NASA-TM-214341-2006 Sealing in Turbomachinery《涡轮机械的密封》.pdf

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1、Raymond E. ChuppGeneral Electric Global Research, Niskayuna, New YorkRobert C. HendricksGlenn Research Center, Cleveland, OhioScott B. LattimeThe Timken Company, North Canton, OhioBruce M. SteinetzGlenn Research Center, Cleveland, OhioSealing in TurbomachineryNASA/TM2006-214341August 2006Provided by

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11、without license from IHS-,-,-NASA/TM2006-214341August 2006National Aeronautics andSpace AdministrationGlenn Research CenterCleveland, Ohio 44135Raymond E. ChuppGeneral Electric Global Research, Niskayuna, New YorkRobert C. HendricksGlenn Research Center, Cleveland, OhioScott B. LattimeThe Timken Com

12、pany, North Canton, OhioBruce M. SteinetzGlenn Research Center, Cleveland, OhioSealing in TurbomachineryProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-AcknowledgmentsSealing in turbomachinery has been the focus of numerous development efforts. Many

13、of these developers have been cited here.The authors would like to especially acknowledge contributors to this review paper: Mahmut Aksit (cloth static seals and extensivelyreviewing this paper), Margaret Proctor (finger seals), Norm Turnquist (aspirating seals), Saim Dinc and Mehmet Demiroglu(brush

14、 seals), Stephen Stone and Greg Moore (metallic static seals) and Farshad Ghasripoor (abradables). We also wish to thankour sponsoring organizations for the time and resources to prepare this paper.Available fromNASA Center for Aerospace Information7121 Standard DriveHanover, MD 210761320National Te

15、chnical Information Service5285 Port Royal RoadSpringfield, VA 22161Available electronically at http:/gltrs.grc.nasa.govTrade names and trademarks are used in this report for identificationonly. Their usage does not constitute an official endorsement,either expressed or implied, by the National Aero

16、nautics andSpace Administration.Level of Review: This material has been technically reviewed by technical management.This report is a formal draft or workingpaper, intended to solicit comments andideas from a technical peer group.This report contains preliminary findings,subject to revision as analy

17、sis proceeds.Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2006-214341 1Sealing in Turbomachinery Raymond E. Chupp General Electric Global Research Niskayuna, New York 12302 Robert C. Hendricks National Aeronautics and Space Administration G

18、lenn Research Center Cleveland, Ohio 44135 Scott B. Lattime The Timken Company North Canton, Ohio 44720 Bruce M. Steinetz National Aeronautics and Space Administration Glenn Research Center Cleveland, Ohio 44135 Abstract Clearance control is of paramount importance to turbomachinery designers and is

19、 required to meet todays aggressive power output, efficiency, and operational life goals. Excessive clearances lead to losses in cycle efficiency, flow instabilities, and hot gas ingestion into disk cavities. Insufficient clearances limit coolant flows and cause interface rubbing, overheating downst

20、ream components and damaging interfaces, thus limiting component life. Designers have put renewed attention on clearance control, as it is often the most cost effective method to enhance system performance. Advanced concepts and proper material selection continue to play important roles in maintaini

21、ng interface clearances to enable the system to meet design goals. This work presents an overview of turbomachinery sealing to control clearances. Areas covered include: characteristics of gas and steam turbine sealing applications and environments, benefits of sealing, types of standard static and

22、dynamics seals, advanced seal designs, as well as life and limitations issues. I. Introduction Controlling interface clearances is the most cost effective method of enhancing turbomachinery performance. Seals control turbomachinery leakages, coolant flows and contribute to overall system rotordynami

23、c stability. In many instances, sealing interfaces and coatings are sacrificial, like lubricants, giving up their integrity for the benefit of the component. They are subjected to abrasion, erosion, oxidation, incursive rubs, foreign object damage (FOD) and deposits, extremes in thermal, mechanical,

24、 aerodynamic and impact loadings. Tribological pairing of materials control how well and how long these interfaces will be effective in controlling flow. A variety of seal types and materials are required to satisfy turbomachinery sealing demands. These seals must be properly designed to maintain th

25、e interface clearances. In some cases, this will mean machining adjacent surfaces, yet in many other applications, coatings are employed for optimum performance. Many seals are coating composites fabricated on superstructures or substrates that are coated with sacrificial materials which can be refu

26、rbished either in situ or by removal, stripping, recoating and replacing until substrate life is exceeded. For blade and knife tip sealing an important class of materials known as abradables permit blade or knife rubbing without significant damage or wear to the rotating element while maintaining an

27、 effective sealing interface. Most such tip interfaces are passive, yet some, as for the high-pressure turbine (HPT) case or shroud, are actively controlled. This work presents an overview of turbomachinery sealing. Areas covered include: characteristics of gas and steam turbine sealing applications

28、 and environments, benefits of sealing, types of standard static and dynamics seals, advanced seal designs, as well as life and limitations issues. II. Sealing in Gas and Steam Turbines A. Clearance Control Characteristics Turbomachines range in size from centimeters (size of a penny) to ones you ca

29、n almost walk through. The problem is how to control the large changes in geometry between adjacent rotor/stator components from cold-build to operation. The challenge is to provide geometric control while maintaining efficiency, integrity and long service life (e.g., estimated time to failure or ma

30、intenance, and low cost1). Figure 1 shows the relative clearance between the rotor tip and case for a HPT during takeoff, climb, and Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2006-214341 2Figure 1.Effects of case cooling on HPT blade tip

31、 clearance during takeoff.2 cruise conditions.2The figure shows the dramatic effect of clearance control via applied cooling to the casing. A critical clearance requirement occurs at “cut-back” (about 1000 sec into climb-out) when takeoff thrust is reduced. Using thermal active clearance control (AC

32、C), the running clearance is drastically reduced, producing significant cost savings in fuel reduction and increased service life. However, designers must note that changing parameters in critical seals can change the dynamics of the entire engine.3These effects are not always positive. B. Sealing B

33、enefits Performance issues are closely tied to engine clearances. Ludwig4determined that improvements in fluid film sealing resulting from a proposed research program could lead to an annual energy saving, on a national basis, equivalent to about 37 million barrels (1.554 billion U.S. gallons) of oi

34、l or 0.3 percent of the total U.S. energy consumption (1977 statistics). In terms engine bleed, Moore5cited that a 1 percent reduction in engine bleed gives a 0.4 percent reduction in specific fuel consumption (SFC), which translates into nearly 0.033 (1977 statistics) to 0.055 (2004 statistics) bil

35、lion gallons of U.S. airlines fuel savings and nearly 0.28 billion gallons world wide (2004 statistics), annually. In terms of clearance changes, Lattime and Steinetz6cite a 0.0254 mm (0.001 in.) change in HPT tip clearance, decreases SFC by 0.1 percent and EGT (exhaust gas temperature) by 1 C, prod

36、ucing an annual savings of 0.02 billion gallons for U.S. airlines. In terms of advanced sealing, Munson et al.7estimate savings of over 0.5 billion gallons of fuel. Chupp et al.8estimated that refurbishing compressor seals would yield impressive improvements across the fleet ranging from 0.2 to 0.6

37、percent reduction in heat-rate and 0.3 to 1 percent increase in power output. For these large, land-based gas turbines, the percentages represent huge fuel savings and monetary returns with the greatest returns cited for aging power systems. C. The Sealing Environment 1. Seal Types and Locations Key

38、 aero-engine sealing and thermal restraint locations cited by Bill9are shown in figure 2. These include the fan and compressor shroud seals (rub strips), compressor interstage and discharge seals (labyrinth), combustor static seals, balance piston sealing, turbine shroud and rim-cavity sealing. Indu

39、strial engines have similar sealing requirements. Key sealing locations for the compressor and turbine in an industrial engine are cited by Aksit10and Camatti et al.11,12and are shown in figures 3 and 4. Figure 3 shows high-pressure compressor (HPC) and HPT tip seal (abradable) and interstage seal (

40、brush seal) locations, while figure 4 shows impeller shroud (labyrinth) and interstage seal (honeycomb) locations for the compressor. Compressor interstage platform seals are of the shrouded type (figs. 5 and 6). These seals are used to minimize backflow, stage pressure losses and re-ingested passag

41、e flow. Turbine stators, also of the shrouded type, prevent hot gas ingestion into the cavities that house the rotating disks and control Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2006-214341 3blade and disk coolant flows. Designers need

42、 to carefully consider the differences in thermal and structural characteristics, pressure gradient differences, and blade rub interfaces. Characteristically the industrial gas turbine can be thought of as a heavy-duty derivative of an aero engine. Still industrial and aero-turbomachines have many d

43、ifferences. The most notable are the fan, spools and combustor. Aero engines derive a large portion of their thrust through the bypass fan and usually have inline combustors, high and low pressure spools, drum rotors and high exhaust velocities, all subject to flight constraints. Large industrial en

44、gines (fig. 7) have plenum inlets, can-combustors, single spools, through-bolted-stacked disc rotors and exhaust systems constrained by 640 C (1180 F) combined cycle (steam-reheat-turbine) requirements. In both types of engines, core requirements are similar, yet materials restraints differ. Figure

45、2.Key aero-engine sealing and thermal restraint locations.9Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2006-214341 4Figure 3.Advanced seals locations in a Frame 7EA gas turbine.10 Figure 4.Compressor cross-sectional drawing showing detail

46、of rotor and seals. (a) Impeller shroud labyrinth seal. (b) Honeycomb interstage seal. (c) Abradable seal. (d) Honeycomb interstage seal.12 Figure 5.Engine schematic showing main-shaft seal locations.4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-N

47、ASA/TM2006-214341 5Figure 6.Compressor sealing locations. (a) Blade tip and interstage. (b) Drum rotor.4 2. Materials and Environmental Conditions Over the years, advances in new base materials, notably Ni-based single crystal alloys, and coatings have allowed increased operating temperatures of tur

48、bine engine components. Complementary to the thermal and pressure profiles, materials used range from steel to superalloys coated with metallics and ceramics. Variations in engine pressure and temperature of the Rolls-Royce Trent gas turbine*are illustrated in figure 8. The lower temperature blades

49、in the fan and low-pressure compressor (LPC) sections are made of titanium, or composite materials, with corrosion resistant coatings due to their high strength and low density. The elevated temperatures of the HPC, HPT and low-pressure turbine (LPT) require the use of Nickel-based superalloys. In the HPT of aero-engines, for e