Abstract: A method for moulding multiple castings in which each mould is fed from a source of molten metal through a thin slit the width of which lies in the range 1.25 mm down to 0.25 mm. The cast articles can easily be removed from the runner and riser system after casting without a machining operation so that the casting moulds can be packed closer together and more castings can be produced from each mould assembly. The thin slit also acts as a filter. A particular mould assembly seen in FIG. 2 is cylindrical and comprises a plurality of wedge-shaped mould segments 2 having mould cavities 4 in abutting faces. A central runner passage 6 is formed when the mould segments are assembled and the metal flows into the mould cavities through narrow slits 10 in one edge of each mould. After casting and removal of the mould the narrow flashing formed in the slits can easily be broken to remove the cast articles from the metal formed in the central runner passage.

Abstract: A fuel control unit forms part of a control system of a gas turbine aeroengine. The control unit is in communication with a main fuel line leading to the aeroengine and comprises a fuel accumulator, i.e. volume varied by free piston, which is controllable by the control system to take fuel from the fuel line to reduce temporarily but substantially the mass flow of fuel to the aeroengine. This is helpful in combating surge conditions in the aeroengine caused by temporary overfueling of the aeroengine by the fuel control system.

Abstract: Surge conditions in the compressor of a gas turbine aeroengine can be automatically controlled by a surge control system in which compressor outlet pressure is monitored and a signal P corresponding to it is processed in a surge detector to determine the ratio P/P and to compare the value of the ratio with a predetermined reference value, surge correction control signals being outputted whenever a surge is detected. Surge is controlled as these signals actuate various units linked with the surge detector, these units achieving bleeding off of air from the compressor, reduction of the mass flow of fuel to the aeroengine, and maintenance of fuel ignition for a predetermined period.

Abstract: Hollow fluid cooled turbine blades of the multi-pass type used in gas turbine engines have suffered from separation of cooling fluid from longitudinally extending walls defining longitudinally extending passages as the cooling fluid is turned through a turning passage from one longitudinally extending passage to an adjacent one. The invention provides an aerodynamically shaped end portion arranged at an angle with respect to the remainder of the wall to increase the turning radius, and a turning vane is positioned in turning passage to form a convergent passage with the end portion of wall. The turning vane has a large turning radius and a large surface area for retention of a boundary layer of cooling fluid thereon. The turning vane directs the cooling fluid flowing through the convergent passage and over the turning vane substantially parallel to the wall to reduce separation in order to reduce pressure losses.

Abstract: A marine gas turbine engine including a fluid coupling between its low pressure turbine and power turbine. During forward drive the fluid coupling is drained so that the exhaust gases from the low pressure turbine drive the power drive in a first direction of rotation. For reverse drive, the fluid coupling is filled so as to couple the low pressure turbine and power turbine and cause the power turbine to rotate in the opposite direction of rotation. When the fluid coupling is operational, the compressor delivery air and low pressure turbine exhaust gases are exhausted to atmosphere.

Abstract: A gas turbine engine is of a size suitable for generating electrical and heat energy for domestic and other purposes. The engine has a low number of components, and some of the components are capable of performing more than one function. For example, the engine has a centrifugal compressor driven by a centripetal turbine through a shaft. The compressor and turbine are mounted in a casing comprising a two part core and two end plates. The gas flow ducting is formed by surfaces on the compressor and turbine rotors, the core and the two end plates.

Abstract: Simplification in manufacture and use of an optical triangulation probe is achieved by providing it with a T-shaped optical path. The cross-bar of the T-shape extends between a light source comprising a laser diode and a light detector comprising a photodiode array, while the stem of the T-shape contains a rod-shaped lens and prism arrangement. The cross-bar of the T-shape is occupied by a solid optical bar-shaped assembly comprising a number of blocks cemented together and providing reflective surfaces for directing outgoing and return light through the T-shape. The lens and prism arrangement focusses outgoing light from laser diode onto the surface of an object whose distance is to be measured and focusses reflected return light onto the photodiode array as a light spot. Position of the light spot as monitored by the output signal of a photodiode array is a measure of distance D between the object and the probe.

Abstract: A rotary bladed machine (10) is provided with two probes (16,17) which provide output signals upon the passage past them of the tips (15) of an annular array of rotor blades (14) mounted within the machine (10). Electrical circuitry associated with the probes (16,17) incorporates a ramp generator (29) which provides steadily increasing and decreasing voltages as the blade tips (15) successively pass the probes (16,17). The ramp generator (29) voltage is sampled at regular intervals, the circumferential spacing of the probes (16,17) and the rates of the ramp generator (29) voltage change being chosen such that the sample voltage is zero in the event of the spacings between the blade tips (15) having a predetermined value but is not zero in the event that those spacings depart from the predetermined value. The sampled voltage is a function of the amplitude and frequency of vibration of the disc (13) carrying the blades (14).

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.

Abstract: Those gas turbine engines which have reserver cascades covered by a translatable cowl portion when reverse thrust is not required, may undergo inadvertent translating of the cowl portion on take off or cruise with consequent disasterous results. The invention provides an anti rotation mechanism which prevents rotation of the shafts and gearing commonly used for translation of the cowl, in the direction which results in uncovering of the cascades. The mechanism comprises a rod movable to a position closely adjacent a gear shaft which is part of the translation system, a bar mounted in the end of the rod for pivoting and reciprocatory movement and abutments on the gear shaft. When the shaft rotates to bring about closure of the cowl, the rod at the point of near closure is moved closely adjacent to the shaft.

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.

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.

Abstract: A transducer for detecting stress waves comprises a piezo-electric member which is mounted on a brass backing member and carried by a boron nitride support member. The piezo-electric member is deformed under the influence of stress waves to generate an electrical output, the magnitude of which is indicative of the magnitude of the stress waves.

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.

Abstract: A gas turbine engine oil system is provided in which the centrifugal separator is arranged to act as a pump for supplying bearing chambers directly, and the scavenging of the bearing chambers is achieved primarily by the pressurization air which flows into the chambers to prevent oil leakage. To avoid the use of pressure regulating valves for controlling the oil flow an oil tank is pressurized and communicates with an auxiliary outlet from the separator, the pressure in which is governed by the quantity of oil flowing around the system. The tank and the bearing chambers are fluidly connected to the centrifugal separator in two separate fluid circuits with each circuit having the separator as an element thereof.

Abstract: The exhaust mixer can be classified as being of the multi-lobed type, with troughs between the lobes. The lobes and troughs comprise confronting pairs of flow surfaces which are twisted between their upstream and downstream ends such that a vortex flow system is established downstream of the mixer to encourage mixing between the bypass airstream and the turbine exhaust stream. The downstream edges of the twisted flow surfaces are in the form of sinuous curves which destabilize the vortex system and cause the vortices to burst, hence increasing the mixing efficiency.

Abstract: A housing for a rotor of a turbomachine comprising, radially spaced inner and outer casings. The inner casing comprises a plurality of segments 20(a) to 20(e) each of which comprises one or more stator vanes 23. A first of the casings 19 has two or more axially spaced locating members 21,22 which co-operate with locating means 25,29 on the second of the casings 18 to locate the first casing 19 relative to the second casing 18. A first of the locating means 25 comprising a first surface 27 inclined to a direction extending axially along the second casing 18 and a second surface 28 that constitutes a sealing face. A first of the locating members 21 having a third surface 32 that confronts the first surface 27. In use, axial gas loads on the stator vanes 23 cause the first and third surfaces 27,32 to engage each other and slide along the incline to bring a fourth surface 33 on the member 21 into sealing engagement with the said second surface 28.

Abstract: Cores made from Alumina and other non-Silica based refractories can be made readily leachable in fused anhydrous caustic alkalis by the addition to the core of a small quantity of a material containing a Hydrogen donor group. The Hydrogen donor group is one which produces uncombined, or nascent Hydrogen when the ceramic is contacted with the anhydrous caustic alkali. Such groups are Hydroxyl groups, Hydrides or chemically combined water. In one disclosed example Silica which contains traces of water is added to high fired Alumina to provide the Hydrogen donor group. Only 2% to 3% Silica addition is required to make the Alumina readily soluble in the fused alkali.

Abstract: A hydraulic seal and an oil scavenge system are combined, and oil pumping gears and other associated equipment thus obviated. The hydraulic seal 32 comprises an oil reservoir holding centrifuged oil, and an annular fin 22, the periphery of which dips in the oil. The fin 22 has an orifice 33 which receives the oil under pressure derived from the speed of rotation of the oil, and passes it via conduit 34,26 to an oil sump.

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.