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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Development of modified poly(perfluoropropyleneoxide) urethane systems for use in liquid oxygen and in enriched 100 percent oxygen atmosphere

This program consisted of two separate though related phases. The initial phase was directed toward improving the mechanical and adhesive properties of the very highly fluorinated-polyurethane resin system derived from the hydroxyl-terminated polyperfluoropropylene oxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate. Various new curing agents for this system were investigated, with the goal of providing a more thermally stable crosslink (cure) mechanism to provide wider applicability and fuller utilization of the outstanding oxygen resistance of the PFPO system. Complete resistance to liquid- and gaseous-oxygen impact at presures as high as 1035 N/sq cm were attained with the use of the PFPO resin castings. The second corollary phase was directed toward investigating the feasibility and optimization of the allophanate cured, urethane extended polymer derived from hydroxyl-terminated polyperfluoropropyleneoxide and 6-chloro-2,4,5-trifluoro-m-phenylene diisocyanate, as the adhesive system for use in a weld-bond configuration for liquid oxygen tankage. The synthesis and application procedures of the adhesive system to insure liquid oxygen compatibility (under 10 kg-m loading), and the development of procedures and techniques to provide high quality weld-bonded joint configurations were studied.

Harrison, E. S.↗
NASA NTRS1996

Guide for Oxygen Hazards Analyses on Components and Systems

Because most materials, including metals, will burn in an oxygen-enriched environment, hazards are always present when using oxygen. Most materials will ignite at lower temperatures in an oxygen-enriched environment than in air, and once ignited, combustion rates are greater in the oxygen-enriched environment. Many metals burn violently in an oxygen-enriched environment when ignited. Lubricants, tapes, gaskets, fuels, and solvents can increase the possibility of ignition in oxygen systems. However, these hazards do not preclude the use of oxygen. Oxygen may be safely used if all the materials in a system are not flammable in the end-use environment or if ignition sources are identified and controlled. These ignition and combustion hazards necessitate a proper oxygen hazards analysis before introducing a material or component into oxygen service. The objective of this test plan is to describe the White Sands Test Facility oxygen hazards analysis to be performed on components and systems before oxygen is introduced and is recommended before implementing the oxygen component qualification procedure. The plan describes the NASA Johnson Space Center White Sands Test Facility method consistent with the ASTM documents for analyzing the hazards of components and systems exposed to an oxygen-enriched environment. The oxygen hazards analysis is a useful tool for oxygen-system designers, system engineers, and facility managers. Problem areas can be pinpointed before oxygen is introduced into the system, preventing damage to hardware and possible injury or loss of life.

Stoltzfus, Joel M.↗
NASA NTRS2015

Evaluation of the Oxygen Concentrator Prototypes: Pressure Swing Adsorption Prototype and Electrochemical Prototype

An oxygen concentrator is needed to provide enriched oxygen in support of medical contingency operations for future exploration human spaceflight programs. It would provide continuous oxygen to an ill or injured crew member in a closed cabin environment. Oxygen concentration technology is being pursued to concentrate oxygen from the ambient environment so oxygen as a consumable resource can be reduced. Because oxygen is a critical resource in manned spaceflight, using an oxygen concentrator to pull oxygen out of the ambient environment instead of using compressed oxygen can provide better optimization of resources. The overall goal of this project is to develop an oxygen concentrator module that minimizes the hardware mass, volume, and power footprint while still performing at the required clinical capabilities. Should a medical event occur that requires patient oxygenation, the release of 100 percent oxygen into a small closed cabin environment can rapidly raise oxygen levels to the vehicles fire limit. The use of an oxygen concentrator to enrich oxygen from the ambient air and concentrate it to the point where it can be used for medical purposes means no oxygen is needed from the ultra-high purity (99.5+% O2) oxygen reserve tanks. By not adding oxygen from compressed tanks to the cabin environment, oxygen levels can be kept below the vehicle fire limit thereby extending the duration of care provided to an oxygenated patient without environmental control system intervention to keep the cabin oxygen levels below the fire limits. The oxygen concentrator will be a Food and Drug Administration (FDA) clearable device. A demonstration unit for the International Space Station (ISS) is planned to verify the technology and provide oxygen capability. For the ISS, the demonstration unit should not exceed 10 kg (approximately 22 lb), which is the soft stowage mass limit for launch on resupply vehicles for the ISS. The unit's size should allow for transport within the spacecraft to an ill crewmember. The user interface needs to be designed for ease of use by the local care provider and with consideration to the limited amount of training available to the astronaut corps for medical equipment and procedures.

Gilkey, Kelly M.↗
NASA NTRS1981

Performance calculations for 1000 MWe MHD/steam power plants

The effects of MHD generator operating conditions and constraints on the performance of MHD/steam power plants are investigated. Power plants using high temperature combustion air preheat (2500 F) and plants using intermediate temperature preheat (1100 F) with oxygen enrichment are considered. Variations of these two types of power plants are compared on the basis of fixed total electrical output (1000 MWe). Results are presented to show the effects of generator plant length and level of oxygen enrichment on the plant thermodynamic efficiency and on the required generator mass flow rate. Factors affecting the optimum levels of oxygen enrichment are analyzed. It is shown that oxygen enrichment can reduce magnet stored energy requirement.

Pian, C. C. P.↗
DOE OSTI2024

Flame kinetics at scramjet-engine-relevant conditions: Role of prompt dissociation of weakly-bound radicals

Combustion in high-speed ram-based propulsion engines occurs under distinct thermodynamic conditions of high reactant temperatures (greater than 1000 K) and relatively low pressures (<5 atm). There is a lack of fundamental flame measurements at such conditions that result in adiabatic flame temperatures (T ad ) exceeding 2500 K. In this work, we have measured laminar flame speeds of oxygen-enriched CH 4 /oxidizer mixtures at sub-atmospheric conditions to probe kinetics at high T ad using the isobaric spherically expanding flame approach. Simulations with recent kinetic models revealed increasing differences between data and model predictions with increasing T ad , reaching up to 25 %. Kinetic analyses reveal that at the thermodynamic conditions in these O 2 -enriched flames, i.e., lower pressures and higher T ad , the effects of HCO prompt dissociation are accentuated. In addition to HCO, the prompt dissociations of CH 2 OH and C 2 H 5 are also considered. Here, the prompt dissociations of all three radicals were evaluated and their effects considered in flame speed simulations. Reaction path analysis for the present flames revealed that approximately half of the reaction flux for HCO formation undergoes prompt dissociation to H + CO. Furthermore, these analyses also revealed that the pathways and sensitive reactions are similar between oxygen-enriched fuel/oxidizer mixtures and preheated fuel/air mixtures, if both have similar T ad . Thus, flames of oxygen-enriched mixtures could be a surrogate to probe the flame chemistry of highly preheated mixtures at relatively low pressures that are often encountered in ram-based propulsion engine combustors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Contributions of anoxic microsites to soil carbon protection across soil textures

Anoxic microsites, zones of oxygen depletion in otherwise oxic soils, may slow soil C turnover. However, the abundance of anoxic microsites and their contribution to soil C protection is yet undefined. In this study, we determine the contribution of anoxic microsites to soil C protection in soils of three distinct textures (clay loam, loam, sandy loam) across a range of soil moistures. We examined the influence of soil oxygen supply by increasing oxygen content in the incubation atmosphere (oxygen enrichment) and through disaggregation. We attributed increases in CO 2 efflux to the aeration of anoxic microsites. The contribution of anoxic microsites to soil C protection increased with decreasing clay content. Clay loam CO 2 efflux was relatively unaffected by aeration. Moderately moist, loam soils had CO 2 effluxes that did not increase with oxygen enrichment but increased by 375% upon disaggregation. Sandy loam soil CO 2 efflux increased by 50–75% with oxygen enrichment and 250% with disaggregation. Geochemical and microbial data reveal that anoxic microsite abundance also increased with decreasing clay content. The proportion of acid extractable Fe present as Fe(II) increased with decreasing clay content, and methanogens were more abundant in loam and sandy loam soils. Our results suggest that oxygen demand, rather than supply, can regulate anoxic microsite formation and that anoxic protection of soil C can be diminished through physical disruption of soil structure. Our findings further illustrate that anoxic microsites should be included in conceptual models of soil C protection to avoid soil C loss and improve predictions of soil C response to disturbance.

58 GEOSCIENCES↗
NASA NTRSDate not supplied

Ground Testing of an Oxygen Concentrator in a Simulated International Space Station (ISS) Cabin Environment

The method for supplying medical oxygen to respiratorily-compromised astronauts on the International Space Station (ISS) and in future Orion missions consists of drawing oxygen from high pressure oxygen tanks. An Oxygen Concentrator Module (OCM) is a device that pulls in ambient air and separates out the nitrogen, resulting in a high concentration oxygen source. This technology has the potential to eliminate resupply and oxygen-enrichment issues associated with using high pressure oxygen tanks and become an alternative technology to support medical oxygen operations for future exploration missions. In this study, we test the long-term performance of a Commercial Off-the-Shelf (COTS) OCM in a simulated ISS cabin environment. Humidified air, carbon dioxide, and fifteen representative trace contaminants are continuously injected through a enclosed test chamber where the OCM is challenged. This study included the first successful demonstration of the Trace Gas Injection System (TGIS), which reliably and continuously produced ISS levels of trace contaminants, carbon dioxide, and humidity in an enclosed environment. The TGIS is a new and unique ground capability with significant implications for Test Readiness Level (TRL) advancement of COTS items and Government Furnished Equipment (GFE). This study demonstrated that the tested OCM reliably delivers enriched oxygen mostly at desired performance specifications. This study also demonstrated that the OCM does not inadvertently concentrate trace gases in its oxygen product stream, as detectable concentrations of trace contaminants in the oxygen product stream were at all times below the simulated ISS levels.

medical oxygen↗
NASA NTRSDate not supplied

Ground Testing of an Oxygen Concentrator in a Simulated International Space Station (ISS) Cabin Environment

The method for supplying medical oxygen to respiratorily-compromised astronauts on the International Space Station (ISS) and in future Orion missions consists of drawing oxygen from high pressure oxygen tanks. An Oxygen Concentrator Module (OCM) is a device that pulls in ambient air and separates out the nitrogen, resulting in a high concentration oxygen source. This technology has the potential to eliminate resupply and oxygen-enrichment issues associated with using high pressure oxygen tanks and become an alternative technology to support medical oxygen operations for future exploration missions. In this study, we test the long-term performance of a Commercial Off-the-Shelf (COTS) OCM in a simulated ISS cabin environment. Humidified air, carbon dioxide, and fifteen representative trace contaminants are continuously injected through an enclosed test chamber where the OCM is challenged. This study included the first successful demonstration of the Trace Gas Injection System (TGIS), which reliably and continuously produced ISS levels of trace contaminants, carbon dioxide, and humidity in an enclosed environment. The TGIS is a new and unique ground capability with significant implications for Test Readiness Level (TRL) advancement of COTS items and Government Furnished Equipment (GFE). This study demonstrated that the tested OCM reliably delivers enriched oxygen mostly at desired performance specifications. This study also demonstrated that the OCM does not inadvertently concentrate trace gases in its oxygen product stream, as detectable concentrations of trace contaminants in the oxygen product stream were at all times below the simulated ISS levels.

medical oxygen↗
NASA NTRS1987

A simplified method for determining heat of combustion of natural gas

A simplified technique for determination of the heat of combustion of natural gas has been developed. It is a variation of the previously developed technique wherein the carrier air, in which the test sample was burnt, was oxygen enriched to adjust the mole fraction of oxygen in the combustion product gases up to that in the carrier air. The new technique eliminates the need for oxygen enrichment of the experimental mixtures and natural gas samples and has been found to predict their heats of combustion to an uncertainty of the order of 1 percent.

Singh, Jag J.↗
NASA NTRS1982

Comparative analysis of the conceptual design studies of potential early commercial MHD power plants (CSPEC)

A conceptual design study of the MHD/steam plant that incorporates the use of oxygen enriched air preheated in a metallic heat exchanger as the combustor oxidant showed that this plant is the most attractive for early commercial applications. The variation of performance and cost was investigated as a function of plant size. The contractors' results for the overall efficiencies are in reasonable agreement considering the slight differences in their plant designs. NASA LeRC is reviewing cost and performance results for consistency with those of previous studies, including studies of conventional steam plants. LeRC in house efforts show that there are still many tradeoffs to be considered for these oxygen enriched plants and considerable variations can be made in channel length and level of oxygen enrichment with little change in overall plant efficiency.

Sovie, R. J.↗
NASA NTRS1981

Conceptual design study of potential early commercial MHD powerplant. Report of task 2 results

The conceptual design of one of the potential early commercial MHD power plants was studied. The plant employs oxygen enrichment of the combustion air and preheating of this oxygen enriched air to an intermediate temperature of 1200 F attainable with a tubular type recuperative heat exchanger. Conceptual designs of plant componets and equipment with performance, operational characteristics, and costs are reported. Plant economics and overall performance including full and part load operation are reviewed. The projected performance and estimated cost of this early MHD plant are compared to conventional power plants, although it does not offer the same high efficiency and low costs as the mature MHD power plant. Environmental aspects and the methods incorporated in plant design for emission control of sulfur and nitrogen are reviewed.

Hals, F. A.↗
NASA NTRS1987

Determining Heats of Combustion of Gaseous Hydrocarbons

Enrichment-oxygen flow rate-ratio related to heat of combustion. Technique developed for determining heats of combustion of natural-gas samples. Based on measuring ratio m/n, where m is (volmetric) flow rate of oxygen required to enrich carrier air in which test gas flowing at rate n is burned, such that mole fraction of oxygen in combustion-product gases equals that in carrier air. The m/n ratio directly related to heats of combustion of saturated hydrocarbons present in natural gas.

Singh, Jag J.↗
NASA NTRS2017

Flame Retardant Fibers for Human Space Exploration - Past, Present, and Future

The National Aeronautics and Space Administration (NASA) has led in the development of unique flame retardant fibers for human spaceflight since the beginning of the Apollo program. After the Apollo 1 fire which killed Command Pilot Virgil I 'Gus' Grissom, Senior Pilot Edward H. White II, and Pilot Roger B. Chaffee from cardiac arrest on January 27, 1967, the accident investigators found severe third degree burns and melted spacesuits on the astronauts bodies. NASA immediately initiated an extensive research program aimed at developing flame retardant and flame resistant fibers for the enriched oxygen atmosphere of the Apollo crew cabin. Fibers are flame retardant when they have been modified by chemical and thermal treatments. Fibers are flame resistant when they are made of inherently flame resistant materials (i.e. glass, ceramic, highly aromatic polymers). Immediately after this tragic accident, NASA funded extensive research in specifically developing flame retardant fibers and fabrics. The early developmental efforts for human spaceflight were for the outer layer of the Apollo spacesuit. It was imperative that non-flammable fabrics be used in a 100% oxygen environment. Owens-Corning thus developed the Beta fiber that was immediately used in the Apollo program and later in the Space Shuttle program. Aside from the urgent need for protective fabrics for the spacesuit, NASA also needed flame retardant fabrics for both clothing and equipment inside the spacecraft. From the mid-1960s to the early 1980's, NASA contracted with many companies to develop inherently flame retardant fibers and flame retardant finishes for existing fibers. Fluorocarbons and aromatic polyamides were the polymers of great interest for the development of new inherently flame retardant fibers for enriched oxygen environments. These enriched environments varied for different space programs. For example, the Apollo program requirements were for materials that would not support combustion in a 70%/30% oxygen/nitrogen environment at 6.3 pounds per square inch (psi). The Skylab program flammability requirements were set at 80%/20% oxygen/nitrogen ratios at 5 psi. While many fibers produced under several NASA contracts were never used, a few have become commercial products. The intent of this paper is to present the developmental history of some of these new or modified textile fibers. These developmental efforts are presented at various levels of details depending on the source of the historical records.

Orndoff, Evelyne↗
NASA NTRS2007

Piloted Ignition to Flaming in Smoldering Fire-Retarded Polyurethane Foam

Experimental results are presented on the piloted transition from smoldering to flaming in the fire-retarded polyurethane foam Pyrell . The samples are small rectangular blocks with a square cross section, vertically placed in the wall of a vertical wind tunnel. Three of the vertical sample sides are insulated and the fourth side is exposed to an upward oxidizer flow of variable oxygen concentration and to a variable radiant heat flux. The gases emitted from the smoldering reaction pass upwards through a pilot, which consists of a coiled resistance heating wire. In order to compensate for the solid-phase and gas-phase effects of the fire retardants on the piloted transition from smoldering to flaming in Pyrell, it was necessary to assist the process by increasing the power supplied to the smolder igniter and the pilot (compared to that used for non-fire retarded foam). The experiments indicate that the piloted transition from smoldering to flaming occurs when the gaseous mixture at the pilot passes the lean flammability limit. It was found that increasing the oxygen concentration or the external heat flux increases the likelihood of a piloted transition from smoldering to flaming, and generally decreases the time delay to transition. The piloted transition to flaming is observed in oxygen concentrations of 23% and above in both low-density and high-density Pyrell. Comparisons with previous experiments show that the piloted transition from smoldering to flaming is possible under a wider range of external conditions (i.e. lower oxygen concentration) than the spontaneous transition from smoldering to flaming. The results show that the fire retardants in Pyrell are very effective in preventing the piloted transition to flaming in normal air, but Pyrell is susceptible to smoldering and the piloted transition to flaming in oxygen-enriched environments. Therefore, precautions should be taken in the design of applications of Pyrell in oxygen-enriched environments to reduce to the risk of a piloted transition to flaming.

Putzeys, O.↗
NASA NTRS1980

Results from study of potential early commercial MHD power plants and from recent ETF design work

The study deals with different 'moderate technology' entry-level commercial MHD power plants. Two of the reference plants are based on combustion of coal with air preheated in a high-temperature regenerative air heater separately fired with a low-BTU gas produced in a gasifier integrated with the power plant. The third reference plant design is based on the use of oxygen enriched combustion air. Performance calculations show that an overall power plant efficiency of the order of 44% can be reached with the use of oxygen enrichment.

Hals, F.↗
DOE OSTI2023

Particle Size Distribution and Its Impacts on Ash Deposition and Radiative Transfer during Oxy-Combustion of Rice Husk–Natural Gas

Rice husk (RH) co-combustion with natural gas in highly oxygen-enriched concentrations presents a net carbon-negative energy production opportunity while minimizing flue gas recycling. However, recent experiments have shown enhanced ash deposition rates in oxygen-enriched conditions, with deposition/shedding also being dependent on the particle size distribution (PSD) of the parent RH fuel. To uncover the causative mechanisms behind these observations, add-on models for ash deposition/shedding and radiative properties were employed in computational fluid dynamics simulations. The combustion scenarios investigated encompassed two types of RH (US RH, Chinese RH) with widely varying ash contents (by % mass) and inlet fuel PSD with air and O2/CO2 (70/30 vol %, OXY70) as oxidizers. Utilizing the measured fly-ash PSDs near the deposit surface and modeling the particle viscosity accurately, particle kinetic-energy (PKE)-based capture and shedding criteria were identified as the keys to accurate deposition/shedding rate predictions. The OXY70 scenarios showed higher ash-capturing propensities due to their lower PKE. Conversely, higher erosion rates were predicted in the AIR firing scenarios. In addition, the radiative characteristics across all the scenarios were dominated by the gases and were not sensitive to the fly-ash PSD. Therefore, the higher particle concentrations in the OXY70 conditions did not negatively impact the heat extraction.

Krishnamoorthy, Gautham (ORCID:0000000255205092)↗
NASA NTRS1979

Coupled generator and combustor performance calculations for potential early commercial MHD power plants

A parametric study of the performance of the MHD generator and combustor components of potential early commercial open-cycle MHD/steam power plants is presented. Consideration is given to the effects of air heater system concept, MHD combustor type, coal type, thermal input power, oxygen enrichment of the combustion, subsonic and supersonic generator flow and magnetic field strength on coupled generator and combustor performance. The best performance is found to be attained with a 3000 F, indirectly fired air heater, no oxygen enrichment, Illinois no. 6 coal, a two-stage cyclone combustor with 85% slag rejection, a subsonic generator, and a magnetic field configuration yielding a constant transverse electric field of 4 kV/m. Results indicate that optimum net MHD generator power is generally compressor-power-limited rather than electric-stress-limited, with optimum net power a relatively weak function of operating pressure.

Dellinger, T. C.↗