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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Silica modulated palladium catalyst with superior activity for the selective catalytic reduction of nitrogen oxides with hydrogen

A significant promotion effect of colloidal SiO 2 on Pd/TiO 2 catalyst for improving the activity and N 2 selectivity in the selective catalytic reduction of NO with H 2 (H 2 -SCR) was reported, both before and after hydrothermal aging. The SiO 2 addition not only benefited the formation of more oxygen vacancies but also increased Pd dispersion and created rich Pd-SiO 2 interfaces on Pd-SiO 2 /TiO 2 catalyst. The H 2 -SCR of NO on both Pd/TiO 2 and Pd-SiO 2 /TiO 2 followed a Langmuir-Hinshelwood mechanism, in which the adsorbed bridging bidentate nitrates on TiO 2 could react with dissociated H 2 species on Pd sites at Pd-TiO 2 interface. Particularly, on the promoted Pd-SiO 2 /TiO 2 , the Pd-TiO 2 interface could facilitate NO adsorption and activation, and the created Pd-SiO 2 interface could benefit H 2 adsorption and dissociation, thus contributing to its significantly improved H 2 -SCR activity. Additionally, the active Pd species (which should be Pd0 under reaction condition with higher surface concentration) within Pd-SiO 2 /TiO 2 could be well stabilized during long-term hydrothermal aging process through the formation of rich Pd-SiO 2 interfaces.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A comparative study of silver- and palladium-exchanged zeolites in propylene and nitrogen oxide adsorption and desorption for cold-start applications

Here, silver and palladium ion-exchanged BEA zeolites (Si/Al = 12.5) and silver ion-exchanged ZSM-5 zeolites (Si/Al = 15) were studied for their ability to adsorb and desorb propylene and NO under simulated diesel exhaust conditions. The adsorption experiment results demonstrated the excellent ability of bare BEA zeolites to adsorb propylene, but only a small amount of NO. The presence of H 2 O inhibited the adsorption of both C 3 H 6 and NO. Ion-exchanging BEA zeolites with Ag (1.2 and 5.1 wt.% Ag/BEA) attenuated the inhibiting effect of H 2 O on C 3 H 6 adsorption, while NO storage remained inhibited. Adsorption experiments indicated that C 3 H 6 and NO competed with each other for Pd sites with C 3 H 6 showing stronger adsorption compared to NO, whereas Ag sites preferentially adsorbed C 3 H 6 . DRIFTS data indicated the formation of nitrate, formate and acetate species on Ag and Pd, while C 3 H 6 and NO adsorption was also observed on the zeolite hydroxyl groups in the absence of H 2 O. However, the C 3 H 6 and NO adsorption on the zeolite hydroxyl groups was significantly inhibited in the presence of H 2 O. Additionally, nitrosyl, acrolein and carbonate species were formed over 1.0 wt.% Pd/BEA. The effluent analysis during the temperature-programmed desorption in the DRIFTS reactor revealed that adsorbed C 3 H 6 and NO reacted during the release to form oxidation reaction byproducts. The 1.0 wt.% Pd/BEA zeolite showed the greatest oxidation ability during desorption with the majority of stored C 3 H 6 converted to CO 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Finite-rate entrainment effects on nitrogen oxide (NO x ) emissions in staged combustors

Axially staged combustors offer the potential for achieving low NO x emissions from gas turbines at the elevated temperatures required to achieve at least 65% combined cycle efficiencies. While there is evidence that premixing between the main burner products and secondary stream reduces NO x , it is important to characterize the specific requirements needed to achieve low emissions at gas turbine conditions. This study examines the sensitivity of NO x to finite-rate, large-scale entrainment of the main and secondary streams under the simplifying assumption of infinitely-fast small-scale mixing. Essentially, this allows us to isolate the effects of limited large-scale entrainment rates by using a homogeneous/uniform condition for the entrained and reacting gases. We use a reduced-order reactor network model to examine a generic staged-combustor whose inputs are physical time scales that embody the finite-rate entrainment characteristics. With simulations conducted over a large parameter space at typical operating conditions (25 atm, 650 K air), the results show that, even when small-scale mixing is infinitely fast and the reaction zone is uniform, entrainment significantly affects NO x emissions due to its influence on the equivalence ratio — and thus the temperature and time — at which the entrained mixture ignites. Fuel-air staging is shown to be vital to NO x reduction in most practical cases where entrainment times exceed roughly 1 ms and the secondary stream finishes entraining before the main burner products. A constrained NO x minimization indicates that using the leanest possible main burner and re-routing as much air as possible to the secondary stage is key to low NO x with finite-rate entrainment; for example, less than 10 ppm NO x can be achieved if the secondary stage contains 20% of the total mass flow.

03 NATURAL GAS↗
DOE OSTI2026

Measured Indoor Nitrogen Oxides in Homes with a Child with Asthma and Gas or Induction Electric Cooking

The Cooking Energy and Ventilation Impacts on Children's Asthma (CEVICA) study is a randomized control trial investigating the effects of replacing gas with induction electric ranges in the homes of children with asthma in California's San Joaquin Valley. Indoor air quality parameters and respiratory health indicators were measured over 2-week intensive at Baseline and after consecutive 3-month study phases, with half getting electric cooking at the start of Phase 1 and others in Phase 2. Indoor air measurements included time-integrated NO 2 and NO X by passive sampler and time-resolved NO 2 by electrochemical sensors. In the first 40 homes, data were collected during 61 intensives for gas cooking and 55 for induction. Cooking was identified using temperature sensors above the cooktop. Pollutant events were identified from sharp rises in concentrations Time integrated NOX species were lower with electric cooking, with mean differences of 14.2 ppb for NO 2 (95% CI: 9.6, 18.7; p < 0.001), 55.6 ppb for NO X (95% CI: 30.4, 80.9; p < 0.001), and 41.5 ppb for derived NO (95% CI: 19.7, 63.2; p < 0.001). A paired, within home analysis showed larger reductions in Group 2 (gas to induction) than Group 1 that remained electric across Phase 1 and Phase 2 for NO 2 (mean difference in As of 10.5 ppb; 95% CI: 5.6, 15.4; p < 0.001), NO X (32.3 ppb; 95% CI: 10.0, 54.5; p=0.007), and derived NO (21.8 ppb; 95% CI: 3.6, 40.0; p=0.022). Compared to electric cooking, gas had much higher rates of associated NO 2 events, and larger above-baseline NO 2 peaks. These preliminary results are consistent with prior findings that shifting to induction cooking can substantially lower indoor NO 2 compared with gas cooking.

Fang, Yi↗
NASA NTRS1975

Stratospheric ozone destruction by aircraft-induced nitrogen oxides

The preliminary results from a three-dimensional dynamic-chemical model applied to the SST-NOx (NO + NO2) problem are reported. Simulations indicate that a depletion of about 12 per cent in total stratospheric O3 would be realized for a continuous NOx injection rate of 1.8 x 10 to the sixth power metric tons per year from a hypothetical fleet of SST's flying at an altitude of 20 km in the midlatitudes of the Northern Hemisphere. Sixteen per cent of the existing O3 would be destroyed on an annual basis. The model assumes a fleet of about 500 aircraft of the now-canceled American Boeing 2707 type; if only present Anglo-French and Russian SST models, which fly at lower, less harmful altitudes, are built, it will take a fleet of a few thousand such craft to attain an effective injection rate equal to the one above.

Alyea, F. N.↗
NASA NTRS1989

Nitrogen oxides from high-altitude aircraft - An update of potential effects on ozone

In the study of fuel consumption rate by stratospheric aircraft, the range of nitric oxide injection is interpreted as an eightfold range of emission index (5-40) with both the one- and the two-dimensional models. Possible effects of future aircraft NO(x) emissions on stratospheric ozone are considered for a broad range in magnitude, altitude, and latitude of the assumed NO(x) emissions. Results of the sensitivity studies using both models are discussed. Large ozone reductions are found to be outside the expected range of validity of these models and are to be anticipated if there should be a large fleet of stratospheric aircraft with NO(x) emission characteristics of current commercial aircraft. Under the test conditions, a global ozone reduction of about 9 percent is estimated for a jet engine emission index of 15 in both models. If engines are redesigned to reduce the emission index to the NASA goal of 5, global average ozone reductions are between 2 and 3 percent, and those of the Northern Hemisphere are about 4 percent. The effects of stratospheric aircraft on ozone could be further reduced through operation at lower altitudes, reduction of aircraft, and efficient fuel consumption.

Johnston, Harold S.↗
NASA NTRS1990

Atmospheric peroxyacetyl nitrate measurements over the Brazilian Amazon Basin during the wet season - Relationships with nitrogen oxides and ozone

An analysis is presented on the distribution and variability of PAN as well as its relationship with measured chemical and meteorological parameters. The chemicals of most interest for which measurements were available are PAN, NO(x), O3, CO, and C2Cl4. PAN was measured by the electron capture gas chromatographic technique, and the technique for calibrations and measurements are detailed. Data show that significant concentrations of PAN (5-125 ppt) are present during the wet season and this PAN is 1-5 times more abundant than NO(x). PAN levels at different atmospheric locations are discussed, and it is noted that PAN shows evidence of a possible latitudinal gradient in the free troposphere, with values falling rapidly from the northern midlatitudes toward the equator. High correlations between O3 and PAN levels suggest that nonmethane hydrocarbons may contribute significantly to high O3 in the free troposphere. Evidence indicates that virtually all of the NO(x) above 4 km could result from PAN decomposition.

Singh, H. B.↗
NASA NTRS1999

Nitrogen Oxides and Ozones from B-747 Measurements (NOXAR) during POLINAT 2 and SONEX: Overview and Case-Studies on Continental and Marine Convection

In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 98 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO, concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x), enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case-studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, with lightning observations from the U.S. National Lightning Detection Network (NLDN) or with the Optical Transient Detector (OTD) satellite. For frontal activity above the continental U.S., we demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. For another case we show that the number of lightning flashes in a cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows and suggest that lightning was the dominant source. From the fact that in autumn the NO, maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are an important source for the regional upper tropospheric NO(x) budget in autumn.

Jeker, Dominique↗
NASA NTRS1998

Downsizing of Georgia Tech's Airborne Fluorescence Spectrometer (AFS) for the Measurement of Nitrogen Oxides

This report addresses the Tropospheric Trace Gas and Airborne Measurements (TTGAMG) endeavors to further downsize and stabilize the Georgia Institute of Technology's Airborne Laser Induced Fluorescence Experiment (GITALIFE). It will mainly address the TTGAMG successes and failures as participants in the summer 1998 Wallops Island test flights on board the P3-B. Due to the restructuring and reorganization of the TTGAMG since the original funding of this grant, some of the objectives and time lines of the deliverables have been changed. Most of these changes have been covered in the preceding annual report. We are anticipating getting back on track with the original proposal's downsizing effort this summer, culminating in the GITALIFE no longer occupying a high bay rack and the loss of several hundred pounds.

Sandholm, Scott↗
NASA NTRS1997

Nitrogen Oxides and Ozone from B-747 Measurements (NOXAR) During POLINAT-2 and SONEX: Overview and Case Studies on Continental and Marine Convection

In the framework of the project POLINAT 2 (Pollution in the North Atlantic Flight Corridor) we measured NO(x) (NO and NO2) and ozone on 85 flights through the North Atlantic Flight Corridor (NAFC) with a fully automated system permanently installed aboard an in-service Swissair B-747 airliner in the period of August to November 1997. The averaged NO(x) concentrations both in the NAFC and at the U.S. east coast were similar to that measured in autumn 1995 with the same system. The patchy occurrence of NO(x) enhancements up to 3000 pptv over several hundred kilometers (plumes), predominately found over the U.S. east coast lead to a log-normal NO(x) probability density function. In three case studies we examine the origins of such plumes by combining back-trajectories with brightness temperature enhanced (IR) satellite imagery, lightning observations from the U.S. National Lightning Detection Network (NLDN) and the Optical Transient Detector (OTD) satellite. We demonstrate that the location of NO(x) plumes can be well explained with maps of convective influence. We show that the number of lightning flashes in cluster of marine thunderstorms is proportional to the NO(x) concentrations observed several hundred kilometers downwind of the anvil outflows. From the fact that in autumn the NO(x) maximum was found several hundred kilometers off the U.S. east coast, it can be inferred that thunderstorms triggered over the warm Gulf Stream current are major sources for the regional upper tropospheric NO(x) budget in autumn.

Jeker, Dominique P.↗
NASA NTRS1999

SONEX: NASA SASS Ozone and Nitrogen Oxide Experiment

This final report follows closely on our 1998 Annual Progress Report which was forwarded to NASA on November 19, 1998. Rather than reiterate the material therein we note here the continuation of the various items covered. SONEX has proN,Ided a number of opportunities to learn more about the fine-scale structure of the atmosphere. Coupled with the MOZAIC work on layers we can synthesize a new 3-D view of the fine scales that influence atmospheric chemistry. As a side issue we are also relating the features to clear air turbulence which would be, we think, a useful connection for commercial aviation.

Newell, Reginald E.↗