed herein.

A first variable speed pumping system 200a according to the present disclosure is associated with the first gas turbine engine <NUM>. A second variable speed pumping system 200b according to the present disclosure is associated with the second gas turbine engine <NUM>.

Claim 1:
A blower system (<NUM>) for supplying air to a system of an aircraft (<NUM>), the blower system (<NUM>) comprising:
an air compressor (<NUM>) for compressing air for delivery to the system of the aircraft; and
a transmission (<NUM>) having a first transmission input (<NUM>) mechanically couplable with a gas turbine engine spool (<NUM>, <NUM>) and an output mechanically coupled with the air compressor (<NUM>),
characterized in that the transmission (<NUM>) comprises a variable speed pumping system (<NUM>, 200a, 200b) for the aircraft (<NUM>), the variable speed pumping system (<NUM>, 200a, 200b) comprising:
a first electrical machine (<NUM>) comprising an electrical machine rotor shaft (<NUM>) mechanically couplable to the gas turbine engine spool (<NUM>, <NUM>) and electrical machine stator coils (<NUM>), the first electrical machine being a motor-generator; and
an electric pump motor-generator (<NUM>) comprising an electric pump rotor shaft (<NUM>) mechanically connected to the electrical machine rotor shaft (<NUM>) via a one way drive arrangement (<NUM>) and electric pump stator coils (<NUM>);
wherein the electric pump rotor shaft (<NUM>) is mechanically connected to a fluid pumping system (<NUM>).