Engineering topics
Publications and source records attributed to Strom, T. N..
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.
A modified circumferential segmented ring seal was designed for direct replacement of a helicopter transmission elastomeric lip seal operating on a shaft diameter of 13.91 centimeters (5.481 in.) at sliding velocities to 52.48 m/sec (10 330 ft/min). The modifications involved the garter spring tension, shaft roundness, seal housing flatness, and pumping grooves to inhibit leakage. Operation of the seals in bench tests under simulated helicopter transmission conditions revealed that the seal leakage rate was within acceptable limits and that the wear rate was negligible. The low leakage and wear rates were confirmed in flight tests of 600 and 175 hours (sliding speed, 48.11 m/sec (9470 ft/min)). An additional 200 hours of air worthiness qualification testing (aircraft tie down) demonstrated that the seal can operate at the advanced sliding conditions of 52.48 m/sec (10 330 ft/min).
Comparative tests of modified and unmodified carbon ring seals showed that addition of helical grooves to conventional segmented carbon ring seals reduced leakage significantly. Modified seal was insensitive to shaft runout and to flooding by lubricant.
Mating flat surfaces inhibit leakage of a fluid around a stationary shaft. A spiral groove produces a pumping action toward the fluid when the shaft rotates. This prevents leakage while a generated hydraulic lifting force separates the mating surfaces to minimize wear. Provision is made for placing these spiral grooves in communication with the fluid to accelerate the generation of the hydraulic lifting force.
Operation under simulated aircraft transmission conditions of speeds to 2850 m/min (9350 ft/min), lubricant temperatures to 394 K (250 F), shaft radial runouts to 0.254 mm (0.010 in.) F.I.R. (full indicator reading), and pressure differentials to 1.03 N/cm2 (1.5 psi) revealed that conventional circumferential seals leaked excessively. Modifying the conventional seal by adding helical grooves to the seal bore reduced leakage rates to within the acceptable level of 10 cm3/hr. The leakage rate of this modified seal was not significantly affected by lubricant flooding or by shaft radial runout.
Torque and leakage rates of various lubricated lip seal designs at peripheral velocity of 120 feet per second
Mechanically simple, hermetically-sealed pump utilizes pumped fluid for lubrication. The rotor, having helical grooves on the outer surface, functions as both a bearing and pump.
Pump and seal parameters for helical groove, hermetically sealed pump and bearing rotor
Vibration of shaft face seals and stabilizing effect of viscous and friction damping
Rotating shaft seals used in space power systems have spiral grooves in one or both of the opposing seal faces. These grooves induce a pumping action which displaces the intervening fluid radially inward toward the shaft and counters the centrifugal forces which tend to displace the fluid outward.
Spiral groove face seals for improved sealing of liquid sodium flow
Conventional face contact seal performance improved by incorporating spiral groove geometry, discussing liquid sodium containment
Viscoseal operation in superlaminar flow regime noting pressure patterns, end effect, gas ingestion and sealing capacity
Wear and friction of impregnated mechanical carbons at high temperatures in air or nitrogen
Improved performance of face contact seal in liquid sodium by incorporation of spiral groove geometry
Viscoseal operation in superlaminar flow regime noting pressure patterns, end effect, gas ingestion and sealing capacity
Theoretical and experimental study of convective inertia and gas ingestion effects on flow regimes of viscoseal
Helical groove viscosity seal using sodium and water as sealed fluids