1、Margaret P. ProctorGlenn Research Center, Cleveland, OhioIrebert R. DelgadoU.S. Army Research Laboratory, Glenn Research Center, Cleveland, OhioLeakage and Power Loss Test Resultsfor Competing Turbine Engine SealsNASA/TM2004-213049April 2004GT200453935Provided by IHSNot for ResaleNo reproduction or
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11、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-Margaret P. ProctorGlenn Research Center, Cleveland, OhioIrebert R. DelgadoU.S. Army Research Laboratory, Glenn Research Center, Cleveland, OhioLeakage and Power Loss Test Resultsfor Competing Turbine Engine SealsNASA/TM
12、2004-213049April 2004National Aeronautics andSpace AdministrationGlenn Research CenterPrepared for theTurbo Expo 2004sponsored by the American Society of Mechanical EngineersVienna, Austria, June 1417, 2004GT200453935Provided by IHSNot for ResaleNo reproduction or networking permitted without licens
13、e from IHS-,-,-AcknowledgmentsThe authors acknowledge the contributions of Arun Kumar and his colleagues at Honeywell Engines, Systems and significant heat generation at the seals could expose downstream components to temperatures that exceed material capabilities. Baseline labyrinth and brush seals
14、 were tested in NASA Glenn Research Centers High-Speed, High-Temperature Turbine Seal Test Rig. Static, performance, and endurance tests were conducted. The results of these baseline tests are compared to each other and to finger seal leakage and power loss performance data obtained in the same test
15、 rig. Brush and finger seal wear results are presented along with an assessment of the rotor coating performance. NOMENCLATURE A = contact area Dseal= outside diameter of the test rotor, m D1= bearing bore diameter, m P = contact pressure Power= frictional seal power loss Pu= air pressure upstream o
16、f seal, MPa T = torque loss, N-m Tavg= average seal air inlet temperature, K U = surface velocity W = load on bearing, N f = friction coefficient m= air leakage flow rate, kg/s = friction coefficient = flow factor, kg-K/MPa-m-s TEST HARDWARE Labyrinth Seal Used for many years to control leakage acro
17、ss a stationary/rotating interface within jet engines, labyrinth seals are clearance seals composed of a number of axially spaced knife edges offset a distance from the opposing surface. A pressure drop, as exists between compressor or turbine stages within a jet engine, is present across the labyri
18、nth seal due to its alternating series of knife edges and cavities which dissipates the kinetic energy of the fluid flowing through it 1. However, the labyrinth seals sealing capability is limited by the need to maintain a clearance from the rotating surface. This, in turn, limits the amount of leak
19、age that can be controlled which affects the maximum engine performance. The labyrinth seal used in this study, fig. 1, was designed using the KTK computer code 2 to predict its leakage performance. KTK calculates the leakage and pressure distribution through labyrinth seals based on a detailed knif
20、e-to-knife analysis. The labyrinth seal tested isProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2004-213049 2Figure 1.Four-knife labyrinth seal made of Inconel 625. a straight four-knife design with a nominal 229 m radial clearance at assembl
21、y with the 215.9 mm diameter rotor. The 229 m radial clearance is too small to ensure non-contacting operation at temperature and speed. Hence, only static room temperature tests were conducted. Key design features are given in table 1. Table 1.Labyrinth seal design parameters. Material Inconel 625
22、Type straight Number of knives 4 Rotor outer diameter 215.9 mm Tooth height 2.286 mm Tooth taper angle 7.5 degrees Land thickness 305 m Tooth pitch 3.175 mm Radial clearance 127 m Seal inner diameter 216.154 mm Brush Seal Brush seals are contacting seals composed of a dense pack of high-temperature
23、alloy wires captured between stationary plates and pointed inward towards the rotating surface at an angle to the radius of the seal. They control leakage more effectively than labyrinth seals 3 because their compliant nature permits a smaller clearance to be used and the bristles track rotor radial
24、 growth due to rotation and temperature. However frictional heating due to contact with the rotating surface tends to quickly wear the brush seal and limit its useful life. A commercially available brush seal (fig. 2) with a flow deflector was used for this study. It is composed of Inconel-625 sidep
25、lates and 102 m diameter Haynes-25 bristles at a 50 angle to the radius. The bristle density at the seal inner diameter (id) is approximately 675 bristles/cm of circumference. The initial radial interference with the rotor was 96.5 m. The fence height, the distance between the rotor and the downstre
26、am side plate, is 1.27 mm. The total axial thickness of the brush seal was 4.27 mm. It should be noted that brush seal designs vary, and that brush seal leakage performance is strongly dependent on bristle pack stiffness and density, bristle angle, fence height, materials, etc. The brush seal tested
27、 is only one design and may or may not be the optimum for any aircraft engine application. It is, however, representative of typical brush seals used under the conditions at which the tests were conducted. Figure 2.Brush seal with flow deflector. Finger Seal In the mid to late 1990s a pressure balan
28、ced, low hysteresis finger seal was successfully developed and tested at NASA Glenn Research Center 4 and subsequently patented by AlliedSignal Engines 5. In 2002 a 215.9 mm id pressure balanced finger seal was tested at inlet air temperatures up to 922 K, speeds up to 366 m/s, and pressure differen
29、tials up to 517 kPa 6. Brush and labyrinth seal performance data are compared to this data. The finger seal, fig. 3, is composed of a series of finger elements sandwiched between aft and forward spacers and cover plates. Each finger element has been machined to create a series of slender curved beam
30、s or fingers around its inner diameter. The finger elements are alternately indexed so that the fingers of one element cover the spaces between the fingers on the adjacent element. The flexible fingers can bend radially to accommodate shaft excursions and relative growth of the seal and rotor result
31、ing from rotational forces and thermal mismatch. The seal is made of sheet AMS5537, a cobalt-base alloy which has good formability, excellent high temperature properties, and displays excellent resistance to the hot corrosive atmospheres encountered in jet engine operations. The finger seal had an i
32、nitial radial interference with the rotor of 165 m. Test Rotors The test rotors used were nominally 215.9 mm in diameter and made of Grainex Mar-M-247. Their outer diameters were coated with chromium-carbide (CrC) applied with a high-velocity oxygen-fuel (HVOF) thermal spray process. The same rotor
33、was used for the labyrinth and brush seals and had an inspected outer diameter (od) of 215.8975 mm. The rotor for the finger seal had an inspected od of 215.8949 mm. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2004-213049 3TEST APPARATUS T
34、urbine Seal Test Rig In the NASA High Temperature, High Speed Turbine Seal Test Rig, fig. 4, the 215.9 mm diameter test rotor is mounted on a shaft in an overhung configuration. The shaft is supported by two oil-lubricated bearings. A balance piston controls the axial thrust load on the bearings due
35、 to pressure loads on the test rotor. An air turbine drives the test rig. A torquemeter is located between the air turbine and the test rig and is connected to each by a quill shaft. The test seal is clamped into the Grainex Mar-M 247 seal holder as shown in figure 5. A C-seal located at the seal ho
36、lder/test seal interface prevents flow from bypassing the test seal at its outer diameter. The seal holder is heated to approximately match the thermal growth of the rotor and to prevent a change in radial clearance that may damage the seal and/or rotor. Heated, filtered air enters the bottom of the
37、 test rig and passes through an inlet plenum that directs the heated air axially toward the sealrotor interface. The hot air either leaks through the test seal to the seal exhaust line or exits the rig before the test seal through a controlled bypass line at the top of the rig. If seal leakage is lo
38、w, the bypass line must be open to maintain sufficient flow through the test rig to keep the rig hot. Instrumentation Seal inlet and exit temperatures and static pressures, seal upstream metal temperature (finger seal only), and seal Figure 3.Finger seal design. backface temperatures were measured a
39、t the locations shown in figure 5. For each measurement there were 3 probes equally spaced around the circumference, except for the upstream seal metal temperature for which 2 thermocouples were located at the 90 and 180 positions (0 is top-dead-center). Type-K thermocouples were used and all were 1
40、57 m, Inconel sheath, closed ball except the seal exit temperatures, which were 3.2 mm diameter and the seal metal and backface temperatures, which were open-ball. High temperature capacitance proximity probes were mounted in the seal holder at four equally-spaced locations to view the test rotor ou
41、ter diameter. These probes were used to measure the change in clearance between the seal holder and the rotor and to monitor the rotordynamic behavior of the test rotor. The average inlet air temperature is used as the probe temperature when correcting the probe output. These proximity probes have a
42、n accuracy of 5 m at room temperature. Proximity probe data were only available for some of the finger seal tests due to instrumentation problems. Figure 4.High-temperature, high-speed turbine seal rig. Figure 5.Test seal configuration and location of research measurements. Provided by IHSNot for Re
43、saleNo reproduction or networking permitted without license from IHS-,-,-NASA/TM2004-213049 4Pitot tube-type flow meters are used to measure the flow rates of the hot air supplied to the rig and the air exiting the rig through the bypass line. The seal leakage rate is the difference between these tw
44、o flow measurements. The seal leakage rate is then used to calculate the flow factor, which is defined as: avgusealmTPD=, kg-K/MPa-m-s (1) The flow factor can be used to compare the leakage performance of seals with different diameters and with different operating conditions. The accuracy of the mea
45、sured flow factor is 1.5%. A phase shift torquemeter measures the total torque of the seal test rig and compensates for any relative motion between the torsion shaft and stator. The torquemeter is rated to 22 N-m, has a maximum operating speed of 5236 rad/s, and an absolute accuracy of 0.13% or 0.02
46、8 N-m. The calculated seal torque is the measured rig torque with the test seal installed minus the rig tare torque. The rig tare torque was measured at various inlet air temperatures and speeds with no seal installed. This data was two-dimensionally curve fitted. The fitted curve is used with the m
47、easured average inlet air temperature and speed to infer the corresponding tare torque. Seal power loss is calculated as the seal torque multiplied by speed. The maximum error in the seal power loss measurements is 97.7 W over the range of test conditions. The speed measurement from the torquemeter
48、is accurate to 0.04% or 1.4 rad/s at the maximum speed tested. TEST PROCEDURES Pre-test photographs were taken of all seals and rotors. Additionally, the seals were weighed and the rotor surface profile was recorded using a Talysurf profilometer. Labyrinth seal tests were limited to static tests (no
49、 rotation) at room temperature where the pressure differential across the seal was increased to 483 kPa and back down to zero psid in 69 kPa increments. At each pressure differential, approximately 10 seconds of leakage data was recorded. Four tests were conducted on both the brush seal and on the finger seal: a static leakage test, a performance t
