Abstract: A fuel system for a gas turbine engine configured to combust hydrogen fuel is disclosed. The fuel system comprises a main fuel conduit and a fuel pump configured to operate on liquid hydrogen within the fuel conduit to provide pressurised fuel to a combustor of the gas turbine engine. A fuel metering unit is configured to control fuel flow delivered to the combustor. The fuel pump is configured to provide hydrogen at an outlet above a critical temperature and pressure, to thereby provide supercritical hydrogen fuel downstream. The fuel metering unit is configured to provide a variable flow area downstream of the pump, to deliver fuel at required flow parameters.

Abstract: An auxiliary power unit (10) for an aircraft (1) comprises a gas turbine engine comprising an engine core (12). The engine core comprises a core compressor (14) and core turbine (18) coupled by a core shaft (24). The auxiliary power unit further comprises a load spool comprising a load compressor (30), a load turbine (20) and a permanent magnet electric machine (28), each being coupled by a load shaft (26). The load shaft (26) and core shaft (24) are configured to rotate independently of one another.

Abstract: A turboshaft gas turbine engine comprises, in fluid flow series, a gas-generator compressor, a combustor, a gas-generator turbine, and a free power turbine. The expansion ratios of the turbines are dependent upon an outlet temperature of the combustor, and an expansion relationship between the turbines is defined as the ratio of expansion ratios of the turbines over a running range of non-dimensional power outputs of the gas turbine engine. A second derivative of the expansion relationship is from 0.6 to 1.0.

Abstract: A turboshaft gas turbine engine comprises, in fluid flow series, a gas-generator compressor, a combustor, a gas-generator turbine, and a free power turbine. The expansion ratios of the turbines are dependent upon an outlet temperature of the combustor, and an expansion relationship between the turbines is defined as the ratio of expansion ratios of the turbines over a running range of non-dimensional power outputs of the gas turbine engine. A second derivative of the expansion relationship is from 0.6 to 1.0.

Abstract: A turboshaft gas turbine engine comprises, in fluid flow series, a gas-generator compressor, a combustor, a gas-generator turbine, and a free power turbine. The gas-generator turbine is a single stage turbine having a specific work of from 200 to 350 kilojoules per kilogram, said specific work being the power output of the turbine per unit mass flow therethrough.

Abstract: An auxiliary power unit (10) for an aircraft (1) comprises a gas turbine engine comprising an engine core (12). The engine core comprises a core compressor (14) and core turbine (18) coupled by a core shaft (24). The auxiliary power unit further comprises a load spool comprising a load compressor (30), a load turbine (20) and a permanent magnet electric machine (28), each being coupled by a load shaft (26). The load shaft (26) and core shaft (24) are configured to rotate independently of one another.

Abstract: A turboshaft gas turbine engine comprises, in fluid flow series, a gas-generator compressor, a combustor, a gas-generator turbine, and a free power turbine. The rotational speeds of the turbines are dependent upon an outlet temperature of the combustor, and a speed relationship between the turbines is defined as the ratio of rotational speeds of the turbines over a running range of non-dimensional power outputs of the gas turbine engine. A first derivative of the speed relationship is from 0.9 to 1.

Abstract: A gas turbine engine (10) having a pressure-rise combustor (30) and the pressure-rise combustor (30) is positioned upstream of a stage of turbine nozzle guide vanes (32). The vanes (33) of the stage of turbine nozzle guide vanes (32) forms an ejector and each of the vanes (33) has an upstream portion (34) and a downstream portion (36). The upstream portions (34) of the vanes (33) have leading edges (38) and the upstream portions (34) are arranged substantially straight and parallel to define constant area mixing passages (40) for a flow of gases there-through. The downstream portions (36) of the vanes (33) are arranged at an angle to the upstream portions (34) of the vanes (33) to turn the flow of gases there-through.

Abstract: A method of operating an aircraft, and the aircraft itself, comprising a gas turbine engine that exhausts a plume of gases in use, the aircraft is characterized by comprising an electromagnetic radiation generator and a waveguide to direct electromagnetic radiation at the exhaust plume to avoid the formation of contrails.

Abstract: A gas turbine engine includes, in flow series, a generator section and a free power turbine. The generator section includes one or more generator turbine stages. One or more respective generator drive shafts extend axially forwardly from the generator turbine stages to one or more corresponding compressor stages. The free power turbine includes a first turbine stage and a contra-rotating second turbine stage. The gas turbine engine further includes a first drive shaft extending axially from the free power turbine to transmit rotational drive from the first turbine stage to a first propeller. The gas turbine engine further includes a second drive shaft extending from the free power turbine coaxially with the first drive shaft to transmit contra-rotational drive from the second turbine stage to a contra-rotating second propeller.

Abstract: Environmental concerns have resulted in consideration of the effects of condensation trails from gas turbine engines. By provision of a condensation stage in a heat exchanger arrangement for a gas turbine engine the level of condensation within a final exhaust gas flow G from an engine is reduced. Furthermore, by cooling of the exhaust gas flows for mixing with by-pass air flows a water partial pressure at an exhaust gas exit temperature can be provided which is below the eutectic liquid to vapor phase transition and therefore avoid condensation (contrail) formation.

Abstract: A rotor and a stator assembly, wherein the rotor (30) comprises at least one stage of rotor blades (32) and the stator (34) comprises at least one stage of turbine stator vanes (36). The rotor blades (32) have aerofoils and platforms (42) and the turbine stator vanes (36) having aerofoils and platforms (48). A seal (43,45) is defined between the rotor blade (32) platforms (42) and the stator vane (36) platforms (48) wherein a portion (42B) of the rotor blade platforms (42) and/or a portion (48B) of the stator vane (36) platforms (48) comprise a shape memory alloy member or a bimetallic member. The shape memory alloy member, or bimetallic member, controls the flow of cooling air through the seals (43,45) allowing a greater cooling flow at higher temperatures than at lower temperatures.

Abstract: A gas turbine engine (10) having a pressure-rise combustor (30) and the pressure-rise combustor (30) is positioned upstream of a stage of turbine nozzle guide vanes (32). The vanes (33) of the stage of turbine nozzle guide vanes (32) forms an ejector and each of the vanes (33) has an upstream portion (34) and a downstream portion (36). The upstream portions (34) of the vanes (33) have leading edges (38) and the upstream portions (34) are arranged substantially straight and parallel to define constant area mixing passages (40) for a flow of gases there-through. The downstream portions (36) of the vanes (33) are arranged at an angle to the upstream portions (34) of the vanes (33) to turn the flow of gases there-through.

Abstract: A method of operating an aircraft, and the aircraft itself, comprising a gas turbine engine that exhausts a plume of gases in use, the aircraft is characterised by comprising an electromagnetic radiation generator and a waveguide to direct electromagnetic radiation at the exhaust plume to avoid the formation of contrails.

Abstract: An aircraft comprising a gas turbine engine that exhausts a plume of gases in use, the aircraft comprises an ultrasound generator having an ultrasonic actuator and a waveguide to direct ultrasonic waves at the exhaust plume to avoid the formation of contrails.

Abstract: A method of operating a contra-rotating propeller engine that preferably comprises a 12 bladed front and a 9 bladed rear propeller. As is conventional, the engine is operated during at least a take-off phase, a cruise phase and an approach phase; during the cruise phase the engine operates with a generally constant propeller tip speed. The method is characterised by the step of operating the engine such that the tip speed of either or both of the propellers, during at least one of take-off, climb or approach, at least 10% greater than cruise tip speed. With a specific front to rear propeller spacing, increasing the tip speed reduces overall noise generated by the propellers.

Abstract: A gas turbine engine turbine comprises an annular array of nozzle guide vanes and an annular array of turbine blades mounted within its annular casing. An array of radially extending protrusions are positioned axially upstream of said array of said nozzle guide vanes and protruding inwardly from the inner casing wall so as to mix the tangential momentum component of the overtip leakage fluid flow before it reaches the array of nozzle guide vanes.

Abstract: A pressure rise combustor is provided with fuel provided at intermittent periods. The fuel is pulsed at timings such that the phase lag between the addition of the fuel and a resultant pressure rise is minimized. The fuel is pulsed such that the unsteady addition of heat reinforces the amplitude of an unsteady pressure fluctuation.

Abstract: A pressure rise combustor is provided with fuel provided at intermittent periods. The fuel is pulsed at timings such that the phase lag between the addition of the fuel and a resultant pressure rise is minimised. The fuel is pulsed such that the unsteady addition of heat reinforces the amplitude of an unsteady pressure fluctuation.

Abstract: A turbine engine arrangement is provided in which contra rotating shafts 104, 105 are respectively secured to a fan and a gearbox 106 which is also coupled to the shaft 104. In such circumstances the relative rotational speed ratio between the shafts 104, 105 can be determined with a first low pressure turbine 101 secured to the first shaft 104 arranged to rotate at a lower speed but provide high work whilst a second low pressure turbine 102 secured to the second shaft 105 rotates at a higher speed governed by the gearbox 106. By such an arrangement a smaller gearbox 106 may be used as less power is transferred through that gearbox 106 than with previous arrangements. By contra rotation of the turbines 101, 102 a lower flow deflection guide vane assembly 103 may be used and a further stator/guide vane assembly is not required between the turbines 101, 102.