Showing papers by "Rolls-Royce Limited published in 1983"

Fuel control system for a gas turbine engine

Abstract: A fuel control system for a gas turbine engine comprises a main fuel controller and an overspeed limiter arranged to prevent overspeed of the engine in the case of a fault in the main controller To ensure that the limiter is tested regularly, the logic capacity of the main controller (which is preferably a digital electronic unit) is used to vary the parameters of the limiter each time the engine is started up This variation is such as to cause the limiter to operate and produce an observable reduction in the engine speed which is detected by the main controller and uses as an indication of correct limiter operation

Method of manufacturing articles from a composite material

Abstract: A method of vacuum moulding a composite material in which laid-up prepregs uncured resin and reinforcing filaments are placed on a heated former and covered with a sheet of a microporous film material a breather material and an impermeable membrane. The volume enclosed by the membrane is evacuated and the temperature of the mould increased to firstly outgas the resin and mould the prepregs to the shape of the former and finally cure the resin. The arrangement ensures excellent access of the prepregs to the vacuum during the moulding operation, thereby in turn ensuring that the resultant moulded article has very low porosity as a result of gas or vapor inclusions or is porosity-free.

Exhaust mixing in turbofan aeroengines

Abstract: The core engine of a mixed exhaust turbofan aeroengine is provided with a conical afterbody. The normal outlet guide vanes which remove residual swirl from the turbine exhaust gases are dispensed with and replaced by ducts within an afterbody having entries which receive the hot gases in the same manner and at the same angle as the passages between the guide vanes would have done. The hot ducts, whose aspect ratio is preferably transformed between their upstream and downstream ends, extend through the afterbody in substantially straight paths to avoid aerodynamic losses, and intersect its conical surface to form preferably slot-like nozzles from which the turbine exhaust gases issue as flattened jets. The exhaust jets partake of the original axial and tangential/swirl velocity components of the turbine gases, plus a radial component (consequential upon the orientation of the ducts) to achieve good penetration of the bypass stream. Satisfactory mixing between the bypass stream and the jets is achieved because of the radial and tangential velocity components and because the bypass stream flows in sheets between the jets. No net swirl in the mixed stream through the propulsion nozzle is ensured by counter-swirling of the bypass stream before mixing commences.

Shroud assembly for a gas turbine engine

Abstract: A shroud assembly for a gas turbine engine consists of a housing having a boundary wall and a gas contacting skin, the wall and skin being in segmented form. The skin consists of a thin metal sheet attached to the boundary wall, and a ceramic gas contacting coating. The skin is impingement cooled by cooling air flowing through apertures in the boundary wall, and the cooling air exhausts into the gas flow through passages. The use of a thin metal sheet with a ceramic coating promotes favorable temperature gradients in the skin enabling the coating to run at optimum conditions for maximum cooling effect.

Cooled turbine blade for a gas turbine engine

Abstract: A cooled turbine blade is provided with an aerofoil which tapers from root end to tip end so that the thicker root section provides greater resistance to detachment of the aerofoil. In order to provide effective cooling and light weight the aerofoil has a central `dead` cavity which extends from its root and part way up the aerofoil. Spanwise cooling passages bifurcate to pass between the cavity and the side walls in the relatively constant metal thickness thus provided.

Turbine overspeed limiter for turbomachines

Abstract: A mechanism 25 for preventing a turbine rotor 14 from exceeding a predetermined speed if a shaft 24, connecting the turbine rotor 14 to a compressor rotor 12 of the engine, breaks and releases its axial and torsional constraint on the turbine rotor 14. The mechanism 25 comprises a segmented stator vane assembly 26 downstream of a stage of the turbine rotor 14. Each segment 26 has first and second members 38,40 projecting radially inwards. The first and second members 38,40 are provided respectively at an upstream and downstream region of the inner end of each segment 26. A constraining means 34,36 is provided to constrain the segments 26 against displacement bodily on an axial direction. Static structure of the engine 56 engages the first and second members 38,40 and provides radially outwards and axially rearwards constraint on the first members 38 and radially inwards and axially forwards constraint on the second member 40. When the shaft 24 breaks and the turbine rotor 14 strikes the structure 56 in an axial direction, the structure 56 constrains the first members 38 of each segment 26 and provides a fulcrum about which the segments 26 rotate. Simultaneously the axial and radial constraint on the second members 40 is released causing the gas loads on the segments 26 to tilt then about the fulcrum into the path of the turbine rotor blades.

Aerofoil for a gas turbine engine

Abstract: An aerofoil, particularly a nozzle guide vane, for a gas turbine engine comprises a hollow interior with an air guide tube located therein. The air guide tube has apertures therein, and in order to cause the free edges of the apertures to seal against internal ribs of the aerofoil, springs are provided to force the open edges apart. Conveniently the springs comprise straps between the apertures which are formed with a corrugated shape.

Stator vane for a gas turbine engine

Abstract: A vane for a gas turbine engine has an aerofoil of unconventional shape. The stacking of sections which defines the aerofoil is arranged to produce an aerofoil whose concave flank is convex in spanwise sections and whose convex flank is concave in spanwise sections. In order to reduce the problems produced by the resulting shape of trailing edge the sections are stacked so that all their trailing edges lie in a plane substantially parallel with the plane of the throat formed between the trailing edge and the next adjacent vane in an array.

Optical radiation pyrometer

Abstract: To be of most use as an input signal for the control system of a gas turbine aeroengine, a pyrometer-derived turbine blade temperature signal should represent the average temperature of the hottest parts of the blades with fast and accurate response when the average temperature of the hottest parts changes with engine conditions. The invention achieves this by providing the pyrometer with an optical system adapted to give the pyrometer's photo-diode a large field of view which is rectangular at the face of the turbine rotor and which extends an integer number of inter-blade passage widths in the circumferential direction and a portion of the length of the blade aerofoils in the radial direction. The large rectangular field of view is achieved by masking the optical system and arranging that it cooperates with a small aperture in the wall of the turbine gas passage in such a way that at the aperture the field of view lies entirely within the boundary of the aperature, the field of view expanding out of the aperture to produce the required rectangular field of view at the face of the turbine rotor.

Ceramic casting mould and a method for its manufacture

Abstract: The present invention provides a method for manufacturing a thin-walled ceramic casting mould which is particularly suitable for casting directionally solidified articles in which rapid cooling of the cast material is required. The mould is transfer moulded around a disposable pattern material and includes an integral core. The mould has an outer wall thickness of the order of 0.5 mm to 2.0 mm. The mould and core may be made of the same or different ceramic materials chosen for their strength or thermal conductivity. The method further provides for a series of high temperature disposable supports embedded in the disposable pattern material, providing support for the outer wall of the mould during the firing process. The disposable supports are disposed of at a temperature at which the mould has acquired self-supporting strength.

Method of manufacturing a damped resonator acoustical panel

Abstract: A method of manufacturing a damped resonator acoustical panel in which a porous acoustical damping fabric and a resin impregnated open weave fabric are laid up and subjected to moulding by the application of heat and pressure thereto to cause a portion of the resin from the open weave fabric to impregnate the abutting portions of the acoustical damping fabric and bond the fabrics together. A film of an adhesive is then applied to the open weave fabric and heated by a hot gas stream until it reticulates. The bonded fabrics are then bonded to the edges of an open honeycomb core by means of the reticulated adhesive. A solid sheet is bonded to the other side of the honeycomb core in order to close the cells thereof.

Turbine overspeed limiter for turbomachines

Abstract: A mechanism 25 for preventing a turbine rotor 14 exceeding a predetermined speed in the event that a shaft 24 connecting the turbine rotor 14 to a compressor rotor 12 of the engine breaks and releases its torsional and axial constraint on the turbine rotor. The mechanism 25 comprises a segmented nozzle guide vane assembly 26 downstream of a stage of the turbine rotor 14. Each of the segments 26 is pivotally mounted (hinge pins 40) on an outer casing 34 at a region adjacent a radially outer upstream end of each segment 26. The structure of the engine on which the radially innermost ends of the segments 26 are mounted includes a releasable means 46. When the structure 46 is struck by the turbine rotor 14 the innermost ends of the segments 26 are released and allowed to swing rearwards and outwards about the pivotal attachment of the segments 26 to the outer casing 34. The upstream outer ends of the segments 26 are retained in the path of rotation of the blades of the turbine rotor 14 so that they collide with the blades and decelerate the turbine rotor 14.

Gas turbine engine bearing support structure

Abstract: A gas turbine engine bearing support structure comprises a central hub which carries a bearing and which is supported by a plurality of spokes from a ring member. The majority of the spokes are radially extending so that each is perpendicular to an imaginary tangent at its point of intersection with the ring member. However, two of the spokes are not perpendicular but are inclined so that compressive loading on the spokes results in partial rotation of the central hub, thereby leading to compressive loads in the non-inclined spokes being partially relieved by localised bending.

Fluid operated nozzles for generation of vibrations in liquids

Abstract: A group of nozzles are submerged in a tank of liquid to produce convergent-divergent vortices and cavitation in a liquid which in turn produce acoustic vibrations which assist in cleaning articles placed in the liquid, or in emulsifying a mixture of liquids Each such nozzle comprises a body, with a central axis, an inlet at one end for supply of liquid under pressure thereto, and a plurality of discrete outlet ports at the other end transversely spaced from the central axis, the axes of the ports converging externally of the body towards the central axis whereby liquid supplied to the inlet under pressure emerges from the outlets in discrete jets directed to pass close to but not to intersect the central axis of the body

Air intakes of aircraft mounted gas turbine engines

Abstract: An air intake for a helicopter mounted gas turbine engine comprises two intake portions which comprises vortex separator panels. One panel is generally forward facing while the other is generally sideways facing. A panel is pivotally mounted between the separator panels so as to pivot between a first position in which it obturates the generally sideways facing panel and a second position in which it obturates neither of the separator panels. The arrangement is such that when the helicopter is in fast forward flight, the pressure of the ram air flow through the generally forward facing inlet panel causes the pivoted panel to pivot to the position in which it obturates the generally sideways facing inlet panel.

Propfan aircraft propulsion engine

Abstract: In a propfan engine, the need for an annular or chin-type intake when the propfan is mounted in front of the engine is avoided by mounting the propfan downstream of the engine The engine exhaust is ducted to atmosphere through inner chutes which alternate with outer chutes through which ambient air flows The alternate streams of exhaust gas and ambient air then flow through axial ducts which are located between adjacent blade mountings in the rotating hub of the propfan

Device for passing a fluid flow through a barrier

Abstract: A device is provided for passing a fluid flow across a static or rotating barrier wherein there is relative rotation between the flow and the barrier and wherein it is necessary to pass the maximum of flow through the device while keeping the diameter of the device as small as possible. One embodiment of the invention shown in FIG. 2 is a device for use in a gas turbine engine for supplying cooling air across a bolted joint 19 to a space behind a cover plate 6 for cooling an engine disc. The device comprises a cylindrical receiver 11 having helical slots 13 running through it from one axial end face to the other the helix angle being the same as the angle of the relative velocity vector between the flow and the slots. The helical shape of the slots ensures that the radius of the axis of each slot is constant along the length of the slots and allow greater slot height and hence greater flow area.

Dissolving ceramic materials

Abstract: Ceramic core materials are selectively dissolved from light metal, e.g. Aluminium or light alloy, e.g. Aluminium alloy castings which are themselves susceptible to attack by caustic alkali solutions, by providing the core material with a substance containing Hydrogen donor group which is capable of producing nascent hydrogen and contacting the core with fused anhydrous caustic alkalis. By this means Silica cores can be removed from Aluminium alloy castings, or a ceramic containing a hydrogen donor group can be selectively dissolved from one that does not, e.g. a Silica disposable pattern from within an Alumina mould containing an integral Alumina core.

Mounting system for coupled turboshaft gas turbine engines

Abstract: A mounting system for two turboshaft gas turbine engines which are connected by a coupling gearbox. The mounting system comprises a front mounting attached to the gearbox which permits pivotal movement of the engine/gearbox assembly but restrains longitudinal movement and two strut members which support the engines vertically but provide no lateral or longitudinal support. The engines are interconnected by link members and an intermediate member rotatably attached to the vehicle which permit relative lateral movement between the engines but constrain any lateral movements of the engines which are in unison relative to the vehicle.

Aero engine development for the future

Abstract: A historical survey of the development and future trends in aero engine design and performance are given. Emphasis is placed on the achievement of low cost of ownership through high fuel efficiency...

Detection of changes in transparency of optical elements

Abstract: In a radiation pyrometer in a gas turbine engine, non-uniformly distributed changes in transparency of an optical element in the system, e.g. contamination of pyrometer objective lens L 1 by combustion products from the turbine can be automatically detected. Lens L 1 focusses radiation from target T onto an additional lens L 2 , which in turn focusses it onto the end E of the fibre-optic bundle F. Considered reciprocally, lens L 2 images the end E of fibre-optic F into L 1 , so that although each optical fibre in end E receives radiation from all parts of target T, each fibre is imaged into a corresponding discrete area of L 1 . Fibre-optic bundle F comprises two (or more) sub-bundles F 1 and F 2 forming complementary sub-areas of end E and each sub-bundle is provided with its own photodetector P 1 , P 2 and associated pre-amplifier A 1 ,A 2 adjusted so that their outputs A 1 S 1 and A 2 ,S 2 are matched at the non-contamination condition. When one part of lens L 1 is contaminated during service more than the other parts, this will show as an unacceptable mis-match between the outputs A 1 S 1 and A 2 S 2 . This is automatically detected by differential amplifier D whose output gives a warning indication and can also be used to trigger a selector circuit X to select the strongest signal for onward transmission.

Mounting arrangements for combustion equipment

Abstract: The combustion equipment of a gas turbine engine comprises an annular flame tube and a support casing both subjected to relatively high temperatures. Engine acceleration or engine deceleration causes the temperature in the combustion equipment to increase or decrease respectively, and this results in either expansion or contraction of the annular flame tube and the support casing. The annular flame tube has a greater rate of thermal expansion/contraction than that of the support casing and this results in distortion or cracking of the combustion equipment if the annular flame tube and support casing are rigidly mounted to each other. To overcome this problem a relatively flexible support structure which has a generally U-shaped cross-section is positioned radially between the annular flame tube and the support casing, and a first limb of the flexible support structure is secured to the annular flame tube and a second limb of the flexible support structure is secured to the support casing, and the flexible support structure permits relative radial movement of the annular flame tube and the support casing.

Turbine overspeed limiter for turbomachines

Abstract: A turbine rotor 14 of a gas turbine engine is provided with a mechanism 25 designed to tilt into the path of the turbine rotor blades to decelerate the rotor if a shaft 24, which connects the turbine rotor 14 to a compressor rotor 12 breaks. The mechanism 25 comprises a segmented stator vane assembly 26 in which the segments are supported at an upstream region of their radial inner ends on a deflectable strut 44 and by means of a tie 46 at a downstream region of their radial inner ends. When the shaft 24 breaks, the rearward movement of the rotor 14 is used to unlatch the strut 44 causing the NGV segments 26 to collapse inwards and tilt forwards into the path of the turbine rotor blades to decelerate the rotor. The NGV segments 26 and the turbine rotor blades destroy each other and the resulting debris is ejected out of the jet pipe 22 destroying further downstream turbine stages.

Component inspection by self generated transient stress wave detection

Abstract: A method of inspecting a component in which the surface of the component is scanned with a loud speaker, the sonic output of which is arranged to be at such a frequency or frequencies as to cause any cracks, fractures or unbonded regions within the component to generate transient stress wave emissions. An acoustic emission transducer is attached to the component surface so as to detect any such transient stress wave emissions and thereby provide evidence of the existence of any such cracks, fractures or unbonded regions.

Flame sprayed coatings

Abstract: A method of sealing a flame sprayed metal or metal containing coating on a metal substrate in which the deposited coating is saturated with an anaerobically curable sealant such as a polymethacrylic ester with an amine catalyst which has a viscosity of up to 25 centipoises. After the sealant has been applied to the coating, excess sealant is wiped off the coating surface and the sealant is cured. The sealant prevents the absorption of water by the flame sprayed coating and hence corrosion of the metal substrate.

Vectorable nozzles for turbomachines

Abstract: A vectorable nozzle (17) comprising a fixed first duct (21) a rotatable second duct (22) scarfed at its rear end and a rotatable third duct (23) scarfed at its front end. The second and third ducts (22, 23) are mounted in bearings (24, 26) respectively and the bearing (26) is constrained to swing bodily about trunnions (29) the axis of which lies transverse to the ducts (22, 23), and a screw jack (30) is provided to rotate the bearing (26) about the trunnions (29). The second and third ducts (22, 23) are provided with means to rotate them in opposite directions in syncronism with the rotation of the bearing (26) in the trunnion (29).

Aeroengine test cells

Abstract: Measurements of net thrust of an aeroengine on a thrust balance in a test cell must be corrected to gross thrust and it is also advantageous to detect changes in the airflows into and through the test cell of a magnitude sufficient to alter significantly the thrust correction factor. The invention can accomplish both these objectives by obtaining measures of the static pressures p i and p e in planes i and e respectively of the test cell using pressure probes 29 and 31, and utilizing the measures of p i and p e (a) in a function of the form D=f(p.sub.i, p.sub.e) where D is the thrust correction necessary to convert the net thrust reading on the thrust balance to gross thrust, and (b) to monitor variations of p i and p e with respect to the net thrust and detect such of these variations as are outside predetermined limits of variation, such detection indicating the occurence of changes in the characteristics of the airflows sufficient to alter significantly the value of D.

Apparatus for processing of pyrometer signals

Abstract: A circuit is provided for eliminating the effects of spurious signals from a pyrometer in a gas turbine engine. The pyrometer signal is fed to a part of the circuit (8,12,16,20,24) which produces an inverted and rate limited output signal c representative of the pyrometer output signal. Signal c is fed back to the input of amplifier 8 and is subtracted from it and amplifier 8 outputs a positive or negative signal depending on whether or not its input is positive or negative. The output is passed to a positive edge triggering device 28 which triggers a sample and hold device 30 the output of which constitutes the output of the circuit. When the pyrometer signal increases very rapidly due to a spurious signal, the input to the amplifier 8 rises more rapidly than the rate limited feedback from amplifier 12 so that the output goes positive to trigger device 28 and remains positive until the spurious signal has died away. The sample and hold device 30 thus holds the last sampled pyrometer signal and is not affected by the spurious signal.

Development and Application of Continuous Dress Creep Feed Grinding

Abstract: In 1979 Bristol University concluded some work, on behalf of Rolls-Royce, on continuous dress creep feed grinding. This work had only been applied to flat faces at that point. In November 1979 it was decided to embark on a production implementation plan based on profile work and involving development work in line with production implementation.This paper describes the theory of continuous dress creep feed grinding, explores the development work required and the implementation procedure and experience gained in the production of turbine blades in Product Centre 02 at Rolls-Royce, Derby.