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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The SSME seal test program: Leakage tests for helically-grooved seals

Helically grooved annular seal configurations were tested in highly turbulent flow to determine if reduced leakage and enhanced stability would result from the pumping action of the seal. It was found that: (1) leakage of a helically grooved seals decreases with running speed; (2) leakage reduction due to increased running speed is greater at lower values of R sub a; (3) an asymptote for leakage reduction is indicated with increasing running speed; (4) leakage is reduced by reducing the ridge (minimum) and average clearances; (5) leakage increases with increasing pitch angles and with increasing groove depth. Plain seals with smooth rotors and stators will leak more than a helically grooved seal. It was also found that plain seals with a rough rotor and a rough stator leak less than a properly designed helically grooved seal. A properly designed helically grooved seal consumes at least twice as much power as a conventional annular seal.

Childs, D. W.↗
NASA NTRS1996

High temperature braided rope seals for static sealing applications

Achieving efficiency and performance goals of advanced aircraft and industrial systems are leading designers to implement high temperature materials such as ceramics and intermetallics. Generally these advanced materials are applied selectively in the highest temperature sections of the engine system including the combustor and high pressure turbine, amongst others. Thermal strains that result in attaching the low expansion-rate components to high expansion rate superalloy structures can cause significant life reduction in the components. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Designers require high temperature, low-leakage, compliant seals to mitigate thermal stresses and control parasitic and cooling airflow between structures. NASA is developing high temperature braided rope seals in a variety of configurations to help solve these problems. This paper will describe the types of seals being developed, describe unique test techniques used to assess seal performance, and present leakage flow data under representative pressure, temperature and scrubbing conditions. Feasibility of the braided rope seals for both an industrial tube seal and a turbine vane seal application is also demonstrated.

Adams, Michael L.↗
NASA NTRS1993

A hot dynamic seal rig for measuring hypersonic engine seal durability and flow performance

A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts has been installed at NASA Lewis Research Center. The test fixture has been designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (NASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840 C (1550 F) and air pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. This report covers the capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling.

Miller, Jeffrey H.↗
NASA NTRS1993

A Hot Dynamic Seal Rig for Measuring Hypersonic Engine Seal Durability and Flow Performance

A test fixture for measuring the dynamic performance of candidate high-temperature engine seal concepts was installed at NASA Lewis Research Center. The test fixture was designed to evaluate seal concepts under development for advanced hypersonic engines, such as those being considered for the National Aerospace Plane (NASP). The fixture can measure dynamic seal leakage performance from room temperature up to 840 C (1550 F) and air pressure differentials up to 690 kPa (100 psi). Performance of the seals can be measured while sealing against flat or distorted walls. In the fixture two seals are preloaded against the sides of a 30 cm (1 ft) long saber that slides transverse to the axis of the seals, simulating the scrubbing motion anticipated in these engines. The capabilities of this test fixture along with preliminary data showing the dependence of seal leakage performance on high temperature cycling are addressed.

Miller, Jeffrey H.↗
NASA NTRS2011

Modifications to Marshall's Annular Seal Test (MAST) Rig and Facility for Improved Rotordynamic Coefficient Testing of Annular Seals and Fluid Film Bearings

The limits of rotordynamic stability continue to be pushed by the high power densities and rotational speeds of modern rocket engine turbomachinery. Destabilizing forces increase dramatically with rotor speed. Rotordynamic stability is lost when these destabilizing forces overwhelm the stabilizing forces. The vibration from the unstable rotor grows until it is limited by some nonlinearity. For example, a rolling element bearing with a stiffness characteristic that increases with deflection may limit the vibration amplitude. The loads and deflections resulting from this limit cycle vibration (LCV) can lead to bearing and seal damage which promotes ever increasing levels of subsynchronous vibration. Engineers combat LCV by introducing rotordynamic elements that generate increased stabilizing forces and reduced destabilizing forces. For example, replacing a labyrinth seal with a damping seal results in substantial increases in the damping and stiffness rotordynamic coefficients. Adding a swirl brake to the damping seal greatly reduces the destabilizing cross-coupled forces generated by the damping seal for even further increases in the stabilizing capacity. Marshall?s Annular Seal Test (MAST) rig is designed to experimentally measure the stabilizing capacity of new annular seal designs. The rig has been moved to a new facility and outfitted with a new slave bearing to allow increased test durations and to enable the testing of fluid film bearings. The purpose of this paper is to describe the new facility and the new bearing arrangement. Several novel seal and bearing designs will also be discussed.

Darden, J. M.↗
DOE OSTI2015

Outcomes of the full scale seal experiment: a seal industrial prototype for the Cigeo project - 15207

The Full Scale Seal (FSS) Experiment is one of various experiments implemented by Andra, within the frame of the French HLW and IL-LLW Deep Geological Repository Project (aka Cigeo) development, to demonstrate the technical feasibility and check the performance of the seals which will be constructed in the shafts, ramps, drifts and disposal vaults, at time of Cigeo underground facilities progressive closure. The FSS experimental objectives, principles and rationale were presented at WM'2013 (Paper 1306): FSS is a technological demonstrator built on surface, inside a concrete made horizontal drift model (also called the 'test box'). FSS is part of the European DOPAS (Demonstration of Plugs and Seals) [2] project, under the umbrella of the Implementing Geological Disposal - Technology Platform (IGD-TP) [3] project. FSS construction activities started in July 2012 and were completed in September 2014. The construction compliance assessment work activities are now ongoing (and will be continued until mid-2015). This paper presents the construction and monitoring story of the FSS components, starting with the construction of a first containment wall based on a low pH self-compacting concrete (SCC), followed by the swelling clay core backfilling sequence and finishing with the erection of a second containment wall based on a low pH shotcrete. The FSS experiment also enabled to qualify the commissioning methods applicable to an industrial sealing work at time of underground operations in the Repository. These commissioning methods are described and the results discussed. The equipment and methods used for the purpose of seal component construction and monitoring are presented. The physical characteristics obtained for each component of the seal are detailed and the compliance of measured values with the initial requirements is commented. The post-mortem work planned (e.g. coring and wire sawing of low pH concrete containment walls, use of penetrometer for the swelling clay core...) is also explained. FSS is a first of a kind experiment, by its size, by the technical choices made. The first technical outcomes were presented to the French Nuclear Authority and to its Technical Support Organization. The successful implementation of the work carried out in the FSS drift model was positively assessed by the evaluators and deemed representative of the real underground conditions (industrial feasibility is proven). This article concludes with a critical analysis of the methods and equipment used, of the results obtained and provides some perspectives of improvement for the construction of the first Cigeo industrial prototype seals scheduled around 2030 in ramps and horizontal drifts (provided the Cigeo construction is authorized in late 2020, and following the licensing request filing scheduled in late 2017). (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
NASA NTRS1986

SSME Seal Test Program: Test results for sawtooth pattern damper seal

Direct and transverse force coefficients for 11, sawtooth-pattern, and damper-seal configurations were examined. The designation damper seal uses a deliberately roughened stator and smooth rotor to increase the net damping force developed by a seal. The designation sawtooth-pattern refers to a stator roughness pattern. The sawtooth pattern yields axial grooves in the stator which are interrupted by spacer elements which act as flow constrictions or dams. All seals use the same smooth rotor and have the same, constant, minimum clearance. The stators examined the consequences of changes in the following design parameters: (1) axial-groove depth; (2) number of teeth: (3) number of sawtooth sections; (4) number of spacer elements; (5) dam width; (6) axially aligned sawtooth sections versus axially-staggered sawtooth sections; and (7) groove geometry. It is found that none of the sawtooth-pattern seal performs as well as the best round-hole-pattern seal. Maximum damping configurations for the sawtooth and round-hole-pattern stators have comparable stiffness performance. Several of the sawtooth pattern stators outperformed the best round-hole pattern seal.

Childs, D. W.↗
NASA NTRS1989

Experimental results for labyrinth gas seals with honeycomb stators - Comparisons to smooth-stator seals and theoretical predictions

Experimental measurements are presented for the rotordynamic stiffness and damping coefficients of a teeth-on-rotor labyrinth seal with a honeycomb stator. Inlet circumferential velocity, inlet pressure, rotor speed, and seal clearance are primary variables. Results are compared to data for teeth-on-rotor labyrinth seals with smooth stators and to analytical predictions from a two-control-volume compressible flow model. The experimental results show that the honeycomb-stator configuration is more stable than the smooth-stator configuration at low rator speeds. At high rotor speeds, the stator surface does not affect stability. The theoretical model predicts the cross-coupled stiffness of the honeycomb-stator seal correctly within 25 percent of measured values. The model provides accurate predictions of direct damping for large clearance seals; however, the model predictions and test results diverge with increasing running speed. Overall, the model does not perform as well for low clearance seals as for high clearance seals.

Hawkins, Larry↗
NASA NTRSDate not supplied

Lunar Dust Tolerance Testing of Representative Seals for Lunar Surface Hatch Seals

The Moon’s surface creates a uniquely challenging environment for mechanisms and materials. Electrostatic adhesion combined with a jagged particulate morphology makes lunar dust particularly destructive to the components and sub-systems of lunar surface assets. One component that will be acutely impacted by lunar dust is seals, particularly those on the hatches which will be opened and closed to allow extravehicular activities (EVA) and on docking systems that will connect surface assets and spacecraft together. Lunar dust on these seals can create leak paths for the pressurized atmosphere of a surface asset to escape. Quantifying the level of lunar dust contamination that is allowable for seals is of paramount importance for mission planners and asset designers. This paper covers dust tolerance testing that was conducted on representative hatch seals with the Uniform Dust Deposition System (UDDS) at NASA Glenn Research Center [1]. Sub scale (≈30 cm diameter) versions of seals for the Orion docking hatch and NASA Docking System (NDS were coated evenly with varying amounts of lunar dust simulant to evaluate its effect on seals leak rates. The resulting leak rate results from these flight-proven seal design can help planners and designers construct robust missions and products

N. Jimenez↗
DOE OSTI2016

Sealing device for providing a seal in a turbomachine

Sealing device for providing seals between adjacent components, and turbomachines utilizing such sealing devices, are provided. A sealing device includes a seal plate insertable between the adjacent components, the seal plate comprising a first face and an opposing second face. The sealing device further includes a plurality of pins extending from one of the first face or the second face, the plurality of pins configured to space the one of the first face or the second face from contact surfaces of the adjacent components.

42 ENGINEERING↗
DOE OSTI2014

Method of sealing a bipolar plate supported solid oxide fuel cell with a sealed anode compartment

Methods of sealing a bipolar plate supported solid oxide fuel cell with a sealed anode compartment are provided. The solid oxide fuel cell includes a cathode, an electrolyte, and an anode, which are supported on a metallic bipolar plate assembly including gas flow fields and the gas impermeable bipolar plate. The electrolyte and anode are sealed into an anode compartment with a metal perimeter seal. An improved method of sealing is provided by extending the metal seal around the entire perimeter of the cell between an electrolyte and the bipolar plate to form the anode compartment. During a single-step high temperature sintering process the metal seal bonds to the edges of the electrolyte and anode layers, the metal foam flow field and the bipolar plate to form a gastight containment.

25 ENERGY STORAGE↗
NASA NTRS1978

Development of low cost, high reliability sealing techniques for hybrid microcircuit packages. Phase 2, supplement 1: Moisture permeation of adhesive-sealed hybrid microcircuit packages

The susceptibility of adhesive-sealed ceramic packages to moisture permeation was investigated. The two adhesives, Ablebond 789-1 and Epo-Tek H77, were evaluated as package sealants. These adhesives were previously selected as the most promising candidates for this application from a group of ten adhesives. Ceramic packages sealed with these adhesives were exposed to temperature-humidity conditions of 25 C/98 percent RH, 50 C/60 percent RH, 50 C/98 percent RH, and 85 C/85 percent RH and their moisture contents using were monitored solid state moisture sensors sealed inside them. Five packages were tested at each of these exposures - two ceramic packages sealed with each of the two adhesives and one seam-sealed gold-plated Kovar package. This latter package was included to serve as a control. The results showed that the adhesive-sealed packages were not hermetic to moisture. The rates at which moisture entered the packages increased with the severity of the exposure environments (i.e., higher temperatures and higher moisture vapor pressures) with greater dependence on temperature than on moisture vapor pressure.

Perkins, K. L.↗
NASA NTRS1978

The accuracy of the narrow seal approximation in analyzing radial face seals

The accuracy of the narrow seal approximation which enables closed form analytical solutions for radial face seals is examined in this paper. Both hydrostatic and hydrodynamic effects in a flat, misaligned seal are considered. Analytical results obtained from a simplified Reynolds equation, based on the neglect of circumferential pressure gradient and seal curvature, are compared with accurate results from numerical solution of the complete Reynolds equation. The agreement between the approximate and accurate solutions is quite reasonable over a wide range of a seal's inner-to-outer radius ratio. For radius ratios greater than 0.8, the accuracy of the narrow seal approximation is better than 1 percent over most of the range of angular misalignment.

Etsion, I.↗
NASA NTRS1985

SSME seal test program: Test results for hole-pattern damper seals

The results consisting of direct and transverse force coefficients are presented for thirteen, hole-pattern, damper-seal configurations. The designation damper seal refers to a seal which uses a deliberately roughened stator nd smooth rotor, to increase the net damping force developed by a seal. The designation hole-pattern refers to a stator roughness pattern which is developed by a pattern of round holes while are milled into the stator. All seals tested use the same smooth rotor and have the same constant minimum clearance. The seal tests examined the following major design options: (1) hole-area density, i.e., the proportion of stator surface area consumed by holes; and (2) hole depth, particularly the ratio of hole depth to minimum clearance. In addition, limited data were taken to examine the influence of in-line versus staggered hole patterns and flat-bottomed versus spherical-bottomed holes.

Childs, D. W.↗
NASA NTRS1987

Rotordynamic coefficients and leakage flow of parallel grooved seals and smooth seals

Based on Childs finite length solution for annular plain seals an extension of the bulk flow theory is derived to calculate the rotordynamic coefficients and the leakage flow of seals with parallel grooves in the stator. Hirs turbulent lubricant equations are modified to account for the different friction factors in circumferential and axial direction. Furthermore an average groove depth is introduced to consider the additional circumferential flow in the grooves. Theoretical and experimental results are compared for the smooth constant clearance seal and the corresponding seal with parallel grooves. Compared to the smooth seal the direct and cross-coupled stiffness coefficients as well as the direct damping coefficients are lower in the grooved seal configuration. Leakage is reduced by the grooving pattern.

Nordmann, R.↗
DOE OSTI2013

The Full Scale Seal Experiment - A Seal Industrial Prototype for Cigeo - 13106

The Full Scale Seal (FSS) Experiment is one of various experiments implemented by Andra, within the frame of the Cigeo (the French Deep Geological Repository) Project development, to demonstrate the technical construction feasibility and performance of seals to be constructed, at time of Repository components (shafts, ramps, drifts, disposal vaults) progressive closure. FSS is built inside a drift model fabricated on surface for the purpose. Prior to the scale 1:1 seal construction test, various design tasks are scheduled. They include the engineering work on the drift model to make it fit with the experimental needs, on the various work sequences anticipated for the swelling clay core emplacement and the concrete containment plugs construction, on the specialized handling tools (and installation equipment) manufactured and delivered for the purpose, and of course on the various swelling clay materials and low pH (below 11) concrete formulations developed for the application. The engineering of the 'seal-as-built' commissioning means (tools and methodology) must also be dealt with. The FSS construction experiment is a technological demonstrator, thus it is not focused on the phenomenological survey (and by consequence, on the performance and behaviour forecast). As such, no hydration (forced or natural) is planned. However, the FSS implementation (in particular via the construction and commissioning activities carried out) is a key milestone in view of comforting phenomenological extrapolation in time and scale. The FSS experiment also allows for qualifying the commissioning methods of a real sealing system in the Repository, as built, at time of industrial operations. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2017

Sealing glass-ceramics with near-linear thermal strain, part III: Stress modeling of strain and strain rate matched glass-ceramic to metal seals

Thermal mechanical stresses of glass-ceramic to stainless steel (GCtSS) seals are analyzed using finite element modeling over a temperature cycle from a set temperature (T set ) 500°C to -55°C, and then back to 600°C. There are two glass-ceramics that have an identical coefficient of thermal expansion (CTE) at ~16 ppm/°C but have very different linearity of thermal strains, designated as near-linear NL16 and step-like SL16, and were formed from the same parent glass using different crystallization processes. Stress modeling reveals much higher plastic strain in the stainless steel using SL16 glass-ceramic when the GCtSS seal cools from T set . Upon heating tensile stresses start to develop at the GC-SS interface before the temperature reaches T set . On the other hand, the much lower plastic deformation in stainless steel accumulated during cooling using NL16 glass-ceramic allows for radially compressive stress at the GC-SS interface to remain present when the seal is heated back to T set . Finally, the qualitative stress comparison suggests that with a better match of thermal strain rate to that of stainless steel, the NL16 glass-ceramic not only improves the hermeticity of the GCtSS seals, but would also improve the reliability of the seals exposed to high-temperature and/or high-pressure abnormal environments.

36 MATERIALS SCIENCE↗