Showing papers on "Gas compressor published in 1998"

1997 Best Paper Award—Turbomachinery Committee: A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

Abstract: This paper presents a study of stall inception mechanisms in a low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short length-scale disturbance known as a “spike,” and the second with a longer length-scale disturbance known as a “modal oscillation.” In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented that relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: Long length-scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed that explains the type of stall inception pattern observed in a particular compressor. Measurements from a single-stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

An adaptive control for a refrigeration system using pulse width modulated duty cycle scroll compressor

Abstract: A control for a refrigeration system serviced by a special pulse width modulated compressor (30) coupled to a condenser (32)and evaporator (42). The system can be of the distributed type wherein the condenser (32) and compressor (30) may be coupled to service a group of adjacent refrigeration cases, wherein each case would have its own evaporator (42). A controller (52) is coupled to a load sensor (58) for producing a variable duty cycle control signal (54) in which the duty cycle is a function of demand for cooling. Moreover, fuzzy logic technique may be utilized in order to provide self adaptive tuning control for the system.

Turbocharging systems for internal combustion engines

Abstract: An internal combustion engine (11) includes an exhaust gas recirculation system and a two-stage charge air compression system which utilizes a turbocharger (14) with an exhaust gas turbine (15) and a compressor (18); a motor-driven air charge compressor (22) connected to an inlet (20) of the turbocharger compressor (18); a two-input proportioning gas control valve (35) having a first inlet (36) to the atmosphere, a second inlet (37) connected with an EGR conduit and an outlet (39) delivering a mixture of air and exhaust gas to the inlet of the motor-driven compressor (22); and a controller (40) for operating the two-input proportioning gas control valve utilizing an algorithm for controlling the gas control valve to provide an optimal mixture of recirculated exhaust gas and air. Such systems can include a bypass conduit (28) with a check valve between an inlet (21) and outlet (23) of the motor-driven charge air compressor, an EGR cooler (45), an EGR particulate filter or trap (29), and an intercooler (24) for the compressed charge air.

1997 Best Paper Award—Controls and Diagnostics Committee: Active Stabilization of Rotating Stall and Surge in a Transonic Single-Stage Axial Compressor

Abstract: Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular array of twelve separately modulated air injectors. At tip relative Mach numbers of 1.0 and 1.5 the control achieved 11 and 3.5 percent reductions in stalling mass flow, respectively, with injection adding 3.6 percent of the design compressor mass flow. The aerodynamic effects of the injection have also been examined. At a tip Mach number, M tip , of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the prestall perturbations using constant gain feedback. At a M tip of 1.5 (design rotor speed), the prestall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. At design speed, the instability was initiated by approximately ten rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include more than one lightly damped mode, which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150 percent of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor a this speed. A dynamic, model-based robust controller was therefore us to stabilize the multiple modes that co prise the first three harmonic perturbations in this transonic region of operation.

Self-contained energy center for producing mechanical, electrical, and heat energy

Abstract: Various forms of energy, such as mechanical, electrical, and/or heat energy are produced by an energy conversion mechanism (10) which includes a spool (16), the spool (16) including a shaft (22) on which a compressor (18) and turbine (20) are mounted. A generator (23) is operably connected to the energy conversion mechanism (10) for converting mechanical energy into electrical energy. Fuel and air are supplied separately to the compressor (18). A regenerator type heat exchanger (28) has a cold side for conducting compressed air traveling from an outlet of a compressor (18) to an inlet of the turbine (20), a hot side for conducting hot waste gas from the energy conversion mechanism (10), and a rotary core movable sequentially through the cold and hot sides for absorbing heat in the hot side and giving up heat in the cold side. A catalytic combustor (30) combusts the fuel at a location upstream of the turbine (20). During start-up, the catalytic combustor (30) is preheated independently of the heat exchanger (28) by an electric heater (40).

High efficiency environmental control systems and methods

Abstract: A high efficiency environmental control system (10) uses air (16) exhausted from a pressurized cabin (12) to cool compressed air (14) entering the cabin (12). Air (16) exhausted from the cabin (12) may flow directly from the cabin (12) through a heat exchanger (60) which cools the compressed air (14) entering the cabin (12). Alternatively, air (16) exiting the cabin (12) may flow through a turbine (66) which expands and cools the air (16) prior to passing through the heat exchanger (60). The turbine (66) may be used to drive a compressor (68) to provide the compressed air (14) to the cabin (12). Supplemental power to drive the compressor (68) may be provided by a second turbine (70) driven by bleed air (44) from one or more turbine engines (20), or by an electric motor. Bleed air (44) may also be mixed with air from the compressor to provide fresh air to the cabin (12). To further increase efficiency and meet the cooling requirements of the cabin (12) on the ground and at altitude, switch dampers may be employed to selectably vary the flow path of air supplied to the cabin (12).

Design of high-speed low-power 3-2 counter and 4-2 compressor for fast multipliers

Abstract: A 3-2 counter and a 4-2 compressor are the basic components in the partial product summation tree of a parallel array multiplier. A new high-speed and low power design of these components is presented. Owing to the reduction of the internal load capacitance, the counter and compressor have better speed and power performance than other recently proposed approaches.

Extracted, cooled, compressed/intercooled, cooling/combustion air for a gas turbine engine

Abstract: A system for cooling hot section components of a gas turbine engine. The cooling system includes a plurality of compressors, or compression train, and an intercooler disposed between each adjacent pair of compressors so as to achieve the desired pressure and temperature of the cooling air at reduced shaft power requirements. The first stage of compression may be provided by the booster, or low pressure compressor, of the engine, with the first intercooler receiving all of the air discharging from the booster. After exiting the first intercooler, a first portion of the booster discharge air is routed to the engine high pressure compressor and a second portion is routed to an inlet of the second compressor of the cooling air compression train. The compressed, cooled air exiting the last, downstream one of the compressors is used for cooling at least a first hot section component of the engine.

Motor-driven centrifugal air compressor with internal cooling airflow

Abstract: A motor-driven compressor comprises a motor (13) that is carried by a motor-enclosing housing portion (16), a compressor wheel (11) that is driven by the motor within a second housing portion (17) forming a pressurized enclosure, and means (20) for providing a flow of cooling air for the motor from the pressurized compressor housing portion to the motor-enclosing housing portion. In this motor-driven compressor a small portion of the air flowing through the compressor is directed to the motor housing as cooling air for the motor windings.

Compressor system and method and control for same

Abstract: An electronic control system (52) and method for controlling and preventing damage to a stand alone or network of oil free, two stage compressor packages (50). To prevent the occurrence of a high temperature condition and subsequent seizure of the compressor, pressure (76, 72) and temperature (60, 62, 58) sensors are disposed at strategic locations in the compressor package. The electronic control system (52) detects and predicts failure based on pressure and temperature differentials and shuts the compressors (54, 56) down before actual failure. The electronic control system (52) records the shutdown parameters in non volatile memory and displays a reason for shutdown. A plurality of electronic control systems (52) can be connected in a peer-to-peer network to coordinate control of a plurality of compressors connected to the same air distribution system.

Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part I—Radial Distortion

Abstract: This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper. First, the effects of radial distortion on the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer function indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7 percent relative to the case with inlet distortion and no injection. Use of a robust H{sub {infinity}} controller with unsteady nonaxisymmetric injection achieved a further reduction in stalling mass flow of 7.5 percent, resulting inmore » a total reduction of 17.2 percent.« less

Apparatus and method for forming oxygen-enriched gas and compression thereof for high-pressure mobile storage utilization

Abstract: An oxygen concentrator is utilized in combination with a compressor to provide a highly enriched and compressed oxygen gas in a mobile container such as a gas cylinder. The combination and method of production provides for the facile preparation of an enriched source of oxygen for use by an ambulatory or wheelchair-confined patient. The oxygen concentrator utilizes two or more molecular sieves to provide a breathable gas of from approximately 80 to about 98 percent oxygen from atmospheric air. The oxygen-enriched gas is stored in a concentrator product tank and can be prioritized so as to supply a patient with a proper amount and concentration of oxygen and secondarily to supply any surplus or excess enriched oxygen to a compressor. The compressor utilizes multiple stages to produce the highly compressed oxygen-enriched gas and utilizes a two-part piston at low rpm to enhance low wear and low noise. The multiple pistons of the compressor can either all rotate at one RPM or in an alternative embodiment, at least a first piston can rotate at a higher RPM than any remaining pistons. Desirably, at least the initial piston of the alternative embodiment is driven by one drive shaft source with one or more other remaining pistons being driven by a second drive shaft.

Method of operating a combustion turbine power plant having compressed air storage

Abstract: A method is provided to ensure that a combustion turbine power generation system may operate at maximum allowable power at elevated ambient temperature and/or at low air density. The method includes providing at least one combustion turbine assembly including a compressor, an expansion turbine operatively associated with the compressor, an upgraded generator coupled with the expansion turbine; a combustor feeding the expansion turbine; flow path structure fluidly connecting an outlet of the compressor to an inlet of the combustor; a compressed air storage; a charging compressor for charging the air storage; charging structure fluidly connecting an outlet of the charging compressor with an inlet to the air storage; connection structure fluidly connecting an outlet of the air storage to an inlet of the combustor; and valve structure associated with the connection structure and the charging structure to control flow through the connection structure and the charging structure, respectively. The valve structure is controlled to selectively permit one of the following modes of operation: (1) a combustion turbine mode of operation wherein air compressed from the compressor moves through the flow path structure to the combustor feeding the expansion turbine such that the expansion turbine drives the generator, (2) a compressed air augmentation mode of operation wherein compressed air from the air storage is supplied through the connection structure to the combustor in addition to the compressed air passing through the flow path structure to the combustor, which increases mass flow of compressed air and gas to the expansion turbine and thus permits the upgraded generator to provide an increased power due to the additional compressed air suppled to the expansion turbine, and (3) an air storage charging mode of operation wherein compressed air from the charging compressor moves through the charging structure to charge the air storage.

High frequency rotary pressure swing adsorption apparatus

Abstract: Pressure swing adsorption separation of a feed gas mixture, to obtain a purified product gas of the less strongly adsorbed fraction of the feed gas mixture, is performed with a cooperating set of "N" adsorbers in a rotary assembly, with each adsorber communicating at its product end directly to a rotary cyclic displacement chamber, and at its feed end by rotary distributor valve ports to a rotary piston feed compressor and a rotary piston exhaust vacuum pump. The compressor and vacuum pump are integrated with the cycle, and rotate at "N" times the cycle frequency. Alternative adsorber configurations for high frequency operation are disclosed.

Comparative performance evaluation of positive displacement compressors in variable-speed refrigeration applications

Abstract: This paper presents the results of investigations into the performance of positive-displacement refrigeration compressors for variable-speed capacity control applications Compressors tested include an open-type reciprocating, a semi-hermetic reciprocating and an open-type rotary vane All three compressors were tested under constant and variable head-pressure operating conditions The results indicate that all three compressors were designed for maximum efficiency at nominal speed At constant head-pressure only the open-type compressor exhibited an improvement in the COP at reduced speeds With variable head-pressure-control all three compressors showed an increase in the COP with a reduction in speed The results of an energy analysis carried out based on the experimental results and weather conditions for two locations representing temperate and warm weather conditions showed that all three compressors when operated at variable speed offer energy savings compared to their fixed-speed counterparts The analysis has shown the open-type reciprocating compressor to be the most efficient system offering 12% savings when operating in a temperate climate and 24% savings when operating in a warm climate

Charge air systems for four-cycle internal combustion engines

Abstract: Charge air systems may include a small electric motor-driven compressor (42) for supplying charge air to four-cycle internal combustion engines (10), including systems with turbocharger charge air compressors (64) in series and parallel connection. The disclosed charge air systems can provide an effective charge air flow path to the internal combustion engine and avoid air flow restrictions at high engine operating speeds.

Gaseous fuel compression and control system

Abstract: A gaseous fuel compression and control system is disclosed which utilizes one or more helical flow compressor/turbine integrated with a permanent magnet motor/generator and driven by a torque controlling inverter to compress or expand gaseous fuels, precisely control fuel pressure and flow, and precisely control the operations (speed, combustion temperature and output power) of a gaseous fuel fired turbogenerator.

Semi-automatic compressor controller and method of controlling a compressor

Abstract: The present invention provides a controller for an air compressor system. The air compressor system includes an air compressor, control unloaders on the air compressor to prevent the air compressor from compressing gases when signaled to unload, an electric motor for driving the air compressor, and a tank for receiving and storing compressed gases from the air compressor. The controller has an adjustable pressure switch to raise or lower the discharge pressure. The differential pressure is pre-set in the pressure switch. The controller includes two methods of operating the air compressor, each of which is manually selected by operating a switch that will designate start/stop control or automatic dual control at the option of the operator. The start/stop control will start the motor when the pressure in the system reaches a predetermined low point. When the preselected high pressure point is reached, a signal is sent to the motor to stop, thereby ending the compressing cycle. When the automatic dual control mode is selected and when the high pressure point is reached, the compressor unloaders are actuated, the motor continues to run and the compressor operates in the unloaded or idling mode. When the aforementioned unloaders are actuated, the unloader time accumulates and times the manually set idle period the compressor will run before shutting down the motor. If during the idle time the system pressure drops to the preselected low point, the unloaders are disabled and the compressor begins to pump to satisfy the compressed air load requirement. The controller also includes a power on/off switch, a running timer, an emergency shutdown with indicator light with remote signaling capability, and an autodrain feature based upon production of compressed air. The controller is adaptable to both rotary screw and reciprocating air compressors.

Endwall Blockage in Axial Compressors

Abstract: This paper presents a new methodology for quantifying compressor endwall blockage and an approach, using this quantification, for defining the links between design parameters, flow conditions, and the growth of blockage due to tip clearance flow. Numerical simulations, measurements in a low speed compressor, and measurements in a wind tunnel designed to simulate a compressor clearance flow are used to assess the approach. The analysis thus developed allows predictions of endwall blockage associated with variations in tip clearance, blade stagger angle, inlet boundary layer thickness, loading level, loading profile, solidity and clearance jet total pressure. The estimates provided by this simplified method capture the trends in blockage with changes in design parameters to within 10%. More importantly, however, the method provides physical insight into, and thus guidance for control of, the flow features and phenomena responsible for compressor endwall blockage generation.© 1998 ASME

Method for providing emergency reserve power using storage techniques for electrical systems applications

Abstract: A combustion turbine power generation system includes a modified simple cycle combustion turbine power generation system optimized for a "hot" stand-by reserve mode of operation and having a power shaft assembly including a compressor, an expansion turbine, and a double-ended motor/generator between the compressor and the turbine. The motor/generator has a turbine driving clutch structure on one end thereof and a compressor driving clutch structure on the other end thereof. A combustor feeds the expansion turbine. The power generation system includes an additional system having a boost compressor, an intercooler feeding cooled air to the boost compressor an electric motor for driving the boost compressor, and aftercooler downstream of the boost compressor. A compressed air energy storage is downstream of the aftercooler. The additional system is integrated with the modified simple cycle combustion turbine power generation system to provide (i) a primary mode of operation--a hot stand-by mode, when the plant is ready to deliver an emergency power at full turbine power of specified duration within a few seconds; (ii) a cold start-up mode of operation, when the plant is ready to deliver an emergency power at full turbine power of specified duration within a few minutes, depending on the specifics of the turbine design, (iii) an emergency power supply mode, when the plant provides emergency power at full turbine power of specified duration; (iv) a combustion turbine emergency power supply mode, when the plant provides approximately 50% of full turbine power of unlimited duration during long term interruptions of the power supply; and (v) a storage charging mode of operation to charge the air storage.

The Relationship of Optimum Heat Exchanger Allocation and Minimum Entropy Generation Rate for Refrigeration Cycles

Abstract: This paper investigates the effect of heat exchanger allocation on overall system performance using both reverse Carnot and vapor compression refrigeration cycle models to calculate system performance and entropy generation rate. The algebrai­ cally simple constraints applied in previous studies are shown to be justifiable. The vapor compression model considers nonideal compressor performance, compressor volumetric efficiency, refrigerant properties, and throttling, in addition to mechanistic heat exchanger models. The results support the conclusions of previous studies in that maximum performance is observed when the condenser and evaporator thermal sizes are approximately equal. For air-to-air systems, this result indicates that the areas of the heat exchangers should be approximately equal. However, it is found that minimizing the entropy generation rate does not always result in the same design as maximizing the system performance unless the refrigeration capacity is fixed. Minimizing the entropy generation rate per unit capacity is found to always corre­ spond to maximizing the coefficient of performance of refrigeration systems.

On gearing of helical screw compressor rotors

Abstract: Twin-screw compressor rotors are effectively helical gears. When these are formed from a hobbing cutter, the hobbing tool and the rotor together constitute a pair of crossed helical gears. ...

Pressure boosted compressor cooling system

Abstract: A gas turbine engine cooling system for providing cooling air to engine components includes a core engine and, in downstream serial flow relationship, a high pressure compressor, a combustor, and high pressure turbine. A first flowing system is used for flowing a portion of the pressurized air to a heat exchanger to cool the pressurized air and provide the cooling air and a second flowing system is used for flowing a first portion of the cooling air to a compressor impeller operably connected to a compressor disk of the high pressure compressor for boosting pressure of the first portion of the cooling air. A second portion of the cooling air is supplied to turbine cooling. The heat exchanger may be a fuel to air heat exchanger for cooling the portion of the pressurized air from the first flowing means with fuel. Preferably, a first plurality of diffuser vanes extending radially across the core flowpath and each includes at one radial vane airflow passage for conveying the cooling air across the core flowpath to the compressor impeller and the turbine cooling apparatus.

Thermodynamic Optimization of a Gas Turbine Power Plant With Pressure Drop Irreversibilities

Abstract: In this paper we show that the thermodynamic performance of a gas turbine power plant can he optimized by adjusting the flow rate and the distribution of pressure losses along the flow path. Specifically, we show that the power output has a maximum with respect to the fuel flow rate or any of the pressure drops. The maximized power output has additional maxima with respect to the overall pressure ratio and overall temperature ratio. When the optimization is performed subject to a fixed fuel flow rate, and the power plant size is constrained, the power output and efficiency can be maximized again by properly allocating the fixed total flow area among the compres­ sor inlet and the turbine outlet.

Linear motor compressor

Abstract: A linear motor and/or compressor (10; 100; 300; 500; 600) comprises a housing (20; 120; 311; 511) fitted with a number of electromagnets (40, 40'; 140, 140'; 315, 315', 316; 515a-515c; 635a-635d), a shuttle (50; 150; 350; 550; 650) with a central guide (30, 30'; 130; 356, 356'; 520; 655) for keeping it coaxial with the electromagnets and a suspension mechanism for the shuttle including mechanical spring, gas spring and magnetic spring arrangements. The electromagnets form a number of axially exposed magnetic gaps to interact with axially exposed magnetic gaps formed on the shuttle to cause it reciprocate by push-and-pull forces. A phase difference can be produced between the electromagnets to improve shuttle suspension. The central guide can be made hollow to circulate a coolant to cool the compressor from inside. A multi-stage compression arrangement is formed between the shuttle and the electromagnets so that the compressor can work in a double-acting manner to compress the process fluid progressively for a high pressure output. A further suspension (640, 640') can be used for the stator (630) so as to ensure the machine's vibration-free operation.

Reduced pressure carbon dioxide-based refrigeration system

Abstract: There is disclosed an novel refrigeration apparatus and a method of refrigeration. The novel refrigeration apparatus comprises a desorber/evaporator, a gas/liquid compressor operatively connected to said desorber/evaporator, a resorber/condenser operatively connected to said gas/liquid compressor, an expansion device operatively connected to said resorber/condenser and to said desorber/evaporator and a circulating refrigerant comprising carbon dioxide and a liquid co-fluid in which the carbon dioxide is differentially soluble. The refrigeration method comprises compressing carbon dioxide gas and a liquid co-fluid in a gas/liquid compressor to an increased pressure, such that carbon dioxide at least partially dissolves in the liquid co-fluid, and reducing the pressure on the liquid co-fluid containing the dissolved carbon dioxide so that dissolved carbon dioxide comes out of solution with the liquid co-fluid, and recirculating the gaseous carbon dioxide and liquid co-fluid to the gas/liquid compressor.

Apparatus for passive hypoxic training and therapy

Abstract: This invention is an apparatus (10) for passive hypoxic training or therapy which provides a user hypoxic (low oxygen) gas mixture having optimal carbon dioxide content for breathing stimulation and a comfortable humidity level. The oxygen content of air is reduced by being passed through a pressure swing adsorption separator. The air is then pressurized by a compressor (13) and delivered in alternating sequence to cartridges (20, 21) having a molecular sieve material which adsorbs nitrogen, carbon dioxide and water vapor. The remaining hypoxic gas mixture is recovered by de-pressurization of the cartridges and is delivered to a user through a surge tank (27), filter (28), breathing bag (30), and respiratory mask (35).