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At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Thermal barrier coatings application in diesel engines

Commercial use of thermal barrier coatings in diesel engines began in the mid 70's by Dr. Ingard Kvernes at the Central Institute for Industrial Research in Oslo, Norway. Dr. Kvernes attributed attack on diesel engine valves and piston crowns encountered in marine diesel engines in Norwegian ships as hot-corrosion attributed to a reduced quality of residual fuel. His solution was to coat these components to reduce metal temperature below the threshold of aggressive hot-corrosion and also provide protection. Roy Kamo introduced thermal barrier coatings in his 'Adiabatic Diesel Engine' in the late 70's. Kamo's concept was to eliminate the engine block water cooling system and reduce heat losses. Roy reported significant performance improvements in his thermally insulated engine at the SAE Congress in 1982. Kamo's work stimulates major programs with insulated engines, particularly in Europe. Most of the major diesel engine manufacturers conducted some level of test with insulated combustion chamber components. They initially ran into increased fuel consumption. The German engine consortium had Prof. Woschni of the Technical Institute in Munich. Woschni conducted testing with pistons with air gaps to provide the insulation effects. Woschni indicated the hot walls of the insulated engine created a major increase in heat transfer he refers to as 'convection vive.' Woschni's work was a major factor in the abrupt curtailment of insulated diesel engine work in continental Europe. Ricardo in the UK suggested that combustion should be reoptimized for the hot-wall effects of the insulated combustion chamber and showed under a narrow range of conditions fuel economy could be improved. The Department of Energy has supported thermal barrier coating development for diesel engine applications. In the Clean Diesel - 50 Percent Efficient (CD-50) engine for the year 2000, thermal barrier coatings will be used on piston crowns and possibly other components. The primary purpose of the thermal barrier coatings will be to reduce thermal fatigue as the engine peak cylinder pressure will nearly be doubled. As the coatings result in higher available energy in the exhaust gas, efficiency gains are achieved through use of this energy by turbochargers, turbocompounding or thermoelectric generators.

Fairbanks, J. W.↗
NASA NTRS1972

Metal/silicate fractionation in the solar system.

Fractionation between the metal and silicate components of objects in the inner solar system has long been recognized as a necessity in order to explain the observed density variations of the terrestrial planets and the H-group, L-group dichotomy of the ordinary chondrites. This paper discusses the densities of the terrestrial planets in light of current physical and chemical models of processes in the solar nebula. It is shown that the observed density trends in the inner solar system need not be the result of special fractionation processes, and that the densities of the planets may be direct results of simultaneous application of both physical and chemical restraints on the structure of the nebula, most notably the variation of temperature with heliocentric distance. The density of Mercury is easily attributed to accretion at temperatures so high that MgSiO3 is only partially retained but Fe metal is condensed. The densities of the other terrestrial planet are shown to be due to different degrees of retention of S, O and H as FeS, FeO and hydrous silicates produced in chemical equilibrium between condensates and solar-composition gases.

Lewis, J. S.↗
NASA NTRSDate not supplied

System Modeling of a Lunar Molten Regolith Electrolysis Plant

Introduction: In-Situ Resource Utilization (ISRU) is the process of extracting local resources to produce commodities for propulsion, life support systems, and off-planet construction rather than transporting consumables from Earth. Molten Regolith Electrolysis (MRE) is a novel ISRU method of extracting oxygen gas and metal alloy from lunar regolith. The MRE process involves placing lunar regolith between two electrodes, through which current is passed, to melt the regolith and reduce the metal oxide constituents by direct electrolysis (e.g. FeO, SiO2, MgO, Al2O3) into oxygen gas and metal alloys. The oxygen is liquefied and used as propellant for landers, while the metals (e.g. Ferro-alloys) are further processed and used in structural building materials and parts manufacturing. A system model was developed that accounted for the major processes of an MRE plant (from excavation of raw materials to storage of products) to assess the feasibility of a lunar MRE plant. The System Engineering and Integration (SE&I) ISRU Modeling and Analysis (SIMA) team utilized its previously documented system sizing model, the Mission Analysis and Integration Tool (MAIT) [1] as framework of the system model. MAIT uses MATLAB/Simulink to integrate subsystem models into a complete system model of the MRE plant. Total mass, volume, and power requirements were computed for numerous iterations of a MRE plant. System Model: Figure 1: MRE Plant Block Diagram The regolith excavation model determines the mass and power needed to excavate sufficient regolith. The preheating auger initiates the regolith heating process before regolith enters the MRE re-actor to reduce the energy required to turn the solid into a molten liquid. The MRE reactor is modeled in COMSOL Multiphysics and based on the research by Dominguez, Sibille, and Schreiner [2, 3, 4]. This preliminary reactor model provides an accurate calculation of thermal equilibrium during electrochemical operation of the reactor system to assess the optimal mass and power required to process the inlet flow of regolith. The model also computes the outlet flowrates of oxygen and molten products. For this analysis, the primary components of the metal alloy considered were iron and silicon. The oxygen is then purified using an Yttrium Stabilized Zirconia (YSZ) electrode, followed by liquefaction using a 90K cryocooler to be stored as liquid oxygen in insulated cylindrical tanks. In future iterations of the system model, the molten metal tapped from the MRE reactor will undergo additional processing or refinement. However, downstream handling of metals is currently a technology gap that is missing a high TRL subsystem model. Therefore, for this analysis, the accumulated metal alloy stream terminates after leaving the MRE reactor. Study Goals: This analysis investigates multiple input variables to the system to determine the sensitivity of a (near) complete plant at full-scale. This preliminary investigation ran parametric sweeps on the MRE reactor geometry, electrical current supply, layers of multi-layer insulation (MLI) on the reactor, size of the electrodes in the oxygen purification model, and regolith composition (based on landing site location). Three production targets of oxygen (1,000, 10,000, and 50,000 kg/yr) were investigated for this analysis. The parametric sweeps conducted in this analysis provide valuable insight into the expected impact of the various model inputs on plant size. This information can be used to identify the most critical components of the plant and guide future decisions on allocating funding for research and development, providing subsystem developers with appropriate interfaces with downstream and upstream processes, and assessing the overall feasibility of MRE when compared to other ISRU plants. References: [1] Carlson, A. et al. (2024) ICES, ICES-2024-53. [2] Dominguez, D.A., and Sibille, L. (2011) AIAA, AIAA-2011-700. [3] Schreiner, S.S. (2015) MIT, Dissertation. [4] Schreiner, S.S. et al. (2016) ASR, 57(7), pp.1585-1603.

ISRU↗
NASA NTRS2020

Hardness-Strength Correlations in Zr(Cu)-Based BMG Alloys for QA Purposes

Quality assurance (QA) of bulk metallic glass (BMG) components would be expedited if hardness testing could provide a ready estimate of material strength. Consequently, a compilation of published data for Zr(Cu)-based alloys on the relationship between Vickers hardness (HV) and tensile/compressive strength (σ) is presented. An assessment reveals that the majority of data are confined within the hardness range of HV = 4.4−6.2 GPa and the strength range of σ = 1.4−2.3 GPa. Assuming a linear relationship, the statistical average of the hardness-strength correlation for BMGs (HV/σ = 2.87 ± 0.35) is very close to that established for non-austenitic steels (HV/σ = 2.86 ± 0.05). Unfortunately, the standard deviation of the BMG data is too broad for any type of correlation to be exploited for QA purposes. However, the narrow hardness range suggests that significant departures from the fully amorphous state resulting from processing variations may be detectable via indentation testing. Therefore, the relationship between hardness and volume/distribution of crystallinity for a specific alloy system warrants further investigation.

Bulk metallic glass↗
NASA NTRS1970

Coplanar interconnection module

Module for interconnecting a semiconductor array to external leads or components incorporates a metal external heat sink for cooling the array. Heat sink, extending down from the molded block that supports the array, is immersed in a liquid nitrogen bath which is designed to maintain the desired array temperature.

Steward, R. D.↗
NASA NTRS1973

Analysis of fatigue, fatique-crack propagation, and fracture data

Analytical methods have been developed for consolidation of fatigue, fatigue-crack propagation, and fracture data for use in design of metallic aerospace structural components. To evaluate these methods, a comprehensive file of data on 2024 and 7075 aluminums, Ti-6A1-4V, and 300M and D6Ac steels was established. Data were obtained from both published literature and unpublished reports furnished by aerospace companies. Fatigue and fatigue-crack-propagation analyses were restricted to information obtained from constant-amplitude load or strain cycling of specimens in air at room temperature. Fracture toughness data were from tests of center-cracked tension panels, part-through crack specimens, and compact-tension specimens.

Jaske, C. E.↗
NASA NTRS1975

Consolidation of fatigue and fatigue-crack-propagation data for design use

Analytical methods developed for consolidation of fatigue and fatigue-crack-propagation data for use in design of metallic aerospace structural components are evaluated. A comprehensive file of data on 2024 and 7075 aluminums, Ti-6Al-4V alloy, and 300M steel was established by obtaining information from both published literature and reports furnished by aerospace companies. Analyses are restricted to information obtained from constant-amplitude load or strain cycling of specimens in air at room temperature. Both fatigue and fatigue-crack-propagation data are analyzed on a statistical basis using a least-squares regression approach. For fatigue, an equivalent strain parameter is used to account for mean stress or stress ratio effects and is treated as the independent variable; cyclic fatigue life is considered to be the dependent variable. An effective stress-intensity factor is used to account for the effect of load ratio on fatigue-crack-propagation and treated as the independent variable. In this latter case, crack-growth rate is considered to be the dependent variable. A two term power function is used to relate equivalent strain to fatigue life, and an arc-hyperbolic-tangent function is used to relate effective stress intensity to crack-growth rate.

Rice, R. C.↗
NASA NTRS1978

Wide-temperature corrosion-resistant pressure regulator

Simplified design and all-metal-and-ceramic-components make pressure regulator compatible with corrosive fluids such as fluorine and hydrazine, and extends operating-temperature range. Flexure guidance eliminates hysteresis and friction, and self-generated contaminations are diminished enough to produce nearly unlimited maintenance-free lifetime.

Wichmann, H.↗
NASA NTRS1980

Deposition and material response from Mach 0.3 burner rig combustion of SRC 2 fuels

Collectors at 1173K (900 C) were exposed to the combustion products of a Mach 0.3 burner rig fueled with various industrial turbine liquid fuels from solvent refined coals. Four fuels were employed: a naphtha, a light oil, a wash solvent and a mid-heavy distillate blend. The response of four superalloys (IN-100, U 700, IN 792 and M-509) to exposure to the combustion gases from the SRC-2 naphtha and resultant deposits was also determined. The SRC-2 fuel analysis and insights obtained during the combustion experience are discussed. Particular problems encountered were fuel instability and reactions of the fuel with hardware components. The major metallic elements which contributed to the deposits were copper, iron, chromium, calcium, aluminum, nickel, silicon, titanium, zinc, and sodium. The deposits were found to be mainly metal oxides. An equilibrium thermodynamic analysis was employed to predict the chemical composition of the deposits. The agreement between the predicted and observed compounds was excellent. No hot corrosion was observed. This was expected because the deposits contained very little sodium or potassium and consisted mainly of the unreactive oxides. However, the amounts of deposits formed indicated that fouling is a potential problem with the use of these fuels.

Santoro, G. J.↗
NASA NTRS1984

Improving Trace-Ion Sensitivity

Background noise reduced by some special precautions. Blanket of argon flows over solution so no chance for contamination from air to creep in. Conventional pump replaced with one made of polytetrafluoroethlylene component and all metal couplings eliminated from flow lines. Used to improve quality control in integrated circuit fabrication, lens fabrication, and vacuum-tube assembly.

Buggle, R. N.↗
NASA NTRS1984

Acoustic emission evaluation of plasma-sprayed thermal barrier coatings

Acoustic emission techniques have recently been used in a number of studies to investigate the performance and failure behavior of plasma-sprayed thermal barrier coatings. Failure of the coating is a complex phenomena, especially when the composite nature of the coating is considered in the light of possible failure mechanisms. Thus it can be expected that both the metal and ceramic components (i.e., the bond coat and ceramic overlay) of a composite thermal protection system influence the macroscopic behavior and performance of the coating. The aim of the present work is to summarize the 'state-of-the-art' in terms of this initial work and indicate where future progress may be made.

Berndt, C. C.↗
NASA NTRS1985

Fastening Parts Having Mismatched Thermal Coefficients

Fastener eliminates thermal stresses and maintains snug fit. Conicalhead bolt and metal washer main components of fastener that keeps constant tension on carbon/carbon parts regardless of thermal stress. Fastener used in cases where fastened parts have unmatched thermalexpansion coefficients. Does not become looser or tighter as conventional bolts and nuts or rivets do at elevated temperatures.

Jackson, L. R.↗
NASA NTRS1993

Tin-polyimide and indium-polyimide thin-film composites as soft X-ray bandpass filters

A tin-polyimide and an indium-polyimide soft X-ray bandpass filter were fabricated with thicknesses of 1400 and 1750 A for the metal and polyimide components, respectively. The transmission of each filter was measured at the Stanford Synchrotron Radiation Laboratory. The transmission of the tin-polyimide filter was found to be about 40 percent for radiation with wavelengths between 60 and 80 A. The transmission of the indium-polyimide filter was greater than 40 percent between 70 and 90 A. The indium was about 5 percent more transmissive than the tin and attained a maximum transmission of about 48 percent at 76 A. Such filters have potential applications to soft X-ray telescopes that operate in this region. They might also be of interest to investigators who work with X-ray microscopes that image live biological specimens in the 23-44-A water window.

Powell, Stephen F.↗
NASA NTRS1997

Validation of Framework Code Approach to a Life Prediction System for Fiber Reinforced Composites

The grant was conducted by the MMC Life Prediction Cooperative, an industry/government collaborative team, Ohio Aerospace Institute (OAI) acted as the prime contractor on behalf of the Cooperative for this grant effort. See Figure I for the organization and responsibilities of team members. The technical effort was conducted during the period August 7, 1995 to June 30, 1996 in cooperation with Erwin Zaretsky, the LERC Program Monitor. Phil Gravett of Pratt & Whitney was the principal technical investigator. Table I documents all meeting-related coordination memos during this period. The effort under this grant was closely coordinated with an existing USAF sponsored program focused on putting into practice a life prediction system for turbine engine components made of metal matrix composites (MMC). The overall architecture of the NMC life prediction system was defined in the USAF sponsored program (prior to this grant). The efforts of this grant were focussed on implementing and tailoring of the life prediction system, the framework code within it and the damage modules within it to meet the specific requirements of the Cooperative. T'he tailoring of the life prediction system provides the basis for pervasive and continued use of this capability by the industry/government cooperative. The outputs of this grant are: 1. Definition of the framework code to analysis modules interfaces, 2. Definition of the interface between the materials database and the finite element model, and 3. Definition of the integration of the framework code into an FEM design tool.

Gravett, Phillip↗
NASA NTRS2002

Characterization of Ceramic Matrix Composite Fasteners Exposed in a Combustion Liner Rig Test

Combustion tests on SiC/SiC CMC (Ceramic Matrix Composite) components were performed in an aircraft combustion environment using the Rich-burn, Quick-quench, Lean-burn (RQL) sector rig. SiC/SiC fasteners were used to attach several of these components to the metallic rig structure. The effect of combustion exposure on the fastener material was characterized via microstructural examination. Fasteners were also destructively tested, after combustion exposure, and the failure loads of fasteners exposed in the sector rig were compared to those of as-manufactured fasteners. Combustion exposure reduced the fastener failure load by 50% relative to the as-manufactured fasteners for exposure times ranging from 50 to 260 hours. The fasteners exposed in the combustion environment demonstrated failure loads that varied with failure mode. Fasteners that had the highest average failure load, failed in the same manner as the unexposed fasteners.

Verrilli, Michael J.↗
NASA NTRS2005

Fabrication of High Temperature Cermet Materials for Nuclear Thermal Propulsion

Processing techniques are being developed to fabricate refractory metal and ceramic cermet materials for Nuclear Thermal Propulsion (NTP). Significant advances have been made in the area of high-temperature cermet fuel processing since RoverNERVA. Cermet materials offer several advantages such as retention of fission products and fuels, thermal shock resistance, hydrogen compatibility, high conductivity, and high strength. Recent NASA h d e d research has demonstrated the net shape fabrication of W-Re-HfC and other refractory metal and ceramic components that are similar to UN/W-Re cermet fuels. This effort is focused on basic research and characterization to identify the most promising compositions and processing techniques. A particular emphasis is being placed on low cost processes to fabricate near net shape parts of practical size. Several processing methods including Vacuum Plasma Spray (VPS) and conventional PM processes are being evaluated to fabricate material property samples and components. Surrogate W-Re/ZrN cermet fuel materials are being used to develop processing techniques for both coated and uncoated ceramic particles. After process optimization, depleted uranium-based cermets will be fabricated and tested to evaluate mechanical, thermal, and hot H2 erosion properties. This paper provides details on the current results of the project.

Hickman, Robert↗