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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Application of an improved Nelson-Nguyen analysis to eccentric, arbitrary profile liquid annular seals

An improved dynamic analysis for liquid annular seals with arbitrary profile based on a method, first proposed by Nelson and Nguyen, is presented. An improved first order solution that incorporates a continuous interpolation of perturbed quantities in the circumferential direction, is presented. The original method uses an approximation scheme for circumferential gradients, based on Fast Fourier Transforms (FFT). A simpler scheme based on cubic splines is found to be computationally more efficient with better convergence at higher eccentricities. A new approach of computing dynamic coefficients based on external specified load is introduced. This improved analysis is extended to account for arbitrarily varying seal profile in both axial and circumferential directions. An example case of an elliptical seal with varying degrees of axial curvature is analyzed. A case study based on actual operating clearances of an interstage seal of the Space Shuttle Main Engine High Pressure Oxygen Turbopump is presented.

Padavala, Satyasrinivas↗
NASA NTRS1994

Relative performance comparison between baseline labyrinth and dual-brush compressor discharge seals in a T-700 engine test

In separate series of T-700 engine tests, direct comparisons were made between the forward-facing labyrinth and dual-brush compressor discharge seals. Compressor speeds to 43,000 rpm, surface speeds to 160 m/s (530 ft/s), pressures to 1 MPa (145 psi), and temperatures to 680 K (765 F) characterized these tests. The wear estimate for 40 hr of engine operations was less than 0.025 mm (0.001 in.) of the Haynes 25 alloy bristles running against a chromium-oxide-coated rub runner. The pressure drops were higher for the dual-brush than for the forward-facing labyrinth seal, implying better seal characteristics and engine performance for the brush seal. Modification of the secondary flow path requires that changes in cooling air and engine dynamics be accounted for.

Hendricks, Robert C.↗
NASA NTRS1994

Tribology and Microstructure of PS212 with a Cr2O3 Seal Coat

PS212 is a plasma sprayed metal bonding chrome carbide coating with solid lubricant additives which has lubricating properties at temperatures up to about 900 deg C. The coating is diamond ground to achieve an acceptable tribological surface. But, as with many plasma spray coatings, PS212 is not fully-dense. In this study, a chromium oxide base seal coating is used in an attempt to seal any porosity that is open to the surface of the PS212 coating, and to study the effect of the sealant on the tribological properties of PS212. The results indicate that the seal coating reduces friction and wear when it is applied and then diamond ground leaving a thin layer of seal coating which fills in the surface pits of the PS212 coating.

Sliney, Harold E.↗
NASA NTRS1995

Automatic Inspection Of Heat Seals Between Plastic Sheets

Automatic inspection apparatus detects flaws in heat seals between films of polyethylene or other thermoplastic material. Heat-sealed strip in multilayer plastic sheet continuously moved lengthwise over illuminators. Variations in light transmitted through sheet interpreted to find flaws in heat seal. Site of flaw marked to facilitate subsequent manual inspection. Heat sealing used to join plastic films in manufacturing of variety of products, including inflatable toys and balloons carrying scientific instruments to high altitudes.

Rai, Kula R.↗
NASA NTRS1996

Soft Wire Seals For High Temperatures And Pressures

Soft metal wires used to make O-ring and similar seals for vessels, flanges, and fittings subject to pressures equal to or greater than 1,000 psi and temperatures equal to or greater than 100 degrees C. Seals containing soft metal wires made inexpensively because fabricated to looser tolerances like those of lower-temperature, lower-pressure elastomeric-O-ring seals, which they resemble. Seals also made with noncircular grooves and with soft metals other than aluminum. For example, gold performs well, though expensive. For other applications, silver good choice.

Tsou, Peter↗
NASA NTRS1996

SCISEAL: A CFD Code for Analysis of Fluid Dynamic Forces in Seals

A 3D CFD code, SCISEAL, has been developed and validated. Its capabilities include cylindrical seals, and it is employed on labyrinth seals, rim seals, and disc cavities. State-of-the-art numerical methods include colocated grids, high-order differencing, and turbulence models which account for wall roughness. SCISEAL computes efficient solutions for complicated flow geometries and seal-specific capabilities (rotor loads, torques, etc.).

Althavale, Mahesh M.↗
NASA NTRS1996

Wall Shear Stress, Wall Pressure and Near Wall Velocity Field Relationships in a Whirling Annular Seal

The mean and phase averaged pressure and wall shear stress distributions were measured on the stator wall of a 50% eccentric annular seal which was whirling in a circular orbit at the same speed as the shaft rotation. The shear stresses were measured using flush mounted hot-film probes. Four different operating conditions were considered consisting of Reynolds numbers of 12,000 and 24,000 and Taylor numbers of 3,300 and 6,600. At each of the operating conditions the axial distribution (from Z/L = -0.2 to 1.2) of the mean pressure, shear stress magnitude, and shear stress direction on the stator wall were measured. Also measured were the phase averaged pressure and shear stress. These data were combined to calculate the force distributions along the seal length. Integration of the force distributions result in the net forces and moments generated by the pressure and shear stresses. The flow field inside the seal operating at a Reynolds number of 24,000 and a Taylor number of 6,600 has been measured using a 3-D laser Doppler anemometer system. Phase averaged wall pressure and wall shear stress are presented along with phase averaged mean velocity and turbulence kinetic energy distributions located 0.16c from the stator wall where c is the seal clearance. The relationships between the velocity, turbulence, wall pressure and wall shear stress are very complex and do not follow simple bulk flow predictions.

Morrison, Gerald L.↗
NASA NTRS1996

Resilient Braided Rope Seal

A resilient braided rope seal for use in high temperature applications. The resilient braided rope seal includes a center core of fibers, a resilient 5 member overbraided by at least one layer of braided sheath fibers tightly packed together. The resilient member adds significant stiffness to the seal while maintaining resiliency. Furthermore, the seal permanent set and hysteresis are greatly reduced. Finally, improved load capabilities are provided.

Steinetz, Bruce M.↗
NASA NTRS1997

Bidirectional Brush Seals

Presented is a study of the use of a set of I.D./O.D. bidirectional press seals to reduce the leakage losses in a wave rotor. Relative to the baseline configuration, data indicate the use of brush seals enhanced wave rotor efficiency from 36 to 45 percent at low leakages (small rotor endwall gap spacings) and from 15 to 33 percent at high leakages (larger endwall gap spacings). These brush seals are capable of sealing positive or negative pressure drops with respect to the axial direction. Surface tribology for these tests suggested little evidence of grooving although the bristles appeared polished.

Hendricks, Robert C.↗
NASA NTRS1997

Upstream Swirl Effects on the Flow Inside a Labyrinth Seal

The flow field inside a seven cavity tooth on rotor labyrinth seal was measured using a 3D laser Doppler anemometer system. The seal was operated at a Reynolds number of 24,000 and a Taylor number of 6,600 using water as the working fluid. Swirl vanes were placed upstream of the seal to produce positive, negative, and no preswirl. It was found that the axial and radial velocities were minimally effected. The tangential velocity, both in the clearance region and the seal cavities on the rotor, were greatly altered by the preswirl. By applying negative preswirl, the tangential velocity was suppressed, even in the seventh cavity. The turbulence levels decreased as the preswirl varied from negative to positive.

Morrison, Gerald L.↗
NASA NTRS1997

Seal Sample Fixtures

The development of the International Space Station is critically dependent upon development and testing of materials that will require exposure to the space environment. The seals between the modules are one of the more important examples. The choice of seals depends upon the seal materials' susceptibility to atomic oxygen, UV radiation, and the combined external space environment. Also, the choice of thermal control materials depends on their susceptibility to the space environment. The Space Environmental Branch at MSFC developed a flight experiment to provide information on the effects of the space environment on seal and thermal control materials. The experiment, called the Passive Optical Sample Array (POSA), involved exposing several different material samples to the atomic oxygen, UV radiation, and combined effects of the space environment. The POSA experiment is currently flying on the Russian Mir space station. It was necessary during the assembly of POSA to develop an understanding of available fabrication and metrology techniques in order to develop several monitoring systems for the experiment. The report briefly describes the tasks and the work performed in preparing the samples for the POSA experiment.

White, Edwin↗
NASA NTRS2001

High Temperature Performance Evaluation of a Compliant Foil Seal

The key points to be gleaned from the effort reported herein are that the CFS (Compliant Foil Seal) has been demonstrated in conjunction with a foil bearing in a small gas turbine simulator at temperatures as high as 1000 F and outperformed a comparable brush seal. Having demonstrated the feasibility of the CFS, it would appear that this new seal design has application potential in a wide range of machines. What remains is to demonstrate performance at higher pressure ratios, consistent performance at large rotor excursions and the ability to manufacture the seal in much larger sizes exceeding by an order of magnitude that which has been tested to date.

Salehi, Mohsen↗
NASA NTRS2001

NASA GRC Cryogenic Seal Test Rig Capability

It has been about six years since any cryogenic seal tests were run at NASA GRC (Glenn Research Center). The Cryogenic Components Lab, where the cryogenic seal test rigs are located, has been shutdown due to the impending expansion of the Cleveland Hopkins International Airport. The current plan is to move the Cryogenic Components Lab (CCL), Cells I and 2 to NASA Plumbrook in Sandusky, Ohio. The purpose of this presentation is to inform the seal community of the cryogenic seal test rig capabilities available at NASA GRC for planning of future programs.

Proctor, Margaret↗
NASA NTRS2002

Advanced High Temperature Structural Seals

This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

Newquist, Charles W.↗
NASA NTRS2003

A Brief Analysis of Capillary Sealing Methods and Their Effectiveness

Protein crystals and the solutions from which they are grown need to be carefully protected against dehydration. In absence of a proper seal, the crystals will dehydrate and lose their original properties, among these the ability to diffract X-rays. We conducted a systematic study of the efficacy of the most common sealing materials in use and we report the results here. The study shows that no single material is completely effective in both untreated and silanized glass capillaries. Various combinations of two materials, however, give excellent seals that will prevent dehydration for long periods of time. Recommendations are made for sealing materials to be used.

Curreri, Peter A.↗
NASA NTRS2003

Compliant Foil Seal Investigations

NASA Glenn Research Center has been working with Mohawk Innovative Technology, Inc. (MiTi) to develop a Compliant Foil Seal for use in gas turbine engines. MiTi was awarded phase I and phase II SBIR contracts to analyze, develop, and test foil seals. As part of the Phase II contract, MiTi delivered an 8.5 inch diameter foil seal to NASA GRC for testing. Today I will be presenting some results of testing the 8.5 inch foil seal at NASA.

Proctor, Margaret↗
NASA NTRS2004

Numerical, Analytical, Experimental Study of Fluid Dynamic Forces in Seals: Executive Summary and Description of Knowledge-Based System - Volume 1

The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allows the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.

Liang, Anita D.↗
NASA NTRS2004

Numerical, Analytical, Experimental Study of Fluid Dynamic Forces in Seals: Description of Spiral-Groove Codes SPIRALG and SPIRALI - Volume 3

The objectives of the program were to develop computational fluid dynamics (CFD) codes and simpler industrial codes for analyzing and designing advanced seals for air-breathing and space propulsion engines. The CFD code SCISEAL is capable of producing full three-dimensional flow field information for a variety of cylindrical configurations. An implicit multidomain capability allow the division of complex flow domains to allow optimum use of computational cells. SCISEAL also has the unique capability to produce cross-coupled stiffness and damping coefficients for rotordynamic computations. The industrial codes consist of a series of separate stand-alone modules designed for expeditious parametric analyses and optimization of a wide variety of cylindrical and face seals. Coupled through a Knowledge-Based System (KBS) that provides a user-friendly Graphical User Interface (GUI), the industrial codes are PC based using an OS/2 operating system. These codes were designed to treat film seals where a clearance exists between the rotating and stationary components. Leakage is inhibited by surface roughness, small but stiff clearance films, and viscous pumping devices. The codes have demonstrated to be a valuable resource for seal development of future air-breathing and space propulsion engines.

Liang, Anita D.↗