Showing papers on "Gas compressor published in 1997"

A Study of Spike and Modal Stall Phenomena in a Low-Speed Axial Compressor

Abstract: This paper presents a study of stall inception mechanisms a in low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short lengthscale disturbance known as a ‘spike’, and the second with a longer lengthscale 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 which 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 lengthscale disturbances are related to a two-dimensional instability of the whole compression system, while short lengthscale 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 which 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.Copyright © 1997 by ASME

Synthesis gas production system and method

Abstract: A synthesis gas production system (302) includes a gas turbine (310) having a compressor (312) with an autothermal reformer (308) between the compressor (312) and the turbine (314). The system (302) may include a separator (326) for removing a portion of the mass exiting the compressor (312) prior to its delivery to the autothermal reformer (308). Gaseous light hydrocarbons are delivered to the autothermal reformer (308) through conduit (330) and may be selectively controlled with a valve (331). Synthesis gas production system (302) may be used with a methanol process, ammonia process, a Fischer-Tropsch process (304), or other process involving synthesis gas.

Process for converting gas to liquids

Abstract: A process for converting a hydrocarbon gas (e.g. natural gas) to syngas which, in turn, is converted into a liquid hydrocarbon product wherein a substantial amount of the heat generated in the process is recovered for use in generating steam needed in the process or for conversion into mechanical energy. Further, tail gas produced by the process is used to fuel the gas turbine which, in turn, is used to power the compressor needed for compressing the air used in the process. By using tail gas to fuel the gas turbine, less of the compressed combustion-air is needed to cool the combustion gases in the turbine and, instead, can be used to provide a portion of the process-air required in the process; thereby possibly saving up to 20 to 30 percent of the horsepower otherwise needed to compress the required volume of the process-air.

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.

Process and apparatus for achieving power augmentation in gas turbines via wet compression

Abstract: A power augmentation apparatus and process for effectively adding a mass flow of water to the working fluid acquired by the compressor of an industrial gas turbine, and especially for adding a mass flow of water to a fully-humidified working fluid for reducing the work of compression performed by the compressor and achieving a net augmentation of the power produced by the turbine, said apparatus and process preferably including the use of a spray rack group assembly having at least one spray rack water pipe and at least one spray rack water nozzle which assembly is ideally positioned a distance away from the compressor inlet. Water mass flow is added preferably in increments which correspond to the spray rack water pipes and associated nozzles. Monitoring of the temperature profile of fluid-cooled rotor blades in the turbine section with an optical pyrometer to detect clogging of cooling pathways in those rotor blades from impurities in the added water, monitoring of the working fluid's temperature in proximity to the gas turbine compressor inlet to guard against the possibility of icing, a deformation measurement device, and concurrent addition of heat and humidity, preferably steam, to the working fluid as a means to extend the utility of the process and apparatus to lower ambient air temperature operation are disclosed.

Scavenger energy converter system its new applications and its control systems

Abstract: What has been invented is a series of scientific applications of the wideface energy converter device, be it in the form of a wideface solar heat receiver or a wideface fluid impeder device. The wider is the solar heat receiver, the more solar power is available for conversion. The wider is the sail of the boat, the more wind is available to push the boat. Wherefore, the wideface solar trap made up of multi-layer transparent roofs covering a heat insulated box is used to heat up a radiator tubings that contain water. The multilayer transparent roof, having spaces in between sheets, prevents solar heat from backing out hence the trap becomes hoter and hoter because the inner sheet is not in contact with the cold wind. This solar trap is now used to heat up radiator pipes of compressed air coming from a gas turbine engine and then returned back to the exhaust turbine of same engine. Applying the principle of the wind sail, the turbine blades of the compressor and the turbine blades of the exhaust turbine are made wideface as much as possible to produce maximum impedance against the expanding exhaust hot air and to produce maximum push upon the fresh air being compressed. This wideface fluid impeder is now expanded into an underwater platform from One Acre or much more and attached to floating hotels, large/small boats, and floating sea walls, to prevent oscillation by the surfs.

High frequency pressure swing adsorption

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 in a plurality of preferably an even number of adsorbent beds (2, 4, 3, 5) with each adsorbent bed communicating at its product end (12, 13, 14, 15) directly to a variable volume expansion chamber (53, 57), and at its feed end by directional valves to a feed compressor and an exhaust vacuum pump. For high frequency operation of the pressure swing adsorption cycle, a high surface area layered support is used for the adsorbent. The compressor and vacuum pump pistons may be integrated with the cycle, reciprocating at twice the cycle frequency. Alternative configurations of the layered adsorbent beds are disclosed.

On the Design Criteria for Suppression of Secondary Flows in Centrifugal and Mixed Flow Impellers

Abstract: In this paper, for the first time, a set of guidelines is presented for the systematic design of mixed flow and centrifugal compressors and pumps with suppressed secondary flows and a uniform exit flow field. the paper describes the shape of the optimum pressure distribution for the suppression of secondary flows in the impeller with reference to classical secondary flow theory. The feasibility of achieving this pressure distribution is then demonstrated by deriving guidelines for the design specifications of a three-dimensional inverse design method, in which the blades are designed subject to a specified circulation distribution or 2 pi r (V) over bar(theta). The guidelines will define the optimum choice of the blade loading or partial derivative r (V) over bar(theta)/partial derivative m and the stacking condition for the blades. These guidelines are then used in the design of three different low specific speed centrifugal pump impellers and a high specific speed industrial centrifugal compressor impeller. The flows through all the designed impellers are computed numerically by a three-dimensional viscous code and the resulting flow field is compared to that obtained in the corresponding conventional impeller. The results show consistent suppression of secondary flows in all cases. the design guidelines are validated experimentally by comparing the performance of the inverse designed centrifugal compressor impeller with the corresponding conventional impeller. The overall performance of the stage with the inverse designed impeller with suppressed secondary flows was found to be 5 percent higher than the conventional impeller at the peak efficiency point. Exit flow traverse results at the impeller exit indicate a more uniform exit flow than that measured at the exit from the conventional impeller.

Integrated air conditioning and power unit

Abstract: An integrated air conditioning and power unit is provided for use with an aircraft. The system includes an air turbine 42 having air passages connected to an engine 10 of the aircraft for receiving bleed air and/or ram air for driving the air turbine 42. A motor/generator 104 is drivingly connected to the air turbine 42. The motor/generator 104 is capable of drawing electricity from an aircraft primary power system for driving the motor or generating electricity which is delivered to the primary power system 108. An air compressor 54 is drivingly connected to the motor/generator 104 and is provided with an air passage which receives bleed air 32 and/or ram air 30 from the aircraft engine 10. A cooling system 71 is provided including a system compressor 81 drivingly connected to the motor/generator 104. A cooling system evaporator 70 and a condenser 92 are connected to the system compressor by fluid passages. The air compressor 54 includes an air outlet for providing pressurized air which is cooled by the cooling system.

Internal combustion engine with an exhaust gas recirculation system

Abstract: In an internal combustion engine with an exhaust gas recirculation system and an exhaust gas turbocharger having a turbine arranged in an exhaust gas duct and a compressor operated by the turbine and being disposed in an air supply duct for supplying charge air to the engine, an exhaust gas recirculation line extends between the exhaust gas duct upstream of the turbine and the air supply duct and downstream of the compressor. Cooling means are arranged in the exhaust gas duct and heating means are arranged in the air supply duct upstream of the compressor to permit the generation of a pressure differential between the exhaust gas duct and the air supply duct which provides for an exhaust gas recirculation flow through the exhaust gas recirculation line over a large engine operating range.

Blockage Development in a Transonic, Axial Compressor Rotor

Abstract: A detailed experimental investigation to understand and quantify the development of blockage in the flow field of a transonic, axial flow compressor rotor (NASA Rotor 37) has been undertaken. Detailed laser anemometer measurements were acquired upstream, within, and downstream of a transonic, axial compressor rotor operating at 100%, 85%, 80%, and 60% of design speed which provided inlet relative Mach numbers at the blade tip of 1.48, 1.26, 1.18, and 0.89 respectively. The impact of the shock on the blockage development, pertaining to both the shock / boundary layer interactions and the shock / tip clearance flow interactions, is discussed. The results indicate that for this rotor the blockage in the endwall region is 2–3 times that of the core flow region, and the blockage in the core flow region more than doubles when the shock strength is sufficient to separate the suction surface boundary layer.Copyright © 1997 by ASME

System for cooling blades in a gas turbine

Abstract: A gas turbine comprises: a first closed circuit in which cooling gas is supplied to a casing, allowed to pass through stationary blades, and removed to the outside of casing after cooling the stationary blades; a second closed circuit in which cooling air is supplied to the casing, allowed to pass through moving blades, and removed to the outside of casing after cooling the moving blades; a cooler for cooling the cooling gas in the first and second closed circuits; and a booster for pressurizing and circulating the cooling gas cooled by the cooler. Also, A gas turbine comprises: a first closed circuit in which cooling air cooled after being extracted from a combustor plenum is allowed to pass through stationary blades successively to cool the stationary blades, and then recovered and returned to a compressor on the upstream side of the combustor plenum; and a second closed circuit in which cooling air cooled after being extracted from the combustor plenum is allowed to pass through moving blades successively to cool the moving blades, and then recovered and returned to the compressor.

Development of Hub Corner Stall and Its Influence on the Performance of Axial Compressor Blade Rows

Abstract: A detailed investigation has been performed to study hub corner stall phenomena in compressor blade rows. Three-dimensional flows in a subsonic annular compressor stator and in a transonic compressor rotor have been analyzed numerically by solving the Reynolds-averaged Navier-Stokes equations. The numerical results and the existing experimental data are interrogated to understand the mechanism of compressor hub comer stall. Both the measurements and the numerical solutions for the stator indicate that a strong twister-like vortex is formed near the rear part of the blade suction surface. Low-momentum fluid inside the hub boundary layer is transported toward the suction side of the blade by this vortex. On the blade suction surface near the hub, this vortex forces fluid to move against the main flow direction and a limiting stream surface is formed near the hub. The formation of this vortex is the main mechanism of hub corner stall. When the aerodynamic loading is increased, the vortex initiates further upstream, which results in a larger corner stall region. For the transonic compressor rotor studied in this paper, the numerical solution indicates that a mild hub corner stall exists at 100 percent rotor speed. The hub corner stall, however, disappears at the reduced blade loading, which occurs at 60 percent rotor design speed. The present study demonstrates that hub comer stall is caused by a three-dimensional vortex system and that it does not seem to be correlated with a simple diffusion factor for the blade row.

Turbine engine with intercooler in bypass air passage

Abstract: A turbine engine (20) having bypass and core passages (30 and 40), a high pressure compressor (80) for compressing air in the core passage and an intercooler (120, 220) for cooling core air (42) in the core passage prior to discharge by the high pressure compressor. The intercooler includes a plurality of heat exchange elements (140) positioned in the bypass passage through which all or a portion of the core air is transported. Heat in the core air is transferred via the heat exchange elements to the relatively cool bypass air, thereby cooling the core air and heating the bypass air. The turbine engine may have a counterflow intercooler (120), a radial flow intercooler 220 or an intercooler of other configuration. The turbine engine may have a high pressure compressor with two sections (82 and 86), with core air transported to and from the intercooler between sections, or a single section high pressure compressor, with core air transported to and from the intercooler upstream of the high pressure compressor. The turbine engine may be of turbofan, turboshaft, turboprop or other design.

Modular pressure swing adsorption with energy recovery

Abstract: Pressure swing adsorption (PSA) separation of a feed gas mixture is performed within an apparatus having typically a single prime mover powering a feed compressor for one or multiple rotary PSA modules in parallel, each module including a rotor with a large number of angularly spaced adsorber elements, with valve surfaces between the rotor and a stator so that individual adsorber elements are opened to compartments for staged pressurization and blowdown, with thermally boosted energy recovery from staged expansion of countercurrent blowdown and light reflux gases, and a plurality of adsorber elements opened at any instant to each compartment so that each compressor and expander stage operates under substantially steady conditions of flow and pressure.

Rotary turbomachine having a transonic compressor stage

Abstract: A rotary turbomachine, and particularly a turbojet engine, has a compressor stage that is especially adapted for operation in the transonic region. The compressor stage includes a rotor (1) having a hub (2) and a plurality of compressor blades (3) extending radially therefrom, and a stator having a plurality of compressor blades extending radially between a stator hub and a housing. The hub (2) of the rotor (1), and/or the hub of the stator, and/or the housing of the stator, have a circumferential surface contour that is not continuously rotationally symmetrical. Namely, a concave contour (K) is provided in the circumferential surface of the hub near the base of each blade (3) on the pressure side (PS) thereof, while the circumferential surface on the suction side (SS) of the base of each blade has a contour that is linear, slightly convex, convex/concave, or slightly concave to a lesser degree than the concave contour (K) on the pressure side of each blade. The hub contour slopes and transitions smoothly radially outwardly from the concave contour (K) on the pressure side to the flatter or convex contour on the suction side. In this manner, fluid flow velocities on both the pressure side and the suction side of each blade are reduced, especially under transonic operating conditions, and compression shock losses can be minimized.

Experiments in active control of stall on an aeroengine gas turbine

Abstract: This paper describes work carried out between 1989 and 1994 to investigate the application of Active Stall Control to a Rolls-Royce Viper turbojet. The results demonstrate that stall control is feasible and can increase the stable operating range by up to 25 percent of pressure rise. Stall disturbances were detected using rings of high response pressure transducers positioned at different axial planes along the compressor, and processed using a PC-based data acquisition and control system. Actuation was provided by six hydraulically operated sleeve valves positioned to recirculate air over all or part of the compressor. Stall was artificially induced using combinations of in-bleed into the combustor outer casing, fuel spiking, hot gas ingestion, and inlet pressure spoiling, thus replicating many of the transient conditions commonly observed to make a compressor prone to stall. Results are compared from a number of stall control strategies including those demonstrated at low speed by Paduano et al. (1993) and Day (1993). Best results were obtained with detection of nonaxisymmetric disturbances coupled with axisymmetric control action. A control system of this type is demonstrated to be capable of extending the stable engine operating range at all speeds and with each method of inducing stall.

Optimum performance of a regenerative Brayton thermal cycle

Abstract: The optimum performance of a regenerative Brayton cycle was analyzed. The model includes external and internal irreversibilities coming from four main sources: coupling to external heat reservoirs, turbine and compressor nonisentropic processes, pressure losses in the heater and the cooler, and the regenerator. In terms of the parameters accounting for each type of irreversibility, explicit numerical results are presented for the maximum efficiency, maximum power output, efficiency at maximum power output, power output at maximum efficiency, as well as for the pressure ratios required for maximum efficiency and maximum power. This analysis could provide a general theoretical tool for the optimal design and operation of real regenerative gas turbine power plants.

Breakdown of Tip Leakage Vortices in Compressors at Flow Conditions Close to Stall

Abstract: The breakdown of tip leakage vortices at operating points close to the stability limit of transonic compressor rotors has been detected. The aerodynamic phenomenon is considered to have a major impact on stall inception. Computations have been carried out and a detailed visualization of the phenomenon is given. In addition the connection of vortex breakdown to rotating instabilities and stall is discussed. Furthermore the tip flow field of the axial rotor is compared to the results for a centrifugal and a mixed flow compressor operating at similar tip speeds.Copyright © 1997 by ASME

Closed loop air cooling system for combustion turbines

Abstract: Convective cooling of turbine hot parts using a closed loop system is disclosed. Preferably, the present invention is applied to cooling the hot parts of combustion turbine power plants, and the cooling provided permits an increase in the inlet temperature and the concomitant benefits of increased efficiency and output. In preferred embodiments, methods and apparatus are disclosed wherein air is removed from the combustion turbine compressor (22, 26) and delivered to passages internal to one or more of a combustor and turbine hot parts (100). The air cools the combustor and turbine hot parts via convection and heat is transferred through the surfaces of the combustor and turbine hot parts.

Linear compressor control circuit to control frequency based on the piston position of the linear compressor

Abstract: A linear compressor operating apparatus includes a rectifying and filtering unit for converting an alternating current into a direct current, an inverter for inverting the direct current outputted from the rectifying and filtering unit into a desired frequency alternating current for operating a linear compressor in accordance with the alternating current outputted from the inverter, a position sensor for detecting a position of a piston of the linear compressor and outputting a position signal in accordance with said detection, a current detector for detecting the current running through the linear compressor, and a controller for receiving a current signal outputted from the current detector and a position signal outputted from the position sensor and outputting a pulse width modulating signal to control the inverter. The apparatus obtains a constant value of an interval which determines the efficiency of the linear compressor, regardless of a load thereof and optimizes a phase angle between the driving current and the compressor piston.

Electrically-driven cooling/heating system utilizing circulated liquid

Abstract: A system is adapted to be vehicle mounted and powered by a D.C. source coupled with an inverter to cool individuals or temperature sensitive hardware under uncomfortable ambient conditions. The system includes a pumped liquid circulation loop which can be connected by self-sealing lines with cooling garments, temperature sensitive hardware and the like. An evaporative heat exchanger is provided in the loop as well as a liquid reservoir which is sized to limit short cycling of a compressor in a refrigeration loop associated therewith via the evaporative heat exchanger. A hot gas bypass can be associated with the compressor to allow recirculation of the superheated refrigerant gas when cooling is not required.

Development and Optimization of Screw Machines With a Simulation Model—Part II: Thermodynamic Performance Simulation and Design Optimization

Abstract: This paper presents a method for the design of twin screw compressors and expanders, which is based on a differential algorithm for defining the rotor profile and an analytical model of the fluid flow and thermodynamic processes within the machine. Part I of the paper presents a method for screw rotor profile generation which simplifies and improves design procedures. An example is given of its use in the development of a new N rotor profile, which is shown to be superior to other well-known types. Part II describes a numerical model of the thermodynamic and fluid flow processes within screw machines, which is valid for both the compressor and expander modes of operation. It includes the use of the equations of conservation of mass and energy applied to an instantaneous control volume of trapped fluid within the machine with allowance for fluid leakage, oil or other fluid injection, heat transfer, and the assumption of real fluid properties. By simultaneous solution of these equations, pressure-volume diagrams may be derived of the entire compression or expansion process within the machine. The procedure has been developed over a period of fifteen years and validated with experimental results obtained from both reciprocating and screw compressors and screw expanders, some of which are included. The rotor profile generation processor, thermofluid solver and optimizer, together with preprocessing facilities for the input data and graphical post-processing and CAD interface, have been incorporated into a design package which provided a suitable tool for analysis and optimization of twin screw machine design. An example of its use is given in the optimization of the gate tip radius of a selected compressor design.

System and method of providing clean filtered cooling air to a hot portion of a gas turbine engine

Abstract: A system and method for providing clean cooling air to a hot portion of a gas turbine engine is disclosed, where the engine includes a compressor. The system includes a turbocompressor (66) having a compressor section and a turbine section, wherein the compressor and turbine sections each have an inlet and an outlet. The system further includes a heat exchanger (64) having a first inlet and a first outlet for a first fluid flow providing cooling to the heat exchanger, the first inlet being in fluid communication with a low temperature fluid. The heat exchanger (64) also has a second inlet and a second outlet for a second air flow receiving cooling from the heat exchanger, the second inlet being in fluid communication with high temperature air from the engine compressor and the second outlet being in fluid communication with the inlet of the compressor section of the turbocompressor. The outlet of the compressor section of the turbocompressor is in fluid communication with the filter inlet and the outlet of the filter (72) is in fluid communication with the engine hot portion so that clean cooling air is supplied to the engine hot portion.

Methods and apparatuses for detecting surge in centrifugal compressors

Abstract: A surge detection system for use in a fluid system having a load driven by a centrifugal compressor (12), the compressor (12) being driven by an electric motor (20). The surge detection system comprises a means (38, 40) for sensing a differential pressure developed across the compressor (12) and a means (42) for sensing a current representing input power to the motor (20). The surge detection system further comprises a first computing means responsive to the differential pressure developed across the compressor (12) for indicating when a valid surge is occurring in the compressor (12), and a second computing means responsive to the variable speed drive current for indicating when a valid surge is occurring in the compressor (12).

Control valve in variable displacement compressor

Abstract: A control valve for a variable displacement compressor in refrigerant circuit permits the compressor displacement to be accurately controlled regardless of the thermal load on an evaporator. The refrigerant circuit includes a high pressure pipe, which extends between a discharge chamber of the compressor and a condenser. A first pressure monitoring point is located in the discharge chamber. A second pressure monitoring point is located in the high pressure pipe. A supply passage connects the second pressure monitoring point with a crank chamber of the compressor. The control valve is located in the supply passage and adjusts the opening size of the supply passage in accordance with the difference between the pressure at the first pressure monitoring point and the pressure at the second pressure monitoring point. The control valve includes a solenoid for determining the target value of the pressure difference. The control valve operates to maintain the determined target value.

Gas turbine engine with water injection

Abstract: Precompressor and pre-booster water spray injection apparatus and methods are described. In an exemplary embodiment, a gas turbine engine suitable for use in connection with water spray injection includes a low pressure compressor, a high pressure compressor, and a combustor. The engine also includes a high pressure turbine, a low pressure turbine, and a power turbine. A water injection apparatus is provided for injecting water into an inlet of the high pressure compressor. The water spray injection apparatus is in flow communication with a water supply, and during engine operation, water is delivered from such supply through the injection apparatus to the inlet of the compressor.