Abstract: To cool the shroud assembly in the high pressure turbine section of a gas turbine engine, high pressure cooling air is directed in metered flow to baffle plenums and thence through baffle perforations to impingement cool the rails and back surfaces of the shroud. Impingement cooling air then flows through elongated, convection cooling passages in the shroud sections and exits to flow along the shroud front surface with the main gas stream to provide film cooling. The aft rail of the shroud sections is provided with one or more cooling holes to impingement cool the annular retaining ring or C-clip retaining the shroud sections on the shroud hangers. This cooling air then travels aftward on the inboard side of the C-clip to provide convection cooling of the C-clip. In an alternative embodiment, cooling air is directed at the aft corners of the shroud base to avoid overheating.

Abstract: A system and method use an optical strain gage to measure engine bearing thrust. Reflecting surfaces, or mirrors, encapsulated in a housing, are separated by an initial gap. An incoming fiber receives light from an interferometer and transmits the light to the reflecting surfaces, which then reflect the light back to the interferometer. An engine load is introduced to a bearing element bonded to the housing, and the rotor thrust into the bearing element causes a change in the initial gap. An increase in the initial gap indicates tension and a decrease in the initial gap indicates compression.

Abstract: A stator airfoil is subject to wake fluid from rotor blades in a gas turbine engine. The airfoil includes a plurality of cross channels extending therethrough between opposite sides thereof for bleeding the wake fluid therebetween to reduce differential pressure thereacross and reduce noise.

Abstract: A compressor stator includes a plurality of vanes affixed to outer and inner bands. A seal includes a pair of mounting rails disposed in respective hooks in the inner band. A spring is affixed to the inner band in compression with an outboard side of the seal to load the rails in radial engagement with the hooks.

Abstract: In a pulse laser drilling process having a machine control for controlling a laser, an apparatus is provided to detect when a hole is drilled through a workpiece. The apparatus detects a laser pulse, where the laser pulse emits a laser light upon drilling impact with the workpiece. A second detection step detects sparks emitted by the workpiece, and a spark signal amplitude representative thereof is produced. The sparks produce visible wavelength light. A filter blocks the laser light and transmits the visible wavelength light. A photosensor associated with the filter senses when the spark signal amplitude diminishes below a predetermined threshold level. An output signal, responsive to the photosensor indicates when a through hole is complete and indicates to the machine control to stop any further laser pulse.

Abstract: The invention includes methods and apparatus for forging and may be applied to trim processes using trim presses. Included are methods and apparatus for forging a gas turbine engine blade forging from a pre-formed workpiece having in serial relationship root, platform, and airfoil sections. A forge press includes a lower die and an upper die and the workpiece has a workpiece contact surface area for contacting a die contact surface area of the upper die during impact of the upper die against the workpiece. A workpiece is heated to a first temperature above an impact temperature, the workpiece is placed on the lower die such that the workpiece contact surface area is in an elevated position above the die contact surface area during chill down, and the ram is actuated to effect impacting of the upper die against the workpiece and contact between the workpiece contact surface area and the die contact surface area during the impacting.

Abstract: A bushing assembly as a means to enable guided movement of a shaft in an opening of a housing comprises a stationary bushing support carried by a housing internal wall. The bushing support has a support internal wall defining a bushing support opening through the bushing support to receive a movable shaft. Carried by the shaft is a removable wear sleeve having a wear sleeve outer wall in juxtaposition with and spaced apart from the support internal wall to permit relative axial movement of the wear sleeve with the shaft within the bushing support opening. Disposed between and for contact with the support internal wall and with the wear sleeve outer wall is an anti-friction layer.

Abstract: A squeeze film damper (SFD) assembly whose chamber configuration reduces or eliminates the tendency for a bistable condition in a turbo machine shaft, such as the rotor shaft of a gas turbine engine. The SFD assembly generally entails a housing having a chamber whose wall circumscribes and contains a bearing assembly by which a shaft is rotatably supported. The bearing assembly is prevented from rotating with respect to the housing, but is otherwise free to move within the housing. An annulus is defined between the chamber wall and bearing assembly, and a fluid is contained within the annulus to support and damp the bearing assembly and its shaft. The chamber wall of the housing is not uniformly cylindrical, but instead is defined by at least two nonconcentric cylindrical wall portions.

Abstract: Gas turbine engines working on an inverted Brayton cycle (IBC) which provides increased power output at a same fuel flow as is currently used in some other known cycles (e.g., air bottoming cycle) are described. In one embodiment, the engine includes a compressor coupled by a first shaft to a high pressure turbine. A combustor is located in the flow intermediate the compressor and high pressure turbine. A free wheeling power turbine is located downstream of the high pressure turbine, and the power turbine is coupled to a load by a second shaft. The flow from the power turbine is supplied, e.g., via ducts, to an axial turbine coupled to an axial compressor by a third shaft. A heat exchanger is located in the flow intermediate the axial turbine and axial compressor. In operation, the working fluid (e.g., air) is compressed by the compressor, and the compressed air is injected into the combustor which heats the air causing it to expand.

Abstract: A turbine airfoil includes a squealer rib extending outwardly from a tip cap to define a tip cavity thereatop. A thermal insulator is disposed in the tip cavity atop the tip cap.

Abstract: A process for manufacturing a component in which residual tensile stresses are present in the component surface as a result of the operation by which the surface was produced. The process generally entails removing residual tensile stresses and inducing compressive stresses in the surface of a component by controlled impacting of the surface with two or more jets of fluid. An additional benefit of this invention is that damaged surface regions of the component can be removed simultaneously with residual tensile stresses by abrading the damaged surface region with a jet of abrasive fluid. The fluid jet employed to abrade the component surface is preferably at a pressure of at least 1360 bar, while the fluid jet employed to induce compressive stresses in the component surface is preferably at a pressure of at least 1700 bar. The second fluid jet can be operated to remove any embedded abrasive grit remaining from the first fluid jet operation.

Abstract: A turbine engine airfoil includes a three-pass serpentine shaped cooling cavity including a leading edge chamber, an oversized intermediate chamber, and a trailing edge chamber in flow communication. The cavity further includes a combination of a plurality of ribs and a plurality of pins, a purge air swirler, a turning vane, and a metering partition which mixes the high pressure air and provides increased air cooling and uniform flow control in the airfoil. The metering partition provides a decrease of the air pressure in the trailing edge chamber allowing for an increase in the number of trailing edge slots.

Abstract: A method for quality assurance of a laser process and, more particularly, a laser shock peening process that uses a ballistic momentum apparatus for maintaining quality control of a laser shock peening process that uses a laser includes a movable target mass having a laser target face and confined to freely move in one direction. An indicating means indicates a maximum distance traversed by the target mass during a recoil from firing of the laser on the target face. An ablative coating is preferably applied on at least a portion of the face and preferably a transparent confinement medium, such as a flow of water, is applied over the ablative coating.

Abstract: A process for depositing a mullite coating on a silicon-based material, such as those used to form articles exposed to high temperatures and including the hostile thermal environment of a gas turbine engine. The process is generally to thermally spray a mullite powder to form a mullite layer on a substrate, in which the thermal spraying process is performed so that the mullite powder absorbs a sufficient low level of energy from the thermal source to prevent evaporation of silica from the mullite powder. Processing includes deposition parameter adjustments or annealing to maintain or reestablish phase equilibrium in the mullite layer, so that through-thickness cracks in the mullite layer are avoided.

Abstract: A gas turbine engine hollow airfoil includes an airfoil outer wall having width wise spaced aparted pressure and suction side walls joined together at chordally spaced apart leading and trailing edges of the airfoil and extending longitudinally from a root to a tip. At least one internal aft flowing serpentine cooling circuit inside the airfoil has an exit that is positioned aft of the entrance so as to have a chordal flow direction afterwards from the leading edge to the trailing edge within the serpentine circuit. At least one longitudinally extending first side wall impingement chamber is in downstream fluid communication with the serpentine cooling circuit within the airfoil and positioned between one of the side walls, preferably the pressure side wall, and a first inner wall bounding the serpentine cooling circuit. Impingement cooling apertures are disposed in the first inner wall between one of the serpentine channels and the side wall impingement chamber.

Abstract: An airfoil having extended life due to reduction in stresses. The stresses are reduced by extending the thermal barrier coating below the radius between the outer band perimeter and the inner flow path surfaces and tapering the coating thickness. This additional tapered thermal barrier coating reduces the temperature gradient across a region already having high mechanical stresses resulting from geometric considerations thereby lowering thermally-induced stresses so that low cycle fatigue life is improved.

Abstract: An electrical discharge machine includes a chuck for holding an electrode above a workpiece. A lower guide positions a tip of the electrode above the workpiece, and mid-guide laterally supports the electrode between its opposite ends for reducing flexing therebetween.

Abstract: A thermal barrier coating system and a method for forming the coating system which yields a thermal barrier coating having good adhesion to a bond coat overlying a metal superalloy substrate. The adhesion of the bond coat and the thermal barrier coating is enhanced by forming a mature .alpha.-alumina (Al.sub.2 O.sub.3) scale at the bond coat-TBC interface. The desired mature .alpha.-alumina scale can be obtained by utilizing one or more of the following steps: preoxidation of the bond coat at certain minimum temperatures and durations; inoculation of the surface of the bond coat; surface doping or alloying of the bond coat surface; and the addition of noble metals to the bond coat. Each of these steps promotes the formation of .alpha.-alumina and avoids the formation of the .gamma., .delta. and .theta.-alumina phases which undergo phase transformations at elevated temperatures, with the result that a more spallation-resistant thermal barrier coating system is obtained.

Abstract: A heating apparatus and method for welding a superalloy article. The apparatus and method of this invention provide for pre-weld and post-weld heat treatments to be performed on an article within the same enclosure in which the welding operation is performed. The apparatus accurately controls the temperature of the component to be welded throughout the temperature treatment profiles with the use of means for welding the article, means for heating the article, and means for sensing the article temperature. The apparatus also works in conjunction with a memory storage device that stores appropriate pre-weld and post-weld heat treatment temperature profiles and a welding temperature profile for the article.

Abstract: A low pressure turbine shroud includes an arcuate backsheet having opposite mounting rails for engaging a surrounding annular case. The backsheet includes a thicker blade containment shield extending between the rails in a unitary construction. And, a honeycomb rub strip is fixedly joined to the backsheet between the rails.