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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Investigation of Lubricant Additive Interactions on Gasoline Particulate Filters

To understand how the composition of novel lubricant additives and their ash interact with gasoline particulate filters (GPFs), an accelerated aging protocol was conducted using three lubricant additive formulations and two GPF types. The additive packages (adpaks) consisted of Ca+Mg detergent in a 3:1 or 0:1 ratio and an anti-wear component—either zinc dialkyl dithiophosphate (ZDDP) or a novel phosphonium-phosphinate ionic liquid (IL) substitute. The particulate sampling captured amount/compositions of particulate matter (PM) generated, total particulate number, and size distribution. Five ash loadings were completed. GPF position and adpak composition affected the backpressure, ash composition, ash morphology, and captured mass. The particulate sampling indicated that the ash component consisted primarily of particles less than 50 nm in size and that the Mg-only adpak resulted in more particulate of 50–400 nm in size. Postmortem materials characterization indicated GPFs in the underfloor position had deeper penetration of ash into the walls compared to the close-coupled position. Additionally, the Mg-only adpak had a higher filter collection efficiency (>90%) and the ash particles consisted of a higher concentration of dense ash material. In contrast, four of the 3:1 Ca:Mg lubricant adpaks resulted in a collection efficiency of only 40–50%. Although the collection efficiency was higher with the Mg-only adpak, the ash layer in the GPF was not thicker, nor was the penetration into the wall more significant, and surprisingly the full useful life (FUL) backpressure was lower than with Ca:Mg adpaks. The higher density of the Mg-derived ash was the only detectable difference. A possible explanation of this observation is that Mg ash has a lower melting point and is more susceptible to densification during combustion or GPF regeneration. The substitution of IL in place of the ZDDP did not lead to any notable changes in collection efficiency or location of the ash.

42 ENGINEERING↗
DOE OSTI2020

Competitive Adsorption of Lubricant Base Oil and Ionic Liquid Additives at Air/Liquid and Solid/Liquid Interfaces

Oil-soluble ionic liquids (ILs) have been proved as effective additives in lubricant oils through tribological experiments and post-test analytical analyses. Here, surface structures of lubricant base oil, oil-soluble ILs, and their mixtures at the air/liquid and solid/liquid interfaces have been studied using sum frequency generation (SFG) vibrational spectroscopy. At the air/base oil and air/IL interfaces, the alkyl chains of the studied compounds were shown to be conformationally disordered and their terminal methyl groups point outward at the liquid surface. The base oil dominates the air/(base oil + IL) interface due to its higher surface excess propensity and larger bulk concentration. At the solid (silica) surface, ILs adopt a structure with their charged headgroups in contact with the silica surface, while their alkyl chains are more conformationally ordered or packed compared to the air/IL interface. At the interface between silica and (base oil + IL) mixtures, ILs also preferentially adsorb to the silica surface with their layer structures somewhat different from those of ILs alone. These results showed that ILs can adsorb onto the solid surface even before tribological contacts are made. The insights obtained from this SFG study provide a better understanding of the role of ionic liquids in lubrication.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1968

Bearings use dry self-lubricating cage materials

Rolling element bearings in spacecraft mechanical systems use solid lubricant composites of polytetrafluoroethylene in the bearing cage which functions as the lubricant reservoir. The cage spaces the rolling elements equally and provides the lubricant at the bearing load-carrying surface.

Anderson, W. J.↗
NASA NTRS1970

Liquid cryogenic lubricant

Fluorinated polyethers are suitable lubricants for rolling-element bearings in cryogenic systems. Lubrication effectiveness is comparable to that of super-refined mineral oil lubricants operating at room temperature.

Dietrich, M. W.↗
NASA NTRS1971

Applications of aerospace technology in industry, a technology transfer profile: Lubrication

Technology transfer in the lubrication field is discussed in terms of the movement of NASA-generated lubrication technology into the private sector as affected by evolving industrial requirements. An overview of the field is presented, and NASA technical contributions to lubrication technology are described. Specific examples in which these technologies have been used in the private sector are summarized.

Kottenstette, J. P.↗
NASA NTRS1972

Comparative lubrication studies of OH-58A tail rotor drive shaft bearings

Comparative lubrication tests were run with OH-58A helicopter tail rotor drive shaft bearings. The tests were run in an outdoor environment with ambient temperatures ranging from 10 to 75 F. Dust was periodically applied to the bearings to simulate field conditions. The cause of bearing failure was associated with dust penetration. Rotor shaft failure was found to be caused by the shaft rotating in the standard rubber collar due to seizure of the bearings. Bearings with a positive rubbing seal having a MIL-G-81322 grease produced lives greater than with bearings having labyrinth seals and a mineral oil paste lubricant. An elongated collar prevented failure of the rotor shaft during bearing seizure. In a limited test, installation of tail boom shrouds over the bearings which excluded dust and water resulted in bearing lives in excess of 1800 hours or 1200 hours greater than the current 600 hours TBO, regardless of the lubricant-bearing combination used.

Dietrich, M. W.↗
NASA NTRS1973

Lubrication handbook

Information on lubricants from government reports, military specifications, qualified parts lists, and suppliers of commercial lubricants has been consolidated in one source. Handbook includes data on chemical and physical properties of solid, bonded solid, and liquid lubricants; dispersions and composites; and greases, oils, and hydraulic fluids.

Campbell, M. E.↗
NASA NTRS1972

Development and characterization of lubricants for use near nuclear reactors in space vehicles

The synthesis and evaluation program was conducted to develop wide-temperature range lubricants suitable for use in space vehicles particularly in the vicinity of nuclear reactors. Synthetic approaches resulted in nonpolymeric, large molecular weight materials, all based on some combination of siloxane and aromatic groups. Evaluation of these materials indicated that certain tetramethyl and hexamethyl disiloxanes containing phenyl thiophenyl substituents are extremely promising with respect to radiation stability, wide temperature range, good lubricity, oxidation resistance and additive acceptance. The synthesis of fluids is discussed, and the equipment and methods used in evaluation are described, some of which were designed to evaluate micro-quantities of the synthesized lubricants.

Robinson, G. L.↗
NASA NTRS1973

Parametric study of the lubrication of thrust loaded 120-mm bore ball bearings to 3 million DN

A parametric study was performed with 120-mm bore angular-contact ball bearings under varying thrust loads, bearing and lubricant temperatures, and cooling and lubricant flow rates. Contact angles were nominally 20 and 24 deg with bearing speeds to 3 million DN. Endurance tests were run at 3 million DN and a temperature of 492 K (425 F) with 10 bearings having a nominal 24 deg contact angle at a thrust load of 22241 N (5000 lb). Bearing operating temperature, differences in temperatures between the inner and outer races, and bearing power consumption can be tuned to any desirable operating requirement by varying 4 parameters. These parameters are outer-race cooling, inner-race cooling, lubricant flow to the inner race, and oil inlet temperature. Preliminary endurance tests at 3 million DN and 492 K (425 F) indicate that long term bearing operation can be achieved with a high degree of reliability.

Signer, H.↗
NASA NTRS1972

The evaporation of various lubricant fluids in vacuum.

The weight-loss rate in vacuum of 18 lubricating liquids and greases is reported for temperatures up to 120 C. Eleven types of 'medium-viscosity' (20 to 52 centistokes at 40 C) fluids were studied. In addition, a variety of perfluoro ether liquids having viscosities of 350 to 500 centistokes at 40 C were investigated, as were some commercial greases based on these liquids. The results showed that a methylchlorophenyl silicone, a high-viscosity-index perfluoro ether research fluid, and a polyoctene have suitably low outgassing properties for long-term space applicaitons requiring a medium-viscosity lubricant. Perfluoro ether greases also displayed low outgassing, but batch-to-batch variation was great. Mass spectrometer measurements indicated that the outgassed species were characterized by much lower molecular weights than that expected for the liquids. This suggests that lubricant transfer techniques which rely on evaporation from a reservoir may not be desirable for long-term space applications.

Hamilton, D. B.↗
NASA NTRS1973

Environmental Capability of Liquid Lubricants

The methods available for predicting the properties of liquid lubricants from their structural formulas are discussed. The methods make it possible to design lubricants by forecasting the results of changing the structure and to determine the limits to which liquid lubricants can cope with environmental extremes. The methods are arranged in order of their thermodynamic properties through empirical physical properties to chemical properties.

Beerbower, A.↗
NASA NTRS1973

Development of special lubricants for ball bearings operating in vacuum

A ball bearing life test program was performed to obtain data on the efficiencies of various lubricated and self-lubricating ball retainer systems for instrument bearings in a vacuum environment. The program utilized light to moderate radial loads at relatively low speeds on a NASA-GSFC designed and supplied test rig. Several systems were found which gave acceptable bearing life under the test conditions used, but the most consistent low running torques after testing resulted from oil lubrication.

Source record↗
NASA NTRS1975

Effect of viscosity on rolling-element fatigue life at cryogenic temperature with fluorinated ether lubricants

Rolling-element fatigue tests were conducted with 12.7-mm-(1/2-in.-) diameter AISI 52100 steel balls in the NASA five-ball fatigue tester, with a maximum hertz stress of 5500 mN/m2 (800 000 psi), a shaft speed of 4750 rpm, lubricant temperature of 200 K (360 R), a contact angle of 20 deg, using four fluorinated ether lubricants of varying viscosities. No statistically significant differences in rolling-element fatigue life occurred using the four viscosity levels. Elastohydrodynamic calculations indicate that values of the lubricant film parameter were approximately 2 or greater.

Dietrich, M. W.↗
NASA NTRS1974

Study of lubricant jet flow phenomena in spur gears

Review of the results of lubrication tests conducted in the NASA-Lewis Research Center gear test apparatus modified for high speed photography of gear tooth lubrication. The experimental results are compared with an analytical model that includes windage effects. The resulting findings show that the analytical model provides good agreement with the experimental impingement depth and that small oil drops are affected by gear windage. For this reason, the best lubrication is provided when the oil jet is not atomized.

Akin, L. S.↗
NASA NTRS1976

Transient effect of lubricant on elastohydro-dynamic film thickness

The inlet solution of the elastohydrodynamic lubricated rolling contact problem was obtained by considering lubricants with transient viscosity. The effect of the viscoelastic retardation time of the lubricant on the center film thickness was investigated. The effect of transient viscosity in response to a sudden pressure was found to be insignificant in determining the film thickness in elastohydrodynamic contacts.

Wang, K. L.↗
NASA NTRS1976

An evaluation of grease ball bearing lubricants in vacuum

Because many future spacecraft will require mechanisms to operate for long periods of time in environments which are inimical to most bearing lubricants, a series of tests has been started to evaluate 25 grease type lubricants in R-4 size bearings in vacuum at ambient temperature for a 1 year period. Four repetitions of each test are made to provide statistical samples. These tests will be used to select from two to five lubricants for 5 year tests in the same environment. At the present time fifteen test sets have been completed and five sets are being tested. The best results to date have been obtained with perfluoropolyether greases.

Demorest, K. E.↗
NASA NTRS1976

Dynamics of solid lubrication as observed by optical microscopy

A bench metallograph was converted into a micro contact imager by the addition of a tribometer employing a steel ball in sliding contact with a glass disk. The sliding contact was viewed in real time by means of projection microscope optics. The dynamics of abrasive particles and of solid lubricant particles within the contact were observed in detail. The contact was characterized by a constantly changing pattern of elastic strain with the passage of surface discontinuities and solid particles. Abrasive particles fragmented upon entering the contact, embedded in one surface and scratched the other; in contrast, the solid lubricant particles flowed plastically into thin films. The rheological behavior of the lubricating solids gave every appearance of a paste-like consistency within the Hertzian contact.

Sliney, H. E.↗