WO1992003661A1 - Procede et moyens de regulation d'ecoulement - Google Patents

Procede et moyens de regulation d'ecoulement Download PDF

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Publication number
WO1992003661A1
WO1992003661A1 PCT/GB1991/001407 GB9101407W WO9203661A1 WO 1992003661 A1 WO1992003661 A1 WO 1992003661A1 GB 9101407 W GB9101407 W GB 9101407W WO 9203661 A1 WO9203661 A1 WO 9203661A1
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WO
WIPO (PCT)
Prior art keywords
flow
station
compressor
injection
variations
Prior art date
Application number
PCT/GB1991/001407
Other languages
English (en)
Inventor
Christopher Freeman
Ivor John Day
Original Assignee
Rolls Royce Plc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rolls Royce Plc filed Critical Rolls Royce Plc
Priority to EP91915299A priority Critical patent/EP0543908B1/fr
Priority to US07/960,367 priority patent/US5340271A/en
Priority to DE69122258T priority patent/DE69122258T2/de
Publication of WO1992003661A1 publication Critical patent/WO1992003661A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/02—Surge control
    • F04D27/0207—Surge control by bleeding, bypassing or recycling fluids
    • F04D27/0215—Arrangements therefor, e.g. bleed or by-pass valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/001—Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/02—Surge control
    • F04D27/0207—Surge control by bleeding, bypassing or recycling fluids
    • F04D27/0238—Details or means for fluid reinjection

Definitions

  • This invention relates to a method of and means for the control of flow disturbances in turbo- compressors, including both instabilities such as the phenomena of rotating stall and surge, in particular axial turbo-compressors, and steady state or quasi steady state disturbances.
  • Rotating stall is an aerodynamic instability which determines the maximum pressure rise capabilities of a turbo-compressor. At that maximum any further demand will lead to the formation of a small patch (usually referred to as a "cell" ) of disturbed flow in the blading which can then spread rapidly to engulf a large proportion of the annular cross-section of the compressor. As the stall cell forms fully, the delivery pressure at the exit from the compressor falls off just as rapidly. This type of disturbance is called rotating stall because the disturbed or "blocked" sector of the annulus will rotate with the blading, at roughly half (typically between 0.8 and 0.3) the speed of the blading.
  • the system-related instability of surge occurs when a compressor is coupled to a large downstream volume, eg. pipework in an industrial plant or the combustion chamber in a gas turbine. If the pressure rise capability of the compressor is exceeded and a stall condition is initiated there is a fall in delivery pressure which allows compressed gas in the volume downstream of the compressor to blow back through the compressor. In extreme cases this can lead to flames spewing out of the front of an engine. Venting the downstream volume in this way lowers the back pressure on the compressor; the stall condition disappears and the pressure downstream is able to rise again as the downstream volume is refilled. The stalling, venting, refilling cycle will thus start again and a continuous sequence of surge cycles can ensue if the operating conditions remain unchanged.
  • a large downstream volume eg. pipework in an industrial plant or the combustion chamber in a gas turbine.
  • a stall control system for an axial flow compressor in which signals from a number of pressure transducers within the compressor are compared with a reference signal, the value of which is related to the operating conditions in the compressor.
  • the signals from the individual transducers are compared sequentially with the reference signal so that corrective action can be initiated when an abnormal value is sensed by any one sensor.
  • the signals are also summed, and the strength of the corrective action is determined by the summed signal value.
  • the form of corrective action described in US 4196472 takes the form of a controllable bleed from the compressor gas passage, and control of the stagger angle of the stator blades is also suggested.
  • a novel manner of controlling disturbances such as rotating stall and surge in turbo-compressors is now proposed in which variations in the flow are sensed at a series of circumferentially spaced positions at a chosen station in the direction of f ⁇ ow through the compressor to detect variations above a predetermined variation limit.
  • the compressor upon such a variation being detected, within " the compressor there is injected into a first axial station, spaced from the compressor exit a flow of higher-pressure gas from a second axial station of the compressor downstream of the first region, said injection being directed generally in said direction of flow and in a circumferentially selective manner dependent upon the different circumferential origins of said variations, to act against the flow disturbances indicated by said variation.
  • the sensing of said variations at a series of said positions in circumferential sequence actuates the injection into the compressor, at a region spaced from the compressor exit, of a flow of gas at a higher pressure than that prevailing at the region of injection to act against a flow disturbance indicated by said variations.
  • a significant feature of the present invention the use of injected gas to counter a flow disturbance, has the advantage over the method proposed by US 4196472 that the injection of gas improves the basic surge margin of the compressor.
  • the compressor is therefore capable of operating at a higher output than would be the case with a prior art bleed system.
  • Rotating stall conditions may also be experienced in turbo-compressors at low speed, part load conditions. In this case, the instability is found to occur at the front of the compressor. Because the machine is then working at a lower compression ratio than the optimum for which it is designed the early stages are relatively highly loaded compared with the rearmost stages. The flow at the front of the compressor can then reach stalling point, giving an uncontrolled loss of power.
  • the present invention can also be employed to counter this problem by the injection of higher pressure gas into the foremost stages of a turbo-compressor, preferably at the front stage, in a similar manner to that described for high speed operation.
  • any axial region of the compressor may be chosen for the flow injection, depending upon the nature of the disturbance to be countered. It is necessary to ensure that the injection pressure is sufficient to obtain an adequate energy input at a location where it will influence the flow disturbance sensed, but for greatest efficiency the pressure differential should be kept as low as is practical. If a flow is to be injected at the front of the compressor, it may not be desirable therefore to take the injected air from the compressor outlet. From the point of view of aerodynamic efficiency, it would be desirable to have a multiplicity of successive flow injection circuits along the compressor flow path, each spanning only a small part of that path, but the mechanical complexity of such an arrangement will normally be impractical.
  • both high and low speeds stalling can be countered with relatively simple means if there are tappings at the front, rear and intermediate regions of the compressor, so enabling an injection from the rear or outlet to the intermediate region to counter high speed stall in response to detection means at the intermediate region, and from the intermediate region to the front or entry region to counter low speed stall in response to detection means at the entry region.
  • the critical axial station or stations at which a flow disturbance will be initiated can be expected to vary with different designs of turbo-compressor and the locations of the injection and sensing means may therefore be selected empirically. There may also be a need to monitor the compressor flow near its outlet end for incipient surge conditions, independently of monitoring for rotating stall further upstream.
  • gas injection means in response to the sensing of a rotating flow variation gas may be injected sequentially through a circumferentially spaced series of ports at a station.
  • gas may be injected simultaneously through said series of ports.
  • gas injection means at a number of axially spaced stations they can be actuated in response to sensed variations at their respective stations or at other stations as appropriate.
  • the control system is deployed at a number of axidl stations, it may be operated independently at each station or the gas injection at the different stations can be coordinated, eg. to operate in unison or in a predetermined sequence.
  • the method of the present invention can also be employed to counter flow distortions where the flow distribution is non-uniform in the circumferential sense. This condition can occur in aero-engines during transient manoeuvres or when the aircraft is travelling at low speed with the engine axis at a larger angle than usual to the flight path, such as can occur at take-off. A part of the engine air intake area is then effectively "shadowed" by the cowling upstream of it and there can be break away of the flow in the first stage of the compressor.
  • apparatus having means for sensing variations in the flow at a series of circumferentially spaced positions at a chosen station in the direction of flow through a turbo- compressor also comprises means for tapping higher pressure gas from the compressor downstream of said station and for reinjecting said higher pressure gas into the compressor at or adjacent said station, generally in said direction of flow, and control means for permitting said injection to take place, the sensing means actuating said control means in a circumferentially selective manner dependent upon the circumferential origins of the variations sensed, thereby to act against the flow disturbances indicated by said variations.
  • apparatus for controlling gas flow in a turbo-compressor comprises flow sensing means for a series of circumferentially spaced positions at a chosen axial station in the direction of flow through the compressor, means for detecting from signals from the sensing means at said the individual positions flow variations above a predetermined variation limit, means for injecting a flow of gas at a higher pressure than that prevailing at said station and generally in the direction of flow, means for actuating said injection means in response to the sensing 13 compressor to supply high-pressure air for injection through the inlets.
  • the valves 14 are normally shut but can be opened by a control circuit 22 in dependence upon the signals from the sensors 2. As will be described in more detail below, detection of a disturbance by some or all of the sensors greater than the anticipated level of noise in the steady flow at the compressor inlet triggers the opening of the valves 14 to inject onto the first ring of rotor blades 6 the high pressure flow bled from the outlet end of the compressor.
  • Fig. 5 the outputs from a series of four equispaced hot-wire sensors are shown, with a stall cell appearing first in the trace of sensor II. As the stall cell circulates past sensors III and IV, the control circuit 22 is able to confirm that the disturbance is not an instrument fault and the output from the control circuit is turned on to open the valves 14. Fig. 5 demonstrates how the injection of high pressure air immediately suppresses the stall cell.
  • Fig. 6 illustrates the same set-up in which, conversely, overriding the control unit and switching the valve 14 closed allows the stall cell to reappear and a fully developed rotating stall condition quickly establishes itself.
  • the control unit 22 should close the valves once the stall cell has been suppressed.
  • the use of a timer to switch the valves off is illustrated in an experiment that produced the traces shown in Fig. 7.
  • the steady flow is close enough to a critical condition for a stall cell to appear after a short time with the valves closed, but on each occasion when the control system is operative, the disturbance is quickly removed.
  • the trace S in Fig. 7 the control system was switched off after demonstrating its efficiency, whereupon the next re- emergence of the stall cell led to a rotating stall 14 condition.
  • Figs. 8 and 9 show a similar experiment to that in Fig. 7, here using piezo-electric sensors, which are able to actuate the opening of the individual injection valves each operatively linked with a circumferentially adjacent sensor to inject high pressure air through the inlets 8.
  • Fig. 8 demonstrates how the disturbance is suppressed each time that an incipient stall cell is detected.
  • Fig. 9 shows the opening and closing sequence of the control valves which control the counteracting flow injection. As shown by some of the incidents in traces II and IV, it is possible to arrange for the control unit to respond to a persistent disturbance so fast that in effect the period of valve opening is extended.
  • FIG. 10 there is an illustration of the sensor traces recorded during a typical surge cycle in which the compressor of Fig. 4 delivers its output to a tank to produce a progressive pressure increase at the compressor outlet.
  • Fig. 11 the same surge cycle is shown, to a compressed time scale, in which the control system was switched on for a period in the middle of the cycle.
  • the surge cycle was suppressed by the operation of the injection valves and reappeared when the control system was switched off.
  • the trace shows an output from a single hot-wire sensor ahead of the first rotor stage.
  • Fig. 12 illustrates a typical pressure rise characteristic of an axial flow compressor. Without the use of the present invention, instability and a drastic drop in performance would be met at the point on the 7 of said variations at a series of said positions in circumferential sequence thereby to act against a flow disturbance indicated by said variations.
  • the or each valve controlling the flow is automatically re-shut after an interval, which may be a preset period, since a continuous injection of high-pressure gas would be uneconomic. It may be preferred to do this by tapering off the initial flow whereby the flow control effect is removed gradually.
  • the responses of the components of the system ensure in that case that the injection flow is not interrupted between the two periods. It is significant that the invention can be utilised, whether the control flow is tapered off or is simply cut off, without the control means using a feedback loop. It is possible to initiate corrective action at a maximum rate when gas injection begins, subject only to the threshold disturbance level having been exceeded. If thereafter the injection flow is cut off or its rate of injection is tapered off, it can be assured that full 8 corrective action is restored at any stage if the disturbance continues or restarts.
  • the arrangement permits considerable simplification, as compared with prior art arrangements, without impairing the ability to control disturbances. It is also possible very simply to provide manual actuating means which allows the operator to put the arrangement into operation.
  • each sensor signal is averaged with a plurality of immediately preceding sensor signals.
  • a mean value is obtained and a difference signal is then formed between the instantaneous and mean signals. If a measure of the relative magnitude of the difference signal is taken, the detection of signal relative magnitudes above a predetermined level can be arranged to produce an operative output.
  • the generation of a series of operative outputs from a plurality of the sensors can then be employed to actuate the injection means in a sequential pattern.
  • the sampling period at a given rotational speed, determines the maximum rate of response of the system. It may be desired and it can be made possible to have a sampling period occupying less than one revolution of the compressor.
  • a rolling period of revolution can be used for averaging the mean value from three successive sensors; comparing the instantaneous signal from one of these sensors with the mean value determines whether an operative output is generated.
  • the flows through the injection locations are controlled by respective valves for individual ports or groups of ports.
  • groups of ports By grouping the ports the apparatus is simplified but the amount of injection air needed is increased. It may be preferred to provide multiple orifice ports spread over a sector of the circumference at each gas injection location to improve the distribution of the injected flow.
  • the outlets should direct their flows towards the high-pressure end of the compressor.
  • the outlet For an axial flow compressor the outlet should be directed at an angle in the radial plane not substantially more than 30° from 10 the compressor casing in that plane, which will be less than 30° to the main flow streamlines.
  • the flow may be directed circumferentially in an oblique direction that opposes the direction of rotation of the compressor. It may also be found useful for an operative signal at one station to actuate an injection flow of another station, for example, if a flow disturbance is more easily detected at a station downstream from its initiation, as for example the appearance of rotating stall nearer the compressor outlet at higher speeds.
  • the sensing means should not be disposed so close to the gas injection sites that their signals are disturbed by the inflowing gas.
  • Figs. 1 to 3 are plots of a series of simultaneous air flow measurements from circumferentially spaced sensors at the entry end of an axial flow air compressor
  • Fig. 4 is a schematic illustration of the air compressor provided with flow control means according to the invention.
  • Figs. 5 to 11 are further plots of air flow measurements in the compressor illustrating the operation of the flow control means
  • Fig. 12 is a graph of the compressor characteristic indicating the improvement of performance obtainable by the use of the control means
  • Fig. 13 is a schematic illustration of an axial flow jet engine provided with control means according to the invention.
  • Figs. 14 and 15 are detail views that illustrates schematically the air injection means at a portion of the circumference of a compressor casing
  • Fig. 15a is a detail view of a modified arrangement of injection ports, 11
  • Fig. 16 is a sectional view of one form of control valve for the injection flow
  • Figs. 17 and 18 are block diagrams illustrating details of the control arrangement in Fig. 13, and Fig. 19 is a schematic illustration of a further example of an axial flow jet engine provided with control means according to the invention.
  • a stall cell in an axial flow compressor can grow from an undetectable disturbance to a fully developed blockage in a matter of milliseconds; this development will usually take place over about 4 to 6 revolutions of the compressor rotor.
  • the stall cell may make its first appearance at any point around the flow passage through the compressor, so that a series of spaced sensors are needed to detect the origin and development of a stall cell.
  • Experiments testing the basis of the p. .sent invention were made using a turbo- compressor with a series of hot-wire sensors spaced circumferentially around an axial position im * lately ahead of the first rotor disc as shown in Fig.
  • FIG. 2 illustrates to the same time scale as Fig. 1 the 12 initiation of a surge cycle, the first sign of which is the v-shaped stall cell emerging first in trace IV.
  • the subsequent development after a couple of revolutions is notably different from the development of rotating stall, and the outputs from all the sensors show a concurrent and relatively long-lived drop of flow rate.
  • Fig. 2 and Fig. 3 shows, over a longer time scale, the complete "stall-backflow-refill" sequence. Steady flow, dropping slightly as the back pressure builds up, finally breaks down and the flow reverses, steady flow being resumed again at a higher rate because of the reduced back pressure.
  • Fig. 4 illustrates in outline the axial flow compressor C equipped with flow control means in accordance with the invention.
  • the hot wire sensors 2 can be seen immediately between a ring of fixed guide vanes 4 and a ring 6 of rotor blades.
  • a circumferentially distributed series of air inlets 8 blend tangentially with the inner wall 10 of the compressor casing.
  • the inlets are directed rearwards into the adjacent rotor blade ring.
  • the inlets are set at an angle in the circumferential sense that may be determined empirically but that preferably directs them counter to the direction of rotation of the rotor.
  • Fig. 13 illustrates schematically the application of control apparatus according to the invention to a gas turbine which comprises an axial flow compressor A, combustion chamber C and turbine T, the compressor and turbine being coupled by a shaft S to rotate together.
  • Flow sensors are located at two axial stations, namely the sensors 102a in front of the first stage of blades disc 106a and the sensors 102b behind a stage 106b near the high pressure outlet. At each station there is a series of three or more of the sensors 102 circumferentially equally spaced around the casing.
  • a first series of injection ports 108a are distributed around the compressor casing upstream of the front stage 106a but circumferentially offset from the sensors 102a.
  • a similar series of bleed ports 110a around the circumference of an intermediate stage of the compressor allow gas flow through conduits 116 to the lower pressure regime at the injection ports 108a when normally closed valves 114a are opened.
  • a further series of circumferentially distributed injection ports 108b adjacent the bleed ports 110a can receive higher pressure gas from similarly distributed bleed ports 110b through conduits 118 and further normally closed valves 114b.
  • this arrangement of ports and valves is illustrated at diametrically opposite sides, but as is described below, the circumference of the compressor is divided into a number of equal sectors, eg. 6 to 12, each of which has its own pair of valves 114a, 114b and associated conduits 116,118 controlling the flow through a series of injection and bleed ports distributed over the sector.
  • Fig. 13 provides two separate recirculation systems which can be operated independently of each other.
  • the intermediate to front stage recirculation through the valves 114a intended to counter low power instabilities, is regulated by a control circuit 202a in response to the signals from the sensors 102a at the front of the compressor.
  • Recirculation from the rear to intermediate stages through the valves 114b is regulated by control circuit 202b in accordance with the signals from sensors 102b near the rear of the compressor. Further details of the control circuit 202 will be described with reference to Figs. 17 and 18.
  • Figs. 14 and 15 illustrate in more detail the air injection arrangement at a typical port 108.
  • the port is located in a ring of guide vanes 122 mounted on the casing inner wall 124 of an axial compressor.
  • Each port comprises a group of three nozzles 126 opening into the compressor gas flow passage from a plenum 128.
  • the nozzles are inclined at 30° to the axial direction to direct injected air I obliquely into the main flow F at as shallow a radial angle as possible.
  • the division of the flow through a number of nozzles helps to keep the radial angle of injection small.
  • a lip 130 shrouds the leading portion of the outlet of each nozzle.
  • the nozzles 126 may also be inclined circumferentially so that the flow through them is injected with some whirl component in a direction counter to the whirl component of the main flow through the guide vanes.
  • Fig. 15a illustrates an alternative location of the ports 126, in the axial gap between the trailing edges of the stator guide vanes 122 and the leading edges of the rotor blades 123.
  • An advantage of the arrangement shown in Fig. 15a is that the circumferential angle of injection can be more freely varied because it is not limited by the proximity of the stator guide vanes. The angle may be varied quite widely but it preferably lies between the axial direction and an angle to that direction substantially equal to the stagger angle of the rotor blades of the adjacent ring.
  • the ports 108 are disposed between each successive pair of guide vanes 122 and they are connected in groups to a series of six plenums 128 so that each plenum supplies injection air to a 60° sector of the compressor circumference.
  • Each 60° sector has its own control valve 114 and is connected to the extraction porting 110 of a corresponding 60° sector at the downstream station.
  • For each 60° sector there may be a single flow sensor 102, or a plurality of circumferentially spaced sensors, preferably at substantially the same axial station as the injection ports.
  • the sensors 102 are preferably static pressure sensors mounted flush in the casing wall, as indicated in Fig. 14.
  • FIG. 16 A preferred form of the valve 114 to obtain an appropriately fast response to the detection of a flow disturbance is shown in Fig. 16.
  • This is an oscillatory rotary valve comprising a rotor 142 mounted on a spindle 144 in a casing 146 through upper and lower bearings 148,150.
  • the rotor 142 is a hollow cylinder closely fitting but freely slidable in a cylindrical stator 152. Both rotor and stator have a series of spaced slots 154 in their cylindrical walls, and the two series of slots can be moved in and out of register by a relatively small rotary movement of the rotor. With the slots out of register flow through the valve is blocked.
  • valve rotor When the slots are in register, gas from supply conduit 156 reaching the encircling entry chamber 158 in the valve casing 146 can flow th ough the slots, past the spider 159 supporting the lower bearing 150 and through the valve outlet 160.
  • the valve rotor has a lightweight construction, eg. of a carbon composite material.
  • the stator is preferably made of the same material to ensure fit is maintained over a range of temperatures. Movement of the valve is controlled electro- magnetically by a torque motor 162 comprising an electromagnet 164 secured in the casing and an armature 166 attached to the rotor 142.
  • the motor is displaceable between end positions which correspond to the valve open and closed states so that no mechanical stops are required to locate the rotor at either position.
  • a control circuit 202 dealing with an individual sensor output is shown in more detail in Figs. 17 and 18.
  • the electronic signal a from each sensor output is first filtered in a low-pass filter 210 to remove blade order disturbances and the filtered signal b is then processed in an integrator 212.
  • the integrator functions to give an average sensor value c over a rolling period equal to the sampling of at least three successive sensors 102 - for example if there is one sensor per sector the rolling period can be as little as one half revolution.
  • the average value gives a steady but continuously updated base level against which the magnitude of instantaneous variations can be measured.
  • the integrated output c is compared with the filtered instantaneous signal b in a subtraction unit 214, the difference d between the two signals being the perturbation, ie the divergence of the instantaneous signal from the rolling average.
  • a divider circuit 216 calculates the ratio of the perturbation d to the current average value c, so that a non-dimensional measure e of the deviation is obtained.
  • the output e from the divider circuit 216 is fed to at least a first discriminator 218 to be compared with a pre-set level X which must at least be matched if the air injection is to be operated.
  • the output f from the discriminator is on if the magnitude of the division is greater than or equal to X.
  • the signals b obtained .rom the individual sensors and the outputs f are used to actuate an array of AND-gates 219-219n each linked to a respective valve 114.
  • Each valve is opened when its AND-gate receives both an output f and a signal from the sensor circumferentially associated with its valve, and so produces an output which operates relay 220 of the valve.
  • Each of the valves is therefore opened in turn in coordination with the circumferential position of the flow signal sensed when that signal has generated the perturbation output f. It will be seen that the valve to be opened may be for the same segment of the compressc air passage as that in which the perturbation was sensed, or it may be for a sector that follows in the direction of rotation if it is necessary to compensate for a lag in the response.
  • a further discriminator 218 ' in the circuit of Fig. 18 may also receive the signal e and be tuned to respond with an output f' at a level X' that is greater than the value that would appear in normal engine operating conditions such as acceleration and deceleration, but is less than the level that would appear in a stall condition. This can for example be used to counter flow distortion at extreme flight altitudes, for example.
  • a store 222 has addresses 223 for the outputs from the discriminators 218 for all of the sensors, of each stage.
  • an output fj(e>X) occurs, that signal is held for at least the rolling period of the integrator 212, as determined by the input signal of compressor speed N.
  • the values held in the store are extracted in step with the scanning of the addresses 223 and are summed in an addition circuit 224 for all of the sensors in the stage.
  • Comparator 228 determines if the summed signals exceed predetermined values, whereupon a valve control circuit 22 _s actuated to open the injection valve or valves 114 to the appropriate compressor locations. Simultaneously, a timer 234 is actuated to close the valves 114 again after a set period, which may correspond to as little as one or two revolutions of the compressor.
  • Fig. 18 shows a gas turbine having an installation according to the invention with isolation valves 250 which are similar to the valves 114 but are designed for 3-way operation.
  • Each valve 250 has three alternative positions, (i) closed, in which the conduits 252,254,256 communicating with the valve are isolated from each other, (ii) a first operative position, in which conduits 252,254 are connected together and the conduit 256 remains isolated, and (iii) a second operative position in which the conduits 254,256 are connected together and the conduit 252 is isolated.
  • the valve 250 illustrated and its associated conduits of course represent only one of a series of such air circulation devices distributed at spaced intervals around the circumference of the compressor to take air from and deliver it to rings of nozzles at the chosen take-off and injection stages.
  • the control system shown in Fig. 19 includes an inlet temperature sensor 262 and a shaft speed sensor 264 which provide inputs through A-D convertors 266,268 of temperature T and rotational speed N to an operating unit 270.
  • the unit 270 operates on the inputs to produce an output N/T which represents the corrected speed, a parameter of flow conditions in the compressor.
  • a processing unit 280 operates in the manner already described with reference to the units 202, in accordance with signals from static pressure sensors 282,284 indicating a flow disturbance actuating the opening of the valves 250 to produce a fixed period of air injection.
  • the value of the N/T value is input to the processor 280 to determine whether the output from the unit 280 actuates the valve 250 to open the path 254,252 or the path 256,254.
  • Lower values of N/T indicate lower power operation of the compressor and the valve 250 is actuated so that air tapped from the intermediate station is injected into the front of the compressor via the conduits 252.
  • Higher values of N/T indicate that any disturbance to be acted upon requires correction in the downstream stages and the valve 250 so opens that air from the compressor exit is injected into the intermediate stage via the conduits 254.
  • the method of control according to the invention can also operate to counter a steady flow distortion, ie. some element of circumferential asymmetry in the flow which, although not necessarily leading to a catastrophic disruption of the flow, reduces the efficiency of the turbo-compressor.
  • the control systems would be arranged to act on the appropriate single injection valves or selected groups of the valves at a particular station and sector when a steady flow distortion is indicated by the signals sensed.
  • the circumferentially corresponding injection conduits at two or more stations may share the same control valve. If injection is required only to counter incipient surge conditions, a circumferential series of injection conduits may be connected to a common control valve.
  • the amount of opening may be graduated, or the injected flow volume may be reduced if the valve is opened and closed several times in quick succession.
  • an initial command opens the valve eg. up to 25%, and then if there is a further command from the logic circuitry to open the valve it is opened wider.
  • the form of response may also be matched to the type of instability being detected.
  • the distortion will circulate around the circumference of any particular stage and if the distortion is sensed in sequence by the associated sensors, it may not be necessary to inject pressure air through all the inlets associated with that stage. A sequential injection in phase with the distortion may then be sufficient. That does not apply if the distortion is sensed simultaneously by all the sensors, indicating a surge condition.
  • the speed of response of the system is dependent upon the level of discrimination, which must be sufficiently low to enable corrective action to be initiated before any significant loss of engine power occurs, yet must not be so sensitive as to respond to the normal and inevitable variations that occur in the operation of an axial flow compressor, such as the blade to blade differences and the wake disturbances of each blade giving a blade passing frequency variation. This latter is usually the most significant noise component in the axial flow compressor of an aero engine and would give a variation there of about 2%.
  • the limiting value for initiating corrective action ie. the value of X for the discriminators 218 (Fig. 17), would thus be set above the 2% level in such an installation.

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  • Control Of Positive-Displacement Air Blowers (AREA)

Abstract

L'invention décrit un procédé de régulation d'écoulement de gaz dans un compresseur centrifuge axial, selon lequel l'écoulement, à au moins un poste donné dans le sens d'écoulement à travers le compresseur, est détecté en une série de positions espacées de manière circonférentielle. Des fluctuations d'écoulement au-dessus d'une limite prédéterminée sont évaluées afin de produire une réaction d'actionnement si une perturbation se situant au-dessus d'un niveau acceptable prédéterminé est détectée. Lorsqu'une perturbation est détectée, un gaz à plus haute pression soutiré d'un endroit plus loin en aval est injecté dans ledit poste pour y compléter l'écoulement de gaz principal. Une cellule de décrochage tournant naissante va apparaître sous forme d'une fluctuation ayant lieu séquentiellement à des positions espacées de manière circonférentielle. Lorsqu'on réagit à une telle condition par un écoulement à injection sous pression, il devient possible de supprimer des conditions de décrochage tournant et de pompage dans le compresseur avant que la perturbation ne se développe entièrement. Les mêmes moyens peuvent être agencés pour contrecarrer la distortion en régime permanent.
PCT/GB1991/001407 1990-08-18 1991-08-19 Procede et moyens de regulation d'ecoulement WO1992003661A1 (fr)

Priority Applications (3)

Application Number Priority Date Filing Date Title
EP91915299A EP0543908B1 (fr) 1990-08-18 1991-08-19 Procede et moyens de regulation d'ecoulement
US07/960,367 US5340271A (en) 1990-08-18 1991-08-19 Flow control method and means
DE69122258T DE69122258T2 (de) 1990-08-18 1991-08-19 Verfahren und mittel zur strömungskontrolle

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9018188.4 1990-08-18
GB909018188A GB9018188D0 (en) 1990-08-18 1990-08-18 Flow control method and means

Publications (1)

Publication Number Publication Date
WO1992003661A1 true WO1992003661A1 (fr) 1992-03-05

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PCT/GB1991/001407 WO1992003661A1 (fr) 1990-08-18 1991-08-19 Procede et moyens de regulation d'ecoulement

Country Status (5)

Country Link
EP (1) EP0543908B1 (fr)
JP (1) JPH05509143A (fr)
DE (1) DE69122258T2 (fr)
GB (1) GB9018188D0 (fr)
WO (1) WO1992003661A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2804732A1 (fr) * 2000-02-03 2001-08-10 Snecma Procede de detection precoce des instabilites aerodynamiques dans un compresseur de turbomachine
GB2413158A (en) * 2004-04-13 2005-10-19 Rolls Royce Plc Part casing circumference flow control arrangement
EP1942259A2 (fr) * 2006-12-28 2008-07-09 General Electric Company Contrôle de la ligne de fonctionnement d'un système de compression avec recirculation du flux
CN104114875A (zh) * 2012-01-16 2014-10-22 慕尼黑联邦国防军大学 用于稳定压缩机流的方法和装置
EP3296573A1 (fr) * 2016-09-20 2018-03-21 Siemens Aktiengesellschaft Technique de contrôle du décrochage tournant dans un compresseur de moteur à turbine à gaz

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DE102007035927A1 (de) * 2007-07-31 2009-02-05 Mtu Aero Engines Gmbh Regelung für eine Gasturbine mit aktiv stabilisiertem Verdichter
KR20120077335A (ko) * 2010-12-30 2012-07-10 한국항공우주연구원 축류 압축기 및 그의 유체 안정화 제어 방법

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FR1136881A (fr) * 1954-10-06 1957-05-21 Power Jets Res & Dev Ltd Perfectionnements apportés aux compresseurs à plusieurs étages à aubes aérodynamiques
FR2248427A1 (fr) * 1973-10-23 1975-05-16 Howell Instruments
US4196472A (en) * 1977-09-09 1980-04-01 Calspan Corporation Stall control apparatus for axial flow compressors
GB2191606A (en) * 1986-04-28 1987-12-16 Rolls Royce Plc Active control of unsteady motion phenomena in turbomachinery

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Publication number Priority date Publication date Assignee Title
FR1136881A (fr) * 1954-10-06 1957-05-21 Power Jets Res & Dev Ltd Perfectionnements apportés aux compresseurs à plusieurs étages à aubes aérodynamiques
FR2248427A1 (fr) * 1973-10-23 1975-05-16 Howell Instruments
US4196472A (en) * 1977-09-09 1980-04-01 Calspan Corporation Stall control apparatus for axial flow compressors
GB2191606A (en) * 1986-04-28 1987-12-16 Rolls Royce Plc Active control of unsteady motion phenomena in turbomachinery

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Title
Journal of Propulsion and Power, volume 5, no. 2, 1989, A.H. Epstein et al.: "Active suppression of aerodynamic instabilities in turbomachines", pages 204-211, see the whole article (cited in the application) *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2804732A1 (fr) * 2000-02-03 2001-08-10 Snecma Procede de detection precoce des instabilites aerodynamiques dans un compresseur de turbomachine
EP1138952A1 (fr) * 2000-02-03 2001-10-04 Snecma Moteurs Procédé de détection précoce des instabilités aérodynamiques dans un compresseur de turbomachine
US6755617B2 (en) 2000-02-03 2004-06-29 Snecma Moteurs Method for the early detection of aerodynamic instabilities in a turbomachine compressor
GB2413158A (en) * 2004-04-13 2005-10-19 Rolls Royce Plc Part casing circumference flow control arrangement
GB2413158B (en) * 2004-04-13 2006-08-16 Rolls Royce Plc Flow control arrangement
US7811049B2 (en) 2004-04-13 2010-10-12 Rolls-Royce, Plc Flow control arrangement
EP1942259A2 (fr) * 2006-12-28 2008-07-09 General Electric Company Contrôle de la ligne de fonctionnement d'un système de compression avec recirculation du flux
EP1942259A3 (fr) * 2006-12-28 2014-04-30 General Electric Company Contrôle de la ligne de fonctionnement d'un système de compression avec recirculation du flux
CN104114875A (zh) * 2012-01-16 2014-10-22 慕尼黑联邦国防军大学 用于稳定压缩机流的方法和装置
EP3296573A1 (fr) * 2016-09-20 2018-03-21 Siemens Aktiengesellschaft Technique de contrôle du décrochage tournant dans un compresseur de moteur à turbine à gaz
WO2018054916A1 (fr) * 2016-09-20 2018-03-29 Siemens Aktiengesellschaft Technique de commande de décollement tournant dans un compresseur de moteur à turbine à gaz
US11149751B2 (en) 2016-09-20 2021-10-19 Siemens Energy Global GmbH & Co. KG Technique for controlling rotating stall in compressor for a gas turbine engine

Also Published As

Publication number Publication date
EP0543908A1 (fr) 1993-06-02
DE69122258D1 (de) 1996-10-24
EP0543908B1 (fr) 1996-09-18
JPH05509143A (ja) 1993-12-16
DE69122258T2 (de) 1997-01-30
GB9018188D0 (en) 1990-10-03

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