Abstract: A gas turbine engine annular combustor having a bulkhead at its upstream end which is thermally protected by an annular array of heat shields. Each heat shield is provided with integral flanges which space apart the heat shields and bulkhead to define chambers therebetween. Apertures in the bulkhead direct cooling air into the chambers. Further apertures in the heat shields exhaust the cooling air in a common circumferential direction so that the air flows merge to define a substantially continuous annular flow of cooling air about the longitudinal axis of the combustor and across the downstream heat shield faces.

Abstract: A method of making a bladed disc assembly, of a kind used, for example, in the turbine or compressor sections of a gas turbine engine, includes forming a peripheral groove in the rim of the disc, positioning a plurality of bladed segments around the disc, each segment preferably including two or more blades extending radially from a root portion, each segment having its root portion located in the groove, securing the root portions in the groove by means of electron beam welding to form circumferential seam welds at either side of the root portions and axial seam welds between the root portions of adjacent segments thereby forming a vacuum seal, and diffusion bonding the root portions and the rim of the disc by means of isostatic hot gas pressure bonding.

Abstract: In a VTOL or STOL aircraft in which a lift device is housed internally within the aircraft fuselage or wing an outlet nozzle is stowable within the lift device exit aperture. A pair of doors, which when closed conceal the aperture from the sides of the nozzle, and a third folding member form the forward side of the nozzle and support a frame carrying variable vanes which vector the lift thrust.

Abstract: To modify a turbulent boundary layer flow over a surface to reduce its drag, a series of streamwise riblet projections is provided on the surface arranged in a pattern consisting of spaced larger height projections between which are a plurality of smaller height projections The latter inhibit turbulent eddy motions from penetrating deep into the grooves between them and so displace the turbulent motion away from the wall. The larger projections control the longitudinal vortices or streaks that are characteristic of turbulent boundary layer flow and promote energy transfer to the smaller scale secondary vortices associated with the smaller projections.

Abstract: A method and means are provided for operating a bleed to counter surge in the compressor of a gas turbine. A number of engine condition parameters which are precursors to a change of engine running conditions are monitored to detect changes outside predetermined limits. The method includes deriving a measure of heat soakage effects as an engine condition parameter by monitoring a gas flow value such as compressor outlet pressure, and deriving a further engine condition parameter by evaluating changes of engine power-setting by comparing instantaneous power-setting commands with lagged values of power-setting commands. If over-limit values of a monitored engine condition parameter are detected the bleed is opened and the bleed is maintained open if monitored changes of an engine operational parameter (such as compressor speed) exceed predetermined limits within a predetermined period of the opening of the bleed by an over-limit engine condition parameter.

Abstract: It is common practice to assemble heat exchangers from a multitude of pre-formed and sometimes extremely delicate pieces. The pieces have to be held in jigs along with appropriately placed braze material and then heated to achieve brazing. The invention takes advantage of the ability which some materials have to considerably extend their areas without rupturing by using such materials in that they are assembled in the flat condition and then diffusion bonded, followed by inflation of the parts of the assembly which are to provide the fluid passageways, inlet manifolds and headers. The construction of heat exchangers is thus considerably simplified.

Abstract: A plate-fin type of heat exchanger (100) facilitates exchange of heat between two or more process streams (101, 102). It comprises a matrix (M) of two different types of heat exchange plate elements (P1, P2) inter-digitated with each other. Adjacent plate elements are metallurgically bonded together for good thermal contact by an activated diffusion bonding process. The plate elements (P1, P2) are high-integrity diffusion bonded sandwich constructions comprising two outer sheets (201, 203 - FIG. 4 and a superplastically expanded core sheet structure (202) between the two outer sheets. The sandwich construction provides flow passages (P) for the process streams. Adjacent plate elements (P1, P2) carry different process streams (101, 102).

Abstract: Carbon coated carbide fibers are arranged in a predetermined pattern and shape around a silicon carbide coated graphite insert. Silicon carbide is infiltrated into the silicon carbide fibers to produce a SiC/SiC composite component. The SiC/SiC composite component is coated with glass and is then heated in air to burn out the graphite insert to form a hollow glass coated SiC/SiC composite component. The method is suitable for producing hollow SiC/SiC composite turbine blades or vanes.

Abstract: A cam operated valve mechanism for directing the flow in a fluid flow duct to selective alternative outlets. The valve comprises an annular array of segmented elements which are each pivotally mounted to an axially translatable sleeve disposed coaxially within the duct. In a first axial position the sleeve extends across port and starboard alternative flow outlets, and in a second axial position extends downstream thereof. Each valve element comprises a cam follower which engages an axially extending cam track formed in the duct surface. The profile of the cam track is such that translation of the sleeve from its first to second axial position causes each of the valve elements to rotate from a stowed to a deployed position, and thereby obturate the duct.

Abstract: The mechanical behavior of a given component formed from reinforcing ceramic fibers enclosed in a ceramic matrix is determined by subjecting a dummy component to mechanical testing. The dummy component is formed from low modulus organic resin fibers enclosed in a matrix of an organic resin having a correspondingly low modulus. The organic resin fibers have the same configuration and fiber architecture as those of the ceramic fibers.

Abstract: A nacelle of a gas turbine engine is attached via a pylon to an aircraft wing from which the engine is to be mounted. The nacelle is split to form a pair of opposing arcuate doors which are moveable between an open position and a closed position. When the doors are closed a ring on the fan casing locates in a correspondingly shaped groove on the inner surface of the arcuate doors. The nacelle is structurally integrated with the fan casing with the ring so that all the engine loads are transmitted through the nacelle. Telescopic struts are provided to connect the engine casings directly to the pylon so that when the arcuate doors are open, to allow access to the engine, the struts 50-60 support the engine.

Abstract: A duel fuel gas generator (10) is provided with a steam injection system (48) having a bleed-off valve (66) and a steam metering valve which are controlled in concert by a controller (50) to supply steam to a steam manifold (22) for injection into the gas generator at rapidly variable rates independent of the steam supply rate from a boiler (42, FIG. 1). A proportion of the system can be preheated using a steam warm-up flow through the bleed-off valve (66). A further portion of the system can be purged and preheated using compressor delivery air to flow through a steam metering valve (80), a purge valve (74) and a drain valve (94). To control the degree of superheat at the steam manifold (22), water can be injected through a metering valve (90) and a vortex mixer (92), and to purge condensation from a gas fuel manifold (30, FIG. 7) of the gas generator, compressor delivery air can be allowed to flow through the manifold (30 ), a supply line (108) and a purge valve (112) to atmosphere.

Abstract: A fan for a ducted fan gas turbine engine comprises a hub carrying an array of generally radially extending fan blades. The hub is hollow and tapered in an axial direction. The radially outer hub surface is provided with a plurality of generally axially extending slots. The slots receive corresponding stepped teeth provided on the radially inner ends of the fan blades. A nose cone engages the upstream end of the roots of the fan blades to ensure that the teeth are retained in the slots.

Abstract: A turbine compressor or turbine bladed disc assembly wherein the blades 6 include root portions 8 provided with opposed converging surfaces 9,10 and the disc 14 includes slots 11 provided with opposed diverging surfaces 12,13. In assembly the root portion 8 of a blade 6 is engaged in a slot 11 with abutting converging and diverging surfaces and the blade 6 is oscillated relative to the disc whilst pressure is applied radially to urge the root into close contact with the slot until melting temperature is reached whereupon the oscillatory motion is arrested and the pressure maintained as the converging and diverging surfaces coalesce. A hole 16 may be drilled through the assembled blade and disc assembly in order that communication may be made with cooling air passages in the blade.

Abstract: A plurality of titanium sheets are assembled into a stack. At least one of the sheets is provided with a stop off material on one of its surfaces to prevent diffusion bonding at predetermined positions. The edges of the sheets are welded together and a pipe is welded to the stack to interconnect with the stop off material to form a sealed assembly. The assembly is heated and externally pressurized to diffusion bond the sheets together. The integral structure so formed is heated and opposite ends of the integral structure are twisted relatively to contour the integral structure to a predetermined shape. The integral structure is internally pressurized to break the adhesive bonds. The integral structure is heated and internally pressurized to superplastically form one sheet to produce an article, e.g. a fan blade.

Abstract: A method of welding comprises forming an alternating current electric arc between an electrode (32) of a tungsten inert gas welding torch (30) and a metallic substrate (10). The alternating current has a square wave form which is self supporting and does not require intercycle high frequency support. The square wave alternating current has a wave bias ratio equal to or greater than 90% forward current to 10% reverse current. A metal welding rod (38) is supplied into the electric arc for depositing a weld deposit (40) on the metallic substrate (10). The welding method is used to apply a metallic wear resistant coating (40) to an edge surface (20 or 22) on a shroud (18) of a turbine blade (10) and is used to seal a cooling passage of a turbine blade or turbine vane.

Abstract: An abrasive medium suitable for the cutting tip of a turbine blade of a gas turbine engine comprises cubic boron nitride grit coated with a layer of aluminum nitride. Coating of the grit particles is carried out by vapour deposition in a fluidised bed reaction.

Abstract: The smaller diameter end of a first stiff frustoconical casing member (74) is secured to a compressor casing (34) and the smaller diameter end of a second stiff frustoconical casing member (80) is secured to the nozzle guide vanes (40). A plurality of hollow axially extending members (86) are secured to the first and second stiff frustoconical members (74, 80) to transfer tensile and compressive stresses between the compressor casing (34) and the nozzle guide vanes (40). The larger diameter end of the first stiff frustoconical member (74) is secured to an engine casing (52) by a first radially and axially flexible member (88) to define a second chamber (100), and the larger diameter end of the second stiff frustoconical member (80) is secured to the engine casing (52) by a second radially and axially flexible member (94) to define a third chamber (102).

Abstract: A gas turbine engine includes a casing cooling system which operates in one of two conditions, the first being operational at engine cruise, where all of the cooling air is initially directed onto a specific region of the casing; under full power conditions, some of the cooling air is directed onto the specific casing region and the reminder directed onto the reminder of the casing; the cooling system operates to optimize turbine blade/casing radial clearances.

Abstract: An assembly for making a wax pattern of a hollow component includes a pattern die and a noncircular core which is located within the pattern die. The pattern die is a split die and includes two halves which have shaped internal surfaces to define the external shape of the wax pattern of the hollow component. The core has shaped external surfaces which define the internal shape of the wax pattern of the hollow component. The core has coaxial circular cross-section projections which locate within correspondingly shaped and dimensioned apertures in the pattern die. One of the apertures in the pattern die has a radially extending pin which is arranged to mate in a groove on the projection to locate the core longitudinally. The core is allowed to rotate within the die so that chaplets on the core position the core accurately without imposing strains on the core.