Patent Description:
Thermoelectric generator systems are known to produce a voltage when in the presence of a thermal gradient. Placing thermoelectric generators in places with a high thermal gradient, such as on a compressor casing of a gas turbine engine, can result in losses, for example, in thrust.

Prior art systems are described in documents <CIT>, <CIT>, <CIT> and in <NPL>).

The present invention provides a thermoelectric generator system as set out in claim <NUM>, and a method of controlling a thermoelectric generator system as set out in claim <NUM>. Optional features are included in the dependent claims.

With reference to <FIG>, a gas turbine engine for an aircraft is generally indicated at <NUM>, having a principal and rotational axis <NUM>. The engine <NUM> comprises, in axial flow series, an air intake <NUM>, a propulsive fan <NUM>, a compressor stage comprising an intermediate pressure compressor <NUM>, a high-pressure compressor <NUM>, combustion equipment <NUM>, a high-pressure turbine <NUM>, an intermediate pressure turbine <NUM>, a low-pressure turbine <NUM> and an exhaust nozzle <NUM>. A nacelle <NUM> generally surrounds the engine <NUM> and defines both the intake <NUM> and the exhaust nozzle <NUM>.

The gas turbine engine <NUM> works in the conventional manner so that air entering the intake <NUM> is accelerated by the fan <NUM> to produce two air flows: a first air flow into the intermediate pressure compressor <NUM> and a second air flow which passes through a bypass duct <NUM> to provide propulsive thrust. The intermediate pressure compressor <NUM> compresses the air flow directed into it before delivering that air to 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 combusted. The resultant hot combustion products then expand through, and thereby drive the high, intermediate and low-pressure turbines <NUM>, <NUM>, <NUM> before being exhausted through the nozzle <NUM> to provide additional propulsive thrust. The high <NUM>, intermediate <NUM> and low <NUM> pressure turbines drive respectively the high pressure compressor <NUM>, intermediate pressure compressor <NUM> and fan <NUM>, each by suitable interconnecting shaft.

Other gas turbine engines to which the present invention 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.

<FIG> shows a schematic representation of the gas turbine engine <NUM> comprising a first example thermoelectric generator system <NUM> connected to the compressor stage via a bleed air line <NUM> which is diverted from the compressor stage of the gas turbine engine <NUM>.

In this example, the bleed air line <NUM> is bifurcated into two lines, with a first line <NUM> being configured to deliver compressed air to the thermoelectric generator system <NUM>, and a second line <NUM> being configured to receive compressed air from the thermoelectric generator system <NUM>. In some examples, the bleed air line may not bifurcate, and may simply be configured to deliver compressed air to the thermoelectric generator system without receiving the compressed air back again. In other examples, compressed air is delivered to the thermoelectric generator system <NUM> by other means, and the bleed air line may be configured to receive compressed air from the thermoelectric generator system. In yet other examples, the thermoelectric generator system may not receive or deliver air to the bleed air line, and may be completely independent from the bleed air diverted from the compressor stage.

The first example thermoelectric generator system <NUM> comprises a thermoelectric generator <NUM>, a vortex tube <NUM> and a radiator system <NUM> which may be disposed between the vortex tube <NUM> and the thermoelectric generator <NUM>.

The thermoelectric generator <NUM> generates a potential difference by a temperature gradient across the thermoelectric generator <NUM>. In this example, the thermoelectric generator <NUM> is a p/n type thermoelectric generator which comprises a plurality of p/n type thermoelectric modules. Each thermoelectric module may be able to produce approximately <NUM>-1W. The p/n type thermoelectric modules can be connected in series which enables the voltage output (and wattage) of the thermoelectric generator <NUM> to be increased by adding the wattages of each thermoelectric module connected in series.

In this example, the thermoelectric generator <NUM> is electrically coupled to electronic components to power the electronic components. In this example, the electronic components comprise a sensor <NUM>, and an energy storage component <NUM> such as a battery or capacitor, to store energy generated by the thermoelectric generator <NUM> that cannot be immediately consumed. In some examples, the thermoelectric generator <NUM> may not be connected to any components, but may be configured to be connected to such components. In other examples, the thermoelectric generator may be configured to be, or may be, coupled to a single electric component, or more than two electric components.

The sensor may include any of: an accelerometer, a temperature sensor, a pressure sensor, a location sensor, an orientation sensor, a humidity sensor, a vibration sensor, an air quality sensor and/or a gas sensor. The electronic component may additionally or alternatively include control electronics, data logging electronics and/or wireless communication electronics. The electronic components may require power in the order of mW up to approximately 10W. For example, a pressure sensor may require approximately 15mW of power, while a datalogger may require <NUM>-5W of power.

The vortex tube <NUM> comprises a flow input <NUM> which is configured to receive an input of compressed gas. In this example, the flow input <NUM> is fluidically connected to the first line <NUM> of the bleed air line <NUM>, such that it receives compressed gas from the compressor stage of the gas turbine engine <NUM>. The vortex tube <NUM> is configured to separate the compressed gas into a hot flow and a cold flow, with the hot flow and cold flow being hot and cold relative to one another. In other words, the cold flow has a lower temperature than the hot flow, and the hot flow has a higher temperature than the cold flow. The vortex tube <NUM> is configured to achieve this separation without additional energy input. The hot flow is discharged from a first output <NUM> of the vortex tube <NUM> and the cold flow is discharged from the second output <NUM> of the vortex tube <NUM>.

The radiator system <NUM> in this example comprises a first heat exchanger <NUM> and a second heat exchanger <NUM> which are disposed on opposing sides of the thermoelectric generator <NUM>. In this example, the cold flow is directed to the second heat exchanger <NUM> and the hot flow is directed to the first heat exchanger <NUM>. Since the thermoelectric generator <NUM> generates a potential difference and electric current by a temperature gradient across the thermoelectric generator <NUM>, by splitting compressed air into a hot flow and a cold flow with the vortex tube <NUM>, the thermal gradient across the thermoelectric generator <NUM> can be increased without requiring additional power input, thus increasing the power output of the thermoelectric generator <NUM>. In particular this allows for the thermoelectric generator to operate in an otherwise isothermal environment. This provides greater flexibility in the placement of the energy harvesting system.

In other examples, only the cold flow may be directed to the second heat exchanger <NUM> or only the hot flow may be directed to the first heat exchanger <NUM>. In such examples, the ambient surroundings may be sufficient to provide the other of the second heat exchanger or first heat exchanger with the required temperature gradient to produce a voltage across the thermoelectric generator <NUM>.

In this example, after passing through the second heat exchanger <NUM> and the first heat exchanger <NUM>, the cold flow and the hot flow are directed back to join the bleed air from the compressor stage at the second line <NUM> of the bleed air line <NUM>. While passing through the first heat exchanger <NUM>, the hot flow may have become hotter or cooler due to the ambient surroundings of the gas turbine engine in which the thermoelectric generator has been placed. The cold flow may also have become hotter for the same reasons. Therefore, adding the hot flow and the cold flow back to the bleed air may improve its heating capacity, for example for de-icing a wing of an aircraft. In other examples, only the hot flow may be returned to the bleed air to increase the temperature of the bleed air. In yet further examples, only the cold flow may be returned to the bleed air, which may cool the bleed air, thereby reducing a requirement to cool the air, for example when using bleed air for conditioning cabin air of an aircraft.

<FIG> shows the gas turbine engine <NUM> comprising a second example thermoelectric generator system <NUM> connected to the compressor stage via a bleed air line <NUM> which is diverted from the compressor stage of the gas turbine engine <NUM>.

The second example thermoelectric generator system <NUM> is similar to the first example thermoelectric generator system <NUM> described with reference to <FIG>, with like reference numerals denoting like components. The second example thermoelectric generator system <NUM> differs from the first example thermoelectric generator system <NUM> in that it has a different radiator system <NUM>.

The radiator system <NUM> in this example still comprises a first heat exchanger <NUM> and a second heat exchanger <NUM> which are disposed on opposing sides of the thermoelectric generator <NUM>, but in this example, once the cold flow has passed through the second heat exchanger <NUM>, it is directed to at least one of the electronic components to cool them. In this example, <FIG> shows a component heat exchanger <NUM> at the sensor <NUM>, which is configured to receive the cold flow from the second heat exchanger <NUM>. Providing the cold flow to the component heat exchanger <NUM> after it has passed through the second heat exchanger <NUM> improves the electric generation capacity of the thermoelectric generator <NUM>, since the cold flow is as cold as possible, since it has not been heated by passing through another heat exchanger.

In other examples, the cold flow may be directed to cool the sensor <NUM> or other electronic components before being provided to the second heat exchanger <NUM>.

In this second example thermoelectric generator system <NUM>, the cold flow is used to cool the same electronic components which are powered by the thermoelectric generator <NUM>, such that the electronic components are cooled more efficiently and effectively than, for example, simply using bleed air or ambient air, without the requirement for additional energy inputs or additional heat exchangers or cooling flows.

<FIG> shows the gas turbine engine <NUM> comprising a third example thermoelectric generator system <NUM> connected to the compressor stage via a bleed air line <NUM> which is diverted from the compressor stage of the gas turbine engine <NUM>.

The third example thermoelectric generator system <NUM> is similar to the first example thermoelectric generator system <NUM> described with reference to <FIG> and the second example thermoelectric generator system <NUM> described with reference to <FIG>, with like reference numerals denoting like components.

The third example thermoelectric generator system <NUM> differs from the first example thermoelectric generator system <NUM> and the second example thermoelectric generator system <NUM> in that the electronic components comprise a sensor system <NUM> which is configured to determine a first parameter, TH, a second parameter, TC, and a third parameter, T<NUM>. The first parameter is indicative of a temperature of the hot flow at, or upstream of, the first output <NUM> of the vortex tube <NUM>, the second parameter is indicative of a temperature of the cold flow at the second output <NUM> of the vortex tube <NUM>, and the third parameter is indicative of a temperature of a third fluid flow. One or more component heat exchangers <NUM> are associated with the sensor system <NUM> in a similar way to the component heat exchanger <NUM> and the sensor <NUM> in the second example thermoelectric generator system <NUM>. In other examples, there may additionally be any other sensors <NUM>, such as in the first and second example thermoelectric generator systems <NUM>, <NUM>.

The third example thermoelectric generator system <NUM> also differs from the first example thermoelectric generator system <NUM> and the second example thermoelectric generator system <NUM> in that it has a different radiator system <NUM>.

The radiator system <NUM> in this example still comprises a first heat exchanger <NUM> and a second heat exchanger <NUM> which are disposed on opposing sides of the thermoelectric generator <NUM>. In this example, the radiator system <NUM> further comprises a tube system which is configured to separately direct the hot flow, the cold flow and the third fluid flow towards a switch arrangement <NUM> upstream of the second heat exchanger <NUM> and the first heat exchanger <NUM>.

In this example, the third fluid flow is ambient air which may be derived directly from the surroundings, such as around the vortex tube <NUM>, around the sensor system <NUM>, around the radiator system <NUM> or from any other suitable place. In other examples, the third fluid flow may be a bleed air flow derived from the bleed air line.

The switch arrangement <NUM> is configured to receive each of the hot flow, the cold flow and the third fluid flow, and to be moveable between a first configuration, a second configuration and a third configuration, which are shown in more detail with reference to <FIG>.

The thermoelectric generator system <NUM> comprises a control unit <NUM> which is configured to control the switch arrangement <NUM> to move to any one of the first configuration, the second configuration and the third configuration based on the first parameter, the second parameter and the third parameter, which the control unit <NUM> is configured to receive from the sensor system <NUM>. The first parameter, the second parameter and the third parameter may be communicated wirelessly to the control unit <NUM>, or through a wired connection.

The control unit <NUM> may comprise any suitable circuitry to cause performance of the methods described herein and as illustrated in <FIG>. The control unit <NUM> may comprise: control circuitry; and/or processor circuitry; and/or at least one application specific integrated circuit (ASIC); and/or at least one field programmable gate array (FPGA); and/or single or multi-processor architectures; and/or sequential/parallel architectures; and/or at least one programmable logic controllers (PLCs); and/or at least one microprocessor; and/or at least one microcontroller; and/or a central processing unit (CPU); and/or a graphics processing unit (GPU), to perform the methods.

In various examples, the control unit <NUM> may comprise at least one processor and at least one memory. The memory may store a computer program comprising computer readable instructions that, when read by the processor, causes performance of the methods described herein, and as illustrated in <FIG>. The computer program may be software or firmware, or may be a combination of software and firmware.

The control unit <NUM> may be part of the thermoelectrical generator system <NUM> or a remote computer (such as a high-performance computing cluster in the 'cloud'). Alternatively, the control unit <NUM> may be distributed between a plurality of devices and locations. For example, the control unit <NUM> may be distributed between the thermoelectric generator system <NUM> and a high-performance computing cluster in the 'cloud'.

The processor may include at least one microprocessor and may comprise a single core processor, may comprise multiple processor cores (such as a dual core processor or a quad core processor), or may comprise a plurality of processors (at least one of which may comprise multiple processor cores). The memory may be any suitable non-transitory computer readable storage medium, data storage device or devices, and may comprise a hard disk and/or solid-state memory (such as flash memory). The memory may be permanent non-removable memory or may be removable memory (such as a universal serial bus (USB) flash drive or a secure digital card). The memory may include: local memory employed during actual execution of the computer program; bulk storage; and cache memories which provide temporary storage of at least some computer readable or computer usable program code to reduce the number of times code may be retrieved from bulk storage during execution of the code.

The computer program may be stored on a non-transitory computer readable storage medium. The computer program may be transferred from the non-transitory computer readable storage medium to the memory. The non-transitory computer readable storage medium may be, for example, a USB flash drive, an external hard disk drive, an external solid-state drive, a secure digital (SD) card, an optical disc (such as a compact disc (CD), a digital versatile disc (DVD) or a Blu-ray disc). In some examples, the computer program may be transferred to the memory via a signal (which may be a wireless signal or a wired signal). Input/output devices may be coupled to the controller <NUM> either directly or through intervening input/output controllers. Various communication adaptors may also be coupled to the controller <NUM> to enable the apparatus <NUM> to become coupled to other apparatus or remote printers or storage devices through intervening private or public networks. Non-limiting examples include modems and network adaptors of such communication adaptors.

In this example, the thermoelectric generator <NUM> is electrically connected to the control unit <NUM>, the sensor system <NUM> and an energy storage component <NUM> so that the control unit <NUM>, the sensor system <NUM> and the energy storage component <NUM> are powered by the thermoelectric generator <NUM>. In other examples, the sensor system <NUM>, the energy storage component <NUM> and the control unit <NUM> may be powered by other means and/or there may be additional or alternative electronic components which are powered by the thermoelectric generator <NUM>.

<FIG> shows the switch arrangement in the first configuration <NUM>, the second configuration <NUM> and the third configuration <NUM>.

In the first configuration, the cold flow having a temperature, TC, from the vortex tube <NUM> is directed to the second heat exchanger <NUM>, and the hot flow having a temperature, TH, from the vortex tube <NUM> is directed to the first heat exchanger <NUM>. The third fluid flow, having a temperature T<NUM>, and/or the cold flow after passing through the second heat exchanger <NUM> may be directed to the component heat exchanger <NUM> to cool the sensor system <NUM>. In other examples, the third fluid flow may be stopped with a valve, so that it is not used or may be returned to a source after cooling the sensor system <NUM> and any other electronic components.

In the second configuration, the cold flow having a temperature, TC, from the vortex tube <NUM> is directed to the second heat exchanger <NUM> and the third fluid flow having a temperature, T<NUM>, from the vortex tube <NUM> is directed to the first heat exchanger <NUM>. The hot flow having a temperature, TH, may be directed back to the bleed air line <NUM>. In some examples, the cold flow may be used to cool the sensor system <NUM> after it has passed through the second heat exchanger <NUM> and/or may be directed back to the bleed air line <NUM>.

In the third configuration, the third fluid flow having a temperature, T<NUM>, is directed to the second heat exchanger <NUM> and the hot flow having a temperature, TH, from the vortex tube <NUM> is directed to the first heat exchanger <NUM>. The cold flow having a temperature, TC, and/or the third fluid flow after passing through the cold heat exchanger <NUM> may be directed to the component heat exchanger <NUM> to cool the sensor system <NUM>. In other examples, the cold flow may be directed back to the bleed air line <NUM> or the cold flow may be stopped with a valve.

In this example, the switch arrangement <NUM> may be a single solenoid valve which is capable of managing the flows in the three configurations, or may comprise multiple valves to achieve the flow management in the three configurations.

<FIG> is a flow chart showing steps of a method <NUM> for controlling the thermoelectric generator system <NUM>.

In block <NUM>, the method <NUM> comprises monitoring the first parameter, TH, the second parameter, TC, and the third parameter T<NUM>, for example with the sensor system <NUM>. The parameters, TH, TC, T<NUM> may be sent to the control unit <NUM> or may be processed with a processor within the sensor system <NUM>.

In block <NUM>, the method <NUM> comprises determining if the third parameter T<NUM> and the second parameter TC indicate that the temperature of the third fluid flow is higher than the temperature of the cold flow. Since the temperature of the hot flow TH will always be higher than the temperature of the cold flow TC, if block <NUM> returns NO, then: <MAT>.

If block <NUM> returns NO, the method <NUM> moves to block <NUM> in which the control unit <NUM> controls the switch arrangement <NUM> to move to the third configuration, such that the hot flow (having the highest temperature) is delivered to the first heat exchanger <NUM> and the third flow (having the lowest temperature) is delivered to the second heat exchanger <NUM>, such that the possible thermal gradient across the thermoelectric generator <NUM> is maximised, thereby maximising the potential difference generated by the thermoelectric generator <NUM>.

The cold flow in this configuration may be directed to the component heat exchanger <NUM> to cool the sensor system <NUM> and/or any other electronic components which are powered by the thermoelectric generator <NUM>. In other examples, the cold flow may be directed to a heat exchanger to cool any suitable components, powered by other means and unpowered. In yet other examples, the cold flow may be directed back to the bleed air line <NUM> in the gas turbine engine <NUM>. In some examples, the cold flow and the hot flow may be returned to the bleed air line <NUM> if the compressed air is supplied to the vortex tube <NUM> from the bleed air line <NUM>.

If block <NUM> returns YES, the method <NUM> moves to block <NUM> in which the method <NUM> comprises determining if the third parameter T<NUM> and the first parameter TH indicate that the temperature of the third fluid flow is higher than the temperature of the hot flow. Since the temperature of the hot flow TH will always be higher than the temperature of the cold flow TC, if block <NUM> returns NO, then: <MAT>.

If block <NUM> returns NO, the method <NUM> moves to block <NUM> in which the control unit <NUM> controls the switch arrangement <NUM> to move to the first configuration, such that the hot flow (having the highest temperature) is delivered to the first heat exchanger <NUM> and the cold flow (having the lowest temperature) is delivered to the second heat exchanger <NUM>, such that the possible thermal gradient across the thermoelectric generator <NUM> is maximised, thereby maximising the potential difference generated by the thermoelectric generator <NUM>.

The third fluid flow in this configuration may be directed to the component heat exchanger <NUM> to cool the sensor system <NUM> and/or any other electronic components which are powered by the thermoelectric generator <NUM>. In other examples, the third fluid flow may be directed to a heat exchanger to cool any suitable components, powered by other means and unpowered. In yet other examples, the third fluid flow may be directed to the bleed air line <NUM> in the gas turbine engine <NUM> or stopped with a valve so that it does not leave the bleed air line <NUM> if it is air from the bleed air line <NUM>. The cold flow may also be directed to the component heat exchanger <NUM> after passing through the second heat exchanger <NUM>. In some examples, the cold flow and the hot flow may be returned to the bleed air line <NUM> if the compressed air is supplied to the vortex tube <NUM> from the bleed air line <NUM>.

If block <NUM> returns YES, since the temperature of the hot flow TH will always be higher than the temperature of the cold flow TC, then: <MAT>.

If block <NUM> returns YES, the method <NUM> moves to block <NUM> in which the control unit <NUM> controls the switch arrangement <NUM> to move to the second configuration, such that the third flow (having the highest temperature) is delivered to the first heat exchanger <NUM> and the cold flow (having the lowest temperature) is delivered to the second heat exchanger <NUM>, such that the possible thermal gradient across the thermoelectric generator <NUM> is maximised, thereby maximising the potential difference generated by the thermoelectric generator <NUM>.

The hot flow in this configuration may be directed back to the bleed air line <NUM> in the gas turbine engine <NUM>. In other examples, the hot flow may be directed to the component heat exchanger <NUM> to cool the sensor system <NUM> and/or any other electronic components which are powered by the thermoelectric generator <NUM>. The cold flow may additionally or alternatively be directed to the component heat exchanger <NUM> after passing through the second heat exchanger <NUM>. In some examples, the cold flow and the hot flow may be returned to the bleed air line <NUM> if the compressed air is supplied to the vortex tube <NUM> from the bleed air line <NUM>.

It can be seen that the method <NUM> therefore controls the configuration of the switch arrangement <NUM> based on the first parameter, the second parameter and the third parameter. In this method, it ensures that the highest temperature difference is used in the flows through the first heat exchanger <NUM> and the second heat exchanger <NUM> to ensure the maximum potential difference can be achieved across the thermoelectric generator <NUM>.

The method <NUM> may also include directing the energy generated by the thermoelectric generator <NUM> to the control unit <NUM>, the sensor system <NUM> and the energy storage component <NUM>.

Although it has been described that the thermoelectric generator systems <NUM>, <NUM>, <NUM> are coupled to the compressor stage of a gas turbine engine <NUM>, in other examples, the thermoelectric generator system <NUM> may be supplied with compressed air from any suitable source, and references to a bleed air line may be replaced by any air source line. For example, the thermoelectric generator system may be used outside of, and without, a gas turbine engine, with any suitable supply of compressed air.

Although it has been described that the second heat exchanger <NUM> and the first heat exchanger <NUM> of the radiator system <NUM> are configured to receive the cold flow and the hot flow respectively from the vortex tube <NUM>, one of the first heat exchanger and the second heat exchanger may simply be a hot surface or a cold surface respectively.

Claim 1:
A thermoelectric generator system (<NUM>) comprising:
a thermoelectric generator (<NUM>);
a vortex tube (<NUM>) comprising a flow input (<NUM>) configured to receive an input of compressed gas and to separate the compressed gas into a hot flow discharged from a first output (<NUM>) of the vortex tube, and a cold flow discharged from a second output (<NUM>) of the vortex tube;
a sensor system (<NUM>) configured to determine a first parameter indicative of a temperature of the hot flow, a second parameter indicative of a temperature of the cold flow and a third parameter indicative of a temperature of a third fluid flow;
a radiator system (<NUM>) comprising:
a first heat exchanger (<NUM>) and a second heat exchanger (<NUM>) disposed on opposing sides of the thermoelectric generator; and
a tube system configured to separately direct the hot flow, the cold flow and the third fluid flow towards a switch arrangement (<NUM>), wherein the switch arrangement is configured to receive each of the hot flow, the cold flow and the third fluid flow, and to be moveable between:
a first configuration in which the cold flow is directed to the second heat exchanger and the hot flow is directed to the first heat exchanger;
a second configuration in which the cold flow is directed to the second heat exchanger and the third fluid flow is directed to the first heat exchanger; and
a third configuration in which the third fluid flow is directed to the second heat exchanger and the hot fluid is directed to the first heat exchanger;
the thermoelectric generator system further comprising a control unit (<NUM>) configured to control the configuration of the switch arrangement based on the first parameter, the second parameter, and the third parameter.