Showing papers on "Gas compressor published in 1999"

Process for manufacturing or repairing turbine engine or compressor components

Abstract: A process of the kind used for producing or repairing a turbine or compressor or fan blade by laser consolidation wherein a laser beam is moved relative to a metal surface and a stream of metal is supplied to the surface via a supply tube, so that said laser beam melts a thin layer of the metal substrate and also melts the metal being delivered to the substrate and thus forms a band of fused metal on said surface, the process being repeated until a desired blade is built up or repaired. The invention is characterized in that the laser beam is orientated at an acute angle to the surface. The supply tube may deliver the metal substantially along a path normal to the surface, with the laser beam being one of a plurality of laser beams each orientated at an acute angle to the surface and spaced around the supply means. Alternatively, a single laser beam may be used at a first acute angle to the surface, with the supply tube being at a second acute to the surface, the laser beam and supply tube being at opposite sides to the normal to the surface.

Centrifugal compressor surge and speed control

Abstract: Previous work on stabilization of compressor surge is extended to include control of the angular velocity of the compressor. A low-order centrifugal compressor model is presented, where the states are mass flow, pressure rise, and rotational speed of the spool. Energy transfer considerations are used to develop a compressor characteristic. In order to stabilize equilibria to the left of the surge line, a close coupled valve is used in series with the compressor. Controllers for the valve pressure drop and spool speed are derived. Semiglobal exponential stability is proved using a Lyapunov argument.

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 percent. 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.

Recommendations for Achieving Accurate Numerical Simulation of Tip Clearance Flows in Transonic Compressor Rotors

Abstract: The tip clearance flows of transonic compressor rotors are important because they have a significant impact on rotor and stage performance. While numerical simulations of these flows are quite sophisticated. they are seldom verified through rigorous comparisons of numerical and measured data because these kinds of measurements are rare in the detail necessary to be useful in high-speed machines. In this paper we compare measured tip clearance flow details (e.g. trajectory and radial extent) with corresponding data obtained from a numerical simulation. Recommendations for achieving accurate numerical simulation of tip clearance flows are presented based on this comparison. Laser Doppler Velocimeter (LDV) measurements acquired in a transonic compressor rotor, NASA Rotor 35, are used. The tip clearance flow field of this transonic rotor was simulated using a Navier-Stokes turbomachinery solver that incorporates an advanced k-epsilon turbulence model derived for flows that are not in local equilibrium. Comparison between measured and simulated results indicates that simulation accuracy is primarily dependent upon the ability of the numerical code to resolve important details of a wall-bounded shear layer formed by the relative motion between the over-tip leakage flow and the shroud wall. A simple method is presented for determining the strength of this shear layer.

Ventilator compressor system having improved dehumidification apparatus

Abstract: An improved compressor system (10) designed for use with a patient assist medical ventilator is provided which includes a compressor (12) and a pressurized gas delivery conduit (14); a hollow fiber membrane dryer (16) is interposed within the conduit (14) for final dehumidification of the pressurized gas and suppression of the dew point thereof In preferred forms, the membrane dryer output air may be recycled via a conduit (50) to the compressor (12) during phases of the system operation, so that such dried, pressurized air may be mixed with ambient air and fed to the compressor (12).

Simulation of Industrial Processes for Control Engineers

Abstract: Introduction Fundamental Concepts of Dynamic Simulation Thermodynamics and the conservation equations Steady state incompressible flow Flow through ideal nozzles Control valve flow Steady-state compressible flow Control valve liquid flow Liquid flow through the installed control valve Gas flow through the installed control valve Accumulation of liquids and gases in process vessels Two-phase systems - boiling, condensation and distillation Chemical reactions Turbine nozzles Steam and gas turbines Steam and gas turbines - simplified model Turbo pumps and compressors Flow networks Pipeline dynamics Distributed components: heat exchangers and tubular reactors Nuclear reactors Process controllers and control valve dynamics Linearization Model Validation Appendices: Comparative size of energy terms Explicit calculation of compressible flow using approximating functions Equations for control valve flow in SI units Comparison of Fisher Universal Gas Sizing Equation, FUGSE, with the nozzle-based model for control valve gas flow Measurement of the internal energy of reaction and the enthalpy of reaction using calorimeters Approximations used in modelling turbine reaction stages in off-design conditions Fuel pin average temperature and effective heat transfer coefficient Conditions for emergence from saturation for P + I controllers with integral desaturation

Knudsen compressor as a micro- and macroscale vacuum pump without moving parts or fluids

Abstract: Applications of Knudsen compressors as both microscale and macroscale vacuum pumps have been investigated. The study is based on a cascade analysis incorporating available transitional thermal transpiration and Poiseuille flow results for slender channels. It was found that the Knudsen compressor is an attractive possibility for microscale pumps down to a pressure of about 1 mTorr and for macroscale pumps to about 0.1 mTorr. A microscale pump for a micromass spectrometer providing a molecule flow rate of 5×1014 molecules/s results in the following pump characteristics: energy use of 2.4 W, pump volume of 13.9 ml at an inlet pressure of 1 mTorr and an energy use of 28.5 mW, and pump volume of 0.16 ml at an inlet pressure of 10 mTorr. A macroscale pump providing a pumping speed of 103 l/s results in a pump with an energy use of 1786 W, and pump volume of 1695 l at an inlet pressure of 0.1 mTorr. Several Knudsen compressor characteristics such as pressure rise, pumping speed, volume, energy use and mass flow...

Compressor pulse width modulation

Abstract: A scroll compressor includes a capacity modulation system. The capacity modulation system has a piston that is connected to the non-orbiting scroll that disengages the non-orbiting scroll from the orbiting scroll when a pressure chamber is placed in communication with the suction chamber of the compressor. The non-orbiting scroll member moves into engagement with the orbiting scroll when the chamber is placed in communication with the discharge chamber. The engagement between the two scrolls is broken when the pressure chamber is placed in communication with fluid from the suction chamber. A solenoid valve controls the communication between the pressure chamber and the suction chamber. By operating the valve in a pulsed width modulated mode, the capacity of the compressor can be infinitely varied between zero and one hundred percent.

A Computational Model for Short-Wavelength Stall Inception and Development in Multistage Compressors

Abstract: This paper presents a computational model for simulating axial compressor stall inception and development via disturbances with length scales on the order of several (typically about three) blade pitches. The model was designed for multistage compressors in which stall is initiated by these “short-wavelength” disturbances, also referred to as spikes. The inception process described is fundamentally nonlinear, in contrast to the essentially linear behavior seen in so-called “modal stall inception”. The model was able to capture the following experimentally observed phenomena: (1) development of rotating stall via short-wavelength disturbances, (2) formation and evolution of localized short-wavelength stall cells in the first-stage of a mismatched compressor, (3) the switch from long to short-wavelength stall inception resulting from the re-staggering of the inlet guide vane, (4) the occurrence of rotating stall inception on the negatively sloped portion of the compressor characteristic. Parametric investigations indicated that: (1) short-wavelength disturbances were supported by the rotor blade row, (2) the disturbance strength was attenuated within the stators, and (3) the reduction of inter-blade row gaps can suppress the growth of short-wavelength disturbances. It is argued that each local component group (rotor plus neighboring stators) has its own instability point (i.e., conditions at which disturbances are sustained) for short-wavelength disturbances, with the instability point for the compressor set by the most unstable component group.

Compressor capacity modulation

Abstract: A pulsed modulated capacity modulation system for refrigeration, air conditioning or other types of compressors is disclosed in which suitable valving is provided which operates to cyclically block flow of suction gas to a compressor. A control system is provided which is adapted to control both the frequency of cycling as well as the relative duration of the on and off time periods of each cycle in accordance with sensed system operating conditions so as to maximize the efficiency of the system. Preferably the cycle time will be substantially less than the time constant of the load and will enable substantially continuously variable capacity modulation from substantially zero capacity to the full capacity of the compressor. Additional controls may be incorporated to modify one or more of the motor operating parameters to improve the efficiency of the motor during periods of reduced load.

Dynamic control system and method for catalytic combustion process and gas turbine engine utilizing same

Abstract: A unique and useful dynamic control system for the control of a catalytic combustion system for use on a dynamic plant, preferably, a gas turbine engine (14). The dynamic control system facilitates the replacement of conventional flame combustion systems with catalytic combustion systems. A method of controlling the catalytic combustion process comprises the steps of calculating a mass flow of air introduced into the combustor, monitoring a flow of fuel to be combusted within the combustor (32), monitoring a temperature of the air introduced into the combustor (32), calculating an inlet temperature set point based on the mass flow and fuel flow, and controlling a pre-burner (54) to heat the air based on the inlet temperature set point, the mass flow, and the temperature of the air. Further, the mass flow may be estimated based on ambient air temperature and pressure, and compressor (20) speed. A catalytic combustion gas turbine system is also presented, the operation of which is controlled by a dynamic plant controller (34) which generates a fuel flow rate demand signal to control the flow of fuel to be combusted in response to dynamic plant demands.

Novel high speed induction motor for a commercial centrifugal compressor

Abstract: This paper describes the electrical, mechanical and metallurgical design, construction and testing of a novel, low-cost, high-speed, high-efficiency induction motor to drive a new type of small centrifugal compressor in industrial cooling applications. The 28 shaft HP, 50 krpm motor features a unique laminated rotor with a multi-function, high-strength copper alloy cage brazed with a novel process. Relatively thin, high-silicon steel laminations were used to achieve low losses and high mechanical strength at low cost. Different heat-treatments for the stator and rotor laminations were used to optimize the mechanical and magnetic properties. The pre-prototype motors achieved about 94% (electromagnetic) efficiency at the rated point, including inverter harmonics, while meeting cost (less than one tenth of aerospace practice) and produceability goals.

Modeling and control of compressor flow instabilities

Abstract: Compressors are widely used for the pressurization of fluids. Applications involve air compression for use in aircraft engines and pressurization and transportation of gas in the process and chemical industries. The article focuses on two commonly used types of continuous flow compressors: the axial compressor, where the gaseous fluid is processed in a direction parallel to the rotational axis, and the radial or centrifugal compressor, where the pressurized fluid leaves the compressor in a direction perpendicular to the rotational axis. In these machines, the entering fluid is pressurized by first accelerating it via the kinetic energy imparted in the rotors and then converting the kinetic energy into potential energy by decelerating the fluid in diverging channels. Toward low mass flows, stable operation of axial and radial compressors is constrained by two aerodynamic flow instabilities: rotating stall and surge. The article gives an overview of the current state of modeling and control of these instabilities.

Exhaust gas re-circulation arrangement

Abstract: In an exhaust gas re-circulation arrangement for a supercharged internal combustion engine including an exhaust gas turbocharger with an exhaust gas turbine and a compressor, first and second exhaust pipes extending from the engine separately to the exhaust gas turbine, a charge air duct extending from the compressor to the engine and an exhaust gas recirculation line extending from one of the exhaust pipes upstream of the exhaust gas turbine to the charge air duct downstream of the compressor, the exhaust gas turbine has two turbine inlet flow passages, which provide for different flow volumes and to each of which one of the exhaust pipes is connected and a control arrangement is provided for controlling the exhaust gas flow through the turbine inlet flow passages so as to control the pressure in the exhaust gas re-circulation line to be higher than in the charge air intake duct.

Quasi-isothermal Brayton Cycle engine

Abstract: An engine is disclosed. According to one embodiment of the present invention, the engine comprises a compressor, and combustor, and an expander. The compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The expander receives the exhaust gases from the combustor, and expands the exhaust gases. The compressor may be a gerotor compressor or a piston compressor having variable-dead-volume control. The expander may be a gerotor expander or a piston expander having variable-dead-volume control. In another embodiment, an engine comprises a piston compressor, a combustor, a piston expander, and a pressure tank. The piston compressor compresses ambient air. The combustor burns the compressed air, and produces exhaust gases. The piston expander receives the exhaust gases from the combustor, and expands the exhaust gases. The pressure tank receives and stores the compressed air from the compressor. In another embodiment, a gerotor compressor or a gerotor expander comprises an inner gerotor, and an outer gerotor. The inner gerotor and the outer gerotor are driven so that they do not touch. The gerotors may be cantilevered or non-cantilevered.

Integrated bleed air and engine starting system

Abstract: An integrated bleed air and engine starting system for an engine utilizes an innovative flow multiplier air turbine starter to provide bleed air supply to an ECS as well as starting an engine The technique reduces bleed air consumption by mixing fan stage air and high stage air for ECS fresh air usage It also can eliminate or reduce the size of the precooler heat exchanger The system includes an air turbine starter subsystem and an air flow subsystem The air turbine starter subsystem includes a compressor, a turbine, and a common shaft fixed between the compressor and turbine Also provided is a gear coupled to a gearbox which links the engine with a shaft, as well as a variable nozzle valve intermediate the turbine and engine The air flow subsystem comprises a diverter valve downstream of the turbine, an isolation valve intermediate the turbine and an auxiliary power unit, and a check valve downstream of the compressor and turbine A fan is in air flow communication with the compressor and engine

Oil level control system

Abstract: This oil level control device is for a refrigeration system, the control device being attached between the compressor and the oil supply. The control device includes a housing having an inlet communicating with the oil supply and an outlet communicating with a compressor sump; and a solenoid valve controlling flow from the oil supply into the compressor sump. A sensing chamber having a fixed probe providing a proximity detection system detects the oil level in the sump and responds to a change in the complex permittivity of the oil as the oil level rises and falls to generate a signal that controls the supply of oil to maintain the oil level in the compressor. Circuitry is provided having an input connected to the output of the sensor and an output connected to the solenoid valve.

An overview of rotating stall and surge control for axial flow compressors

Abstract: Modeling and control for axial flow compression systems have received great attention in recent years. The objectives are to suppress rotating stall and surge, to extend the stable operating range of the compressor system, and to enlarge domains of attraction of stable equilibria using feedback control methods. The success of this research field will significantly improve compressor performance and thus future aeroengine performance. This paper surveys the research literature and summarizes the major developments in this active research field, focusing on the modeling and control perspectives to rotating stall and surge for axial flow compressors.

Gas turbine power plant

Abstract: A gas turbine power plant has no intercooler for compressed air and comprises a compressor, a combustor for burning fuel with compressed air from the compressor to produce combustion gas, a turbine driven by the combustion gas, a generator driven by the turbine to generate electric power, a regenerative heat exchanger which heats the compressed air with the heat of exhaust gas of the turbine and has a water spray arranged therein for spraying water droplets onto the compressed air therein, and a spray device directly communicating with the compressor for spraying water onto compressed air of high temperature from the compressor to humidify the compressed air, the compressed air being led to the regenerative heat exchanger.

Air conditioner for vehicle

Abstract: PROBLEM TO BE SOLVED: To improve the assembling workability of an air conditioner to a vehicle by connecting the outlet of a receiver dryer and the inlet of a compressor to the inlet of an expansion valve and the outlet of an evaporator, respectively. SOLUTION: A sub-assembly is composed by assembling a compressor 15, capacitor 17, receiver dryer 18, discharge hose 22 and receiver outlet hose 24 to an engine 10. An expansion valve 19 and an evaporator 20 are attached to a dash panel 8 in a car body side, and the inlet 19a of the expansion valve 19 and the outlet 20a of the evaporator 20 are protruded in an engine room 9. A suction hose 25 is connected to the outlet 20a of the evaporator 20, and fixed to a strut tower 14 via a clamp 38. When the engine 10 as the sub-assembly is mounted in an engine room 9, the receiver exit hose 24 and the entrance of the compressor 15 in the engine side are respectively connected to the inlet 19a of the expansion valve 19a and the suction hose 25 in a car body side. Work in the engine room 9 is facilitated, and assembling workability is improved.

Combustion air control system for a gas turbine engine

Abstract: Systems for controlling the combustion air to be used with a gas turbine engine for control of the products of combustion and reducing emissions emitted therefrom have been used in the past. The present system (44) includes a compressed air plenum (198, 198') being divided into a combustion air supply portion (250, 250') and a dilution or cooling air supply portion (252, 252'). A variable geometry system (76) is positioned between the compressor section (18) and the compressed air plenum (198, 198'). The variable geometry system (76) is movable between an open position (268, 268') and a closed position (270, 270'). Movement of the variable geometry system (76) varies the distribution of the compressed air (22) between the combustion air supply portion (250, 250') and the dilution or cooling air supply portion (252, 252'). The system (44) reduces emissions emitted from the gas turbine engine (10).

Method of operating a power plant with recycled CO2

Abstract: In a method of operating a power station plant with a closed or virtually closed CO2 process, a fuel quantity (21) and oxygen (18) required in this regard for the oxidation are introduced into the cycle for the internal combustion. A recuperator (8) acts on the downstream side of a turbine (2) belonging to the power station plant, at least one heat sink (24) operating downstream of this recuperator before the cycle medium (6) flows back into a compressor (1) which likewise belongs to the power station plant. A partial quantity of the compressed cycle medium (10) is directed into a condensing plant, the liquid CO2 formed here being disposed of in the best possible way.

Cooled Cooling Air Systems for Turbine Thermal Management

Abstract: This paper evaluates the feasibility and potential impact on overall engine performance when utilizing the heat sink sources available in a gas turbine engine for improved turbine thermal management. A study was conducted to assess the application of a heat exchanger to cool the compressor bleed air normally used air for cooling turbine machinery. The design tradeoffs of this cooled cooling air approach as we’ll as the methodology used to make the performance assessment will be addressed.The results of this study show that the use of a cooled cooling air (CCA) system can make a positive impact on overall engine performance. Minimizing the complexity and weight of the CCA system, while utilizing advanced, high temperature materials currently under development provide the best overall solution in terms of design risk and engine performance.Copyright © 1999 by ASME

Hybrid compressor and control method

Abstract: A hybrid compressor selectively driven by an engine (3) and an electric motor (4) The hybrid compressor includes a variable displacement compression mechanism (1) When the compression mechanism (1) is driven by the motor (4), the cooling capacity of a refrigeration circuit that includes the hybrid compressor is adjusted by controlling the inclination of the swash plate (19) and the motor speed In the control procedure, the inclination angle of the swash plate (19) and the motor speed are controlled so that the compression mechanism (1) and the motor (4) are most efficiently operated to achieve the required cooling capacity Therefore, the hybrid compressor is constantly operated with maximum efficiency

Development of Advanced Compressor Airfoils for Heavy-Duty Gas Turbines: Part I — Design and Optimization

Abstract: A new family of subsonic compressor airfoils, which are characterized by low losses and wide operating ranges, has been designed for use in heavy-duty gas turbines. In particular the influence of the higher airfoil Reynolds numbers compared to aeroengine compressors and the impact of these differences on the location of transition are taken into account. The design process itself is carried out by the combination of a geometric code for the airfoil description, with a blade-to-blade solver and a numerical optimization algorithm. The optimization process includes the design-point losses for a specified Q3D flow problem and the off-design performance for the entire operating range. The family covers a wide range of inlet flow angle, Mach number, flow turning, blade thickness, solidity and AVDR in order to consider the entire range of flow conditions that occur in practical compressor design. The superior performance of the new airfoil family is demonstrated by a comparison with conventional controlled diffusion airfoils (CDA). The advantage in performance has been confirmed by detailed experimental investigations, which will be presented in Part II of the paper. This leads to the conclusion that CDA airfoils that have been primarily developed for aeroengine applications are not the optimum solution, if directly transferred to heavy-duty gas turbines. A significant improvement in compressor efficiency is possible, if the new profiles are used instead of conventional airfoils. @S0889-504X~00!02102-4#

Oil-free liquid chiller

Abstract: A refrigeration chiller employs a centrifugal compressor the impellers of which are mounted on a shaft which is itself mounted for rotation using rolling element bearings lubricated only by the refrigerant which constitutes the working fluid of the chiller system. Apparatus is taught for providing liquid refrigerant to (1.) the bearings immediately upon chiller start-up, during chiller operation and during a coastdown period subsequent to shutdown of the chiller and (2.) the drive motor of the chiller's compressor for motor cooling purposes. By use of a variable speed-driven motor to drive the compressor, optimized part load chiller performance is achieved in a chiller which does not require or employ an oil-based lubrication system.

Multistage supercharging system for a reciprocating engine

Abstract: A multistage supercharging system for a reciprocating engine, which is suitable for use in an aircraft capable of flying at high altitude, includes plural stage turbochargers connected in series to each other. A control unit controls operation of these turbochargers. The turbocharger at each stage includes a turbine side bypass passage bypassing the turbine, a compressor side bypass passage bypassing the compressor, a wastegate valve for controlling the flow rate of exhaust flowing through the turbine side bypass passage, a bleed valve for controlling the flow rate of intake air flowing through the compressor side bypass passage, and a pressure sensor disposed at the downstream side of the compressor. The control unit receives a signal from the pressure sensor, and controls the respective valves to selectively operate the turbochargers.

Environment control unit for turbine engine

Abstract: An environmental control unit to supply cool dry air to an aircraft cabin has a plurality of bleed air sources from an aircraft engine compressor supplying working fluid to an air cycle cooling circuit An electronic control computer having a plurality of inputs and selects a bleed air source depending upon cabin cooling and pressurization requirements A speed control valve responsive to an output from the control computer, modulates the flow of working fluid through a turbo-alternator, thereby synchronizing the frequency of electrical power produced by the turbo-alternator with that of an aircraft engine alternator The turbo-alternator supplies additional electrical power to the aircraft, thereby minimizing the deleterious effect of warm air bled from the engine compressor on aircraft performance