Document
United States Patent [19] 4,513,567
[ i l l Patent Number:
Deveau et al. [45] Date of Patent: Apr. 30, 1985
4,213,296 7/1980 Schwarz ........................... 60/39.141 [54] GAS TURBINE ENGINE ACTIVE 4,230,436 10/1980 Davison .................................. 415/1 CLEARANCE CONTROL 4,242,042 12/1980 Schwarz .............................. 415/116 [75] Inventors: Paul J. Deveau, Ellington; Paul B.
4,279,123 7/1981 Griffin et al. ...................... 60/226.1 Greenberg, Manchester; Roger E. 4,304,093 12/1981 Schulze .............................. 60/39.07 4,317,646 3/1982 Steel et al. .......................... 415/178 Paolillo, Vernon, all of Conn.
[73] Assignee: United Technologies Corporation, Primary Examiner-Louis J. Casaregola Hartford, Conn.
Assistant Examiner-Timothy S. Thorpe Attorney, Agent, or Firm-Norman Friedland; Robert C.
[21] Appl. No.: 576,770 Walker [22] Filed: Feb. 3 , 1984 [571 ABSTRACT Related U.S. Application Data Method for controlling the clearance between rotating and stationary components of a gas turbine engine are [63] Continuation of Ser. No. 317,633, Nov. 2, 1981, aban- doned. disclosed. Techniques for achieving close correspon- dence between the radial position of rotor blade tips and
[51] Int. Cl.3 ......................... F02G 3/00; FOlD 11/08
the circumscribing outer air seals are disclosed. In one
[52] U.S. C1. .................................... 60/39.02; 415/178
embodiment turbine case temperature modifying air is [58] Field of Search ............................ 60/39.02, 39.07; provided in flow rate, pressure and temperature varied 415/116, 117, 175, 178, 115 as a function of engine operating condition. The modi- 1561 References Cited fying air is scheduled from a modulating and mixing valve supplied with dual source compressor air. One U.S. PATENT DOCUMENTS source supplies relatively low pressure, low tempera- 3,039,737 6/1962 Kolthoff ................................ 415/17 ture air and the other source supplies relatively high Stanton ................................. 236/75 3,911,354 10/1975 pressure, high temperature air. After the air has been 3,914,952 10/1975 Barbier .................................. 236/75 415/1 16 used for the active clearance control (cooling the high 3,957,391 5/1976 Vollinger ............................
415/116 3,966,354 6/1976 Patterson ............................
pressure turbine case) it is then used for cooling the Brown et al. ....................... 415/116 3,975,112 8/1976 structure that supports the outer air seal and other high 3,975,901 SA976 Hallinger et al. ................ 60/39.141 pressure turbine component parts.
4,005,946 2/1977 Brown et al. ....................... 415/136 4,019,320 4/1977 Redinger et al. .................. 60/39.75 4,069,662 1/1978 Redinger et al. .................. 60/226.1 1 Claim, 5 Drawing Figures
U.S. Patent Apr. 30,1985 Sheet 1 of 5 4,513,567
U.S. Patent Apr. 30,1985 Sheet 2 of 5 4 , 5 13,567
FIG. 2
U . S . Patent Apr. 30,1985 Sheet 3 of 5 4,513,567
U . S . Patent Apr. 30,1985 Sheet 4 of 5
4,5 13,567
U.S. Patent Apr. 30,1985
Sheet 5 of 5 4,s 13,567
4,513,567
1 -
interior of the case. Cooling air is flowed along the GAS TURBINE ENGINE ACTIVE CLEARANCE interior of the engine between the working medium CONTROL flow path and the engine case.
U.S. Pat. Nos. 3,957,39 1 to Vollinger entitled “Tur- The invention described herein was made in the per- 5 bine Cooling”; 3,975,112 to Brown et a1 entitled “Appa- formance of work under NASA Contract No. NAS3- ratus for Sealing Gas Turbine Flow Path”; 4,005,946 to 20646 and is subject to the provisions Of Section 305 O f Brown et a] entitled “Method and Apparatus for Con- the National Aeronautics and Space Act Of 1958 (72 trolling Stator Thermal Growth”; and 4,242,042 to Stat. 435; 42 U.S.C. 2457).
Schwarz entitled “Temperature Control of Engine Case 10 for Clearance Control” representatively illustrated such CROSSREFERENCETORELATED APPLICATION concepts.
Notwithstanding the effectiveness of such prior art This is a continuation of application Ser. No. 317,633, systems, scientists and engineers in the gas turbine en- filed on Nov. 2, 1981, now abandoned.
gine industry are seeking yet improved systems employ- l 5 ing judicious use of coolingfieating air.
TECHNICAL FIELD DISCLOSURE OF THE INVENTION This invention relates to gas turbine engines, and more specifically to the active control of clearances According to the present invention the flow rate and between opposing Of the rotor and stator temperature of turbine case, temperature modifying air assemblies.
2o in an active clearance control system is varied by modu- lating proportions of relatively low temperature, low BACKGROUNDART pressure air and relatively high temperature, high pres- It is well known in the gas turbine industry that en- sure air in response to engine operating conditions.
gine performance is proportional to the leakage of In accordance with one detailed embodiment of the working medium gases between opposing seal elements 25 .
invention the case temperature modifying air is flow- of the rotor and stator assemblies. Techniques and con- able to one or more annular spaces circumscribing the cepts for reducing such clearances are continually cases to be controlled, and thence internally of the cases under investigation and development.
for Of components in proximity to the engine One class of techniques are those relating to ‘‘active clearance control” in which the clearances are set as a 30 flow path* A primary feature Of the present invention is the function of engine operating condition. The objective is utilization of dual source air for modifying the tempera- to establish minimum clearances under stable operating ture Of the engine case. low pressure, low conditions, yet to provide sufficient clearance during temperature air is mixed with relatively transient operation to preclude destructive interference between relatively rotating components. 35 high temperature high pressure air at one or more mod- U.S. Pat. Nos. 3,039,737 to Kolthoff entitled ‘‘Device ulating valves. The valves are capable of varying the for Controlling Clearance Between Rotor and Shroud Proportions of air from each source for effecting case of a Turbine”; 3,966,354 to Patterson entitled “Thermal cooling at differing flow rates and temperatures.
Actuated Valve for Clearance Control”; 3,975,901 to In one detailed embodiment a shroud circumscribes Hollinger et a1 entitled “Device for Regulating Turbine 40 each engine case to be controlled and is spaced apart Blade ~i~ Clearance”; and 4,2 13,296 to Schwarz enti- therefrom. Case temperature modifying air is flowable tied “Seal Clearance Control System for a Gas Tur- to the space. The modifying air is subsequently flowable bine” are representative of concepts and structures for through apertures in the case into the interior of the effecting local control over rotor blade tip clearances. engine for cooling components adjacent the engine flow In some embodiments relatively hot air is utilized ‘to 45 Path.
move the seals away from the rotor blade tips and in A principal advantage Of the present invention is the other embodiments relatively cool air is utilized to judicious use Of case temperature modifying air for move the seals toward the rotor blade tips. The con- controlling Case diameter. Internal clearances at seals cepts are at times combined in the same structure. between rotor and stator structure are minimized by Recent commercial aircraft gas turbine engines, such 50 matching the case d h - ~ e t e r to expected rotor growth as the JTgD-7R4 engine manufactured by Pratt & Whit- under varied engine operation conditions. AS viewed ney Aircraft, Division of United Technologies Corpo- from another aspect, turbine cooling air utilized to pro- ration, have incorporated clearance control systems tect engine components adjacent the flow path is di- operative on a large segment of the engine to closely verted en route to preliminarily modify the temperature match thermal growth of the stator elements to that of 55 of the engine case. Improved engine performance re- the rotor elements. Principally, cooling or heating air is sults from the sequential use of compressor air for such squirted onto the exterior of the engine case of the seg- auxiliary purposes as well as from actual clearance con- ment to be controlled. Desired contraction or expansion trol.
occurs. U.S. Pat. Nos. 4,069,662 to Redinger et a1 enti- The foregoing features and advantages of the present tled “Clearance Control for Gas Turbine Engine”; 60 invention will become more apparent in the light of the following detailed description of the best mode for 4,019,320 to Redinger et a1 entitled “External Gas Tur- bine Engine Cooling for Clearance Control”; and carrying out the invention and in the accompanying 4,279,123 to Griffin et a1 entitled “External Gas Turbine drawing.
Engine Cooling for Clearance Control” are representa- BRIEF DESCRIPTION O F THE DRAWING tive of the concepts employed in systems of the external 65 ~~ FIG. 1 is a simplified side elevation view of a gas type.
Advancing techniques for effecting segment cooling turbine engine with portions broken away in cross sec- now include the wide distribution of cooling air at the tion;
4.5 13,567
The modulating and mixing valve 54 is capable for FIG. 2 is a simplified side elevation view of a portion receiving the dual source air from the compressor and of the engine illustrating the dual course of turbine case, modulating the flow of each to produce an effluent temperature modifying air; having a desired temperature, pressure, and flow rate.
FIG. 3 is a simplified view of a portion of the turbine 5 In some embodiments the valve may be collaterally section of the engine illustrating the distribution of cool- capable of producing dual effluents, each having indi- ing air internally of the engine; and FIG. 4 is a “pinch point” diagram illustrating relative vidualized temperatures, pressures and flow rates. Ef- fluent from the valve is flowed to the turbine section of thermal growth between the rotor and stator of such an the engine through one or more conduits 58. In the engine.
10 structure illustrated a second modulating and mixing FIG. 5 is a partial view and an enlargement of the valve on the reverse side of the engine is capable of high pressure turbine section depicted in FIG. 3 to discharging effluent through a second conduit 60 to a show the flow pattern of this invention.
downstream position on the turbine. The first conduit BEST MODE FOR CARRYING OUT T H E 58 illustrated is capable of discharging to the high pres- INVENTION 15 sure turbine 16; the second conduit 60 illustrated is capable of discharging to the low pressure turbine 18.
An aircraft-type gas turbine engine capable of em- The FIG. 3 turbine cross section view illustrates the ploying the concepts of the present invention is illus- distribution of effluent from the modulating and mixing trated in the FIG. 1 partial cross section view. The engine principally includes a low pressure compression valves via the first conduit 58 to the high pressure tur- 20 bine 16 and via the second conduit 60 to the low pres- section 10, a high pressure compression section 12, a sure turbine 18.
combustion section 14, a high pressure turbine section 16 and a low pressure turbine section 18. The engine T o illustrate the flow charactenstics of this invention at the high pressure turbine, the structure of the high illustrated is of the dual rotor type having a first shaft 20 pressure turbine disclosed in FIG. 3 is enlarged in FIG.
joining a high turbine rotor assembly 22 to a high com- 25 5. As noted, the modulated air is conducted through pressor rotor assembly 24 and a second shaft 26 joining conduit 58 where it is admitted into the manifold 59 a low turbine rotor assembly 28 to a low compressor rotor assembly 30. which are segmented around the periphery of the row of high pressure turbine blades 40. The air is transmitted The respective rotor assemblies are contained within through a plurality of apertures where it is directed to a low compressor case 32, a high compressor case 34, a 30 impinge on the high pressure turbine case 36. The air is high turbine case 36 and a low turbine case 38. Rows of rotor blades, as represented by the single blades 40 then directed inwardly toward the engine centerline where it serves to cool the structure of manifold 59 and extend outwardly on the rotor blades toward the engine cases. Rows of stator vanes, as represented by the single the supporter hooks 63 and the attendant structure. A vanes 42, are supported from the engine cases and ex- portion of this air leaks between the adjacent supporting tend inwardly therefrom in interdigitated position with 35 structure and then into the engine air stream down- respect to the blades 40. A flow path 4 4 from working stream of the high pressure turbine blades 40 while the remaining air is directed downstream through openings medium gases extends axially through the engine be- 65 and 67 in the support structure and then between the tween rows of rotor blades and rows of stator vanes.
shield 69 and the inner diameter of the high pressure The rows of rotor blades 40 are circumscribed by essentially cylindrical outer air seals 46. The positions of 40 turbine case 36 where it dumps into the low pressure turbine section downstream thereof.
the outer air seals relative to the tips of the rotor blades In this manner, and as is apparent from the foregoing, is largely a function of the diameter of the engine case supporting the seals and of the temperature of the rotor the air utilized to control the gap between the outer air blades. Particularly, within the turbine section the rela- seal 46 and the tips of the high pressure turbine blades 45 40 is also used to cool the supporting structure. This tive positions, referred to as “clearance” may vary widely over the operating range of the engine as the negates the need to bring in air from a separate source to rotor blades and the case are subjected to differing cool these components as was done in the heretofore systems. Consequently, this avoids putting an undue thermal environments. Curve A of FIG. 4 represents the radial position of the rotor blade tips at a turbine thermal stress on the high pressure turbine case that section location as a function of engine operating condi- 50 would otherwise occur by having air from two different sources where one source may be cooler than the other tion. Curve B of FIG. 4 represents the radial position of the outer air seal at the corresponding turbine location and hence create a situation where considerably hotter as a function of engine operating condition. The gap X air is opposite the cooler impinging air and impairing its intended function of shrinking the case to close the gap between the two curves illustrates the expected clear- ance between the two relatively rotating components in 55 or vice versa. In the low turbine the case 38 is formed of an engine not employing the active clearance control double wall construction including an inner case 62 and concepts to be later described. an outer case or shroud 64. Effluent from the modulat- ing and mixing valve is flowable to a space 66 between The simplified side elevation view of FIG. 2 illus- trates apparatus incorporating the concepts of the pres- the inner case and shroud for the purpose of modifying ent invention. A first manifold 48 is in gas communica- 60 the temperature of the case as a function of engine oper- tion with the compressor at a relatively low pressure, ating condition. The modifying air is hence flowable low temperature stage. A second manifold 50 is in gas through apertures 68 in the inner case to the interior of communication with the compressor at a relatively high the engine for subsequently cooling engine components pressure, high temperature stage such as downstream of in the turbine.
the final compression stage. A low pressure conduit 52 During operation of the engine, working medium 65 connects the manifold 48 with a modulating and mixing gases are compressed within the compressor section to valve 54; a high pressure conduit 56 connects the mani- pressure ratios on the order of thirty to one (30:11 and fold 50 to the valve 54.
burned with fuel in the combustion section. The hot
4,5 13,567
- 6
effluent from the combustion section is expanded and exhaust gas temperature are selected for control.
through the turbine section to provide the motive force For the representative engine described above the pa- driving the compressor. Pressures across the compres- rameters shaft RPM, altitude, and flight Mach Number sor section of a typical engine increases at each succes- were selected for control.
sion stage from atmosphere pressure to the order of four hundred fifty pounds per square inch absolute (450 psia) at sea level take-off conditions. Correspondingly, tem- Flight peratures across the compressor section increase at each Low Rotor High Rotor Mach Speed Speed Altitude Number succesive stage from ambient conditions to the order of eleven hundred fifty degrees Fahrenheit (1 150" F.) at 11 15 RPM 10,063 RPM 0 ft. 0.0 10 Ground Idle sea level take-off conditions. Corresponding tempera- 0 ft. 0.0 Sea Level 3923 RPM 14,045 RPM tures at the inlet to the turbine section are on the order Take Off of twenty-five hundred degrees Fahrenheit (2500" F.).
Cruise 3902 RPM 13,178 RPM 35,Goo ft. .80 Radical variations in engine temperatures over the op- erating cycle of the engine establish the need for control of clearances between rotating and stationary structures Referring again to the FIG. 4 "pinch point" diagram under the influence of differing environments. curve C represents the radial position of an outer air seal The concepts of the present invention employ case as it is varied over the engine operating range by modi- heating and case cooling in accord with the engine fying the supporting case in accordance with the pres- cycle to achieve close growth correspondence between 20 ent concepts in accordance with the sensed parameters, the rotor and the case supported seals. Case temperature shaft RPM, altitude and flight Mach Number. The gap modifying air is utilized for such heating and cooling.
Y represents the attainable relative clearance between The modifying air comprises varied proportions of the tips of the rotor blades and the corresponding outer heating and cooling air ducted from the engine com- air seal. Clearance is not only greatly reduced from the pressor to the case segment to be cooled. Representa- 25 non-controlled conditions, but closely corresponds in tive characteristics of case temperature modifying air contour to the radial position of the tips. The minimum produced as the eflluent from a modulating and mixing clearance necessary to avoid destructive interferences is valve, such as that described herein, is shown in the provided.
table reproduced below. The pressure, temperature and Although the invention has been described with re- flow rate data is representative of a forty thousand 30 spect to a particular turbine embodiment, it should be (40,000) pound thrust class engine at idle, sea level take- .
understood that the invention is not so limited and that off and cruise conditions. Data is for a split-type system in which a first modulating valve is supplied with dual various changes and modifications may be made with- source air for discharge and temperature control of the out departing from the spirit and scope of this novel high pressure turbine case and a second modulating 35 concept.
valve is supplied with dual source air for discharge and We claim: temperature control of the low pressure turbine case.
1 . A method of controlling the clearance between opposing seal elements of the rotor assembly and the stator assembly including supporting structure of a dual Low Pres- High Pres- High 40 rotor gas turbine engine having high pressure compres- sure Low sure High Turbine Tempera- Tempera- Modifying sor and high pressure turbine, low compressor and high ture Source ture Source Air ~ pressure turbine rotors comprising the steps of: HIGH PRESSURE TURBINE flowing relatively low pressure, low temperature air Idle Pressure 27 psia 61 psia 25 psia from the compressor of the engine to a modulating Temp 290°F. 430" F. 430" F.
Flow Rate 0.0 Ib m/sec 45 and mixing valve; .06 Ib m/sec .06 Ib m/sec Sea Pressure 136 psia 431 psia 130 psia flowing relatively high pressure, high temperature air Level Temp 720" F. 1110" F. 970' F.
from the compressor of the engine to said modulat- Take- Flow Rate .10 Ib m/sec .22 Ib m/sec .32 Ib m/sec ing and mixing valve; O f f Cruise Pressure 65 psia 197 psia 60 psia mixing said relatively low pressure, low temperature Temp 580" F. 9 W F. 580" F. 50 air and said relatively high pressure, high tempera- Flow Rate ,155 Ib m/sec 0.0 Ib m/sec .I55 Ib m/sec ture air at the modulating valve in proportions LOW PRESSURE TURBINE functionally related to engine operating condition Idle Pressure 20 psia 61 psia 0 220" F. 430" F.
Temp 0 to produce a mixture of air having a desired tem- Flow Rate 0.0 Ib m/sec 0.0 Ib m/sec 0 perature, pressure and flow rate at that operating Sea Pressure 75.0 psia 431 psia 62 psia 5 5 condition for thermally modifying the diameter of Level Temp 580°F. 1110" F. 820" F.
Flow Rate ,642 Ib m/sec ,526 Ib m/sec Take- 1.168 Ib m/sec the turbine case adjacent said high pressure turbine; off flowing said mixed air to the high pressure turbine Cruise Pressure 33 psia 197 psia 28 psia section of the engine and against the case thereof Temp 420" F. 900' F. 420" F.
Flow Rate .56 Ib m/sec 0.0 Ib m/sec .56 Ib d s e c for thermally varying the diameter of said case to achieve control over clearances between the rotor and stator assemblies of said high pressure turbine Each of the one or more modulating valves is con- and admitting the effluent mixed air from said case trollable in response to engine operating conditions to so as to cool said supporting internally thereof produce the effluents described above. The modulating 65 structure; valves are controllable in response to engine operating flowing relatively low pressure, low temperature air conditions. Parameters representative of engine condi- tion, such as case temperature, rotor speed, engine pres- from the compressor of the engine to a second sure rates, altitude Mach Number, turbine temperature modulating and mixing valve;
4,5 13,567
ing condition for thermally modifying the diameter flowing relatively high pressure, high temperature air of the turbine case; and from the compressor of the engine to said second flowing said air mixed at the second modulating vaive modulating and mixing valve; to the case of the low pressure turbine at a location mixing said relatively low pressure, low temperature downstream of the location to which the air mixed air and said relatively high pressure, high tempera- at the first modulating valve was flowed and ture air at the second modulating valve in propor- against the case at that downstream location for tions functionally related to engine operating con- thermally varying the diameter of the case at that dition to produce a mixture of air having a desired location.
* * + * * temperature, pressure and flow rate at that operat- 10 3 0