Nonelastomeric Rod Seals for Advanced Hydraulic Systems

Advanced high temperature hydraulic system rod sealing requirements can be met by using seals made of nonelastomeric (plastic) materials in applications where elastomers do not have adequate life. Exploratory seal designs were optimized for advanced applications using machinable polyimide materials. These seals demonstrated equivalent flight hour lives of 12,500 at 350 F and 9,875 at 400 F in advanced hydraulic system simulation. Successful operation was also attained under simulated space shuttle applications; 96 reentry thermal cycles and 1,438 hours of vacuum storage. Tests of less expensive molded plastic seals indicated a need for improved materials to provide equivalent performance to the machined seals

High speed, self-acting shaft seal

A high-speed, self-acting circumferential type shaft seal for use in turbine engines is disclosed. One or more conventional circumferential ring seals having a central aperture are mounted in a housing. In three of the four embodiments of the invention, a helical groove and one or more dam seals are cut in the inner cylindrical surface of the one or more ring seals. In a fourth embodiment, two or more lift pads are disposed in surface contact with the inner cylindrical surface of the seal rings. To the outside of the lift pads, two dam seals are cut in the inner cylindrical surface of two of the ring seals. In each of the embodiments, a net outward radial force was produced during rotation of the turbine causing the ring seals to lift out of contact with the turbine shaft to minimize wear of the ring seals

Tribological properties of graphite-fiber-reinforced, partially fluorinated polyimide composites

Graphite-fiber-reinforced polyimide (GFRPI) composites were formulated from three new partially fluorinated polyimides and three types of graphite fiber. Nine composites were molded into pins and evaluated in a pin-on-disk tribometer. Friction coefficients, wear rates, pin wear surface morphology, and transfer film formation were assessed at 25 and 300 C. Also assessed was the effect of sliding speed on friction. Wear was up to two orders of magnitude lower at 25 C and up to one order of magnitude lower at 300 C than with previously formulated NASA GFRPI composites

New circumferential seal design concept using self-acting lift geometries

Seal operating temperatures, leakage (pressurizing gas flow), torque, and wear of a conventional circumferential shaft seal were measured and compared to those of a conventional seal modified to have self-acting lift geometries. Both seal types had a 2.625-in diameter bore and were operated at a sliding velocity of 150 ft/sec with differential pressures ranging from 0 to 100 psi. Results of this investigation show that the self-acting seal operated at lower bulk carbon temperatures with half the torque and approximately one-tenth the wear of the conventional seal. Seal leakage of the self-acting seal was of order of 0.04 scfm for pressures above 60 psi which is well within the accepted range for gas turbine engine applications

Effect of sterilization irradiation on friction and wear of ultrahigh-molecular-weight polyethylene

The effect of sterilization gamma irradiation on the friction and wear properties of ultrahigh molecular weight polyethylene (UHMWPE) sliding against 316L stainless steel in dry air at 23 C was determined. A pin-on-disk apparatus was used. Experimental conditions included a 1-kilogram load, a 0.061- to 0.27-meter-per-second sliding velocity, and a 32000- to 578000-meter sliding distance. Although sterilization doses of 2.5 and 5.0 megarads greatly altered the average molecular weight and the molecular weight distribution, the friction and wear properties of the polymer were not significantly changed

Compressible flow across narrow passages: Comparison of theory and experiment for face seals

Computer calculation for determining compressible flow across radial face seals were compared with measured results obtained in a seal simulator rig at pressure ratios to 0.9 (ambient pressure/sealed pressure). In general, the measured and calculated leakages across the seal dam agreed within 3 percent. The resultant loss coefficient, dependent upon the pressure ratio, ranged from 0.47 to 0.68. The calculated pressures were within 2.5 N/cu um of the measured values

An overview of the NASA rotary engine research program

A brief overview and technical highlights of the research efforts and studies on rotary engines over the last several years at the NASA Lewis Research Center are presented. The test results obtained from turbocharged rotary engines and preliminary results from a high performance single rotor engine were discussed. Combustion modeling studies of the rotary engine and the use of a Laser Doppler Velocimeter to confirm the studies were examined. An in-house program in which a turbocharged rotary engine was installed in a Cessna Skymaster for ground test studies was reviewed. Details are presented on single rotor stratified charge rotary engine research efforts, both in-house and on contract

Biomass from Paddy Waste Fibers as Sustainable Acoustic Material

Utilization of biomass for green products is still progressing in the efort to provide alternative clean technology.his paper presents the utilization of natural waste ibers frompaddy as acousticmaterial. Samples of sound absorbingmaterial frompaddy waste ibers were fabricated.he efect of the iber density, that is, the iber weight and the sample thickness, and also the air gap on the sound absorption coeicient is investigated through experiment. he paddy ibers are found to have good acoustic performance with normal incidence absorption coeicient greater than 0.5 from 1 kHz and can reach the average value of 0.8 above 2.5 kHz. his result is comparable against that of the commercial synthetic glass wool. Attachment of a single layer of polyester fabric is shown to further increase the absorption coeicient

Effect of vitamin B17 on experimentally induced colon cancer in adult male albino rat

Background: Colon cancer is considered to be the third most common cancer worldwide. At diagnosis of colon cancer, 3.7–11% developed bone metastasis. Diet based strategies are important for prevention and treatment of colon cancer. This study investigated the effect of vitamin B17 on a DMH induced rat model of colon cancer. Materials and methods: Eighty young adult male albino rats were divided into five groups: group I (control group), group II (vitamin B17), group III (colon cancer), group IV (protected) and group V (treated). Distal colon sections were prepared for light and scanning electron microscopic examination. Lumbar vertebrae specimens were prepared for light microscopic study. Morphometric and statistical analysis were done. Results: In comparison with the control, both colon cancer and treated groups showed invasion of the colonic tissue by pleomorphic branching colonic glands of variable shapes and sizes lined with dysplastic elongated hyperchromatic nuclei with frequent mitotic figures or stratified multi-layered crowded nuclei with an extremely significant (p < 0.0001) reduction of goblet cell number when compared to the control together with major pathological bone changes were observed in colon cancer and the treated groups. Conclusions: While the protected group showed impressive improvement of all previously mentioned diameters