Patent ID: 12241424

DETAILED DESCRIPTION

Various embodiments are discussed in detail below. While specific embodiments are discussed, this is done for illustration purposes only. A person skilled in the relevant art will recognize that other components and configurations may be used without departing from the spirit and scope of the present disclosure.

To reduce carbon dioxide emissions from commercial aircraft, a hydrogen fuel may be used. Hydrogen fuel, however, poses a number of challenges as compared to combustible hydrocarbon liquid fuel. For example, hydrogen fuel has a relatively low boiling point, and, in its gaseous form, hydrogen fuel has a much lower power density. Hydrogen fuel, when in a gaseous form, also tends to seep through materials and attachment points between components without leaving residue. Moreover, hydrogen fuel is colorless and odorless. When hydrogen fuel burns, it has a flame that is not visible to the naked eye under normal lighting conditions.

The present disclosure discusses ways to improve the safety of hydrogen fuel systems and, particularly, such fuel systems used in aircraft. Preferred embodiments described herein relate to leak detection systems for use in hydrogen fuel systems, including, for example, hydrogen fuel systems for aircraft. Current aircraft using combustible hydrocarbon liquid fuel typically do not include systems for detecting fuel leaks. Hydrogen fuel, however, poses a number of challenges as compared to combustible hydrocarbon liquid fuel. When in a gaseous form, hydrogen fuel tends to seep through materials and attachment points between components without leaving residue. Moreover, hydrogen fuel is colorless and odorless. When hydrogen fuel burns, it has a flame that is not visible to the naked eye under normal lighting conditions. To improve the safety of aircraft using hydrogen fuel, the present disclosure provides a leak detection system that can be used onboard an aircraft to monitor for hydrogen fuel leaks.

FIG.1is a perspective view of an aircraft10that may implement various preferred embodiments. The aircraft10includes a fuselage12, wings14attached to the fuselage12, and an empennage16. The aircraft10also includes a propulsion system that produces a propulsive thrust required to propel the aircraft10in flight, during taxiing operations, and the like. The propulsion system for the aircraft10shown inFIG.1includes a pair of engines100. In this embodiment, each engine100is attached to one of the wings14by a pylon18in an under-wing configuration. Although the engines100are shown attached to the wing14in an under-wing configuration inFIG.1, in other embodiments, the engine100may have alternative configurations and be coupled to other portions of the aircraft10. For example, the engine100may additionally or alternatively include one or more aspects coupled to other parts of the aircraft10, such as, for example, the empennage16, and the fuselage12.

As will be described further below with reference toFIG.2, the engines100shown inFIG.1are gas turbine engines that are each capable of selectively generating a propulsive thrust for the aircraft10. The amount of propulsive thrust may be controlled at least in part based on a volume of fuel provided to the gas turbine engines100via a fuel system200(seeFIG.3). In the embodiments discussed herein, the fuel is a hydrogen fuel that is stored in a fuel tank210of the fuel system200. As shown inFIG.1, at least a portion of the fuel tank210is located in each wing14and a portion of the fuel tank210is located in the fuselage12between the wings14. The fuel tank210, however, may be located at other suitable locations in the fuselage12or the wing14. The fuel tank210may also be located entirely within the fuselage12or the wing14. The fuel tank210may also be separate tanks instead of a single, unitary body, such as, for example, two tanks each located within a corresponding wing14.

For the embodiment depicted, the power generator is an engine100and, in particular, a high bypass turbofan engine. The engine100may also be referred to as a turbofan engine100herein.FIG.2is a schematic, cross-sectional view of one of the engines100used in the propulsion system for the aircraft10shown inFIG.1. The turbofan engine100has an axial direction A (extending parallel to a longitudinal centerline101, shown for reference inFIG.2), a radial direction R, and a circumferential direction. The circumferential direction (not depicted inFIG.2) extends in a direction rotating about the axial direction A. The turbofan engine100includes a fan section102and a turbomachine104disposed downstream from the fan section102.

The turbomachine104depicted inFIG.2includes a tubular outer casing106that defines an annular inlet108. The outer casing106encases, in a serial flow relationship, a compressor section including a booster or low-pressure (LP) compressor110and a high-pressure (HP) compressor112, a combustion section114, a turbine section including a high-pressure (HP) turbine116and a low-pressure (LP) turbine118, and a jet exhaust nozzle section120. The compressor section, the combustion section114, and the turbine section together define at least in part a core air flowpath121extending from the annular inlet108to the jet exhaust nozzle section120. The turbofan engine further includes one or more drive shafts. More specifically, the turbofan engine includes a high-pressure (HP) shaft or a spool122drivingly connecting the HP turbine116to the HP compressor112, and a low-pressure (LP) shaft or a spool124drivingly connecting the LP turbine118to the LP compressor110.

The fan section102shown inFIG.2includes a fan126having a plurality of fan blades128coupled to a disk130in a spaced-apart manner. The fan blades128and disk130are rotatable, together, about the longitudinal centerline (axis)101by the LP shaft124. The disk130is covered by rotatable front hub132aerodynamically contoured to promote an airflow through the plurality of fan blades128. Further, an annular fan casing or outer nacelle134is provided, circumferentially surrounding the fan126and/or at least a portion of the turbomachine104. The nacelle134is supported relative to the turbomachine104by a plurality of circumferentially spaced outlet guide vanes136. A downstream section138of the nacelle134extends over an outer portion of the turbomachine104, so as to define a bypass airflow passage140therebetween.

The turbofan engine100is operable with the fuel system200and receives a flow of fuel from the fuel system200. As will be described further below, the fuel system200includes a fuel delivery assembly202providing the fuel flow from the fuel tank210to the engine100, and, more specifically, to a fuel manifold172(not labeled inFIG.2; seeFIG.3) of the combustion section114of the turbomachine104of the turbofan engine100.

The turbofan engine100also includes various accessory systems to aid in the operation of the turbofan engine100and/or an aircraft including the turbofan engine100. For example, the turbofan engine100may include a main lubrication system152, a compressor cooling air (CCA) system154, an active thermal clearance control (ATCC) system156, and a generator lubrication system158, each of which is depicted schematically inFIG.2. The main lubrication system152is configured to provide a lubricant to, for example, various bearings and gear meshes in the compressor section, the turbine section, the HP spool122, and the LP shaft124. The lubricant provided by the main lubrication system152may increase the useful life of such components and may remove a certain amount of heat from such components. The compressor cooling air (CCA) system154provides air from one or both of the HP compressor112or LP compressor110to one or both of the HP turbine116or LP turbine118. The active thermal clearance control (ATCC) system156cools a casing of the turbine section to maintain a clearance between the various turbine rotor blades and the turbine casing within a desired range throughout various engine operating conditions. The generator lubrication system158provides lubrication to an electronic generator (not shown), as well as cooling/heat removal for the electronic generator. The electronic generator may provide electrical power to, for example, a startup electrical motor for the turbofan engine100, and/or various other electronic components of the turbofan engine100, and/or an aircraft including the turbofan engine100.

Heat from these accessory systems152,154,156,158, and other accessory systems, may be provided to various heat sinks as waste heat from the turbofan engine100during operation, such as to various vaporizers220, as discussed below. Additionally, the turbofan engine100may include one or more heat exchangers162within, for example, the turbine section or120for extracting waste heat from an airflow therethrough to also provide heat to various heat sinks, such as the vaporizers220, discussed below.

It will be appreciated, however, that the turbofan engine100discussed herein is provided by way of example only. In other embodiments, any other suitable engine may be utilized with aspects of the present disclosure. For example, in other embodiments, the engine may be any other suitable gas turbine engine, such as a turboshaft engine, a turboprop engine, a turbojet engine, and the like. In such a manner, it will further be appreciated that, in other embodiments, the gas turbine engine may have other suitable configurations, such as other suitable numbers or arrangements of shafts, compressors, turbines, fans, etc. Further, although the turbofan engine100is shown as a direct drive, fixed-pitch turbofan engine100, in other embodiments, a gas turbine engine may be a geared gas turbine engine (i.e., including a gearbox between the fan126and shaft driving the fan, such as the LP shaft124), may be a variable pitch gas turbine engine (i.e., including a fan126having a plurality of fan blades128rotatable about their respective pitch axes), etc. Further, still, in alternative embodiments, aspects of the present disclosure may be incorporated into, or otherwise utilized with, any other type of engine, such as reciprocating engines, as discussed above. Additionally, in still other exemplary embodiments, the exemplary turbofan engine100may include or be operably connected to any other suitable accessory systems. Additionally, or alternatively, the exemplary turbofan engine100may not include or be operably connected to one or more of the accessory systems152,154,156,158, and162, as discussed above.

FIG.3is a schematic view of the fuel system200according to an embodiment of the present disclosure that is configured to store the hydrogen fuel for the engine100in the fuel tank210and to deliver the hydrogen fuel to the engine100via a fuel delivery assembly202. The fuel delivery assembly202includes tubes, pipes, and the like, to fluidly connect the various components of the fuel system200to the engine100. The fuel system200of this embodiment includes two fuel tanks210configured to provide hydrogen fuel to the engine100. An isolation valve204is provided in a flow path of the hydrogen fuel from each of the fuel tanks210. The isolation valve204can be closed to isolate the respective fuel tank210and opened to allow hydrogen fuel to flow from the fuel tank210.

The fuel tank210may be configured to hold the hydrogen fuel at least partially within the liquid phase, and may be configured to provide hydrogen fuel to the fuel delivery assembly202substantially completely in the liquid phase, such as completely in the liquid phase. For example, the fuel tank210may have a fixed volume and contain a volume of the hydrogen fuel in the liquid phase (liquid hydrogen fuel). As the fuel tank210provides hydrogen fuel to the fuel delivery assembly202substantially completely in the liquid phase, the volume of the liquid hydrogen fuel in the fuel tank210decreases and the remaining volume in the fuel tank210is made up by, for example, hydrogen in the gaseous phase (gaseous hydrogen). It will be appreciated that, as used herein, the term “substantially completely” as used to describe a phase of the hydrogen fuel refers to at least 99% by mass of the described portion of the hydrogen fuel being in the stated phase, such as at least 97.5%, such as at least 95%, such as at least 92.5%, such as at least 90%, such as at least 85%, or such as at least 75% by mass of the described portion of the hydrogen fuel being in the stated phase.

To store the hydrogen fuel substantially completely in the liquid phase, the hydrogen fuel is stored in the fuel tank210at very low (cryogenic) temperatures. For example, the hydrogen fuel may be stored in the fuel tank210at about −253 Deg. Celsius or less at atmospheric pressure, or at other temperatures and pressures to maintain the hydrogen fuel substantially in the liquid phase. The fuel tank210may be made from known materials such as titanium, Inconel®, aluminum, or composite materials. The fuel tank210and the fuel system200may include a variety of supporting structures and components to facilitate storing the hydrogen fuel in such a manner.

The liquid hydrogen fuel is supplied from the fuel tank210to the fuel delivery assembly202. The fuel delivery assembly202may include one or more lines, conduits, etc., configured to carry the hydrogen fuel between the fuel tank210and the engine100. The fuel delivery assembly202thus provides a flow path of the hydrogen fuel from the fuel tank210to the engine100. Herein, the terms “downstream” and “upstream” may be used to describe the position of components relative to the direction of flow of the hydrogen fuel in the flow path of the fuel delivery assembly202. The fuel delivery assembly202may also include various valves (for example, valve206) and other components to deliver the hydrogen fuel to the engine100(that are not shown inFIG.3).

The hydrogen fuel is delivered to the engine by the fuel delivery assembly202in the gaseous phase, the supercritical phase, or both (at least one of the gaseous phase and the supercritical phase). The fuel system200thus includes a vaporizer220in fluid communication with the fuel delivery assembly202to heat the liquid hydrogen fuel flowing through the fuel delivery assembly202. The vaporizer220is positioned in the flow path of the hydrogen fuel between the fuel tank210and the engine100. In the embodiment shown inFIG.3, the vaporizer220is positioned at least partially within the fuselage12or the wing14, such as at least partially within the wing14. The vaporizer220may, however, be positioned at other suitable locations in the flow path of the hydrogen between fuel tank210and the engine100. For example, the vaporizer220may be positioned external to the fuselage12and the wing14and positioned at least partially within the pylon18or the engine100. Although only one vaporizer220is shown inFIG.3, the fuel system200may include multiple vaporizers220. For example, when a vaporizer220is positioned in the engine100or in the pylon18and functions as a primary vaporizer configured to operate once the engine100is in a thermally stable condition, another vaporizer220is positioned upstream of the primary vaporizer and proximate to the fuel tank210and functions as a primer vaporizer during start-up (or prior to start-up) of the engine100.

The vaporizer220is in thermal communication with at least one heat source222,224. In this embodiment, the vaporizer220is in thermal communication with a primary heat source222and an auxiliary heat source224. In this embodiment, primary heat source222is waste heat from the engine100, and the vaporizer220is thus thermally connected to at least one of the main lubrication system152, the compressor cooling air CCA system154, the active thermal clearance control (ATCC) system156, the generator lubrication system158, and the heat exchangers162to extract waste heat from the engine100to heat the hydrogen fuel. In such a manner, it will be appreciated that the vaporizer220is configured to operate by drawing heat from the primary heat source222once the engine100is capable of providing enough heat, via the heat source224, to the vaporizer220, in order to facilitate operation of the vaporizer220.

The vaporizer220may be heated by any suitable heat source, and, in this embodiment, for example, the auxiliary heat source224is a heat source external to the engine100. The auxiliary heat source224may include, for example, an electrical power source, a catalytic heater or burner, and/or a bleed airflow from an auxiliary power unit. The auxiliary heat source224may be integral to the vaporizer220, such as when the vaporizer220includes one or more electrical resistance heaters, or the like, that are powered by the electrical power source. In this configuration the auxiliary heat source224may provide heat for the vaporizer220independent of whether or not the engine100is running and can be used, for example, during start-up (or prior to start-up) of the engine100.

As noted, the vaporizer220is in communication with the flow of the hydrogen fuel through the fuel delivery assembly202. The vaporizer220is configured to draw heat from at least one of the primary heat source222and the auxiliary heat source224to heat the flow of hydrogen fuel from a substantially completely liquid phase to a substantially completely gaseous phase or to a substantially completely supercritical phase.

The fuel delivery assembly202also includes a high-pressure pump230to induce the flow of the hydrogen fuel through the fuel delivery assembly202to the engine100. The high-pressure pump230may generally be the primary source of pressure rise in the fuel delivery assembly202between the fuel tank210and the engine100. The high-pressure pump230may be configured to increase a pressure in the fuel delivery assembly202to a pressure greater than a pressure within a combustion chamber of the combustion section114of the engine100. For example, the high-pressure pump230may be configured to increase a pressure in the fuel delivery assembly202to at least four hundred pounds per square inch (“psi”), such as to at least five hundred psi, such as to at least six hundred psi, such as to at least seven hundred psi, such as to at least five hundred fifty psi, and/or such as up to two thousand psi.

The high-pressure pump230is positioned within the flow of hydrogen fuel in the fuel delivery assembly202at a location downstream of the vaporizer220. In this embodiment, the high-pressure pump230is positioned external to the fuselage12and the wing14, and is positioned at least partially within the pylon18, or at least partially within the engine100. More specifically, the high-pressure pump230is positioned within the engine100. With the high-pressure pump230located in such a position, the high-pressure pump230may be any suitable pump configured to receive the flow of hydrogen fuel in substantially completely a gaseous phase or a supercritical phase. It will be appreciated, however, that, in other embodiments, the high-pressure pump230may be positioned at any other suitable locations, including other positions within the flow path of the hydrogen fuel. For example, the high-pressure pump230may be located upstream of the vaporizer220and may be configured to receive the flow of hydrogen fuel through the fuel delivery assembly202in a substantially completely liquid phase.

The fuel system200also includes a fuel metering unit in fluid communication with the fuel delivery assembly202. In this embodiment, the fuel metering unit is a metering valve240positioned downstream of the vaporizer220and the high-pressure pump230. The fuel system200is configured to provide the metering valve240, and the metering valve240is configured to receive hydrogen fuel in a substantially completely gaseous phase, or in a substantially completely supercritical phase. The metering valve240is further configured to provide the flow of fuel to the engine100in a desired manner. More specifically, as depicted schematically inFIG.3, the metering valve240is configured to provide a desired volume of hydrogen fuel, at, for example, a desired flow rate, to a fuel manifold172of the engine100. The fuel manifold172then distributes (provides) the hydrogen fuel received to a plurality of fuel nozzles174within the combustion section114of the engine100where the hydrogen fuel is mixed with compressed air and the mixture of hydrogen fuel, and compressed air is combusted to generate combustion gases that drive the engine100. Adjusting the metering valve240changes the volume of fuel provided to the combustion section114of the engine100and, thus, changes the amount of propulsive thrust produced by the engine100to propel the aircraft10.

The hydrogen fuel used in the engine100and in the fuel system200may be substantially pure hydrogen molecules (diatomic hydrogen). As diatomic hydrogen is the smallest molecule known to exist, hydrogen can be difficult to contain, particularly, in the gaseous form. Hydrogen, when in a gaseous form, also tends to seep through materials and attachment points between components without leaving residue. The hydrogen is prone to leak through conventional seals and other small orifices such as cracks that may form in the fuel system200over time. Hydrogen, however, burns with a nearly colorless flame that is invisible in sunlight and is an odorless, colorless gas. As a result, leaks may be difficult to detect without additional systems to facilitate detection.

The fuel system200thus includes a hydrogen leak detection system300.FIG.4is a schematic of the hydrogen leak detection system300according to an embodiment of the present disclosure. The hydrogen leak detection system300includes a leak detection controller310communicatively coupled to a plurality of sensors320. Each sensor of the plurality of sensors320is configured to monitor a component of the aircraft10for an indication of a hydrogen leak. The monitored component may be any component in fluid communication with the hydrogen fuel, including, for example, the components of the fuel system200, the fuel manifold172, the fuel nozzles174, and the combustor of the combustion section114. Other monitored components in fluid communication with the hydrogen fuel and not explicitly identified above may include fuel filters and fuel purge or primer systems. The monitored component may also be a component housing one of the components in fluid communication with the hydrogen fuel. For example, the monitored component may be a portion of the fuselage12, the wing14, the pylon18, and the engine100. Various examples of the sensors and monitored components will be discussed in more detail below.

In this embodiment, the leak detection controller310is a computing device having one or more processors312and one or more memories314. The processor312can be any suitable processing device, including, but not limited to, a microprocessor, a microcontroller, an integrated circuit, a logic device, a programmable logic controller (PLC), an application specific integrated circuit (ASIC), and/or a Field Programmable Gate Array (FPGA). The memory314can include one or more computer-readable media, including, but not limited to, non-transitory computer-readable media, a computer readable non-volatile medium (e.g., a flash memory), a RAM, a ROM, hard drives, flash drives, and/or other memory devices.

The memory314can store information accessible by the processor312, including computer-readable instructions that can be executed by the processor312. The instructions can be any set of instructions or a sequence of instructions that, when executed by the processor312, cause the processor312and the leak detection controller310to perform operations. In some embodiments, the instructions can be executed by the processor312to cause the processor312to complete any of the operations and functions for which the leak detection controller310is configured, as will be described further below. The instructions can be software written in any suitable programming language or can be implemented in hardware. Additionally, and/or alternatively, the instructions can be executed in logically and/or virtually separate threads on the processor312. The memory314can further store data that can be accessed by the processor312.

The technology discussed herein makes reference to computer-based systems and actions taken by and information sent to and from computer-based systems. One of ordinary skill in the art will recognize that the inherent flexibility of computer-based systems allows for a great variety of possible configurations, combinations, and divisions of tasks and functionality between and among components. For instance, processes discussed herein can be implemented using a single computing device or multiple computing devices working in combination. Databases, memory, instructions, and applications can be implemented on a single system or distributed across multiple systems. Distributed components can operate sequentially or in parallel.

As noted above, the leak detection controller310is communicatively coupled to each sensor of the plurality of sensors320. More specifically, the leak detection controller310includes a sensor interface316, and each sensor of the plurality of sensors320includes a communication interface321. The sensor interface316is communicatively coupled to the communication interface321. Any suitable connection and protocol may be used including wired communications and wireless communications. Suitable connections include, for example, an electrical conductor, a low-level serial data connection, such as Recommended Standard (RS) 232 or RS-485, a high-level serial data connection, such as Universal Serial Bus (USB) or the Institute of Electrical and Electronics Engineers (IEEE®) 1394, a parallel data connection, such as IEEE® 1284 or IEEE® 488, and/or a short-range wireless communication channel, such as BLUETOOTH®. When a wired connection and protocol is used, the sensor interface316and the communication interface321each may include a suitable port, and, when a wireless protocol is used the sensor interface316and the communication interface321, each may include a transmitter and a receiver.

As noted above, various suitable sensors may be used to monitor the aircraft10, including the engine100and the fuel system200, for hydrogen leaks. One suitable sensor is an infrared camera323. A plurality of infrared cameras323may be used to monitor various different components of the aircraft10. For example, the infrared camera323may be placed on the wing14to monitor the outer casing106and/or the nacelle134of the engine100(seeFIG.1). The infrared camera323may be mounted at other suitable locations, including, for example, on the fuselage12, the pylon18, or even the engine100itself. The infrared camera323is positioned to detect the infrared energy emitted by the monitored component, which, in this example, is the outer casing106and/or the nacelle134. The infrared camera323generates an output based on the infrared energy and transmits the output to the leak detection controller310via the communication interface321. The leak detection controller310then receives, via the sensor interface316, the output from the infrared camera323. The infrared camera323may output the temperature of the monitored component (or a portion thereof) or another output that can be used by the leak detection controller310to determine the temperature of the monitored component. The temperature of the monitored component is an indicator of a hydrogen fuel leak.

The leak detection controller310determines if there is a hydrogen fuel leak based on the output of the infrared camera323. As the liquid hydrogen fuel is stored at cryogenic temperatures (e.g., −253 Deg. Celsius or less), an extreme cold temperature detected by the infrared camera323may indicate a hydrogen fuel leak. The leak detection controller310receives the output of the infrared camera323, determines the temperature of the monitored component (if necessary), and compares the temperature to a threshold. When the temperature is lower than the threshold, the leak detection controller310determines that a leak has occurred in the monitored component. The threshold is a temperature lower than the temperature that the monitored component is expected to achieve during normal operation. Exterior components of the aircraft10may, for example, reach −73 Deg. Celsius (−100 Deg. Fahrenheit) during flight, and the threshold may be set at −100 Deg. Celsius (−150 Deg. Fahrenheit).

The infrared camera323may also be used to identify an extremely hot temperature that may indicate a hydrogen fuel leak that has resulted in combustion (a fire). The leak detection controller310receives the output of the infrared camera323, determines the temperature of the monitored component (if necessary), and compares the temperature to a threshold. When the temperature is higher than the threshold, the leak detection controller310determines that a leak has occurred in the monitored component, or, more specifically in this example, a hydrogen fire has occurred. The threshold in this example is a temperature higher than the temperature that the monitored component is expected to achieve during normal operation. The nacelle134and the outer casing106may reach temperatures between 426 Deg. Celsius and 538 Deg. Celsius (800 Deg. Fahrenheit and 1,000 Deg. Fahrenheit) during normal operation, and the threshold may be set at 815 Deg. Celsius (1,500 Deg. Fahrenheit).

The leak detection controller310may use the temperature of the monitored component, based on the output of the infrared camera323, in other suitable ways to determine if a leak has occurred. For example, the leak detection controller310may identify the temperature at a plurality of different times to calculate a rate of change in the temperature. A rapid decrease in the temperature may indicate a hydrogen fuel leak, and a rapid increase in the temperature may indicate a hydrogen fuel leak with combustion. The leak detection controller310then compares the calculated rate of change in the temperature of the monitored component to a lower threshold and/or an upper threshold. If the calculated rate of decrease in the temperature is lower than the lower threshold, the leak detection controller310determines that a leak has occurred in the monitored component. If the calculated rate of increase in the temperature is higher than the higher threshold, the leak detection controller310determines that a leak has occurred in the monitored component or, more specifically in this example, a hydrogen fire has occurred.

Another suitable sensor that may be used in the hydrogen leak detection system300is a speed of sound sensor325. The speed of sound sensor325is configured to measure the speed of sound in the gas surrounding the speed of sound sensor325. Hydrogen has a lower density than air, and, as such, the speed of sound will increase in hydrogen as compared to air. Accordingly, the speed of sound or a change in the speed of sound is an indicator of a hydrogen fuel leak.

The speed of sound sensor325in conjunction with the leak detection controller310may be configured to detect a change, and, more specifically, an increase in the speed of sound in the gas surrounding the speed of sound sensor325. The speed of sound sensor325generates an output corresponding to the speed of sound surrounding the speed of sound sensor325and transmits the output to the leak detection controller310via the communication interface321. The leak detection controller310then receives, via the sensor interface316, the output from the speed of sound sensor325. The speed of sound sensor325may output the speed of sound in the gas surrounding the speed of sound sensor325or another output that can be used by the leak detection controller310to determine the speed of sound. The leak detection controller310receives the output of the speed of sound sensor325, determines the speed of sound (if necessary), and compares the speed of sound to a threshold. The threshold is a speed of sound higher than the speed of sound of the gas surrounding the speed of sound sensor325during normal operation. When the speed of sound is higher than the threshold, the leak detection controller310determines that a leak has occurred in a monitored component. Alternatively, the leak detection controller310may identify the speed of sound at a plurality of different times to calculate an increase in the speed of sound between the plurality of times. An increase in the speed of sound greater than a threshold or of a set percent increase may indicate a hydrogen fuel leak. If the calculated rate of increase in the speed of sound is higher than the threshold or greater than the set percent increase, the leak detection controller310determines that a leak has occurred in the monitored component.

One suitable speed of sound sensor325is a surface acoustic wave (SAW) sensor332. The SAW sensor332may be configured to detect the speed of sound in the gas surrounding the SAW sensor332. The SAW sensor332may be placed on a monitored component to monitor the gas surrounding the monitored component for hydrogen leaks or in a compartment to monitor for hydrogen leaks. The SAW sensor332may be placed on any of the monitored components discussed above. For example,FIG.5Ashows a plurality of SAW sensors332positioned to monitor the fuel tank210as the monitored component, andFIG.5Bshows a plurality of SAW sensors332positioned on a pipe334of the fuel delivery assembly202as the monitored component. InFIGS.5A and5B, a plurality of the SAW sensors332is arrayed on an outer surface of the fuel tank210and the pipe334, respectively. Only some of the SAW sensors332are labeled inFIGS.5A and5B. If a crack336occurs, for example, in the fuel tank210(as shown inFIG.5A), the SAW sensor332in combination with the leak detection controller310will detect the change of the speed of sound surrounding the SAW sensor332and determine that a hydrogen leak as occurred in the fuel tank210.

A further suitable sensor that may be used in the hydrogen leak detection system300is a thermal conductivity sensor327, as shown inFIG.4. The thermal conductivity sensor327is configured to measure the thermal conductivity of the gas surrounding the thermal conductivity sensor327. Hydrogen has a higher thermal conductivity than the oxygen and nitrogen that make up 99% of air, and, as such, the thermal conductivity will increase in hydrogen as compared to air. Accordingly, the thermal conductivity or a change in the thermal conductivity is an indicator of a hydrogen fuel leak.

The thermal conductivity sensor327in conjunction with the leak detection controller310may be configured to detect a change, and, more specifically, an increase in the thermal conductivity in the gas surrounding the thermal conductivity sensor327. The thermal conductivity sensor327generates an output corresponding to the thermal conductivity surrounding the thermal conductivity sensor327and transmits the output to the leak detection controller310via the communication interface321. The leak detection controller310then receives, via the sensor interface316, the output from the thermal conductivity sensor327. The thermal conductivity sensor327may output the thermal conductivity in the gas surrounding the thermal conductivity sensor327or another output that can be used by the leak detection controller310to determine the thermal conductivity. The leak detection controller310receives the output of the thermal conductivity sensor327, determines the thermal conductivity (if necessary), and compares the thermal conductivity to a threshold. The threshold is a thermal conductivity higher than the thermal conductivity of the gas surrounding the thermal conductivity sensor327during normal operation. When the thermal conductivity is higher than the threshold, the leak detection controller310determines that a leak has occurred in a monitored component. Alternatively, the leak detection controller310may identify the thermal conductivity at a plurality of different times to calculate an increase in the thermal conductivity between the plurality of times. An increase in the thermal conductivity greater than a threshold or of a set percent increase may indicate a hydrogen fuel leak. If the calculated rate of increase in the thermal conductivity is higher than the threshold or greater than the set percent increase, the leak detection controller310determines that a leak has occurred in the monitored component. The SAW sensor332can also be configured to detect the thermal conductivity of the gas surrounding the SAW sensor332, and, thus, the SAW sensor332is an example of a suitable thermal conductivity sensor327. When used as a thermal conductivity sensor327, the SAW sensor332can be arranged as discussed above.

Yet another sensor that may be used in the hydrogen leak detection system300is a laser diode spectroscopy sensor329. The laser diode spectroscopy sensor329emits a beam of laser light to excite a gas. Then, the laser diode spectroscopy sensor329detects the wavelengths of light emitted when the gas is excited. When hydrogen is present, the hydrogen will emit a light with a characteristic wavelength. The emitted light is detected by the laser diode spectroscopy sensor329and may be identified as corresponding to the characteristic wavelength of hydrogen, indicating that a leak has occurred. The laser diode spectroscopy sensor329generates an output corresponding to an indication that a wavelength of light corresponding to hydrogen has been detected and transmits the output to the leak detection controller310via the communication interface321. The leak detection controller310then receives, via the sensor interface316, the output from the laser diode spectroscopy sensor329. When the output of the laser diode spectroscopy sensor329indicates the presence of hydrogen, the leak detection controller310determines that a leak has occurred. As with the other sensors of the plurality of sensors320discussed herein, the laser diode spectroscopy sensor329is located on a monitored component to monitor the component for the presence of hydrogen.

The examples of the plurality of sensors320discussed above are configured to detect attributes of parameters of the hydrogen in the hydrogen fuel. The sensors of the plurality of sensors320are not so limited and the sensors discussed above, or other suitable sensors, may be used to detect other attributes. In some embodiments, additives may be added to the hydrogen fuel and the sensors may be configured to detect those additives or parameters associated with those additives. Such additives may include, for example, safety markers added to the hydrogen fuel. One such safety marker is an odorant. Suitable odorants include, for example, mercaptans or sulfides. When an odorant is used, the sensor may be an appropriate sensor configured to detect the presence of the odorant. Another suitable visual safety marker is a noble gas, such as helium, neon, argon, krypton, xenon, and radon. The sensor may be configured to detect the presence of the noble gas. The SAW sensor332and the laser diode spectroscopy sensor329are examples of sensors that may be configured to detect the noble gas. For example, when the noble gas is present and excited by the beam of laser light emitted by the laser diode spectroscopy sensor329, the laser diode spectroscopy sensor329detects the characteristic wavelengths of the noble gas, indicating that a leak has occurred.

The leak detection controller310is also communicatively coupled to at least one indicator340. When the leak detection controller310determines that a leak has occurred, the leak detection controller310transmits an output to the indicator340to alert personnel that a hydrogen leak has occurred. Any suitable indicator340may be used to issue the alert. For example, the indicator340may be a display screen342, and, upon receipt of the output from the leak detection controller310, the display screen342displays the alert to indicate that a hydrogen leak has been detected. The alert may take any suitable form, including, for example, a warning symbol or a danger symbol and text. When text is included in the alert, the location of the hydrogen leak may also be included. For example, the leak detection controller310determines from which sensor of the plurality of sensors320the hydrogen leak is detected and uses that information to determine the location of the leak. The leak detection controller310then includes location information in the output to the display screen342, and the display screen342uses the location information to display the location of the hydrogen fuel leak.

A light344is another suitable indicator340. When the leak detection controller310determines that a leak has been detected, the leak detection controller310transmits an output to turn the light344on. Alternatively, the light344may be configured to flash, in order to provide the alert that a hydrogen leak has been detected.

A speaker346is another suitable indicator340. The leak detection controller310may be configured to transmit an output that causes the speaker346to issue an audible alert. The audible alert may be an alarm indicating that a hydrogen leak has occurred, may be speech stating that a hydrogen leak has occurred, or both. When the audible alert includes speech, such speech may state the location of the hydrogen leak when location information is provided in the output from the leak detection controller310.

The leak detection controller310and the indicator340may be dedicated to the hydrogen leak detection system300. In such a case, each of the leak detection controller310and the indicator340may be located in the engine100, such as in the nacelle134, or in the pylon18. But, each of the leak detection controller310and the indicator340may be positioned in other suitable locations including the fuselage12and the wing14. The leak detection controller310may also be communicatively coupled to other controllers of the aircraft10. Such controllers may include, for example, an engine controller180and a controller that is part of the flight control system for the aircraft10(flight controller30). The output of the leak detection controller310may be received by the engine controller180and/or the flight controller30. Alternatively, the leak detection controller310may be incorporated or configured as part of the engine controller180or the flight controller30.

The engine controller180is schematically shown inFIG.2, and may be a computing device, as in the leak detection controller310discussed above, having one or more processors182and one or more memories184. The engine controller180is configured to operate various aspects of the engine100and the fuel system200, including, for example, opening and closing valves, such as valves204,206,208or metering valve240, operating the vaporizer220, and operating the high-pressure pump230. The engine controller180may be communicatively coupled to an indicator, such as a display device186and a speaker188. The engine controller180may receive the output of the leak detection controller310, and, when the output indicates that a hydrogen leak has been detected, generate an alert to be displayed or emitted on the indicator, such as the display device186and the speaker188in a manner similar to the alerts discussed above.

Additionally, when the engine controller180receives an output from the hydrogen leak detection system300that a leak has been detected, the engine controller180may be configured to take mitigating actions. For example, the fuel system200may include redundant components and the mitigating action may be switching to the redundant components. The aircraft10may include an entire fuel system200that is redundant or only certain components of the fuel system200may be redundant. As shown inFIG.3, for example, the fuel system200discussed herein includes redundant fuel tanks210. If a hydrogen leak is detected in one of the fuel tanks210by the leak detection controller310, the engine controller180receives the output from the leak detection controller310, including location information, and takes a mitigating action, which, in this case, is switching fuel tanks210. More specifically, the mitigating action includes isolating the fuel tank210that has the hydrogen leak by closing one of the isolation valves204, and opening the other isolation valve204, if it is not already open, to provide hydrogen fuel from the other fuel tank210. Another mitigating action may be isolating or shutting off all or part of the fuel system200. For example, the engine controller180may operate valve206to isolate the components in the wing14from those in the pylon18and the engine100, or the engine controller180may operate one of the isolation valves204to isolate one of the fuel tanks210. A further mitigating action may be venting the area of the hydrogen fuel leak to atmosphere to minimize the buildup of hydrogen or to keep the hydrogen concentration below an acceptable limit (such as the minimum concentration of hydrogen necessary to sustain combustion). For example, if the hydrogen leak is detected in a component of the fuel system200located in the pylon18, the engine controller180may open a vent valve208to vent the pylon18to the atmosphere. Yet another mitigating action may be shutting down (deactivating) systems or components. For example, the engine controller180may shut down the engine100when the leak detection controller310determines that a hydrogen fuel leak has occurred.

The flight controller30is schematically shown inFIG.1and may be a computing device, as in the leak detection controller310discussed above, having one or more processors32and one or more memories34. The flight controller30is configured to operate various aspects of the aircraft10and may be communicatively coupled to the engine controller180and/or the leak detection controller310. The flight controller30of this embodiment is located in the fuselage12. The aircraft10includes a cockpit20where pilots fly the aircraft10. The flight controller30is communicatively coupled to a plurality of controls (not shown) in the cockpit20for operating the aircraft10. The flight controller30is also communicatively coupled to an indicator, such as a display device36and a speaker38. The flight controller30may receive the output of the leak detection controller310, and, when the output indicates that a hydrogen leak has been detected, generate an alert to be displayed or emitted on the indicator, such as the display device36and the speaker38in a manner similar to the alerts discussed above. In this embodiment, the display device36and the speaker38are in the cockpit20to alert the pilots of a hydrogen fuel leak, allowing the pilots to take appropriate mitigating actions.

In the embodiments discussed above, the fuel system200stores hydrogen fuel as a liquid in the fuel tank210. However, the hydrogen leak detection system300discussed herein is not so limited and it may be used with fuel systems200where the hydrogen fuel is stored in a gaseous phase. In such a system, the vaporizer220may be omitted.

Although the aircraft10shown inFIG.1is an airplane, the embodiments described herein may also be applicable to other aircraft10, including, for example, helicopters and unmanned aerial vehicles (UAV). The aircraft discussed herein are fixed-wing aircraft or rotor aircraft that generate lift by aerodynamic forces acting on, for example, a fixed wing (e.g., wing14) or a rotary wing (e.g., rotor of a helicopter), and are heavier-than-air aircraft, as opposed to lighter-than-air aircraft (such as a dirigible). In addition, the embodiments described herein may also be applicable to other applications where hydrogen is used as a fuel. The engines described herein are gas turbine engines, but the embodiments described herein also may be applicable to other engines. Further, the engine, specifically, the gas turbine engine, is an example of a power generator using hydrogen as a fuel, but hydrogen may be used as a fuel for other power generators. For example, the power generator may be a fuel cell (hydrogen fuel cell) where the hydrogen is provided to the fuel cell to generate electricity by reacting with air. Such power generators may be used in various applications, including stationary power generation systems (including both gas turbines and hydrogen fuel cells) and other vehicles beyond the aircraft10explicitly described herein, such as boats, ships, cars, trucks, and the like.

Further aspects of the present disclosure are provided by the subject matter of the following clauses.

A hydrogen fuel system comprising: a fuel tank for holding a hydrogen fuel; a power generator configured to generate power; a fuel delivery assembly extending from the fuel tank to the power generator, the fuel delivery assembly being configured to provide the hydrogen fuel from the fuel tank to the power generator in at least one of a gaseous phase and a supercritical phase; a monitored component, the monitored component being a component of one of the fuel tank, the power generator, and the fuel delivery assembly; and a fuel leak detection system including: (a) a sensor positioned to monitor at least a portion of the monitored component, the sensor being configured (i) to sense a parameter corresponding to a hydrogen fuel leak of the monitored component, and (ii) to generate an output; and (b) a controller communicatively coupled to the sensor, the controller configured (i) to receive the output of the sensor, (ii) to determine, based on the output of the sensor, if a leak has occurred in the monitored component, and (iii) to generate an output indicating a fuel system leak when the controller determines that the leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the power generator is an engine having an engine controller, the engine controller being configured to receive the output of the controller of the fuel leak detection system.

The hydrogen fuel system of any preceding clause, wherein the power generator is an engine having an engine controller, the engine controller being the controller of the fuel leak detection system.

The hydrogen fuel system of any preceding clause, wherein the power generator is an engine having an engine controller, the engine controller being configured to take a mitigating action when the controller of the fuel leak detection system determines that the leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, further comprising a compartment, the compartment having the monitored component located therein, wherein the mitigating action is venting the compartment to atmosphere.

The hydrogen fuel system of any preceding clause, wherein the mitigating action is isolating the monitored component.

The hydrogen fuel system of any preceding clause, further comprising an isolation valve, and wherein isolating the monitored component includes closing the isolation valve.

The hydrogen fuel system of any preceding clause, further comprising a redundant component, the redundant component being a component of one of the fuel tank, the power generator, and the fuel delivery assembly, wherein the mitigating action is switching from the monitored component to the redundant component.

The hydrogen fuel system of any preceding clause, wherein the fuel tank is a first fuel tank, the first fuel tank being the monitored component, and wherein the hydrogen fuel system further comprises a second fuel tank, the second fuel tank being the redundant component.

The hydrogen fuel system of any preceding clause, wherein the mitigating action is shutting down the engine.

The hydrogen fuel system of any preceding clause, wherein the fuel leak detection system further includes an indicator, the indicator being configured receive the output from the controller of the fuel leak detection system and to provide an alert indicating a fuel system leak, when the controller determines the leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the indicator is a display configured to display the alert.

1The hydrogen fuel system of any preceding clause, wherein the indicator is a speaker and the alert is an audible alert.

The hydrogen fuel system of any preceding clause, wherein the indicator is a light and when the alert is provided, the light is one of on and flashing.

The hydrogen fuel system of any preceding clause, wherein the sensor is an infrared camera configured to monitor the temperature of the monitored component.

The hydrogen fuel system of any preceding clause, wherein the controller is configured to determine, based on the output of the infrared camera, if the temperature is lower than a threshold and, when the temperature is lower than the threshold, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the controller is configured to determine, based on the output of the infrared camera, if the temperature is higher than a threshold and, when the temperature is higher than the threshold, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the controller is configured to determine, based on the output of the infrared camera, a temperature rise over a period of time, and, when the temperature rise over the period of time is higher than a threshold, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the sensor is a speed of sound sensor configured to detect the speed of sound in a surrounding gas, and wherein the controller is configured to determine, based on the output of the speed of sound sensor, if the speed of sound is higher than a threshold and, when the speed of sound is higher than the threshold, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the speed of sound sensor is a surface acoustical wave sensor.

The hydrogen fuel system of any preceding clause, wherein the sensor is a thermal conductivity sensor configured to detect a change in the thermal conductivity of a surrounding gas, and wherein the controller is configured to determine, based on the output of the thermal conductivity sensor, if the thermal conductivity is higher than a threshold and, when the thermal conductivity is higher than the threshold, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the thermal conductivity sensor is a surface acoustical wave sensor.

The hydrogen fuel system of any preceding clause, wherein the sensor is a surface acoustical wave sensor.

The hydrogen fuel system of any preceding clause, wherein the sensor is a laser diode spectroscopy sensor configured to detect the presence of the wavelengths of light emitted when hydrogen gas is excited, and wherein, when the presence of the wavelengths of light emitted when hydrogen gas is excited are detected, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the hydrogen fuel includes a safety marker and the sensor is configured to detect the presence of the safety marker.

The hydrogen fuel system of any preceding clause, wherein the safety marker is a noble gas, wherein the sensor is a laser diode spectroscopy sensor configured to detect the presence of the wavelengths of light emitted when the noble gas is excited, and wherein, when the presence of the wavelengths of light emitted when the noble gas is excited are detected, the controller determines that a leak has occurred in the monitored component.

The hydrogen fuel system of any preceding clause, wherein the monitored component includes an outer surface and the sensor is positioned on the outer surface of the monitored component.

The hydrogen fuel system of any preceding clause, wherein fuel leak detection system further includes a plurality of sensors arrayed on the outer surface of the monitored component.

The hydrogen fuel system of any preceding clause, wherein fuel leak detection system further includes a plurality of sensors.

The hydrogen fuel system of any preceding clause, wherein the power generator is a gas turbine engine.

An aircraft comprising: a fuselage; a wing connected to the fuselage; the hydrogen fuel system of any preceding clause, wherein the fuel tank is positioned at least partially within at least one of the fuselage and the wing and the power generator is configured to generate power for the aircraft.

The aircraft of any preceding clause, wherein the power generator is a gas turbine engine.

The aircraft of any preceding clause, further comprising a flight control system, the flight control system being configured to receive the output of the controller of the fuel leak detection system.

The aircraft of any preceding clause, further comprising a flight control system, the flight control system having a controller, the controller of the flight control system being the controller of the fuel leak detection system.

The aircraft of any preceding clause, further comprising a cockpit located in the fuselage, wherein the fuel leak detection system further includes an indicator located in the cockpit, the indicator being configured receive the output from the controller of the fuel leak detection system and to provide an alert indicating a fuel system leak, when the controller determines the leak has occurred in the monitored component.

Although the foregoing description is directed to the preferred embodiments, it is noted that other variations and modifications will be apparent to those skilled in the art, and may be made without departing from the spirit or scope of the disclosure Moreover, features described in connection with one embodiment may be used in conjunction with other embodiments, even if not explicitly stated above.