EP0481149A1 - Aktive Rotor-Statorspielregelung für Gasturbine - Google Patents

Aktive Rotor-Statorspielregelung für Gasturbine Download PDF

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Publication number
EP0481149A1
EP0481149A1 EP90630181A EP90630181A EP0481149A1 EP 0481149 A1 EP0481149 A1 EP 0481149A1 EP 90630181 A EP90630181 A EP 90630181A EP 90630181 A EP90630181 A EP 90630181A EP 0481149 A1 EP0481149 A1 EP 0481149A1
Authority
EP
European Patent Office
Prior art keywords
rotor
turbine
case
engine
decrease
Prior art date
Legal status (The legal status 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 status listed.)
Granted
Application number
EP90630181A
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English (en)
French (fr)
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EP0481149B1 (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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Filing date
Publication date
Application filed by United Technologies Corp filed Critical United Technologies Corp
Priority to DE1990617685 priority Critical patent/DE69017685T2/de
Priority to EP19900630181 priority patent/EP0481149B1/de
Publication of EP0481149A1 publication Critical patent/EP0481149A1/de
Application granted granted Critical
Publication of EP0481149B1 publication Critical patent/EP0481149B1/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.
  • 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. 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 (now 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 6 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 6 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 6 represented by curve 102 while experiencing an initial increase in clearance, the clearance 6 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 6IDLE 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 6 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 6 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 T i , T 2 , and T 3 .
  • T i , T 2 , T 3 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 6 MIN -It should be noted, for that period in which the method according to the present invention has cut the flow of cooling air to the turbine case, engine efficiency is temporarily reduced due to the increased clearance provided between the blade tips and shroud.
  • 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 21NIT initial while the horizontal axis represents the magnitude of the decrease in rotor speed, N 2 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, N 2 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.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
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 true EP0481149A1 (de) 1992-04-22
EP0481149B1 EP0481149B1 (de) 1995-03-08

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Family Applications (1)

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

Country Status (2)

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

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015021522A1 (pt) 2013-08-16 2015-02-19 Milani Paulo Giacomo Turbomáquinas axiais de carcaça rotativa e elemento central fixo
US9657587B2 (en) 2013-08-29 2017-05-23 Rolls-Royce Plc Rotor tip clearance

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2025536A (en) * 1978-07-17 1980-01-23 Gen Electric Turbine rotor/shroud clearance control system
GB2054741A (en) * 1979-07-25 1981-02-18 Gen Electric Active clearance control system for a turbomachine
EP0330492A2 (de) * 1988-02-24 1989-08-30 General Electric Company Aktivkontrolle des Zwischenraumes
FR2648864A1 (fr) * 1989-06-23 1990-12-28 United Technologies Corp Procede de commande thermique du jeu radial a l'endroit des bouts des ailettes d'un turbomoteur

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2025536A (en) * 1978-07-17 1980-01-23 Gen Electric Turbine rotor/shroud clearance control system
GB2054741A (en) * 1979-07-25 1981-02-18 Gen Electric Active clearance control system for a turbomachine
EP0330492A2 (de) * 1988-02-24 1989-08-30 General Electric Company Aktivkontrolle des Zwischenraumes
FR2648864A1 (fr) * 1989-06-23 1990-12-28 United Technologies Corp Procede de commande thermique du jeu radial a l'endroit des bouts des ailettes d'un turbomoteur

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2015021522A1 (pt) 2013-08-16 2015-02-19 Milani Paulo Giacomo Turbomáquinas axiais de carcaça rotativa e elemento central fixo
US9657587B2 (en) 2013-08-29 2017-05-23 Rolls-Royce Plc Rotor tip clearance

Also Published As

Publication number Publication date
DE69017685D1 (de) 1995-04-13
DE69017685T2 (de) 1995-07-06
EP0481149B1 (de) 1995-03-08

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