Abstract: Disclosed is a fuel system for a gas turbine engine having a core exhaust and a combustion section. The system comprises a fuel pump for fluid communication with a fuel reservoir; a driving turbine for driving the fuel pump; and an air feed to drive the driving turbine, the air feed being fluidly connectable to the core exhaust of the gas turbine engine. Also disclosed is a fuel system comprising: a fuel pump for fluid communication with a fuel reservoir; a fuel line from the fuel pump for fluid communication with the combustion section of the gas turbine engine; and an air feed to a heat exchanger, the air feed being fluidly connectable to the core exhaust of the gas turbine engine, wherein the fuel line is in thermal communication with the air feed within a heat exchanger.

Abstract: A fuel delivery system (201) is shown for delivering the hydrogen fuel from a cryogenic storage system to a fuel injection system in a gas turbine engine. The fuel delivery system includes a pump (301), a metering device (302), and a fuel heating system (303,304) for heating the hydrogen fuel to an injection temperature for the fuel injection system.

Abstract: 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.

Abstract: Disclosed is a fuel system for a gas turbine engine. The system comprises a fuel pump for fluid communication with a fuel reservoir; a driving turbine for driving the fuel pump; and a source of compressed air flow to drive the driving turbine. The source of compressed air may be the engine core, a dedicated fuel system compressor or the compressor of a cabin blower system.

Abstract: Disclosed is a fuel system for a gas turbine engine having a core exhaust and a combustion section. The system comprises a fuel pump for fluid communication with a fuel reservoir; a driving turbine for driving the fuel pump; and an air feed to drive the driving turbine, the air feed being fluidly connectable to the core exhaust of the gas turbine engine. Also disclosed is a fuel system comprising: a fuel pump for fluid communication with a fuel reservoir; a fuel line from the fuel pump for fluid communication with the combustion section of the gas turbine engine; and an air feed to a heat exchanger, the air feed being fluidly connectable to the core exhaust of the gas turbine engine, wherein the fuel line is in thermal communication with the air feed within a heat exchanger.

Abstract: An aircraft propulsion system includes a hydrocarbon fuel store, a hydrogen fuel store, an engine system capable of producing thrust by combusting hydrocarbon fuel and/or combusting or oxidising hydrogen fuel, a conveying system to convey hydrocarbon and hydrogen fuel from the fuel stores to the engine system and a control system to control the respective flow rates of the fuel within the conveying system. The control system adapts the fractions of the total fuel energy flow rate to the engine system represented by the hydrocarbon and hydrogen fuel energy flow rates in order to reduce climate warming impact caused by at least one of carbon dioxide, water vapour and condensation trails and/or increase climate cooling impact caused by condensation trails produced by the aircraft propulsion system compared to a dual-fuel propulsion system in which a reserve of hydrocarbon fuel is entirely combusted before any of a reserve of hydrogen fuel.

Abstract: An aircraft propulsion system includes a hydrocarbon fuel store, a hydrogen fuel store, an engine system capable of producing thrust by combusting hydrocarbon fuel and/or combusting or oxidising hydrogen fuel, a conveying system to convey hydrocarbon and hydrogen fuel from the fuel stores to the engine system and a control system to control the respective flow rates of the fuel within the conveying system. The control system adapts the fractions of the total fuel energy flow rate to the engine system represented by the hydrocarbon and hydrogen fuel energy flow rates in order to reduce climate warming impact caused by at least one of carbon dioxide, water vapour and condensation trails and/or increase climate cooling impact caused by condensation trails produced by the aircraft propulsion system compared to a dual-fuel propulsion system in which a reserve of hydrocarbon fuel is entirely combusted before any of a reserve of hydrogen fuel.

Abstract: A fuel delivery system (201) is shown for delivering the hydrogen fuel from a cryogenic storage system to a fuel injection system in a gas turbine engine. The fuel delivery system includes a pump (301), a metering device (302), and a fuel heating system (303,304) for heating the hydrogen fuel to an injection temperature for the fuel injection system.

Abstract: A case cooling calibration system for a gas turbine engine includes a rotor casing, and a stage, rotatably mounted within the rotor casing. The rotor-casing includes in-series fluid communication, a duct, a flow control valve, and a manifold. The valve regulates an air flow through the duct to the manifold, which is arranged radially outwardly around the casing radially coplanar with the rotor stage. A temperature sensing apparatus is positioned on the rotor casing, radially outwardly of the rotor stage. A controller regulates the valve in a stepwise manner providing a variable cooling air-flow to the rotor-casing. A processor calculates a correction depending on a comparison between the rotor casing temperature and a predicted rotor-casing temperature for a given engine power condition. An engine controller controls the valve depending on the correction characteristic to maintain a predetermined operational radial clearance between the rotor-stage and the rotor-casing.

Abstract: A case cooling calibration system for a gas turbine engine comprises a rotor casing, and a rotor stage, rotatably mounted within the rotor casing. The rotor casing comprises in series fluid communication, a duct, a flow control valve, and a manifold. The valve is operable to regulate an air flow through the duct to the manifold, with the manifold arranged radially outwardly around the casing radially coplanar with the rotor stage. A temperature sensing apparatus is positioned on the rotor casing, radially outwardly of the rotor stage. A controller is operable to regulate the valve in a stepwise manner to provide a variable cooling air flow to the rotor casing. A processor is operable to calculate a correction characteristic in dependence on a comparison between the rotor casing temperature and a predicted rotor casing temperature for a given engine power condition.

Abstract: An apparatus, for example for a pitch change mechanism, includes a cylinder having a magnetic portion defining an annular array of features extending parallel to the longitudinal axis of the cylinder, the cylinder rotating in use and able to translate longitudinally. There is a sensing arrangement including a stationary magnetised core and two coils connected in series and wound around the core. In use, the cylinder rotates and current is induced in the coils. Monitoring equipment is arranged to calculate rotational speed of the cylinder from the frequency of the current and to calculate longitudinal position from the relative amplitude of the current in each coil. Also a method.

Abstract: A method and arrangement of controlling blade pitch angle of a set of rotor blades. The method comprises providing a target blade pitch angle to a controller mounted on the rotor; measuring the speed of rotation of the rotor using a rate gyro mounted on the rotor; calculating the blade pitch angle required to match the target blade pitch angle by summing the target blade pitch angle and the measured rotational speed; and actuating the blades to the calculated blade pitch angle.

Abstract: A engine such as a gas turbine engine has a bladed rotor 24 having variable pitch blades 8. In normal operation, the pitch angle of the blades 8 is controlled by a primary pitch control system. A back-up system is provided for controlling the blades 8, for example to displace them to a feathered condition, in the event of failure of the primary pitch control system. The back-up system comprises a pump 32 mounted on the rotor 24, and driven by relative rotation between the rotor 24 and a contra-rotating rotor 23. In response to a failure signal on a conduit 48, the pump delivers hydraulic fluid under pressure to a secondary actuator 30, which acts on the blade 8.

Abstract: An apparatus, for example for a pitch change mechanism, includes a cylinder having a magnetic portion defining an annular array of features extending parallel to the longitudinal axis of the cylinder, the cylinder rotating in use and able to translate longitudinally. There is a sensing arrangement including a stationary magnetised core and two coils connected in series and wound around the core. In use, the cylinder rotates and current is induced in the coils. Monitoring equipment is arranged to calculate rotational speed of the cylinder from the frequency of the current and to calculate longitudinal position from the relative amplitude of the current in each coil. Also a method.

Abstract: A method and arrangement of controlling blade pitch angle of a set of rotor blades. The method comprises providing a target blade pitch angle to a controller mounted on the rotor; measuring the speed of rotation of the rotor using a rate gyro mounted on the rotor; calculating the blade pitch angle required to match the target blade pitch angle by summing the target blade pitch angle and the measured rotational speed; and actuating the blades to the calculated blade pitch angle.

Abstract: A clearance control apparatus for controlling the clearance between a rotary assembly (17) and a casing (24) surrounding the rotary assembly (17) is disclosed. The clearance control apparatus comprises a temperature measuring device (34) to measure the temperature of a radially outer portion of the rotary assembly and a cooling arrangement (28) to cool the casing (24). A control system (36) is associated with the temperature measuring device (34) and the cooling arrangement (28) to control the extent of cooling of the casing (24). The extent of cooling is dependent upon the temperature of the aforesaid portion.

Abstract: A engine such as a gas turbine engine has a bladed rotor 24 having variable pitch blades 8. In normal operation, the pitch angle of the blades 8 is controlled by a primary pitch control system. A back-up system is provided for controlling the blades 8, for example to displace them to a feathered condition, in the event of failure of the primary pitch control system. The back-up system comprises a pump 32 mounted on the rotor 24, and driven by relative rotation between the rotor 24 and a contra-rotating rotor 23. In response to a failure signal on a conduit 48, the pump delivers hydraulic fluid under pressure to a secondary actuator 30, which acts on the blade 8.

Abstract: It is known that determination of bleed valve activation in a gas turbine engine can be difficult unless the engine is maintained at a steady idle state for comparison between that state and effects of activation of the bleed valve. Furthermore, specific test activation of bleed valves increases wear and tear on those valves. By sensing a flow pressure response signal and then through appropriate averaging and processing through a non-linear filter, it is possible to identify bleed valve activation by a target signal response exceeding a threshold indicative of such bleed valve activation.