Abstract: A nozzle guidevane for a gase turbine engine 10 comprising a first fixed upstream portion 24, a movable downstream portion 26 and a seal situated therebetween. The seal comprises two pairs of ridges 56, 58 on the upstream portion and two ridges 60 on the downstream portion 26 which co-operate with each other to form a flow restrictor which maintains the flow of escaping air within acceptable limits. The air which does escape is used to advantage by maintaining the mainflow of air over the outside of the vane 22.

Abstract: Combustion apparatus for a gas turbine engine comprises a burner which is so configured and located within a combustion chamber so as to urge fuel and air mixture ejected therefrom into a fuel rich toroidal vortex in an upstream first combustion zone of the combustion chamber. Unburnt fuel from the first combustion zone is mixed with additional air in a second fuel weak combustion zone downstream of the first zone. Adjustment of the air to fuel ratios in the two combustion zones results in the reduction of smoke and oxides of nitrogen reduction.

Abstract: A mechanism suitable for friction welding aerofoil blades to the periphery of a disc. The mechanism comprises a first member (flywheel 12) which has an ecentric crank pin. Two pivotally interconnected links 18 and 20 are connected between the crank pin and a second member 19 which is pivotally mounted. A blade to be friction welded (by rubbing it in an arcuate path on the disc) is mounted at the point of pivotal connection 32 between the second link 20 and the member 19. An actuator lever 24 is pivotally mounted on a pivot 22 which is located in the vicinity of the locus of movement of the pivotal interconnection 30 between the two links 18, 20. The actuator has a third link 28 which is of the same length as the link 20. The third link is connected by a pivot 26 to the lever 24 at a radius equal to the length of the second and third links 20 and 28.

Abstract: To produce an image of a component of part of an engineering structure such as an aero-engine using a positron emission tomography (PET) technique it is proposed to provide the component or part of the structure of interest with a surface coating containing a radioisotope labelling material. The radioisotope label may be provided by applying a film of lacquer, paint or the like containing the isotope, or the component etc. may be bombarded by suitably energetic ions in order to induce a reaction in which a selected isotope is produced.

Abstract: The invention relates to turbopropeller gas turbine engines of the type which have a propeller positioned upstream of the gas generator. Intake openings supply air through intake ducts and annular intake duct to the gas generator. A separating duct removes foreign bodies from the air flowing through an outlet. The separating duct has a plurality of ejector nozzles equi-spaced in the wall of the duct. The ejector nozzles induce a flow through the separating duct to draw the foreign bodies through the separating duct. The separating duct allows the passage of large foreign bodies therethrough without damage to the ejector nozzles. The ejector nozzles are supplied with air from a compressor of the gas generator, and this allows control of the flow through the separating duct by a valve.

Abstract: A heat exchanger comprises a matrix made up of alternate layers of generally planar sheets and generally corrugated sheets which cooperate to define a plurality of parallel passages for first and second heat exchange fluids. Alternate of the passages defined by each of the corrugated sheets and its adjacent planar sheets are adapted for the passage of a first heat exchange fluid and the remainder adapted for the passage of a second heat exchange fluid. The ony bonding together of the planar sheets and corrugated sheets is along those portions of their peripheries which are parallel with the defined passages.

Abstract: The invention relates to variable guide vane arrangements for axial flow compressors of aircraft gas turbine engines. The variable guide vane arrangement comprises a plurality of stator vanes rotatably mounted in a stator structure of the compressor. A control ring surrounds and is normally coaxially with the compressor axis, and a plurality of operating levers extend from the control ring to their respective stator vane. The control ring is movable laterally with respect to the axis of the compressor so that the stator vanes in a first half of the compressor are rotated in one direction so that the first half of the compressor operates at a higher pressure ratio and the stator vanes in a second half of the compressor are rotated in the opposite direction so that the second half of the compressor operates at a lower pressure ratio.

Abstract: A gas turbine engine combustor is provided with a semi-spherical upstream wall constituted by two correspondingly shaped skins which are spaced apart by pedestals attached to one of the skins to define a space between them. Cooling air is progressively metered into to space through apertures in the first upstream skin to provide effective cooling of the second downstream skin. The cooling air is exhausted from the space through an outlet defined by the first skin and the periphery of the second skin to provide film coating of the upstream end of the combustor side wall.

Abstract: In order to evaluate the condensation amount in a jet engine intake duct, for calibrating the engine, apparatus are provided which induce a high speed flow of air through a duct. The duct is designed so that the air velocity within it very gradually increases along it until a choked (sonic) condition is reached. At or around sonic conditions static pressure is very responsive to changes in flow due to condensation. Thus by first obtaining a pressure profile along the duct under non-condensing conditions and then comparing this with a pressure profile under condensing conditions a condensation amount can be computed.

Abstract: An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

Abstract: The invention is aimed at avoiding excessive wear of the tips of the turbine blades in deceleration of a gas turbine engine, and provides a control ring which is loosely supported by fixed structure. The control ring is made from a material which reacts more slowly to thermal changes than the support structure and firstly being loosely supported thereby, avoids the stresses which would be otherwise experienced by the fixed joining of differing materials for operation in varying temperatures. Secondly, on deceleration of the associated engine with consequent fall in operating temperature, the control ring contracts more slowly than the turbine assembly and so avoids engaging the shrouds abradable linings with the tips of the blades.

Abstract: An aerodynamic or hydrodynamic surface is provided with so-called "riblets" for reducing drag by modification of the turbulent boundary layer. The riblets comprise flow-aligned elongate projections of small height. In order to increase their effectiveness in reducing drag, just those parts of the riblets which extend above the height of the virtual surface--established by the riblets themselves due to their displacing the turbulent motion away from the real surface--exhibit an abrupt transition to a cusp-shaped profile which more effectively promotes very small scale flow-aligned vortices which drain energy from the larger drag-inducing low speed flow-aligned vortices or "streaks" in the boundary layer.

Abstract: A variable stator vane assembly suitable for a power turbine in which each stator vane is provided at its radially inner and outer extents with disc-shaped platforms which locate on bushes provided on associated support structure. The bushes are cooled by a flow of cooling air which is of higher pressure than that of the hot gases operationally flowing over the vanes so as to prevent the leakage of such hot gases past the bushes.

Abstract: A mechanism for use in linear friction welding has a drive-shaft (10) rotatable about a first longitudinal axis (12). An eccentric portion (10A) for locating a cam member (18) has a second longitudinal axis (16) spaced a distance d from the longitudinal axis (12) of the drive-shaft (10). The cam member (18) has a third longitudinal axis (20) spaced distance d from the second axis (16) of the cam member (18). A connecting-rod (24) is located via a big-end bearing (26) on the periphery of the cam member (18). When the drive-shaft is rotated with the third axis (20) of the cam member (18) displaced from the longitudinal axis (12) the connecting-rod reciprocates. If the cam member (18) is rotated about the second axis (16) of the eccentric portion (10A) until the longitudinal axis (12) and the third axis (20) of the cam member (18) are coincident the connecting-rod stops reciprocating.

Abstract: To evaluate the working line characteristics of a compressor of a gas turbine engine, fuel is supplied from the gas turbine engine fuel supply to a fuel accumulator via a control valve. The control valve is closed when a predetermined quantity of fuel is in the fuel accumulator, and a three way valve is adjusted to allow high pressure fluid from a fluid cylinder into the accumulator to pressurize the fuel. The fuel is then supplied from the accumulator via the valve to a combustion chamber to be burnt to increase the pressure in the combustion chamber and hence the compressor. The pressure of the fuel supplied which causes a surge is indicative of the working line characteristics of the compressor. The pressure and quantity of fuel supplied are varied until a surge is produced.Reworking of compressors with reduced surge margin can be carried out. Enables evaluation to take place while the engine is fixed to an aircraft.

Abstract: A rotor assembly for use in a rotodynamic machine comprises a rotor disc (10) with a plurality of blades (14) attached to its outer rim (12) and a seal plate (22) for substantially preventing the escape of blade cooling air. The rotor disc (10) is provided with a plurality of hooked restraining members (30) each including a radially inward directed abutment face (32) which in use restrain the seal plate from moving axially and from moving radially outward under centrifugal force by abutment with the seal plate. In this way the blades (14) are not subjected to additional loading by the seal plate (22).

Abstract: A single link digital telemetry system transmits data in serial form from a sending station. The data clock signal is recovered at a receiving station for data synchronization purposes. To achieve recovery of the data clock signal the incoming data is synchronized with a high frequency clock of n times the original data clock frequency; the fast clock is utilized to drive a data latch so that on each positive incoming data edge the latch produces a synchronized data pulse for feeding to a recirculating shift register n bits long, which is also driven by the fast clock. The original data pulse can be recovered merely by tapping off from a chosen location on the register.

Abstract: An alloy suitable for making single crystal castings consists essentially of the following constituents by weight percent:______________________________________ Chromium 8-15% Aluminum 5-7% Titanium 2-5% Niobium 0.1-2% Molybdenum 0-7% Tantalum 1-8% Tungsten 0-7% Cobalt 5-15% Vanadium 0.5-2% Carbon 0-0.05% Balance Nickel plus impurities. ______________________________________The combined weight of Tungsten, Molybdenum and Tantalum is from 2.5 to 8.0 percent by weight of the total alloy weight and the combinations of Aluminium, Titanium, Niobium, Tantalum and Vanadium are balanced such as to give an alloy volume fraction of between 60 and 75% of gamma prime (Ni.sub.3 (M)) where M is Aluminium, Titanium, Niobium, Tantalum, Vanadium and also minimum gamma/gamma prime lattice mismatch. The alloy has good high strength characteristics, impact resistance, corrosion and oxidation resistance and has a wide heat treatment window.

Abstract: A method of manufacturing an axial flow compressor stator assembly in which a plurality of aerofoil cross-section stator vanes having divergent inner and outer extents are encapsulated in a low melting point alloy so that their extents protrude from the alloy. The vanes are encapsulated in the same relationship with respect to each other which they would assume in a compressor. A moulding material is then moulded around the radially inner and outer extents to define arcuate bridging member which interconnect adjacent stator vanes. A stiffening member is bonded to the bridging piece interconnecting adjacent radially outer stator vane extents and the whole assembly heated to melt the encapsulation alloy.

Abstract: A gas turbine engine for a compound helicopter comprises a core gas generator, an upstream fan, and a power turbine. Bypass air is selectively directable to either augmentor wings, or to a second power turbine which is mechanically coupled to the first power turbine.