Investigation of Positive Type Shaft Seals Final Report
Flow correlation and predictability in static seal leakage
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Experimental investigation of self-acting-lift-pad characteristics for main-shaft seal applications
Shrouded step pads for separating seal surfaces
Hady, W. F.↗
High speed, self-acting, face-contact shaft seal has low leakage and very low wear
Design adds gas thrust bearing to face of conventional face seal. Bearing lifts seal's carbon face out of contact after startup and establishes thin gas film between sealing surfaces. Operating pressure and speed capabilities are greater than those of conventional face seals.
Zuk, J.↗
Design study of shaft face seal with self-acting lift augmentation. 5: Performance in simulated gas turbine engine operation
The feasibility and the noncontact operation of the self-acting seal was demonstrated over a range of simulated gas turbine engine conditions from 200 to 500 ft/sec sliding speed. Sealed pressure differentials were 50 to 300 psi and sealed temperatures were 150 to 1200 F. Low leakage (about 1/10 that of conventional labyrinth seals) was exhibited in two endurance runs (200 and 338 hr) at 400 ft/sec, 200 psi and 1000 F (gas temperature). For these endurance runs, the self-acting pad wear was less than 3.8 micrometers (0.00015 in.); this low wear was attributed to the noncontact operation of the primary seal. Operating problems identified were fretting wear of the secondary seal and erosion of the primary seal by hard particles.
Ludwig, L. P.↗
Design study of shaft face seal with self-acting lift augmentation. 4: Force balance
A method for predicting the operating film thickness of self-acting seals is described. The analysis considers a 16.76-cm mean diameter seal that is typical of large gas turbines for aircraft. Four design points were selected to cover a wide range of operation for advanced engines. This operating range covered sliding speeds of 61 to 153 m/sec, sealed pressures of 45 to 217 N/sq cm abs, and gas temperatures of 311 to 977 K. The force balance analysis revealed that the seal operated without contact over the operating range with gas film thicknesses ranging between 0.00046 to 0.00119 cm, and with gas leakage rates between 0.01 to 0.39 scmm.
Ludwig, L. P.↗
Self-acting and hydrodynamic shaft seals
Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis revealed three different vibration modes. Proposed applications of self-acting seals in gas turbine engines and in rocket vehicle turbopumps are described. Also experimental data on self-acting face seals operating under simulated gas turbine conditions are given; these data show the feasibility of operating the seal at conditions of 345 newtons per square centimeter (500 psi) and 152 meters per second (500 ft/sec) sliding speed.
Ludwig, L. P.↗
Self-acting and hydrodynamic shaft seals.
Self-acting and hydrodynamic seals are described. The analytical procedures are outlined for obtaining a seal force balance and the operating film thickness. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis revealed three different vibration modes. Proposed applications of self-acting seals in gas turbine engines and in rocket vehicle turbopumps are described. Also experimental data on self-acting face seals operating under simulated gas turbine conditions are given; these data show the feasibility of operating the seal at conditions of 345 newtons per square centimeter (500 psi) and 152 meters per second (500 ft/sec) sliding speed.
Ludwig, L. P.↗
US studies in the field of shaft drilling on the lunar surface
American equipment for drilling in the lunar surface is discussed, with emphasis on rotary-percussive methodology and core-sample retrieval techniques.
Zakharyev, B. V.↗
Combined bending-torsion fatigue reliability of AISI 4340 steel shafting with K sub t = 2.34
Results generated by three, unique fatigue reliability research machines which can apply reversed bending loads combined with steady torque are presented. Six-inch long, AISI 4340 steel, grooved specimens with a stress concentration factor of 2.34 and R sub C 35/40 hardness were subjected to various combinations of these loads and cycled to failure. The generated cycles-to-failure and stress-to-failure data are statistically analyzed to develop distributional S-N and Goodman diagrams. Various failure theories are investigated to determine which one represents the data best. The effect of the groove and of the various combined bending-torsion loads on the S-N and Goodman diagrams are determined. Three design applications are presented. The third one illustrates the weight savings that may be achieved by designing for reliability.
Kececioglu, D.↗
Improved cryogenic shaft seals
Seals are designed for use with liquid propellant ball valves at temperatures ranging from -400 F to 130 F and 8,000 psig. Seals are capable of sustaining 90 degree rotation, with substantial amount of lateral and axial play, caused by large pressure loads and differential thermal contraction.
Gillon, W. A., Jr.↗
Cost saving synergistic shaft seal
Segmented carbon rings, used to replace elastomeric seal lip, provide resistance to high temperatures generated in lubricating film. Machining and close manufacturing tolerances of conventional segmented seal are avoided by mounting segmented rings in elastomeric flex section.
Ludwig, L. P.↗
Capacitive shaft-angle encoder
Economical device is less subject to wear than conventional resistive-potentiometer devices.
Hruby, R. J.↗
Endurance and failure characteristics of main-shaft jet engine bearings at 3x10 to the 6th power DN
Groups of thirty 120-mm bore angular contact ball bearings were endurance tested at a speed of 12,000 and 25,000 rpm and a thrust load of 66 721 N. The bearings were manufactured from a single heat of VIM-VAR AISI M-50 steel. At 1.44X1 million and 3.0x1 million DN, 84 483 and 74 800 bearing test hours were accumulated, respectively. Test results were compared with similar bearings made from CVM AISI M-50 steel run under the same conditions. Bearing lives at speeds of 3x1 million DN with the VIM-VAR AISI M-50 steel were nearly equivalent to those obtained at lower speeds. A combined processing and material life factor of 44 was found for VIM-VAR AISI M-50 steel. Continuous running after a spall has occurred at 3.0x1 million DN can result in a destructive fracture of the bearing inner race.
Bamberger, E. N.↗
Eliminate gas-entrained dirt from shaft seals
Technique using counter-pumping principle in conjunction with high centrifugal-force field to separate debris entrained in fluid.
Ludwig, L. P.↗
Analysis of regenerated single-shaft ceramic gas-turbine engines and resulting fuel economy in a compact car
Ranges in design and off-design operating conditions of an advanced gas turbine and their effects on fuel economy were analyzed. The assumed engine incorporated a single stage radial flow turbine and compressor with fixed geometry. Fuel economies were calculated over the composite driving cycle with gasoline as the fuel. At a constant turbine-inlet temperature, with a regenerator sized for a full power effectiveness the best fuel economies ranged from 11.1 to 10.2 km/liter (26.2 to 22.5 mpg) for full power turbine tip speeds of 770 to 488m/sec (2530 to 1600ft/sec), respectively.
Klann, J. L.↗
Small High-Speed Self-Acting Shaft Seals for Liquid Rocket Engines
Design analysis, fabrication, and experimental evaluation were performed on three self-acting facetype LOX seal designs and one circumferential-type helium deal design. The LOX seals featured Rayleigh step lift pad and spiral groove geometry for lift augmentation. Machined metal bellows and piston ring secondary seal designs were tested. The helium purge seal featured floating rings with Rayleigh step lift pads. The Rayleigh step pad piston ring and the spiral groove LOX seals were successfully tested for approximately 10 hours in liquid oxygen. The helium seal was successfully tested for 24 hours. The shrouded Rayleigh step hydrodynamic lift pad LOX seal is feasible for advanced, small, high-speed oxygen turbopumps.
Burcham, R. E.↗
Self-acting shaft seals
Self-acting seals are described in detail. The mathematical models for obtaining a seal force balance and the equilibrium operating film thickness are outlined. Particular attention is given to primary ring response (seal vibration) to rotating seat face runout. This response analysis reveals three different vibration models with secondary seal friction being an important parameter. Leakage flow inlet pressure drop and affects of axisymmetric sealing face deformations are discussed. Experimental data on self-acting face seals operating under simulated gas turbine conditions are given. Also a spiral groove seal design operated to 244 m/sec (800 ft/sec) is described.
Ludwig, L. P.↗
Liquid Rocket Engine Turbopump Rotating-shaft Seals
A monograph is organized and presents, for effective use in design, the significant experience and knowledge accumulated in development and operational programs to date. It reviews and assesses current practices, and from them establishes firm guidance for achieving greater consistency in design, increased reliability in the end product, and greater efficiency in the design effort. The monograph is divided into two major sections: state of the art and design criteria.
Burcham, R. E.↗