US20210071583A1 - Electrical systems - Google Patents

Electrical systems Download PDF

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Publication number
US20210071583A1
US20210071583A1 US17/002,044 US202017002044A US2021071583A1 US 20210071583 A1 US20210071583 A1 US 20210071583A1 US 202017002044 A US202017002044 A US 202017002044A US 2021071583 A1 US2021071583 A1 US 2021071583A1
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United States
Prior art keywords
switch
gas turbine
converter circuit
switch array
spool
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US17/002,044
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English (en)
Inventor
Graham P. BRUCE
Stephen M. Husband
David F. BROOKES
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Rolls Royce PLC
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Rolls Royce PLC
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Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Assigned to ROLLS-ROYCE PLC reassignment ROLLS-ROYCE PLC ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUSBAND, Stephen M., BROOKES, DAVID F., BRUCE, Graham P.
Publication of US20210071583A1 publication Critical patent/US20210071583A1/en
Priority to US18/158,683 priority Critical patent/US20230160344A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/26—Starting; Ignition
    • F02C7/268—Starting drives for the rotor, acting directly on the rotor of the gas turbine to be started
    • F02C7/275—Mechanical drives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D27/00—Arrangement or mounting of power plants in aircraft; Aircraft characterised by the type or position of power plants
    • B64D27/02—Aircraft characterised by the type or position of power plants
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J1/00—Circuit arrangements for dc mains or dc distribution networks
    • H02J1/10—Parallel operation of dc sources
    • H02J1/102—Parallel operation of dc sources being switching converters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D15/00—Adaptations of machines or engines for special use; Combinations of engines with devices driven thereby
    • F01D15/10—Adaptations for driving, or combinations with, electric generators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C3/00—Gas-turbine plants characterised by the use of combustion products as the working fluid
    • F02C3/04—Gas-turbine plants characterised by the use of combustion products as the working fluid having a turbine driving a compressor
    • F02C3/107—Gas-turbine plants characterised by the use of combustion products as the working fluid having a turbine driving a compressor with two or more rotors connected by power transmission
    • F02C3/113—Gas-turbine plants characterised by the use of combustion products as the working fluid having a turbine driving a compressor with two or more rotors connected by power transmission with variable power transmission between rotors
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C6/00—Plural gas-turbine plants; Combinations of gas-turbine plants with other apparatus; Adaptations of gas-turbine plants for special use
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/26—Starting; Ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/32—Arrangement, mounting, or driving, of auxiliaries
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K11/00—Structural association of dynamo-electric machines with electric components or with devices for shielding, monitoring or protection
    • H02K11/30—Structural association with control circuits or drive circuits
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/14—Structural association with mechanical loads, e.g. with hand-held machine tools or fans
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
    • H02K7/1807—Rotary generators
    • H02K7/1823—Rotary generators structurally associated with turbines or similar engines
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K7/00—Arrangements for handling mechanical energy structurally associated with dynamo-electric machines, e.g. structural association with mechanical driving motors or auxiliary dynamo-electric machines
    • H02K7/18—Structural association of electric generators with mechanical driving motors, e.g. with turbines
    • H02K7/1807—Rotary generators
    • H02K7/1823—Rotary generators structurally associated with turbines or similar engines
    • H02K7/183—Rotary generators structurally associated with turbines or similar engines wherein the turbine is a wind turbine
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B64—AIRCRAFT; AVIATION; COSMONAUTICS
    • B64D—EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT
    • B64D27/00—Arrangement or mounting of power plants in aircraft; Aircraft characterised by the type or position of power plants
    • B64D2027/005—Aircraft with an unducted turbofan comprising contra-rotating rotors, e.g. contra-rotating open rotors [CROR]
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2220/00—Application
    • F05D2220/70—Application in combination with
    • F05D2220/76—Application in combination with an electrical generator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2230/00—Manufacture
    • F05D2230/20—Manufacture essentially without removing material
    • F05D2230/23—Manufacture essentially without removing material by permanently joining parts together
    • F05D2230/232—Manufacture essentially without removing material by permanently joining parts together by welding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T50/00—Aeronautics or air transport
    • Y02T50/50—On board measures aiming to increase energy efficiency

Definitions

  • This disclosure concerns electrical systems for connecting rotary electric machines with rotating machinery such as gas turbine spools.
  • one known aircraft configuration includes in its engines electric machines operable as both motors and generators so as to facilitate both generation of electrical power during flight but also starting of the engine and removal of the air-turbine starter.
  • One engine configuration for this known aircraft includes such electric machines coupled to the high-pressure spool of a twin-spool turbofan.
  • turbofans for airliners
  • vehicles such as electric vertical take-off and landing (EVTOL) aircraft
  • EVTOL electric vertical take-off and landing
  • Near term proposals are configured with redundant turboelectric generators for powering electric propellers.
  • the turboelectric generators are likely to be single-spool gas turbines.
  • the invention is directed towards electrical systems for connecting rotary electric machines with rotating machinery, which rotating machinery may comprise, for example, gas turbine spools.
  • rotating machinery may comprise, for example, gas turbine spools.
  • the invention is also directed towards a gas turbine comprising such electrical systems, and arrangements comprising two gas turbines and such electrical systems.
  • the electrical systems comprise:
  • a first dual-wound rotary electric machine mechanically coupled with a first gas turbine spool and comprising a first three-phase sub-machine and a second three-phase submachine;
  • a second dual-wound rotary electric machine mechanically coupled with a second gas turbine spool and comprising a third three-phase sub-machine and a fourth three-phase submachine;
  • the dc side of the first converter circuit is connected with the dc side of the third converter circuit
  • the dc side of the second converter circuit is connected with the dc side of the fourth converter circuit.
  • the dc side of the first converter circuit and the dc side of the third bidirectional converter circuit are connected to a first dc output bus;
  • the dc side of the second converter circuit and the dc side of the fourth bidirectional converter circuit are connected to a second dc output bus.
  • connection to the first dc output bus is via a first switch array, and the connection to the second dc output bus is via a second switch array.
  • bus tie across the first input and the second input, the bus tie comprising a third switch.
  • first switch array and the second switch array are configured to operate in a no-fault condition in which the first switch and the second switch are closed, and the third switch is opened.
  • first switch array and the second switch array are configured to operate in a first fault condition in which the second switch is closed, and the first switch and the third switch are opened.
  • first switch array and the second switch array are configured to operate in a second fault condition in which the first switch is closed, and the second switch and the third switch are opened.
  • first switch array and the second switch array are configured to operate in a third fault condition in which the third switch is closed, and the first switch and the second switch are opened.
  • the switches are dc contactors.
  • a gas turbine engine having a low-pressure spool and a high-pressure spool, and further comprising the electrical system of the aforesaid type, in which the first gas turbine spool is the low-pressure spool and the second gas turbine spool is the high-pressure spool.
  • an arrangement comprising:
  • the electrical system of the aforesaid type in which the first gas turbine spool is the first spool of the first gas turbine engine, and the second gas turbine spool is the second spool of the second gas turbine engine.
  • FIG. 1 shows a general arrangement of a turbofan engine for an aircraft, including a rotary electric machine on each spool thereof;
  • FIG. 2 shows an electrical system for connecting the electric machines of FIG. 1 ;
  • FIG. 3 is a schematic of the dual-wound electric machines of FIG. 1 ;
  • FIG. 4 is a single line diagram of an embodiment of the electrical system of FIG. 2 ;
  • FIG. 5 is a single line diagram of one of the switching arrays of FIG. 4 .
  • FIG. 1 A first figure.
  • FIG. 1 A general arrangement of an engine 101 for an aircraft is shown in FIG. 1 .
  • the engine 101 is of turbofan configuration, and thus comprises a ducted fan 102 that receives intake air A and generates two pressurised airflows: a bypass flow B which passes axially through a bypass duct 103 and a core flow C which enters a core gas turbine.
  • the core gas turbine comprises, in axial flow series, a low-pressure compressor 104 , a high-pressure compressor 105 , a combustor 106 , a high-pressure turbine 107 , and a low-pressure turbine 108 .
  • the core flow C is compressed by the low-pressure compressor 104 and is then directed into the high-pressure compressor 105 where further compression takes place.
  • the compressed air exhausted from the high-pressure compressor 105 is directed into the combustor 106 where it is mixed with fuel and the mixture is combusted.
  • the resultant hot combustion products then expand through, and thereby drive, the high-pressure turbine 107 and in turn the low-pressure turbine 108 before being exhausted to provide a small proportion of the overall thrust.
  • the high-pressure turbine 107 drives the high-pressure compressor 105 via an interconnecting shaft.
  • the low-pressure turbine 108 drives the low-pressure compressor 104 via another interconnecting shaft.
  • the high-pressure compressor 105 , high-pressure turbine 107 , and associated interconnecting shaft form part of a high-pressure spool of the engine 101 .
  • the low-pressure compressor 104 , low-pressure turbine 108 , and associated interconnecting shaft form part of a low-pressure spool of the engine 101 .
  • Such nomenclature will be familiar to those skilled in the art.
  • the fan 102 is driven by the low-pressure turbine 108 via a reduction gearbox in the form of a planetary-configuration epicyclic gearbox 109 .
  • the low-pressure turbine 108 is connected with a sun gear of the gearbox 109 .
  • the sun gear is meshed with a plurality of planet gears located in a rotating carrier, which planet gears are in turn are meshed with a static ring gear.
  • the rotating carrier drives the fan 102 via a fan shaft 110 .
  • a first rotary electric machine 111 capable of operating both as a motor and generator is mechanically coupled with the high-pressure spool.
  • the first electric machine 111 is coupled to the high-pressure spool via a high-pressure spool driven, core-mounted accessory gearbox 112 of conventional drive configuration.
  • the first electric machine 111 may drive the high-pressure spool to facilitate starting of the engine 101 in place of an air turbine starter, and may also drive it in certain flight phases to improve operability, fuel consumption, etc.
  • the first electric machine 111 may be mounted coaxially with the turbomachinery in the engine 101 .
  • the first electric machine 111 may be mounted axially in line with the duct between the low- and high-pressure compressors 104 and 105 .
  • a second rotary electric machine 113 capable of operating both as a motor and generator is mechanically coupled with the low-pressure spool.
  • the second electric machine 113 is mounted in the tail cone 114 of the engine 101 coaxially with the turbomachinery and is coupled to the low-pressure turbine 108 .
  • the second rotary electric machine 113 may be located axially in line with low-pressure compressor 104 , which may adopt a bladed disc or bladed drum configuration to provide space for the second rotary electric machine 113 .
  • the first and second electric machines are connected with power electronics. Extraction of power from, or application of power to the electric machines is performed by a power electronics module (PEM) 115 .
  • PEM power electronics module
  • the PEM 115 is mounted on the fan case 116 of the engine 101 , but it will be appreciated that it may be mounted elsewhere such as on the core gas turbine, or in the vehicle to which the engine 101 is attached, for example.
  • Control of the PEM 115 and of the first and second electric machines 111 and 113 is in the present example performed by an engine electronic controller (EEC) 117 .
  • EEC engine electronic controller
  • the EEC 117 is a full-authority digital engine controller (FADEC), the configuration of which will be known and understood by those skilled in the art. It therefore controls all aspects of the engine 101 , i.e. both of the core gas turbine and the first and second electric machines 111 and 113 . In this way, the EEC 117 may holistically respond to both thrust demand and electrical power demand.
  • FADEC full-authority digital engine controller
  • the internal configuration of PEM 115 guarantees fault-tolerant transfer of electric power between the first electric machine 111 and second electric machine 113 .
  • the turbomachinery may be designed to exploit the attendant advantages conferred by transfer of power between the high-pressure spool and the low-pressure spool. For example, transfer of power from the low-pressure spool to the high-pressure spool during the approach phase reduces the effective thrust of the engine 101 whilst maintaining sufficient high-pressure spool rotational speed to safely initiate a go-around manoeuvre. Further, in engine 101 , transfer of power from the high-pressure spool to the low-pressure spool during a deceleration manoeuvre reduces the risk of weak extinction, therefore enabling a more optimal combustor design.
  • the PEM 115 is configured such that it may output to or receive electrical power from two dc busses—a configuration contemplated for future more electric aircraft platforms. The configuration of this electrical system will be described with reference to FIG. 2 .
  • Various embodiments of the engine 101 may include one or more of the following features.
  • the engine 101 may instead be a turboprop comprising a propeller for producing thrust.
  • the low- and high-pressure compressors 104 and 105 may comprise any number of stages, for example multiple stages. Each stage may comprise a row of rotor blades and a row of stator vanes, which may be variable stator vanes (in that their angle of incidence may be variable). In addition to, or in place of, axial stages, the low-or high-pressure compressors 104 and 105 may comprise centrifugal compression stages.
  • the low- and high-pressure turbines 107 and 108 may also comprise any number of stages.
  • the fan 102 may have any desired number of fan blades, for example 16, 18, 20, or 22 fan blades.
  • Each fan blade may be defined as having a radial span extending from a root (or hub) at a radially inner gas-washed location, or 0 percent span position, to a tip at a 100 percent span position.
  • the hub-tip ratio may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the hub-tip ratio may both be measured at the leading edge (or axially forwardmost) part of the blade.
  • the hub-tip ratio refers, of course, to the gas-washed portion of the fan blade, i.e. the portion radially outside any platform.
  • the radius of the fan 102 may be measured between the engine centreline and the tip of a fan blade at its leading edge.
  • the fan diameter may be greater than (or on the order of) any of: 2.5 metres, 2.6 metres, 2.7 metres, 2.8 metres, 2.9 metres, 3 metres, 3.1 metres, 3.2 metres, 3.3 metres, 3.4 metres, 3.5 metres, 3.6 metres, 3.7 metres, 3.8 metres or 3.9 metres.
  • the fan diameter may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the rotational speed of the fan 102 may vary in use. Generally, the rotational speed is lower for fans with a higher diameter. Purely by way of non-limitative example, the rotational speed of the fan at cruise conditions may be less than 2500 rpm, for example 2300 rpm. Purely by way of further non-limitative example, the rotational speed of the fan 102 at cruise conditions for an engine having a fan diameter in the range of from 2.5 metres to 3 metres (for example 2.5 metres to 2.8 metres) may be in the range of from 1700 rpm to 2500 rpm, for example in the range of from 1800 rpm to 2300 rpm, or, for example in the range of from 1900 rpm to 2100 rpm.
  • the rotational speed of the fan at cruise conditions for an engine having a fan diameter in the range of from 3.2 metres to 3.8 metres may be in the range of from 1200 rpm to 2000 rpm, for example in the range of from 1300 rpm to 1800 rpm, for example in the range of from 1400 rpm to 1600 rpm.
  • the fan 102 In use of the engine 101 , the fan 102 (with its associated fan blades) rotates about a rotational axis. This rotation results in the tip of the fan blade moving with a velocity U tip .
  • the work done by the fan blades on the flow results in an enthalpy rise dH of the flow.
  • a fan tip loading may be defined as dH/U tip 2 , where dH is the enthalpy rise (for example the one-dimensional average enthalpy rise) across the fan and U tip is the (translational) velocity of the fan tip, for example at the leading edge of the tip (which may be defined as fan tip radius at leading edge multiplied by angular speed).
  • the fan tip loading at cruise conditions may be greater than (or on the order of) any of: 0.3, 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39 or 0.4.
  • the fan tip loading may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • the engine 101 may have any desired bypass ratio, where the bypass ratio is defined as the ratio of the mass flow rate of the flow B through the bypass duct to the mass flow rate of the flow C through the core at cruise conditions. Depending upon the selected configuration, the bypass ratio may be greater than (or on the order of) any of the following: 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, or 17.
  • the bypass ratio may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the bypass duct may be substantially annular.
  • the bypass duct may be radially outside the core engine 103 .
  • the radially outer surface of the bypass duct may be defined by a nacelle and/or a fan case.
  • the overall pressure ratio of the engine 101 may be defined as the ratio of the stagnation pressure upstream of the fan 102 to the stagnation pressure at the exit of the high-pressure compressor 105 (before entry into the combustor).
  • the overall pressure ratio of the engine 101 at cruise may be greater than (or on the order of) any of the following: 35, 40, 45, 50, 55, 60, 65, 70, 75.
  • the overall pressure ratio may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • Specific thrust of the engine 101 may be defined as the net thrust of the engine divided by the total mass flow through the engine 101 .
  • the specific thrust of the engine 101 may be less than (or on the order of) any of the following: 110 Nkg ⁇ 1 s, 105 Nkg ⁇ 1 s, 100 Nkg ⁇ 1 s, 95 Nkg ⁇ 1 s, 90 Nkg ⁇ 1 s, 85 Nkg ⁇ 1 s, or 80 Nkg ⁇ 1 s.
  • the specific thrust may be in an inclusive range bounded by any two of the values in the previous sentence (i.e. the values may form upper or lower bounds).
  • Such engines may be particularly efficient in comparison with conventional gas turbine engines.
  • the engine 101 may have any desired maximum thrust.
  • the engine 101 may be capable of producing a maximum thrust of at least (or on the order of) any of the following: 160 kilonewtons, 170 kilonewtons, 180 kilonewtons, 190 kilonewtons, 200 kilonewtons, 250 kilonewtons, 300 kilonewtons, 350 kilonewtons, 400 kilonewtons, 450 kilonewtons, 500 kilonewtons, or 550 kilonewtons.
  • the maximum thrust may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the thrust referred to above may be the maximum net thrust at standard atmospheric conditions at sea level plus 15 degrees Celsius (ambient pressure 101.3 kilopascals, temperature 30 degrees Celsius), with the engine 101 being static.
  • the temperature of the flow at the entry to the high-pressure turbine 107 may be particularly high.
  • This temperature which may be referred to as turbine entry temperature or TET, may be measured at the exit to the combustor 106 , for example immediately upstream of the first turbine vane, which itself may be referred to as a nozzle guide vane.
  • the TET may be at least (or on the order of) any of the following: 1400 kelvin, 1450 kelvin, 1500 kelvin, 1550 kelvin, 1600 kelvin or 1650 kelvin.
  • the TET at cruise may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the maximum TET in use of the engine 101 may be, for example, at least (or on the order of) any of the following: 1700 kelvin, 1750 kelvin, 1800 kelvin, 1850 kelvin, 1900 kelvin, 1950 kelvin or 2000 kelvin.
  • the maximum TET may be in an inclusive range bounded by any two of the aforesaid values (i.e. the values may form upper or lower bounds).
  • the maximum TET may occur, for example, at a high thrust condition, for example at a maximum take-off (MTO) condition.
  • MTO maximum take-off
  • a fan blade and/or aerofoil portion of a fan blade described and/or claimed herein may be manufactured from any suitable material or combination of materials.
  • at least a part of the fan blade and/or aerofoil may be manufactured at least in part from a composite, for example a metal matrix composite and/or an organic matrix composite, such as carbon fibre.
  • at least a part of the fan blade and/or aerofoil may be manufactured at least in part from a metal, such as a titanium-based metal or an aluminium based material (such as an aluminium-lithium alloy) or a steel-based material.
  • the fan blade may comprise at least two regions manufactured using different materials.
  • the fan blade may have a protective leading edge, which may be manufactured using a material that is better able to resist impact (for example from birds, ice or other material) than the rest of the blade.
  • a leading edge may, for example, be manufactured using titanium or a titanium-based alloy.
  • the fan blade may have a carbon-fibre or aluminium-based body with a titanium leading edge.
  • the fan 102 may comprise a central hub portion, from which the fan blades may extend, for example in a radial direction.
  • the fan blades may be attached to the central portion in any desired manner.
  • each fan blade may comprise a fixture which may engage a corresponding slot in the hub.
  • such a fixture may be in the form of a dovetail that may slot into and/or engage a corresponding slot in the hub/disc in order to fix the fan blade to the hub.
  • the fan blades maybe formed integrally with a central hub portion.
  • Such an arrangement may be a bladed disc or a bladed ring. Any suitable method may be used to manufacture such a bladed disc or bladed ring.
  • at least a part of the fan blades may be machined from a billet and/or at least part of the fan blades may be attached to the hub/disc by welding, such as linear friction welding.
  • the engine 101 may be provided with a variable area nozzle (VAN). Such a variable area nozzle may allow the exit area of the bypass duct to be varied in use.
  • VAN variable area nozzle
  • the general principles of the present disclosure may apply to engines with or without a VAN.
  • cruise conditions may be conventionally defined as the conditions at mid-cruise, for example the conditions experienced by the aircraft and/or engine at the midpoint (in terms of time and/or distance) between top of climb and start of descent.
  • Cruise conditions thus define an operating point of the gas turbine engine which provides a thrust that would ensure steady state operation (i.e. maintaining a constant altitude and constant Mach number) at mid-cruise of an aircraft to which it is designed to be attached, taking into account the number of engines provided to that aircraft. For example, where an engine is designed to be attached to an aircraft that has two engines of the same type, at cruise conditions the engine provides half of the total thrust that would be required for steady state operation of that aircraft at mid-cruise.
  • cruise conditions are defined as the operating point of the engine that provides a specified thrust (required to provide—in combination with any other engines on the aircraft—steady state operation of the aircraft to which it is designed to be attached at a given mid-cruise Mach number) at the mid-cruise atmospheric conditions (defined by the International Standard Atmosphere according to ISO 2533 at the mid-cruise altitude).
  • the mid-cruise thrust, atmospheric conditions and Mach number are known, and thus the operating point of the engine at cruise conditions is clearly defined.
  • the cruise conditions may correspond to ISA standard atmospheric conditions at an altitude that is in the range of from 10000 to 15000 metres, such as from 10000 to 12000 metres, or from 10400 to 11600 metres (around 38000 feet), or from 10500 to 11500 metres, or from 10600 to 11400 metres, or from 10700 metres (around 35000 feet) to 11300 metres, or from 10800 to 11200 metres, or from 10900 to 11100 metres, or 11000 metres.
  • the cruise conditions may correspond to standard atmospheric conditions at any given altitude in these ranges.
  • the forward speed at the cruise condition may be any point in the range of from Mach 0.7 to 0.9, for example one of Mach 0.75 to 0.85, Mach 0.76 to 0.84, Mach 0.77 to 0.83, Mach 0.78 to 0.82, Mach 0.79 to 0.81, Mach 0.8, Mach 0.85, or in the range of from Mach 0.8 to 0.85. Any single speed within these ranges may be the cruise condition. For some aircraft, the cruise conditions may be outside these ranges, for example below Mach 0.7 or above Mach 0.9.
  • the cruise conditions may correspond specifically to a pressure of 23 kilopascals, a temperature of minus 55 degrees Celsius, and a forward Mach number of 0.8.
  • FIG. 2 An electrical system 201 for connecting the first and second electric machines 111 and 113 to the high- and low-pressure spools is shown in FIG. 2 .
  • the electrical system 201 is shown in the form of a single line diagram, the conventions of which will be familiar to those skilled in the art. Thus for alternating current (ac) a single line replaces a plurality of polyphase lines, and for direct current (dc) a single line replaces the +V and ⁇ V lines.
  • the ac output of the electric machines is provided to the PEM 115 .
  • the configuration of the electric machines will be described further with reference to FIG. 3 .
  • a controller 202 for the PEM 115 is provided in the EEC 117 .
  • the controller 202 is a functional module implemented in software running on the EEC 117 . It will be appreciated that in alternative embodiments the controller 202 may be implemented in hardware in the EEC 117 . It will also be appreciated that the controller 202 may be a separate module in addition to the EEC 117 .
  • a first set of bidirectional converter circuits 203 is connected with the first electric machine 111
  • a second set of bidirectional converter circuits 204 is connected with the second electric machine 113 .
  • the controller 202 is configured to control the operation of the first and second sets of bidirectional converter circuits 203 and 204 so as to control the operation of the electric machines 111 and 113 .
  • the bidirectional converter circuits are configured to convert alternating current to and from direct current.
  • the direct current output of the converter circuits is provided to a switching arrangement 205 for connection to a two-channel aircraft dc network, comprising a first dc bus 206 and a second dc bus 207 .
  • the switching circuit is operable to connect or disconnect the bidirectional converters to each other, and the dc busses. In this way, various faults may be managed as will be described further with reference to FIG. 5 , whilst maintaining the capability to transfer power between the gas turbine spools.
  • the first electric machine 111 is shown in FIG. 3 .
  • the configuration—so far as described herein—of the second electric machine 113 is the same.
  • the first electric machine 111 is a dual-wound rotary electric machine.
  • the term “dual-wound” will be understood by those skilled in the art to mean that it may be considered to comprise two functionally separate submachines. Further, in the present implementation, these submachines are three-phase submachines. It will be appreciated that the number of phases could differ, and in particular may be greater than two. The maximum number is typically limited by space constraints, and would normally be less than nine.
  • the first electric machine 111 comprises a stator 301 having twelve teeth 302 .
  • Six coils 303 , 304 , 305 , 306 , 307 , and 308 are wound on alternate teeth such that there is only one coil side per slot. This will be recognised by those skilled in the art as a concentrated winding arrangement.
  • the coils are electrically, electromagnetically, thermally, and mechanically separated to provide fault-tolerance.
  • the “dual-winding” of the first electric machine 111 is achieved by designating opposite coils as part of separate submachines.
  • coil 303 forms a phase ⁇ U 1
  • coil 306 forms a phase ⁇ U 2 .
  • Phases ⁇ U 1 , ⁇ V 1 , and ⁇ W 1 which form a first submachine are in the present embodiment connected in a star winding (also known as a wye winding), as are—in a separate connection—phases ⁇ U 2 , ⁇ V 2 and ⁇ W 2 which form the second submachine. It will be appreciated that a delta winding may be used instead.
  • the first electric machine 111 is a permanent magnet electric machine.
  • magnetic fields generated by the coils 303 to 308 interact with permanent magnets on a rotor 309 which generates torque.
  • the magnetic field of the rotor 309 interacts with the coils 303 to 308 to generate a voltage.
  • machines of induction, wound-field or switched-reluctance type may be used. Further, the machines may instead be of transverse- or axial-flux configuration.
  • the submachines may be formed not by different winding sets wound around the same stator 301 , but by axially separate machines each having one of the two windings of the dual winding.
  • the machines may be of radially-segmented stator type in which each submachine occupies a different sector of the stator.
  • the electrical system 201 is shown in more detail in FIG. 4 , again in the form of a single line diagram.
  • Each electric machine 111 and 113 has a three-phase connection for each of the submachines to a respective bidirectional converter circuit.
  • a first submachine 111 - 1 in the first electric machine 111 (corresponding to phases ⁇ U 1 , ⁇ V 1 , and ⁇ W 1 thereof) is connected with a first bidirectional converter circuit 401 .
  • a second submachine 111 - 2 in the first electric machine 111 (corresponding to phases ⁇ U 2 , ⁇ V 2 , and ⁇ W 2 thereof) is connected with a second bidirectional converter circuit 402 .
  • a third submachine 113 - 1 in the second electric machine 113 (corresponding to phases ⁇ U 1 , ⁇ V 1 , and ⁇ W 1 thereof) is connected with a third bidirectional converter circuit 403 .
  • a fourth submachine 113 - 2 in the second electric machine 113 (corresponding to phases ⁇ U 2 , ⁇ V 2 , and ⁇ W 2 thereof) is connected with a fourth bidirectional converter circuit 404 .
  • the bidirectional converter circuits 401 to 404 are two-level converters comprising three half-bridge converter legs along with appropriate filters.
  • other converter topologies may be used, such as neutral-point clamped topologies.
  • switching arrangement 205 is split into two separate switch arrays 405 and 406 which facilitates fault tolerant isolation of the first submachines and the second submachines.
  • the dc sides of the first and third bidirectional converter circuits 401 and 403 are connected together by a first switch array 405
  • the dc sides of the first and third bidirectional converter circuits 401 and 403 are connected together by a second switch array 406 .
  • the first switch array 405 connects to the dc sides of the first and third bidirectional converter circuits 401 and 403 to the first dc bus 206
  • the second switch array 406 connects to the dc sides of the second and fourth bidirectional converter circuits 402 and 404 to the second dc bus 207 .
  • the first switch array 405 is shown in greater detail in FIG. 5 , again in the form of a single line diagram.
  • the second switch array 406 is of the same configuration.
  • the switch array 405 comprises a first input 501 for connection with one of the converter circuits, a second input 502 for connection with another one of the converter circuits, and an output 503 for connection with a dc output bus.
  • the first input 501 is connected with the first bidirectional converter circuit 401
  • the second input 502 is connected with the third bidirectional converter circuit 403 .
  • the output 503 is connected with the first dc bus 206 . Both the first input 501 and the second input 502 are connected to the output 503 .
  • the second switch array 406 which in this example is of the same configuration, its first input 501 is connected with the second bidirectional converter circuit 402 , its second input 502 is connected with the fourth bidirectional converter circuit 404 , and its output 503 is connected with the second dc bus 207 .
  • a first switch 504 is provided between the first input 501 and the output 503
  • a second switch 505 is provided between the second input 502 and the output 503
  • a third switch 506 is provided in a bus tie across the first input 501 and second input 502 .
  • each switch 504 to 506 may be configured with the same voltage and current rating, and thus may be provided as identical parts.
  • the switches 504 to 506 are dc contactors, which as will be familiar to those skilled in the art are electrically-controlled switches used for switching an electrical power circuit, where the control circuit has a lower power level than the switched circuit.
  • the power levels may be in excess of 500 kilowatts at 540 volts dc.
  • the switches 504 to 506 operate under the control of controller 201 , which provides respective control signals Q 1 , Q 2 , and Q 3 to the switches. In this way, it is possible to isolate any one of the inputs and output during a fault condition and to continue to operate the rest of the electrical system 201 .
  • the fault may be any type of fault which risks the safe operation of the system, for example a short circuit or an earth fault.
  • Such faults may be sensed by the controller 201 on the basis of a measurement of any of current flow or voltage of each phase.
  • the fault may be sensed using one or more of overcurrent protection, ground (earth) fault protection, unit (or differential) protection and negative phase sequence protection.
  • the fault may be sensed by one or more of a current transformer and a voltage transformer, or digital equivalents.
  • the primary mode of operation is the no-fault condition.
  • the first fault condition is the existence of a fault between the first submachine 111 - 1 in the first electric machine 111 and the first bidirectional converter circuit 401 .
  • the second fault condition is the existence of a fault between the third submachine 113 - 1 in the second electric machine 113 and the third bidirectional converter circuit 403 .
  • the third fault condition is the existence of a fault on the first dc bus 206 .
  • Control signals Qn associated with these fault conditions are set out in Table 1 below, in which a “0” indicates an open switch, and a “1” indicates a closed switch:
  • the switches 504 to 506 are configured to isolate the faulted part of the electrical system 201 from the remaining, operational parts. Power transfer between the gas turbine spools is possible even in the presence of a fault on the first dc bus 206 by provision of switch 506 in the bus tie across the first input 501 and second input 502 , which is closed by the controller in the third fault condition.
  • the primary mode of operation is the no-fault condition.
  • the first fault condition is the existence of a fault between the second submachine 111 - 2 in the first electric machine 111 and the second bidirectional converter circuit 402 .
  • the second fault condition is the existence of a fault between the fourth submachine 113 - 2 in the second electric machine 113 and the fourth bidirectional converter circuit 404 .
  • the third fault condition is the existence of a fault on the second dc bus 206 .
  • the electrical system configuration described herein may be extended to facilitate connection of rotary electric machines with other types of rotating machinery.
  • the rotary electric machines may be connected with other types of heat engines, for example internal combustion engines such as reciprocating or Wankel-type engines.
  • Other types of heat engines such as steam turbines operating according to the Rankine cycle may be connected.
  • Combinations of different types of rotating machinery may be connected.

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