Patent Description:
Hydrogen-burning gas turbine engine systems are of interest for both stationary power and propulsion applications as they do not produce carbon dioxide at the point of use. In such an engine system, hydrogen is provided to combustion apparatus of an engine in gaseous form, although it may be stored in liquid form. In aircraft propulsion applications, it is important to provide for rapid shut-off of fuel to an engine in the event of a fan-blade off, shaft breakage or a similar occurrence. In a conventional gas turbine engine, a shut-off valve in the engine's fuel line may be used to isolate combustion apparatus of the engine from its fuel supply and provide rapid engine shut-down. However, unlike kerosene, gaseous hydrogen is compressible. Therefore, if a hydrogen-burning gas turbine engine is fed with hydrogen by means of a fuel line including a shut-off valve, hydrogen may continue to flow into combustion apparatus of the engine briefly following closure of the shut-off valve, driven by the pressure differential between hydrogen in the fuel line and the combustion apparatus. Fuel provided to the combustion apparatus after activation of the shut-off valve may delay shutdown of the engine sufficiently that, in the event of a shaft-break, the angular speed of a turbine of the engine may reach a critical level, leading to a disc burst or multiple blade release which in turn results in hazardous uncontained release of engine debris.

European patent application <CIT> discloses a fuel system for a vehicle having an engine. The fuel system includes a fuel tank for holding a hydrogen fuel in a liquid phase; a fuel delivery assembly extending from the fuel tank to the engine for providing the hydrogen fuel from the fuel tank to the engine; a vaporizer in communication with the fuel delivery assembly for heating the hydrogen fuel in the liquid phase to a gaseous phase, to a supercritical phase, or both; and a high pressure pump in fluid communication with the fuel delivery assembly at a location downstream of the vaporizer for inducing a flow of the hydrogen fuel through the fuel delivery assembly to the engine.

European patent application <CIT> discloses a fuel delivery system for a gas turbine engine which comprises a cryogenic fuel tank, a first fuel line for connection to the cryogenic fuel tank, a fuel pump connected to receive fuel via the first fuel line, a plurality of fuel lines connecting the fuel pump to a combustor of the gas turbine engine, a controller configured to operate the fuel delivery system, a purge gas tank connected to the first fuel line and configured to store a purge gas for purging the plurality of fuel lines and a fuel gas tank connected to the first fuel line and configured to store a fuel gas for flushing purge gas from the plurality of fuel lines.

European patent application <CIT> discloses a propulsion system which includes a solid hydride storage unit from which gaseous hydrogen fuel is drawn, an engine comprising a combustion chamber and a piping system to draw the gaseous hydrogen fuel from the solid hydride storage unit, the piping system being interposed between the solid hydride storage unit and the combustion chamber. The combustion chamber is receptive of the gaseous hydrogen fuel drawn from the solid hydride storage unit by the piping system and is configured to combust the gaseous hydrogen fuel to drive an operation of the engine.

United States patent application <CIT> discloses a discloses a gas turbine engine which comprises a gas turbine engine; a purge gas supply line connected to a first connection section on the fuel supply line connected to the gas turbine engine; a fuel discharge line connected to a second connection section of the fuel supply line which is located downstream of the first connection section; a blowoff valve disposed on the fuel discharge line, and a passage switching device which performs switching of the fuel supply line between a fuel supply mode and a purge mode. A check valve and a flame arrester are disposed on the fuel discharge line at locations that are downstream of the blowoff valve.

European patent application <CIT> discloses a direct fuel injection system for injecting hydrogen fuel into a gas turbine combustor, the fuel injection system comprising a plurality of fuel injector blocks. Each fuel injector block includes a fuel admission duct having a fuel inlet for receiving fuel from a manifold, a fuel outlet for delivering fuel into a mixing zone and a central axis extending from the fuel inlet to the fuel outlet. Each fuel injector block also includes a plurality of air admission ducts distributed around the air admission duct, and having an air inlet for receiving air from a diffuser and an air outlet for delivering air into the mixing zone for combustion with the fuel.

According to a first aspect of the present invention, a gas turbine engine system comprises a hydrogen-burning gas turbine engine and a fuel system which comprises (i) a fuel line arranged to receive gaseous hydrogen at an input thereof and provide the gaseous hydrogen to combustion apparatus of the hydrogen-burning gas turbine engine; (ii) a vent line including a vent valve and having a first end coupled to the fuel line and a second end disposed remotely from the hydrogen-burning gas turbine engine, coupled to the exhaust (<NUM>) of the hydrogen-burning gas turbine engine; and (iii) a controller (<NUM>; <NUM>) arranged to open the vent valve in response to detection of a shaft-break of the hydrogen-burning gas turbine engine. The vent line allows the hydrogen-burning gas turbine engine to be shut down more rapidly than is the case using a shut-off valve within the fuel line.

The second end of the vent line is coupled to the exhaust or bypass duct of the hydrogen-burning gas turbine engine. When the vent valve in the fuel line is opened, gaseous hydrogen within the fuel line is rapidly evacuated therefrom.

The gas turbine engine system may comprise a store of compressed gaseous hydrogen coupled to the input of the fuel line. A shut-off valve may be provided at the input of the fuel line, providing for the store of gaseous hydrogen to be isolated from the fuel line when the vent valve is opened, thus preventing further gaseous hydrogen entering the fuel line.

Alternatively, the gas turbine engine system may further comprise a store of liquid hydrogen and an evaporator arranged to receive and evaporate liquid hydrogen from the store and provide resulting gaseous hydrogen to the input of the fuel line.

The gas turbine engine system comprises a controller arranged to open the vent valve in response to detection of a shaft-break of the hydrogen-burning gas turbine engine. The controller may be a Full-Authority Digital Electronic Controller of the hydrogen-burning gas turbine engine.

A second aspect of the invention provides an aircraft comprising a gas turbine engine according to the first aspect.

Embodiments of the invention are described below by way of example only and with reference to the accompanying drawings in which:.

Referring to <FIG>, a gas turbine engine system <NUM> comprises a hydrogen-burning gas turbine engine which includes combustion apparatus <NUM>. The combustion apparatus comprises a combustion chamber <NUM> fed by a plurality of fuel nozzles such as <NUM>. The gas turbine engine system <NUM> further comprises a fuel store <NUM> of gaseous hydrogen and a fuel line <NUM> having an input <NUM>, the fuel line <NUM> coupling the fuel store <NUM> to the combustion apparatus <NUM>. The fuel store <NUM> is coupled to the input <NUM> of the fuel line <NUM> via a shut-off valve <NUM>. A vent line <NUM> including a vent valve <NUM> couples the fuel line <NUM> to the exhaust flow <NUM> of the hydrogen-burning gas turbine engine. The state of the vent valve <NUM> (either open or closed) is controlled by a controller <NUM> which may be the FADEC (Full-Authority Digital Electronic Controller) of the hydrogen-burning gas turbine engine.

In normal operation of the gas turbine engine system <NUM>, the vent valve <NUM> is closed, shut-off valve <NUM> is open and gaseous hydrogen introduced at the input <NUM> of the fuel line <NUM> is conveyed to the combustion apparatus <NUM>. Upon detection of an engine shaft-break or similar condition requiring rapid engine shut-down, the controller <NUM> causes the vent valve <NUM> to switch from its closed state to its open state such that hydrogen within the fuel line <NUM> and combustion apparatus <NUM> is rapidly vented to the exhaust <NUM> of the hydrogen-burning gas turbine engine, thus producing rapid shut-down of the hydrogen-burning gas turbine engine. With the vent valve <NUM> in its open state, the combustion apparatus <NUM> and the input <NUM> of the fuel line <NUM> are both coupled to the exhaust <NUM>, which provides a region much lower pressure than that found in the fuel line <NUM> during normal operation of the system <NUM> and hence rapid evacuation of gaseous hydrogen gas from the fuel line <NUM>.

The shut-off valve <NUM> is also controlled by the FADEC <NUM> and closed when the vent valve <NUM> is switched from its closed state to its open state in order to prevent further gaseous hydrogen entering the fuel line <NUM>.

In a variant of the system <NUM> not in accordance with the present invention, the vent line <NUM> couples the fuel line <NUM> to the bypass duct of the hydrogen-burning gas turbine engine, or alternatively to a dump tank having a volume of five times or ten times, or more, the volume of the fuel line <NUM>. Hydrogen evacuated from the fuel line <NUM> may thereby be recovered and used subsequently. More generally, the end of the vent line <NUM> is at some location remote from the hydrogen-burning gas turbine engine, allowing hydrogen within the fuel line <NUM> to be evacuated and safely vented away from possible ignition sources.

<FIG> shows a second example gas turbine engine system <NUM> of the invention not in accordance with the present invention. The system <NUM> comprises a hydrogen-burning gas turbine engine having combustion apparatus <NUM> and a fuel line <NUM> having an input <NUM> arranged to receive gaseous hydrogen in normal operation of the system <NUM>. A vent line <NUM> includes a vent valve <NUM> and couples the fuel line <NUM> to a dump tank <NUM>, the dump tank <NUM> having a volume which is five or ten times, or more, the volume of the fuel line <NUM>. The state of the vent valve <NUM> (i.e. open or closed) is controlled by a controller <NUM>, which may be the FADEC of the hydrogen-burning gas turbine engine.

In normal operation of the gas turbine engine system, the vent valve <NUM> is closed and gaseous hydrogen introduced into the input <NUM> of the fuel line <NUM> is conveyed to the combustion apparatus <NUM>. Upon detection of an engine shaft-break or similar condition requiring rapid engine shut-down, the controller <NUM> switches the vent valve <NUM> to its open state such that fuel line <NUM> is coupled to the dump tank <NUM>, thus rapidly evacuating gaseous hydrogen from the fuel line <NUM>. The hydrogen removed to the dump tank <NUM> may be used subsequently by the system <NUM>.

With the vent valve <NUM> in its open state, the hydrogen-burning gas turbine engine is rapidly shut down due to rapid evacuation of gaseous hydrogen from the fuel line <NUM> caused by the much lower pressure within the dump tank <NUM> compared to that in the fuel line <NUM>.

In ordinary operation of the system <NUM>, the vent valve <NUM> is in its closed state and gaseous hydrogen is provided to the input <NUM> of the first fuel line <NUM> from an evaporator <NUM> arranged to receive liquid hydrogen from a liquid hydrogen store <NUM> via a cryogenic line <NUM>.

The input <NUM> of the first fuel line <NUM> may be provided with a shut-off valve (not shown) also under control of the controller <NUM> and arranged to close when the vent valve <NUM> is switched from its closed state to its open state, thus preventing further gaseous hydrogen entering the fuel line <NUM>.

Claim 1:
A gas turbine engine system (<NUM>; <NUM>) comprising a hydrogen-burning gas turbine engine and a fuel system which comprises:
(i) a fuel line (<NUM>; <NUM>) arranged to receive gaseous hydrogen at an input (<NUM>; <NUM>) thereof and provide the gaseous hydrogen to combustion apparatus (<NUM>; <NUM>) of the hydrogen-burning gas turbine engine;
(ii) a vent line (<NUM>; <NUM>) including a vent valve (<NUM>; <NUM>) and having a first end coupled to the fuel line and a second end disposed remotely from the hydrogen-burning gas turbine engine, coupled to the exhaust (<NUM>) of the hydrogen-burning gas turbine engine; and
(iii) a controller (<NUM>; <NUM>) arranged to open the vent valve in response to detection of a shaft-break of the hydrogen-burning gas turbine engine.