GAS TURBINE ENGINE SYSTEM

A gas turbine engine system includes a hydrogen-burning gas turbine engine and a fuel system including 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 and 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. A controller is arranged to switch the vent valve from a closed state to an open state upon detection of an engine shaft-break or similar condition, thus providing rapid evacuation of gaseous hydrogen from the fuel line and hence rapid shut-down of the engine. The engine may be shut down more rapidly than is possible by means of a shut-off valve within the fuel line.

TECHNICAL FIELD

The invention relates to gas turbine engine systems.

BACKGROUND

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.

BRIEF SUMMARY

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 and (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. 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 may be 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. Alternatively, the gas turbine engine system may further comprise a dump tank, the second end of the vent line being coupled to the dump tank. The dump tank may have a volume of five times, or more, the volume of the fuel line. The dump tank may have a volume of ten times, or more, the volume of the fuel line. Gaseous hydrogen vented from the fuel line may thereby be captured rather than lost from the gas turbine engine system.

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 may comprise a controller arranged to open the vent valve in response to detection of a shaft-break of the hydrogen-burning gas turbine engine or other event. The controller may be a Full-Authority Digital Electronic Controller of the hydrogen-burning gas turbine engine. In the case where a store of compressed gaseous hydrogen is coupled to the fuel line via a shut-off valve, the controller may be arranged to close the shut-off off valve and open the vent valve in the vent line simultaneously or substantially simultaneously.

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

DETAILED DESCRIPTION

Referring toFIG.1, a gas turbine engine system100comprises a hydrogen-burning gas turbine engine which includes combustion apparatus106. The combustion apparatus comprises a combustion chamber107fed by a plurality of fuel nozzles such as109. The gas turbine engine system100further comprises a fuel store102of gaseous hydrogen and a fuel line114having an input115, the fuel line114coupling the fuel store102to the combustion apparatus106. The fuel store102is coupled to the input115of the fuel line114via a shut-off valve160. A vent line116including a vent valve104couples the fuel line114to the exhaust flow110of the hydrogen-burning gas turbine engine. The state of the vent valve104(either open or closed) is controlled by a controller112which may be the FADEC (Full-Authority Digital Electronic Controller) of the hydrogen-burning gas turbine engine.

In normal operation of the gas turbine engine system100, the vent valve104is closed, shut-off valve160is open and gaseous hydrogen introduced at the input115of the fuel line114is conveyed to the combustion apparatus106. Upon detection of an engine shaft-break or similar condition requiring rapid engine shut-down, the controller112causes the vent valve104to switch from its closed state to its open state such that hydrogen within the fuel line114and combustion apparatus106is rapidly vented to the exhaust110of the hydrogen-burning gas turbine engine, thus producing rapid shut-down of the hydrogen-burning gas turbine engine. With the vent valve104in its open state, the combustion apparatus106and the input115of the fuel line114are both coupled to the exhaust110, which provides a region much lower pressure than that found in the fuel line114during normal operation of the system100and hence rapid evacuation of gaseous hydrogen gas from the fuel line114.

The shut-off valve160is also controlled by the FADEC112and closed when the vent valve104is switched from its closed state to its open state in order to prevent further gaseous hydrogen entering the fuel line114.

In a variant of the system100, the vent line116couples the fuel line114to 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 line114.

Hydrogen evacuated from the fuel line114may thereby be recovered and used subsequently. More generally, the end of the vent line116is at some location remote from the hydrogen-burning gas turbine engine, allowing hydrogen within the fuel line114to be evacuated and safely vented away from possible ignition sources.

FIG.2shows a second example gas turbine engine system200of the invention. The system200comprises a hydrogen-burning gas turbine engine having combustion apparatus206and a fuel line214having an input215arranged to receive gaseous hydrogen in normal operation of the system200. A vent line216includes a vent valve204and couples the fuel line214to a dump tank210, the dump tank210having a volume which is five or ten times, or more, the volume of the fuel line214. The state of the vent valve204(i.e. open or closed) is controlled by a controller212, which may be the FADEC of the hydrogen-burning gas turbine engine.

In normal operation of the gas turbine engine system, the vent valve204is closed and gaseous hydrogen introduced into the input215of the fuel line214is conveyed to the combustion apparatus206. Upon detection of an engine shaft-break or similar condition requiring rapid engine shut-down, the controller212switches the vent valve204to its open state such that fuel line214is coupled to the dump tank210, thus rapidly evacuating gaseous hydrogen from the fuel line214. The hydrogen removed to the dump tank210may be used subsequently by the system100.

With the vent valve204in its open state, the hydrogen-burning gas turbine engine is rapidly shut down due to rapid evacuation of gaseous hydrogen from the fuel line214caused by the much lower pressure within the dump tank210compared to that in the fuel line214.

In ordinary operation of the system200, the vent valve204is in its closed state and gaseous hydrogen is provided to the input215of the first fuel line214from an evaporator203arranged to receive liquid hydrogen from a liquid hydrogen store202via a cryogenic line218.

The input215of the first fuel line214may be provided with a shut-off valve (not shown) also under control of the controller212and arranged to close when the vent valve204is switched from its closed state to its open state, thus preventing further gaseous hydrogen entering the fuel line214.

In a variant of the system200, dump tank210is omitted and vent line216couples the fuel line214to the exhaust or bypass duct of the hydrogen-burning gas turbine engine of the system200, or alternatively to some location remote from the hydrogen-burning gas turbine engine.