Abstract: A fuel nozzle for gas turbine combustors reduces combustion instabilities by injecting purge air into the combustor angularly instead of axially. The fuel nozzle has a substantially cylindrical body with a number of internal passages. One of the passages provides premix gas fuel to a plurality of fuel injectors attached to the fuel nozzle. The remaining passages can be for diffusion gas, atomizing air and liquid fuel. One or more of the remaining passages is connected to a respective group of discharge orifices formed in the cylindrical side surface of the nozzle body. During low NO.sub.x operation, premix gas is introduced through the fuel injectors, and the remaining passages are all purged with air to prevent the ingress of flame gases from the combustion chamber. The resulting jets of air emitted from discharge orifices formed in the side surface will disrupt or break-up spanwise vortices shed from the bluff end of the fuel nozzle, thereby reducing combustion instabilities.

Abstract: A refrigerator evaporator is formed in a spread serpentine configuration having a plurality of straight tube segments and a plurality of bent tube segments where each one of the straight tube segments is joined at an acute angle to at least one other straight tube segment. The straight tube segments are arranged in a number of planar rows which are adjacent and parallel to one another. Approximately 25-50 percent of the cross-sectional area of the evaporator is not occupied by tubing or any attached fins. A cross flow blower disposed at one end of the evaporator draws air longitudinally over the evaporator.

Abstract: An expanded fiber composite structure and process for making an expanded fiber composite structure are provided. The expanded fiber composite structure is made up of a fiber mat held in partial compression by a monolithic plastic coating on the fibers, the structure having a plurality of interstitial voids which may optionally be filled with a polymeric interstitial material. The process includes impregnating a fiber mat with a plastic material, compressing the mat to impregnate the mat with the plastic, fully wetting each fiber and creating a substantially void-free fiber/plastic matrix, and reducing the compressive forces on the mat, allowing the fibers to rebound and expand the mat to a predetermined desired thickness, in the process creating the interstitial voids. The structure is then cooled such that the plastic material stiffens and itself retains the structure at the desired thickness.

Abstract: This invention relates to the use of a catalytic preburner for heating the pair from compressor discharge temperatures to above the light-off or extinction temperatures of a catalytic combustor. Such structures of this type, generally, eliminate the diffusion flame during steady-state operation and produce a preburner/catalytic combustor system capable of achieving less than 1 ppm NO.sub.x.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency is tuned by adjusting the size of a frame which encloses the noise radiating element. One or more expandable elements are disposed in the frame to produce expansion and contraction of the frame. The elements are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the frame to expand or contract.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied.

Abstract: A trim system reduces NO.sub.x output from a cannular gas turbine by trimming fuel flow rates to equalize the fuel-air ratio in each combustor can. The system includes a main valve fluidly connected to the fuel inlet of each can and a trim valve fluidly connected to each fuel inlet in parallel with the main valve. Each trim valve has a flow resistance which is about 30-100 times greater than the flow resistance of each main valve. A controller is provided for controlling the opening of the trim valves in response to the level of NO.sub.x emitted from the gas turbine. The controller receives a signal corresponding to the NO.sub.x emissions from a NO.sub.x sensor and outputs suitable control signals to the trim valves. In one preferred control scheme, the controller sequentially perturbs the fuel flow rate to each can and monitors the resulting changes in NO.sub.x emissions. The controller establishes influence coefficients for each combustor can which are defined as the ratio of the change in NO.sub.

Abstract: An active noise control system which minimizes noise output by creating a secondary, cancelling noise field using vibrational inputs. The system includes one or more piezoceramic actuators mounted to the inner surface of the shroud of an aircraft engine. The actuators can be either mounted directly to the shroud or to one or more noise cancelling members which are resiliently mounted the shroud. Transducers are also provided for sensing the noise generated by the engine and producing an error signal corresponding to the level of noise sensed. A controller sends a control signal to the actuators in response to the error signal, thereby causing the actuators to vibrate and generate a noise field which minimizes the total noise emanating from the engine. The piezoceramic actuators can be thin sheets of piezoceramic material or can be in the form of a piezoelectric-driven mechanical lever arrangement.

Abstract: A trim system reduces NO.sub.x output from a cannular gas turbine by trimming fuel flow rates to equalize the fuel-air ratio in each combustor can. The system includes a main valve fluidly connected to the fuel inlet of each can and a trim valve fluidly connected to each fuel inlet in parallel with the main valve. Each trim valve has a flow resistance which is about 30-100 times greater than the flow resistance of each main valve. A controller is provided for controlling the opening of the trim valves in response to the level of NO.sub.x emitted from the gas turbine. The controller receives a signal corresponding to the NO.sub.x emissions from a NO.sub.x sensor and outputs suitable control signals to the trim valves. In one preferred control scheme, the controller sequentially perturbs the fuel flow rate to each can and monitors the resulting changes in NO.sub.x emissions. The controller establishes influence coefficients for each combustor can which are defined as the ratio of the change in NO.sub.

Abstract: Apparatus and method for regenerating saturated adsorbents using microwave energy. A saturated adsorbent, such as activated carbon, is fed onto a continuously moving conveyor belt. The conveyor belt transports the carbon to a microwave cavity where the carbon is exposed to microwave energy. The cavity is defined by a containment enclosure which is sealed to prevent radiation leakage. The carbon is heated to a sufficient temperature to cause the contaminants to desorb. The system also includes vents for removing the desorbed contaminants and a holder for receiving the treated carbon discharged from the belt. The microwave cavity may be divided into a number of heating compartments so that the carbon on the belt is heated to different temperatures in each compartment. Each compartment is separately vented, thereby allowing selective recovery of the different contaminants in the carbon.

Abstract: This invention relates to the catalytic reduction of nitrogen monoxide (NO) from highly oxidizing environments. Such catalytic reductions of this type employ the use of small quantities of methane (CH.sub.4) to provide a selective catalytic reduction (SCR) of the NO.

Abstract: Induction heating is utilized to heat polymer matrix composite fiber strands containing electrically conductive fibers. This is accomplished with an apparatus having a helical induction coil and a matching helical guide tube situated adjacent to the induction coil. Composite fiber strands are drawn through the guide tube which is made of a non-electrically conductive, nonmagnetic material. Electrically conductive rollers, positioned next to the entrance and exit of the guide tube, form an electrical circuit with the electrically conductive fibers. This permits currents to be induced in the fibers when the coil is activated, thereby heating the fiber composites. The guide tube can be thermally insulated and flushed with an inert purge gas. Alternatively, the guide tube can be made of an electrically conductive or ferromagnetic material so that heat producing currents are induced in the guide tube, and the composite fiber strands are heated by conduction.

Abstract: A rotary magnetic valve including a cylindrical housing having flow passages in both ends and a magnetically-responsive valve closure assembly rotatively mounted therein. The valve closure assembly includes an armature mounted to rotate about the longitudinal axis of the housing and a shoe slideably disposed on each end of the armature. Each shoe is biased away from the armature and into contact with the inner end surfaces of the housing. A controller assembly is provided to rotate the valve closure assembly between a first position where flow through the valve is prevented and a second position where flow is permitted. The controller includes at least one permanent magnet for biasing the valve closure assembly into one of the positions and an electromagnet for rotating the valve closure assembly into the other position. A three-way valve is also possible.

Abstract: A method and apparatus for converting computed tomography (CT) data into finite element models. The system generates both 2-D and 3-D models using the automatic mesh generators, QUADTREE and OCTREE, which are founded on recursive spatial decomposition. Multiple slices of CT data are obtained by scanning the object to be modeled. The slices are stacked and processed to form a discrete solid model. The discrete solid model is an alternate geometry defined discretely rather than with continuous analytic curves and surfaces but still provides a foundation for automatic mesh generation. Since the QUADTREE and OCTREE automatic mesh generators map naturally to the discrete solid model, the integration of CT technology and automatic mesh generation can be achieved.

Abstract: An open magnet having a frustoconical shaped inner bore is provided for MR imaging. The magnet has a plurality of axisymmetric superconducting coils of differing diameters which are disposed along an axis in order of successively increasing diameters so as to define the frustoconical shape. This shape permits a patient access opening which is much larger than that in conventional cylindrical magnets. The overall length is much less than the length of conventional systems. The combination of wide opening and short length facilitates patient access and presents a feeling of openness. Furthermore, the device can be tilted with respect to horizontal to increase the openness.

Abstract: Low refrigerant charge in a refrigeration system is detected by monitoring the oscillation of the thermal expansion valve. This monitoring is accomplished with a sensor which senses the oscillation of the expansion valve and produces a signal indicative of the valve oscillation. The sensor signal is fed to a monitoring controller which produces a low charge signal whenever the amplitude of valve oscillation falls below a predetermined level, thus indicating low charge conditions. The sensor is preferably a temperature sensor situated at either the outlet or the inlet of the evaporator. The system further comprises a validity evaluation controller for determining when valve oscillation is a valid indication of low charge. The validity evaluation controller analyzes a number of system operating characteristics which affect valve oscillation.

Abstract: A method and apparatus for thermoforming 3-dimensional articles of chosen wall thickness dimensions from a polar polymer sheet. The polymer sheet is dielectrically heated, the heating being controlled to impress a predetermined thermal pattern on the sheet. The thermal pattern is selected in accordance with the amount of stretching to which each area of the sheet is subjected during the subsequent work-forming step, the areas subjected to greater stretching being heated to a lower temperature and vice versa. Thus, the stretching action is balanced and results in accurate control of the wall thickness of the final article.

Abstract: A Si--SiC ceramic layer is bonded to a non-porous SiC substrate with the Si etched from the layer to form a relatively porous surface on the otherwise non-porous high strength SiC substrate. A quartz layer is softened by heating and forced into the pores of the porous layer to form a mechanical bond to the SiC substrate. A refractory metal layer is bonded to the quartz layer to complete the joint. A refractory metal support component is then bonded to the refractory layer whereby the quartz serves as a high strength, high temperature reaction barrier between the metal of the refractory layer and the silicon of the SiC substrate.

Abstract: A method is provided for making a four-piece hollow airfoil. Four metal sheets are preformed into initial shapes. The sheets are sealed together into two pairs or sub-assemblies. Internal cavities are formed in one sheet from each pair prior to sealing. Each sub-assembly is subjected to high temperature and pressure in order to diffusion bond the sheets together at selected points. The cavities of each sub-assembly are then subjected to internal pressure in order to inflate and superplastically deform the sub-assemblies. The inflated sub-assemblies are combined to form a single assembly and the cavities are again subjected to internal pressure in order to bond the sub-assemblies together. The assembly is then exposed to hot isostatic pressing, after which, excess material is machined off.

Abstract: Low charge detection for a refrigeration system is accomplished using a differential pressure sensor which detects superheat at the evaporator exit. The differential pressure sensor includes a casing having a reference chamber containing a reference charge of refrigerant. A pressure responsive snap member is disposed in the casing so as to have one side exposed to the reference chamber and another side exposed to the exit pressure of the evaporator. The snap member is normally biased into a first position but snaps to a second position when the pressure differential across it exceeds a predetermined level. When a low charge condition exits, the evaporator exit will exhibit superheat. Heat conduction through the casing raises the temperature, and thus the pressure in the reference chamber. Thus the pressure differential which causes the snap member to snap to the second position is created.