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At least 235 records · Page 13

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NASA NTRS1981

Fumigation of Alcohol in a Light Duty Automotive Diesel Engine

A light-duty automotive Diesel engine was fumigated with methanol in amounts up to 35% and 50% of the total fuel energy respectively in order to determine the effect of alcohol fumigation on engine performance at various operating conditons. Engine fuel efficiency, emissions, smoke, and the occurrence of severe knock were the parameters used to evaluate performance. Raw exhaust particulate and its soluble organic extract were screened for biological activity using the Ames Salmonella typhimurium assay. Results are given for a test matrix made up of twelve steady-state operating conditions. For all conditions except the 1/4 rack (light load) condition, modest thermal efficiency gains were noted upon ethanol fumigation. Methanol showed the same increase at 3/4 and full rack (high load) conditions. However, engine roughness or the occurrence of severe knock limited the maximum amount of alcohol that could be fumigated. Brake specific nitrogen oxide concentrations were found to decrease for all ethanol conditions tested. Oxides of nitrogen emissions, on a volume basis, decreased for all alcohol conditions tested. Based on the limited particulate data analyzed, it appears that ethanol fumigation, like methanol fumigation, while lowering the mass of particulated emitted, does enhance the biological activity of that particulate.

Broukhiyan, E. M. H.↗

NASA NTRS1992

Component test results from the bearing life improvement program for the Space Shuttle Main Engine oxidizer turbopumps

Interim results from a component test program to improve ball bearing life in the Space Shuttle Main Engine oxygen turbopumps are presented. Two specific bearing applications, using liquid oxygen as the bearing coolant, are addressed. The first, the thrust bearing of the low pressure pump, operates at relatively slow speed with predominantly axial load and little temperature rise in the bulk coolant. Testing has demonstrated a very significant reduction in bearing wear by increasing the bearing internal clearance. Heat generation data was obtained that indicates heavy, intermittent cage-to-ball contact occurs, providing a possible explanation for the observed wear. The second application is the turbine end bearings of the high pressure pump. These bearings operate at high speed and load with the possibility of significant coolant vaporization. Tests on production bearings and bearings having modified internal clearance and curvature yielded scattered but generally poor lives. A dramatic improvement was achieved by coating the standard cage with a thin film of fluorinated ethylene propylene and 15 percent molybdenum disulfide. Very promising results have also been obtained by replacing the standard balls with ones made of silicon nitride, especially in combination with the coated cage.

Keba, John E.↗

NASA NTRS2013

Single-Event Effect Report for EPC Series eGaN FETs: EPC1001, EPC1010, EPC1014, EPC1012

Heavy ion testing of newly available GaN FETs from EPC were tested in March of 2012 at TAM. The EPC1010, EPC1001, EPC1012, and EPC1014 were tested for general radiation response from gold and xenon ions. Overall the devices showed radiation degradation commensurate with breakdown in isolation oxides, and similar testing by EPC and Microsemi agrees with these data. These devices were the first generation production of the device called Gen1. Gen2 parts are scheduled for later in the third quarter of FY2012

Scheick, Leif↗

NASA NTRS2013

Single-Event Effect Report for EPC Series eGaN FETs: EPC1001, EPC1010, EPC1014, EPC1012

Scheick, Leif↗

NASA NTRS1962

STABILITY TESTS OF MONOPROPELLANTS EXPOSED TO FLAMES AND RIFLE FIRE

Tests of the stability of several monopropellants under the effects of impact and heat were conducted in order to assess the potential hazard in a propellant storage area from major fires and enemy attack. Hydrazine, hydrazine nitrate solution, n-propyl nitrate, and ethylene oxide were all tested in one-gallon aluminum containers (half of them filled to 25% and half to 95% capacity) by being subjected to oil bonfires and wood bonfires, and 20-mm incendiary, 20mm high explosive incendiary, and .30-caliber rifle fire. Aviation gasoline was tested in the same manner, for comparison. In the bonfire tests, all four monopropellants generally gave explosion intensities equivalent to one another regardless of the type of bonfire (oil or wood) or the amount of liquid in the test container. Occasionally, however, with hydrazine, hydrazine nitrate solution, and n-propyl nitrate, anomalous results occurred: there was either (a) no explosion or (b) an explosion of above average intensity. Ethylene oxide more nearly approximated the behavior of aviation gasoline than did the other monopropellants. In the rifle-fire tests, n-propyl nitrate appeared to be most shock- sensitive since it was exploded by all three types of ammunition. Hydrazine and hydrazine nitrate solution were exploded by the high-explosive ammunition, but not by the incendiary or .30-dber ammunition. Ethylene oxide was not exploded by any of the gunfire, but the liquid was ignited by both incendiary and high-explosive incendiary ammunition.

FIRING↗

NASA NTRS1982

Thermochemical generation of hydrogen

The direct fluid contact heat exchange with H2SO4 at about 330 C prior to high temperature decomposition at about 830 C in the oxygen release step of several thermochemical cycles for splitting water into hydrogen and oxygen provides higher heat transfer rates, savings in energy and permits use of cast vessels rather than expensive forged alloy indirect heat exchangers. Among several candidate perfluorocarbon liquids tested, only perfluoropropylene oxide polymers having a degree of polymerization from about 10 to 60 were chemically stable, had low miscibility and vapor pressure when tested with sulfuric acid at temperatures from 300 C to 400 C.

Lawson, D. D.↗

NASA NTRS1991

Aqueous alteration on the parent bodies of carbonaceous chondrites: Computer simulations of late-stage oxidation

CI carbonaceous chondrites may be products of hydrous alteration of CV- or anhydrous CM-type materials. The CIs typically contain veins filled with carbonates and sulfates, probably indicating a period of late stage aqueous alteration under oxidizing conditions. To test this idea, computer simulations of aqueous alteration of CV- and CM-type carbonaceous were performed. Simulations were restricted to the oxidation of hydrous mineral assemblages produced in previous simulations in order to determine whether further reaction and oxidation results in the phyllosilicate, carbonate, sulfate and oxide vein assemblages typical of CI carbonaceous chondrites. Our simulations were performed at 1, 25, 100, and 150 C (the appropriate temperature range) for the CV and CM mineral assemblages and using the computer code EQ3/6.

Bourcier, W. L.↗

NASA NTRS2014

Single-Event Effect Report for EPC Series eGaN FETs: EPC2015, EPC2014, EPC2012

Heavy ion testing of newly available eGaN FETs from EPC were tested in May of 2012 at TAM. The EPC2001, EPC2012, and EPC2014 were tested for general single-event effect response from gold and xenon ions. Overall, the devices showed radiation degradation commensurate with breakdown in isolation oxides, and similar testing by EPC and Microsemi agrees with these data.

Scheick, Leif↗

NASA NTRS2004

Solid oxidized fuel cells seals leakage setup and testing

As the world s reserves of fossil fuels are depleted, the U.S. Government, as well as other countries and private industries, is researching solutions for obtaining power, answers that would be more efficient and environmentally friendly. For a long time engineers have been trying to obtain the benefits of clean electric power without heavy batteries or pollution-producing engines. While some of the inventions proved to be effective (i.e. solar panels or windmills) their applications are limited due to dependency on the energy source (i.e. sun or wind). Currently, as energy concerns increase, research is being carried out on the development of a Solid Oxide Fuel Cell (SOFC). The United States government is taking a proactive role in expanding the technology through the Solid State Energy Conversion Alliance (SECA) Program, which is coordinated by the Department of Energy. into an electrical energy. This occurs by the means of natural tendency of oxygen and hydrogen to chemically react. While controlling the process, it is possible to harvest the energy given off by the reaction. SOFCs use currently available fossil fuels and convert a variety of those fuels with very high efficiency (about 40% more efficient than modem thermal power plants). At the same time they are almost entirely nonpolluting and due to their size they can be placed in remote areas. The main fields where the application of the fuel cells appears to be the most useful for are stationary energy sources, transportation, and military applications. structure and materials must be resolved. All the components must be operational in harsh environments including temperatures reaching 800 C and cyclic thermal- mechanical loading. Under these conditions, the main concern is the requirement for hermetic seals to: (1) prevent mixing of the fuel and oxidant within the stack, (2) prevent parasitic leakage of the fuel from the stack, (3) prevent contamination of the anode by air leaking into the stack, (4) electrically isolate the individual cells within the stack, and (5) mechanically bond the cell components. The sealing challenges are aggravated by the need to maintain hermetic boundaries between the different flow paths within the fuel cell throughout cycled operation. Within the timeframe of my tenure, the main objective is to assist in building a state-of-art test facility.

Bastrzyk, Marta B.↗

NASA NTRS1983

The effects of Cr, Al, Ti, Mo, W, Ta, and Cb on the cyclic oxidation behavior of cast Ni-base superalloys at 1100 and 1150 C

Fifty Ni-base superalloys with concentrations of Cr, Al, Ti, Mo, W, Ta, and Cb systematically varied between two nonzero levels, were tested for cyclic oxidation resistance at 1100 and 1150 C. Oxidation resistance was interpreted in terms of the rate of specific weight change and the types of oxides formed. It is found that the resistance of the alloys to cyclic oxidation is largely determined by Al content, with a sharp increase in the oxidation resistance observed in the Al concentration range 5-8 at. pct. The effects of the other elements studied were small compared with that of aluminum. Best oxidation resistance characteristics were predicted for high Al (13 at. pct), low Cr (10 at. pct), low Ti (2 at. pct), low Cb (1 at. pct), and high Mo, W, and Ta (3 at. pct each). The effects of the refractory metals, however, are somewhat ambiguous and should be investigated further. Higher boron contents, which were unintentionally varied, were clearly detrimental even for the most resistant compositions.

Barrett, C. A.↗

NASA NTRS1982

Oxidation of low cobalt alloys

Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

Barrett, C. A.↗

NASA NTRS1970

Space-storable oxidizer valve Final report

Fabrication and acceptance testing, fluorine compatibility testing, valve refurbishment and testing, environmental testing, and design of space storable oxidizer valve

De Gennaro, T. R.↗

NASA NTRS2005

Protection of Conductive and Non-conductive Advanced Polymer-based Paints from Highly Aggressive Oxidative Environments

Research has been continued to further improve the space durability of conductive and non-conductive polymer-based paints and of conductive thermal control paints for space applications. Efforts have been made to enhance the space durability and stability of functional Characteristics in ground-based space environment imitating conditions, using specially developed surface modification treatment. The results of surface modification of new conductive paints, including the ground-based testing in aggressive oxidative environments, such as atomic oxygen/UV and oxygen plasma, and performance evaluation are presented. Functional properties and performance characteristics, such as thermal optical properties (differential solar absorptance and thermal emittance representing the thermal optical performance of thermal control paints) and surface resistivity characteristics of pristine, surface modified, and tested materials were verified. Extensive surface analysis studies have been performed using complementary surface analyses including SEM/EDS and XPS. Test results revealed that the successfully treated materials exhibit reduced mass loss and no surface morphology change, thus indicating good protection from the severe oxidative environment. It was demonstrated that the developed surface modification treatment could be applied successfully to charge dissipative and conductive paints.

Gudimenko, Y.↗

NASA NTRS1992

Analysis of samples of reflector materials which are multicoated and metal samples with oxide coatings which have been exposed the space environment in LDEF testing

The use of low angle x-ray diffraction (XRD), x-ray photoelectron spectrometry (XPS), and Auger spectrometry have been tested as suitable methods for analysis of thin oxide films on metal substrates exposed to the space environment during Long Duration Exposure Facility (LDEF) testing. No significant changes in the composition of silicon monoxide overcoats on aluminum surfaces was found. XPS and Auger testing appear to be more suitable for ultrathin films than XRD.

Neely, W. C.↗

NASA NTRS1989

Advanced Launch System advanced development oxidizer turbopump program: Technical implementation plan

The Advanced Launch Systems (ALS) Advanced Development Oxidizer Turbopump Program has designed, fabricated and demonstrated a low cost, highly reliable oxidizer turbopump for the Space Transportation Engine that minimizes the recurring cost for the ALS engines. Pratt and Whitney's (P and W's) plan for integrating the analyses, testing, fabrication, and other program efforts is addressed. This plan offers a comprehensive description of the total effort required to design, fabricate, and test the ALS oxidizer turbopump. The proposed ALS oxidizer turbopump reduces turbopump costs over current designs by taking advantage of design simplicity and state-of-the-art materials and producibility features without compromising system reliability. This is accomplished by selecting turbopump operating conditions that are within known successful operating regions and by using proven manufacturing techniques.

Ferlita, F.↗

NASA NTRS1977

High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

Lowell, C. E.↗

NASA NTRS1994

Automated System Tests High-Power MOSFET's

Computer-controlled system tests metal-oxide/semiconductor field-effect transistors (MOSFET's) at high voltages and currents. Measures seven parameters characterizing performance of MOSFET, with view toward obtaining early indication MOSFET defective. Use of test system prior to installation of power MOSFET in high-power circuit saves time and money.

Huston, Steven W.↗

NASA NTRS2001

Carbon Nanostructure: Its Evolution During its Impact Upon Soot Growth and Oxidation

The proposed work is a ground-based study to define and quantify soot nanostructural changes in response to growth conditions, thermal and oxidative treatments and to quantify their impact upon further oxidation and growth of highly ordered carbon materials. Experimental data relating soot oxidation rates to multiple oxidizing species concentrations will directly test for additive or synergistic soot oxidation rates. Such validation is central for assessing the applicability of individual soot oxidation rates and designing oxidative strategies for controlling soot loadings in and emissions from turbulent combustion processes. Through these experiments, new insights into soot nanostructure evolution during and its impact upon oxidation by O2 and OH will be realized. It is expected that the results of this effort will spawn new research directions in future microgravity and 1g environments. Issues raised by positive or even negative demonstration of the hypotheses of this proposal have direct bearing on modelling and controlling soot formation and its destruction in nearly every combustion process producing soot.

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