Abstract: A valve assembly for controlling the fluid flow to the fuel spray nozzles in the combustion chamber of a gas turbine aeroengine. The valve assembly comprises a main flow valve whereby translation of the main valve beyond a predetermined limit initiates movement of a control valve by a mechanical interconnection means. Movement of the control valve serves to activate means for fluid communication between the main valve and the control valve, venting some of the pressurized fluid flow acting on main valve to the control valve and subsequently to the fluid outlet. The more sensitive operation and hence quicker response time for any given change in fluid pressure at the inlet to the valve assembly results in rapid closure of the valve assembly when the fluid flow is decreasing which discourages dribble occurring.

Abstract: An air bleed system for a compressor, particularly for gas turbine engines is provided with an air bleed from a portion of the compressor to an annular chamber through an annular opening in the casing; an annular passage is connected to the opening and terminates in the annular chamber surrounding the casing; a plurality of turning vanes change the direction of flow of the bleed air by 90.degree. to induce a circulating flow of air in the chamber; flush openings and ducts angle circumferentially in the direction of the circulating flow in the annular chambers supply air to the engine and aircraft accessories.

Abstract: The high pressure turbine of a gas turbine engine is provided with an annular array of aerofoil rotor blades which are surrounded by a shroud. The shroud is mounted on a tubular diaphragm which is deflected by pressure modulation to vary the effective diameter of said shroud means. An L-shaped cross-section flange provided on the turbine casing cooperates with a plurality of L-shaped cross-section hooks on the diaphragm to limit radially inward movement of the shroud and thereby prevent contact between the aerofoil blade tips and the shroud means.

Abstract: A valve is one of a plurality of similar valves set out in the form of a matrix to constitute a portion of the fuel control system of a gas turbine engine. The valve comprises a piezo-electric crystal and is deformable by the application of a potential difference thereto from a first, non-deformed condition in which the crystal blocks the orifice to second deformed condition in which the orifice is unblocked. At least some of the valves are normally redundant but are caused to become operable in the event of the failure of any of the other operable valves.

Abstract: An integrated rocket ramjet in which initial acceleration of the rocket is achieved by a rocket fuel propellant and subsequent flight is sustained by a ramjet engine receiving air via a supersonic diffuser from an inlet disposed at the middle of the rocket. The flame for the ramjet combustion system is incorporated into the diffuser so that diffusion and combustion take place simultaneously. The combustion process continues within the space previously occupied by the rocket fuel propellant and the walls bounding this space are the outer casing of the rocket and are directly cooled by free stream air flowing past the rocket.

Abstract: An apparatus for machining a brush seal 19 comprising a clamp for holding the brush seal 14 and a cutting member 16 having a diameter which corresponds to the required finished diameter of the seal 19. The cutting member comprises a cup having an axis of rotation R which is positioned to be coincident with the brush seal axis of rotation S. The machining process is conducted by revolving the mandrel and moving it along its axis of rotation such that an edge portion 38 cuts the bristle material at a required diameter and an outer portion 34 acts to grind the bristle elements to the required diameter.

Abstract: This invention relates to a method of enhancing the leaching rate of a given material. The material is provided with a plurality of pores 16 each of which contain a gas, such as for example air, which is intermittantly exposed to the leaching solution 20 by the action of said leaching solution and acts to promote the rapid removal of the reaction product away from the core/leading solution interface 22.

Abstract: A control system for a gas turbine engine guards the engine against destructive overspeed resulting from failure of electronic components in the system due to overheating. A main electronic (preferably digital) controller is normally in control of fuel flow to the engine by means of a flow metering unit. In addition, an electronic overspeed limiter guards against overspeed at normal system temperatures, should the main controller fail, by overriding the action of the main controller on the flow metering unit. A failsafe unit is responsive to the temperature of the control system, and comprises components rated at a substantially higher peak operating temperature than the components used in the other units. The failsafe unit acts as an ultra-reliable switch operative to depower the main controller, and, optionally, the overspeed limiter, when the temperature of the control system exceeds a predetermined value above which components in the two latter units are likely to fail.

Abstract: A temperature indicating device which comprises a plurality of panels in a fixed array. Some of the panels are adapted to undergo a reversible change in appearance at a given temperature whereas the remainder are adapted to undergo irreversible change in appearance at a given temperature. The device is useful in indicating the temperature which an object has achieved as well as its actual temperature.

Abstract: A fuel system for a gas turbine engine in which there is provided a filter 20 having its output connected to the fuel control system 24 that controls fuel flow to the main combustors 26 of the engine. A bypass pipe 25, which has a pressure relief valve 29, by-passes the filter 20 and is connected to the inlet of a fuel control system 23 that controls the flow of fuel to the reheat burners 28 of the engine. A connecting pipe 30 connects the output of the filter to the reheat fuel control system. In normal operation, filtered fuel is supplied to both fuel control systems 24, 27 and there is no flow in the filter by-pass pipe 25. As the filter 20 becomes progressively blocked, filtered fuel is supplied to the main combustors 26 irrespective of whether or not reheat is required. When reheat is selected, and the filter 20 is too blocked to meet the flow demand, relief valve 29 opens to supply unfiltered flow to the reheat burners.

Abstract: A turbofan gas turbine engine comprising in axial flow series a fan, a booster compressor and a core engine is provided with a diffuser. The diffuser is positioned axially between the booster compressor and the compressor of the core engine to efficiently diffuse the air from the fan to the compressor of the core engine. The diffuser comprises a plurality of circumferentially arranged geodesic pipe diffusers, the pipe diffusers extend axially and radially and the outlets of the pipe diffusers are displaced circumferentially by an angle of between 20.degree. and 60.degree. with respect to the inlets of the pipe diffusers.The geodesic pipe diffusers allows the airflow between the fan and the core engine to be diffused adequately without compromising the efficiency of the core engine, or the high mass flow rate of the fan and also minimizes the length, weight and drag of the gas turbine engine.

Abstract: A power turbine (12) comprises alternate annular arrays of contra-rotatable turbine blades. Two arrays of turbine blades (30) and (47) have annular arrays of aerofoil propulsion blades (17,18) respectively attached thereto. Alternate arrays of turbine blades are attached to a primary drum member (55) in such a manner that below normal operating temperatures, limited relative radial movement is permitted between them. However when the normal operating temperature is reached, the relative radial movement is inhibited in such a manner that the rigidity of the power turbine (12) enhanced.

Abstract: Gas turbine engines, usually of the kind which include ducted fans, have cowl structures which generate drag inter alia by virtue of their frontal area. Where the cowl is of very large diameter i.e. in the order of 3 to 4 meters, if known devices such as thrust reverser cascades are installed in them, the frontal area and weight of the structure would be unacceptable. The invention provides a cowl structure of the magnitude mentioned hereinbefore, in which an improved cascade is installed. The or each cascade comprises a pair of rectangular frames which are joined by vanes. The vanes are pivotably connected to the frames in the manner of parallel rules as used in navigation. When non operative, the frames are stowed in superimposed relationship and thus enable a thinner cowl to be utilized than is possible in known cascade storage arrangements.

Abstract: A nozzle for a gas turbine engine having a first fixed petal 44 and a second movable petal 46 which is pivotally mounted at a point intermediate its leading edge 46(a) and its trailing edge 46(b). Actuation means 48 are provided to move the nozzle between a first and a second position. In the petals first position, its leading edge 46(a) is positioned forward of and slightly radially inward of the trailing edge 50 of the exhaust duct 52, such that a small ejector gap 54 is provided therebetween and the trailing edge 46(b) approaches the trailing edge 44(b) of the fixed petal, such that the gap therebetween defines the exit area of the nozzle 36. In the petals second position (shown dotted), its leading edge 46(a) is moved radially inwards of its trailing edge 46(b) such that the exit area of the nozzle is defined by the area between the trailing edge 50 of the exhaust duct 52 on the second petal side and the trailing edge of the first petal 44(b).

Abstract: An apparatus for securing a component, comprising a casing 12 having two portions 12a, 12b between which a portion of the component 38 is positioned. The casing 12 is provided with end walls 34,36 which extend towards the component but terminate just short thereof by a predetermined amount. The position of the component 38 is fixed relative to features 28 provided on the casing 12 prior to injecting a location material into the interior of said casing 12. The material preferably has a high resistance to extrusion and acts to locate the component 38 during machining.

Abstract: An axially extending electrode (16) is provided on a casing liner (10) such that a capacitor is formed, with rotor blades constituting the other electrode, and the tip clearance therebetween forming a dielectric. The axial length of the electrode (16) exceeds that swept by the rotor blade tips and is sufficient for any axial movement of the rotor blades under operating conditions not to affect the capacitance of the sensor.

Abstract: A bypass gas turbine has a mixer nozzle at the turbine outlet with a main body, of lobed cross-section to promote mixing of the turbine gas flow and the bypass flow. For a transition at the forward end of the nozzle from the essentially circular boundary between the two flows preceding the turbine outlet to said lobed form, there is an annular connecting ring fairing a channel section with radially inner and outer flanges to which the forward end of the fabricated main body is secured at the peaks and troughs of its lobes. Fairing elements are secured to the flanges to blend with the lobed form of the nozzle body. Because the nozzle body has a lobed form along its entire length it can be constructed as a single skin fabrication while retaining sufficient stiffness to prevent unacceptable deformations from the pressure forces on it under reverse thrust conditions.

Abstract: Variable stator vane arrangements for compressors of gas turbine engines suffer from errors in the angular position of the variable stator vanes because of relative movement between the stator casing and control ring which is allowed by a clearance between the stator casing and control ring. A plurality of pieces of material which have a relatively high coefficient of expansion are arranged circumferentially and are positioned radially between the control ring and the stator casing. The pieces of material control the effective clearance between the control ring and the stator casing so that the error of the variable stator vane angular position is minimized. The pieces of material may be formed from a polyimide resin or high coefficient of expansion steel, and may be positioned in housings which are secured to the control ring.

Abstract: The pins which are used for the support of a core in a lost wax casing process are provided with caps. The caps provide sufficient surface area for encapsulation by ceramic slurry. Heat loss from the metal melt via the pins is thus obviated along with undesirable grain nucleation.

Abstract: A pitch arrangement for a variable pitch fan assembly of a turbofan gas turbine engine comprises a plurality of fan blades, each of which has a root portion rotatably mounted, in a thrust bearing on a fan rotor. A control ring is arranged coaxially with and is rotatably mounted on the fan rotor, and each of the fan blades is connected to the control ring by a lever arm. The pitch of the fan blades is varied by rotation of the control ring in either direction. A plurality of hydraulic rams are arranged to drive the control ring through a plurality of bell cranks. The hydraulic rams are mounted on the fan rotor so that the pistons and shafts move in a radial direction such that the centrifugal force of the pistons and shafts is applied to the bell cranks so that a counter turning movement is applied to the control ring to oppose the centrifugal turning moment of the fan blades.