A propulsion system

Abstract

A propulsion system (300) for an aircraft (10) comprises a fuel reservoir (100, 800) for storing hydrogen (H2-1, H2-2) and a fuel reservoir (200) for storing a hydrocarbon fuel (HC). The propulsion system can be provided with a gas turbine engine (400) comprising a fuel injection unit (500) comprising a hydrogen pilot combustion chamber (510) in fluid communication with the hydrogen fuel reservoir (100, 800) via a flow control valve (512, 542), and further provided with a dual fuel main combustion chamber (520) in fluid communication with the hydrogen fuel reservoir (100, 800) via a flow control valve (522) and in fluid communication with the hydrocarbon fuel reservoir (200) via a flow control valve (532). A control system (600) is provided for controlling: the flow control valve (512, 542) to control the flow of hydrogen from the hydrogen fuel reservoir (100, 800) to the hydrogen pilot combustion chamber (510); the flow control valve (522) to control the flow of hydrogen from the hydrogen fuel reservoir (100, 800) to the dual fuel main combustion chamber (520); and, the flow control valve (532) to control the flow of hydrocarbon fuel (HC) from the hydrocarbon fuel reservoir (200) to the dual fuel main combustion chamber (520).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a propulsion system.

[0002] In particular to a fuel and propulsion system for an aircraft. BACKGROUND

[0003] Dual fuel capability (i.e. using more than one type of fuel at the same time, for example a mixture of hydrogen and methane) has been used for industrial gas turbines. This will reduce the emission of carbon dioxide, which is a driver of climate change. Dual fuel capability can be achieved by premixing the fuels, as both hydrogen and methane are gasses at ambient conditions.

[0004] Hydrogen has been proposed as a fuel for aircraft gas turbines in order to similarly reduce carbon emissions into the atmosphere. However, hydrogen, even when in liquid form, has a much greater volumetric energy density than the liquid hydrocarbon fuels currently used (such as kerosene). This greater fuel volume greatly increases the size of the aircraft and, as a result, the drag, and / or results in a reduction in payload and passenger numbers. The ability of an aircraft to use a combination of hydrogen and liquid hydrocarbon fuel will reduce the amount of hydrogen required by the aircraft and, as a result, the impact on drag.

[0005] Accordingly, an aircraft propulsion system capable of using a combination of hydrogen and liquid hydrocarbon fuel is highly desirable, configured to be able to burn hydrogen and liquid hydrocarbon separately or simultaneously as required in order to provide a power output at acceptable combustion temperatures, margins of stability and exhaust emissions. SUMMARY

[0006] According to the present disclosure, there is provided an apparatus and method. Other features of the invention will be apparent from the following description.

[0007] To this end, there is provided a propulsion system (300) for an aircraft (10), comprising a first fuel reservoir (100) configured to store hydrogen (H2-1), a second fuel reservoir (200) configured to store a hydrocarbon fuel (HC), and a gas turbine engine (400) comprising a fuel injection unit (500). The fuel injection unit (500) comprises a hydrogen pilot combustion chamber (510) in fluid communication with the first fuel reservoir (100) through a first flow control valve (512), and a dual-fuel main combustion chamber (520) in fluid communication with the first fuel reservoir (100) through a second flow control valve (522) and with the second fuel reservoir (200) through a third flow control valve (532). The propulsion system (300) further comprises a control system (600) for controlling the first flow control valve (512) to control the flow rate of hydrogen (H2-1) from the first fuel reservoir (100) to the hydrogen pilot combustion chamber (510), the second flow control valve (522) to control the flow rate of hydrogen from the first fuel reservoir (100) to the dual-fuel main combustion chamber (520), and / or the third flow control valve (532) to control the flow rate of hydrocarbon fuel (HC) from the second fuel reservoir (200) to the dual-fuel main combustion chamber (520).

[0008] The first fuel reservoir (100) can be a cryogenic low-pressure reservoir for storing liquid hydrogen. The propulsion system further comprises a third fuel reservoir (800) configured to store pressurized hydrogen gas (H2-2). The third fuel reservoir (800) can be in fluid communication with the hydrogen pilot combustion chamber (510) through a fourth flow control valve (542). The control system (600) can be configured to control the fourth flow control valve (542) to control the flow rate of hydrogen (H2-2) from the third fuel reservoir (800) to the hydrogen pilot combustion chamber (510) through the fourth flow control valve (542).

[0009] The first fuel reservoir (100) can be in fluid communication with the hydrogen pilot combustion chamber (510) through a heat exchanger (110) configured to provide heat to the liquid hydrogen output from the first fuel reservoir (100) to convert it into gaseous form.

[0010] The hydrogen pilot combustion chamber (510) comprises a plurality of flow outlets (514) in communication with the first fuel reservoir (100).

[0011] The hydrogen pilot combustion chamber (510) comprises a plurality of flow outlets (514) in communication with the first fuel reservoir (100) and the third fuel reservoir (800).

[0012] The dual fuel main combustion chamber (520) can include a plurality of outlets (524, 528) around the hydrogen pilot combustion chamber (510). A first subset (528) of the dual fuel main combustion chamber outlets (524) can be in fluid communication with the first fuel reservoir (100) through a first flow passage (550); while a second subset (530) of the dual fuel main combustion chamber outlets (524) is in fluid communication with the second fuel reservoir (200) through a second flow passage (552); the first flow passage (550) and the second flow passage (552) are fluidly isolated from each other.

[0013] The control system (600) can be configured to control the first flow control valve (512), the second flow control valve (522), and the third flow control valve (532) to achieve:

[0014] a. in a first mode of operation, the first flow control valve (512) is open, the second flow control valve (522) is closed, and the third flow control valve (532) is closed, such that only hydrogen is delivered to the pilot combustion chamber (510);

[0015] b. in a second mode of operation, the first flow control valve (512) is open, the second flow control valve (522) is open, and the third flow control valve (532) is closed, such that only hydrogen is delivered to the pilot combustion chamber (510) and the dual fuel main combustion chamber (520);

[0016] c. in a third mode of operation, the first flow control valve (512) is open to deliver hydrogen to the pilot combustion chamber (510), and the second flow control valve (522) and the third flow control valve (532) are both open, such that hydrogen and hydrocarbon fuel (HC) are delivered to the dual fuel main combustion chamber (520);

[0017] d. in a fourth mode of operation, the first flow control valve (512) is open, such that only hydrogen is delivered to the pilot combustion chamber (510); the second flow control valve (522) is closed, and the third flow control valve (532) is open, such that only hydrocarbon fuel (HC) is delivered to the dual fuel main combustion chamber (520).

[0018] The control system (600) can be configured to control the fourth flow control valve (542) to be closed in the first, second, third, and fourth modes of operation.

[0019] The control system (600) can be configured to control the first flow control valve (512), the second flow control valve (522), the third flow control valve (532), and the fourth flow control valve (542) to achieve:

[0020] In a fifth mode of operation, the first flow control valve (512) is closed, the second flow control valve (522) is closed, and the third flow control valve (532) is closed, and the fourth flow control valve (542) is open, such that only hydrogen is delivered from the third fuel reservoir (800) into the pilot combustion chamber (510);

[0021] In a sixth mode of operation, the first flow control valve (512) is closed, the second flow control valve (522) is closed, the third flow control valve (532) is open, such that only hydrocarbon fuel (HC) is delivered into the dual fuel main combustion chamber (520), and the fourth flow control valve (542) is open to deliver hydrogen from the third fuel reservoir (800) into the pilot combustion chamber (510).

[0022] The control system (600) can be used to control the first flow control valve (512), the second flow control valve (522), the third flow control valve (532), and the fourth flow control valve (542) to achieve, in a seventh mode of operation, that the first flow control valve (512) and the fourth flow control valve (542) are closed, such that no fuel is delivered into the pilot combustion chamber (510), and the second flow control valve (522) is closed, and the third flow control valve (532) is open, such that only hydrocarbon fuel (HC) is delivered into the dual fuel main combustion chamber (520).

[0023] The gas turbine engine (400) further comprises a combustion chamber (700).

[0024] There is also provided an aircraft (10) comprising a propulsion system (300) as described in the present disclosure, wherein the control system (600) can be used to control the first flow control valve (512), the second flow control valve (522), and the third flow control valve (532) relative to each other in terms of opening / closing rate to switch between the first mode of operation, the second mode of operation, the third mode of operation, and / or the fourth mode of operation.

[0025] The control system (600) can be used to control the first flow control valve (512), the second flow control valve (522), the third flow control valve, and the fourth flow control valve (542) relative to each other in terms of opening / closing rate to switch between the modes of operation.

[0026] The first mode of operation can correspond to a start-up, idle, and / or low power state of the gas turbine engine (400). The other modes of operation provide a range of power conditions.

[0027] Thereby, a propulsion system for an aircraft capable of operating on hydrogen is provided, which has the ability to switch to hydrocarbon fuel or to simultaneously combust hydrogen and hydrocarbon when required by certain engine conditions, such as take-off. Attached Figure Description

[0028] Examples of this disclosure will now be described with reference to the accompanying drawings, in which:

[0029] Figure 1 A view of an aircraft including the fuel and propulsion systems as described in this disclosure is shown;

[0030] Figure 2 A schematic diagram of the fuel and propulsion system described in this disclosure is shown;

[0031] Figures 3 to 7 It shows Figure 2 The different possible operating modes of the propulsion system are shown.

[0032] Figure 8 A cross-sectional view is shown of a partial example of a fuel injector and combustion chamber that can be used in the propulsion system described in this disclosure;

[0033] Figure 9 It shows Figure 8 The image shows an end view of the fuel injector. Detailed Implementation

[0034] This disclosure relates to an aircraft propulsion system, an aircraft including the propulsion system as described in this disclosure, and a method of operating the propulsion system and a method of operating the aircraft.

[0035] Figure 1 A schematic diagram of an aircraft 10 including a propulsion system 300 as described in this disclosure is shown. The aircraft 10 thus includes a fuselage 12 and wings 14. The propulsion system 300 includes a first fuel reservoir 100 configured to store hydrogen H2-1 and a second fuel reservoir 200 configured to store hydrocarbon fuel HC. The first fuel reservoir (also referred to as the "first hydrogen fuel reservoir") 100 is a cryogenic, low-pressure reservoir for storing liquid hydrogen. The first fuel reservoir 100 is in fluid communication with a hydrogen ignition combustion chamber 510 via a heat exchanger 110 configured to provide heat to the liquid hydrogen supplied from the first fuel reservoir 100 to convert it into a gaseous form.

[0036] The propulsion system may further include a third fuel reservoir 800 configured to store pressurized hydrogen H2-2. The third fuel reservoir 800 (also referred to as the "second hydrogen fuel reservoir") is in fluid communication with the hydrogen ignition combustion chamber 510 via a fourth flow control valve 542.

[0037] Figure 1 The locations of the storage devices 100, 200, and 800 shown are merely illustrative. Figure 1The locations of the engine and fuel tanks shown in the figures are typical, but they can be provided in different locations and configurations from those shown.

[0038] The propulsion system further includes a gas turbine engine 400 that includes a fuel injection unit 500, for example, as shown in Figures 2 to 7 and Figure 8 、 Figure 9 The gas turbine engine 400 also includes a combustion chamber 700 to which fuel is delivered by the fuel injection unit 500. The combustion chamber is not shown in Figures 2 to 7 . An example of a combustion chamber 700 is shown in Figure 8 . The combustion chamber 700 is annular, as shown in Figure 8 . In other examples, the combustion chamber can have a different configuration. The combustion chamber 700 can be designed in any suitable manner, the details of which need not be discussed here. Likewise, more than one fuel injection unit 500 can be provided, for example, in an annular combustion chamber 700, which can be provided with a plurality of fuel injection units 500 spaced around the inlet of the combustion chamber 700. Alternatively, if the engine 400 includes a plurality of combustion chambers, then each combustion chamber can be provided with one or more fuel injection units 500.

[0039] The heat exchanger 110 can be in thermal communication with a heat source. In some examples, the heat source can be the engine 400. In this way, some of the heat generated by the engine 400 can be transferred to the liquid hydrogen as it passes between the first reservoir 102 and the fuel injection unit 500.

[0040] The fuel injection unit 500 includes a hydrogen pilot combustion chamber 510 that is in fluid communication with the first hydrogen fuel reservoir 100 via a first flow control valve 512. In examples in which a second hydrogen fuel reservoir 800 is provided, the hydrogen pilot combustion chamber 510 is in fluid communication with the second hydrogen fuel reservoir 800 via a second flow control valve 542. For example, the hydrogen pilot combustion chamber 510 is in fluid communication with a hydrogen fuel source only and is completely isolated from any other fuel source.

[0041] The fuel injection unit 500 further includes a dual-fuel main combustion chamber 520 that is in fluid communication with the first fuel reservoir 100 via a second flow control valve 522 and in fluid communication with the second fuel reservoir 200 via a third flow control valve 532.

[0042] The propulsion system 300 may further include a control system 600, which can be used to control a first flow control valve 512 to control the flow rate of hydrogen H2-1 from the first fuel reservoir 100 to the hydrogen ignition combustion chamber 510, a second flow control valve 522 to control the flow rate of hydrogen from the first fuel reservoir 100 to the dual-fuel main combustion chamber 520, and a third flow control valve 532 to control the flow rate of hydrocarbon fuel HC from the second fuel reservoir 200 to the dual-fuel main combustion chamber 520.

[0043] The control system 600 can be used to control the fourth flow control valve 542 to control the flow rate of hydrogen H2-2 from the third fuel reservoir 800 to the hydrogen ignition combustion chamber 510.

[0044] like Figures 2 to 7 As shown in Figure 9, the hydrogen ignition combustion chamber 510 includes a plurality of flow outlets 514 in fluid communication with the first fuel reservoir 100 via a flow passage 562a. In other words, the hydrogen ignition combustion chamber 510 includes a first inlet 560 leading to a third manifold, which is in fluid communication with the plurality of flow outlets 514 via the flow passage 562a. The plurality of flow outlets 514 are also in fluid communication with the third fuel reservoir 800 via a flow passage 562b.

[0045] The flow channels 562a and 562b are in fluid communication with the first inlet 560 via a valve 544. Another flow channel 564 provides fluid communication between the valve 544 and the inlet 560.

[0046] like Figure 8 As shown, the plurality of flow outlets 514 are located on the downstream end face of the hydrogen ignition combustion chamber 510.

[0047] An internal swirler 540 may extend radially outward from the hydrogen ignition combustion chamber 510 to the dual-fuel combustion chamber 520, thereby physically connecting the hydrogen ignition combustion chamber 510 and the dual-fuel combustion chamber 520, for example, such that one can be carried on the other.

[0048] An external swirler 546 may extend radially outward from the dual-fuel combustion chamber 520 to the shroud 548, thereby physically connecting the dual-fuel combustion chamber 520 and the shroud 546, for example, such that one can be carried on the other.

[0049] The inner swirler 540 and the outer swirler 546 may include a plurality of spaced-apart blades to allow air to pass through them. The blades may be angled to the flow direction to create vortices in the airflow, thereby aiding in the mixing of fuel and air delivered to the combustion chamber 700. The blades may also be tilted in such a way as to create vortices in the airflow to atomize the liquid hydrocarbon fuel, thereby aiding in its combustion and mixing with hydrogen.

[0050] The dual-fuel main combustion chamber 520 may be configured as a ring 526 surrounding the hydrogen ignition combustion chamber 510. A plurality of outlets 524 may be provided at the downstream end of the ring 526, the outlets 524 surrounding the hydrogen ignition combustion chamber 510.

[0051] The first sub-group 528 of the dual-fuel main combustion chamber outlet 524 is in fluid communication with the first fuel reservoir 100 via a first flow passage 550. In other words, the ring 526 includes a second inlet 556 leading to a second manifold, which is in fluid communication with the first sub-group 528 of the dual-fuel main combustion chamber outlet 524. The second sub-group 530 of the dual-fuel main combustion chamber outlet 524 is in fluid communication with the second fuel reservoir 200 via a second flow passage 552. In other words, the ring 526 includes a third inlet 559 leading to a second manifold, which is in fluid communication with the second sub-group 530 of the dual-fuel main combustion chamber outlet 524. The first flow passage 550 and the second flow passage 552 are fluidly isolated from each other. The first manifold and the second manifold are also fluidly isolated from each other.

[0052] In one example (such as) Figure 2 As shown), the first subgroup 528 and the second subgroup 530 of the dual-fuel main combustion chamber outlet 524 may be disposed at the downstream end / face of the ring 526.

[0053] In the second example (such as) Figure 8 As shown), the first subgroup 528 and the second subgroup 530 of the dual-fuel main combustion chamber outlet 524 may be disposed at the downstream end / face of the ring 526, and the second subgroup 530 of the dual-fuel main combustion chamber outlet 524 may extend radially, for example as... Figure 8 As shown, the main body of the dual-fuel main combustion chamber exits upstream of the surface where the first subgroup 528 of the dual-fuel main combustion chamber outlet 524 is located.

[0054] like Figures 3 to 7 As shown, the control system 600 can control the first flow control valve 512, the second flow control valve 522, and the third flow control valve 532 in different operating modes. Figures 3 to 7 In the diagram, arrows overlapping the flow path indicate flow along the flow path. Where no arrow indicates flow, there is no flow.

[0055] In the first operating mode, such as Figure 3 As shown, the first flow control valve 512 is open, the second flow control valve 522 is closed, and the third flow control valve 532 is closed, so that only hydrogen is supplied to the ignition combustion chamber 510. This first operating mode can correspond to the start-up, idling, and / or low-power states of the gas turbine engine 400.

[0056] Other modes of operation, set out below, provide a range of power conditions to best match the requirements of the propulsion system 300 and the aircraft 10 mission.

[0057] In a second mode of operation, as shown in Figure 4 the first flow control valve 512 is open, the second flow control valve 522 is open, and the third flow control valve 532 is closed, so that only hydrogen is delivered into the pilot combustion chamber 510 and the dual fuel main combustion chamber 520. This can provide a high power cruise condition.

[0058] In a third mode of operation, as shown in Figure 5 the first flow control valve 512 is open to deliver hydrogen into the pilot combustion chamber 510, the second flow control valve 522 and the third flow control valve 532 are both open, so that hydrogen and hydrocarbon fuel HC are delivered into the dual fuel main combustion chamber 520. This can correspond to a high power condition to maximise carbon dioxide reduction while meeting nitrogen oxide emissions.

[0059] In a fourth mode of operation, as shown in Figure 6 the first flow control valve 512 is open so that only hydrogen is delivered into the pilot combustion chamber 510, and the second flow control valve 522 is closed, and the third flow control valve 532 is open so that only hydrocarbon fuel HC is delivered into the dual fuel main combustion chamber 520. This mode can correspond to a take-off condition for the aircraft / engine.

[0060] In examples where a fourth flow control valve 542 is present, the control system 600 can be used to control the fourth flow control valve 542 to be closed in the first, second, third and fourth modes of operation.

[0061] Thus, in the first, second, third and fourth modes of operation, a constant pilot combustion chamber flame is provided. In examples where hydrocarbon fuel is provided, this enables the hydrocarbon fuel to be burnt more leanly in the main combustion chamber 520, resulting in cleaner combustion and avoiding the rich main zone required in conventional dual annular staged combustion chambers which limits the nitrogen oxide reduction capability.

[0062] The control system 600 can be used to control the first flow control valve 512, the second flow control valve 522, the third flow control valve 532 and the fourth flow control valve 542 so that in a fifth mode of operation, as shown in Figure 7As shown, the first flow control valve 512 is closed, the second flow control valve 522 is closed, and the third flow control valve 532 is closed, and the fourth flow control valve 542 is open, such that only hydrogen is delivered from the third fuel reservoir 800 into the pilot combustion chamber 510. The fifth mode of operation can correspond to a normal engine start mode, and can be used to provide hydrogen to the pilot combustion chamber when a supply of liquid hydrogen from the first hydrogen fuel reservoir 100 is not available.

[0063] The control system 600 can be used to control the first flow control valve 512, the second flow control valve 522, the third flow control valve 532, and the fourth flow control valve 542, such that in the sixth mode of operation, as shown in FIG. 6B, the first flow control valve 512 is closed, the second flow control valve 522 is closed, and the third flow control valve 532 is open, such that only the hydrocarbon fuel HC is delivered into the dual fuel main combustion chamber 520 (as shown by the thick dashed line overlying the flow passage 552), and the fourth flow control valve 542 is open, delivering hydrogen from the third fuel reservoir 800 into the pilot combustion chamber 510. Figure 7

[0064] The control system 600 can be used to control the first flow control valve 512, the second flow control valve 522, the third flow control valve 532, and the fourth flow control valve 542, such that in the seventh mode of operation, the first flow control valve 512 and the fourth flow control valve 542 are closed, such that no fuel is delivered into the pilot combustion chamber 510, and the second flow control valve 522 is closed and the third flow control valve 532 is open, such that only the hydrocarbon fuel HC is delivered into the dual fuel main combustion chamber 520. Such an example can be in higher power output conditions of the gas turbine engine where the main flame is stable and the pilot is not needed. This mode can also mitigate the risk of hot damage to the pilot combustion chamber from hydrogen combustion under very demanding takeoff operating conditions. This mode can also allow the aircraft to operate when the source of liquid hydrogen fuel is not available. For example, this mode of operation can allow operation / recovery from an airport without a hydrogen refueling station to one with such capability. This mode can also correspond to a cruise condition of the engine with the pilot turned off, as the pilot can only be needed for low power operation.

[0065] The control system 600 can be used to control the relative opening / closing rates of the first flow control valve 512, the second flow control valve 522, and the third flow control valve 532 relative to one another to transition between the first mode of operation, the second mode of operation, the third mode of operation, and / or the fourth mode of operation.

[0066] The control system 600 can be used to control the relative opening / closing rates of the first flow control valve 512, the second flow control valve 522, the third flow control valve, and the fourth flow control valve 542 relative to one another to transition between the modes of operation.​

[0067] A fuel injection unit 500 containing a hydrogen piloted combustion chamber 510 has been developed to address the issues that arise from the significantly different physical properties of hydrogen compared to conventional hydrocarbon fuel HC for the aircraft 10 and gas turbine engine 400.

[0068] The main issue for the aircraft 10 using hydrogen as fuel is the low volumetric density of hydrogen, which leads to the need for large fuel tanks with the associated impact on weight and aerodynamic drag. The passenger capacity is also reduced.

[0069] By using liquid hydrogen stored at cryogenic temperatures (-253 K), the volume required to store the hydrogen fuel in the aircraft is reduced, and therefore the impact on the aircraft range is less.

[0070] The size of the hydrogen tank required to supply the piloted injection will be significantly smaller than for a 100% hydrogen fuelled aircraft 10, and there are more options, like the hydrogen tank can be located inside the aircraft 10. In addition to this baseline piloted combustion chamber allowing full range capability of the aircraft 10, the additional hydrogen feed to the main combustion chamber can allow more carbon dioxide savings without increasing the tank size. This flow can be adjusted according to the length of the flight.

[0071] Furthermore, carrying a supply of hydrocarbon fuel, such as kerosene or sustainable aviation fuel, allows the aircraft 10 to use both fuels for longer flights in the full thrust range.

[0072] Liquid hydrocarbon can be used as reserve fuel to cope with diversion situations. This reduces the size of the hydrogen tank and the associated weight and drag penalty.

[0073] The ability to vary the consumption ratio of liquid hydrocarbon and hydrogen during cruise is another potential mitigation measure to manage the increased control risk arising from hydrogen combustion.

[0074] The extreme reactivity of hydrogen and the high extinction strain rate result in excellent flame stability and allow the use of lower equivalence ratios to reduce the flame temperature without flame extinction problems at low power operation or in fuel starved conditions when the gas turbine engine 400 is derated.

[0075] The use of a hydrogen fuel piloted zone that can operate at very low equivalence ratios has the potential to eliminate the constraints limiting the nitrogen oxide reduction that can be achieved with current combustion chamber concepts.

[0076] This arrangement of the present disclosure also allows the supply of additional hydrogen to the main combustion chamber to be limited to flight conditions, such as cruise, where the delivery pressure and temperature of the compressor are significantly lower and the risk of damaging the fuel injectors is reduced. Injecting hydrogen into the airflow of the main combustion chamber ensures combustion at low equivalence ratio and low emissions. Lower hydrogen flow also reduces the size of the fuel delivery and thermal management systems.

[0077] The use of hydrogen fuel for low power operation around airports would reduce the emissions of unburnt hydrocarbons and particulates.

[0078] It is predicted that hydrogen will be less costly than green synthetic fuels requiring hydrogen and captured carbon dioxide for processing. Hydrogen piloting can also reduce the emission of nitrogen oxides from aircraft 10 using sustainable or conventional hydrocarbon fuel HC.

[0079] It is advantageous to provide a source of pressurised hydrogen as well as liquid hydrogen, as pressurised hydrogen can be stored for long periods without the boil-off problems of liquid hydrogen. This combination of fuel sources will allow operation / recovery from an airport without hydrogen refuelling facilities to an airport with hydrogen refuelling capability. The endurance of the aircraft will depend on the size of the pressurised fuel tank and the flow rate of the piloted combustion chamber.

[0080] Furthermore, the fuel injection unit 500 can employ a structure for a combustion chamber using liquid hydrocarbon fuel (e.g. kerosene) rather than a specially configured combustion chamber for dual fuel use. In other words, starting from an optimised combustion chamber design for take-off operation, in which the ports and cooling are configured for take-off (typically hot day) operating points, and the control system delivers kerosene to the main combustion chamber, a suitable configuration is determined to achieve the lowest actual main zone temperature that enables the turbine inlet temperature required for this flight condition. This sets the amount of air available for liner cooling and dilution.

[0081] The inventors have determined that, in take-off conditions, a higher hydrogen flame temperature is required to indicate a leaner combustion chamber main zone to avoid leaving less air for cooling and dilution due to excessive nitrogen oxides. The propulsion system as described in the present disclosure is provided with a combustion chamber configured to use kerosene in take-off conditions and to exploit the excellent flame stability combustion characteristics of hydrogen in the piloted zone.

[0082] In the propulsion system of the present disclosure, in order to increase the amount of hydrogen consumed in flight, additional hydrogen is delivered to the main combustion chamber during cruise.

[0083] The arrangement of the control system described in the present disclosure allows the ratio of hydrogen to hydrocarbon to be varied, so that the performance of the propulsion system can be "tuned" as required.

[0084] All papers and documents submitted with or prior to this application and pertaining to this application are hereby incorporated by reference into this specification to disclose publicly the contents thereof and are to be treated as part of the disclosure herein.

[0085] All features disclosed in this specification (including any accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, every feature disclosed in this specification is one only example of a generic series of equivalent or similar features.

[0086] Every feature disclosed in this specification (including any accompanying claims, abstract and drawings) can be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, every feature disclosed in this specification is one only example of a generic series of equivalent or similar features.

[0087] The application is not limited to the details of the above embodiment. The application extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A propulsion system (300) for an aircraft (10), characterized in that, include: The first fuel storage unit (100) is configured to store hydrogen (H2-1). The second fuel storage unit (200) is configured to store hydrocarbon fuel (HC); Gas turbine engine (400), including fuel injection unit (500), comprising: The hydrogen ignition combustion chamber (510) is in fluid communication with the first fuel reservoir (100) through the first flow control valve (512); The dual-fuel main combustion chamber (520) is in fluid communication with the first fuel reservoir (100) through the second flow control valve (522) and with the second fuel reservoir (200) through the third flow control valve (532); Control system (600), used to control: A first flow control valve (512) controls the flow rate of hydrogen (H2-1) from the first fuel reservoir (100) to the hydrogen ignition combustion chamber (510); A second flow control valve (522) controls the flow rate of hydrogen from the first fuel reservoir (100) to the dual-fuel main combustion chamber (520); A third flow control valve (532) controls the flow rate of hydrocarbon fuel (HC) from the second fuel reservoir (200) to the dual-fuel main combustion chamber (520).

2. The propulsion system (300) as described in claim 1, characterized in that, The first fuel storage unit (100) is a cryogenic, low-pressure storage unit for storing liquid hydrogen; and, The propulsion system also includes a third fuel storage unit (800) configured to store pressurized hydrogen (H2-2). The third fuel storage tank (800) is in fluid communication with the hydrogen ignition combustion chamber (510) via the fourth flow control valve (542); The control system (600) can be used to control: The fourth flow control valve (542) controls the flow rate of hydrogen (H2-2) from the third fuel reservoir (800) to the hydrogen ignition combustion chamber (510); The third fuel storage unit (800) is in fluid communication with the hydrogen ignition combustion chamber (510) via a fourth flow control valve (542).

3. The propulsion system (300) as described in claim 2, characterized in that: The first fuel storage unit (100) is in fluid communication with the hydrogen ignition combustion chamber (510) via a heat exchanger (110) configured to provide heat to the liquid hydrogen output from the first fuel storage unit (100) to convert it into a gaseous form.

4. The propulsion system (300) as described in claim 1, characterized in that: The hydrogen ignition combustion chamber (510) includes a plurality of flow outlets (514) in communication with the first fuel reservoir (100).

5. The propulsion system (300) as described in claim 1, characterized in that: The hydrogen ignition combustion chamber (510) includes a plurality of flow outlets (514) communicating with the first fuel reservoir (100) and the third fuel reservoir (800).

6. The propulsion system (300) as described in claim 1, characterized in that: The dual-fuel main combustion chamber (520) includes multiple outlets (524, 528) surrounding the hydrogen ignition combustion chamber (510). The first subgroup (528) of the dual-fuel main combustion chamber outlet (524) is in fluid communication with the first fuel reservoir (100) through the first flow channel (550); the second subgroup (530) of the dual-fuel main combustion chamber outlet (524) is in fluid communication with the second fuel reservoir (200) through the second flow channel (552); the first flow channel (550) and the second flow channel (552) are fluidly isolated from each other.

7. A propulsion system (300) as described in claim 1, characterized in that... The control system (600) is used to control the first flow control valve (512), the second flow control valve (522), and the third flow control valve (532) to perform: a. In the first operating mode, the first flow control valve (512) is open, the second flow control valve (522) is closed, and the third flow control valve (532) is closed, so that only hydrogen is delivered to the ignition combustion chamber (510); b. In the second operating mode, the first flow control valve (512) is open, the second flow control valve (522) is open, and the third flow control valve (532) is closed, so that only hydrogen is delivered to the ignition combustion chamber (510) and the dual-fuel main combustion chamber (520); c. In the third operating mode, the first flow control valve (512) opens to supply hydrogen to the ignition combustion chamber (510), and both the second flow control valve (522) and the third flow control valve (532) open, allowing hydrogen and hydrocarbon fuel (HC) to be supplied to the dual-fuel main combustion chamber (520); and, d. In the fourth operating mode, the first flow control valve (512) is open, so that only hydrogen is supplied to the ignition combustion chamber (510); the second flow control valve (522) is closed, and the third flow control valve (532) is open, so that only hydrocarbon fuel (HC) is supplied to the dual-fuel main combustion chamber (520).

8. A propulsion system (300) as described in claim 7, characterized in that, The control system (600) is used to control the fourth flow control valve (542) to close in the first, second, third and fourth operating modes.

9. A propulsion system (300) as described in claim 8, characterized in that, The control system (600) is used to control the first flow control valve (512), the second flow control valve (522), the third flow control valve (532), and the fourth flow control valve (542) to perform: In the fifth operating mode, the first flow control valve (512) is closed, the second flow control valve (522) is closed, the third flow control valve (532) is closed, and the fourth flow control valve (542) is open, so that only hydrogen is delivered from the third fuel storage unit (800) to the ignition combustion chamber (510); as well as In the sixth operating mode, the first flow control valve (512) is closed, the second flow control valve (522) is closed, the third flow control valve (532) is open so that only hydrocarbon fuel (HC) is supplied to the dual-fuel main combustion chamber (520), and the fourth flow control valve (542) is open to supply hydrogen from the third fuel storage tank (800) to the ignition combustion chamber (510).

10. A propulsion system (300) as described in any one of claims 2-9, characterized in that, The control system (600) is used to control the first flow control valve (512), the second flow control valve (522), the third flow control valve (532), and the fourth flow control valve (542) to perform: In the seventh operating mode, the first flow control valve (512) and the fourth flow control valve (542) are closed, so that no fuel is delivered to the ignition combustion chamber (510), and the second flow control valve (522) is closed, and the third flow control valve (532) is open, so that only hydrocarbon fuel (HC) is delivered to the dual-fuel main combustion chamber (520).

11. A propulsion system (300) as described in claim 1, characterized in that: The gas turbine engine (400) also includes a combustion chamber (700).

12. An aircraft (10) comprising the propulsion system as claimed in claim 7, characterized in that: The control system (600) is used to control the relative opening / closing rates of the first flow control valve (512), the second flow control valve (522) and the third flow control valve (532) to switch between a first operating mode, a second operating mode, a third operating mode and / or a fourth operating mode.

13. An aircraft (10) comprising the propulsion system as claimed in claim 9, characterized in that: The control system (600) is used to control the relative opening / closing rates of the first flow control valve (512), the second flow control valve (522), the third flow control valve, and the fourth flow control valve (542) to switch between the operating modes.

14. An aircraft (10) comprising the propulsion system as claimed in claim 7, characterized in that: The first operating mode may correspond to the start-up, idling and / or low-power state of the gas turbine engine (400).

15. An aircraft (10) comprising the propulsion system as claimed in claim 14, characterized in that: Other operating modes provide a range of power conditions.

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