EP0481149B1 - Aktive Rotor-Statorspielregelung für Gasturbine - Google Patents

Aktive Rotor-Statorspielregelung für Gasturbine Download PDF

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Publication number
EP0481149B1
EP0481149B1 EP19900630181 EP90630181A EP0481149B1 EP 0481149 B1 EP0481149 B1 EP 0481149B1 EP 19900630181 EP19900630181 EP 19900630181 EP 90630181 A EP90630181 A EP 90630181A EP 0481149 B1 EP0481149 B1 EP 0481149B1
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EP
European Patent Office
Prior art keywords
rotor
turbine
engine
angular velocity
case
Prior art date
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Expired - Lifetime
Application number
EP19900630181
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English (en)
French (fr)
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EP0481149A1 (de
Inventor
Fred M. Schwarz
Ken R. Lagueux
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Raytheon Technologies Corp
Original Assignee
United Technologies Corp
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Publication date
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Priority to DE1990617685 priority Critical patent/DE69017685T2/de
Priority to EP19900630181 priority patent/EP0481149B1/de
Publication of EP0481149A1 publication Critical patent/EP0481149A1/de
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D11/00—Preventing or minimising internal leakage of working-fluid, e.g. between stages
    • F01D11/08—Preventing or minimising internal leakage of working-fluid, e.g. between stages for sealing space between rotor blade tips and stator
    • F01D11/14—Adjusting or regulating tip-clearance, i.e. distance between rotor-blade tips and stator casing
    • F01D11/20—Actively adjusting tip-clearance
    • F01D11/24—Actively adjusting tip-clearance by selectively cooling-heating stator or rotor components

Definitions

  • Present invention relates to a method for controlling cooling air to a gas turbine engine.
  • the reduction of the running clearance between the tips of the rotating turbine blades of a gas turbine engine and the surrounding annular shroud is a technical problem which has occupied gas turbine engine designers and manufacturers.
  • One successful technique for reducing this clearance has been to impinge a flow of external cooling air on the supporting turbine case for the purpose of cooling the case and thereby reducing the inner diameter of the supported shroud.
  • the shroud may be brought sufficiently close to the rotating blade tips so as to reduce the quantity of turbine working fluid which bypasses the rotating blade stages, but not so close as to result in contact between the shroud and blade tips.
  • the effect of the re-acceleration is a rapid increase in turbine rotor speed thereby restoring the centrifugal forces on the turbine blades which may expand radially a sufficient distance to result in a blade tip to shroud interference.
  • the temperature of the working fluid passing through the turbine does increase as a result of the re-acceleration, the thermal effect on the case does not result in re-expansion of the case as quickly as the increased rotor speed causes radial growth of the turbine blade tips.
  • GB-A-2 025 536 discloses a turbine rotor/shroud clearance control system in which cooling air flow to the shroud support apparatus is varied in response to both rotor speed and time elapsed above a predetermined level by the selective use and mixing of two air sources at different temperatures.
  • Four different operating modes, each having its prescribed cooling air delivery mode, are provided so that in steady state, when engine speed and cycle temperature increase, so does that of the cooling air.
  • a timer sequences the desired cooling air delivery modes in such a manner as to maintain optimum rotor-to-shroud clearances.
  • the invention provides a method for preventing rubbing or radial interference between the blade tips of the turbine rotor and the surrounding shroud during a re-acceleration subsequent to a deceleration.
  • the invention senses a drop in the rotor speed and overrides the controller for the turbine case cooling air valve, commanding it to shut for a period of time during which the transient effect of the deceleration is permitted to pass.
  • the controller is released at the expiration of the time period, allowing the valve and turbine case cooling system to resume normal operation.
  • the shutting of the valve eliminates the flow of external case cooling air, permitting the case to become warmer as a result of the flow of the heated combustion products through the turbine.
  • the temporarily warmer case increases the running clearance between the tips of the rotor blades and the case supported shroud. This additional clearance is sufficient to accommodate the potential short term radial growth of the blade tips as a result of a re-acceleration to full load operation before the turbine rotor has reached the steady state reduced power dimension.
  • Fig.1 shows a graph of the transient response of the radial clearance between the blade tips and shroud following deceleration for subsequent re-acceleration.
  • Fig. 2 is a graph of valve shut-off time as a function of the reduction in high rotor rpm and high rotor initial rpm.
  • Fig. 3 shows a schematic of a gas turbine engine with a system for delivering a modulated flow of cooling air to the exterior of the turbine case.
  • Fig. 3 shows a turbofan gas turbine engine 10 having a fan case 12 and a turbine case 9 which is cooled by the impingement of the relatively cool air discharged from openings (not shown) in a plurality of encircling discharge tubes 36.
  • the tubes 36 receive the cooling air from a supply header 34 which receives cool air from the fan case 12 by an opening 32 provided therein. Cooling airflow is regulated by a modulated valve 44 which is controlled by a controller 42 operating according to the method as disclosed hereinbelow.
  • turbofan engine 10 As noted in the preceding background section, the use of relatively cool air impinged directly on the turbine case 9 reduces turbine case temperature and, hence diameter, thereby reducing the radial clearance between the tips of the blades of the turbine rotor (not shown) and the surrounding annular shroud or air seal (not shown) which is supported concentrically within the outer turbine case 9.
  • the structural details of the turbofan engine 10 are well known in the art and will therefore not be repeated here.
  • Fig. 1 shows the transient response of the blade tip to shroud clearance ⁇ following a decrease in engine power level from steady state operation at operating or cruise power to flight idle power level or some other significantly reduced power level.
  • the reduction in power level occurs at time equals zero and results in an immediate increase in clearance from the steady state clearance corresponding to ⁇ MIN .
  • the immediate increase in blade tip to shroud clearance is the result of the corresponding decrease in rotor speed which reduces the centrifugal force on the turbine blades thereby reducing the overall diameter of the turbine blade tips.
  • the broken curve 102 in Fig. 1 represents the current state of the art for impingement cooling systems wherein the flow of cooling air to the turbine case 9 is controlled as a function of rotor speed.
  • the clearance ⁇ represented by curve 102 while experiencing an initial increase in clearance, the clearance ⁇ represented by curve 102 then decreases transiently as the temperature of the turbine case 9 declines to the steady state, part power level. Clearance then gradually increases to the part power steady state level ⁇ IDLE as the massive turbine rotor reaches its lower equilibrium temperature. The variation in clearance over time is thus a result of the heat capacity and response mismatch between the relatively thin turbine case 9 and the more massive turbine rotor (not shown).
  • broken curve 104 shows the effect on blade tip to shroud clearance of a subsequent acceleration of the engine back to cruise power level before the turbine rotor has reached flight idle temperature.
  • the relatively rapid increase in rotor speed results in a reimposition of centrifugal forces on the turbine blades and an increase in blade tip diameter.
  • This increase is relatively rapid and occurs more quickly than the concurrent thermal effect of the increasing temperature of working fluid on the turbine case 9.
  • the mismatch is shown by the excursion 106 of the curve 104 below ⁇ MIN , as shown in Fig. 1.
  • This excursion 106 can result in contact between the blade tips and the shroud, removing shroud material and permanently opening the clearance between the shroud and blade tips during subsequent operation of the gas turbine engine by removing shroud material, reducing overall gas turbine engine efficiency, increasing fuel consumption and shortening shroud service life.
  • the effect of a single excursion such as is shown by curve 104 may significantly or completely diminish the efficiency advantage achieved by the use of external turbine case cooling by causing the removal of a significant portion of the surrounding shroud or air seal.
  • the method according to the present invention recognizes that a temporary thermal mismatch between the turbine case and turbine rotor occurs following a significant deceleration or decrease in engine power and accommodates this mismatch by temporarily interrupting the operation of the cooling flow modulating control 42 when a decrease in engine power level is detected.
  • the method according to the present invention provides for a temporary interruption of cooling airflow to the turbine case 9 by substantially shutting the modulating valve 44 for a period of time following a decrease in engine power level.
  • the length of time of the decrease is a function of both the initial engine power level and of the magnitude of the reduction.
  • FIG. 1 A transient effect of the use of the method according to the present invention is shown in Fig. 1 by solid curve 108.
  • the reduction in engine power level from cruise to idle results in an immediate increase in the clearance ⁇ as a result of the decrease in turbine rotor speed.
  • this increased clearance is maintained by eliminating the flow of cooling air to the turbine case 9 temporarily, thereby resulting increased turbine case temperature and, hence diameter.
  • control of the flow of cooling air is returned to the normal controller 42 resulting in the curves which initiate at times T1, T2, and T3.
  • T1, T2, T3 are dependent on the initial rotor speed and magnitude of the decrease therein.
  • the method according to the present invention by providing increased radial clearance between the blade tips and shroud during the transient mismatch following a decrease in engine power level, provides sufficient radial clearance to accommodate a subsequent re-acceleration of the engine from reduced power to full or cruise power without experiencing a excursion beneath the minimum required clearance ⁇ MIN .
  • engine efficiency is temporarily reduced due to the increased clearance provided between the blade tips and shroud.
  • Such decrease in efficiency occurs only following a significant reduction in engine power level from cruise or operating power and only then for a period of time sufficient to protect the engine from the occurrence of interference during a subsequent re-acceleration. It has been estimated by a review of engine power level settings during a normal revenue flight that this reduction in efficiency averages a single occurrence per flight cycle and effects the operation of the engine for approximately 120 seconds, thus a temporary decrease in engine efficiency is the small price paid to avoid permanent removal of shroud material and permanent increase in blade tip to shroud clearance.
  • Fig. 2 shows a sample schedule used by the method according to the present invention for calculating the length of delay time P D which will be imposed by the method following a decrease in engine power level.
  • the method according to the present invention uses rotor speed or, in the case of a two spool gas turbine engine, high rotor speed as a measure of engine power level.
  • curves 112, 114, 116, 118 and 120 represent the range of initial rotor speed, N 2INIT initial while the horizontal axis represents the magnitude of the decrease in rotor speed, ⁇ N2 which are used by the method according to the present invention to determine the delay before returning control of the modulating valve 44 to the normal controller 42.
  • Fig. 2 For example, with an initial rotor speed of 11,500 rpm and a step decrease in rotor speed of 4,000 rpm, the method according to the present invention, using the schedule of Fig. 2 would maintain the modulating valve 44 in a closed position for approximately 410 seconds prior to returning control to the controller 42.
  • initial turbine rotor speeds of 10,250 rpm or less will not require any interruption of cooling airflow to the turbine case 9 for a decrease in rpm of any magnitude.
  • Fig. 2 also represents a practical lower limit on the change in rotor speed, ⁇ N2 which will trigger an interruption in cooling airflow.
  • This lower limit of 500 rpm represents a practical lower limit on the change in engine power level below which a thermal mismatch between the turbine rotor and case is relatively insignificant.
  • Fig. 2 is but one representation of the relationship between high rotor initial speed and the change in high rotor speed, and that other formulas and schedules may be used depending upon parameters such turbine case thermal response, turbine rotor thermal response, cooling capacity of the turbine case cooling system, etc.
  • the delay schedule may therefore be either calculated or determined experimentally for a given engine series or type.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)

Claims (2)

  1. Verfahren zum Steuern einer Strömung von Kühlluft zu einem Turbinengehäuse zum Steuern des radialen Spiels zwischen dem Gehäuse und einem innen angeordneten Rotor, umfassend die Schritte:
    (a) Vorsehen eines Programms für die Kühlluftströmung als eine Funktion der stationären Winkelgeschwindigkeit;
    (b) Messen der Winkelgeschwindigkeit des Rotors;
    (c) Anordnen eines Luftströmungsregelventils , das auf das vorgesehene Programm und die gemessene Winkelgeschwindigkeit anspricht; und
    (d) Überwachen der Große der Anderung der Rotorwinkelgeschwindigkeit; gekennzeichnet durch den Schritt:
    (e) Schließen des Ventils auf einen überwachten Abfall der Rotorwinkelgeschwindigkeit hin, der großer als ein vorgewählter Wert ist, wobei das Ventil für eine vorgewählte Zeitspanne nach dem überwachten Abfall geschlossen bleibt, wobei die vorgewählte Zeitspanne eine Funktion der Rotorwinkelgeschwindigkeit vor dem überwachten Abfall und zusätzlich eine Funktion der Größe des überwachten Abfalls ist.
  2. Verfahren nach Anspruch 1, wobei der vorgewählte Wert 500 U/min ist.
EP19900630181 1990-10-17 1990-10-17 Aktive Rotor-Statorspielregelung für Gasturbine Expired - Lifetime EP0481149B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
DE1990617685 DE69017685T2 (de) 1990-10-17 1990-10-17 Aktive Rotor-Statorspielregelung für Gasturbine.
EP19900630181 EP0481149B1 (de) 1990-10-17 1990-10-17 Aktive Rotor-Statorspielregelung für Gasturbine

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP19900630181 EP0481149B1 (de) 1990-10-17 1990-10-17 Aktive Rotor-Statorspielregelung für Gasturbine

Publications (2)

Publication Number Publication Date
EP0481149A1 EP0481149A1 (de) 1992-04-22
EP0481149B1 true EP0481149B1 (de) 1995-03-08

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EP19900630181 Expired - Lifetime EP0481149B1 (de) 1990-10-17 1990-10-17 Aktive Rotor-Statorspielregelung für Gasturbine

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EP (1) EP0481149B1 (de)
DE (1) DE69017685T2 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BR102013021427B1 (pt) 2013-08-16 2022-04-05 Luis Antonio Waack Bambace Turbomáquinas axiais de carcaça rotativa e elemento central fixo
GB201315365D0 (en) 2013-08-29 2013-10-09 Rolls Royce Plc Rotor tip clearance

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4230436A (en) * 1978-07-17 1980-10-28 General Electric Company Rotor/shroud clearance control system
US4329114A (en) * 1979-07-25 1982-05-11 The United States Of America As Represented By The Administrator Of The National Aeronautics And Space Administration Active clearance control system for a turbomachine
US4928240A (en) * 1988-02-24 1990-05-22 General Electric Company Active clearance control
US5076050A (en) * 1989-06-23 1991-12-31 United Technologies Corporation Thermal clearance control method for gas turbine engine

Also Published As

Publication number Publication date
DE69017685D1 (de) 1995-04-13
EP0481149A1 (de) 1992-04-22
DE69017685T2 (de) 1995-07-06

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