Abstract: Pulse width modulation is used to control the flow rate through a solenoid expansion valve in a refrigeration system. A first temperature sensor is located near the evaporator inlet, and a second temperature sensor is disposed in a compartment to be cooled. A controller is included for controlling the duty cycle of the pulse width modulated solenoid valve. The controller receives inputs from the two temperature sensors and controls the valve duty cycle based on the difference of the two temperatures. The second temperature sensor is preferably located on the back wall of the compartment and can be adjacent to the compartment air inlet, adjacent to the compartment air outlet, or between the air inlet and air outlet.

Abstract: A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers 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 drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

Abstract: A signal enhancement system for separating a composite diagnostic signal detected in a rotating machine into component signals representative of the contributions to the composite signal of a number of independent sources. The signal enhancement system includes at least one signal subtraction loop having a transducer which produces a reference signal based on the rotational speed of a rotating shaft in the machine and an adaptive filter connected to the transducer. The adaptive filter processes the reference signal to produce a component signal which closely approximates the contribution of the rotating shaft to the composite signal. A summer is also included which subtracts the component signal from the composite diagnostic signal to produce a second component signal. Both the first and second component signals are provided as outputs of the system.

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 an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is 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 ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

Abstract: Pulse width modulation is used to control the flow rate through a solenoid expansion valve in a refrigeration system. A device for sensing suction line temperature is provided, and a controller is included for controlling the duty cycle of the pulse width modulated solenoid valve. The controller receives input from the suction line temperature sensing device as a basis for controlling the duty cycle. The suction line temperature sensing device may be a temperature sensor disposed on the suction line at the midpoint of the heat exchanger between the suction line and the liquid line. Alternatively, the suction line temperature sensing device may include a first temperature sensor disposed on the liquid line at one end of the heat exchanger and a second temperature sensor disposed on the liquid line at another end of the heat exchanger.

Abstract: Microwave heating is used to desorb successive batches of contaminated adsorbent. The apparatus includes first and second stations and an adsorbent carrier tray displaceable between the two stations. Adsorbent is loaded and unloaded from the tray in the first station and heated with microwave energy in the second station. The tray is loaded by passage under a feed hopper, thereby providing an even bed of adsorbent in the tray. Unloading is performed by rotating the tray to an inverted position so that the adsorbent falls into a bin below. The second station includes an oven chamber which is swept with a purge gas to remove gaseous sorbates desorbed from the adsorbent. The tray can include a gas-permeable adsorbent support structure to facilitate passing purge gas and gasification reactants through the adsorbent bed.

Abstract: Induction heating is utilized to heat polymer matrix composites containing electrically conductive fibers. This is accomplished with an apparatus having a mandrel for supporting a composite workpiece and a helical induction coil disposed around the mandrel. The mandrel, workpiece and induction coil are disposed in an autoclave. The mandrel is a hollow, porous member having a port formed therein which is connected to a vacuum. A vacuum bag is hermetically sealed on the mandrel so as to define an enclosure over the workpiece. A power source is connected to the induction coil and, when activated, causes the coil to generate an oscillating magnetic field lying along the longitudinal axis of the mandrel. The magnetic field induces heat-generating eddy currents in the fibers of the workpiece which are oriented orthogonally to the magnetic field.

Abstract: This invention relates to a gas burner which employs a two stage flame stabilizer. At low input rates, a fully aerated flame is stabilized at the surface of a porous material. At higher input rates, the flame blows off and is held by flame stabilization tabs. Such structures of this type, generally, operate over a very wide range of input rates and employ a highly aerated flame which reduces the flame temperature, slows NOx production, and increases the overall reaction rate by shortening the flame while reducing carbon monoxide (CO) caused by flame impingement.

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.