Showing papers by "Rolls-Royce Limited published in 1981"

Apparatus for application of metallic coatings to metallic substrates

Abstract: A metallic coating is applied to a metallic substrate by directing a laser beam on to the substrate and simultaneously directing a gas stream containing entrained particles of the coating material on to the area of laser impingement on the substrate. The particles are melted by the laser beam to form a pool of molten coating metal. Relative movement is effected between the laser beam and substrate so that a pool of molten coating metal traverses the substrate to form a solidified metallic coating which is fused to the metallic substrate.

Combustion chamber for a gas turbine engine having a variable rate diffuser upstream of air inlet means

Abstract: A combustion chamber of a gas turbine engine has an upstream variable rate diffuser for controlling the airflow into first and second annular ducts which partially surround the combustion chamber, primary and dilution air flowing into the combustion chamber from the first annular duct and bypass air flowing into the combustion chamber from the second annular duct. The variable rate diffuser comprises a primary duct and downstream fence located in a secondary duct which has a bleed duct with a variable bleed rate, the outlet of the primary duct being smaller in diameter than the inlet to the first annular duct. In operation, by varying the bleed rate, the rate of diffusion into the combustion chamber can be varied, and if the bleed rate is reduced to low bleed conditions at high power conditions or to zero bleed condition at full power condition, vitiated air can be drawn from the combustion chamber and flowed in a reverse direction, upstream along the second annular duct and returned to the combustion chamber at its upstream end whereby the rate of combustion is reduced thereby reducing emissions of NOx.

Method of making an aerofoil member for a gas turbine engine

Abstract: A blade or vane structure for a gas turbine engine comprises a hollow aerofoil member and a cooling air entry tube within the hollow aerofoil member, the aerofoil and the tube comprising a unitary cast structure. To make this structure it is proposed that a lost wax casting process should be utilized, with the internal cavities formed using ceramic cores formed with the aid of temporary, disposable pieces which define the space eventually occupied by the tube.

Air sealing for turbomachines

Abstract: A stator assembly for a turbomachine having a sealing plate which co-operates with sealing members on an adjacent rotor assembly to form air seals. The sealing plate is provided with a thermal slugging mass, the thermal response of which controls the rate of expansion and contraction of the sealing plate to match that of the rotor. In this way tip clearances between the stationary and rotating parts of the air seals are maintained substantially uniform throughout all operating conditions of the turbomachine.

Oil system for aircraft gas turbine engine

Abstract: A fully aerobatic oil system for an aircraft gas turbine engine includes two re-circulatory oil systems the pumps for which have inlets 19 and 31a disposed at locations in the engine such that when one inlet is starved of oil, due to the aircraft attitude changing, oil will be supplied to the other one. In a specific embodiment, the breather of the oil system 30 (FIG. 2) is positioned in the engine gearbox and provides the lowest pressure point in the system. The breather is of the type described in UK Pat. No. 1,508,212 which includes a rotating compartment filled with RETIMET (Regd. Trade Mark). The bearing chambers are pressurised with air from the engine and the air/oil mixture in each chamber is vented via a first series of vents 24 to the breather where the air and oil are separated. The breather is used as a pump to pump the separated oil back to the oil tank via a scavenge line 35 which includes a relief valve 38. A bleed line 36 takes some of the oil from line 35 to the main oil supply gallery 23 via a non-return check valve 37. In normal flight pump 20 supplies the gallery 23 from the tank 18 via pump inlet 19, the relief valve 38 being set to a pressure lower than that of relief valve 40 which controls the pump pressure. The check valve 37 thus remains shut. When the inlet 19 is starved of oil because the flight attitude of the aircraft changes, the pressure in gallery 23 drops to the extent that check valve 37 opens and the breather/pump takes over circulating oil from the gearbox and bearings around the second system.

Wall structure for a combustion chamber

Abstract: A cooled wall structure for a gas turbine engine comprises a perforated and an inner wall in which the walls are capable of relative movement to cope with the thermal strains experienced by the combustion chamber during operation of the engine. The inner wall comprises a number of wall elements attached to the outer wall in the manner of overlapping tiles. Each wall element is immovably secured to the outer wall at the mid-point of its downstream end and the sides of each wall element are movably attached to the outer wall adjacent the sides of the downstream end of the wall element. The upstream end of each wall element is located between the outer wall and an adjacent flow in either an upstream or a downstream direction between the walls. The wall elements can have a plurality of raised lands to increase the surface area of the elements and to protect the incoming cooling air against the cross-flow of cooling air already flowing in the wall structure.

Gas turbine dual fuel burners

Abstract: A dual fuel burner for a gas turbine engine comprises a gas fuel manifold and ducts opening into a central air passage, a liquid fuel manifold and tangentially arranged apertures opening into an annular liquid fuel passage terminating in an annular nozzle. The central air passage has an upstream swirler, and is arranged to receive a flow of compressed air at its upstream end and to discharge a flow of compressed air and either gaseous or liquid fuel from its downstream end. The burner also has a water manifold so that water can be injected into the fuel and air flow via ducts and an annular air passage, to control NOx emission. In an alternative arrangement, the liquid fuel can be injected into the annular air passage. The burner is intended to operate on a range of high calorific fuels, both liquid and gaseous, and is designed to minimize the surface area on which carbon may accumulate during operation.

Multi-layer acoustic linings

Abstract: An acoustic lining for a flow duct has a first perforate skin fixed to an underlying sound-absorbing layer. The first perforate skin is overlain by a second perforate skin which forms the wall of the flow duct. One of the skins is relatively moveable in a sliding sense with respect to the other skin so as to vary the acoustic impedance of the duct wall as the perforations in the respective skins slide into and out of registration with each other. This enables the acoustic impedance of the duct wall to be varied to suit the flow and noise conditions prevailing in the duct and so obtain optimum noise attenuation in the duct, which may be the intake duct of a turbofan aeroengine.

Gas turbine engine having an automatic ice shedding spinner

Abstract: A gas turbine propulsion engine for aircraft of the type in which thrust is provided only from flow of exhaust gases or a combination of flow of exhaust gases and by-pass air, the engine having a cone-shaped spinner with a solid pointed tip portion and a main body portion. The tip portion has at least a surface made of a different material from the substantially rigid material of the main body portion, the at least surface of the tip portion being flexible relative to the body portion at operational rotations of the spinner whereby ice is automatically shed from the spinner due to cracks being developed at the bond between the tip portion and the main body portion. The cracks in the ice developed at the bond are propagated by the surface deflection of the remainder of the tip portion causing any accretion of ice thereon to shed from the remainder of the spinner.

Gas turbine engine seal

Abstract: A gas turbine engine is provided with an annular sealing element which is adapted to provide a gas seal between relatively rotatable gas turbine components. The sealing element is in the form of a woven fabric which has metallic warp filaments, metallic weft filaments and metallic warp pile filaments. The free ends of the warp pile filaments are non-looped. The sealing element is brazed to one of the gas turbine engine components so that the free ends of the warp pile filaments abut the other gas turbine engine component in sealing engagement.

Thermal barrier coating

Abstract: A thermal barrier coating adapted to provide a thermally insulating protective barrier on a component, the coating being capable of being applied to the components by spraying methods and being ductile when exposed to high temperatures. The coating comprises a mixture containing constituents of finely divided hollow glass microspheres; a ceramic frit of finely divided particles of alkali silicate titanate glass; and a refractory filler material of finely divided partiles such as micronized mica; aluminum oxide of mullite. All of the constituents of the mixture are suspended in a high temperature resistant binder material such as potassium silicate, sodium silicate or aluminum orthophosphate.

Single crystal castings

Abstract: An alloy composition intended for use in the form of a single crystal casting comprises a modified nickel-based superalloy. The alloy consists essentially of, by weight percent, 7-13% Chromium, 0-15% Cobalt, 1.25-3% Titanium+1/2 Niobium, 4.5-6.7% Aluminium, 3-12% Tungsten, 0-3.5% Molybdenum, 0-5% Tantalum, 0-2% Hafnium, 0-1.5% Vanadium, 0.015-0.05% Carbon, 0-0.01% Boron, 0-0.05% Zirconium, Balance essentially Nickel plus incidental impurities. The invention also contemplates a heat treatment for the alloy comprising initially heating to 1300°-1320° C. followed by cooling to room temperature and ageing the alloy at a temperature of about 870° C. for 16 hours.

Rotor drive systems

Abstract: A fan drive system comprising a main drive shaft 13 which drives the fan through a frangible coupling 27 and an auxilliary drive shaft 30 which by-passes the coupling 27. The auxilliary shaft 30 is pre-twisted elastically in the opposite direction to the direction of rotation of the main shaft 13, and is held in the pre-twisted state by the coupling 27. When the coupling 27 disconnects the drive from the main shaft 13, for example when the fan becomes unbalanced and transverse loads exceed a predetermined magnitude, the auxilliary shaft 30 unwinds. Unwinding of the shaft 30 cushions the fan against suddenly applied loads when the coupling 27 breaks and also reduces the loads on the coupling 27 during normal balanced running.

Variable stator vane operating mechanism for turbomachines

Abstract: A variable stator vane operating mechanism for a gas turbine engine includes a plurality of unison rings 21,22 and 23 each connected by a drag link 18,19 and 20 respectively to a pivoting beam 14. The unison rings are connected to each of vanes 10 in a stator vane row by first arms 24. In order to minimize side loads on the unison rings by the drag links during pivoting of the beam, the beam is connected at its free end to a second arm 30 which is pivotable about an axis 28 by means of a torque tube 26 or other suitable actuator, and the length of the second arm 30 between the axis 28 and its point of connection 44 to the beam is made as nearly as possible equal to the length of the first arms 24. By this means the fore and aft movement of the beam can be matched to the fore and aft movement of the unison rings, or at least in the case of one of them, and the drag links remain substantially in the plane of the unison rings.

Nozzle guide vane assemblies for turbomachines

Abstract: A nozzle guide vane assembly for a turbomachine comprises a plurality of segments mounted in an outer casing by means of pins which locate in slots. The slots are angled relative to radial planes so that the reaction force exerted by the pin normal to the length of the slot produces a tangential and radial force. The radial force opposes the couples produced on each segment by gas loads and the tangential reaction force.

Seal between a turbine rotor of a gas turbine engine and associated static structure of the engine

Abstract: A seal for use between the turbine rotor of a gas turbine engine and associated static structure comprises a ring of low-friction material which cooperates with the surface of the rotor to form an air bearing. The ring carries a sealing member which cooperates with a surface of the rotor to form a seal. The air bearing ensures that the sealing member is maintained at a constant spacing from the rotor, and this spacing may thus be maintained at a low value.

Vibration damped rotor blades for turbomachines

Abstract: A blade for a turbomachine having an aerofoil portion and a root portion. The blade is provided with a vibration damper for damping a predetermined vibration of the blade. The damper comprises a closed chamber 14 within the aerofoil portion 13 adjacent the tip of the blade, and liquid 15 within the chamber 14. The volume of liquid 15 is less than the volume of the chamber 14. The chamber 14 is shaped, positioned, and aligned relative to the blade, so that in use the liquid 15 is constrained to form a column which oscillates in the chamber 14 in radial directions and in the same directions as the vibration to be damped. The volume, mass, and viscosity of the liquid are all chosen in relation to the frequency vibration (W B ) of the vibration to be damped and the rotor speed (W E ) so that, in use, the length (L) of the column of liquid is such that ##EQU1## where R=the blade tip radius. In this way the liquid 15 is caused to oscillate, under centrifugal loads, at a natural frequency which matches, or is close to, the resonant frequency of the vibration to be damped.

Gas turbine engine air intake

Abstract: An air intake structure for a gas turbine engine comprising a duct having an air inlet at its upstream end for the engine and a generally mushroom-shaped center body. The duct and the center body have circular cross-sections throughout their lengths and are coaxial. The center body has a first stem portion extending into the duct and a second mushroom-shaped portion upstream of the air inlet of the duct, the mushroom-shaped portion having a maximum diameter greater than the diameter of the air inlet. An apertured wall circumferentially extends around the maximum diameter of the second portion of the center body, the apertures of the wall being so dimensioned as to cause any small liquid droplets flowing over the upstream face thereof to coalesce into larger liquid droplets. A step immediately downstream of the apertured wall causes the formed larger droplets to be launched from the center body in a trajectory which avoids the air inlet of the duct. The apertures are dimensioned so that each launched liquid droplet is of a mass sufficient to provide the desired trajectory.

System for supporting a rotor in a conditions of accidental dynamic imbalance

Abstract: The fan rotor (10) of a gas turbine engine is driven by a shaft (16) having a first part (16A) supported in a first radial bearing (17) for rotation about an axis (16C). The shaft (16) further has a second part (16B) secured to the rotor for transmitting torque thereto. The second part (16B) is flexible in bending to allow radial displacement of the rotor (10) relative to the bearing (17). Normally, the rotor (10) is supported against said displacement by a second radial bearing (23). If, due to damage, a given dynamic imbalance on the rotor (10) is exceeded, the resulting unbalanced force (F) transversely to the axis (16C) shears the pins (21C) of a coupling (21) provided between the rotor and the second bearing (23). This then permits the rotor (10) to move eccentrically with respect to the axis (16C) by virtue of the resilience of the shaft portion (16B) thereby cushioning the bearing (17) against the force (F).

Gas turbine engines

Abstract: A gas turbine engine blade tip seal consists of a sealing ring which is controlled by means of two annular control members The members are arranged such that one control member has a relatively rapid thermal response rate and the other control member has a relatively slow thermal response rate, the sealing ring being controlled such that a preferred tip clearance is maintained under varying engine operating conditions

The Protection of Gas Turbine Blades: A PLATINUM ALUMINIDE DIFFUSION COATING

Abstract: Turbine blades in gas turbine engines operate at elevated temperatures and in highly oxidising atmospheres that can be contaminated with fuel residues and sea water salts. These components, which are expensive to produce, are subjected to high stresses during operation but must be totally reliable during their design life. An economic way to maintain blade properties is to coat the base metal superalloy with a protective layer capable of resisting both high temperature oxidation and hot corrosion. Conventional aluminide coatings are widely used for this purpose but platinum aluminides offer improved corrosion resistance. A collaborative exercise involving Rolls‐Royce and Johnson Matthey has now resulted in the development of a platinum aluminide diffusion coating that offers some advantages over the commercial systems.

Method of manufacturing a composite material

Abstract: A method of manufacturing a composite material which comprises filaments enclosed in a matrix of a high temperature resistant thermoplastic polymer. The method entails impregnating the filament with a first high temperature resistant thermoplastic polymer in an amount sufficient only to lightly bind the fibres together. The bound fibres are then interposed between sheets of a second thermoplastic polymer and the whole structure subjected to heat and pressure for a time sufficient to ensure impregnation of said second thermoplastic polymer into said filaments and diffusion of the first thermoplastic polymer into the second thermoplastic polymer.

Electroplating of titanium and titanium base alloys

Abstract: A method of treating a titanium or titanium base alloy surface prior to the electroplating of a metal thereon in which the surface is immersed in a solution containing hydrofluoric acid, ammonium bifluoride and dimethylformamide. Reaction between the solution and the surface results in a coating being deposited on the surface which provides better adhesion between the surface and any metal subsequently electroplated thereon.

Thrust spoiler for aero engines

Abstract: A gas turbine engine terminates at its rear in a jet pipe (14) having a fixed area nozzle (15). The engine is provided with one or more target type deflector doors (18) which in a first position constitute a rearward extension of the jet pipe (14) and define an effective exhaust nozzle (19), downstream of the nozzle (15) of the jet pipe 18, which is of smaller area than that of the jet pipe. The door, or doors 18, are movable from the first position to a second position where the nozzle 15 of the jet pipe 14 is exposed and constitutes the effective exhaust nozzle of the engine. In the second position the door, or doors 18, lie predominantly transverse to the length of the jet pipe 14 to redirect the hot gas efflux from the jet pipe 14 and reduce the forward thrust produced by the engine.

Combustion equipment for a gas turbine engine

Abstract: Combustion equipment for a gas turbine engine operating on the pre-mix lean combustion bases comprises a flame tube having a plurality of alternately arranged main and pilot air ducts each having a respective fuel injector and receiving axially directed air from downstream of part span outlet guide vanes. The fuel and air in each duct are substantially pre-mixed before entry into the flame tube and the outlets of the pilot ducts direct the fuel and air mixture into the recirculation zone in a single vortex. At engine idle the air fuel ratio (AFR) is substantially stoichiometric to prevent the formation of unburnt hydrocarbons (UHC) and carbon monoxide (CO). As the engine accelerates the fuel flow to the pilot air ducts remains near constant so that the AFR in the re-circulation zone progressively weakens, and fuel is introduced into the main air ducts, the outlets of which direct the air fuel mixture into the flame tube with a substantial downstream component. The equivalence ratio of the main air fuel mixture is kept below 0.7 to keep NOx emissions at an acceptable level. Air direct from the engine compressor with a large swirl component is used to cool the flame tube walls with a high degree of effectiveness due to the scrubbing action of the air. Ducting for outer dilution air and bleed air can also be provided interdigitated with the main and pilot air ducting, and the flame tube can also have a catalyst block which allows the re-circulation zone to run weak at engine idle without excessive UHC and CO being produced.

Method of manufacture of an article having internal passages

Abstract: A method of manufacture of hollow turbine blades for gas turbine engines comprises forming them in two parts and brazing the parts together. This requires very accurate machining of the two faces of the parts which are to be joined prior to the brazing process. The invention provides a method of machining two confronting faces of parts of an article which are to be joined together. The method includes the step of passing an electrolyte linishing belt (2) FIG. 4 between the confronting surfaces of the two parts (10,11) and in contact with both faces simultaneously while passing an electric current between the parts. Thus one or both faces of the parts are machined using one as the former for the other.

Boundary Layer Studies on Highly Loaded Cascades using Heated Thin Films and a Traversing Probe

Abstract: In the continuing quest for increased turbine efficiency, the part played by blade profile shape remains crucial. Three turbine vanes with successively increased aerodynamic loading were tested in the High Speed Cascade Wind Tunnel at DFVLR Braunschweig. In addition to wake traverses, measurements of the boundary layer behavior were made. These consisted of: a) use of a constant temperature anemometer to measure the fluctuating heat transfer rate on an array of thin film platinum thermometers deposited on the vanes and b) a flattened, traversing pitot probe held against the vane surface. Transition measurement by these techniques is described.© 1980 ASME

Aerofoil blade mounting

Abstract: A blade assembly for use in an axial flow compressor or turbine. The blade assembly includes a disc provided with a circumferential blade root retaining channel in its periphery and an annular array of aerofoil blades having roots located in the channel so that gaps are defined between adjacent roots. Each root is provided with two circumferentially extending sealing skirts which are arranged so that they cooperate with the blade roots to define an annular sealing surface which is in operation in sealing engagement with an annular portion of the internal surface of the root retaining channel.

Manufacture of laminated material

Abstract: This invention relates to a method of manufacturing laminated material. Particularly to laminated materials for use in the construction of flame tubes of gas turbine engines. The laminated material is manufactured from three sheets, a central sheet, a first sheet, and a second sheet. The central sheet is perforated with an arrangement of equi-spaced apertures. The central sheet with apertures is then secured to the first sheet. A number of channels are machined through the central sheet to leave the first sheet and an arrangement of equi-spaced lands secured thereto. The first sheet is perforated with an arrangement of equi-spaced apertures to form air entry holes. The second sheet is then secured to the assembly to form a laminated material comprising a first sheet with apertures and second sheet separated by an arrangement of equi-spaced lands machined from central sheet.