Showing papers on "Gas compressor published in 1991"

Method of operating a transport refrigeration unit

Abstract: A method of operating a transport refrigeration system having a refrigerant compressor driven by an internal combustion engine. Microprocessor based electrical control maintains the temperature of a conditioned space at a desired set point via heating, cooling and null cycles, with the engine being started and stopped, as required. During the engine starting process, a suction line modulation valve, if used, is closed, engine pre-heat time is selected, including using engine temperature to access a look-up table, and current draw is checked during pre-heat. Excessive current terminates pre-heat. Control diagnostics checks the voltage level on both sides of a refrigerant high pressure switch, before initiating engine cranking. Prior to stopping the engine, a control option initiates a heating cycle for a short time when null is being entered from a cooling cycle, to warm the evaporator and prevent premature starting of the engine.

Economizer control with variable capacity

Abstract: A refrigeration circuit is provided in which economizer control is provided together with variable capacity control. Constant cooling is achieved by controlling an economizer cycle responsive to the suction pressure of the compressor. Additionally, compressor discharge temperature is controlled by controlling the portion of liquid refrigerant supplied to the interstage line.

Motor controls, refrigeration systems and methods of motor operation and control

Abstract: A method of operating a brushless motor having a stationary assembly with at least two different energizable windings for producing spaced apart magnetic fields in time sequence, and a rotor adapted to rotate in response to the magnetic fields. The method includes the steps of simulating rotor position in accordance with the back emf condition of at least one winding, energizing a selected one of the windings in accordance with the simulated rotor position, sensing an underspeed condition when the motor speed is less than a minimum value for a length of time, and preventing energization of any of the windings when the motor speed is less than the minimum value for the length of time. An electrically commutated motor controller apparatus controls the speed of a variable speed motor compressor driven by an electrically commutated motor. A controller circuit includes a circuit for producing feedback signals representative of a back emf of the motor. A compressor speed circuit generates actual compressor speed signals from the feedback signals produced by the controller circuit. A duty cycle generator produces a speed control signal as a function of the actual compressor speed signals, and the speed control signal is transmitted to the controller circuit for adjusting the speed of the electrically commutated motor driven compressor. Other motor controls, refrigeration systems and methods of control and operation are also disclosed.

Gas turbine engine module assembly

Abstract: A gas turbine engine compressor module subassembly construction and associated assembly method and tooling includes a threaded inner bore on the first stage compressor adapted to receive a tubular tool that slips axially between the compressor bores and the engine central shaft Securement of the accessible tooling to the module's stationary structure permits assembly and handling of the module independently of the engine shaft

Method and device for high side pressure regulation in transcritical vapor compression cycle

Abstract: High side pressure in a transcritical vapor compression cycle system is regulated by varying a liquid inventory of a low pressure refrigerant receiver provided in a circuit of the system. The circuit includes a compressor, a gas cooler, a throttling valve, an evaporator and the receiver connected in series in a closed circuit operating at supercritical pressure in a high pressure side of the circuit. The degree of opening of the throttling valve is controlled to regulate the high side pressure in the circuit. It is possible to control capacity, and it also is possible to achieve minimum energy consumption for a given capacity requirement by regulating high side pressure.

Gas turbine engine powered aircraft environmental control system and boundary layer bleed

Abstract: An aircraft gas turbine engine is provided with a starting air turbine that is directly connected through the starter gearbox to the high pressure (HP) shaft and is provided with an apparatus to extract excess energy from engine compressor bleed air, return it to the engine, and to start the engine with compressed air from starting air sources, and to cool and provide compressed air for powering the Environmental Control System (ECS) and using the bleed air for cabin refreshening. The air turbine may be connected to a nacelle boundary layer bleed compressor to bleed boundary layer air from a forward portion of the nacelle to reduce nacelle surface drag. The ECS may be provided with a wing boundary layer bleed means which uses a cooling air fan in the ECS to draw cooling air through the heat exchangers in the ECS pack from the boundary layer air from a forward portion of the aircraft's wing to reduce its surface drag.

Aircraft gas turbine engine bleed air energy recovery apparatus

Abstract: An environmental control system for supplying aircraft or cabin air to an aircraft is provided with a propulsive engine compressor bleed supply means and an ECS bleed air flow control means which includes an energy recovery means for using the unrequired or unused energy to pump boundary layer air from the surface of the aircraft, such as from the engine nacelle, and exhaust this air rearward of the engine to produce thrust, thus returning some of this unused energy to the propulsive engine.

Active Stabilization of Centrifugal Compressor Surge

Abstract: Active suppression of centrifugal compressor surge has been demonstrated on a centrifugal compressor equipped with a servo-actuated plenum exit throttle controller. The control scheme is fundamentally different from conventional surge control techniques in that it addresses directly the dynamic behavior of the compression system to displace the surge line to lower mass flows. The method used is to feed back perturbations in plenum pressure rise, in real time, to a fast-acting control valve. The increased aerodynamic damping of incipient oscillations due to the resulting valve motion allows stable operation past the normal surge line. For the compressor used, a 25 percent reduction in the surge point mass flow was achieved over a range of speeds and pressure ratios. Time-resolved measurements during controlled operation revealed that the throttle required relatively little power to suppress the surge oscillations, because the disturbances are attacked in their initial stages. Although designed for operation with small disturbances, the controller was also able to eliminate existing, large-amplitude, surge oscillations. Comparison of experimental results with theoretical predictions showed that a lumped parameter model appeared adequate to represent the behavior of the compression system with the throttle controller and, perhaps more importantly, to be used in the design of more sophisticated control strategies.

Turbine disk interstage seal system

Abstract: A turbine engine of the type having a compressor section, combustor section and high-pressure turbine section in which compressor air is conveyed internally of the compressor and turbine sections to cool the turbine interstage volume, a first stage turbine disk includes a shaft supporting a second stage turbine disk, a turbine interstage seal is secured by boltless engagement to the disks and is prestressed to resist flexure, and the first stage disk carries a forward seal attached by boltless connections. The interstage seal includes a bore having a rearwardly-extending arm engaging the aft shaft in a bayonet connection to prevent deflection of the bore and includes passages to allow air flow around the bore. The forward seal includes radially-extending vanes to convey cooling air along the disk, and is secured by inward and outward bayonet connections, the inward connection including locking pins which are arranged to perform a balancing function.

Noise control of air conditioner

Abstract: An air conditioning apparatus having a condenser fan, an evaporator fan, a compressor, at least two motor for driving the fans and the compressor, and being responsive to vibration of the apparatus to control the speed of each motor to reduce the vibration. In its preferred embodiments, the apparatus performs a test to determine optimum speeds of the motors to minimize the vibration. The apparatus uses a microcomputer, operative during the test to change the speed of at least one of the motors to each of a plurality of different speed values within a predetermined speed range, and at least one vibration detector. The detector detects values of the vibration when the motors are operating at the different speed values. At the end of the test, the motors are controlled to operate at the speed value at which the vibration is minimized.

Propulsion system for a vertical and short takeoff and landing aircraft

Abstract: The invention is a propulsion system for a V/STOL type aircraft. In detail, the invention comprises a turbofan engine (31) including a fan section (46), compressor section (65), combustion section (74), turbine section (58) and nozzle section (34). The turbine section (58) comprises a low-pressure turbine portion (56) coupled to and driving the fan section (46) and a high-pressure turbine portion (68) coupled to and driving the compressor section (65). A lift fan (36) is coupled to the fan section (46) by means of a drive shaft (52). A clutch (108) is incorporated for de-coupling the lift fan (36) from the fan section (46). A mechanism (80) is incorporated for extracting additional power from the low-pressure turbine portion (56) of the turbine section (58) to drive the lift fan (36) that augments the basic engine thrust for V/STOL operation.

Active Suppression of Rotating Stall and Surge in Axial Compressors

Abstract: This paper reports on an experimental program in which active control was successfully applied to both rotating stall and surge in a multi-stage compressor. Two distinctly different methods were used to delay the onset of rotating stall in a four stage compressor using fast acting air injection valves. The amount of air injected was small compared to the machine mass flow, the maximum being less than 1.0%. In some compressor configurations modal perturbations were observed prior to stall. By using the air injection valves to damp out these perturbations an improvement of about 4.0% in stall margin was achieved. The second method of stall suppression was to remove emerging stall cells by injecting air in their immediate vicinity. Doing this repeatedly delayed the onset of stall, giving a stall margin improvement of about 6.0%. Further studies were conducted using a large plenum downstream of the compressor to induce the system to surge rather than stall. The resulting surge cycles were all found to be initiated by rotating stall and therefore the stall suppression systems mentioned above could also be used to suppress surge. In addition, it was possible to arrest the cyclical pulsing of a compressor already in surge.Copyright © 1991 by ASME

Integrated air separation plant-integrated gasification combined cycle power generator

Abstract: An integrated cryogenic air separation unit power cycle system is disclosed wherein the air separation unit (ASU) is operated at elevated pressure to produce moderate pressure nitrogen. The integrated cycle combines a gasification section wherein a carbon source, e.g., coal is converted to fuel and combusted in a combustion zone. The combustion gases are supplemental with nitrogen from the air separation unit and expanded in a turbine. Air to the cryogenic air separation unit is supplied via a compressor independent of the compressor used to supply air to the combustion zone used for combusting the fuel gas generated in the gasifier system.

Energy recovery system for large motor vehicles

Abstract: An energy recovery system for wheeled vehicles is characterized by a compressor/expander which operates as an expander in the run mode to assist the engine in driving the vehcile and as a compressor in the braking mode to store braking energy. A heat exchanger, a boiler drum, and a flash chamber transfer heat from the vehicle exhaust to a working fluid for generating high and low pressure vapor. The boiler drum stores heated and vaporized liquid and supplies high-pressure vapor to the inlet port of the compressor/expander during the run mode. The flash chamber supplies low-pressure steam to the inlet port of the compressor/expander during the braking mode. Storage tanks are provided for storing and passing low-pressure vapor to the input of the compressor/expander during the run mode.

Flow control method and means

Abstract: The method controls gas flow in an axial flow compressor in which the flow at one or more chosen station in the direction of flow through the compressor is sensed at a series of circumferentially spaced positions. Flow variations above a predetermined limit are evaluated to initiate a response if a disturbance above a predetermined acceptable level is detected. When such a disturbance is detected, higher pressure gas bled from downstream is injected at a station to supplement the main gas flow. An incipient rotating stall cell will appear as a variation occurring sequentially at the circumferentially spaced positions. By responding to such a condition with a pressure injection, it is found possible to suppress both rotating stall and surge conditions in the compressor before this disturbance develops fully. The same method can be arranged to counter steady state distortion.

Dynamic Control of Centrifugal Compressor Surge Using Tailored Structures

Abstract: A new method for dynamic control of centrifugal compressor surge is presented. The approach taken is to suppress surge by modifying the compression system dynamic behavior using structural feedback. More specifically, one wall of a downstream volume, or plenum, is constructed so as to move in response to small perturbations in pressure. This structural motion provides a means for absorbing the unsteady energy perturbations produced by the compressor, thus extending the stable operating range of the compression system. In the paper, a lumped parameter analysis is carried out to define the coupled aerodynamic and structural system behavior and the potential for stabilization. First-of-a-kind experiments are then conducted to examine the conclusions of the analysis. As predicted by the model and demonstrated by experiment, a movable plenum wall lowered the mass flow at which surge occurred in a centrifugal compression system by roughly 25 percent for a range of operating conditions. In addition, because the tailored dynamics of the structure acts to suppress instabilities in their initial stages, this control was achievable with relatively little power being dissipated by the movable wall system, and with no noticeable decrease in steady-state performance. Although designed on the basis of linear system considerations, the structural control is shown to be capable of suppressing existing large-amplitude limit cycle surge oscillations.

Active Control of Rotating Stall in a Low Speed Axial Compressor

Abstract: The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.Copyright © 1991 by ASME

Power plant for generation of electrical power and pneumatic pressure

Abstract: A power plant (10) for generating electric power and pneumatic pressure is disclosed which includes an internal combustion engine (20), an electrical generator (24), and a compressor (28) and pneumatic supply tanks (40). Both the electrical generator (24) and the compressor (28) are driven by the engine (20); however, the engine drive is so coupled and controlled that the engine (20) drives the generator (24) as its primary load, and the compressor (28) as its secondary load and apportions the engine power between these units according to need. When the generator (24) uses all the engine power, pneumatic power is supplied by the pneumatic supply tanks (40), permitting a smaller than normal drive engine. A quick start and quick kill mechanism is provided for the engine by using the air supply from the pneumatic supply tanks (40) and an air motor (34), and a time delay shut down relay (110) when no power is being used. Also, the generator (24) can be used as an electric drive motor for the compressor (28) in place of the internal combustion engine (20), where 110 volt ac power is available on the job site.

Surge Dynamics in a Free-Spool Centrifugal Compressor System

Abstract: Turbocharger surge has been investigated in a radial impeller-vaneless diffuser free-spool system. Several different aspects are addressed. First, two very different compression systems, one with a large downstream volume and one with the smallest possible downstream volume, are employed to examine stall initiation phenomena as well as the behavior of the compressor characteristics when operating in surge. The measurements show impeller stall at the inducer tips to be a key phenomena in initiating surge. The inducer stall is stationary and asymmetric, due to the presence of the volute, and is most severe near the volute tongue angular position. The compressor characteristic in the large volume system (which gave surge) is observed to be flatter and to lag that in the stabilized small volume system. The difference arises because of the slow development time and differing circumferential extent of the inducer stall present at a given mass flow.A nonlinear simulation of the system is also presented. The model deviates from previous treatments of unsteady flow in compressor systems in that the assumption of constant rotor speed is relaxed. Including a time lag on the order of the compressor throughflow time, together with proper treatment of speed variations, is shown to dramatically improve agreement with the observed surge behavior.Copyright © 1991 by ASME

Low noise fan assembly

Abstract: A gas turbine engine rotor assembly such as a fan or compressor includes a plurality of rotor blades spaced axially from a plurality of stator vanes inside an annular duct. The number of vanes is selected for a predetermined number of blades for obtaining substantially equal values of a cut-off ratio for at least two blade passing frequency harmonics for reducing spinning mode noise from the duct.

Gas dissolving and releasing liquid treatment system

Abstract: An improved gas dissolving and releasing liquid treatment system involving the use of multi-stages gas dissolving pressure vessel and the use of a pressurized water release assembly and an open vessel is described The gas dissolving and releasing liquid treatment system includes a liquid pressure pump, a pressure vessel, a gas injector, an inlet nozzle assembly, a gas compressor, gas regulators, gas flow meters, pressure gauges, a safety valve, a bleed-off point, feeders, pumps, a pressurized water release unit, a liquid flow meter, an open vessel, sludge removal means, and air emission control means More than one gases introduced at different inlets are dissolved simultaneously and efficiently in the pressure vessel under controlled high pressure and high rotating velocity The improved liquid treatment system is compact, simple and cost-effective, and is applied to ozonation, chlorination, recarbonation, oxygenation, bio-oxidation, nitrogenation, aeration, and flotation processes Chemicals and/or microorganisms are dosed to the present invention to facilitate the required chemical and/or biochemical reactions for liquid treatment

Turbine cooling system

Abstract: Cooling air delivery systems for gas turbine engines are used to increase component life and increase power and efficiencies. The present system increases the component life and increases efficiencies by better utilizing the cooling air bled from the compressor section of the gas turbine engine. For example, a flow of cooling air is directed to a plurality of airfoils having a leading edge and includes a cooling path therein each of the plurality of blades in which is positioned a device which causes the cooling air to swirl and more effectively absorb heat and cool the leading edge of the airfoil.

Aircraft cabin air conditioning system with improved fresh air supply

Abstract: An improved air conditioning system is provided for an aircraft, particularly with respect to providing an enhanced supply of fresh air to the aircraft cabin or cockpit. The system includes a dual inlet turbine driven at least in part by pressurized bleed air from an aircraft engine, wherein the turbine expands and cools the air preparatory to supply thereof as conditioned air to the aircraft cabin. During relatively low altitude operation, the bleed air flow is supplemented by compressed fresh air discharged from a turbine-driven compressor and supplied to the dual inlet turbine. At relatively higher altitude operation, this fresh air flow is bypassed around the turbine for addition to the bleed air flow at a downstream side of the turbine, and the entire nozzle area of the turbine is opened to the bleed air flow.

Detection of a Rotating Stall Precursor in Isolated Axial Flow Compressor Rotors

Abstract: Statistical characteristics of pressure fluctuation on the casing wall of two axial flow compressor rotors have been investigated experimentally to find a precursor of rotating stall. Near stall, the casing wall pressure across a flow passage near the leading edge is characterized by a highly unsteady region where low-momentum fluid accumulates. The periodicity of the pressure fluctuation with blade spacing disappears and an alternative phenomenon comes into existence, which supports the disturbance propagating at a different speed from the rotor revolution. The precursor of rotating stall can be detected by monitoring collapse of the periodicity in the pressure fluctuation. To represent the periodicity qualitatively, a practical detection parameter has been proposed, which is easily obtained from signals of a single pressure sensor installed at an appropriate position on the casing wall during operation of a compressor.

Integrated turbine generator

Abstract: An integrated turbine-generator or compressor-motor having a turbine/compressor mounted radially inwardly of a generator/motor or a generator/motor mounted inward of the turbine/compressor with the turbine, for example, sharing a common rotor with the generator.

Method and apparatus for detecting low refrigerant charge

Abstract: In an air conditioning system, thermistors measure evaporator inlet and outlet temperatures and compressor body temperature. When the differential between inlet and outlet temperatures is below a first threshold and the compressor temperature is above a second threshold, very low refrigerant charge is indicated and the compressor is turned off. Also, if compressor temperature reaches a critical value, the compressor is turned off regardless of the temperature differential across the evaporator.

Turbine inlet silencer

Abstract: In order to reduce noise transmission through the air inlet duct (16) of a turbine engine (10), the air inlet duct (16) provides a non-linear path defined by a bend (24) for air from a source, and the turbine engine (10) includes a sound attenuation assembly (26) in the form of a splitter dissipative silencer disposed near the bend (24) in the air inlet duct (16). More specifically, the turbine engine (10) is such that the splitter dissipative silencer (26) can be formed as a modular assembly (42) removably securable near the bend (24) in the air inlet duct (16) upstream of a radial compressor (12) for removal and/or replacement or availability as an optional component of the turbine engine (10).

Humidity control for regulating compressor speed

Abstract: A control for regulating relative humidity in an enclosure including a thermostat, a relative humidity sensor, a refrigeration compressor and an air blower. The compressor is run at low or high speeds in response to thermostat demand. Whenever the relative humidity is excessive the compressor low speed control is overridden to effect high compressor speed.

Design and Testing of a Controlled Diffusion Airfoil Cascade for Industrial Axial Flow Compressor Application

Abstract: Similar to jet engine development, modern design methods are used today to improve the performance of industrial compressors. In order to verify the loading limits, a cascade profile representative for the first rotor hub section of an industrial compressor has been designed by optimizing the suction surface velocity distribution using a direct boundary layer calculation method. The blade shape was computed with an inverse full potential code and the resulting cascade was tested in a cascade wind tunnel. The experimental results confirmed the design intent and resulted in a low loss coefficient of 1.8 percent at design condition and an incidence range of nearly 12 deg (4 percent loss level) at an inlet Mach number of 0.62.