Low NO(x) potential of gas turbine engines

NASA Technical Reports Server (NTRS)

Tacina, Robert R.

1990-01-01

The purpose is to correlate emission levels of gas turbine engines. The predictions of NO(x) emissions are based on a review of the literature of previous low NO(x) combustor programs and analytical chemical kinetic calculations. Concepts included in the literature review consisted of lean-premixed-prevaporized (LPP), rich burn/quick quench/lean burn (RQL), and direct injection. The NO(x) emissions were found to be an exponential function of adiabatic combustion temperature over a wide range of inlet temperatures, pressures and (lean) fuel-air ratios. A simple correlation of NO(x) formation with time was not found. The LPP and direct injection (using gaseous fuels) concepts have the lowest NO(x) emissions of the three concepts. The RQL data has higher values of NO(x) than the LPP concept, probably due to the stoichiometric temperatures and NO(x) production that occur during the quench step. Improvements in the quick quench step could reduce the NO(x) emissions to the LPP levels. The low NO(x) potential of LPP is offset by the operational disadvantages of its narrow stability limits and its susceptibility to autoignition/flashback. The Rich-Burn/Quick-Quench/Lean-Burn (RQL) and the direct injection concepts have the advantage of wider stability limits comparable to conventional combustors.

Ammonia Generation and Utilization in a Passive SCR (TWC+SCR) System on Lean Gasoline Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prikhodko, Vitaly Y; Parks, II, James E; Pihl, Josh A

Lean gasoline engines offer greater fuel economy than the common stoichiometric gasoline engine, but the current three-way catalyst (TWC) on stoichiometric engines is unable to control nitrogen oxide (NOX) emissions in the oxygen-rich exhaust. Thus, lean NOX emission control is required to meet existing Tier 2 and upcoming Tier 3 emission regulations set by the U.S. Environmental Protection Agency (EPA). While urea-based selective catalytic reduction (SCR) has proven effective in controlling NOX from diesel engines, the urea storage and delivery components can add significant size and cost. As such, onboard NH3 production via a passive SCR approach is of interest.more » In a passive SCR system, NH3 is generated over a close-coupled TWC during periodic slightly rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean operation, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. In this work, a passive SCR system was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine to assess NH3 generation over a Pd-only TWC and utilization over a Cu-based SCR catalyst. System NOX reduction efficiency and fuel efficiency improvement compared to stoichiometric engine operation were measured. A feedback control strategy based on cumulative NH3 produced by the TWC during rich operation and NOX emissions during lean operation was implemented on the engine to control lean/rich cycle timing. 15% excess NH3 production over a 1:1 NH3:NOX ratio was required (via longer rich cycle timing) to achieve 99.7% NOX conversion at an SCR average inlet temperature of 350 C. Increasing NH3 generation further resulted in even higher NOX conversion; however, tailpipe NH3 emissions resulted. At higher temperatures, NH3 oxidation becomes important and limits NH3 availability for NOX reduction. At the engine conditions studied here, greater than 99% NOX conversion was achieved with passive SCR while delivering fuel efficiency benefits ranging between 6-11% compared with stoichiometric operation.« less

Lean NOx catalysis for gasoline fueled European cars

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1997-02-01

There is increasing interest in operating gasoline fueled passenger cars lean of the stoichiometric air/fuel (A/F) ratio to improve fuel economy. These types of engines will operate at lean A/F ratios while cruising at partial load, and return to stoichiometric or even rich conditions when more power is required. The challenge for the engine and catalyst manufacturer is to develop a system which will combine the high activity rates of a state-of-the-art three-way catalyst (TWC) with the ability to reduce nitrogen oxides (NOx) in the presence of excess oxygen. The objective is to achieve the future legislative limits (EURO III/IV)more » in the European Union. Recent developments in automotive pollution control catalysis show that the use of NOx adsorption materials is a suitable way to reduce NOx emissions of gasoline-fueled lean-burn engines. However, the primary task for the implementation of this technology in the European market will be to improve the catalyst`s high-temperature stability and to decrease its susceptibility to sulfur poisoning. Outlined here are results of a recent R and D program to achieve NOx reduction under lean-burn gasoline engine conditions. Model gas test results as well as engine bench data are used for discussion of the parameters which control NOx adsorption efficiency under various conditions.« less

The Effect of the Thickness of the Sensitive Layer on the Performance of the Accumulating NOx Sensor

PubMed Central

Groß, Andrea; Richter, Miriam; Kubinski, David J.; Visser, Jacobus H.; Moos, Ralf

2012-01-01

A novel and promising method to measure low levels of NOx utilizes the accumulating sensor principle. During an integration cycle, incoming NOx molecules are stored in a sensitive layer based on an automotive lean NOx trap (LNT) material that changes its electrical resistivity proportional to the amount of stored NOx, making the sensor suitable for long-term detection of low levels of NOx. In this study, the influence of the thickness of the sensitive layer, prepared by multiple screen-printing, is investigated. All samples show good accumulating sensing properties for both NO and NO2. In accordance to a simplified model, the base resistance of the sensitive layer and the sensitivity to NOx decrease with increasing thickness. Contrarily, the sensor response time increases. The linear measurement range of all samples ends at a sensor response of about 30% resulting in an increase of the linearly detectable amount with the thickness. Hence, the variation of the thickness of the sensitive layer is a powerful tool to adapt the linear measurement range (proportional to the thickness) as well as the sensitivity (proportional to the inverse thickness) to the application requirements. Calculations combining the sensor model with the measurement results indicate that for operation in the linear range, about 3% of the LNT material is converted to nitrate.

Low NOx, Lean Direct Wall Injection Combustor Concept Developed

NASA Technical Reports Server (NTRS)

Tacina, Robert R.; Wey, Changlie; Choi, Kyung J.

2003-01-01

The low-emissions combustor development at the NASA Glenn Research Center is directed toward advanced high-pressure aircraft gas turbine applications. The emphasis of this research is to reduce nitrogen oxides (NOx) at high-power conditions and to maintain carbon monoxide and unburned hydrocarbons at their current low levels at low-power conditions. Low-NOx combustors can be classified into rich burn and lean burn concepts. Lean burn combustors can be further classified into lean-premixed-prevaporized (LPP) and lean direct injection (LDI) combustors. In both concepts, all the combustor air, except for liner cooling flow, enters through the combustor dome so that the combustion occurs at the lowest possible flame temperature. The LPP concept has been shown to have the lowest NOx emissions, but for advanced high-pressure-ratio engines, the possibly of autoignition or flashback precludes its use. LDI differs from LPP in that the fuel is injected directly into the flame zone and, thus, does not have the potential for autoignition or flashback and should have greater stability. However, since it is not premixed and prevaporized, the key is good atomization and mixing of the fuel quickly and uniformly so that flame temperatures are low and NOx formation levels are comparable to those of LPP.

Influence of cooled exhaust gas recirculation on performance, emissions and combustion characteristics of LPG fuelled lean burn SI engine

NASA Astrophysics Data System (ADS)

Ravi, K.; Pradeep Bhasker, J.; Alexander, Jim; Porpatham, E.

2017-11-01

On fuel perspective, Liquefied Petroleum Gas (LPG) provides cleaner emissions and also facilitates lean burn signifying less fuel consumption and emissions. Lean burn technology can attain better efficiencies and lesser combustion temperatures but this temperature is quite sufficient to facilitate formation of nitrogen oxide (NOx). Exhaust Gas Recirculation (EGR) for NOx reduction has been considered allover but extremely little literatures exist on the consequence of EGR on lean burn LPG fuelled spark ignition (SI) engine. The following research is carried out to find the optimal rate of EGR addition to reduce NOx emissions without settling on performance and combustion characteristics. A single cylinder diesel engine is altered to operate as LPG fuelled SI engine at a compression ratio of 10.5:1 and arrangements to provide different ratios of cooled EGR in the intake manifold. Investigations are done to arrive at optimum ratio of the EGR to reduce emissions without compromising on performance. Significant reductions in NOx emissions alongside HC and CO emissions were seen. Higher percentages of EGR further diluted the charge and lead to improper combustion and thus increased hydrocarbon emissions. Cooled EGR reduced the peak in-cylinder temperature which reduced NOx emissions but lead to misfire at lower lean limits.

Criteria pollutant and greenhouse gas emissions from CNG transit buses equipped with three-way catalysts compared to lean-burn engines and oxidation catalyst technologies.

PubMed

Yoon, Seungju; Collins, John; Thiruvengadam, Arvind; Gautam, Mridul; Herner, Jorn; Ayala, Alberto

2013-08-01

Engine and exhaust control technologies applied to compressed natural gas (CNG) transit buses have advanced from lean-burn, to lean-burn with oxidation catalyst (OxC), to stoichiometric combustion with three-way catalyst (TWC). With this technology advancement, regulated gaseous and particulate matter emissions have been significantly reduced. Two CNG transit buses equipped with stoichiometric combustion engines and TWCs were tested on a chassis dynamometer, and their emissions were measured. Emissions from the stoichiometric engines with TWCs were then compared to the emissions from lean-burn CNG transit buses tested in previous studies. Stoichiometric combustion with TWC was effective in reducing emissions of oxides of nitrogen (NO(x)), particulate matter (PM), and nonmethane hydrocarbon (NMHC) by 87% to 98% depending on pollutants and test cycles, compared to lean combustion. The high removal efficiencies exceeded the emission reduction required from the certification standards, especially for NO(x) and PM. While the certification standards require 95% and 90% reductions for NO(x) and PM, respectively, from the engine model years 1998-2003 to the engine model year 2007, the measured NO(x) and PM emissions show 96% and 95% reductions, respectively, from the lean-burn engines to the stoichiometric engines with TWC over the transient Urban Dynamometer Driving Schedule (UDDS) cycle. One drawback of stoichiometric combustion with TWC is that this technology produces higher carbon monoxide (CO) emissions than lean combustion. In regard to controlling CO emissions, lean combustion with OxC is more effective than stoichiometric combustion. Stoichiometric combustion with TWC produced higher greenhouse gas (GHG) emissions including carbon dioxide (CO2) and methane (CH4) than lean combustion during the UDDS cycle, but lower GHG emissions during the steady-state cruise cycle. Stoichiometric combustion with three-way catalyst is currently the best emission control technology available for compressed natural gas (CNG) transit buses to meet the stringent U.S. Environmental Protection Agency (EPA) 2010 heavy-duty engine NO(x) emissions standard. For existing lean-burn CNG transit buses in the fleet, oxidation catalyst would be the most effective retrofit technology for the control of NMHC and CO emissions.

Low NOx heavy fuel combustor concept program

NASA Technical Reports Server (NTRS)

White, D. J.; Kubasco, A. J.

1982-01-01

Three simulated coal gas fuels based on hydrogen and carbon monoxide were tested during an experimental evaluation with a rich lean can combustor: these were a simulated Winkler gas, Lurgi gas and Blue Water gas. All three were simulated by mixing together the necessary pure component species, to levels typical of fuel gases produced from coal. The Lurgi gas was also evaluated with ammonia addition. Fuel burning in a rich lean mode was emphasized. Only the Blue Water gas, however, could be operated in such fashion. This showed that the expected NOx signature form could be obtained, although the absolute values of NOx were above the 75 ppm goals for most operating conditions. Lean combustion produced very low NOx well below 75 ppm with the Winkler and Lurgi gases. In addition, these low levels were not significantly impacted by changes in operating conditions.

Model predictive control of a lean-burn gasoline engine coupled with a passive selective catalytic reduction system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Pingen; Lin, Qinghua; Prikhodko, Vitaly Y.

Lean-burn gasoline engines have demonstrated 10–20% engine efficiency gain over stoichiometric engines and are widely considered as a promising technology for meeting the 54.5 miles-per-gallon (mpg) Corporate Average Fuel Economy standard by 2025. Nevertheless, NOx emissions control for lean-burn gasoline for meeting the stringent EPA Tier 3 emission standards has been one of the main challenges towards the commercialization of highly-efficient lean-burn gasoline engines in the United States. Passive selective catalytic reduction (SCR) systems, which consist of a three-way catalyst and SCR, have demonstrated great potentials of effectively reducing NOx emissions for lean gasoline engines but may cause significant fuelmore » penalty due to ammonia generation via rich engine combustion. The purpose of this study is to develop a model-predictive control (MPC) scheme for a lean-burn gasoline engine coupled with a passive SCR system to minimize the fuel penalty associated with passive SCR operation while satisfying stringent NOx and NH3 emissions requirements. Simulation results demonstrate that the MPC-based control can reduce the fuel penalty by 47.7% in a simulated US06 cycle and 32.0% in a simulated UDDS cycle, compared to the baseline control, while achieving over 96% deNOx efficiency and less than 15 ppm tailpipe ammonia slip. The proposed MPC control can potentially enable high engine efficiency gain for highly-efficient lean-burn gasoline engine while meeting the stringent EPA Tier 3 emission standards.« less

Low NOx heavy fuel combustor concept program, phase 1

NASA Technical Reports Server (NTRS)

Cutrone, M. B.

1981-01-01

Combustion tests were completed with seven concepts, including three rich/lean concepts, three lean/lean concepts, and one catalytic combustor concept. Testing was conducted with ERBS petroleum distillate, petroleum residual, and SRC-II coal-derived liquid fuels over a range of operating conditions for the 12:1 pressure ratio General Electric MS7001E heavy-duty turbine. Blends of ERBS and SRC-II fuels were used to vary fuel properties over a wide range. In addition, pyridine was added to the ERBS and residual fuels to vary nitrogen level while holding other fuel properties constant. Test results indicate that low levels of NOx and fuel-bound nitrogen conversion can be achieved with the rich/lean combustor concepts for fuels with nitrogen contents up to 1.0% by weight. Multinozzle rich/lean Concept 2 demonstrated dry low Nox emissions within 10-15% of the EPA New Source Performance Standards goals for SRC-II fuel, with yields of approximately 15%, while meeting program goals for combustion efficiency, pressure drop, and exhaust gas temperature profile. Similar, if not superior, potential was demonstrated by Concept 3, which is a promising rich/lean combustor design.

Compliance of Royal Naval ships with nitrogen oxide emissions legislation.

PubMed

Blatcher, D J; Eames, I

2013-09-15

Nitrogen oxide (NOx) emissions from marine diesel engines pose a hazard to human health and the environment. From 2021, demanding emissions limits are expected to be applied to sea areas that the Royal Navy (RN) accesses. We analyze how these future constraints affect the choice of NOx abatement systems for RN ships, which are subject to more design constraints than civilian ships. A weighted matrix approach is used to facilitate a quantitative assessment. For most warships to be built soon after 2021 Lean Nitrogen Traps (LNT) in conjunction with Exhaust Gas Recirculation (EGR) represents a relatively achievable option with fewer drawbacks than other system types. Urea-selective catalytic reduction is likely to be most appropriate for ships that are built to civilian standards. The future technologies that are at an early stage of development are discussed. Copyright © 2013 Elsevier Ltd. All rights reserved.

Metabolic syndrome and the decreased levels of uric acid by leflunomide favor redox imbalance in patients with rheumatoid arthritis.

PubMed

Costa, Neide Tomimura; Scavuzzi, Bruna Miglioranza; Iriyoda, Tatiana Mayumi Veiga; Lozovoy, Marcell Alysson Batisti; Alfieri, Daniela Frizon; de Medeiros, Fabiano Aparecido; de Sá, Marcelo Cândido; Micheletti, Pâmela Lonardoni; Sekiguchi, Bruno Alexandre; Reiche, Edna Maria Vissoci; Maes, Michael; Simão, Andréa Name Colado; Dichi, Isaias

2018-04-11

Oxidative stress plays a role in the pathophysiology of rheumatoid arthritis (RA). The aim of the present study was to verify the influence of metabolic syndrome (MetS) and disease-modifying antirheumatic drugs on nitrosative and oxidative biomarkers in patients with RA. A total of 177 patients with RA and 150 healthy volunteers participated in this study, which measured lipid hydroperoxides, advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), carbonyl protein, total radical-trapping antioxidant parameter (TRAP), uric acid (UA), and C-reactive protein (CRP). NOx and the NOx/TRAP ratio were significantly increased in RA, while no significant differences in lipid hydroperoxides, AOPP, UA, and TRAP levels were found between both groups. Treatment with leflunomide was associated with increased levels of carbonyl protein, and lowered levels in TRAP and UA, while the NOx/TRAP ratio further increased. NOx and the NOx/TRAP ratio were significantly higher in women than in men, while TRAP and UA were significantly lower in women. MetS was accompanied by increased AOPP and UA levels. RA was best predicted by increased NOx/TRAP ratio, CRP, and BMI. In conclusion, our data demonstrated that NOx and NOx/TRAP are strongly associated with RA physiopathology. Our findings suggest that inhibition of iNOS may become an interesting therapeutic approach for the treatment of RA. In addition, the presence of MetS and a decrease in levels of UA by leflunomide favor redox imbalance in RA patients. More studies are needed to evaluate the impact of antioxidant capacity reduction on RA progression.

Multifuel evaluation of rich/quench/lean combustor

NASA Technical Reports Server (NTRS)

Notardonato, J. J.; Novick, A. S.; Troth, D. L.

1982-01-01

The fuel flexible combustor technology was developed for application to the Model 570-K industrial gas turbine engine. The technology, to achieve emission goals, emphasizes dry NOx reduction methods. Due to the high levels of fuel-bound nitrogen (FBN), control of NOx can be effected through a staged combustor with a rich initial combustion zone. A rich/quench/lean variable geometry combustor utilizes the technology presented to achieve low NOx from alternate fuels containing FBN. The results focus on emissions and durability for multifuel operation.

Low NOx heavy fuel combustor concept program. Phase 1: Combustion technology generation

NASA Astrophysics Data System (ADS)

Lew, H. G.; Carl, D. R.; Vermes, G.; Dezubay, E. A.; Schwab, J. A.; Prothroe, D.

1981-10-01

The viability of low emission nitrogen oxide (NOx) gas turbine combustors for industrial and utility application. Thirteen different concepts were evolved and most were tested. Acceptable performance was demonstrated for four of the combustors using ERBS fuel and ultralow NOx emissions were obtained for lean catalytic combustion. Residual oil and coal derived liquids containing fuel bound nitrogen (FBN) were also used at test fuels, and it was shown that staged rich/lean combustion was effective in minimizing the conversion of FBN to NOx. The rich/lean concept was tested with both modular and integral combustors. While the ceramic lined modular configuration produced the best results, the advantages of the all metal integral burners make them candidates for future development. An example of scaling the laboratory sized combustor to a 100 MW size engine is included in the report as are recommendations for future work.

Low NOx heavy fuel combustor concept program. Phase 1: Combustion technology generation

NASA Technical Reports Server (NTRS)

Lew, H. G.; Carl, D. R.; Vermes, G.; Dezubay, E. A.; Schwab, J. A.; Prothroe, D.

1981-01-01

The viability of low emission nitrogen oxide (NOx) gas turbine combustors for industrial and utility application. Thirteen different concepts were evolved and most were tested. Acceptable performance was demonstrated for four of the combustors using ERBS fuel and ultralow NOx emissions were obtained for lean catalytic combustion. Residual oil and coal derived liquids containing fuel bound nitrogen (FBN) were also used at test fuels, and it was shown that staged rich/lean combustion was effective in minimizing the conversion of FBN to NOx. The rich/lean concept was tested with both modular and integral combustors. While the ceramic lined modular configuration produced the best results, the advantages of the all metal integral burners make them candidates for future development. An example of scaling the laboratory sized combustor to a 100 MW size engine is included in the report as are recommendations for future work.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prikhodko, Vitaly Y; Pihl, Josh A; Toops, Todd J

Ethanol is a very effective reductant of nitrogen oxides (NOX) over silver/alumina (Ag/Al2O3) catalysts in lean exhaust environment. With the widespread availability of ethanol/gasoline-blended fuel in the USA, lean gasoline engines equipped with an Ag/Al2O3 catalyst have the potential to deliver higher fuel economy than stoichiometric gasoline engines and to increase biofuel utilization while meeting exhaust emissions regulations. In this work a pre-commercial 2 wt% Ag/Al2O3 catalyst was evaluated on a 2.0-liter BMW lean burn gasoline direct injection engine for the selective catalytic reduction (SCR) of NOX with ethanol/gasoline blends. The ethanol/gasoline blends were delivered via in-pipe injection upstream ofmore » the Ag/Al2O3 catalyst with the engine operating under lean conditions. A number of engine conditions were chosen to provide a range of temperatures and space velocities for the catalyst performance evaluations. High NOX conversions were achieved with ethanol/gasoline blends containing at least 50% ethanol; however, higher C1/N ratio was needed to achieve greater than 90% NOX conversion, which also resulted in significant HC slip. Temperature and HC dosing were important in controlling selectivity to NH3 and N2O. At high temperatures, NH3 and N2O yields increased with increased HC dosing. At low temperatures, NH3 yield was very low, however, N2O levels became significant. The ability to generate NH3 under lean conditions has potential for application of a dual SCR approach (HC SCR + NH3 SCR) to reduce fuel consumption needed for NOX reduction and/or increased NOX conversion, which is discussed in this work.« less

Low NO sub x heavy fuel combustor concept program phase 1A gas tests

NASA Technical Reports Server (NTRS)

Cutrone, M. B.; Beebe, K. W.; Cutrone, M. B.

1982-01-01

The emissions performance of a rich lean combustor (developed for liquid fuels) for combustion of simulated coal gases ranging in heating value from 167 to 244 Btu/scf were assessed. The 244 Btu/scf gas is typical of the product gas from an oxygen blown gasifier, while the 167 Btu/scf gas is similar to that from an air blown gasifier. Although meeting NOx goals for the 167 Btu/scf gas, NOx performance of the rich lean combustor did not meet program goals with the 244 Btu/scf gas because of high thermal NOx, similar to levels expected from conventional lean burning combustors. The NOx emissions are attributed to inadequate fuel air mixing in the rich stage resulting from the design of the large central fuel nozzle delivering 71% of the total gas flow. NOx generation from NH3 was significant at ammonia concentrations significantly less tha 0.5%. These levels occur depending on fuel gas cleanup system design, However, NOx yield from ammonia injected into the fuel gas decreased rapidly with increasing ammonia level, and is projected to be less than 10% at NH3 levels of 0.5% or higher.

Experimental Assessment of NOx Emissions from 73 Euro 6 Diesel Passenger Cars.

PubMed

Yang, Liuhanzi; Franco, Vicente; Mock, Peter; Kolke, Reinhard; Zhang, Shaojun; Wu, Ye; German, John

2015-12-15

Controlling nitrogen oxides (NOx) emissions from diesel passenger cars during real-world driving is one of the major technical challenges facing diesel auto manufacturers. Three main technologies are available for this purpose: exhaust gas recirculation (EGR), lean-burn NOx traps (LNT), and selective catalytic reduction (SCR). Seventy-three Euro 6 diesel passenger cars (8 EGR only, 40 LNT, and 25 SCR) were tested on a chassis dynamometer over both the European type-approval cycle (NEDC, cold engine start) and the more realistic Worldwide harmonized light-duty test cycle (WLTC version 2.0, hot start) between 2012 and 2015. Most vehicles met the legislative limit of 0.08 g/km of NOx over NEDC (average emission factors by technology: EGR-only 0.07 g/km, LNT 0.04 g/km, and SCR 0.05 g/km), but the average emission factors rose dramatically over WLTC (EGR-only 0.17 g/km, LNT 0.21 g/km, and SCR 0.13 g/km). Five LNT-equipped vehicles exhibited very poor performance over the WLTC, emitting 7-15 times the regulated limit. These results illustrate how diesel NOx emissions are not properly controlled under the current, NEDC-based homologation framework. The upcoming real-driving emissions (RDE) regulation, which mandates an additional on-road emissions test for EU type approvals, could be a step in the right direction to address this problem.

Performance of a Model Rich Burn-quick Mix-lean Burn Combustor at Elevated Temperature and Pressure

NASA Technical Reports Server (NTRS)

Peterson, Christopher O.; Sowa, William A.; Samuelsen, G. S.

2002-01-01

As interest in pollutant emission from stationary and aero-engine gas turbines increases, combustor engineers must consider various configurations. One configuration of increasing interest is the staged, rich burn - quick mix - lean burn (RQL) combustor. This report summarizes an investigation conducted in a recently developed high pressure gas turbine combustor facility. The model RQL combustor was plenum fed and modular in design. The fuel used for this study is Jet-A which was injected from a simplex atomizer. Emission (CO2, CO, O2, UHC, NOx) measurements were obtained using a stationary exit plane water-cooled probe and a traversing water-cooled probe which sampled from the rich zone exit and the lean zone entrance. The RQL combustor was operated at inlet temperatures ranging from 367 to 700 K, pressures ranging from 200 to 1000 kPa, and combustor reference velocities ranging from 10 to 20 m/s. Variations were also made in the rich zone and lean zone equivalence ratios. Several significant trends were observed. NOx production increased with reaction temperature, lean zone equivalence ratio and residence time and decreased with increased rich zone equivalence ratio. NOx production in the model RQL combustor increased to the 0.4 power with increased pressure. This correlation, compared to those obtained for non-staged combustors (0.5 to 0.7), suggests a reduced dependence on NOx on pressure for staged combustors. Emissions profiles suggest that rich zone mixing is not uniform and that the rich zone contributes on the order of 16 percent to the total NOx produced.

Metal/metal oxide doped oxide catalysts having high deNOx selectivity for lean NOx exhaust aftertreatment systems

DOEpatents

Park, Paul W.

2004-03-16

A lean NOx catalyst and method of preparing the same is disclosed. The lean NOx catalyst includes a ceramic substrate, an oxide support material, preferably .gamma.-alumina, deposited on the substrate and a metal promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium, cerium, vanadium, oxides thereof, and combinations thereof. The .gamma.-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between about 80 to 350 m.sup.2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to 0.2 weight percent. In a preferred embodiment the .gamma.-alumina is prepared by a sol-gel method, with the metal doping of the .gamma.-alumina preferably accomplished using an incipient wetness impregnation technique.

Flame Tube NOx Emissions Using a Lean-Direct-Wall-Injection Combustor Concept

NASA Technical Reports Server (NTRS)

Tacina, Robert R.; Wey, Changlie; Choi, Kyung J.

2001-01-01

A low-NOx emissions combustor concept has been demonstrated in flame tube tests. A lean-direct injection concept was used where the fuel is injected directly into the flame zone and the overall fuel-air mixture is lean. In this concept the air is swirled upstream of a venturi section and the fuel is injected radially inward into the air stream from the throat section using a plain-orifice injector. Configurations have two-, four-, or six-wall fuel injectors and in some cases fuel is also injected from an axially located simplex pressure atomizer. Various orifice sizes of the plain-orifice injector were evaluated for the effect on NOx. Test conditions were inlet temperatures up to 8 1 OK, inlet pressures up to 2760 kPa, and flame temperatures up to 2100 K. A correlation is developed relating the NOx emissions to inlet temperature, inlet pressure, fuel-air ratio and pressure drop. Assuming that 15 percent of the combustion air would be used for liner cooling and using an advanced engine cycle, for the best configuration, the NOx emissions using the correlation is estimated to be <75 percent of the 1996 ICAO standard.

Evaluation of advanced combustion concepts for dry NO sub x suppression with coal-derived, gaseous fuels

NASA Technical Reports Server (NTRS)

Beebe, K. W.; Symonds, R. A.; Notardonato, J. J.

1982-01-01

The emissions performance of a rich lean combustor (developed for liquid fuels) was determined for combustion of simulated coal gases ranging in heating value from 167 to 244 Btu/scf (7.0 to 10.3 MJ/NCM). The 244 Btu/scf gas is typical of the product gas from an oxygen blown gasifier, while the 167 Btu/scf gas is similar to that from an air blown gasifier. NOx performance of the rich lean combustor did not meet program goals with the 244 Btu/scf gas because of high thermal NOx, similar to levels expected from conventional lean burning combustors. The NOx emissions are attributed to inadequate fuel air mixing in the rich stage resulting from the design of the large central fuel nozzle delivering 71% of the total gas flow. NOx yield from ammonia injected into the fuel gas decreased rapidly with increasing ammonia level, and is projected to be less than 10% at NH3 levels of 0.5% or higher. NOx generation from NH3 is significant at ammonia concentrations significantly less than 0.5%. These levels may occur depending on fuel gas cleanup system design. CO emissions, combustion efficiency, smoke and other operational performance parameters were satisfactory. A test was completed with a catalytic combustor concept with petroleum distillate fuel. Reactor stage NOx emissions were low (1.4g NOx/kg fuel). CO emissions and combustion efficiency were satisfactory. Airflow split instabilities occurred which eventually led to test termination.

Discovery of Novel NOx Catalysts for CIDI Applications by High-throughput Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blint, Richard J.

DOE project DE-PS26-00NT40758 has developed very active, lean exhaust, NOx reduction catalysts that have been tested on the discovery system, laboratory reactors and engine dynamometer systems. The goal of this project is the development of effective, affordable NOx reduction catalysts for lean combustion engines in the US light duty vehicle market which can meet Tier II emission standards with hydrocarbons based reductants for reducing NOx. General Motors (prime contractor) along with subcontractors BASF (Engelhard) (a catalytic converter developer) and ACCELRYS (an informatics supplier) carried out this project which began in August of 2002. BASF (Engelhard) has run over 16,000 testsmore » of 6100 possible catalytic materials on a high throughput discovery system suitable for automotive catalytic materials. Accelrys developed a new database informatics system which allowed material tracking and data mining. A program catalyst was identified and evaluated at all levels of the program. Dynamometer evaluations of the program catalyst both with and without additives show 92% NOx conversions on the HWFET, 76% on the US06, 60% on the cold FTP and 65% on the Set 13 heavy duty test using diesel fuel. Conversions of over 92% on the heavy duty FTP using ethanol as a second fluid reductant have been measured. These can be competitive with both of the alternative lean NOx reduction technologies presently in the market. Conversions of about 80% were measured on the EUDC for lean gasoline applications without using active dosing to adjust the C:N ratio for optimum NOx reduction at all points in the certification cycle. A feasibility analysis has been completed and demonstrates the advantages and disadvantages of the technology using these materials compared with other potential technologies. The teaming agreements among the partners contain no obstacles to commercialization of new technologies to any potential catalyst customers.« less

Development of Diesel Exhaust Aftertreatment System for Tier II Emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, R. C.; Cole, A. S., Stroia, B. J.; Huang, S. C.

2002-06-01

Due to their excellent fuel efficiency, reliability, and durability, compression ignition direct injection (CIDI) engines have been used extensively to power almost all highway trucks, urban buses, off-road vehicles, marine carriers, and industrial equipment. CIDI engines burn 35 to 50% less fuel than gasoline engines of comparable size, and they emit far less greenhouse gases (Carbon Dioxides), which have been implicated in global warming. Although the emissions of CIDI engines have been reduced significantly over the last decade, there remains concern with the Nitrogen Oxides (NOX) and Particulate Matter (PM) emission levels. In 2000, the US EPA proposed very stringentmore » emissions standards to be introduced in 2007 along with low sulfur (< 15ppm) diesel fuel. The California Air Resource Board (CARB) has also established the principle that future diesel fueled vehicles should meet the same emissions standards as gasoline fueled vehicles and the EPA followed suit with its Tier II emissions regulations. Meeting the Tier II standards requires NOX and PM emissions to be reduced dramatically. Achieving such low emissions while minimizing fuel economy penalty cannot be done through engine development and fuel reformulation alone, and requires application of NOX and PM aftertreatment control devices. A joint effort was made between Cummins Inc. and the Department of Energy to develop the generic aftertreatment subsystem technologies applicable for Light-Duty Vehicle (LDV) and Light-Duty Truck (LDT) engines. This paper provides an update on the progress of this joint development program. Three NOX reduction technologies including plasmaassisted catalytic NOX reduction (PACR), active lean NOX catalyst (LNC), and adsorber catalyst (AC) technology using intermittent rich conditions for NOX reduction were investigated in parallel in an attempt to select the best NOX control approach for light-duty aftertreatment subsystem integration and development. Investigations included system design and analysis, critical lab/engine experiments, and ranking then selection of NOX control technologies against reliability, up-front cost, fuel economy, service interval/serviceability, and size/weight. The results of the investigations indicate that the best NOX control approach for LDV and LDT applications is a NOX adsorber system. A greater than 83% NOX reduction efficiency is required to achieve 0.07g/mile NOX Tier II vehicle-out emissions. Both active lean NOX and PACR technology are currently not capable of achieving the high conversion efficiency required for Tier II, Bin 5 emissions standards. In this paper, the NOX technology assessment and selection is first reviewed and discussed. Development of the selected NOX technology (NOX adsorber) and PM control are then discussed in more detail. Discussion includes exhaust sulfur management, further adsorber formulation development, reductant screening, diesel particulate filter development & active regeneration, and preliminary test results on the selected integrated SOX trap, NOX adsorber, and diesel particulate filter system over an FTP-75 emissions cycle, and its impact on fuel economy. Finally, the direction of future work for continued advanced aftertreatment technology development is discussed. (SAE Paper SAE-2002-01-1867 © 2002 SAE International. This paper is published on this website with permission from SAE International. As a user of this website, you are permitted to view this paper on-line, download this pdf file and print one copy of this paper at no cost for your use only. The downloaded pdf file and printout of this SAE paper may not be copied, distributed or forwarded to others or for the use of others.)« less

Lean mixture engine testing and evaluation program. [for automobile engine pollution and fuel performances

NASA Technical Reports Server (NTRS)

Dowdy, M. W.; Hoehn, F. W.; Griffin, D. C.

1975-01-01

Experimental results for fuel consumption and emissions are presented for a 350 CID (5.7 liter) Chevrolet V-8 engine modified for lean operation with gasoline. The lean burn engine achieved peak thermal efficiency at an equivalence ratio of 0.75 and a spark advance of 60 deg BTDC. At this condition the lean burn engine demonstrated a 10% reduction in brake specific fuel consumption compared with the stock engine; however, NOx and hydrocarbon emissions were higher. With the use of spark retard and/or slightly lower equivalence ratios, the NOx emissions performance of the stock engine was matched while showing a 6% reduction in brake specific fuel consumption. Hydrocarbon emissions exceeded the stock values in all cases. Diagnostic data indicate that lean performance in the engine configuration tested is limited by ignition delay, cycle-to-cycle pressure variations, and cylinder-to-cylinder distribution.

The Effect of Air Preheat at Atmospheric Pressure on the Formation of NO(x) in the Quick-Mix Sections of an Axially Staged Combustor

NASA Technical Reports Server (NTRS)

Vardakas, M. A.; Leong, M. Y.; Brouwer, J.; Samuelsen, G. S.; Holdeman, J. D.

1999-01-01

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of nitrogen oxides (NO(x)) in gas turbine systems. The success of this combustor strategy is dependent upon the efficiency of the mixing section bridging the fuel-rich and fuel-lean stages. Note that although these results were obtained from an experiment designed to study an RQL mixer, the link between mixing and NOx signatures is considerably broader than this application, in that the need to understand this link exists in most advanced combustors. The experiment reported herein was designed to study the effects of inlet air temperature on NO(x) formation in a mixing section. The results indicate that NO(x) emission is increased for all preheated cases compared to non-preheated cases. When comparing the various mixing modules, the affect of jet penetration is important, as this determines where NO(x) concentrations peak, and affects overall NO(x) production. Although jet air comprises 70 percent of the total airflow, the impact that jet air preheat has on overall NO(x) emissions is small compared to preheating both main and jet air flow.

Real-Time Control of Lean Blowout in a Turbine Engine for Minimizing No(x) Emissions

NASA Technical Reports Server (NTRS)

Zinn, Ben

2004-01-01

This report describes research on the development and demonstration of a controlled combustor operates with minimal NO, emissions, thus meeting one of NASA s UEET program goals. NO(x) emissions have been successfully minimized by operating a premixed, lean burning combustor (modeling a lean prevaporized, premixed LPP combustor) safely near its lean blowout (LBO) limit over a range of operating conditions. This was accomplished by integrating the combustor with an LBO precursor sensor and closed-loop, rule-based control system that allowed the combustor to operate far closer to the point of LBO than an uncontrolled combustor would be allowed to in a current engine. Since leaner operation generally leads to lower NO, emissions, engine NO, was reduced without loss of safety.

Experimental Assessment of the Emissions Control Potential of a Rich/Quench/Lean Combustor for High Speed Civil Transport Aircraft Engines

NASA Technical Reports Server (NTRS)

Rosfjord, T. J.; Padget, F. C.; Tacina, Robert R. (Technical Monitor)

2001-01-01

In support of Pratt & Whitney efforts to define the Rich burn/Quick mix/Lean burn (RQL) combustor for the High Speed Civil Transport (HSCT) aircraft engine, UTRC conducted a flametube-scale study of the RQL concept. Extensive combustor testing was performed at the Supersonic Cruise (SSC) condition of a HSCT engine cycle, Data obtained from probe traverses near the exit of the mixing section confirmed that the mixing section was the critical component in controlling combustor emissions. Circular-hole configurations, which produced rapidly-, highly-penetrating jets, were most effective in limiting NOx. The spatial profiles of NOx and CO at the mixer exit were not directly interpretable using a simple flow model based on jet penetration, and a greater understanding of the flow and chemical processes in this section are required to optimize it. Neither the rich-combustor equivalence ratio nor its residence time was a direct contributor to the exit NOx. Based on this study, it was also concluded that (1) While NOx formation in both the mixing section and the lean combustor contribute to the overall emission, the NOx formation in the mixing section dominates. The gas composition exiting the rich combustor can be reasonably represented by the equilibrium composition corresponding to the rich combustor operating condition. Negligible NOx exits the rich combustor. (2) At the SSC condition, the oxidation processes occurring in the mixing section consume 99 percent of the CO exiting the rich combustor. Soot formed in the rich combustor is also highly oxidized, with combustor exit SAE Smoke Number <3. (3) Mixing section configurations which demonstrated enhanced emissions control at SSC also performed better at part-power conditions. Data from mixer exit traverses reflected the expected mixing behavior for off-design jet to crossflow momentum-flux ratios. (4) Low power operating conditions require that the RQL combustor operate as a lean-lean combustor to achieve low CO and high efficiency. (5) A RQL combustor can achieve the emissions goal of EINOX = 5 at the Supersonic Cruise operating condition for a HSCT engine.

Experimental Assessment of the Emissions Control Potential of a Rich/Quench/ Lean Combustor for High Speed Civil Transport Aircraft Engines

NASA Technical Reports Server (NTRS)

Tacina, Robert R. (Technical Monitor); Rosfjord, T. J.; Padget, F. C.

2001-01-01

In support of Pratt & Whitney efforts to define the Rich burn/Quick mix/Lean burn (RQL) combustor for the High Speed Civil Transport (HSCT) aircraft engine, UTRC conducted a flametube-scale study of the RQL concept. Extensive combustor testing was performed at the Supersonic Cruise (SSC) condition of an HSCT engine cycle. Data obtained from probe traverses near the exit of the mixing section confirmed that the mixing section was the critical component in controlling combustor emissions. Circular-hole configurations, which produced rapidly-, highly-penetrating jets, were most effective in limiting NO(x). The spatial profiles of NO(x) and CO at the mixer exit were not directly interpretable using a simple flow model based on jet penetration, and a greater understanding of the flow and chemical processes in this section are required to optimize it. Neither the rich-combustor equivalence ratio nor its residence time was a direct contributor to the exit NO(x). Based on this study, it was also concluded that: (1) While NO(x) formation in both the mixing section and the lean combustor contribute to the overall emission, the NOx formation in the mixing section dominates. The gas composition exiting the rich combustor can be reasonably represented by the equilibrium composition corresponding to the rich combustor operating condition. Negligible NO(x) exits the rich combustor. (2) At the SSC condition, the oxidation processes occurring in the mixing section consume 99 percent of the CO exiting the rich combustor. Soot formed in the rich combustor is also highly oxidized, with combustor exit SAE Smoke Number <3. (3) Mixing section configurations which demonstrated enhanced emissions control at SSC also performed better at part-power conditions. Data from mixer exit traverses reflected the expected mixing behavior for off-design jet to crossflow momentum-flux ratios. (4) Low power operating conditions require that the RQL combustor operate as a lean-lean combustor to achieve low CO and high efficiency. (5) An RQL combustor can achieve the emissions goal of EINO(x) = 5 at the Supersonic Cruise operating condition for an HSCT engine.

LeRC in-house experimental research

NASA Technical Reports Server (NTRS)

Lyons, Valerie J.

1992-01-01

The topics covered include the following: LeRC in-house experimental research; combustion concepts; schedule for in-house experiments; lean premixed prevaporized combustion; comparisons of low NO(x) lean premixed/prevaporized data; rich burn/quick quench/lean burn (RQL); RQL combustion; fuel rich catalytic combustion; advanced diagnostics; and ceramic matrix liner test rig.

Fuel-Air Mixing Effect on Nox Emissions for a Lean Premixed-Prevaporized Combustion System

NASA Technical Reports Server (NTRS)

Lee, Chi-Ming; Chun, Kue S.; Locke, Randy J.

1995-01-01

The lean premixed-prevaporized (LPP) concept effectively meets low nitrogen oxides (NOx) emission requirements for combustors with the high inlet temperature and pressure typical of the High-Speed Civil Transport (HSCT). For the LPP system fuel-air mixture uniformity is probably the most important factor for low NOx emissions. Previous studies have suggested that the fuel-air mixture uniformity can be severely affected by changing the number and configuration of fuel injection points. Therefore, an experimental study was performed to determine how the number of fuel injection points and their arrangement affect NOx emissions from an LPP system. The NOx emissions were measured by a gas-sampling probe in a flame-tube rig at the following conditions: inlet temperature of 810 K (1000 F), rig pressure of 10 atm, reference velocity of 150 ft/s, and residence time near 0.005 s. Additionally, a focused Schlieren diagnostic technique coupled with a high speed camera was used to provide a qualitative description of the spatial flow field.

Effect of an alternating electric field on the polluting emission from propane flame.

NASA Astrophysics Data System (ADS)

Ukradiga, I.; Turlajs, D.; Purmals, M.; Barmina, I.; Zake, M.

2001-12-01

The experimental investigations of the AC field effect on the propane combustion and processes that cause the formation of polluting emissions (NO_x, CO, CO_2) are performed. The AC-enhanced variations of the temperature and composition of polluting emissions are studied for the fuel-rich and fuel-lean conditions of the flame core. The results show that the AC field-enhanced mixing of the fuel-rich core with the surrounding air coflow enhances the propane combustion with increase in the mass fraction of NO_x and CO_2 in the products. The reverse field effect on the composition of polluting emissions is observed under the fuel-lean conditions in the flame core. The field-enhanced CO_2 destruction is registered when the applied voltage increase. The destruction of CO_2 leads to a correlating increase in the mass fraction of CO in the products and enhances the process of NO_x formation within the limit of the fuel lean and low temperature combustion. Figs 11, Refs 18.

Apparatus and method for burning a lean, premixed fuel/air mixture with low NOx emission

DOEpatents

Kostiuk, Larry W.; Cheng, Robert K.

1996-01-01

An apparatus for enabling a burner to stably burn a lean fuel/air mixture. The burner directs the lean fuel/air mixture in a stream. The apparatus comprises an annular flame stabilizer; and a device for mounting the flame stabilizer in the fuel/air mixture stream. The burner may include a body having an internal bore, in which case, the annular flame stabilizer is shaped to conform to the cross-sectional shape of the bore, is spaced from the bore by a distance greater than about 0.5 mm, and the mounting device mounts the flame stabilizer in the bore. An apparatus for burning a gaseous fuel with low NOx emissions comprises a device for premixing air with the fuel to provide a lean fuel/air mixture; a nozzle having an internal bore through which the lean fuel/air mixture passes in a stream; and a flame stabilizer mounted in the stream of the lean fuel/air mixture. The flame stabilizer may be mounted in the internal bore, in which case, it is shaped and is spaced from the bore as just described. In a method of burning a lean fuel/air mixture, a lean fuel/air mixture is provided, and is directed in a stream; an annular eddy is created in the stream of the lean fuel/air mixture; and the lean fuel/air mixture is ignited at the eddy.

Lean burn natural gas fueled S.I. engine and exhaust emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varde, K.S.; Patro, N.; Drouillard, K.

1995-12-31

An experimental study was undertaken to study exhaust emission from a lean-burn natural gas spark ignition engine. The possibility that such an engine may help to reduce exhaust emissions substantially by taking advantage of natural gas fuel properties, such as its antiknock properties and extended lean flammability limit compared to gasoline, was the main motivation behind the investigation. A four cylinder, automotive type spark ignition engine was used in the investigation. The engine was converted to operate on natural gas by replacing its fuel system with a gaseous carburetion system. A 3-way metal metrix catalytic converter was used in themore » engine exhaust system to reduce emission levels. The engine operated satisfactorily at an equivalence ratio as lean as 0.6, at all speeds and loads. As a result NOx emissions were significantly reduced. However, hydrocarbon emissions were high, particularly at very lean conditions and light loads. Most of these hydrocarbons were made up of methane with small concentrations of ethane and propane. Coefficient of variations in hydrocarbons were generally high at very lean operating conditions and light loads, but decreased with increasing equivalence ratio and engine speed. Methane concentrations in the engine exhaust decreased with increasing load and equivalence ratio. At lean air-to-fuel ratios and light loads oxidation of methane in the catalyst was substantially limited and no NOx reduction was achieved. In addition, the proportion of nitric oxide in oxides of nitrogen increased with increasing amount of NOx in the engine exhaust. A major problem encountered in the study was the inability of the fuel system to maintain near constant air-to-fuel ratios at steady operating conditions.« less

Hydrogen enrichment for low-emission jet combustion

NASA Technical Reports Server (NTRS)

Clayton, R. M.

1978-01-01

Simultaneous gaseous pollutant emission indexes (g pollutant/kg fuel) for a research combustor with inlet air at 120,900 N/sq m (11.9 atm) pressure and 727 K (849 F) temperature are as low as 1.0 for NOx and CO and 0.5 for unburned HC. Emissions data are presented for hydrogen/jet fuel (JP-5) mixes and for jet fuel only for premixed equivalence ratios from lean blowout to 0.65. Minimized emissions were achieved at an equivalence ratio of 0.38 using 10-12 mass percent hydrogen in the total fuel to depress the lean blowout limit. They were not achievable with jet fuel alone because of the onset of lean blowout at an equivalence ratio too high to reduce the NOx emission sufficiently.

Effect of fuel-air-ratio nonuniformity on emissions of nitrogen oxides

NASA Technical Reports Server (NTRS)

Lyons, V. J.

1981-01-01

The inlet fuel-air ratio nonuniformity is studied to deterine how nitrogen oxide (NOx) emissions are affected. An increase in NOx emissions with increased fuel-air ratio nonuniformity for average equivalence ratios less than 0.7 and a decrease in NOx emissions for average equivalence ratios near stoichiometric is predicted. The degree of uniformityy of fuel-air ratio profiles that is necessary to achieve NOx emissions goals for actual engines that use lean, premixed, prevaporized combustion systems is determined.

Systems and methods for controlling diesel engine emissions

DOEpatents

Webb, Cynthia Chaffin; Weber, Phillip Anthony; Khair, Magdi K.

2004-06-01

Systems and methods for controlling diesel engine emissions, including, for example, oxides of nitrogen emissions, particulate matter emissions, and the like. The emission control system according to this invention is provided in the exhaust passageway of a diesel engine and includes a catalyst-based particulate filter; and first and second lean NO.sub.x trap systems coupled to the catalyst-based particulate filter. The first and second lean NO.sub.x trap systems are arranged in a parallel flow configuration with each other. Each of the first and second lean NO.sub.x trap systems include a carbon monoxide generating catalyst device, a sulfur trap device, a lean NO.sub.x device, a supplemental fuel injector device, and a plurality of flow diverter devices.

A Low NO(x) Lean-Direct Injection, Multipoint Integrated Module Combuster Concept for Advanced Aircraft Gas Turbines

NASA Technical Reports Server (NTRS)

Tacina, Robert; Wey, Changlie; Laing, Peter; Mansour, Adel

2002-01-01

A low NO(x) emissions combustor has been demonstrated in flame-tube tests. A multipoint, lean-direct injection concept was used. Configurations were tested that had 25- and 36- fuel injectors in the size of a conventional single fuel injector. An integrated-module approach was used for the construction where chemically etched laminates, diffusion bonded together, combine the fuel injectors, air swirlers and fuel manifold into a single element. Test conditions were inlet temperatures up to 810 K, inlet pressures up to 2760 kPa, and flame temperatures up to 2100 K. A correlation was developed relating the NO(x) emissions with the inlet temperature, inlet pressure, fuel-air ratio and pressure drop. Assuming that 10 percent of the combustion air would be used for liner cooling and using a hypothetical engine cycle, the NO(x) emissions using the correlation from flame-tube tests were estimated to be less than 20 percent of the 1996 ICAO standard.

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigel N. Clark

Nitric oxide (NO) and nitrogen dioxide (NO2) generated by internal combustion (IC) engines are implicated in adverse environmental and health effects. Even though lean-burn natural gas engines have traditionally emitted lower oxides of nitrogen (NOx) emissions compared to their diesel counterparts, natural gas engines are being further challenged to reduce NOx emissions to 0.1 g/bhp-hr. The Selective NOx Recirculation (SNR) approach for NOx reduction involves cooling the engine exhaust gas and then adsorbing the NOx from the exhaust stream, followed by the periodic desorption of NOx. By sending the desorbed NOx back into the intake and through the engine, amore » percentage of the NOx can be decomposed during the combustion process. SNR technology has the support of the Department of Energy (DOE), under the Advanced Reciprocating Engine Systems (ARES) program to reduce NOx emissions to under 0.1 g/bhp-hr from stationary natural gas engines by 2010. The NO decomposition phenomenon was studied using two Cummins L10G natural gas fueled spark-ignited (SI) engines in three experimental campaigns. It was observed that the air/fuel ratio ({lambda}), injected NO quantity, added exhaust gas recirculation (EGR) percentage, and engine operating points affected NOx decomposition rates within the engine. Chemical kinetic model predictions using the software package CHEMKIN were performed to relate the experimental data with established rate and equilibrium models. The model was used to predict NO decomposition during lean-burn, stoichiometric burn, and slightly rich-burn cases with added EGR. NOx decomposition rates were estimated from the model to be from 35 to 42% for the lean-burn cases and from 50 to 70% for the rich-burn cases. The modeling results provided an insight as to how to maximize NOx decomposition rates for the experimental engine. Results from this experiment along with chemical kinetic modeling solutions prompted the investigation of rich-burn operating conditions, with added EGR to prevent preignition. It was observed that the relative air/fuel ratio, injected NO quantity, added EGR fraction, and engine operating points affected the NO decomposition rates. While operating under these modified conditions, the highest NO decomposition rate of 92% was observed. In-cylinder pressure data gathered during the experiments showed minimum deviation from peak pressure as a result of NO injections into the engine. A NOx adsorption system, from Sorbent Technologies, Inc., was integrated with the Cummins engine, comprised a NOx adsorbent chamber, heat exchanger, demister, and a hot air blower. Data were gathered to show the possibility of NOx adsorption from the engine exhaust, and desorption of NOx from the sorbent material. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a benchtop adsorption system was constructed. The temperature of this apparatus was controlled while data were gathered on the characteristics of the sorbent material for development of a system model. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passed over fresh sorbent material. A mass heat transfer analysis was conducted to analyze the possibility of using hot exhaust gas for the desorption process. It was found in the adsorption studies, and through literature review, that NO adsorption was poor when the carrier gas was nitrogen, but that NO in the presence of oxygen was adsorbed at levels exceeding 1% by mass of the sorbent. From the three experimental campaigns, chemical kinetic modeling analysis, and the scaled benchtop NOx adsorption system, an overall SNR system model was developed. An economic analysis was completed, and showed that the system was impractical in cost for small engines, but that economies of scale favored the technology.« less

Simultaneous NOx and hydrocarbon emissions control for lean-burn engines using low-temperature solid oxide fuel cell at open circuit.

PubMed

Huang, Ta-Jen; Hsu, Sheng-Hsiang; Wu, Chung-Ying

2012-02-21

The high fuel efficiency of lean-burn engines is associated with high temperature and excess oxygen during combustion and thus is associated with high-concentration NO(x) emission. This work reveals that very high concentration of NO(x) in the exhaust can be reduced and hydrocarbons (HCs) can be simultaneously oxidized using a low-temperature solid oxide fuel cell (SOFC). An SOFC unit is constructed with Ni-YSZ as the anode, YSZ as the electrolyte, and La(0.6)Sr(0.4)CoO(3) (LSC)-Ce(0.9)Gd(0.1)O(1.95) as the cathode, with or without adding vanadium to LSC. SOFC operation at 450 °C and open circuit can effectively treat NO(x) over the cathode at a very high concentration in the simulated exhaust. Higher NO(x) concentration up to 5000 ppm can result in a larger NO(x) to N(2) rate. Moreover, a higher oxygen concentration promotes NO conversion. Complete oxidation of HCs can be achieved by adding silver to the LSC current collecting layer. The SOFC-based emissions control system can treat NO(x) and HCs simultaneously, and can be operated without consuming the anode fuel (a reductant) at near the engine exhaust temperature to eliminate the need for reductant refilling and extra heating.

NOx results from two combustors tested on medium BTU coal gas

NASA Technical Reports Server (NTRS)

Sherlock, T. P.; Carl, D. E.; Vermes, G.; Schwab, J.; Notardonato, J. J.

1982-01-01

The results of tests of two combustor configurations using coal gas from a 25 ton/day fluidized bed coal gasifier are reported. The trials were run with a ceramic-lined, staged rich/lean burner and an integral, all metal multiannular swirl burner (MASB) using a range of temperatures and pressures representative of industrial turbine inlet conditions. A lean mixture was examined at 104, 197, and 254 Btu/Scf, yielding NO(x) emissions of 5, 20, and 70 ppmv, respectively. The MASB was employed only with a gas rated at 220-270 Btu/Scf, producing 80 ppmv NO(x) at rated engine conditions. The results are concluded to be transferrable to current machines. Further tests on the effects of gas composition, the scaling of combustors to utility size, and the development of improved wall cooling techniques and variable geometry are indicated.

Nitric oxide formation in a lean, premixed-prevaporized jet A/air flame tube: An experimental and analytical study

NASA Technical Reports Server (NTRS)

Lee, Chi-Ming; Bianco, Jean; Deur, John M.; Ghorashi, Bahman

1992-01-01

An experimental and analytical study was performed on a lean, premixed-prevaporized Jet A/air flame tube. The NO(x) emissions were measured in a flame tube apparatus at inlet temperatures ranging from 755 to 866 K (900 to 1100 F), pressures from 10 to 15 atm, and equivalence ratios from 0.37 to 0.62. The data were then used in regressing an equation to predict the NO(x) production levels in combustors of similar design. Through an evaluation of parameters it was found that NO(x) is dependent on adiabatic flame temperature and combustion residence time, yet independent of pressure and inlet air temperature for the range of conditions studied. This equation was then applied to experimental data that were obtained from the literature, and a good correlation was achieved.

Microvascular Endothelial Dysfunction in Sedentary, Obese Humans is mediated by NADPH Oxidase; Influence of Exercise Training

PubMed Central

La Favor, Justin D.; Dubis, Gabriel S.; Yan, Huimin; White, Joseph D.; Nelson, Margaret A.M.; Anderson, Ethan J.; Hickner, Robert C.

2016-01-01

Objective The objectives of this study were to determine the impact of in vivo reactive oxygen species (ROS) on microvascular endothelial function in obese human subjects and to determine the efficacy of an aerobic exercise intervention on alleviating obesity-associated dysfunctionality. Approach and Results Young, sedentary men and women were divided into lean (BMI 18–25; n=14), intermediate (BMI 28–32.5; n=13), and obese (BMI 33–40; n=15) groups. A novel microdialysis technique was utilized to detect elevated interstitial hydrogen peroxide (H2O2) and superoxide levels in the vastus lateralis of obese compared to both lean and intermediate subjects. Nutritive blood flow was monitored in the vastus lateralis via the microdialysis-ethanol technique. A decrement in acetylcholine-stimulated blood flow revealed impaired microvascular endothelial function in the obese subjects. Perfusion of apocynin, an NADPH oxidase (Nox) inhibitor, lowered (normalized) H2O2 and superoxide levels and reversed microvascular endothelial dysfunction in obese subjects. Following 8-weeks of exercise, H2O2 levels were decreased in the obese subjects and microvascular endothelial function in these subjects was restored to levels similar to lean subjects. Skeletal muscle protein expression of the Nox subunits p22phox, p47phox, and p67phox were increased in obese relative to lean subjects, where p22phox and p67phox expression was attenuated by exercise training in obese subjects. Conclusions This study implicates Nox as a source of excessive ROS production in skeletal muscle of obese individuals, and links excessive Nox derived ROS to microvascular endothelial dysfunction in obesity. Furthermore, aerobic exercise training proved to be an effective strategy for alleviating these maladies. PMID:27765769

Multifuel evaluation of rich/quench/lean combustor

NASA Technical Reports Server (NTRS)

Novick, A. S.; Troth, D. L.; Notardonato, J.

1982-01-01

Test results on the RQL low NO(x) industrial gas turbine engine are reported. The air-staged combustor comprises an initial rich burning zone, followed by a quench zone, and a lean reaction and dilution zone. The combustor was tested as part of the DoE/NASA program to define the technology for developing a durable, low-emission gas turbine combustor capable of operation with minimally processed petroleum residual, synthetic, or low/mid-heating value gaseous fuels. The properties of three liquid and two gaseous fuels burned in the combustor trials are detailed. The combustor featured air staging, variable geometry, and generative/convective cooling. The lean/rich mixtures could be varied in zones simultaneously or separately while maintaining a specified pressure drop. Low NO(x) and smoke emissions were produced with each fuel burned, while high combustor efficiencies were obtained.

Sector Tests of a Low-NO(sub x), Lean, Direct- Injection, Multipoint Integrated Module Combustor Concept Conducted

NASA Technical Reports Server (NTRS)

Tacina, Robert R.; Wey, Chang-Lie; Laing, Peter; Mansour, Adel

2002-01-01

The low-emissions combustor development described is directed toward advanced high pressure aircraft gas-turbine applications. The emphasis of this research is to reduce nitrogen oxides (NOx) at high-power conditions and to maintain carbon monoxide and unburned hydrocarbons at their current low levels at low power conditions. Low-NOx combustors can be classified into rich-burn and lean-burn concepts. Lean-burn combustors can be further classified into lean-premixed-prevaporized (LPP) and lean direct injection (LDI) concepts. In both concepts, all the combustor air, except for liner cooling flow, enters through the combustor dome so that the combustion occurs at the lowest possible flame temperature. The LPP concept has been shown to have the lowest NOx emissions, but for advanced high-pressure-ratio engines, the possibility of autoignition or flashback precludes its use. LDI differs from LPP in that the fuel is injected directly into the flame zone, and thus, it does not have the potential for autoignition or flashback and should have greater stability. However, since it is not premixed and prevaporized, good atomization is necessary and the fuel must be mixed quickly and uniformly so that flame temperatures are low and NOx formation levels are comparable to those of LPP. The LDI concept described is a multipoint fuel injection/multiburning zone concept. Each of the multiple fuel injectors has an air swirler associated with it to provide quick mixing and a small recirculation zone for burning. The multipoint fuel injection provides quick, uniform mixing and the small multiburning zones provide for reduced burning residence time, resulting in low NOx formation. An integrated-module approach was used for the construction where chemically etched laminates, diffusion bonded together, combine the fuel injectors, air swirlers, and fuel manifold into a single element. The multipoint concept combustor was demonstrated in a 15 sector test. The configuration tested had 36 fuel injectors and fuel-air mixers that replaced two fuel injectors in a conventional dual-annular combustor. During tests, inlet temperatures were up to 870 K and inlet pressures were up to 5400 kPa. A correlation was developed that related the NOx emissions with the inlet temperature, inlet pressure, fuel-air ratio, and pressure drop. At low-power conditions, fuel staging was used so that high combustion efficiency was obtained with only one-fourth of the fuel injectors flowing. The test facility had optical access, and visual images showed the flame to be very short, approximately 25 mm long.

Recent advances in automotive catalysis for NOx emission control by small-pore microporous materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beale, Andrew M.; Gao, Feng; Lezcano-Gonzalez, Ines

The ever increasing demand to develop highly fuel efficient engines coincides with the need to minimize air pollution originating from the exhaust gases of internal combustion engines. Dramatically improved fuel efficiency can be achieved at air-to-fuel ratios much higher than stoichiometric. In the presence of oxygen in large excess, however, traditional three-way catalysts are unable to reduce NOx. Among the number of lean-NOx reduction technologies, selective catalytic reduction (SCR) of NOx by NH3 over Cu- and Fe-ion exchanged zeolite catalysts has been extensively studied over the past 30+ years. Despite the significant advances in developing a viable practical zeolite-based catalystmore » for lean NOx reduction, the insufficient hydrothermal stabilities of the zeolite structures considered cast doubts about their real-world applicability. During the past decade a renewed interest in zeolite-based lean NOx reduction was spurred by the discovery of the very high activity of Cu-SSZ-13 (and the isostructural Cu-SAPO-34) in the NH3 SCR of NOx. These new, small-pore zeolite-based catalysts not only exhibited very high NOx conversion and N2 selectivity, but also exhibited exceptional high hydrothermal stability at high temperatures. In this review we summarize the key discoveries of the past ~5 years that lead to the introduction of these catalysts into practical application. The review first briefly discusses the structure and preparation of the CHA structure-based zeolite catalysts, and then summarizes the key learnings of the rather extensive (but not complete) characterisation work. Then we summarize the key findings of reaction kinetics studies, and provide some mechanistic details emerging from these investigations. At the end of the review we highlight some of the issues that are still need to be addressed in automotive exhaust control catalysis. Funding A.M.B. and I.L.G. would like to thank EPSRC for funding. F.G., C.H.F.P. and J.Sz. gratefully acknowledge financial support from the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program.« less

Effects of sulfation level on the desulfation behavior of pre-sulfated Pt BaO/Al2O3 lean NOx trap catalysts: a combined H2 Temperature-Programmed Reaction, in-situ sulfur K-edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Do Heui; Szanyi, Janos; Kwak, Ja Hun

2009-04-03

Desulfation by hydrogen of pre-sulfated Pt(2wt%) BaO(20wt%)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31 and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), x-ray photoelectron spectroscopy (XPS), in-situ sulfur K-edge x-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved x-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in-situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phase and remained in the catalyst, rathermore » than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.« less

Simulating the Impact of Premixed Charge Compression Ignition on Light-Duty Diesel Fuel Economy and Emissions of Particulates and NOx

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Zhiming; Daw, C Stuart; Wagner, Robert M

2013-01-01

We utilize the Powertrain Systems Analysis Toolkit (PSAT) combined with transient engine and aftertreatment component models implemented in Matlab/Simulink to simulate the effect of premixed charge compression ignition (PCCI) on the fuel economy and emissions of light-duty diesel-powered conventional and hybrid electric vehicles (HEVs). Our simulated engine is capable of both conventional diesel combustion (CDC) and premixed charge compression ignition (PCCI) over real transient driving cycles. Our simulated aftertreatment train consists of a diesel oxidation catalyst (DOC), lean NOx trap (LNT), and catalyzed diesel particulate filter (DPF). The results demonstrate that, in the simulated conventional vehicle, PCCI can significantly reducemore » fuel consumption and emissions by reducing the need for LNT and DPF regeneration. However, the opportunity for PCCI operation in the simulated HEV is limited because the engine typically experiences higher loads and multiple stop-start transients that are outside the allowable PCCI operating range. Thus developing ways of extending the PCCI operating range combined with improved control strategies for engine and emissions control management will be especially important for realizing the potential benefits of PCCI in HEVs.« less

Experimental study of the effect of cycle pressure on lean combustion emissions

NASA Technical Reports Server (NTRS)

Roffe, G.; Venkataramani, K. S.

1978-01-01

Experiments were conducted in which a stream of premixed propane and air was burned under conditions representative of gas turbine operation. Emissions of NOx, CO, and unburned hydrocarbons (UHC) were measured over a range of combustor inlet temperature, pressure, and residence time at equivalence ratios from 0.7 down to the lean stability limit. At an inlet temperature of 600 K, observed NOx levels dropped markedly with decreasing pressure for pressures below 20 atm. The NOx levels are proportional to combustor residence time and formation rates were principally a function of adiabatic flame temperature. For adiabatic flame temperatures of 2050 K and higher, CO reached chemical equilibrium within 2 msec. Unburned hydrocarbon species dropped to a negligible level within 2 msec regardless of inlet temperature, pressure, or equivalence ratio. For a combustor residence time of 2.5 msec, combustion inefficiency became less than 0.01% at an adiabatic flame temperature of 2050 K. The maximum combustion inefficiency observed was on the order of 1% and corresponded to conditions near the lean stability limit. Using a perforated plate flameholder, this limit is well represented by the condition of 1800 K adiabatic flame temperature.

Wide range operation of advanced low NOx combustors for supersonic high-altitude aircraft gas turbines

NASA Technical Reports Server (NTRS)

Roberts, P. B.; Fiorito, R. J.

1977-01-01

An initial rig program tested the Jet Induced Circulation (JIC) and Vortex Air Blast (VAB) systems in small can combustor configurations for NOx emissions at a simulated high altitude, supersonic cruise condition. The VAB combustor demonstrated the capability of meeting the NOx goal of 1.0 g NO2/kg fuel at the cruise condition. In addition, the program served to demonstrate the limited low-emissions range available from the lean, premixed combustor. A follow-on effort was concerned with the problem of operating these lean, premixed combustors with acceptable emissions at simulated engine idle conditions. Various techniques have been demonstrated that allow satisfactory operation on both the JIC and VAB combustors at idle with CO emissions below 20 g/kg fuel. The VAB combustor was limited by flashback/autoignition phenomena at the cruise conditions to a pressure of 8 atmospheres. The JIC combustor was operated up to the full design cruise pressure of 14 atmospheres without encountering an autoignition limitation although the NOx levels, in the 2-3 g NO2/kg fuel range, exceeded the program goal.

Experimental Investigation of a Multiplex Fuel Injector Module With Discrete Jet Swirlers for Low Emission Combustors

NASA Technical Reports Server (NTRS)

Tacina, Robert; Mao, Chien-Pei; Wey, Changlie

2004-01-01

A low-NOx emissions combustor concept has been demonstrated in flame-tube tests. A lean-direct injection (LDI) concept was used where the fuel is injected directly into the flame zone and the overall equivalence ratio of the mixture is lean. The LDI concept described in this report is a multiplex fuel injector module containing multipoint fuel injection tips and multi-burning zones. The injector module comprises 25 equally spaced injection tips within a 76 by 76 mm area that fits into the flame-tube duct. The air swirlers were made from a concave plate on the axis of the fuel injector using drilled holes at an angle to the axis of the fuel injector. The NOx levels were quite low and are greater than 70 percent lower than the 1996 ICAO standard. At an inlet temperature of 810 K, inlet pressure of 2760 kPa, pressure drop of 4 percent and a flame temperature of 1900 K with JP8 fuel, the NOx emission index was 9. The 25-point injector module exhibited the most uniform radial distribution of fuel-air mixture and NOx emissions in the flame tube when compared to other multipoint injection devices. A correlation is developed relating the NOx emissions to inlet temperature, inlet pressure, equivalence ratio and pressure drop.

Uniformity index measurement technology using thermocouples to improve performance in urea-selective catalytic reduction systems

NASA Astrophysics Data System (ADS)

Park, Sangki; Oh, Jungmo

2018-05-01

The current commonly used nitrogen oxides (NOx) emission reduction techniques employ hydrocarbons (HCs), urea solutions, and exhaust gas emissions as the reductants. Two of the primary denitrification NOx (DeNOx) catalyst systems are the HC-lean NOx trap (HC-LNT) catalyst and urea-selective catalytic reduction (urea-SCR) catalyst. The secondary injection method depends on the type of injector, injection pressure, atomization, and spraying technique. In addition, the catalyst reaction efficiency is directly affected by the distribution of injectors; hence, the uniformity index (UI) of the reductant is very important and is the basis for system optimization. The UI of the reductant is an indicator of the NOx conversion efficiency (NCE), and good UI values can reduce the need for a catalyst. Therefore, improving the UI can reduce the cost of producing a catalytic converter, which are expensive due to the high prices of the precious metals contained therein. Accordingly, measurement of the UI is an important process in the development of catalytic systems. Two of the commonly used methods for measuring the reductant UI are (i) measuring the exhaust emissions at many points located upstream/downstream of the catalytic converter and (ii) acquisition of a reductant distribution image on a section of the exhaust pipe upstream of the catalytic converter. The purpose of this study is to develop a system and measurement algorithms to measure the exothermic response distribution in the exhaust gas as the reductant passes through the catalytic converter of the SCR catalyst system using a set of thermocouples downstream of the SCR catalyst. The system is used to measure the reductant UI, which is applied in real-time to the actual SCR system, and the results are compared for various types of mixtures for various engine operating conditions and mixer types in terms of NCE.

Experimental study of the effects of flameholder geometry on emissions and performance of lean premixed combustors

NASA Technical Reports Server (NTRS)

Roffe, G.; Venkataramani, K. S.

1978-01-01

Emissions of NOx, CO, and unburned hydrocarbons (UHC) are reported for a lean premixed propane-air system at inlet conditions of 800K and 1MPa using twelve flameholder designs. The flameholders tested represent six design concepts with two values of blockage for each concept. Data were obtained at reference velocities of 35 m/s, 25 m/s and 20 m/s at combustor stations 10 cm and 30 cm downstream of the flameholders. Flameholder pressure drop was found to be a principal determinant of emissions performance. Designs producing larger pressure drops also produced less NOx, CO, and UHC emissions. The lean stability limit equivalence ratio was found to be approximately 0.35 for all designs. Flashback velocities (axial components in the flameholder passages) varied between 30 m/s and 40 m/s. A perforated plate flameholder was operated with a velocity as low as 23 m/s through the perforations at equivalence ratio 0.7 without producing flashback.

Combustor materials requirements and status of ceramic matrix composites

NASA Technical Reports Server (NTRS)

Hecht, Ralph J.; Johnson, Andrew M.

1992-01-01

The HSCT combustor will be required to operate with either extremely rich or lean fuel/air ratios to reduce NO(x) emission. NASA High Speed Research (HSR) sponsored programs at Pratt & Whitney (P&W) and GE Aircraft Engines (GEAE) have been studying rich and lean burn combustor design approaches which are capable of achieving the aggressive HSCT NO(x) emission goals. In both of the combustor design approaches under study, high temperature (2400-3000 F) materials are necessary to meet the HSCT emission goals of 3-8 gm/kg. Currently available materials will not meet the projected requirements for the HSCT combustor. The development of new materials is an enabling technology for the successful introduction to service of the HSCT.

Gaseous Emissions Results from a Three-Cup Flametube Test of a Third-Generation Swirl-Venturi Lean Direct Injection Combustion Concept

NASA Technical Reports Server (NTRS)

Tacina, Kathleen M.; Podboy, Derek P.; Lee, Phil; Dam, Bidhan

2017-01-01

This paper summarizes the development of lean direct injection (LDI) combustor technology at, or in collaboration with, the NASA Glenn Research Center. These configurations differ mainly in fuel-air mixing strategy. The paper reviews the NOx performance and operability characteristics of multiple LDI configurations tested at NASA Glenn.

Analysis of effect of flameholder characteristics on lean, premixed, partially vaporized fuel-air mixtures quality and nitrogen oxides emissions

NASA Technical Reports Server (NTRS)

Cooper, L. P.

1981-01-01

An analysis was conducted of the effect of flameholding devices on the precombustion fuel-air characteristics and on oxides of nitrogen (NOx) emissions for combustion of premixed partially vaporized mixtures. The analysis includes the interrelationships of flameholder droplet collection efficiency, reatomization efficiency and blockage, and the initial droplet size distribution and accounts for the contribution of droplet combustion in partially vaporized mixtures to NOx emissions. Application of the analytical procedures is illustrated and parametric predictions of NOx emissions are presented.

Fuel/air nonuniformity - Effect on nitric oxide emissions

NASA Technical Reports Server (NTRS)

Lyons, V. J.

1981-01-01

An analytical and experimental study was performed to determine the effect of inlet fuel/air profile nonuniformity on NO(x) emissions. The theoretical NO(x) levels were verified in a flame-tube rig at inlet air temperatures of 600, 700, and 800 K, 0.3 MPa rig pressure, 25 m/sec reference velocity, overall equivalence ratio of 0.6 and residence time near 0.002 sec. The theory predicts an increase in NO(x) emissions for increased fuel/air nonuniformity for average equivalence ratios less than 0.7, while for average equivalence ratios near stoichiometric, increasing the nonuniformity will decrease NO(x) emissions. The results can be used to predict the degree of uniformity of fuel/air profiles necessary to achieve NO(x) emissions goals for actual engines that use lean premixed, prevaporized combustion systems.

Experimental and Modeling Investigation of the Effect of Air Preheat on the Formation of NOx in an RQL Combustor

NASA Technical Reports Server (NTRS)

Samuelsen, G. S.; Brouwer, J.; Vardakas, M. A.; Holderman, J. D.

2012-01-01

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine systems. The success of this low-NOx combustor strategy is dependent upon the links between the formation of NOx, inlet air preheat temperature, and the mixing of the jet air and fuel-rich streams. Chemical equilibrium and kinetics modeling calculations and experiments were performed to further understand NOx emissions in an RQL combustor. The results indicate that as the temperature at the inlet to the mixing zone increases (due to preheating and/or operating conditions) the fuel-rich zone equivalence ratio must be increased to achieve minimum NOx formation in the primary zone of the combustor. The chemical kinetics model illustrates that there is sufficient residence time to produce NOx at concentrations that agree well with the NOx measurements. Air preheat was found to have very little effect on mixing, but preheating the air did increase NOx emissions significantly. By understanding the mechanisms governing NOx formation and the temperature dependence of key reactions in the RQL combustor, a strategy can be devised to further reduce NOx emissions using the RQL concept.

Combustion characteristics of hydrogen. Carbon monoxide based gaseous fuels

NASA Technical Reports Server (NTRS)

Notardonato, J. J.; White, D. J.; Kubasco, A. J.; Lecren, R. T.

1981-01-01

An experimental rig program was conducted with the objective of evaluating the combuston performance of a family of fuel gases based on a mixture of hydrogen and carbon monoxide. These gases, in addition to being members of a family, were also representative of those secondary fuels that could be produced from coal by various gasification schemes. In particular, simulated Winkler, Lurgi, and Blue-water low and medium energy content gases were used as fuels in the experimental combustor rig. The combustor used was originally designed as a low NOx rich-lean system for burning liquid fuels with high bound nitrogen levels. When used with the above gaseous fuels this combustor was operated in a lean-lean mode with ultra long residence times. The Blue-water gas was also operated in a rich-lean mode. The results of these tests indicate the possibility of the existence of an 'optimum' gas turbine hydrogen - carbon monoxide based secondary fuel. Such a fuel would exhibit NOx and high efficiency over the entire engine operating range. It would also have sufficient stability range to allow normal light-off and engine acceleration. Solar Turbines Incorporated would like to emphasize that the results presented here have been obtained with experimental rig combustors. The technologies generated could, however, be utilized in future commercial gas turbines.

A New Paradigm in Modeling and Simulations of Complex Oxidation Chemistry Using a Statistical Approach

DTIC Science & Technology

2009-03-31

8. This range encompasses diesel , HCCI and gas turbine engines , including cold ignition; and NOx , CO and soot pollutant formation in the lean and...equivalence ratios from 0.125 to 8. This range encompasses diesel , HCCI and gas turbine engines , including cold ignition; and NOx , CO and soot pollutant...California Institute of Technology Mechanical Engineering Department Pasadena CA 91125 i Abstract This report describes a study

Lean, Premixed-Prevaporized (LPP) combustor conceptual design study

NASA Technical Reports Server (NTRS)

Dickman, R. A.; Dodds, W. J.; Ekstedt, E. E.

1979-01-01

Four combustion systems were designed and sized for the energy efficient engine. A fifth combustor was designed for the cycle and envelope of the twin-spool, high bypass ratio, high pressure ratio turbofan engine. Emission levels, combustion performance, life, and reliability assessments were made for these five combustion systems. Results of these design studies indicate that cruise NOx emission can be reduced by the use of lean, premixed-prevaporaized combustion and airflow modulation.

Emissions of nitrogen oxides from an experimental hydrogen-fueled gas turbine combustor

NASA Technical Reports Server (NTRS)

Norgren, C. T.; Ingebo, R. D.

1974-01-01

The effect of operating variables of a hydrogen fueled combustor on exhaust concentrations of total oxides of nitrogen was determined at inlet-air temperature levels up to 810 K, pressure of 414,000N/sa m, and reference velocity of 21.3 m/sec. The combustor, which was originally designed for hydrocarbon fuel produced a NO(x) concentration of 380 ppm with hydrogen at 810 K inlet-air temperature. A reduction in NO(x) of about 30 % was obtained by modification to a lean or rich primary zone. The lowest NO(x) levels obtained with hydrogen were equivalent to those of the reference combustor burning hydrocarbon fuels.

Drive cycle simulation of high efficiency combustions on fuel economy and exhaust properties in light-duty vehicles

DOE PAGES

Gao, Zhiming; Curran, Scott J.; Parks, James E.; ...

2015-04-06

We present fuel economy and engine-out emissions for light-duty (LD) conventional and hybrid vehicles powered by conventional and high-efficiency combustion engines. Engine technologies include port fuel-injected (PFI), direct gasoline injection (GDI), reactivity controlled compression ignition (RCCI) and conventional diesel combustion (CDC). In the case of RCCI, the engine utilized CDC combustion at speed/load points not feasible with RCCI. The results, without emissions considered, show that the best fuel economies can be achieved with CDC/RCCI, with CDC/RCCI, CDC-only, and lean GDI all surpassing PFI fuel economy significantly. In all cases, hybridization significantly improved fuel economy. The engine-out hydrocarbon (HC), carbon monoxidemore » (CO), nitrogen oxides (NOx), and particulate matter (PM) emissions varied remarkably with combustion mode. The simulated engine-out CO and HC emissions from RCCI are significantly higher than CDC, but RCCI makes less NOx and PM emissions. Hybridization can improve lean GDI and RCCI cases by increasing time percentage for these more fuel efficient modes. Moreover, hybridization can dramatically decreases the lean GDI and RCCI engine out emissions. Importantly, lean GDI and RCCI combustion modes decrease exhaust temperatures, especially for RCCI, which limits aftertreatment performance to control tailpipe emissions. Overall, the combination of engine and hybrid drivetrain selected greatly affects the emissions challenges required to meet emission regulations.« less

Pollutant formation in fuel lean recirculating flows. Ph.D. Thesis. Final Report; [in an Opposed Reacting Jet Combustor

NASA Technical Reports Server (NTRS)

Schefer, R. W.; Sawyer, R. F.

1976-01-01

An opposed reacting jet combustor (ORJ) was tested at a pressure of 1 atmosphere. A premixed propane/air stream was stabilized by a counterflowing jet of the same reactants. The resulting intensely mixed zone of partially reacted combustion products produced stable combustion at equivalence ratios as low as 0.45. Measurements are presented for main stream velocities of 7.74 and 13.6 m/sec with an opposed jet velocity of 96 m/sec, inlet air temperatures from 300 to 600 K, and equivalence ratios from 0.45 to 0.625. Fuel lean premixed combustion was an effective method of achieving low NOx emissions and high combustion efficiencies simultaneously. Under conditions promoting lower flame temperature, NO2 constituted up to 100 percent of the total NOx. At higher temperatures this percentage decreased to a minimum of 50 percent.

Method of preparing doped oxide catalysts for lean NOx exhaust

DOEpatents

Park, Paul W.

2004-03-09

The lean NOx catalyst includes a substrate, an oxide support material, preferably .gamma.-alumina deposited on the substrate and a metal or metal oxide promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium cerium, and vanadium, and oxides thereof, and any combinations thereof. The .gamma.-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between 80 and 350 m.sup.2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to about 0.2 weight percent. In a preferred embodiment the .gamma.-alumina is prepared by a sol-gel method, with the metal doping of the .gamma.-alumina preferably accomplished using an incipient wetness impregnation technique.

Low NO sub x heavy fuel combustor concept program. Phase 1A: Combustion technology generation coal gas fuels

NASA Technical Reports Server (NTRS)

Sherlock, T. P.

1982-01-01

Combustion tests of two scaled burners using actual coal gas from a 25 ton/day fluidized bed coal gasifier are described. The two combustor configurations studied were a ceramic lined, staged rich/lean burner and an integral, all metal multiannual swirl burner (MASB). The tests were conducted over a range of temperature and pressures representative of current industrial combustion turbine inlet conditions. Tests on the rich lean burner were conducted at three levels of product gas heating values: 104, 197 and 254 btu/scf. Corresponding levels of NOx emissions were 5, 20 and 70 ppmv. Nitrogen was added to the fuel in the form of ammonia, and conversion efficiencies of fuel nitrogen to NOx were on the order of 4 percent to 12 percent, which is somewhat lower than the 14 percent to 18 percent conversion efficiency when src-2 liquid fuel was used. The MASB was tested only on medium btu gas (220 to 270 btu/scf), and produced approximately 80 ppmv NOx at rated engine conditions. Both burners operated similarly on actual coal gas and erbs fuel, and all heating values tested can be successfully burned in current machines.

Turbulent transport measurements in a model of GT-combustor

NASA Astrophysics Data System (ADS)

Chikishev, L. M.; Gobyzov, O. A.; Sharaborin, D. K.; Lobasov, A. S.; Dulin, V. M.; Markovich, D. M.; Tsatiashvili, V. V.

2016-10-01

To reduce NOx formation modern industrial power gas-turbines utilizes lean premixed combustion of natural gas. The uniform distribution of local fuel/air ratio in the combustion chamber plays one of the key roles in the field of lean combustion to prevent thermo-acoustic pulsations. Present paper reports on simultaneous Particle Image Velocimetry and acetone Planar Laser Induced Fluorescence measurements in a cold model of GT-combustor to investigate mixing processes which are relevant to the organization of lean premixed combustion. Velocity and passive admixture pulsations correlations were measured to verify gradient closer model, which is often used in Reynolds-Averaged Navier-Stokes (RANS) simulation of turbulent mixing.

NOVEL CATALYSTS FOR LEAN-NOX REDUCTION BY METHANE. (R825430)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

Low NO sub x heavy fuel combustor concept program

NASA Technical Reports Server (NTRS)

Russell, P.; Beal, G.; Hinton, B.

1981-01-01

A gas turbine technology program to improve and optimize the staged rich lean low NOx combustor concept is described. Subscale combustor tests to develop the design information for optimization of the fuel preparation, rich burn, quick air quench, and lean burn steps of the combustion process were run. The program provides information for the design of high pressure full scale gas turbine combustors capable of providing environmentally clean combustion of minimally of minimally processed and synthetic fuels. It is concluded that liquid fuel atomization and mixing, rich zone stoichiometry, rich zone liner cooling, rich zone residence time, and quench zone stoichiometry are important considerations in the design and scale up of the rich lean combustor.

The effect of incomplete fuel-air mixing on the lean limit and emissions characteristics of a Lean Prevaporized Premixed (LPP) combustor

NASA Technical Reports Server (NTRS)

Santavicca, D. A.; Steinberger, R. L.; Gibbons, K. A.; Citeno, J. V.; Mills, S.

1993-01-01

Results are presented from an experimental study of the effect of incomplete fuel-air mixing on the lean limit and emissions characteristics of a lean, prevaporized, premixed (LPP), coaxial mixing tube combustor. Two-dimensional exciplex fluorescence was used to characterize the degree of fuel vaporization and mixing at the combustor inlet under non-combusting conditions. These tests were conducted at a pressure of 4 atm., a temperature of 400 C, a mixer tube velocity of 100 m/sec and an equivalence ratio of .8, using a mixture of tetradecane, 1 methyl naphthalene and TMPD as a fuel simulant. Fuel-air mixtures with two distinct spatial distributions were studied. The exciplex measurements showed that there was a significant amount of unvaporized fuel at the combustor entrance in both cases. One case, however, exhibited a very non-uniform distribution of fuel liquid and vapor at the combustor entrance, i.e., with most of the fuel in the upper half of the combustor tube, while in the other case, both the fuel liquid and vapor were much more uniformly distributed across the width of the combustor entrance. The lean limit and emissions measurements were all made at a pressure of 4 atm. and a mixer tube velocity of 100 m/sec, using Jet A fuel and both fuel-air mixture distributions. Contrary to what was expected, the better mixed case was found to have a substantially leaner operating limit. The two mixture distributions also unexpectedly resulted in comparable NO(x) emissions, for a given equivalence ratio and inlet temperature, however, lower NO(x) emissions were possible in the better mixed case due to its leaner operating limit.

[Selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalysts].

PubMed

Sun, Hong; Quan, Xie; Zhang, Yao-bin; Zhao, Ya-zhi

2008-06-01

Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst was prepared by sol-gel and impregnation. Furthermore, selective catalytic reduction of NOx over Pd/CeZr/TiO2/Al2O3 wire-mesh honeycomb catalyst with propylene under lean burn condition was studied. The effects of the concentration of tetra-n-butyl titanate and dipcoat cycles on TiO2 washcoat were studied by SEM, and the effects of Pd concentration, O2 concentration and gas velocity on catalytic activity were investigated. The experimental results showed that the TiO2 washcoat on wire-mesh support is even and crack-free when the support is impregnated in 20.0% tetra- n-butyl titanate sol for 2 cycles. The NOx conversion decreases with Pd concentration increase. When Pd concentration is 0.23%, NOx conversion is highest. NOx conversion increases with oxygen concentration increase in the range of 1.5%-6.0%. However, when oxygen concentration is higher than 6.0%, NOx conversion decreases with increasing oxygen concentration. The NOx conversion decreases with gas velocity increase and its effect is severer at high temperature than low temperature.

Flashback Arrestor for LPP, Low NOx Combustors

NASA Technical Reports Server (NTRS)

Kraemer, Gil; Lee, Chi-Ming

1998-01-01

Lean premixed, prevaporized (LPP) high temperature combustor designs as explored for the Advanced Subsonic Transport (AST) and High Speed Civil Transport (HSCT) combustors can achieve low NO(x), emission levels. An enabling device is needed to arrest flashback and inhibit preignition at high power conditions and during transients (surge and rapid spool down). A novel flashback arrestor design has demonstrated the ability to arrest flashback and inhibit preignition in a 4.6 cm diameter tubular reactor at full power inlet temperatures (725 C) using Jet-A fuel at 0.4 less than or equal To phi less than or equal to 3.5. Several low pressure loss (0.2 to 0.4% at 30 m/s) flashback arrestor designs were developed which arrested flashback at all of the test conditions. Flame holding was also inhibited off the flash arrestor face or within the downstream tube even velocities (less than or equal to 3 to 6 m/s), thus protecting the flashback arrestor and combustor components. Upstream flow conditions influence the specific configuration based on using either a 45% or 76% upstream geometric blockage. Stationary, lean premixed dry low NO(x) gas turbine combustors would also benefit from this low pressure drop flashback arrestor design which can be easily integrated into new and existing designs.

Low Emission Hydrogen Combustors for Gas Turbines Using Lean Direct Injection

NASA Technical Reports Server (NTRS)

Marek, C. John; Smith, Timothy D.; Kundu, Krishna

2005-01-01

One of the key technology challenges for the use of hydrogen in gas turbine engines is the performance of the combustion system, in particular the fuel injectors. To investigate the combustion performance of gaseous hydrogen fuel injectors flame tube combustor experiments were performed. Tests were conducted to measure the nitrogen oxide (NOx) emissions and combustion performance at inlet conditions of 600 to 1000 deg F, 60 to 200 pounds per square inch absolute (psia), and equivalence ratios up to 0.48. All the injectors were based on Lean Direct Injection (LDI) technology with multiple injection points and quick mixing. One challenge to hydrogen based premixing combustion systems is flashback since hydrogen has a reaction rate over seven times that of Jet-A. To reduce the risk, design mixing times were kept short and velocities high to minimize flashback. Five fuel injector designs were tested in 2.5 and 3.5-in. diameter flame tubes with non-vitiated heated air and gaseous hydrogen. Data is presented on measurements of NOx emissions and combustion efficiency for the hydrogen injectors at 1.0, 3.125, and 5.375 in. from the injector face. Results show that for some configurations, NOx emissions are comparable to that of state of the art Jet-A LDI combustor concepts.

Low-Emission Hydrogen Combustors for Gas Turbines Using Lean Direct Injection

NASA Technical Reports Server (NTRS)

Marek, C. John; Smith, Timothy D.; Kundu, Krishna

2007-01-01

One of the key technology challenges for the use of hydrogen in gas turbine engines is the performance of the combustion system, in particular the fuel injectors. To investigate the combustion performance of gaseous hydrogen fuel injectors flame tube combustor experiments were performed. Tests were conducted to measure the nitrogen oxide (NO(x)) emissions and combustion performance at inlet conditions of 588 to 811 K, 0.4 to 1.4 MPa, and equivalence ratios up to 0.48. All the injectors were based on Lean Direct Injection (LDI) technology with multiple injection points and quick mixing. One challenge to hydrogen-based premixing combustion systems is flashback since hydrogen has a reaction rate over 7 times that of Jet-A. To reduce the risk, design mixing times were kept short and velocities high to minimize flashback. Five fuel injector designs were tested in 6.35- and 8.9-cm-diameter flame tubes with non-vitiated heated air and gaseous hydrogen. Data is presented on measurements of NO(x) emissions and combustion efficiency for the hydrogen injectors at 2.540, 7.937, and 13.652 cm from the injector face. Results show that for some configurations, NO(x) emissions are comparable to that of state of the art Jet-A LDI combustor concepts.

Investigation of Mixed Oxide Catalysts for NO Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szanyi, Janos; Karim, Ayman M.; Pederson, Larry R.

2014-12-09

The oxidation of engine-generated NO to NO2 is an important step in the reduction of NOx in lean engine exhaust because NO2 is required for the performance of the LNT technology [2], and it enhances the activities of ammonia selective catalytic reduction (SCR) catalysts [1]. In particular, for SCR catalysts an NO:NO2 ratio of 1:1 is most effective for NOx reduction, whereas for LNT catalysts, NO must be oxidized to NO2 before adsorption on the storage components. However, NO2 typically constitutes less than 10% of NOx in lean exhaust, so catalytic oxidation of NO is essential. Platinum has been foundmore » to be especially active for NO oxidation, and is widely used in DOC and LNT catalysts. However, because of the high cost and poor thermal durability of Pt-based catalysts, there is substantial interest in the development of alternatives. The objective of this project, in collaboration with partner General Motors, is to develop mixed metal oxide catalysts for NO oxidation, enabling lower precious metal usage in emission control systems. [1] M. Koebel, G. Madia, and M. Elsener, Catalysis Today 73, 239 (2002). [2] C. H. Kim, G. S. Qi, K. Dahlberg, and W. Li, Science 327, 1624 (2010).« less

Advanced Natural Gas Reciprocating Engine(s)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pike, Edward

The objective of the Cummins ARES program, in partnership with the US Department of Energy (DOE), is to develop advanced natural gas engine technologies that increase engine system efficiency at lower emissions levels while attaining lower cost of ownership. The goals of the project are to demonstrate engine system achieving 50% Brake Thermal Efficiency (BTE) in three phases, 44%, 47% and 50% (starting baseline efficiency at 36% BTE) and 0.1 g/bhp-hr NOx system out emissions (starting baseline NOx emissions at 2 – 4 g/bhp-hr NOx). Primary path towards above goals include high Brake Mean Effective Pressure (BMEP), improved closed cyclemore » efficiency, increased air handling efficiency and optimized engine subsystems. Cummins has successfully demonstrated each of the phases of this program. All targets have been achieved through application of a combined set of advanced base engine technologies and Waste Heat Recovery from Charge Air and Exhaust streams, optimized and validated on the demonstration engine and other large engines. The following architectures were selected for each Phase: Phase 1: Lean Burn Spark Ignited (SI) Key Technologies: High Efficiency Turbocharging, Higher Efficiency Combustion System. In production on the 60/91L engines. Over 500MW of ARES Phase 1 technology has been sold. Phase 2: Lean Burn Technology with Exhaust Waste Heat Recovery (WHR) System Key Technologies: Advanced Ignition System, Combustion Improvement, Integrated Waste Heat Recovery System. Base engine technologies intended for production within 2 to 3 years Phase 3: Lean Burn Technology with Exhaust and Charge Air Waste Heat Recovery System Key Technologies: Lower Friction, New Cylinder Head Designs, Improved Integrated Waste Heat Recovery System. Intended for production within 5 to 6 years Cummins is committed to the launch of next generation of large advanced NG engines based on ARES technology to be commercialized worldwide.« less

Wide range operation of advanced low NOx aircraft gas turbine combustors

NASA Technical Reports Server (NTRS)

Roberts, P. B.; Fiorito, R. J.; Butze, H. F.

1978-01-01

The paper summarizes the results of an experimental test rig program designed to define and demonstrates techniques which would allow the jet-induced circulation and vortex air blast combustors to operate stably with acceptable emissions at simulated engine idle without compromise to the low NOx emissions under the high-altitude supersonic cruise condition. The discussion focuses on the test results of the key combustor modifications for both the simulated engine idle and cruise conditions. Several range-augmentation techniques are demonstrated that allow the lean-reaction premixed aircraft gas turbine combustor to operate with low NOx emissons at engine cruise and acceptable CO and UHC levels at engine idle. These techniques involve several combinations, including variable geometry and fuel switching designs.

Selective NOx Recirculation for Stationary Lean-Burn Natural Gas Engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nigel Clark; Gregory Thompson; Richard Atkinson

Selective NOx Recirculation (SNR) involves cooling the engine exhaust gas and then adsorbing the oxides of nitrogen (NOx) from the exhaust stream, followed by the periodic desorption of NOx. By returning the desorbed, concentrated NOx into the engine intake and through the combustion chamber, a percentage of the NOx is decomposed during the combustion process. An initial study of NOx decomposition during lean-burn combustion was concluded in 2004 using a 1993 Cummins L10G 240hp natural gas engine. It was observed that the air/fuel ratio, injected NO (nitric oxide) quantity and engine operating points affected NOx decomposition rates of the engine.more » Chemical kinetic modeling results were also used to determine optimum NOx decomposition operating points and were published in the 2004 annual report. A NOx decomposition rate of 27% was measured from this engine under lean-burn conditions while the software model predicted between 35-42% NOx decomposition for similar conditions. A later technology 1998 Cummins L10G 280hp natural gas engine was procured with the assistance of Cummins Inc. to replace the previous engine used for 2005 experimental research. The new engine was equipped with an electronic fuel management system with closed-loop control that provided a more stable air/fuel ratio control and improved the repeatability of the tests. The engine was instrumented with an in-cylinder pressure measurement system and electronic controls, and was adapted to operate over a range of air/fuel ratios. The engine was connected to a newly commissioned 300hp alternating current (AC) motoring dynamometer. The second experimental campaign was performed to acquire both stoichiometric and slightly rich (0.97 lambda ratio) burn NOx decomposition rates. Effects of engine load and speed on decomposition were quantified, but Exhaust Gas Recirculation (EGR) was not varied independently. Decomposition rates of up to 92% were demonstrated. Following recommendations at the 2004 ARES peer review meeting at Argonne National Laboratories, in-cylinder pressure was measured to calculate engine indicated mean effective pressure (IMEP) changes due to NOx injections and EGR variations, and to observe conditions in the cylinder. The third experimental campaign gathered NOx decomposition data at 800, 1200 and 1800 rpm. EGR was added via an external loop, with EGR ranging from zero to the point of misfire. The air/fuel ratio was set at both stoichiometric and slightly rich conditions, and NOx decomposition rates were calculated for each set of runs. Modifications were made to the engine exhaust manifold to record individual exhaust temperatures. The three experimental campaigns have provided the data needed for a comprehensive model of NOx decomposition during the combustion process, and data have confirmed that there was no significant impact of injected NO on in-cylinder pressure. The NOx adsorption system provided by Sorbent Technologies Corp. (Twinsburg, OH), comprised a NOx adsorber, heat exchanger and a demister. These components were connected to the engine, and data were gathered to show both the adsorption of NOx from the engine, and desorption of NOx from the carbon-based sorbent material back into the engine intake, using a heated air stream. In order to quantify the NOx adsorption/desorption characteristics of the sorbent material, a bench top adsorption system was constructed and instrumented with thermocouples and the system output was fed into a NOx analyzer. The temperature of this apparatus was controlled while gathering data on the characteristics of the sorbent material. These data were required for development of a system model. Preliminary data were gathered in 2005, and will continue in early 2006. To assess the economic benefits of the proposed SNR technology the WVU research team has been joined in the last quarter by Dr Richard Turton (WVU-Chemical Engineering), who is modeling, sizing and costing the major components. The tasks will address modeling and preliminary design of the heat exchanger, demister and NOx sorbent chamber suitable for a given engine. A simplified linear driving force model was developed to predict NOx adsorption into the sorbent material as cooled exhaust passes over fresh sorbent material. This aspect of the research will continue into 2006, and the benefits and challenges of SNR will be compared with those of competing systems, such as Selective Catalytic Reduction. Chemical kinetic modeling using the CHEMKIN software package was extended in 2005 to the case of slightly rich burn with EGR. Simulations were performed at 10%, 20%, 30% and 40% of the intake air replaced with EGR. NOx decomposition efficiency was calculated at the point in time where 98% of fuel was consumed, which is believed to be a conservative approach. The modeling data show that reductions of over 70% are possible using the ''98% fuel burned'' assumption.« less

Fundamental Study of a Single Point Lean Direct Injector. Part I: Effect of Air Swirler Angle and Injector Tip Location on Spray Characteristics

NASA Technical Reports Server (NTRS)

Tedder, Sarah A.; Hicks, Yolanda R.; Tacina, Kathleen M.; Anderson, Robert C.

2014-01-01

Lean direct injection (LDI) is a combustion concept to reduce oxides of nitrogen (NOx) for next generation aircraft gas turbine engines. These newer engines have cycles that increase fuel efficiency through increased operating pressures, which increase combustor inlet temperatures. NOx formation rates increase with higher temperatures; the LDI strategy avoids high temperature by staying fuel lean and away from stoichiometric burning. Thus, LDI relies on rapid and uniform fuel/air mixing. To understand this mixing process, a series of fundamental experiments are underway in the Combustion and Dynamics Facility at NASA Glenn Research Center. This first set of experiments examines cold flow (non-combusting) mixing using air and water. Using laser diagnostics, the effects of air swirler angle and injector tip location on the spray distribution, recirculation zone, and droplet size distribution are examined. Of the three swirler angles examined, 60 deg is determined to have the most even spray distribution. The injector tip location primarily shifts the flow without changing the structure, unless the flow includes a recirculation zone. When a recirculation zone is present, minimum axial velocity decreases as the injector tip moves downstream towards the venturi exit; also the droplets become more uniform in size and angular distribution.

A Comparison of Three Second-generation Swirl-Venturi Lean Direct Injection Combustor Concepts

NASA Technical Reports Server (NTRS)

Tacina, Kathleen M.; Podboy, Derek P.; He, Zhuohui Joe; Lee, Phil; Dam, Bidhan; Mongia, Hukam

2016-01-01

Three variations of a low emissions aircraft gas turbine engine combustion concept were developed and tested. The concept is a second generation swirl-venturi lean direct injection (SV-LDI) concept. LDI is a lean-burn combustion concept in which the fuel is injected directly into the flame zone. All three variations were based on the baseline 9- point SV-LDI configuration reported previously. The three second generation SV-LDI variations are called the 5-recess configuration, the flat dome configuration, and the 9- recess configuration. These three configurations were tested in a NASA Glenn Research Center medium pressure flametube. All three second generation variations had better low power operability than the baseline 9-point configuration. All three configurations had low NO(sub x) emissions, with the 5-recess configuration generally having slightly lower NO(x) than the flat dome or 9-recess configurations. Due to the limitations of the flametube that prevented testing at pressures above 20 atm, correlation equations were developed for the at dome and 9-recess configurations so that the landing-takeoff NO(sub x) emissions could be estimated. The flat dome and 9-recess landing-takeoff NO(x) emissions are estimated to be 81-88% below the CAEP/6 standards, exceeding the project goal of 75% reduction.

Fundamental Study of a Single Point Lean Direct Injector. Part I: Effect of Air Swirler Angle and Injector Tip Location on Spray Characteristics

NASA Technical Reports Server (NTRS)

Tedder, Sarah A.; Hicks, Yolanda R.; Tacina, Kathleen M.; Anderson, Robert C.

2015-01-01

Lean direct injection (LDI) is a combustion concept to reduce oxides of nitrogen (NOx) for next generation aircraft gas turbine engines. These newer engines have cycles that increase fuel efficiency through increased operating pressures, which increase combustor inlet temperatures. NOx formation rates increase with higher temperatures; the LDI strategy avoids high temperature by staying fuel lean and away from stoichiometric burning. Thus, LDI relies on rapid and uniform fuel/air mixing. To understand this mixing process, a series of fundamental experiments are underway in the Combustion and Dynamics Facility at NASA Glenn Research Center. This first set of experiments examines cold flow (non-combusting) mixing using air and water. Using laser diagnostics, the effects of air swirler angle and injector tip location on the spray distribution, recirculation zone, and droplet size distribution are examined. Of the three swirler angles examined, 60 degrees is determined to have the most even spray distribution. The injector tip location primarily shifts the flow without changing the structure, unless the flow includes a recirculation zone. When a recirculation zone is present, minimum axial velocity decreases as the injector tip moves downstream towards the venturi exit; also the droplets become more uniform in size and angular distribution.

NOx Emissions Performance and Correlation Equations for a Multipoint LDI Injector

NASA Technical Reports Server (NTRS)

He, Zhuohui J.; Chang, Clarence T.; Follen, Caitlin E.

2014-01-01

Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (phi) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 percent reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 percent of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.

NOx Emissions Performance and Correlation Equations for a Multipoint LDI Injector

NASA Technical Reports Server (NTRS)

He, Zhuohui Joe; Chang, Clarence T.; Follen, Caitlin E.

2015-01-01

Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions.This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio(theta) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.

NOx Emissions Performance and Correlation Equations for a Multipoint LDI Injector

NASA Technical Reports Server (NTRS)

He, Zhuohui J.; Chang, Clarence T.; Follen, Caitlin E.

2015-01-01

Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (?) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66% reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50% of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.

NOx Emissions Performance and Correlation Equations for a Multipoint LDI Injector

NASA Technical Reports Server (NTRS)

He, Zhuohui J.; Chang, Clarence T.; Follen, Caitlin E.

2014-01-01

Lean Direct Injection (LDI) is a combustor concept that reduces nitrogen oxides (NOx) emissions. This paper looks at a 3-zone multipoint LDI concept developed by Parker Hannifin Corporation. The concept was tested in a flame-tube test facility at NASA Glenn Research Center. Due to test facility limitations, such as inlet air temperature and pressure, the flame-tube test was not able to cover the full set of engine operation conditions. Three NOx correlation equations were developed based on assessing NOx emissions dependencies on inlet air pressure (P3), inlet air temperature (T3), and fuel air equivalence ratio (?) to estimate the NOx emissions at the unreachable high engine power conditions. As the results, the NOx emissions are found to be a strong function of combustion inlet air temperature and fuel air equivalence ratio but a weaker function of inlet air pressure. With these three equations, the NOx emissions performance of this injector concept is calculated as a 66 percent reduction relative to the ICAO CAEP-6 standard using a 55:1 pressure-ratio engine cycle. Uncertainty in the NOx emissions estimation increases as the extrapolation range departs from the experimental conditions. Since maximum inlet air pressure tested was less than 50 percent of the full power engine inlet air pressure, a future experiment at higher inlet air pressure conditions is needed to confirm the NOx emissions dependency on inlet air pressure.

Activated neuro-oxidative and neuro-nitrosative pathways at the end of term are associated with inflammation and physio-somatic and depression symptoms, while predicting outcome characteristics in mother and baby.

PubMed

Roomruangwong, Chutima; Barbosa, Decio Sabbatini; Matsumoto, Andressa Keiko; Nogueira, André de Souza; Kanchanatawan, Buranee; Sirivichayakul, Sunee; Carvalho, André F; Duleu, Sebastien; Geffard, Michel; Moreira, Estefania Gastaldello; Maes, Michael

2017-12-01

To examine oxidative & nitrosative stress (O&NS) biomarkers at the end of term in relation to perinatal affective symptoms, neuro-immune biomarkers and pregnancy-related outcome variables. We measured plasma advanced oxidation protein products (AOPP), nitric oxide metabolites (NOx), total radical trapping antioxidant parameter (TRAP), -sulfhydryl (-SH), peroxides (LOOH) and paraoxonase (PON)1 activity in pregnant women with and without prenatal depression and non-pregnant controls. Pregnancy is accompanied by significantly increased AOPP and NOx, and lowered TRAP, -SH and LOOH. Increased O&NS and lowered LOOH and -SH levels are associated with prenatal depressive and physio-somatic symptoms (fatigue, pain, dyspepsia, gastro-intestinal symptoms). Increased AOPP and NOx are significantly associated with lowered -SH, TRAP and zinc, and with increased haptoglobin and C-reactive protein levels. Increased O&NS and lowered TRAP and PON 1 activity, at the end of term predict mother (e.g. hyperpigmentation, labor duration, caesarian section, cord length, breast milk flow) and baby (e.g. sleep and feeding problems) outcome characteristics. Pregnancy is accompanied by interrelated signs of O&NS, lowered antioxidant defenses and activated neuro-immune pathways. Increased O&NS at the end of term is associated with perinatal depressive and physio-somatic symptoms and may predict obstetric and behavioral complications in mother and baby. Copyright © 2017 Elsevier B.V. All rights reserved.

Control of diesel soot and NOx emissions with a particulate trap and EGR.

PubMed

Liu, Rui-xiang; Gao, Xi-yan; Yang, De-sheng; Xu, Xiao-guang

2005-01-01

The exhaust gas recirculation (EGR), coupled with a high-collection efficiency particulate trap to simultaneously control smoke and NOx emissions from diesel engines were studied. This ceramic trap developed previously provided the soot cleaning efficiency of 99%, the regeneration efficiency reaches 80% and the ratio of success reaches 97%, which make EGR used in diesel possible. At the presence of EGR, opening of the regeneration control valve of the trap was over again optimized to compensate for the decrease of the oxygen concentration in the exhaust gas resulted from EGR. The results indicated the cleaning efficiency and regeneration performance of the trap were maintained at the same level except that the back pressure increased faster. A new EGR system was developed, which is based on a wide range oxygen (UEGO) sensor. Experiments were carried out under steady state conditions while maintaining the engine speed at 1600 r/min, setting the engine loads at 0%, 25%, 50%, 75% and 100% respectively. Throughout each test the EGR rate was kept at nine different settings and data were taken with the gas analyzer and UEGO sensor. Then, the EGR rate and engine load maps, which showed the tendencies of NOx, CO and HC emissions from diesel engine, were made using the measured data. Using the maps, the author set up the EGR regulation, the relationship between the optimal amounts of EGR flow and the equivalence ratio, sigma, where sigma = 14.5/AFR.

New operation strategy for driving the selectivity of NO x reduction to N 2, NH 3 or N 2O during lean/rich cycling of a lean NO x trap catalyst

DOE PAGES

Mráček, David; Koci, Petr; Choi, Jae -Soon; ...

2015-09-08

Periodical regeneration of NO x storage catalyst (also known as lean NO x trap) by short rich pulses of CO, H 2 and hydrocarbons is necessary for the reduction of nitrogen oxides adsorbed on the catalyst surface. Ideally, the stored NO x is converted into N 2, but N 2O and NH 3 by-products can be formed as well, particularly at low-intermediate temperatures. The N 2 and N 2O products are formed concurrently in two peaks. The primary peaks appear immediately after the rich-phase inception, and tail off with the breakthrough of the reductant front accompanied by NH 3 product.more » In addition, the secondary N 2 and N 2O peaks then appear at the rich-to-lean transition as a result of reactions between surface-deposited reductants/intermediates (CO, HC, NH 3, — NCO) and residual stored NO x under increasingly lean conditions.« less

CFD analysis of jet mixing in low NOx flametube combustors

NASA Technical Reports Server (NTRS)

Talpallikar, M. V.; Smith, C. E.; Lai, M. C.; Holdeman, J. D.

1991-01-01

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor was identified as a potential gas turbine combustor concept to reduce NO(x) emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NO(x) levels, cylindrical flametube versions of RQL combustors are being tested at NASA Lewis Research Center. A critical technology needed for the RQL combustor is a method of quickly mixing by-pass combustion air with rich-burn gases. Jet mixing in a cylindrical quick-mix section was numerically analyzed. The quick-mix configuration was five inches in diameter and employed twelve radial-inflow slots. The numerical analyses were performed with an advanced, validated 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Parametric variation of jet-to-mainstream momentum flux ratio (J) and slot aspect ratio was investigated. Both non-reacting and reacting analyses were performed. Results showed mixing and NO(x) emissions to be highly sensitive to J and slot aspect ratio. Lowest NO(x) emissions occurred when the dilution jet penetrated to approximately mid-radius. The viability of using 3-D CFD analyses for optimizing jet mixing was demonstrated.

CFD analysis of jet mixing in low NO(x) flametube combustors

NASA Technical Reports Server (NTRS)

Talpallikar, M. V.; Smith, C. E.; Lai, M. C.; Holdeman, J. D.

1991-01-01

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor has been identified as a potential gas turbine combustor concept to reduce NO(x) emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NO(x) levels, cylindrical flametube versions of RQL combustors are being tested at NASA Lewis Research Center. A critical technology needed for the RQL combustor is a method of quickly mixing by-pass combustion air with rich-burn gases. Jet mixing in a cylindrical quick-mix section was numerically analyzed. The quick-mix configuration was five inches in diameter and employed twelve radial-inflow slots. The numerical analyses were performed with an advanced, validated 3D Computational Fluid Dynamics (CFD) code named REFLEQS. Parametric variation of jet-to-mainstream momentum flux ratio (J) and slot aspect ratio was investigated. Both non-reacting and reacting analyses were performed. Results showed mixing and NO(x) emissions to be highly sensitive to J and slot aspect ratio. Lowest NO(x) emissions occurred when the dilution jet penetrated to approximately mid-radius. The viability of using 3D CFD analyses for optimizing jet mixing was demonstrated.

Development of Advanced Low Emission Injectors and High-Bandwidth Fuel Flow Modulation Valves

NASA Technical Reports Server (NTRS)

Mansour, Adel

2015-01-01

Parker Hannifin Corporation developed the 3-Zone fuel nozzle for NASA's Environmentally Responsible Aviation Program to meet NASAs target of 75 LTO NOx reduction from CAEP6 regulation. The nozzle concept was envisioned as a drop-in replacement for currently used fuel nozzle stem, and is built up from laminates to provide energetic mixing suitable for lean direct injection mode at high combustor pressure. A high frequency fuel valve was also developed to provide fuel modulation for the pilot injector. Final testing result shows the LTO NOx level falling just shy of NASAs goal at 31.

Compression Ratio and Catalyst Aging Effects on Aqueous Ethanol Ignition (Year 2): Part 1. Compression Ratio Effects on Aqueous Ethanol Ignition

DOT National Transportation Integrated Search

2009-09-01

The lean burning of water ethanol blends has the potential to reduce NOx, CO, and HC emissions while reducing the ethanol fermentation production cost of distillation and dehydration. The torch style ignition produced by the catalytic igniter allows ...

Modelling NOx emissions of single droplet combustion

NASA Astrophysics Data System (ADS)

Moesl, Klaus G.; Schwing, Joachim E.; Sattelmayer, Thomas

2012-02-01

An approach for modelling and simulation of the generation of nitrogen oxide (NOx) in the gas phase surrounding single burning droplets is presented. Assuming spherical symmetry (no gravity, no forced convection), the governing equations are derived first. Then simplifications are introduced and it is proven that they are appropriate. The influences of the initial droplet diameter, the ambient conditions, and the droplet pre-vapourisation on NOx are investigated. The fuel of choice is n-decane (C10H22) as it resembles kerosene and diesel fuel best, and the complexity of the reaction mechanism is manageable. Combinations of C10H22 mechanisms and well-established NOx kinetics are evaluated in detail and validated for their applicability in the context of this work. The conducted simulations of droplet combustion in an atmosphere of hot exhaust gas show that NOx formation (by mass of fuel) increases linearly with the droplet diameter. There is a trade-off between available oxygen and ambient temperature. Increasing the equivalence ratio of the exhaust gas leads to higher NOx emissions in the very lean regime, but to lower emissions if the equivalence ratio exceeds 0.85. Pre-vapourisation of fuel at ambient conditions becomes beneficial with respect to NOx emissions only if the degree of vapourisation is above a minimum limit. If less fuel is vapourised before ignition, the NOx emissions remain almost unaffected.

Laser Absorption Measurements of Equivalence Ratios Studied Along With Their Coupling to Pressure Fluctuations in Lean Premixed Prevaporized (LPP) Combustion

NASA Technical Reports Server (NTRS)

Nguyen, Quang-Viet

2001-01-01

Concerns about damaging the Earth's ozone layer as a result of high levels of nitrogen oxides (known collectively as NOx) from high-altitude, high-speed aircraft have prompted the study of lean premixed prevaporized (LPP) combustion in aircraft engines. LPP combustion reduces NOx emissions principally by reducing the peak flame temperatures inside an engine. Recent advances in LPP technologies have realized exceptional reductions in pollutant emissions (single-digit ppm NOx for example). However, LPP combustion also presents major challenges: combustion instability and dynamic coupling effects between fluctuations in heat-release rate, dynamic pressure, and fuel pressure. These challenges are formidable and can literally shake an engine apart if uncontrolled. To better understand this phenomenon so that it can be controlled, we obtained real-time laser absorption measurements of the fuel vapor concentration (and equivalence ratio) simultaneously with the dynamic pressure, flame luminosity, and time-averaged gaseous emissions measurements in a research-type jet-A-fueled LPP combustor. The measurements were obtained in NASA Glenn Research Center's CE-5B optically accessible flame tube facility. The CE-5B facility provides inlet air temperatures and pressures similar to the actual operating conditions of real aircraft engines. The laser absorption measurements were performed using an infrared 3.39 micron HeNe laser in conjunction with a visible HeNe laser for liquid droplet scattering compensation.

Mixing and NOx Emission Calculations of Confined Reacting Jet Flows in Cylindrical and Annular Ducts

NASA Technical Reports Server (NTRS)

Oechsle, Victor L.; Connor, Christopher H.; Holdeman, James D. (Technical Monitor)

2000-01-01

Rapid mixing of cold lateral jets with hot cross-stream flows in confined configurations is of practical interest in gas turbine combustors as it strongly affects combustor exit temperature quality, and gaseous emissions in for example rich-lean combustion. It is therefore important to further improve our fundamental understanding of the important processes of dilution jet mixing especially when the injected jet mass flow rate exceeds that of the cross-stream. The results reported in this report describe some of the main flow characteristics which develop in the mixing process in a cylindrical duct. A three-dimensional computational fluid dynamics (CFD) code has been used to predict the mixing flow field characteristics and NOx emission in a quench section of a rich-burn/quick-mix/lean-burn (RQL) combustor. Sixty configurations have been analyzed in both circular and annular geometries in a fully reacting environment simulating the operating condition of an actual RQL gas turbine combustion liner. The evaluation matrix was constructed by varying the number of orifices per row and orifice shape. Other parameters such as J (momentum-flux ratio), MR (mass flowrate ratio), DR (density ratio), and mixer sector orifice ACd (effective orifice area) were maintained constant throughout the entire study. The results indicate that the mixing flow field can be correlated with the NOx production if they are referenced with the stoichiometric equivalence ratio value and not the equilibrium value. The mixing flowfields in both circular and annular mixers are different. The penetration of equal jets in both annular and circular geometries is vastly different which significantly affects the performance of the mixing section. In the computational results with the circular mixer, most of the NOx formation occurred behind the orifice starting at the orifice wake region. General trends have been observed in the NOx production as the number of orifices is changed and this appears to be common for all hole configurations and mixer types (circular or annular). The performance of any orifice shape (in producing minimum NOx) appears to be acceptable if the number of orifices can be freely varied in order to attain the optimum jet penetration.

Emission characteristics of a premix combustor fueled with a simulated partial-oxidation product gas

NASA Technical Reports Server (NTRS)

Clayton, R. M.

1979-01-01

A two-stage gas turbine combustor concept employing a very fuel-rich partial oxidation stage is being explored for broadening the combustion margin between ultralow emissions and the lean stability limit. Combustion and emission results are presented for a series of experiments where a simulated partial oxidation product gas was used in a premix combustor operated with inlet air state conditions typical of cruise power for high-performance aviation engines (12 atm and 850 F). Ultralow NOx, CO, and HC emissions and an extended lean burning limit were achieved simultaneously.

Fuel and Combustor Concerns for Future Commercial Combustors

NASA Technical Reports Server (NTRS)

Chang, Clarence T.

2017-01-01

Civil aircraft combustor designs will move from rich-burn to lean-burn due to the latter's advantage in low NOx and nvPM emissions. However, the operating range of lean-burn is narrower, requiring premium mixing performance from the fuel injectors. As the OPR increases, the corresponding combustor inlet temperature increase can benefit greatly with fuel composition improvements. Hydro-treatment can improve coking resistance, allowing finer fuel injection orifices to speed up mixing. Selective cetane number control across the fuel carbon-number distribution may allow delayed ignition at high power while maintaining low-power ignition characteristics.

Method and apparatus to selectively reduce NO.sub.x in an exhaust gas feedstream

DOEpatents

Schmieg, Steven J [Troy, MI; Blint, Richard J [Shelby Township, MI; Den, Ling [Sterling Heights, MI; Viola, Michael B [Macomb Township, MI; Lee, Jong-Hwan [Rochester Hills, MI

2011-08-30

A method and apparatus are described to selectively reduce NO.sub.x emissions of an internal combustion engine. An exhaust aftertreatment system includes an injection device operative to dispense a hydrocarbon reductant upstream of a silver-alumina catalytic reactor device. A control system determines a NO.sub.x concentration and hydrocarbon/NOx ratio based upon selected parameters of the exhaust gas feedstream and dispenses hydrocarbon reductant during lean engine operation. Included is a method to control elements of the feedstream during lean operation. The hydrocarbon reductant may include engine fuel.

Numerical Study of Low Emission Gas Turbine Combustor Concepts

NASA Technical Reports Server (NTRS)

Yang, Song-Lin

2002-01-01

To further reduce pollutant emissions, such as CO, NO(x), UHCs, etc., in the next few decades, innovative concepts of gas turbine combustors must be developed. Several concepts, such as the LIPP (Lean- Premixed- Prevaporized), RQL (Rich-Burn Quick-Quench Lean-Burn), and LDI (Lean-Direct-Injection), have been under study for many years. To fully realize the potential of these concepts, several improvements, such as inlet geometry, air swirler, aerothermochemistry control, fuel preparation, fuel injection and injector design, etc., must be made, which can be studied through the experimental method and/or the numerical technique. The purpose of this proposal is to use the CFD technique to study, and hence, to guide the design process for low emission gas turbine combustors. A total of 13 technical papers have been (or will be) published.

Influence of H2O2 on LPG fuel performance evaluation

NASA Astrophysics Data System (ADS)

Khan, Muhammad Saad; Ahmed, Iqbal; Mutalib, Mohammad Ibrahim bin Abdul; Nadeem, Saad; Ali, Shahid

2014-10-01

The objective of this mode of combustion is to insertion of hydrogen peroxide (H2O2) to the Liquefied Petroleum Gas (LPG) combustion on spark plug ignition engines. The addition of hydrogen peroxide may probably decrease the formation of NOx, COx and unburned hydrocarbons. Hypothetically, Studies have shown that addition of hydrogen peroxide to examine the performance of LPG/H2O2 mixture in numerous volumetric compositions starting from lean LPG until obtaining a better composition can reduce the LPG fuel consumption. The theory behind this idea is that, the addition of H2O2 can cover the lean operation limit, increase the lean burn ability, diminution the burn duration along with controlling the exhaust emission by significantly reducing the greenhouse gaseous.

A CFD Study of Jet Mixing in Reduced Flow Areas for Lower Combustor Emissions

NASA Technical Reports Server (NTRS)

Smith, C. E.; Talpallikar, M. V.; Holdeman, J. D.

1991-01-01

The Rich-burn/Quick-mix/Lean-burn (RQL) combustor has the potential of significantly reducing NO(x) emissions in combustion chambers of High Speed Civil Transport aircraft. Previous work on RQL combustors for industrial applications suggested the benefit of necking down the mixing section. A 3-D numerical investigation was performed to study the effects of neckdown on NO(x) emissions and to develop a correlation for optimum mixing designs in terms of neckdown area ratio. The results of the study showed that jet mixing in reduced flow areas does not enhance mixing, but does decrease residence time at high flame temperatures, thus reducing NO(x) formation. By necking down the mixing flow area by 4, a potential NO(x) reduction of 16:1 is possible for annual combustors. However, there is a penalty that accompanies the mixing neckdown: reduced pressure drop across the combustor swirler. At conventional combustor loading parameters, the pressure drop penalty does not appear to be excessive.

Pollutant emissions from flat-flame burners at high pressures

NASA Technical Reports Server (NTRS)

Maahs, H. G.; Miller, I. M.

1980-01-01

Maximum flame temperatures and pollutant emission measurements for NOx, CO, and UHC (unburned hydrocarbons) are reported for premixed methane air flat flames at constant total mass flow rate over the pressure range from 1.9 to 30 atm and for equivalence ratios from 0.84 to 1.12. For any given pressure, maxima typically occur in both the temperature and NOx emissions curves slightly to the lean side of stoichiometric conditions. The UHC emissions show minima at roughly the same equivalence ratios. The CO emissions, however, increase continually with increasing equivalence ratio. Flame temperature and NOx emissions decrease with increasing pressure, while the opposite is true for the CO and UHC emissions. The NOx data correlate reasonably well as a function of flame temperature only. Four flameholders, differing only slightly, were used. In general, the temperature and emissions data from these four flameholders are similar, but some differences also exist. These differences appear to be related to minor variations in the condition of the flameholder surfaces.

Rich-burn, flame-assisted fuel cell, quick-mix, lean-burn (RFQL) combustor and power generation

NASA Astrophysics Data System (ADS)

Milcarek, Ryan J.; Ahn, Jeongmin

2018-03-01

Micro-tubular flame-assisted fuel cells (mT-FFC) were recently proposed as a modified version of the direct flame fuel cell (DFFC) operating in a dual chamber configuration. In this work, a rich-burn, quick-mix, lean-burn (RQL) combustor is combined with a micro-tubular solid oxide fuel cell (mT-SOFC) stack to create a rich-burn, flame-assisted fuel cell, quick-mix, lean-burn (RFQL) combustor and power generation system. The system is tested for rapid startup and achieves peak power densities after only 35 min of testing. The mT-FFC power density and voltage are affected by changes in the fuel-lean and fuel-rich combustion equivalence ratio. Optimal mT-FFC performance favors high fuel-rich equivalence ratios and a fuel-lean combustion equivalence ratio around 0.80. The electrical efficiency increases by 150% by using an intermediate temperature cathode material and improving the insulation. The RFQL combustor and power generation system achieves rapid startup, a simplified balance of plant and may have applications for reduced NOx formation and combined heat and power.

Lean stability augmentation study. [on gas turbine combustion chambers

NASA Technical Reports Server (NTRS)

Mcvey, J. B.; Kennedy, J. B.

1979-01-01

An analytical conceptual design study and an experimental test program were conducted to investigate techniques and develop technology for improving the lean combustion limits of premixing, prevaporizing combustors applicable to gas turbine engine main burners. The use of hot gas pilots, catalyzed flameholder elements, and heat recirculation to augment lean stability limits was considered in the conceptual design study. Tests of flameholders embodying selected concepts were conducted at a pressure of 10 arm and over a range of entrance temperatures simulating conditions to be encountered during stratospheric cruise. The tests were performed using an axisymmetric flametube test rig having a nominal diameter of 10.2 cm. A total of sixteen test configurations were examined in which lean blowout limits, pollutant emission characteristics, and combustor performance were evaluated. The use of a piloted perforated plate flameholder employing a pilot fuel flow rate equivalent to 4 percent of the total fuel flow at a simulated cruise condition resulted in a lean blowout equivalence ratio of less than 0.25 with a design point (T sub zero = 600k, Phi = 0.6) NOx emission index of less than 1.0 g/kg.

Investigation of a low NOx full-scale annular combustor

NASA Technical Reports Server (NTRS)

1982-01-01

An atmospheric test program was conducted to evaluate a low NOx annular combustor concept suitable for a supersonic, high-altitude aircraft application. The lean premixed combustor, known as the vortex air blast (VAB) concept, was tested as a 22.0-cm diameter model in the early development phases to arrive at basic design and performance criteria. Final demonstration testing was carried out on a full scale combustor of 0.66-m diameter. Variable geometry dilution ports were incorporated to allow operation of the combustor across the range of conditions between idle (T(in) = 422 K, T(out) = 917 K) and cruise (T(in) = 833 K, T(out) - 1778 K). Test results show that the design could meet the program NOx goal of 1.0 g NO2/kg fuel at a one-atmospheric simulated cruise condition.

Exhaust emission control and diagnostics

DOEpatents

Mazur, Christopher John; Upadhyay, Devesh

2006-11-14

A diesel engine emission control system uses an upstream oxidation catalyst and a downstream SCR catalyst to reduce NOx in a lean exhaust gas environment. The engine and upstream oxidation catalyst are configured to provide approximately a 1:1 ratio of NO to NO2 entering the downstream catalyst. In this way, the downstream catalyst is insensitive to sulfur contamination, and also has improved overall catalyst NOx conversion efficiency. Degradation of the system is determined when the ratio provided is no longer near the desired 1:1 ratio. This condition is detected using measurements of engine operating conditions such as from a NOx sensor located downstream of the catalysts. Finally, control action to adjust an injected amount of reductant in the exhaust gas based on the actual NO to NO2 ratio upstream of the SCR catalyst and downstream of the oxidation catalyst.

An Assessment of Combustion Dynamics in a Low-Nox, Second-Generation Swirl-Venturi Lean Direct Injection Combustion Concept

NASA Technical Reports Server (NTRS)

Tacina, K. M.; Chang, C. T.; Lee, P.; Mongia, H.; Podboy, D. P.; Dam, B.

2015-01-01

Dynamic pressure measurements were taken during flame-tube emissions testing of three second-generation swirl-venturi lean direct injection (SV-LDI) combustor configurations. These measurements show that combustion dynamics were typically small. However, a small number of points showed high combustion dynamics, with peak-to-peak dynamic pressure fluctuations above 0.5 psi. High combustion dynamics occurred at low inlet temperatures in all three SV-LDI configurations, so combustion dynamics were explored further at low temperature conditions. A point with greater than 1.5 psi peak-to-peak dynamic pressure fluctuations was identified at an inlet temperature of 450!F, a pressure of 100 psia, an air pressure drop of 3%, and an overall equivalence ratio of 0.35. This is an off design condition: the temperature and pressure are typical of 7% power conditions, but the equivalence ratio is high. At this condition, the combustion dynamics depended strongly on the fuel staging. Combustion dynamics could be reduced significantly without changing the overall equivalence ratio by shifting the fuel distribution between stages. Shifting the fuel distribution also decreased NOx emissions.

The Effect of Spray Initial Conditions on Heat Release and Emissions in LDI CFD Calculations

NASA Technical Reports Server (NTRS)

Iannetti, Anthony C.; Liu, Nan-Suey; Davoudzadeh, Farhad

2008-01-01

The mass and velocity distribution of liquid spray has a primary effect on the combustion heat release process. This heat release process then affects emissions like nitrogen oxides (NOx) and carbon monoxide (CO). Computational Fluid Dynamics gives the engineer insight into these processes, but various setup options exist (number of droplet groups, and initial droplet temperature) for spray initial conditions. This paper studies these spray initial condition options using the National Combustion Code (NCC) on a single swirler lean direct injection (LDI) flame tube. Using laminar finite rate chemistry, comparisons are made against experimental data for velocity measurements, temperature, and emissions (NOx, CO).

Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor

NASA Technical Reports Server (NTRS)

Roffe, G.; Raman, R. S. V.

1981-01-01

Tests were run using a perforated plate flameholder with a relatively short attached recirculation zone and a vee gutter flameholder with a relatively long attached recirculation zone. Combustor streamlines were traced in cold flow tests at ambient pressure. The amount of secondary air entrainment in the recirculation zones of the flameholders was determined by tracer gas testing at cold flow ambient pressure conditions. Combustion tests were caried out at entrance conditions of 0.5 MPa/630K and emission of NOx, CO and unburned hydrocarbons were measured along with lean stability and flashback limits. The degree of entrainment increases as dilution air injection decreases. Flashback appears to be a function of overall equivalence ratio and resistance to flashback increases with increasing combustor entrance velocity. Lean stability limit appears to be a function of both primary zone and flameholder recirculation zone equivalence ratios and resistance to lean blowout increases with increasing combustor entrance velocity.

Emission Characteristics of A P and W Axially Staged Sector Combustor

NASA Technical Reports Server (NTRS)

He, Zhuohui J.; Wey, Changlie; Chang, Clarence T.; Lee, Chi Ming; Surgenor, Angela D.; Kopp-Vaughan, Kristin; Cheung, Albert

2016-01-01

Emission characteristics of a three-cup P and W Axially Controlled Stoichiometry (ACS) sector combustor are reported in this article. Multiple injection points and fuel staging strategies are used in this combustor design. Pilot-stage injectors are located on the front dome plate of the combustor, and main-stage injectors are positioned on the top and bottom of the combustor liners downstream. Low power configuration uses only pilot-stage injectors. Main-stage injectors are added to high power configuration to help distribute fuel more evenly and achieve overall lean burn yielding very low NOx emissions. Combustion efficiencies at four ICAO LTO conditions were all above 99%. Three EINOx emissions correlation equations were developed based on the experimental data to describe the NOx emission trends of this combustor concept. For the 7% and 30% engine power conditions, NOx emissions are obtained with the low power configuration, and the EINOx values are 6.16 and 6.81. The high power configuration was used to assess 85% and 100% engine power NOx emissions, with measured EINOx values of 4.58 and 7.45, respectively. The overall landing-takeoff cycle NOx emissions are about 12% relative to ICAO CAEP/6 level.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Technical Reports Server (NTRS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-01-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Numerical Simulation of Wall Heat Load in Combustor Flow

NASA Astrophysics Data System (ADS)

Panara, D.; Hase, M.; Krebs, W.; Noll, B.

2007-09-01

Due to the major mechanism of NOx generation, there is generally a temperature trade off between improved cycle efficiency, material constraints and low NOx emission. The cycle efficiency is proportional to the highest cycle temperature, but unfortunately also the NOx production increases with increasing combustion temperature. For this reason, the modern combustion chamber design has been oriented towards lean premixed combustion system and more and more attention must be focused on the cooling air management. The challenge is to ensure sufficiently low temperature of the combustion liner with very low amount of film or effusion cooling air. Correct numerical prediction of temperature fields and wall heat load are therefore of critical interest in the modern combustion chamber design. Moreover, lean combustion technology has shown the appearance of thermo-acoustic instabilities which have to be taken into account in the simulation and, more in general, in the design of reliable combustion systems. In this framework, the present investigation addresses the capability of a commercial multiphysics code (ANSYS CFX) to correctly predict the wall heat load and the core flow temperature field in a scaled power generation combustion chamber with a simplified ceramic liner. Comparison are made with the experimental results from the ITS test rig at the University of Karlsruhe [1] and with a previous numerical campaign from [2]. In addition the effect of flow unsteadyness on the wall heat load is discussed showing some limitations of the traditional steady state flow thermal design.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Astrophysics Data System (ADS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-07-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Astrophysics Data System (ADS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-06-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Effects of Sulfation Level on the Desulfation Behavior of Presulfated Pt-BaO/Al2O3 Lean NOx Trap Catalysts: A Combined H2 Temperature-Programmed Reaction, in Situ Sulfur K-Edge X-ray Absorption Near-Edge Spectroscopy, X-ray Photoelectron Spectroscopy, and Time-Resolved X-ray Diffraction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, D.H.; Hanson, J.; Szanyi, J.

2009-04-30

Desulfation by hydrogen of presulfated Pt (2 wt %)-BaO(20 wt %)/Al{sub 2}O{sub 3} with various sulfur loading (S/Ba = 0.12, 0.31, and 0.62) were investigated by combining H{sub 2} temperature programmed reaction (TPRX), X-ray photoelectron spectroscopy (XPS), in situ sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved X-ray diffraction (TR-XRD) techniques. We find that the amount of H{sub 2}S desorbed during the desulfation in the H{sub 2} TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates weremore » transformed to a BaS phase and remained in the catalyst rather than being removed as H{sub 2}S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H{sub 2}S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H{sub 2}O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H{sub 2}S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt-BaO/Al{sub 2}O{sub 3} lean NO{sub x} trap catalysts is markedly dependent on the sulfation levels.« less

Characteristics of a trapped-vortex (TV) combustor

NASA Technical Reports Server (NTRS)

Hsu, K.-Y.; Gross, L. P.; Trump, D. D.; Roquemore, W. M.

1994-01-01

The characteristics of a Trapped-Vortex (TV) combustor are presented. A vortex is trapped in the cavity established between two disks mounted in tandem. Fuel and air are injected directly into the cavity in such a way as to increase the vortex strength. Some air from the annular flow is also entrained into the recirculation zone of the vortex. Lean blow-out limits of the combustor are determined for a wide range of annular air flow rates. These data indicate that the lean blow-out limits are considerably lower for the TV combustor than for flames stabilized using swirl or bluff-bodies. The pressure loss through the annular duct is also low, being less than 2% for the flow conditions in this study. The instantaneous shape of the recirculation zone of the trapped vortex is measured using a two-color PIV technique. Temperature profiles obtained with CARS indicate a well mixed recirculation zone and demonstrate the impact of primary air injection on the local equivalence ratio.

DeNOx Abatement over Sonically Prepared Iron-Substituted Y, USY and MFI Zeolite Catalysts in Lean Exhaust Gas Conditions

PubMed Central

Stachurska, Patrycja; Kuterasiński, Łukasz; Dziedzicka, Anna; Górecka, Sylwia; Chmielarz, Lucjan; Łojewska, Joanna; Sitarz, Maciej

2018-01-01

Iron-substituted MFI, Y and USY zeolites prepared by two preparation routes—classical ion exchange and the ultrasound modified ion-exchange method—were characterised by micro-Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet (UV)/visible diffuse reflectance spectroscopy (UV/Vis DRS). Ultrasound irradiation, a new technique for the preparation of the metal salt suspension before incorporation to the zeolite structure, was employed. An experimental study of selective catalytic reduction (SCR) of NO with NH3 on both iron-substituted reference zeolite catalysts and those prepared through the application of ultrasound conducted during an ion-exchange process is presented. The prepared zeolite catalysts show high activity and selectivity in SCR deNOx abatement. The MFI-based iron catalysts, especially those prepared via the sonochemical method, revealed superior activity in the deNOx process, with almost 100% selectivity towards N2. The hydrothermal stability test confirmed high stability and activity of MFI-based catalysts in water-rich conditions during the deNOx reaction at 450 °C. PMID:29301370

Low Emissions RQL Flametube Combustor Test Results

NASA Technical Reports Server (NTRS)

Chang, Clarence T.; Holdeman, James D.

2001-01-01

The overall objective of this test program was to demonstrate and evaluate the capability of the Rich-burn/Quick-mix/Lean-burn (RQL) combustor concept for HSR applications. This test program was in support of the Pratt & Whitney and GE Aircraft Engines HSR low-NOx Combustor Program. Collaborative programs with Parker Hannifin Corporation and Textron Fuel Systems resulted in the development and testing of the high-flow low-NOx rich-burn zone fuel-to-air ratio research fuel nozzles used in this test program. Based on the results obtained in this test program, several conclusions can be made: (1) The RQL tests gave low NOx and CO emissions results at conditions corresponding to HSR cruise. (2) The Textron fuel nozzle design with optimal multiple partitioning of fuel and air circuits shows potential of providing an acceptable uniform local fuel-rich region in the rich burner. (3) For the parameters studied in this test series, the tests have shown T3 is the dominant factor in the NOx formation for RQL combustors. As T3 increases from 600 to 1100 F, EI(NOx) increases approximately three fold. (4) Factors which appear to have secondary influence on NOx formation are P4, T4, infinity(sub rb), V(sub ref,ov). (5) Low smoke numbers were measured for infinity(sub rb) of 2.0 at P4 of 120 psia.

A chemical reactor network for oxides of nitrogen emission prediction in gas turbine combustor

NASA Astrophysics Data System (ADS)

Hao, Nguyen Thanh

2014-06-01

This study presents the use of a new chemical reactor network (CRN) model and non-uniform injectors to predict the NOx emission pollutant in gas turbine combustor. The CRN uses information from Computational Fluid Dynamics (CFD) combustion analysis with two injectors of CH4-air mixture. The injectors of CH4-air mixture have different lean equivalence ratio, and they control fuel flow to stabilize combustion and adjust combustor's equivalence ratio. Non-uniform injector is applied to improve the burning process of the turbine combustor. The results of the new CRN for NOx prediction in the gas turbine combustor show very good agreement with the experimental data from Korea Electric Power Research Institute.

An intelligent emissions controller for fuel lean gas reburn in coal-fired power plants.

PubMed

Reifman, J; Feldman, E E; Wei, T Y; Glickert, R W

2000-02-01

The application of artificial intelligence techniques for performance optimization of the fuel lean gas reburn (FLGR) system is investigated. A multilayer, feedforward artificial neural network is applied to model static nonlinear relationships between the distribution of injected natural gas into the upper region of the furnace of a coal-fired boiler and the corresponding oxides of nitrogen (NOx) emissions exiting the furnace. Based on this model, optimal distributions of injected gas are determined such that the largest NOx reduction is achieved for each value of total injected gas. This optimization is accomplished through the development of a new optimization method based on neural networks. This new optimal control algorithm, which can be used as an alternative generic tool for solving multidimensional nonlinear constrained optimization problems, is described and its results are successfully validated against an off-the-shelf tool for solving mathematical programming problems. Encouraging results obtained using plant data from one of Commonwealth Edison's coal-fired electric power plants demonstrate the feasibility of the overall approach. Preliminary results show that the use of this intelligent controller will also enable the determination of the most cost-effective operating conditions of the FLGR system by considering, along with the optimal distribution of the injected gas, the cost differential between natural gas and coal and the open-market price of NOx emission credits. Further study, however, is necessary, including the construction of a more comprehensive database, needed to develop high-fidelity process models and to add carbon monoxide (CO) emissions to the model of the gas reburn system.

CRADA Final Report for CRADA Number ORNL00-0605: Advanced Engine/Aftertreatment System R&D

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pihl, Josh A; West, Brian H; Toops, Todd J

2011-10-01

Navistar and ORNL established this CRADA to develop diesel engine aftertreatment configurations and control strategies that could meet emissions regulations while maintaining or improving vehicle efficiency. The early years of the project focused on reducing the fuel penalty associated with lean NOx trap (LNT), also known as NOx adsorber catalyst regeneration and desulfation. While Navistar pursued engine-based (in-cylinder) approaches to LNT regeneration, complementary experiments at ORNL focused on in-exhaust fuel injection. ORNL developed a PC-based controller for transient electronic control of EGR valve position, intake throttle position, and actuation of fuel injectors in the exhaust system of a Navistar enginemore » installed at Oak Ridge. Aftertreatment systems consisting of different diesel oxidation catalysts (DOCs) in conjunction with a diesel particle filter and LNT were evaluated under quasi-steady-state conditions. Hydrocarbon (HC) species were measured at multiple locations in the exhaust system with Gas chromatograph mass spectrometry (GC-MS) and Fourier transform infrared (FTIR) spectroscopy. Under full-load, rated speed conditions, injection of fuel upstream of the DOC reduced the fuel penalty for a given level of NOx reduction by 10-20%. GC-MS showed that fuel compounds were 'cracked' into smaller hydrocarbon species over the DOC, particularly light alkenes. GC-MS analysis of HC species entering and exiting the LNT showed high utilization of light alkenes, followed by mono-aromatics; branched alkanes passed through the LNT largely unreacted. Follow-on experiments at a 'road load' condition were conducted, revealing that the NOx reduction was better without the DOC at lower temperatures. The improved performance was attributed to the large swings in the NOx adsorber core temperature. Split-injection experiments were conducted with ultra-low sulfur diesel fuel and three pure HC compounds: 1-pentene, toluene, and iso-octane. The pure compound experiments confirmed the previous results regarding hydrocarbon reactivity: 1-pentene was the most efficient LNT reductant, followed by toluene. Injection location had minimal impact on the reactivity of these two compounds. Iso-octane was an ineffective LNT reductant, requiring high doses (resulting in high HC emissions) to achieve reasonable NOx conversions. Diesel fuel reactivity was sensitive to injection location, with the best performance achieved through fuel injection downstream of the DOC. This configuration generated large LNT temperature excursions, which probably improved the efficiency of the NOx storage/reduction process, but also resulted in very high HC emissions. The ORNL team demonstrated an LNT desulfation under 'road load' conditions using throttling, EGR, and in-pipe injection of diesel fuel. Flow reactor characterization of core samples cut from the front and rear of the engine-aged LNT revealed complex spatially dependent degradation mechanisms. The front of the catalyst contained residual sulfates, which impacted NOx storage and conversion efficiencies at high temperatures. The rear of the catalyst showed significant sintering of the washcoat and precious metal particles, resulting in lower NOx conversion efficiencies at low temperatures. Further flow reactor characterization of engine-aged LNT core samples established that low temperature performance was limited by slow release and reduction of stored NOx during regeneration. Carbon monoxide was only effective at regenerating the LNT at temperatures above 200 C; propene was unreactive even at 250 C. Low temperature operation also resulted in unselective NOx reduction, resulting in high emissions of both N{sub 2}O and NH{sub 3}. During the latter years of the CRADA, the focus was shifted from LNTs to other aftertreatment devices. Two years of the CRADA were spent developing detailed ammonia SCR device models with sufficient accuracy and computational efficiency to be used in development of model-based ammonia injection control algorithms.ORNL, working closely with partners at Navistar and Mi« less

Filter-based control of particulate matter from a lean gasoline direct injection engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parks, II, James E; Lewis Sr, Samuel Arthur; DeBusk, Melanie Moses

New regulations requiring increases in vehicle fuel economy are challenging automotive manufacturers to identify fuel-efficient engines for future vehicles. Lean gasoline direct injection (GDI) engines offer significant increases in fuel efficiency over the more common stoichiometric GDI engines already in the marketplace. However, particulate matter (PM) emissions from lean GDI engines, particularly during stratified combustion modes, are problematic for lean GDI technology to meet U.S. Environmental Protection Agency Tier 3 and other future emission regulations. As such, the control of lean GDI PM with wall-flow filters, referred to as gasoline particulate filter (GPF) technology, is of interest. Since lean GDImore » PM chemistry and morphology differ from diesel PM (where more filtration experience exists), the functionality of GPFs needs to be studied to determine the operating conditions suitable for efficient PM removal. In addition, lean GDI engine exhaust temperatures are generally higher than diesel engines which results in more continuous regeneration of the GPF and less presence of the soot cake layer common to diesel particulate filters. Since the soot layer improves filtration efficiency, this distinction is important to consider. Research on the emission control of PM from a lean GDI engine with a GPF was conducted on an engine dynamometer. PM, after dilution, was characterized with membrane filters, organic vs. elemental carbon characterization, and size distribution techniques at various steady state engine speed and load points. The engine was operated in three primary combustion modes: stoichiometric, lean homogeneous, and lean stratified. In addition, rich combustion was utilized to simulate PM from engine operation during active regeneration of lean NOx control technologies. High (>95%) PM filtration efficiencies were observed over a wide range of conditions; however, some PM was observed to slip through the GPF at high speed and load conditions. The PM characterization at various engine speeds and loads will help enable optimized GPF design and control to achieve more fuel efficient lean GDI vehicles with low PM emissions.« less

LPG gaseous phase electronic port injection on performance, emission and combustion characteristics of Lean Burn SI Engine

NASA Astrophysics Data System (ADS)

Bhasker J, Pradeep; E, Porpatham

2016-08-01

Gaseous fuels have always been established as an assuring way to lessen emissions in Spark Ignition engines. In particular, LPG resolved to be an affirmative fuel for SI engines because of their efficient combustion properties, lower emissions and higher knock resistance. This paper investigates performance, emission and combustion characteristics of a microcontroller based electronic LPG gaseous phase port injection system. Experiments were carried out in a single cylinder diesel engine altered to behave as SI engine with LPG as fuel at a compression ratio of 10.5:1. The engine was regulated at 1500 rpm at a throttle position of 20% at diverse equivalence ratios. The test results were compared with that of the carburetion system. The results showed that there was an increase in brake power output and brake thermal efficiency with LPG gas phase injection. There was an appreciable extension in the lean limit of operation and maximum brake power output under lean conditions. LPG injection technique significantly reduces hydrocarbon and carbon monoxide emissions. Also, it extremely enhances the rate of combustion and helps in extending the lean limit of LPG. There was a minimal increase of NOx emissions over the lean operating range due to higher temperature. On the whole it is concluded that port injection of LPG is best suitable in terms of performance and emission for LPG fuelled lean burn SI engine.

Emissions of an AVCO Lycoming 0-320-DIAD air cooled light aircraft engine as a function of fuel-air ratio, timing, and air temperature and humidity

NASA Technical Reports Server (NTRS)

Meng, P. R.; Skorobatckyi, M.; Cosgrove, D. V.; Kempke, E. E., Jr.

1976-01-01

A carbureted aircraft engine was operated over a range of test conditions to establish the exhaust levels over the EPA seven-mode emissions cycle. Baseline (full rich production limit) exhaust emissions at an induction air temperature of 59 F and near zero relative humidity were 90 percent of the EPA standard for HC, 35 percent for NOx, and 161 percent for CO. Changes in ignition timing around the standard 25 deg BTDC from 30 deg BTDC to 20 deg BTDC had little effect on the exhaust emissions. Retarding the timing to 15 deg BTDC increased both the HC and CO emissions and decreased NOx emissions. HC and CO emissions decreased as the carburetor was leaned out, while NOx emissions increased. The EPA emission standards were marginally achieved at two leanout conditions. Variations in the quantity of cooling air flow over the engine had no effect on exhaust emissions. Temperature-humidity effects at the higher values of air temperature and relative humidity tested indicated that the HC and CO emissions increased significantly, while the NOx emissions decreased.

Evaluation of concepts for controlling exhaust emissions from minimally processed petroleum and synthetic fuels

NASA Technical Reports Server (NTRS)

Russell, P. L.; Beal, G. W.; Sederquist, R. A.; Shultz, D.

1981-01-01

Rich-lean combustor concepts designed to enhance rich combustion chemistry and increase combustor flexibility for NO(x) reduction with minimally processed fuels are examined. Processes such as rich product recirculation in the rich chamber, rich-lean annihilation, and graduated air addition or staged rich combustion to release bound nitrogen in steps of reduced equivalence ratio are discussed. Variations to the baseline rapid quench section are considered, and the effect of residence time in the rich zone is investigated. The feasibility of using uncooled non-metallic materials for the rich zone combustion construction is also addressed. The preliminary results indicate that rich primary zone staged combustion provides environmentally acceptable operation with residual and/or synthetic coal-derived liquid fuels

Reducing NOx Emissions for a 600 MWe Down-Fired Pulverized-Coal Utility Boiler by Applying a Novel Combustion System.

PubMed

Ma, Lun; Fang, Qingyan; Lv, Dangzhen; Zhang, Cheng; Chen, Yiping; Chen, Gang; Duan, Xuenong; Wang, Xihuan

2015-11-03

A novel combustion system was applied to a 600 MWe Foster Wheeler (FW) down-fired pulverized-coal utility boiler to solve high NOx emissions, without causing an obvious increase in the carbon content of fly ash. The unit included moving fuel-lean nozzles from the arches to the front/rear walls and rearranging staged air as well as introducing separated overfire air (SOFA). Numerical simulations were carried out under the original and novel combustion systems to evaluate the performance of combustion and NOx emissions in the furnace. The simulated results were found to be in good agreement with the in situ measurements. The novel combustion system enlarged the recirculation zones below the arches, thereby strengthening the combustion stability considerably. The coal/air downward penetration depth was markedly extended, and the pulverized-coal travel path in the lower furnace significantly increased, which contributed to the burnout degree. The introduction of SOFA resulted in a low-oxygen and strong-reducing atmosphere in the lower furnace region to reduce NOx emissions evidently. The industrial measurements showed that NOx emissions at full load decreased significantly by 50%, from 1501 mg/m3 (O2 at 6%) to 751 mg/m3 (O2 at 6%). The carbon content in the fly ash increased only slightly, from 4.13 to 4.30%.

High Pressure Low NOx Emissions Research: Recent Progress at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Chi-Ming, Lee; Tacina, Kathleen M.; Wey, Changlie

2007-01-01

In collaboration with U.S. aircraft engine companies, NASA Glenn Research Center has contributed to the advancement of low emissions combustion systems. For the High Speed Research Program (HSR), a 90% reduction in nitrogen oxides (NOx) emissions (relative to the then-current state of the art) has been demonstrated in sector rig testing at General Electric Aircraft Engines (GEAE). For the Advanced Subsonic Technology Program (AST), a 50% reduction in NOx emissions relative to the 1996 International Civil Aviation Organization (ICAO) standards has been at demonstrated in sector rigs at both GEAE and Pratt & Whitney (P&W). During the Ultra Efficient Engine Technology Program (UEET), a 70% reduction in NOx emissions, relative to the 1996 ICAO standards, was achieved in sector rig testing at Glenn in the world class Advanced Subsonic Combustion Rig (ASCR) and at contractor facilities. Low NOx combustor development continues under the Fundamental Aeronautics Program. To achieve these reductions, experimental and analytical research has been conducted to advance the understanding of emissions formation in combustion processes. Lean direct injection (LDI) concept development uses advanced laser-based non-intrusive diagnostics and analytical work to complement the emissions measurements and to provide guidance for concept improvement. This paper describes emissions results from flametube tests of a 9- injection-point LDI fuel/air mixer tested at inlet pressures up to 5500 kPa. Sample results from CFD and laser diagnostics are also discussed.

NASA Glenn High Pressure Low NOx Emissions Research

NASA Technical Reports Server (NTRS)

Tacina, Kathleen M.; Wey, Changlie

2008-01-01

In collaboration with U.S. aircraft engine companies, NASA Glenn Research Center has contributed to the advancement of low emissions combustion systems. For the High Speed Research Program (HSR), a 90% reduction in nitrogen oxides (NOx) emissions (relative to the then-current state of the art) has been demonstrated in sector rig testing at General Electric Aircraft Engines (GEAE). For the Advanced Subsonic Technology Program (AST), a 50% reduction in NOx emissions relative to the 1996 International Civil Aviation Organization (ICAO) standards has been demonstrated in sector rigs at both GEAE and Pratt & Whitney (P&W). During the Ultra Efficient Engine Technology Program (UEET), a 70% reduction in NOx emissions, relative to the 1996 ICAO standards, was achieved in sector rig testing at Glenn in the world class Advanced Subsonic Combustion Rig (ASCR) and at contractor facilities. Low NOx combustor development continues under the Fundamental Aeronautics Program. To achieve these reductions, experimental and analytical research has been conducted to advance the understanding of emissions formation in combustion processes. Lean direct injection (LDI) concept development uses advanced laser-based non-intrusive diagnostics and analytical work to complement the emissions measurements and to provide guidance for concept improvement. This paper describes emissions results from flametube tests of a 9-injection-point LDI fuel/air mixer tested at inlet pressures up to 5500 kPa. Sample results from CFD and laser diagnostics are also discussed.

National Combustion Code Validated Against Lean Direct Injection Flow Field Data

NASA Technical Reports Server (NTRS)

Iannetti, Anthony C.

2003-01-01

Most combustion processes have, in some way or another, a recirculating flow field. This recirculation stabilizes the reaction zone, or flame, but an unnecessarily large recirculation zone can result in high nitrogen oxide (NOx) values for combustion systems. The size of this recirculation zone is crucial to the performance of state-of-the-art, low-emissions hardware. If this is a large-scale combustion process, the flow field will probably be turbulent and, therefore, three-dimensional. This research dealt primarily with flow fields resulting from lean direct injection (LDI) concepts, as described in Research & Technology 2001. LDI is a concept that depends heavily on the design of the swirler. The LDI concept has the potential to reduce NOx values from 50 to 70 percent of current values, with good flame stability characteristics. It is cost effective and (hopefully) beneficial to do most of the design work for an LDI swirler using computer-aided design (CAD) and computer-aided engineering (CAE) tools. Computational fluid dynamics (CFD) codes are CAE tools that can calculate three-dimensional flows in complex geometries. However, CFD codes are only beginning to correctly calculate the flow fields for complex devices, and the related combustion models usually remove a large portion of the flow physics.

Mixing and NO(x) Emission Calculations of Confined Reacting Jet Flows in a Cylindrical Duct

NASA Technical Reports Server (NTRS)

Holdeman, James D. (Technical Monitor); Oechsle, Victor L.

2003-01-01

Rapid mixing of cold lateral jets with hot cross-stream flows in confined configurations is of practical interest in gas turbine combustors as it strongly affects combustor exit temperature quality, and gaseous emissions in for example rich-lean combustion. It is therefore important to further improve our fundamental understanding of the important processes of dilution jet mixing especially when the injected jet mass flow rate exceeds that of the cross-stream. The results reported in this report describe some of the main flow characteristics which develop in the mixing process in a cylindrical duct. A 3-dimensional tool has been used to predict the mixing flow field characteristics and NOx emission in a quench section of an RQL combustor, Eighteen configurations have been analyzed in a circular geometry in a fully reacting environment simulating the operating condition of an actual RQL gas turbine combustion liner. The evaluation matrix was constructed by varying three parameters: 1) jet-to-mainstream momentum-flux ratio (J), 2) orifice shape or orifice aspect ratio, and 3) slot slant angle. The results indicate that the mixing flow field significantly varies with the value of the jet penetration and subsequently, slanting elongated slots generally improve the mixing uniformity at high J conditions. Round orifices produce more uniform mixing and low NO(x) emissions at low J due to the strong and adequate jet penetration. No significant correlation was found between the NO(x) production rates and the mixing deviation parameters, however, strong correlation was found between NO(x) formation and jet penetration. In the computational results, most of the NO(x) formation occurred behind the orifice starting at the orifice wake region. Additional NO(x) is formed upstream of the orifice in certain configurations with high J conditions due to the upstream recirculation.

Effects of spark plug configuration on combustion and emission characteristics of a LPG fuelled lean burn SI engine

NASA Astrophysics Data System (ADS)

Ravi, K.; Khan, Manazir Ahmed; Pradeep Bhasker, J.; Porpatham, E.

2017-11-01

Introduction of technological innovation in automotive engines in reducing pollution and increasing efficiency have been under contemplation. Gaseous fuels have proved to be a promising way to reduce emissions in Spark Ignition (SI) engines. In particular, LPG settled to be a favourable fuel for SI engines because of their higher hydrogen to carbon ratio, octane rating and lower emissions. Wide ignition limits and efficient combustion characteristics make LPG suitable for lean burn operation. But lean combustion technology has certain drawbacks like poor flame propagation, cyclic variations etc. Based on copious research it was found that location, types and number of spark plug significantly influence in reducing cyclic variations. In this work the influence of single and dual spark plugs of conventional and surface discharge electrode type were analysed. Dual surface discharge electrode spark plug enhanced the brake thermal efficiency and greatly reduced the cyclic variations. The experimental results show that rate of heat release and pressure rise was more and combustion duration was shortened in this configuration. On the emissions front, the NOx emission has increased whereas HC and CO emissions were reduced under lean condition.

Hypertonic Saline Suppresses NADPH Oxidase-Dependent Neutrophil Extracellular Trap Formation and Promotes Apoptosis.

PubMed

Nadesalingam, Ajantha; Chen, Jacky H K; Farahvash, Armin; Khan, Meraj A

2018-01-01

Tonicity of saline (NaCl) is important in regulating cellular functions and homeostasis. Hypertonic saline is administered to treat many inflammatory diseases, including cystic fibrosis. Excess neutrophil extracellular trap (NET) formation, or NETosis, is associated with many pathological conditions including chronic inflammation. Despite the known therapeutic benefits of hypertonic saline, its underlying mechanisms are not clearly understood. Therefore, we aimed to elucidate the effects of hypertonic saline in modulating NETosis. For this purpose, we purified human neutrophils and induced NETosis using agonists such as diacylglycerol mimetic phorbol myristate acetate (PMA), Gram-negative bacterial cell wall component lipopolysaccharide (LPS), calcium ionophores (A23187 and ionomycin from Streptomyces conglobatus ), and bacteria ( Pseudomonas aeruginosa and Staphylococcus aureus ). We then analyzed neutrophils and NETs using Sytox green assay, immunostaining of NET components and apoptosis markers, confocal microscopy, and pH sensing reagents. This study found that hypertonic NaCl suppresses nicotinamide adenine dinucleotide phosphate oxidase (NADPH2 or NOX2)-dependent NETosis induced by agonists PMA, Escherichia coli LPS (0111:B4 and O128:B12), and P. aeruginosa . Hypertonic saline also suppresses LPS- and PMA- induced reactive oxygen species production. It was determined that supplementing H 2 O 2 reverses the suppressive effect of hypertonic saline on NOX2-dependent NETosis. Many of the aforementioned suppressive effects were observed in the presence of equimolar concentrations of choline chloride and osmolytes (d-mannitol and d-sorbitol). This suggests that the mechanism by which hypertonic saline suppresses NOX2-dependent NETosis is via neutrophil dehydration. Hypertonic NaCl does not significantly alter the intracellular pH of neutrophils. We found that hypertonic NaCl induces apoptosis while suppressing NOX2-dependent NETosis. In contrast, hypertonic solutions do not suppress NOX2-independent NETosis. Although hypertonic saline partially suppresses ionomycin-induced NETosis, it enhances A23187-induced NETosis, and it does not alter S. aureus -induced NETosis. Overall, this study determined that hypertonic saline suppresses NOX2-dependent NETosis induced by several agonists; in contrast, it has variable effects on neutrophil death induced by NOX2-independent NETosis agonists. These findings are important in understanding the regulation of NETosis and apoptosis in neutrophils.

Measurement and Computation of Supersonic Flow in a Lobed Diffuser-Mixer for Trapped Vortex Combustors

NASA Technical Reports Server (NTRS)

Brankovic, Andreja; Ryder, Robert C., Jr.; Hendricks, Robert C.; Liu, Nan-Suey; Gallagher, John R.; Shouse, Dale T.; Roquemore, W. Melvyn; Cooper, Clayton S.; Burrus, David L.; Hendricks, John A.

2002-01-01

The trapped vortex combustor (TVC) pioneered by Air Force Research Laboratories (AFRL) is under consideration as an alternative to conventional gas turbine combustors. The TVC has demonstrated excellent operational characteristics such as high combustion efficiency, low NO(x) emissions, effective flame stabilization, excellent high-altitude relight capability, and operation in the lean-burn or rich burn-quick quench-lean burn (RQL) modes of combustion. It also has excellent potential for lowering the engine combustor weight. This performance at low to moderate combustor mach numbers has stimulated interest in its ability to operate at higher combustion mach number, and for aerospace, this implies potentially higher flight mach numbers. To this end, a lobed diffuser-mixer that enhances the fuel-air mixing in the TVC combustor core was designed and evaluated, with special attention paid to the potential shock system entering the combustor core. For the present investigation, the lobed diffuser-mixer combustor rig is in a full annular configuration featuring sixfold symmetry among the lobes, symmetry within each lobe, and plain parallel, symmetric incident flow. During hardware cold-flow testing, significant discrepancies were found between computed and measured values for the pitot-probe-averaged static pressure profiles at the lobe exit plane. Computational fluid dynamics (CFD) simulations were initiated to determine whether the static pressure probe was causing high local flow-field disturbances in the supersonic flow exiting the diffuser-mixer and whether shock wave impingement on the pitot probe tip, pressure ports, or surface was the cause of the discrepancies. Simulations were performed with and without the pitot probe present in the modeling. A comparison of static pressure profiles without the probe showed that static pressure was off by nearly a factor of 2 over much of the radial profile, even when taking into account potential axial displacement of the probe by up to 0.25 in. (0.64 cm). Including the pitot probe in the CFD modeling and data interpretation lead to good agreement between measurement and prediction. Graphical inspection of the results showed that the shock waves impinging on the probe surface were highly nonuniform, with static pressure varying circumferentially among the pressure ports by over 10 percent in some cases. As part of the measurement methodology, such measurements should be routinely supplemented with CFD analyses that include the pitot probe as part of the flow-path geometry.

Simulation of mixing in the quick quench region of a rich burn-quick quench mix-lean burn combustor

NASA Technical Reports Server (NTRS)

Shih, Tom I.-P.; Nguyen, H. Lee; Howe, Gregory W.; Li, Z.

1991-01-01

A computer program was developed to study the mixing process in the quick quench region of a rich burn-quick quench mix-lean burn combustor. The computer program developed was based on the density-weighted, ensemble-averaged conservation equations of mass, momentum (full compressible Navier-Stokes), total energy, and species, closed by a k-epsilon turbulence model with wall functions. The combustion process was modeled by a two-step global reaction mechanism, and NO(x) formation was modeled by the Zeldovich mechanism. The formulation employed in the computer program and the essence of the numerical method of solution are described. Some results obtained for nonreacting and reacting flows with different main-flow to dilution-jet momentum flux ratios are also presented.

A Study of Pollutant Formation from the Lean Premixed Combustion of Gaseous Fuel Alternatives to Natural Gas

NASA Astrophysics Data System (ADS)

Fackler, Keith Boyd, Jr.

The goal of this research is to identify how nitrogen oxide (NO x) emissions and flame stability (blowout) are impacted by the use of fuels that are alternatives to typical pipeline natural gas. The research focuses on lean, premixed combustors that are typically used in state-of-the-art natural gas fueled systems. An idealized laboratory lean premixed combustor, specifically the jet-stirred reactor, is used for experimental data. A series of models, including those featuring detailed fluid dynamics and those focusing on detailed chemistry, are used to interpret the data and understand the underlying chemical kinetic reasons for differences in emissions between the various fuel blends. An ultimate goal is to use these data and interpretive tools to develop a way to predict the emission and stability impacts of changing fuels within practical combustors. All experimental results are obtained from a high intensity, single-jet stirred reactor (JSR). Five fuel categories are studied: (1) pure H 2, (2) process and refinery gas, including combinations of H2, CH4, C2H6, and C3H8, (3) oxygen blown gasified coal/petcoke composed of H2, CO, and CO2, (4) landfill and digester gas composed of CH4, CO2, and N2, and (5) liquified natural gas (LNG)/shale/associated gases composed of CH4, C2H6, and C3 H8. NOx measurements are taken at a nominal combustion temperature of 1800 K, atmospheric pressure, and a reactor residence time of 3 ms. This is done to focus the results on differences caused by fuel chemistry by comparing all fuels at a common temperature, pressure, and residence time. This is one of the few studies in the literature that attempts to remove these effects when studying fuels varying in composition. Additionally, the effects of changing temperature and residence time are investigated for selected fuels. At the nominal temperature and residence time, the experimental and modeling results show the following trends for NOx emissions as a function of fuel type: 1.) NOx emissions decrease with increasing H2 fuel fraction for combustion of CH4/H2 blends. This appears to be caused by a reduction in the amount of NO made by the prompt pathway involving the reaction of N2 with hydrocarbon radicals as the CH4 is replaced by H2. 2.) For category 2 (the process and refinery blend) and category 5 (the LNG, shale, and associated gases), NOx emissions increase with the addition of C2 and C3 hydrocarbons. This could be due to an increased production of free radicals resulting from increasing CO production when higher molecular weight hydrocarbons are broken down. 3.) For category 3 (the O2 blown gasified coal/petcoke), NOx emissions increase with increasing CO fuel fraction. The reason for this is attributed to CO producing more radicals per unit heat release than H2. When CO replaces H2, an increase in NOx emissions is seen due to an increase in the productivity of the N2O, NNH, and Zeldovich pathways. 4.) For category 4 (the landfill gas) the addition of diluents such as CO2 and N2 at constant air flow produces more NOx per kg of CH4 consumed, and N2 is more effective than CO 2 in increasing the NOx emission index. The increase in emission index appears to be due to an enhancement of the prompt NOx pathway as the diluents are added and the mixture moves towards stoichiometric. In addition, the presence of CO2 as a diluent catalyzes the loss of flame radicals, leading to less NOx formation than when an equivalent amount of N2 is used as a diluent. For a selected set of fuels, detailed spacial reactor probing is carried out. At the nominal temperature and residence time, the experimental results show the following trends for flame structure as a function of fuel type: 1.) Pure H2 is far more reactive in comparison to CH4 and all other pure alkane fuels. This results in relatively flat NO x and temperature profiles; whereas, the alkane fuels drop in both temperature and NOx production in the jet, where more fresh reactor feed gases are present. 2.) For category 2 (the Process and Refinery blends), H 2 addition increases reactivity in the jet while decreasing overall NOx emissions. The increased reactivity is especially evident in the CO profiles where the fuels blended with C2H6 and H2 have CO peaks on jet centerline and CO emissions for pure CH 4 peaks slightly off centerline. 3.) For category 3 (the O2 blown gasified coal/petcoke), the temperature profiles for the gasification blend and pure H2 are nearly identical, which is likely due to the high reactivity of H2 dominating the relatively low reactivity of CO. Despite a small temperature difference, the addition of CO causes an increase in NOx production. 4.) For category 4 (the landfill gas), the temperature profiles are virtually indistinguishable. However, the addition of diluent decreases reactivity and spreads out the reaction zone with the CO concentration peaking at 2 mm off of centerline instead of 1 mm. Diluent addition increases NOx production in comparison to pure CH4 for reasons explained above. 5.) For category 5 (the LNG, shale, and associated gases), the temperature profiles are all very similar. The increased reactivity of C2H6 is evident from looking at the CO profiles. Increased C2H6 promotes CO production on jet centerline which is indicative of the hydrocarbon material breaking down earlier in the jet. At temperatures and residence times other than the nominal conditions, the experimental results show the following trends: 1.) The NOx emissions from LPM combustion of pure CH4, H2, C 2H6, and C3H8 are shown to vary linearly with residence time and in an Arrhenius fashion with temperature. This occurs because (1) more reaction time leads to more NOx formation, and (2) NOx formation is a strong, non-linear function of temperature. 2.) The addition of both H2 and C2H6 to a LPM CH4 flame is effective at extending its lean blowout limit. The results of both two and three dimensional CFD simulations are presented to illustrate the general flow, temperature, and species structure within the reactor. Since the two dimensional model is far more computationally efficient, it is employed to study various fuel mixtures with more sophisticated chemical mechanisms. The CFD results from the LPM combustion of H2, H2/CO, and CH4 with NOx formation are presented. A three dimensional CFD simulation is run for LPM CH4 combustion that uses a global CH4 oxidation mechanism. While this model does not predict intermediate radicals and NOx, the CO contours and flow field can be used as guidelines to develop a chemical reactor network (CRN), which can incorporate detailed chemistry. In addition, this model runs quickly enough that it is a good way to initialize the temperature and flow field for simulations that do incorporate more complex chemistry. The two dimensional model is used to illustrate the difference in combustion behavior between the various fuels tested. In particular, it illustrates the geometric locations of the super-equilibrium radical fields and shows where and through which pathways NOx is formed. The pathway breakdowns show good agreement with the CRN modeling results. The main goal of the CFD modeling is to use the results of each model to develop Chemical Reactor Networks, CRNs, that are customized for a particular burner. The CRN can then be used to estimate the impacts due to fuel variation.

Pollutant Emissions and Lean Blowoff Limits of Fuel Flexible Burners Operating on Gaseous Renewable and Fossil Fuels

NASA Astrophysics Data System (ADS)

Colorado, Andres

This study provides an experimental and numerical examination of pollutant emissions and stability of gaseous fueled reactions stabilized with two premixed-fuel-flexible and ultra-low NOx burner technologies. Both burners feature lean combustion technology to control the formation of nitrogen oxides (NOx). The first fuel--flexible burner is the low-swirl burner (LSB), which features aerodynamic stabilization of the reactions with a divergent flow-field; the second burner is the surface stabilized combustion burner (SSCB), which features the stabilization of the reactions on surface patterns. For combustion applications the most commonly studied species are: NOx, carbon monoxide (CO), and unburned hydrocarbons (UHC). However these are not the only pollutants emitted when burning fossil fuels; other species such as nitrous oxide (N2O), ammonia (NH3) and formaldehyde (CH2O) can be directly emitted from the oxidation reactions. Yet the conditions that favor the emission of these pollutants are not completely understood and require further insight. The results of this dissertation close the gap existing regarding the relations between emission of pollutants species and stability when burning variable gaseous fuels. The results of this study are applicable to current issues such as: 1. Current combustion systems operating at low temperatures to control formation of NOx. 2. Increased use of alternative fuels such as hydrogen, synthetic gas and biogas. 3. Increasing recognition of the need/desire to operate combustion systems in a transient manner to follow load and to offset the intermittency of renewable power. 4. The recent advances in measurement methods allow us to quantify other pollutants, such as N 2O, NH3 and CH2O. Hence in this study, these pollutant species are assessed when burning natural gas (NG) and its binary mixtures with other gaseous fuels such as hydrogen (H2), carbon dioxide (CO2), ethane (C 2H6) and propane (C3H8) at variable operation modes including: ignition; lean blowoff; and variable air to fuel ratio. Some remarkable results of this dissertation include: • At a fixed fire rate (117kW) the addition of hydrogen to NG raises the emission of NO x for the reactions stabilized with the LSB. Under the same conditions, the addition of H2 to NG will reduce the emission levels of the reactions stabilized with the SSCB. • It was found experimentally that nitrous oxide (N2O) is emitted during ignition and blowoff events. • Ammonia (NH3) is also emitted during ignition and blowoff events. • It was found experimentally that at high concentrations of hydrogen in NG (H2>70%), reactions aerodynamically stabilized with the LSB will emit significant amounts of N2O.

Water Injected Turbomachinery

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Shouse, D. T.; Roquemore, W. M.

2005-01-01

From antiquity, water has been a source of cooling, lubrication, and power for energy transfer devices. More recent applications in gas turbines demonstrate an added facet, emissions control. Fogging gas turbine inlets or direct injection of water into gas turbine combustors, decreases NOx and increases power. Herein we demonstrate that injection of water into the air upstream of the combustor reduces NOx by factors up to three in a natural gas fueled Trapped Vortex Combustor (TVC) and up to two in a liquid JP-8 fueled (TVC) for a range in water/fuel and fuel/air ratios.

NOx Emissions Characteristics and Correlation Equations of Two P and W's Axially Staged Sector Combustors Developed Under NASA Environmentally Responsible Aviation (ERA) Project

NASA Technical Reports Server (NTRS)

He, Zhuohui J.

2017-01-01

Two P&W (Pratt & Whitney)'s axially staged sector combustors have been developed under NASA's Environmentally Responsible Aviation (ERA) project. One combustor was developed under ERA Phase I, and the other was developed under ERA Phase II. Nitrogen oxides (NOx) emissions characteristics and correlation equations for these two sector combustors are reported in this article. The Phase I design was to optimize the NOx emissions reduction potential, while the Phase II design was more practical and robust. Multiple injection points and fuel staging strategies are used in the combustor design. Pilot-stage injectors are located on the front dome plate of the combustor, and main-stage injectors are positioned on the top and bottom (Phase I) or on the top only (Phase II) of the combustor liners downstream. Low power configuration uses only pilot-stage injectors. Main-stage injectors are added to high power configuration to help distribute fuel more evenly and achieve lean burn throughout the combustor yielding very low NOx emissions. The ICAO (International Civil Aviation Organization) landing-takeoff NOx emissions are verified to be 88 percent (Phase I) and 76 percent (Phase II) under the ICAO CAEP/6 (Committee on Aviation Environmental Protection 6th Meeting) standard, exceeding the ERA project goal of 75 percent reduction, and the combustors proved to have stable combustion with room to maneuver on fuel flow splits for operability.

40 CFR Table 1 to Subpart Jjjj of... - NOX, CO, and VOC Emission Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Stationary Non-Emergency SI Engines â¥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI Landfill... Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI...-Emergency SI Natural Gas b and Non-Emergency SI Lean Burn LPG b 100≤HP HP 25 HP Table 1 to Subpart JJJJ of...

HSCT Sector Combustor Hardware Modifications for Improved Combustor Design

NASA Technical Reports Server (NTRS)

Greenfield, Stuart C.; Heberling, Paul V.; Moertle, George E.

2005-01-01

An alternative to the stepped-dome design for the lean premixed prevaporized (LPP) combustor has been developed. The new design uses the same premixer types as the stepped-dome design: integrated mixer flameholder (IMFH) tubes and a cyclone swirler pilot. The IMFH fuel system has been taken to a new level of development. Although the IMFH fuel system design developed in this Task is not intended to be engine-like hardware, it does have certain characteristics of engine hardware, including separate fuel circuits for each of the fuel stages. The four main stage fuel circuits are integrated into a single system which can be withdrawn from the combustor as a unit. Additionally, two new types of liner cooling have been designed. The resulting lean blowout data was found to correlate well with the Lefebvre parameter. As expected, CO and unburned hydrocarbons emissions were shown to have an approximately linear relationship, even though some scatter was present in the data, and the CO versus flame temperature data showed the typical cupped shape. Finally, the NOx emissions data was shown to agree well with a previously developed correlation based on emissions data from Configuration 3 tests performed at GEAE. The design variations of the cyclone swirler pilot that were investigated in this study did not significantly change the NOx emissions from the baseline design (GEAE Configuration 3) at supersonic cruise conditions.

Reduction of nitric oxide and DNA/RNA oxidation products are associated with active disease in systemic lupus erythematosus patients.

PubMed

Iriyoda, T M V; Stadtlober, N; Lozovoy, M A B; Delongui, F; Costa, N T; Reiche, E M V; Dichi, I; Simão, A N C

2017-09-01

The aims of the present study were to evaluate biomarkers of oxidative and nitrosative stress in systemic lupus erythematosus (SLE) patients, in particular products of DNA/RNA oxidative damage and their correlation with disease activity. This study included 188 controls and 203 patients; 153 with inactive SLE (SLEDAI < 6) and 50 with active SLE (SLEDAI ≥ 6) without renal impairment. Oxidative stress was assessed by tert-butyl hydroperoxide-initiated by chemiluminescence, advanced oxidation protein products (AOPP), total radical-trapping antioxidant parameter (TRAP), nitric oxide metabolites (NOx), and DNA/RNA oxidation products. Patients with SLE showed increased oxidative stress, as demonstrated by the augmentation of lipid hydroperoxides ( p < 0.0001) and AOPP ( p < 0.001) and reduced total antioxidant capacity ( p < 0.0001), without differences between patients with active disease and in remission. NOx levels and DNA/RNA oxidation products were inversely and independently associated with disease activity ( p < 0.0001 and p = 0.021, respectively), regardless of BMI and prednisone use. The linear regression analysis showed that about 5% of the SLEDAI score can be explained by the levels of DNA/RNA oxidation products ( r 2 :0.051; p = 0.002) and about 9% of this score by the levels of NOx ( r 2 :0.091; p < 0.0001). This study provides evidence for an inverse association between serum NOx levels and DNA/RNA oxidation products and SLE disease activity, suggesting that oxidative/nitrosative stress markers may be useful in evaluating SLE disease activity and progression of the disease.

Advanced Light-Duty SI Engine Fuels Research: Multiple Optical Diagnostics of Well-mixed and Stratified Operation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sjoberg, Carl Magnus Goran; Vuilleumier, David

Ever tighter fuel economy standards and concerns about energy security motivate efforts to improve engine efficiency and to develop alternative fuels. This project contributes to the science base needed by industry to develop highly efficient direct injection spark ignition (DISI) engines that also beneficially exploit the different properties of alternative fuels. Here, the emphasis is on lean operation, which can provide higher efficiencies than traditional non-dilute stoichiometric operation. Since lean operation can lead to issues with ignition stability, slow flame propagation and low combustion efficiency, the focus is on techniques that can overcome these challenges. Specifically, fuel stratification is usedmore » to ensure ignition and completeness of combustion but this technique has soot and NOx emissions challenges. For ultra-lean well-mixed operation, turbulent deflagration can be combined with controlled end-gas autoignition to render mixed-mode combustion for sufficiently fast heat release. However, such mixed-mode combustion requires very stable inflammation, motivating studies on the effects of near-spark flow and turbulence, and the use of small amounts of fuel stratification near the spark plug.« less

Reduction of gaseous pollutant emissions from gas turbine combustors using hydrogen-enriched jet fuel

NASA Technical Reports Server (NTRS)

Clayton, R. M.

1976-01-01

Recent progress in an evaluation of the applicability of the hydrogen enrichment concept to achieve ultralow gaseous pollutant emission from gas turbine combustion systems is described. The target emission indexes for the program are 1.0 for oxides of nitrogen and carbon monoxide, and 0.5 for unburned hydrocarbons. The basic concept utilizes premixed molecular hydrogen, conventional jet fuel, and air to depress the lean flammability limit of the mixed fuel. This is shown to permit very lean combustion with its low NOx production while simulataneously providing an increased flame stability margin with which to maintain low CO and HC emission. Experimental emission characteristics and selected analytical results are presented for a cylindrical research combustor designed for operation with inlet-air state conditions typical for a 30:1 compression ratio, high bypass ratio, turbofan commercial engine.

Sulfur oxide adsorbents and emissions control

DOEpatents

Li, Liyu [Richland, WA; King, David L [Richland, WA

2006-12-26

High capacity sulfur oxide absorbents utilizing manganese-based octahedral molecular sieve (Mn--OMS) materials are disclosed. An emissions reduction system for a combustion exhaust includes a scrubber 24 containing these high capacity sulfur oxide absorbents located upstream from a NOX filter 26 or particulate trap.

Effects of Sulfation Level on the Desulfation Behavior of Presulfated Pt-BaO/Al2O3 Lean

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, D.; Szanyi, J; Kwak, J

2009-01-01

Desulfation by hydrogen of presulfated Pt (2 wt %)-BaO(20 wt %)/Al2O3 with various sulfur loading (S/Ba = 0.12, 0.31, and 0.62) were investigated by combining H2 temperature programmed reaction (TPRX), X-ray photoelectron spectroscopy (XPS), in situ sulfur K-edge X-ray absorption near-edge spectroscopy (XANES), and synchrotron time-resolved X-ray diffraction (TR-XRD) techniques. We find that the amount of H2S desorbed during the desulfation in the H2 TPRX experiments is not proportional to the amount of initial sulfur loading. The results of both in situ sulfur K-edge XANES and TR-XRD show that at low sulfur loadings, sulfates were transformed to a BaS phasemore » and remained in the catalyst rather than being removed as H2S. On the other hand, when the deposited sulfur level exceeded a certain threshold (at least S/Ba = 0.31) sulfates were reduced to form H2S, and the relative amount of the residual sulfide species in the catalyst was much less than at low sulfur loading. Unlike samples with high sulfur loading (e.g., S/Ba = 0.62), H2O did not promote the desulfation for the sample with S/Ba of 0.12, implying that the formed BaS species originating from the reduction of sulfates at low sulfur loading are more stable to hydrolysis. The results of this combined spectroscopy investigation provide clear evidence to show that sulfates at low sulfur loadings are less likely to be removed as H2S and have a greater tendency to be transformed to BaS on the material, leading to the conclusion that desulfation behavior of Pt-BaO/Al2O3 lean NOx trap catalysts is markedly dependent on the sulfation levels.« less

Low NOx heavy fuel combustor concept program addendum: Low/mid heating value gaseous fuel evaluation

NASA Technical Reports Server (NTRS)

Novick, A. S.; Troth, D. L.

1982-01-01

The combustion performance of a rich/quench/lean (RQL) combustor was evaluated when operated on low and mid heating value gaseous fuels. Two synthesized fuels were prepared having lower heating values of 10.2 MJ/cu m. (274 Btu/scf) and 6.6 MJ/cu m (176 Btu/scf). These fuels were configured to be representative of actual fuels, being composed primarily of nitrogen, hydrogen, carbon monoxide, and carbon dioxide. A liquid fuel air assist fuel nozzle was modified to inject both of the gaseous fuels. The RQL combustor liner was not changed from the configuration used when the liquid fuels were tested. Both gaseous fuels were tested over a range of power levels from 50 percent load to maximum rated power of the DDN Model 570-K industrial gas turbine engine. Exhaust emissions were recorded for four power level at several rich zone equivalence ratios to determine NOx sensitivity to the rich zone operating point. For the mid Btu heating value gas, ammonia was added to the fuel to simulate a fuel bound nitrogen type gaseous fuel. Results at the testing showed that for the low heating value fuel NOx emissions were all below 20 ppmc and smoke was below a 10 smoke number. For the mid heating value fuel, NOx emissions were in the 50 to 70 ppmc range with the smoke below a 10 smoke number.

Regeneration and sulfur poisoning behavior of In/H-BEA catalyst for NOx reduction by CH4

NASA Astrophysics Data System (ADS)

Pan, Hua; Jian, Yanfei; Yu, Yanke; He, Chi; Shen, Zhenxing; Liu, Hongxia

2017-04-01

Sulfur poisoning and regeneration behavior of In/H-BEA catalyst were carried out in NOx reduction by CH4. In/H-BEA catalyst exhibited a poor resistance to sulfur dioxide after addition of 200 ppm SO2 and 10 vol.% H2O into NO reduction with CH4 at 450 °C for 45 h. Sulfur poisoning of In/H-BEA was attributed to the inhibition of NOx adsorption on Brønsted acid sites, suppression of reaction intermediates generation on the active sites, and the formation of surface sulfate species. The formation of surface sulfate reduced the availability of surface active sites, blocked the pore structure and decreased the surface area of catalyst. These changes in chemical and textural properties resulted in a severe loss in the activity of sulfated In/H-BEA catalyst for NO reduction with CH4. H2 reduction is a promising technology for regeneration of In/H-BEA deactivated by SO2 for removing NOx from lean-burn and diesel exhausts. Indium sulfate could be reduced by H2 to InO+ with In2O3 and In(OH)2+ as the intermediates. The optimal parameters of H2 reduction was regeneration temperature of 400 °C and regeneration time of 60 min which completely recovered the catalytic activity of In/H-BEA.

Catalysts, systems and methods to reduce NOX in an exhaust gas stream

DOEpatents

Castellano, Christopher R.; Moini, Ahmad; Koermer, Gerald S.; Furbeck, Howard

2010-07-20

Catalysts, systems and methods are described to reduce NO.sub.x emissions of an internal combustion engine. In one embodiment, an emissions treatment system for an exhaust stream is provided having an SCR catalyst comprising silver tungstate on an alumina support. The emissions treatment system may be used for the treatment of exhaust streams from diesel engines and lean burn gasoline engines. An emissions treatment system may further comprise an injection device operative to dispense a hydrocarbon reducing agent upstream of the catalyst.

Advanced Catalysis Technologies: Lanthanum Cerium Manganese Hexaaluminate Combustion Catalysts for Flat Plate Reactor for Compact Steam Reformers

DTIC Science & Technology

2008-12-01

to decompose the urea into carbon dioxide and ammonia. This increased the pH and caused sol condensation. The mixture was calcined in air at 550°C...propane to carbon dioxide and water. Its high manganese content provides a higher intrinsic activity than the other catalysts and thus the lowest...lean natural gas turbines in order to reduce NOx emissions to reforming catalyst to convert diesel and kerosene to hydrogen rich gases. Unlike

40 CFR Table 1 to Subpart Jjjj of... - NOX, CO, and VOC Emission Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Stationary Non-Emergency SI Engines â¥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI Landfill... Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI...-Emergency SI Natural Gas b and Non-Emergency SI Lean Burn LPG b 100≤HP<500 7/1/2008 2.0 4.0 1.0 160 540 86 1...

40 CFR Table 1 to Subpart Jjjj of... - NOX, CO, and VOC Emission Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Stationary Non-Emergency SI Engines â¥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI Landfill... Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI...-Emergency SI Natural Gas b and Non-Emergency SI Lean Burn LPG b 100≤HP<500 7/1/2008 2.0 4.0 1.0 160 540 86 1...

40 CFR Table 1 to Subpart Jjjj of... - NOX, CO, and VOC Emission Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Stationary Non-Emergency SI Engines â¥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI Landfill... Standards for Stationary Non-Emergency SI Engines ≥100 HP (Except Gasoline and Rich Burn LPG), Stationary SI...-Emergency SI Natural Gas b and Non-Emergency SI Lean Burn LPG b 100≤HP<500 7/1/2008 2.0 4.0 1.0 160 540 86 1...

Evaluation of Exhaust Emissions from Three Diesel-Hybrid Cars and Simulation of After-Treatment Systems for Ultralow Real-World NOx Emissions.

PubMed

Franco, Vicente; Zacharopoulou, Theodora; Hammer, Jan; Schmidt, Helge; Mock, Peter; Weiss, Martin; Samaras, Zissis

2016-12-06

Hybridization offers great potential for decreasing pollutant and carbon dioxide emissions of diesel cars. However, an assessment of the real-world emissions performance of modern diesel hybrids is missing. Here, we test three diesel-hybrid cars on the road and benchmark our findings with two cars against tests on the chassis dynamometer and model simulations. The pollutant emissions of the two cars tested on the chassis dynamometer were in compliance with the relevant Euro standards over the New European Driving Cycle and Worldwide harmonized Light vehicles Test Procedure. On the road, all three diesel-hybrids exceeded the regulatory NO x limits (average exceedance for all trips: +150% for the Volvo, +510% for the Peugeot, and +550% for the Mercedes-Benz) and also showed elevated on-road CO 2 emissions (average exceedance of certification values: +178, +77, and +52%, respectively). These findings point to a wide discrepancy between certified and on-road CO 2 and suggest that hybridization alone is insufficient to achieve low-NO x emissions of diesel powertrains. Instead, our simulation suggests that properly calibrated selective catalytic reduction filter and lean-NO x trap after-treatment technologies can reduce the on-road NO x emissions to 0.023 and 0.068 g/km on average, respectively, well below the Euro 6 limit (0.080 g/km).

Effect of Air Temperature and Relative Humidity at Various Fuel-Air Ratios on Exhaust Emissions on a Per-Mode Basis of an AVCO Lycoming 0-320 Diad Light Aircraft Engine: Volume 1: Results and Plotted Data

NASA Technical Reports Server (NTRS)

Skorobatckyi, M.; Cosgrove, D. V.; Meng, P. R.; Kempe, E. E., Jr.

1978-01-01

A carbureted four cylinder air cooled 0-320 DIAD Lycoming aircraft engine was tested to establish the effects of air temperature and humidity at various fuel-air ratios on the exhaust emissions on a per-mode basis. The test conditions include carburetor lean out at air temperatures of 50, 59, 80, and 100 F at relative humidities of 0, 30, 60, and 80 percent. Temperature humidity effects at the higher values of air temperature and relative humidity tested indicated that the HC and CO emissions increased significantly, while the NOx emissions decreased. Even at a fixed fuel air ratio, the HC emissions increase and the NOx emissions decrease at the higher values of air temperature and humidity.

Predicted exhaust emissions from a methanol and jet fueled gas turbine combustor

NASA Technical Reports Server (NTRS)

Adelman, H. G.; Browning, L. H.; Pefley, R. K.

1975-01-01

A computer model of a gas turbine combustor has been used to predict the kinetic combustion and pollutant formation processes for methanol and simulated jet fuel. Use of the kinetic reaction mechanisms has also allowed a study of ignition delay and flammability limit of these two fuels. The NOX emissions for methanol were predicted to be from 69 to 92% lower than those for jet fuel at the same equivalence ratio which is in agreement with experimentally observed results. The high heat of vaporization of methanol lowers both the combustor inlet mixture temperatures and the final combustion temperatures. The lower combustion temperatures lead to low NOX emissions while the lower inlet mixture temperatures increase methanol's ignition delay. This increase in ignition delay dictates the lean flammability limit of methanol to be 0.8, while jet fuel is shown to combust at 0.4.

Effect of air temperature and relative humidity at various fuel-air ratios on exhaust emissions on a per-mode basis of an Avco Lycoming 0-320 DIAD light aircraft engine. Volume 2: Individual data points

NASA Technical Reports Server (NTRS)

Skorobatckyi, M.; Cosgrove, D. V.; Meng, P. R.; Kempke, E. R.

1976-01-01

A carbureted four cylinder air cooled 0-320 DIAD Lycoming aircraft engine was tested to establish the effects of air temperature and humidity at various fuel-air ratios on the exhaust emissions on a per-mode basis. The test conditions included carburetor lean-out at air temperatures of 50, 59, 80, and 100 F at relative humidities of 0, 30, 60, and 80 percent. Temperature-humidity effects at the higher values of air temperature and relative humidity tested indicated that the HC and CO emissions increased significantly, while the NOx emissions decreased. Even at a fixed fuel-air ratio, the HC emissions increase and the NOx emissions decrease at the higher values of air temperature and humidity. Volume II contains the data taken at each of the individual test points.

Two-stage combustion for reducing pollutant emissions from gas turbine combustors

NASA Technical Reports Server (NTRS)

Clayton, R. M.; Lewis, D. H.

1981-01-01

Combustion and emission results are presented for a premix combustor fueled with admixtures of JP5 with neat H2 and of JP5 with simulated partial-oxidation product gas. The combustor was operated with inlet-air state conditions typical of cruise power for high performance aviation engines. Ultralow NOx, CO and HC emissions and extended lean burning limits were achieved simultaneously. Laboratory scale studies of the non-catalyzed rich-burning characteristics of several paraffin-series hydrocarbon fuels and of JP5 showed sooting limits at equivalence ratios of about 2.0 and that in order to achieve very rich sootless burning it is necessary to premix the reactants thoroughly and to use high levels of air preheat. The application of two-stage combustion for the reduction of fuel NOx was reviewed. An experimental combustor designed and constructed for two-stage combustion experiments is described.

Plasma-assisted catalytic storage reduction system

DOEpatents

Penetrante, Bernardino M.; Vogtlin, George E.; Merritt, Bernard T.; Brusasco, Raymond M.

2000-01-01

A two-stage method for NO.sub.x reduction in an oxygen-rich engine exhaust comprises a plasma oxidative stage and a storage reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons. The second stage employs a lean NO.sub.x trap to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage with a plasma, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber in which a non-thermal plasma converts NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons, such as propene. A flow of such hydrocarbons (C.sub.x H.sub.y) is input from usually a second pipe into at least a portion of the first chamber. The NO.sub.2 from the plasma treatment proceeds to a storage reduction catalyst (lean NO.sub.x trap) that converts NO.sub.2 to N.sub.2, CO.sub.2, and H.sub.2 O, and includes a nitrate-forming catalytic site. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the lean-NO.sub.x trap catalyst. The method allows for enhanced NO.sub.x reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.

Plasma-assisted catalytic storage reduction system

DOEpatents

Penetrante, Bernardino M.; Vogtlin, George E.; Merritt, Bernard T.; Brusasco, Raymond M.

2002-01-01

A two-stage method for NO.sub.x reduction in an oxygen-rich engine exhaust comprises a plasma oxidative stage and a storage reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons. The second stage employs a lean NO.sub.x trap to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O. By preconverting NO to NO.sub.2 in the first stage with a plasma, the efficiency of the second stage for NO.sub.x reduction is enhanced. For example, an internal combustion engine exhaust is connected by a pipe to a first chamber in which a non-thermal plasma converts NO to NO.sub.2 in the presence of O.sub.2 and hydrocarbons, such as propene. A flow of such hydrocarbons (C.sub.x H.sub.y) is input from usually a second pipe into at least a portion of the first chamber. The NO.sub.2 from the plasma treatment proceeds to a storage reduction catalyst (lean NO.sub.x trap) that converts NO.sub.2 to N.sub.2, CO.sub.2, and H.sub.2 O, and includes a nitrate-forming catalytic site. The hydrocarbons and NO.sub.x are simultaneously reduced while passing through the lean-NO.sub.x trap catalyst. The method allows for enhanced NO.sub.x reduction in vehicular engine exhausts, particularly those having relatively high sulfur contents.

Critical research and advanced technology (CRT) support project

NASA Technical Reports Server (NTRS)

Furman, E. R.; Anderson, D. N.; Hodge, P. E.; Lowell, C. E.; Nainiger, J. J.; Schultz, D. F.

1983-01-01

A critical technology base for utility and industrial gas turbines by planning the use of coal-derived fuels was studied. Development tasks were included in the following areas: (1) Combustion - investigate the combustion of coal-derived fuels and methods to minimize the conversion of fuel-bound nitrogen to NOx; (2) materials - understand and minimize hot corrosion; (3) system studies - integrate and focus the technological efforts. A literature survey of coal-derived fuels was completed and a NOx emissions model was developed. Flametube tests of a two-stage (rich-lean) combustor defined optimum equivalence ratios for minimizing NOx emissions. Sector combustor tests demonstrated variable air control to optimize equivalence ratios over a wide load range and steam cooling of the primary zone liner. The catalytic combustion of coal-derived fuels was demonstrated. The combustion of coal-derived gases is very promising. A hot-corrosion life prediction model was formulated and verified with laboratory testing of doped fuels. Fuel additives to control sulfur corrosion were studied. The intermittent application of barium proved effective. Advanced thermal barrier coatings were developed and tested. Coating failure modes were identified and new material formulations and fabrication parameters were specified. System studies in support of the thermal barrier coating development were accomplished.

Gas turbine topping combustor

DOEpatents

Beer, Janos; Dowdy, Thomas E.; Bachovchin, Dennis M.

1997-01-01

A combustor for burning a mixture of fuel and air in a rich combustion zone, in which the fuel bound nitrogen in converted to molecular nitrogen. The fuel rich combustion is followed by lean combustion. The products of combustion from the lean combustion are rapidly quenched so as to convert the fuel bound nitrogen to molecular nitrogen without forming NOx. The combustor has an air radial swirler that directs the air radially inward while swirling it in the circumferential direction and a radial fuel swirler that directs the fuel radially outward while swirling it in the same circumferential direction, thereby promoting vigorous mixing of the fuel and air. The air inlet has a variable flow area that is responsive to variations in the heating value of the fuel, which may be a coal-derived fuel gas. A diverging passage in the combustor in front of a bluff body causes the fuel/air mixture to recirculate with the rich combustion zone.

Simultaneous NOx and Particulate Matter Removal from Diesel Exhaust by Hierarchical Fe-Doped Ce–Zr Oxide

PubMed Central

2017-01-01

Particulate matter and NOx emissions from diesel exhaust remains one of the most pressing environmental problems. We explore the use of hierarchically ordered mixed Fe–Ce–Zr oxides for the simultaneous capture and oxidation of soot and reduction of NOx by ammonia in a single step. The optimized material can effectively trap the model soot particles in its open macroporous structure and oxidize the soot below 400 °C while completely removing NO in the 285–420 °C range. Surface characterization and DFT calculations emphasize the defective nature of Fe-doped ceria. The isolated Fe ions and associated oxygen vacancies catalyze facile NO reduction to N2. A mechanism for the reduction of NO with NH3 on Fe-doped ceria is proposed involving adsorbed O2. Such adsorbed O2 species will also contribute to the oxidation of soot. PMID:28603656

The Effects of Air Preheat and Number of Orifices on Flow and Emissions in an RQL Mixing Section

NASA Technical Reports Server (NTRS)

Holdeman, James D.; Chang, Clarence T.

2007-01-01

This study was motivated by a goal to understand the mixing and emissions in the rich-burn/quick-mix/lean-burn (RQL) combustor scheme that has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine combustors. The study reported in this paper was a reacting jet-in-crossflow experiment at atmospheric pressure in a cylindrical duct. The jets were injected from the perimeter of the duct through round-hole orifices into a fuel-rich mainstream flow. The number of orifices investigated in this study gave over- to optimum to underpenetrating jets at a jet-to-mainstream momentum-flux ratio of 57. The size of individual orifices was decreased as their number increased to maintain a constant total area. The jet-to-mainstream mass-flow ratio was held constant at 2.5. The experiments focused on the effects of the number of orifices and inlet air preheat and were conducted in a facility that provided the capability for independent variation of jet and main inlet air preheat temperature. The number of orifices was found to have a significant effect on mixing and the distributions of species, but very little effect on overall NOx emissions, suggesting that an aerodynamically optimum mixer may not minimize NOx emissions. Air preheat was found to have very little effect on mixing and the distributions of major species, but preheat did increase NOx emissions significantly. Although the air jets injected in the quick-mix section of a RQL combustor may comprise over 70% of the total air flow, the overall NOx emission levels were found to be more sensitive to mainstream air preheat than to jet stream air preheat.

Low Emissions RQL Flametube Combustor Component Test Results

NASA Technical Reports Server (NTRS)

Holdeman, James D.; Chang, Clarence T.

2001-01-01

This report describes and summarizes elements of the High Speed Research (HSR) Low Emissions Rich burn/Quick mix/Lean burn (RQL) flame tube combustor test program. This test program was performed at NASA Glenn Research Center circa 1992. The overall objective of this test program was to demonstrate and evaluate the capability of the RQL combustor concept for High Speed Civil Transport (HSCT) applications with the goal of achieving NOx emission index levels of 5 g/kg-fuel at representative HSCT supersonic cruise conditions. The specific objectives of the tests reported herein were to investigate component performance of the RQL combustor concept for use in the evolution of ultra-low NOx combustor design tools. Test results indicated that the RQL combustor emissions and performance at simulated supersonic cruise conditions were predominantly sensitive to the quick mixer subcomponent performance and not sensitive to fuel injector performance. Test results also indicated the mixing section configuration employing a single row of circular holes was the lowest NOx mixer tested probably due to the initial fast mixing characteristics of this mixing section. However, other quick mix orifice configurations such as the slanted slot mixer produced substantially lower levels of carbon monoxide emissions most likely due to the enhanced circumferential dispersion of the air addition. Test results also suggested that an optimum momentum-flux ratio exists for a given quick mix configuration. This would cause undesirable jet under- or over-penetration for test conditions with momentum-flux ratios below or above the optimum value. Tests conducted to assess the effect of quick mix flow area indicated that reduction in the quick mix flow area produced lower NOx emissions at reduced residence time, but this had no effect on NOx emissions measured at similar residence time for the configurations tested.

Mixing of Multiple Jets with a Confined Subsonic Crossflow: Part III--The Effects of Air Preheat and Number of Orifices on Flow and Emissions in an RQL Mixing Section

NASA Technical Reports Server (NTRS)

Holdemann, James D.; Chang, Clarence T.

2008-01-01

This study was motivated by a goal to understand the mixing and emissions in the Rich-burn/Quick-mix/Lean-burn (RQL) combustor scheme that has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine combustors. The study reported herein was a reacting jet-in-crossflow experiment at atmospheric pressure. The jets were injected from the perimeter of a cylindrical duct through round-hole orifices into a fuel-rich mainstream flow. The number of orifices investigated in this study gave over- to optimum to underpenetrating jets at a jet-to-mainstream momentum-flux ratio of J = 57. The size of individual orifices was decreased as the number of orifices increased to maintain a constant total area; the jet-to-mainstream mass-flow ratio was constant at MR = 2.5. The experiments focused on the effects of the number of orifices and inlet air preheat and were conducted in a facility that provided the capability for independent variation of jet and main inlet air preheat temperature. The number of orifices was found to have a significant effect on mixing and the distributions of species, but very little effect on overall NOx emissions, suggesting that an aerodynamically optimum mixer might not minimize NOx emissions. Air preheat was found to have very little effect on mixing and the distributions of major species, but preheating both main and jet air did increase NOx emissions significantly. Although the air jets injected in the quick-mix section of an RQL combustor may comprise over 70 percent of the total air flow, the overall NOx emission levels were found to be more sensitive to main stream air preheat than to jet stream air preheat.

Effects of Retrofitting Emission Control Systems on all In-Use Heavy Diesel Trucks

NASA Astrophysics Data System (ADS)

Millstein, D.; Harley, R. A.

2009-12-01

Diesel exhaust is now the largest source of nitrogen oxide (NOx) emissions nationally in the US, and contributes significantly to emissions of fine particulate black carbon (soot) as well. New national standards call for dramatically lower emissions of exhaust particulate matter (PM) and NOx from new diesel engines starting in 2007 and 2010, respectively. Unfortunately it will take decades for the cleaner new engines to replace those currently in service on existing heavy-duty trucks. The state of California recently adopted a rule to accelerate fleet turnover in the heavy-duty truck sector, requiring that all in-use trucks meet the new exhaust PM standards by 2014. This will entail retrofit of diesel particle filters or replacement for over a million existing diesel engines. Diesel particle filters can replace the muffler on existing trucks, and there is extensive experience with retrofit of this control equipment on public sector fleets such as diesel-powered transit buses. Nitrogen dioxide (NO2) is used as an oxidizing agent to remove carbon particles from the particle filter, to prevent it from becoming plugged. To create the needed NO2, NOx already present in engine exhaust as nitric oxide (NO) is deliberately oxidized to NO2 upstream of the particle filter using a platinum catalyst. The NO2/NOx ratio in exhaust emissions therefore increases to ~35% in comparison to much lower values (~5%) typical of older engines without particle filters. We evaluate the effects on air quality of increased use of diesel particle traps and NOx controls in southern California using the Community Multiscale Air Quality (CMAQ) model. Compared to a reference scenario without the retrofit program, we found black carbon concentrations decreased by ~20%, with small increases (4%) in ambient ozone concentrations. During summer, average NO2 concentrations decrease despite the increase in primary NO2 emissions - because total NOx emissions are reduced as part of a parallel but more gradual program to retrofit NOx control systems on in-use engines. During winter, NO2 concentrations increase by 1-2% at locations with high diesel truck traffic, and larger increases may occur if diesel trucks outfitted with particle traps do not meet the in-use NOx emission reduction requirements. Small changes to fine particulate nitrate are seen as well with increases over the Los Angeles area of 3 and 6% during the summer and fall, respectively. During the summer, but not the fall, downwind nitrate decreased by 2% east of Los Angeles near Riverside. Emissions reductions due to fleet turnover in the reference scenario (without retrofit) may be optimistic, and the air quality benefits of retrofits could therefore be understated, due to slow sales of new engines in recent years. In any case, significant changes in diesel engine emissions of NOx and PM are expected to occur over the next 5 years in California.

Lean Premixed Combustion Stabilized by Low Swirl a Promising Concept for Practical Applications

NASA Technical Reports Server (NTRS)

Cheng, R. K.

1999-01-01

Since its inception, the low-swirl burner (LSB) has shown to be a useful laboratory apparatus for fundamental studies of premixed turbulent flames. The LSB operates under wide ranges of equivalence ratios, flow rates, and turbulence intensities. Its flame is lifted and detached from the burner and allows easy access for laser diagnostics. The flame brush is axisymmetric and propagates normal to the incident reactants. Therefore, the LSB is well suited for investigating detailed flame structures and empirical coefficients such as flame speed, turbulence transport, and flame generated turbulence. Due to its capability to stabilize ultra-lean premixed turbulent flames (phi approx. = 0.55), the LSB has generated interest from the gas appliance industry for use as an economical low-NO(x) burner. Lean premixed combustion emits low levels of NO(x), due primarily to the low flame temperature. Therefore, it is a very effective NO(x) prevention method without involving selective catalytic reduction (SCR), fuel-air staging, or flue gas recirculation (FGR). En the gas turbine industry, substantial research efforts have already been undertaken and engines with lean premixed combustors are already in use. For commercial and residential applications, premixed pulsed combustors and premixed ceramic matrix burners are commercially available. These lean premixed combustion technologies, however, tend to be elaborate but have relatively limited operational flexibility, and higher capital, operating and maintenance costs. Consequently, these industries are continuing the development of lean premixed combustion technologies as well as exploring new concepts. This paper summarizes the research effects we have undertaken in the past few years to demonstrate the feasibility of applying the low-swirl flame stabilization method for a wide range of heating and power generation systems. The principle of flame stabilization by low-swirl is counter to the conventional high-swirl methods that rely on a recirculation zone to anchor the flame. In LSBS, flow recirculation is not promoted to allow the premixed turbulent flames to propagate freely. A LSB with an air-jet swirler is essentially an open tube with the swirler at its mid section. The small air-jets generate swirling motion only in the annular region and leaving the central core of the flow undisturbed, When this flow exits the burner tube, the angular momentum generates radial mean pressure gradient to diverge the non-swirling reactants stream. Consequently, the mean flow velocity decreases linearly. Propagating against this decelerating flow, the flame self-sustains at the position where the local flow velocity equals the flame speed, S(sub f). The LSB operates with a swirl number, S, between 0.02 to 0.1. This is much lower than the minimum S of 0.6 required for the high-swirl burners. We found that the swirl number needed for flame stabilization varies only slightly with fuel type, flow velocity, turbulent conditions and burner dimensions (i.e. throat diameter and swirl injection angle).

Exposure to Traffic-Related Air Pollution in Relation to Progression in Physical Disability among Older Adults

PubMed Central

Weuve, Jennifer; Kaufman, Joel D.; Szpiro, Adam A.; Curl, Cynthia; Puett, Robin C.; Beck, Todd; Evans, Denis A.; Mendes de Leon, Carlos F.

2016-01-01

Background: Physical disability is common though not inevitable in older age and has direct bearing on a person’s ability to perform activities essential for self-care and independent living. Air pollution appears to increase the risk of several chronic diseases that contribute to the progression of disability. Objective: We evaluated long-term exposure to traffic-related air pollution (TRAP) in relation to progression in physical disability. Methods: We conducted our investigation within the Chicago Health and Aging Project. We measured participants’ exposures to TRAP using two surrogates: residential proximity to major roads (1993 onwards) and ambient concentrations of oxides of nitrogen (NOX; 1999 onwards), predicted via a geographic information systems-based spatiotemporal smoothing model (cross-validation R2 = 0.87) that incorporated community-based monitoring and resolved intraurban exposure gradients at a spatial scale of tens of meters. Participants’ lower-extremity physical ability was assessed every 3 years (1993–2012) via tandem stand, chair stand, and timed walking speed. Results: In multivariable-adjusted analyses (n = 5,708), higher long-term NOX exposure was associated with significantly faster progression in disability. Compared with the 5-year decline in physical ability score among participants in the lowest quartile of NOX exposure, decline among those in the highest exposure quartile was 1.14 units greater (95% confidence interval [CI]: –1.86, –0.42), equivalent to 3 additional years of decline among those in the lowest exposure quartile. The association was linear across the continuum of NOX exposure: per 10-ppb increment in exposure, the 5-year decline in physical ability score was 0.87 unit greater (95% CI: –1.35, –0.39). Proximity to a major road was not associated with disability progression (n = 9,994). Conclusions: These data join a growing body of evidence suggesting that TRAP exposures may accelerate aging-related declines in health. Citation: Weuve J, Kaufman JD, Szpiro AA, Curl C, Puett RC, Beck T, Evans DA, Mendes de Leon CF. 2016. Exposure to traffic-related air pollution in relation to progression in physical disability among older adults. Environ Health Perspect 124:1000–1008; http://dx.doi.org/10.1289/ehp.1510089 PMID:27022889

National Combustion Code Used To Study the Hydrogen Injector Design for Gas Turbines

NASA Technical Reports Server (NTRS)

Iannetti, Anthony C.; Norris, Andrew T.; Shih, Tsan-Hsing

2005-01-01

Hydrogen, in the gas state, has been proposed to replace Jet-A (the fuel used for commercial jet engines) as a fuel for gas turbine combustion. For the combustion of hydrogen and oxygen only, water is the only product and the main greenhouse gas, carbon dioxide, is not produced. This is an obvious benefit of using hydrogen as a fuel. The situation is not as simple when air replaces oxygen in the combustion process. (Air is mainly a mixture of oxygen, nitrogen, and argon. Other components comprise a very small part of air and will not be mentioned.) At the high temperatures found in the combustion process, oxygen reacts with nitrogen, and this produces nitrogen oxide compounds, or NOx--the main component of atmospheric smog. The production of NOx depends mainly on two variables: the temperature at which combustion occurs, and the length of time that the products of combustion stay, or reside, in the combustor. Starting from a lean (excess air) air-to-fuel ratio, the goal of this research was to minimize hot zones caused by incomplete premixing and to keep the residence time short while producing a stable flame. The minimization of these two parameters will result in low- NOx hydrogen combustion.

A new unsteady mixing model to predict NO(x) production during rapid mixing in a dual-stage combustor

NASA Technical Reports Server (NTRS)

Menon, Suresh

1992-01-01

An advanced gas turbine engine to power supersonic transport aircraft is currently under study. In addition to high combustion efficiency requirements, environmental concerns have placed stringent restrictions on the pollutant emissions from these engines. A combustor design with the potential for minimizing pollutants such as NO(x) emissions is undergoing experimental evaluation. A major technical issue in the design of this combustor is how to rapidly mix the hot, fuel-rich primary zone product with the secondary diluent air to obtain a fuel-lean mixture for combustion in the second stage. Numerical predictions using steady-state methods cannot account for the unsteady phenomena in the mixing region. Therefore, to evaluate the effect of unsteady mixing and combustion processes, a novel unsteady mixing model is demonstrated here. This model has been used to study multispecies mixing as well as propane-air and hydrogen-air jet nonpremixed flames, and has been used to predict NO(x) production in the mixing region. Comparison with available experimental data show good agreement, thereby providing validation of the mixing model. With this demonstration, this mixing model is ready to be implemented in conjunction with steady-state prediction methods and provide an improved engineering design analysis tool.

DNS of turbulent premixed slot flames with mixture inhomogeneity: a study of NOx formation

NASA Astrophysics Data System (ADS)

Luca, Stefano; Attili, Antonio; Bisetti, Fabrizio

2016-11-01

A set of Direct Numerical Simulations of three-dimensional methane/air lean flames in a spatially developing turbulent slot burner are performed. The flames are in the thin-reaction zone regimes and the jet Reynolds number is 5600. This configuration is of interest since it displays turbulent production by mean shear as in real devices. The gas phase hydrodynamics are modeled with the reactive, unsteady Navier-Stokes equations in the low Mach number limit. Combustion is treated with finite-rate chemistry. The jet is characterized by a non-uniform equivalence ratio at the inlet and varying levels of incomplete premixing for the methane/air mixture are considered. The global equivalence ratio is 0.7 and temperature is 800 K. All simulations are performed at 4 atm. The instantaneous profiles of the mass fractions of methane and air at the inlet are sampled from a set of turbulent channel simulations that provide realistic, fully turbulent fields. The data are analyzed to study the influence of partial premixing on the flame structure. Particular focus is devoted to the assessment of heat release rate fluctuations and NOx formation. In particular, the effects of partial premixing on the production rates for the various pathways to NOx formation are investigated.

Plasma-assisted combustion in lean, high-pressure, preheated air-methane mixtures

NASA Astrophysics Data System (ADS)

Sommerer, Timothy; Herbon, John; Saddoughi, Seyed; Deminsky, Maxim; Potapkin, Boris

2013-09-01

We combine a simplified physical model with a detailed plasma-chemical reaction mechanism to analyze the use of plasmas to improve flame stability in a gas turbine used for electric power generation. For this application the combustion occurs in a lean mixture of air and methane at high pressure (18.6 atm) and at ``preheat'' temperature 700 K, and the flame zone is both recirculating and turbulent. The system is modeled as a sequence of reactors: a pulsed uniform plasma (Boltzmann), an afterglow region (plug-flow), a flame region (perfectly-stirred), and a downstream region (plug-flow). The plasma-chemical reaction mechanism includes electron-impact on the feedstock species, relaxation in the afterglow to neutral molecules and radicals, and methane combustion chemistry (GRI-Mech 3.0), with extensions to properly describe low-temperature combustion 700-1000 K [M Deminsky et al., Chem Phys 32, 1 (2013)]. We find that plasma treatment of the incoming air-fuel mixture can improve the stability of lean flames, expressed as a reduction in the adiabatic flame temperature at lean blow-out, but that the plasma also generates oxides of nitrogen at the preheat temperature through the reactions e + N2 --> N + N and N + O2 --> NO + O. We find that flame stability is improved with less undesirable NOx formation when the plasma reduced-electric-field E/ N is smaller. A portion of this work was supported by the US Dept of Energy under Award Number DE-FC26-08NT05868.

Comparing Spray Characteristics from Reynolds Averaged Navier-Stokes (RANS) National Combustion Code (NCC) Calculations Against Experimental Data for a Turbulent Reacting Flow

NASA Technical Reports Server (NTRS)

Iannetti, Anthony C.; Moder, Jeffery P.

2010-01-01

Developing physics-based tools to aid in reducing harmful combustion emissions, like Nitrogen Oxides (NOx), Carbon Monoxide (CO), Unburnt Hydrocarbons (UHC s), and Sulfur Dioxides (SOx), is an important goal of aeronautics research at NASA. As part of that effort, NASA Glenn Research Center is performing a detailed assessment and validation of an in-house combustion CFD code known as the National Combustion Code (NCC) for turbulent reacting flows. To assess the current capabilities of NCC for simulating turbulent reacting flows with liquid jet fuel injection, a set of Single Swirler Lean Direct Injection (LDI) experiments performed at the University of Cincinnati was chosen as an initial validation data set. This Jet-A/air combustion experiment operates at a lean equivalence ratio of 0.75 at atmospheric pressure and has a 4 percent static pressure drop across the swirler. Detailed comparisons of NCC predictions for gas temperature and gaseous emissions (CO and NOx) against this experiment are considered in a previous work. The current paper is focused on detailed comparisons of the spray characteristics (radial profiles of drop size distribution and at several radial rakes) from NCC simulations against the experimental data. Comparisons against experimental data show that the use of the correlation for primary spray break-up implemented by Raju in the NCC produces most realistic results, but this result needs to be improved. Given the single or ten step chemical kinetics models, use of a spray size correlation gives similar, acceptable results

Experimental and Computational Study of Trapped Vortex Combustor Sector Rig with Tri-pass Diffuser

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Shouse, D. T.; Roquemore, W. M.; Burrus, D. L.; Duncan, B. S.; Ryder, R. C.; Brankovic, A.; Liu, N.-S.; Gallagher, J. R.; Hendricks, J. A.

2001-01-01

The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL (Rich burn/Quick mix/Lean burn) modes of combustion. The present work describes the operational principles of the TVC, and provides detailed performance data on a configuration featuring a tri-pass diffusion system. Performance data include EINOx (NO(sub x) emission index) results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable in comparison to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.

Reformer assisted lean NO.sub.x catalyst aftertreatment system and method

DOEpatents

Kalyanaraman, Mohan [Media, PA; Park, Paul W [Peoria, IL; Ragle, Christie S [Havana, IL

2010-06-29

A method and apparatus for catalytically processing a gas stream passing therethrough to reduce the presence of NO.sub.x therein, wherein the apparatus includes a first catalyst composed of a silver-containing alumina that is adapted for catalytically processing the gas stream at a first temperature range, a second catalyst composed of a copper-containing zeolite located downstream from the first catalyst, wherein the second catalyst is adapted for catalytically processing the gas stream at a lower second temperature range relative to the first temperature range, a hydrocarbon compound for injection into the gas stream upstream of the first catalyst to provide a reductant, and a reformer for reforming a portion of the hydrocarbon compound into H.sub.2 and/or oxygenated hydrocarbon for injection into the gas stream upstream of the first catalyst. The second catalyst is adapted to facilitate the reaction of reducing NOx into N.sub.2, whereby the intermediates are produced via the first catalyst reacting with NOx and hydrocarbons.

Synthesis of Pt/K2CO3/MgAlOx–reduced graphene oxide hybrids as promising NOx storage–reduction catalysts with superior catalytic performance

PubMed Central

Mei, Xueyi; Yan, Qinghua; Lu, Peng; Wang, Junya; Cui, Yuhan; Nie, Yu; Umar, Ahmad; Wang, Qiang

2017-01-01

Pt/K2CO3/MgAlOx–reduced graphene oxide (Pt/K/MgAlOx–rGO) hybrids were synthesized, characterized and tested as a promising NOx storage and reduction (NSR) catalyst. Mg–Al layered double hydroxides (LDHs) were grown on rGO via in situ hydrothermal crystallization. The structure and morphology of samples were thoroughly characterized using various techniques. Isothermal NOx adsorption tests indicated that MgAlOx–rGO hybrid exhibited better NOx trapping performance than MgAlOx, from 0.44 to 0.61 mmol · g−1, which can be attributed to the enhanced particle dispersion and stabilization. In addition, a series of MgAlOx–rGO loaded with 2 wt% Pt and different loadings (5, 10, 15, and 20 wt%) of K2CO3 (denoted as Pt/K/MgAlOx–rGO) were obtained by sequential impregnation. The influence of 5% H2O on the NOx storage capacity of MgAlOx–rGO loaded with 2 wt% Pt and 10% K2CO3 (2Pt/10 K/MgAlOx–rGO) catalyst was also evaluated. In all, the 2Pt/10 K/MgAlOx–rGO catalyst not only exhibited high thermal stability and NOx storage capacity of 1.12 mmol · g−1, but also possessed excellent H2O resistance and lean–rich cycling performance, with an overall 78.4% of NOx removal. This work provided a new scheme for the preparation of highly dispersed MgAlOx–rGO hybrid based NSR catalysts. PMID:28205630

Multi-Point Combustion System: Final Report

NASA Technical Reports Server (NTRS)

Goeke, Jerry; Pack, Spencer; Zink, Gregory; Ryon, Jason

2014-01-01

A low-NOx emission combustor concept has been developed for NASA's Environmentally Responsible Aircraft (ERA) program to meet N+2 emissions goals for a 70,000 lb thrust engine application. These goals include 75 percent reduction of LTO NOx from CAEP6 standards without increasing CO, UHC, or smoke from that of current state of the art. An additional key factor in this work is to improve lean combustion stability over that of previous work performed on similar technology in the early 2000s. The purpose of this paper is to present the final report for the NASA contract. This work included the design, analysis, and test of a multi-point combustion system. All design work was based on the results of Computational Fluid Dynamics modeling with the end results tested on a medium pressure combustion rig at the UC and a medium pressure combustion rig at GRC. The theories behind the designs, results of analysis, and experimental test data will be discussed in this report. The combustion system consists of five radially staged rows of injectors, where ten small scale injectors are used in place of a single traditional nozzle. Major accomplishments of the current work include the design of a Multipoint Lean Direct Injection (MLDI) array and associated air blast and pilot fuel injectors, which is expected to meet or exceed the goal of a 75 percent reduction in LTO NOx from CAEP6 standards. This design incorporates a reduced number of injectors over previous multipoint designs, simplified and lightweight components, and a very compact combustor section. Additional outcomes of the program are validation that the design of these combustion systems can be aided by the use of Computational Fluid Dynamics to predict and reduce emissions. Furthermore, the staging of fuel through the individually controlled radially staged injector rows successfully demonstrated improved low power operability as well as improvements in emissions over previous multipoint designs. Additional comparison between Jet- A fuel and a hydrotreated biofuel is made to determine viability of the technology for use with alternative fuels. Finally, the operability of the array and associated nozzles proved to be very stable without requiring additional active or passive control systems. A number of publications have been publish

Early Exposure to Traffic-Related Air Pollution, Respiratory Symptoms at 4 Years of Age, and Potential Effect Modification by Parental Allergy, Stressful Family Events, and Sex: A Prospective Follow-up Study of the PARIS Birth Cohort

PubMed Central

Rancière, Fanny; Bougas, Nicolas; Viola, Malika; Momas, Isabelle

2016-01-01

Background: The relation between traffic-related air pollution (TRAP) exposure and the incidence of asthma/allergy in preschool children has been widely studied, but results remain heterogeneous, possibly due to differences in methodology and susceptibility to TRAP. Objectives: We aimed to study the relation of early TRAP exposure with the development of respiratory/allergic symptoms and asthma during preschool years, and to investigate parental allergy, “stressful” family events, and sex as possible effect modifiers. Methods: We examined data of 2,015 children from the PARIS birth cohort followed up with repeated questionnaires completed by parents until age 4 years. TRAP exposure in each child’s first year of life was estimated by nitrogen oxides (NOx) air dispersion modeling, taking into account both home and day care locations. Association between TRAP exposure and patterns of wheezing, dry night cough, and rhinitis symptoms was studied using multinomial logistic regression models adjusted for potential confounders. Effect modification by parental history of allergy, stressful family events, and sex was investigated. Results: An interquartile range (26 μg/m3) increase in NOx levels was associated with an increased odds ratio (OR) of persistent wheezing at 4 years (adjusted OR = 1.27; 95% confidence interval: 1.09, 1.47). TRAP exposure was positively associated with persistent wheeze, dry cough, and rhinitis symptoms among children with a parental allergy, those experiencing stressful family events, and boys, but not in children whose parents did not have allergies or experience stressful events, or in girls (all interaction p-values < 0.2). Conclusions: This study supports the hypothesis that not all preschool children are equal regarding TRAP health effects. Parental history of allergy, stressful family events, and male sex may increase their susceptibility to adverse respiratory effects of early TRAP exposure. Citation: Rancière F, Bougas N, Viola M, Momas I. 2017. Early exposure to traffic-related air pollution, respiratory symptoms at 4 years of age, and potential effect modification by parental allergy, stressful family events, and sex: a prospective follow-up study of the PARIS birth cohort. Environ Health Perspect 125:737–745; http://dx.doi.org/10.1289/EHP239 PMID:27219743

Gas turbine topping combustor

DOEpatents

Beer, J.; Dowdy, T.E.; Bachovchin, D.M.

1997-06-10

A combustor is described for burning a mixture of fuel and air in a rich combustion zone, in which the fuel bound nitrogen in converted to molecular nitrogen. The fuel rich combustion is followed by lean combustion. The products of combustion from the lean combustion are rapidly quenched so as to convert the fuel bound nitrogen to molecular nitrogen without forming NOx. The combustor has an air radial swirler that directs the air radially inward while swirling it in the circumferential direction and a radial fuel swirler that directs the fuel radially outward while swirling it in the same circumferential direction, thereby promoting vigorous mixing of the fuel and air. The air inlet has a variable flow area that is responsive to variations in the heating value of the fuel, which may be a coal-derived fuel gas. A diverging passage in the combustor in front of a bluff body causes the fuel/air mixture to recirculate with the rich combustion zone. 14 figs.

Low NOx Heavy Fuel Combustor Concept Program

NASA Technical Reports Server (NTRS)

Novick, A. S.; Troth, D. L.

1981-01-01

The development of the technology required to operate an industrial gas turbine combustion system on minimally processed, heavy petroleum or residual fuels having high levels of fuel-bound nitrogen (FBN) while producing acceptable levels of exhaust emissions is discussed. Three combustor concepts were designed and fabricated. Three fuels were supplied for the combustor test demonstrations: a typical middle distillate fuel, a heavy residual fuel, and a synthetic coal-derived fuel. The primary concept was an air staged, variable-geometry combustor designed to produce low emissions from fuels having high levels of FBN. This combustor used a long residence time, fuel-rich primary combustion zone followed by a quick-quench air mixer to rapidly dilute the fuel rich products for the fuel-lean final burnout of the fuel. This combustor, called the rich quench lean (RQL) combustor, was extensively tested using each fuel over the entire power range of the model 570 K engine. Also, a series of parameteric tests was conducted to determine the combustor's sensitivity to rich-zone equivalence ratio, lean-zone equivalence ratio, rich-zone residence time, and overall system pressure drop. Minimum nitrogen oxide emissions were measured at 50 to 55 ppmv at maximum continuous power for all three fuels. Smoke was less than a 10 SAE smoke number.

Combustion oscillation: Chemical control showing mechanistic link to recirculation zone purge time

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gemmen, R.S.; Richards, G.A.; Yip, M.J.

1995-12-01

Active control mechanisms are being examined for lean premix combustion applications, such as gas turbine generators. Lean premix combustors are susceptible to large combustion oscillations, particularly when driven very lean to achieve low NOx. While past design work has been focussed on understanding the source of the oscillation and modifying the combustor to avoid such oscillations, commercial combustion designers have more recently considered applying new control elements. As part of the U.S. Department of Energy`s Advanced Gas Turbine Systems Program, the Morgantown Energy Technology Center is investigating various active control techniques. This paper presents results from experiments studying the effectmore » of pilot fuel modulation on combustor oscillation and pollutant emissions for a pilot stabilized dump swirl combustor, typical of gas turbine combustors. The results show that a significant level of attenuation can be achieved in the combustor pressure oscillation (50 to 90 percent) while only moderately affecting pollutant emissions. The control mechanism producing the attenuation is shown to be purely chemical in nature, rather than fluid mechanic. In addition, the frequency region over which control is obtained is shown to be related to the recirculation zone purge time. For this reason, control can be achieved at control frequencies much lower than the frequency of oscillation.« less

Systems Design and Experimental Evaluation of a High-Altitude Relight Test Facility

NASA Astrophysics Data System (ADS)

Paxton, Brendan

Novel advances in gas turbine engine combustor technology, led by endeavors into fuel efficiency and demanding environmental regulations, have been fraught with performance and safety concerns. While the majority of low emissions gas turbine engine combustor technology has been necessary for power generation applications, the push for ultra-low NOx combustion in aircraft jet engines has been ever present. Recent state-of-the-art combustor designs notably tackle historic emissions challenges by operating at fuel-lean conditions, which are characterized by an increase in the amount of air flow sent to the primary combustion zone. While beneficial in reducing NOx emissions, the fuel-lean mechanisms that characterize these combustor designs rely heavily upon high-energy and high-velocity air flows to sufficiently mix and atomize fuel droplets, ultimately leading to flame stability concerns during low-power operation. When operating at high-altitude conditions, these issues are further exacerbated by the presence of low ambient air pressures and temperatures, which can lead to engine flame-out situations and hamper engine relight attempts. To aid academic and industrial research ventures into improving the high-altitude lean blow-out and relight performance of modern gas turbine engine combustor technologies, the High-Altitude Relight Test Facility (HARTF) was designed and constructed at the University of Cincinnati (UC) Combustion and Fire Research Laboratory (CFRL). Following its construction, an experimental evaluation of its abilities to facilitate optically-accessible ignition, combustion, and spray testing for gas turbine engine combustor hardware at simulated high-altitude conditions was performed. In its evaluation, performance limit references were established through testing of the HARTF vacuum and cryogenic air-chilling capabilities. These tests were conducted with regard to end-user control---the creation and the maintenance of a realistic high-altitude environment simulation. To evaluate future testing applications, as well as to understand the abilities of the HARTF to accommodate different sizes and configurations of industrial gas turbine engine combustor hardware, ignition testing was conducted at challenging high-altitude windmilling conditions with a linearly-arranged five-swirler array, replicating the implementation of a multi-cup combustor sector.

Design and preliminary results of a fuel flexible industrial gas turbine combustor

NASA Technical Reports Server (NTRS)

Novick, A. S.; Troth, D. L.; Yacobucci, H. G.

1981-01-01

The design characteristics are presented of a fuel tolerant variable geometry staged air combustor using regenerative/convective cooling. The rich/quench/lean variable geometry combustor is designed to achieve low NO(x) emission from fuels containing fuel bound nitrogen. The physical size of the combustor was calculated for a can-annular combustion system with associated operating conditions for the Allison 570-K engine. Preliminary test results indicate that the concept has the potential to meet emission requirements at maximum continuous power operation. However, airflow sealing and improved fuel/air mixing are necessary to meet Department of Energy program goals.

Simulations of NOx Emissions from Low Emissions Discrete Jet Injector Combustor Tests

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Breisacher, Kevin

2014-01-01

An experimental and computational study was conducted to evaluate the performance and emissions characteristics of a candidate Lean Direct Injection (LDI) combustor configuration with a mix of simplex and airblast injectors. The National Combustion Code (NCC) was used to predict the experimentally measured EINOx emissions for test conditions representing low power, medium power, and high-power engine cycle conditions. Of the six cases modeled with the NCC using a reduced-kinetics finite-rate mechanism and lagrangian spray modeling, reasonable predictions of combustor exit temperature and EINOx were obtained at two high-power cycle conditions.

Effects of Low Sulfur Fuel and a Catalyzed Particle Trap on the Composition and Toxicity of Diesel Emissions

PubMed Central

McDonald, Jacob D.; Harrod, Kevin S.; Seagrave, JeanClare; Seilkop, Steven K.; Mauderly, Joe L.

2004-01-01

In this study we compared a “baseline” condition of uncontrolled diesel engine exhaust (DEE) emissions generated with current (circa 2003) certification fuel to an emissions-reduction (ER) case with low sulfur fuel and a catalyzed particle trap. Lung toxicity assessments (resistance to respiratory viral infection, lung inflammation, and oxidative stress) were performed on mice (C57Bl/6) exposed by inhalation (6 hr/day for 7 days). The engine was operated identically (same engine load) in both cases, and the inhalation exposures were conducted at the same exhaust dilution rate. For baseline DEE, this dilution resulted in a particle mass (PM) concentration of approximately 200 μg/m3 PM, whereas the ER reduced the PM and almost every other measured constituent [except nitrogen oxides (NOx)] to near background levels in the exposure atmospheres. These measurements included PM, PM size distribution, PM composition (carbon, ions, elements), NOx, carbon monoxide, speciated/total volatile hydrocarbons, and several classes of semi-volatile organic compounds. After exposure concluded, one group of mice was immediately sacrificed and assessed for inflammation and oxidative stress in lung homogenate. Another group of mice were intratracheally instilled with respiratory syncytial virus (RSV), and RSV lung clearance and inflammation was assessed 4 days later. Baseline DEE produced statistically significant biological effects for all measured parameters. The use of low sulfur fuel and a catalyzed trap either completely or nearly eliminated the effects. PMID:15345344

Three-dimensional analysis of flow-chemical interaction within a single square channel of a lean NO x trap catalyst.

PubMed

Fornarelli, Francesco; Dadduzio, Ruggiero; Torresi, Marco; Camporeale, Sergio Mario; Fortunato, Bernardo

2018-02-01

A fully 3D unsteady Computational Fluid Dynamics (CFD) approach coupled with heterogeneous reaction chemistry is presented in order to study the behavior of a single square channel as part of a Lean [Formula: see text] Traps. The reliability of the numerical tool has been validated against literature data considering only active BaO site. Even though the input/output performance of such catalyst has been well known, here the spatial distribution within a single channel is investigated in details. The square channel geometry influences the flow field and the catalyst performance being the flow velocity distribution on the cross section non homogeneous. The mutual interaction between the flow and the active catalyst walls influences the spatial distribution of the volumetric species. Low velocity regions near the square corners and transversal secondary flows are shown in several cross-sections along the streamwise direction at different instants. The results shed light on the three-dimensional characteristic of both the flow field and species distribution within a single square channel of the catalyst with respect to 0-1D approaches.

Combustion and NOx emission characteristics with respect to staged-air damper opening in a 600 MWe down-fired pulverized-coal furnace under deep-air-staging conditions.

PubMed

Kuang, Min; Li, Zhengqi; Wang, Zhihua; Jing, Xinjing; Liu, Chunlong; Zhu, Qunyi; Ling, Zhongqian

2014-01-01

Deep-air-staging combustion conditions, widely used in tangential-fired and wall-arranged furnaces to significantly reduce NOx emissions, are premature up to now in down-fired furnaces that are designed especially for industry firing low-volatile coals such as anthracite and lean coal. To uncover combustion and NOx emission characteristics under deep-air-staging conditions within a newly operated 600 MWe down-fired furnace and simultaneously understand the staged-air effect on the furnace performance, full-load industrial-size measurements taken of gas temperatures and species concentrations in the furnace, CO and NOx emissions in flue gas, and carbon in fly ash were performed at various staged-air damper openings of 10%, 20%, 30%, and 50%. Increasing the staged-air damper opening, gas temperatures along the flame travel (before the flame penetrating the staged-air zone) increased initially but then decreased, while those in the staged-air zone and the upper part of the hopper continuously decreased and increased, respectively. On opening the staged-air damper to further deepen the air-staging conditions, O2 content initially decreased but then increased in both two near-wall regions affected by secondary air and staged air, respectively, whereas CO content in both two regions initially increased but then decreased. In contrast to the conventional understanding about the effects of deep-air-staging conditions, here increasing the staged-air damper opening to deepen the air-staging conditions essentially decreased the exhaust gas temperature and carbon in fly ash and simultaneously increased both NOx emissions and boiler efficiency. In light of apparently low NOx emissions and high carbon in fly ash (i.e., 696-878 mg/m(3) at 6% O2 and 9.81-13.05%, respectively) developing in the down-fired furnace under the present deep-air-staging conditions, further adjustments such as enlarging the staged-air declination angle to prolong pulverized-coal residence times in the furnace should be considered to improve the deep-air-staging combustion configuration.

Industrial Application of an Improved Multiple Injection and Multiple Staging Combustion Technology in a 600 MWe Supercritical Down-Fired Boiler.

PubMed

Song, Minhang; Zeng, Lingyan; Chen, Zhichao; Li, Zhengqi; Zhu, Qunyi; Kuang, Min

2016-02-02

To solve the water wall overheating in lower furnace, and further reduce NOx emissions and carbon in fly ash, continuous improvement of the previously proposed multiple injection and multiple staging combustion (MIMSC) technology lies on three aspects: (1) along the furnace arch breadth, changing the previously centralized 12 burner groups into a more uniform pattern with 24 burners; (2) increasing the mass ratio of pulverized coal in fuel-rich flow to that in fuel-lean flow from 6:4 to 9:1; (3) reducing the arch-air momentum by 23% and increasing the tertiary-air momentum by 24%. Industrial-size measurements (i.e., adjusting overfire air (OFA) damper opening of 20-70%) uncovered that, compared with the prior MIMSC technology, the ignition distance of fuel-rich coal/air flow shortened by around 1 m. The gas temperature in the lower furnace was symmetric and higher, the flame kernel moved upward and therefore made the temperature in near-wall region of furnace hopper decrease by about 400 °C, the water wall overheating disappeared completely. Under the optimal OFA damper opening (i.e, 55%), NOx emissions and carbon in fly ash attained levels of 589 mg/m(3) at 6% O2 and 6.18%, respectively, achieving NOx and carbon in fly ash significant reduction by 33% and 37%, respectively.

Control of harmful hydrocarbon species in the exhaust of modern advanced GDI engines

NASA Astrophysics Data System (ADS)

Hasan, A. O.; Abu-jrai, A.; Turner, D.; Tsolakis, A.; Xu, H. M.; Golunski, S. E.; Herreros, J. M.

2016-03-01

A qualitative and quantitative analysis of toxic but currently non-regulated hydrocarbon compounds ranging from C5-C11, before and after a zoned three-way catalytic converter (TWC) in a modern gasoline direct injection (GDI) engine has been studied using gas chromatography-mass spectrometry (GC-MS). The GDI engine has been operated under conventional and advanced combustion modes, which result in better fuel economy and reduced levels of NOx with respect to standard SI operation. However, these fuel-efficient conditions are more challenging for the operation of a conventional TWC, and could lead to higher level of emissions released to the environment. Lean combustion leads to the reduction in pumping losses, fuel consumption and in-cylinder emission formation rates. However, lean HCCI will lead to high levels of unburnt HCs while the presence of oxygen will lower the TWC efficiency for NOx control. The effect on the catalytic conversion of the hydrocarbon species of the addition of hydrogen upstream the catalyst has been also investigated. The highest hydrocarbon engine-out emissions were produced for HCCI engine operation at low engine load operation. The catalyst was able to remove most of the hydrocarbon species to low levels (below the permissible exposure limits) for standard and most of the advanced combustion modes, except for naphthalene (classified as possibly carcinogenic to humans by the International Agency for Research on Cancer) and methyl-naphthalene (which has the potential to cause lung damage). However, when hydrogen was added upstream of the catalyst, the catalyst conversion efficiency in reducing methyl-naphthalene and naphthalene was increased by approximately 21%. This results in simultaneous fuel economy and environmental benefits from the effective combination of advanced combustion and novel aftertreatment systems.

Potential Impact of the National Plan for Future Electric Power Supply on Air Quality in Korea

NASA Astrophysics Data System (ADS)

Shim, C.; Hong, J.

2014-12-01

Korean Ministry of Trade, Industry and Energy (MOTIE) announced the national plan for Korea's future electric power supply (2013 - 2027) in 2013. According to the plan, the national demand for electricity will be increased by 60% compared to that of 2010 and primary energy sources for electric generation will still lean on the fossil fuels such as petroleum, LNG, and coal, which would be a potential threat to air quality of Korea. This study focused on two subjects: (1) How the spatial distribution of the primary air pollutant's emissions (i.e., NOx, SOx, CO, PM) will be changed and (2) How the primary emission changes will influence on the national ambient air quality including ozone in 2027. We used GEOS-Chem model simulation with modification of Korean emissions inventory (Clean Air Policy Support System (CAPSS)) to simulate the current and future air quality in Korea. The national total emissions of CO, NOx, SOx, PM in year 2027 will be increased by 3%, 8%, 13%, 2%, respectively compared to 2010 and there are additional concern that the future location of the power plants will be closer to the Seoul Metropolitan Area (SMA), where there are approximately 20 million population vulnerable to the potentially worsened air quality. While there are slight increase of concentration of CO, NOx, SOx, and PM in 2027, the O3 concentration is expected to be similar to the level of 2010. Those results may imply the characteristics of air pollution in East Asia such as potentially severe O3 titration and poorer O3/CO or O3/NOx ratio. Furthermore, we will discuss on the impact of transboundary pollution transport from China in the future, which is one of the large factors to control the air quality of Korea.

Rapid mix concepts for low emission combustors in gas turbine engines

NASA Technical Reports Server (NTRS)

Talpallikar, Milind V.; Smith, Clifford E.; Lai, Ming-Chia

1990-01-01

NASA LeRC has identified the Rich burn/Quick mix/Lean burn (RQL) combustor as a potential gas turbine combustor concept to reduce NOx emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NOx levels, NASA LeRC soon will test a flametube version of an RQL combustor. The critical technology needed for the RQL combustor is a method of quickly mixing combustion air with rich burn gases. Two concepts were proposed to enhance jet mixing in a circular cross-section: the Asymmetric Jet Penetration (AJP) concept; and the Lobed Mixer (LM) concept. In Phase 1, two preliminary configurations of the AJP concept were compared with a conventional 12-jet radial-inflow slot design. The configurations were screened using an advanced 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Both non-reacting and reacting analyses were performed. For an objective comparison, the conventional design was optimized by parametric variation of the jet-to-mainstream momentum flux (J) ratio. The optimum J was then employed in the AJP simulations. Results showed that the three-jet AJP configuration was superior in overall mixedness compared to the conventional design. However, in regards to NOx emissions, the AJP configuration was inferior. The higher emission level for AJP was caused by a single hot spot located in the wake of the central jet as it entered the combustor. Ways of maintaining good mixedness while eliminating the hot spot were identified for Phase 2 study. Overall, Phase 1 showed the viability of using CFD analyses to evaluate quick-mix concepts. A high probability exists that advancing mixing concepts will reduce NOx emissions in RQL combustors, and should be explored in Phase 2, by parallel numerical and experimental work.

Low NO(x) Combustor Development

NASA Technical Reports Server (NTRS)

Kastl, J. A.; Herberling, P. V.; Matulaitis, J. M.

2005-01-01

The goal of these efforts was the development of an ultra-low emissions, lean-burn combustor for the High Speed Civil Transport. The HSCT Mach 2.4 FLADE C1 Cycle was selected as the baseline engine cycle. A preliminary compilation of performance requirements for the HSCT combustor system was developed. The emissions goals of the program, baseline engine cycle, and standard combustor performance requirements were considered in developing the compilation of performance requirements. Seven combustor system designs were developed. The development of these system designs was facilitated by the use of spreadsheet-type models which predicted performance of the combustor systems over the entire flight envelope of the HSCT. A chemical kinetic model was developed for an LPP combustor and employed to study NO(x) formation kinetics, and CO burnout. These predictions helped to define the combustor residence time. Five fuel-air mixer concepts were analyzed for use in the combustor system designs. One of the seven system designs, one using the Swirl-Jet and Cyclone Swirler fuel-air mixers, was selected for a preliminary mechanical design study.

A study of low emissions gas turbine combustions

NASA Technical Reports Server (NTRS)

Adelman, Henry G.

1994-01-01

Analytical studies have been conducted to determine the best methods of reducing NO(x) emissions from proposed civilian supersonic transports. Modifications to the gas turbine engine combustors and the use of additives were both explored. It was found that combustors which operated very fuel rich or lean appear to be able to meet future emissions standards. Ammonia additives were also effective in removing NO(x), but residual ammonia remained a problem. Studies of a novel combustor which reduces emissions and improves performance were initiated. In a related topic, a study was begun on the feasibility of using supersonic aircraft to obtain atmospheric samples. The effects of shock heating and compression on sample integrity were modeled. Certain chemical species, including NO2, HNO3, and ClONO2 were found to undergo changes to their composition after they passed through shock waves at Mach 2. The use of detonation waves to enhance mixing and combustion in supersonic airflows was also investigated. This research is important to the use of airbreathing propulsion to obtain orbital speeds and access to space. Both steady and pulsed detonation waves were shown to improve engine performance.

Investigation of micro burner performance during porous media combustion for surface and submerged flames

NASA Astrophysics Data System (ADS)

Janvekar, Ayub Ahmed; Abdullah, M. Z.; Ahmad, Z. A.; Abas, Aizat; Hussien, Ahmed A.; Kataraki, Pramod S.; Mohamed, Mazlan; Husin, Azmi; Fadzli, Khairil

2018-05-01

Porous media combustion is considered to be one of the popular choice due to its tremendous advantages. Such type of combustion liberates not only super stable flame but also maintains emissions parameters below thresholds level. Present study incorporates reaction and preheat layer with discrete and foam type of materials respectively. Burner was made to run in ultra-lean mode. Optimum equivalence ratio was found out to be 0.7 for surface flame, while 0.6 during submerged flame condition. Maximum thermal efficiency was noted to be 81%. Finally, emissions parameters where recorded continuously to measure NOx and CO, which were under global limits.

Method to monitor HC-SCR catalyst NOx reduction performance for lean exhaust applications

DOEpatents

Viola, Michael B [Macomb Township, MI; Schmieg, Steven J [Troy, MI; Sloane, Thompson M [Oxford, MI; Hilden, David L [Shelby Township, MI; Mulawa, Patricia A [Clinton Township, MI; Lee, Jong H [Rochester Hills, MI; Cheng, Shi-Wai S [Troy, MI

2012-05-29

A method for initiating a regeneration mode in selective catalytic reduction device utilizing hydrocarbons as a reductant includes monitoring a temperature within the aftertreatment system, monitoring a fuel dosing rate to the selective catalytic reduction device, monitoring an initial conversion efficiency, selecting a determined equation to estimate changes in a conversion efficiency of the selective catalytic reduction device based upon the monitored temperature and the monitored fuel dosing rate, estimating changes in the conversion efficiency based upon the determined equation and the initial conversion efficiency, and initiating a regeneration mode for the selective catalytic reduction device based upon the estimated changes in conversion efficiency.

Tracking nitrogen oxides, nitrous acid, and nitric acid from biomass burning

NASA Astrophysics Data System (ADS)

Chai, J.; Miller, D. J.; Scheuer, E. M.; Dibb, J. E.; Hastings, M. G.

2017-12-01

Biomass burning emissions are an important source of atmospheric nitrogen oxides (NOx = NO + NO2) and nitrous acid (HONO), which play important roles in atmosphere oxidation capacity (hydroxyl radical and ozone formation) and have severe impacts on air quality and climate in the presence of sunlight and volatile organic compounds. However, tracking NOx and HONO and their chemistry in the atmosphere based on concentration alone is challenging. Isotopic analysis provides a potential tracking tool. In this study, we measured the nitrogen isotopic composition (δ15N) of NOx (NO + NO2) and HONO, and soluble HONO and HNO3 during the Fire Influence on Regional and Global Environments Experiment (FIREX) laboratory experiments at the Missoula Fire Laboratory. Our newly developed and validated annular denuder system (ADS) enabled us to effectively trap HONO prior to a NOx collection system in series for isotopic analysis. In total we investigated 25 "stack" fires of various biomass materials where the emissions were measured within a few seconds of production by the fire. HONO concentration was measured in parallel using mist chamber/ion chromatography (MC/IC). The recovered mean HONO concentrations from ADS during the burn of each fire agree well with that measured via MC/IC. δ15N-NOx ranged from -4.3 ‰ to + 7.0 ‰ with a median of 0.7 ‰. Combined with a similar, recent study by our group [Fibiger et al., ES&T, 2017] the δ15N-NOx follows a linear relationship with δ15N-biomass (δ15N-NOx =0.94 x δ15N-biomass +1.98; R2=0.72). δ15N-HONO ranged from -5.3 to +8.3 ‰ with a median of 1.4 ‰. While both HONO and NOx are sourced from N in the biomass fuel, the secondary formation of HONO likely induces fractionation of the N that leads to the difference between δ15N-NOx and δ15N-HONO. We found a correlation of δ15N-HONO= 0.86 x δ15N-NOx + 0.52 (R2=0.55), which can potentially be used to track the chemistry of HONO formation following fire emissions. The methods used in this study will be further applied in field studies, to quantitatively track NOx and HONO in Western US wildfire plumes and their impact on the oxidation chemistry of the atmosphere.

FY2015 Annual Report for Alternative Fuels DISI Engine Research.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sjöberg, Carl-Magnus G.

2016-01-01

Climate change and the need to secure energy supplies are two reasons for a growing interest in engine efficiency and alternative fuels. This project contributes to the science-base needed by industry to develop highly efficient DISI engines that also beneficially exploit the different properties of alternative fuels. Our emphasis is on lean operation, which can provide higher efficiencies than traditional non-dilute stoichiometric operation. Since lean operation can lead to issues with ignition stability, slow flame propagation and low combustion efficiency, we focus on techniques that can overcome these challenges. Specifically, fuel stratification is used to ensure ignition and completeness ofmore » combustion but has soot- and NOx- emissions challenges. For ultralean well-mixed operation, turbulent deflagration can be combined with controlled end-gas auto-ignition to render mixed-mode combustion that facilitates high combustion efficiency. However, the response of both combustion and exhaust emissions to these techniques depends on the fuel properties. Therefore, to achieve optimal fuel-economy gains, the engine combustion-control strategies must be adapted to the fuel being utilized.« less

A Study on the Effect of Stratified Mixture Formation on Combustion Characteristics in a Constant Volume Combustion Chamber

NASA Astrophysics Data System (ADS)

Lee, Kihyung; Lee, Changhee; Jeoung, Haeyoung

It is well known that a lean burn engine caused by stratified mixture formation has many kinds of advantages to combustion characteristics, such as higher thermal efficiency and lower CO, NOx levels than conventional homogeneous mixture combustion. Although this combustion can achieve low fuel consumption, it produces much unburned hydrocarbon and soot because of inhomogeneity of the charge mixture in the combustion chamber. Therefore, it is necessary to investigate the effect of mixture formation on combustion characteristics in order to obtain the stable lean combustion. In this paper, fundamental studies for stratified combustion were carried out using a constant volume combustion chamber. The effect of mixture formation on the combustion characteristics in the chamber was examined experimentally. In addition, the effect of turbulence on stratified charge combustion process was observed by schlieren photography. From this study, as the swirl intensity increases, (Sv)max is rapidly enhanced and the period of combustion is shortened. We also find that the stratification degree can be quantified by using burning velocity and it was controlled by induced air pressure and turbulent intensity.

Onboard Plasmatron Hydrogen Production for Improved Vehicles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daniel R. Cohn; Leslie Bromberg; Kamal Hadidi

2005-12-31

A plasmatron fuel reformer has been developed for onboard hydrogen generation for vehicular applications. These applications include hydrogen addition to spark-ignition internal combustion engines, NOx trap and diesel particulate filter (DPF) regeneration, and emissions reduction from spark ignition internal combustion engines First, a thermal plasmatron fuel reformer was developed. This plasmatron used an electric arc with relatively high power to reform fuels such as gasoline, diesel and biofuels at an oxygen to carbon ratio close to 1. The draw back of this device was that it has a high electric consumption and limited electrode lifetime due to the high temperaturemore » electric arc. A second generation plasmatron fuel reformer was developed. It used a low-current high-voltage electric discharge with a completely new electrode continuation. This design uses two cylindrical electrodes with a rotating discharge that produced low temperature volumetric cold plasma., The lifetime of the electrodes was no longer an issue and the device was tested on several fuels such as gasoline, diesel, and biofuels at different flow rates and different oxygen to carbon ratios. Hydrogen concentration and yields were measured for both the thermal and non-thermal plasmatron reformers for homogeneous (non-catalytic) and catalytic reforming of several fuels. The technology was licensed to an industrial auto part supplier (ArvinMeritor) and is being implemented for some of the applications listed above. The Plasmatron reformer has been successfully tested on a bus for NOx trap regeneration. The successful development of the plasmatron reformer and its implementation in commercial applications including transportation will bring several benefits to the nation. These benefits include the reduction of NOx emissions, improving engine efficiency and reducing the nation's oil consumption. The objective of this program has been to develop attractive applications of plasmatron fuel reformer technology for onboard applications in internal combustion engine vehicles using diesel, gasoline and biofuels. This included the reduction of NOx and particulate matter emissions from diesel engines using plasmatron reformer generated hydrogen-rich gas, conversion of ethanol and bio-oils into hydrogen rich gas, and the development of new concepts for the use of plasmatron fuel reformers for enablement of HCCI engines.« less

Flashback Detection Sensor for Hydrogen Augmented Natural Gas Combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, J.D.; Chorpening, B.T.; Sidwell, T.

2007-05-01

The use of hydrogen augmented fuel is being investigated by various researchers as a method to extend the lean operating limit, and potentially reduce thermal NOx formation in natural gas fired lean premixed (LPM) combustion systems. The resulting increase in flame speed during hydrogen augmentation, however, increases the propensity for flashback in LPM systems. Real-time in-situ monitoring of flashback is important for the development of control strategies for use of hydrogen augmented fuel in state-of-the-art combustion systems, and for the development of advanced hydrogen combustion systems. The National Energy Technology Laboratory (NETL) and Woodward Industrial Controls are developing a combustionmore » control and diagnostics sensor (CCADS), which has already been demonstrated as a useful sensor for in-situ monitoring of natural gas combustion, including detection of important combustion events such as flashback and lean blowoff. Since CCADS is a flame ionization sensor technique, the low ion concentration produced in pure hydrogen combustion raises concerns of whether CCADS can be used to monitor flashback in hydrogen augmented combustion. This paper discusses CCADS tests conducted at 0.2-0.6 MPa (2-6 atm), demonstrating flashback detection with fuel compositions up to 80% hydrogen (by volume) mixed with natural gas. NETL’s Simulation Validation (SimVal) combustor offers full optical access to pressurized combustion during these tests. The CCADS data and high-speed video show the reaction zone moves upstream into the nozzle as the hydrogen fuel concentration increases, as is expected with the increased flame speed of the mixture. The CCADS data and video also demonstrate the opportunity for using CCADS to provide the necessary in-situ monitor to control flashback and lean blowoff in hydrogen augmented combustion applications.« less

Impacts of continuously regenerating trap and particle oxidation catalyst on the NO2 and particulate matter emissions emitted from diesel engine.

PubMed

Liu, Zhihua; Ge, Yunshan; Tan, Jianwei; He, Chao; Shah, Asad Naeem; Ding, Yan; Yu, Linxiao; Zhao, Wei

2012-01-01

Two continuously regenerating diesel particulate filter (CRDPF) with different configurations and one particles oxidation catalyst (POC) were employed to perform experiments in a controlled laboratory setting to evaluate their effects on NO2, smoke and particle number emissions. The results showed that the application of the after-treatments increased the emission ratios of NO2/NOx significantly. The results of smoke emissions and particle number (PN) emissions indicated that both CRDPFs had sufficient capacity to remove more than 90% of total particulate matter (PM) and more than 97% of solid particles. However, the POC was able to remove the organic components of total PM, and only partially to remove the carbonaceous particles with size less than 30 nm. The negligible effects of POC on larger particles were observed due to its honeycomb structure leads to an inadequate residence time to oxidize the solid particles or trap them. The particles removal efficiencies of CRDPFs had high degree of correlations with the emission ratio of NO2/NOx. The PN emission results from two CRDPFs indicated that more NO2 generating in diesel oxidation catalyst section could obtain the higher removal efficiency of solid particles. However this also increased the risk of NO2 exposure in atmosphere.

Spatial and temporal differences in traffic-related air pollution in three urban neighborhoods near an interstate highway

PubMed Central

Patton, Allison P.; Perkins, Jessica; Zamore, Wig; Levy, Jonathan I.; Brugge, Doug; Durant, John L.

2014-01-01

Relatively few studies have characterized differences in intra- and inter-neighborhood traffic-related air pollutant (TRAP) concentrations and distance-decay gradients in along an urban highway for the purposes of exposure assessment. The goal of this work was to determine the extent to which intra- and inter-neighborhood differences in TRAP concentrations can be explained by traffic and meteorology in three pairs of neighborhoods along Interstate 93 (I-93) in the metropolitan Boston area (USA). We measured distance-decay gradients of seven TRAPs (PNC, pPAH, NO, NOX, BC, CO, PM2.5) in near-highway (<400 m) and background areas (>1 km) in Somerville, Dorchester/South Boston, Chinatown and Malden to determine whether (1) spatial patterns in concentrations and inter-pollutant correlations differ between neighborhoods, and (2) variation within and between neighborhoods can be explained by traffic and meteorology. The neighborhoods ranged in area from 0.5 to 2.3 km2. Mobile monitoring was performed over the course of one year in each pair of neighborhoods (one pair of neighborhoods per year in three successive years; 35-47 days of monitoring in each neighborhood). Pollutant levels generally increased with highway proximity, consistent with I-93 being a major source of TRAP; however, the slope and extent of the distance-decay gradients varied by neighborhood as well as by pollutant, season and time of day. Correlations among pollutants differed between neighborhoods (e.g., ρ = 0.35-0.80 between PNC and NOX and ρ = 0.11-0.60 between PNC and BC) and were generally lower in Dorchester/South Boston than in the other neighborhoods. We found that the generalizability of near-road gradients and near-highway/urban background contrasts was limited for near-highway neighborhoods in a metropolitan area with substantial local street traffic. Our findings illustrate the importance of measuring gradients of multiple pollutants under different ambient conditions in individual near-highway neighborhoods for health studies involving inter-neighborhood comparisons. PMID:25364295

Analysis and design of lean direct injection fuel nozzles by eddy resolved turbulence simulation

NASA Astrophysics Data System (ADS)

Ryon, Jason Allen

Combustion systems in gas turbine engines are subjected to particular scrutiny in regards to the emissions which they produce. Of special interest are the emissions of Oxides of Nitrogen (NOx), which have a direct impact on air quality as well as health aspects. There is a need in the industry for elegant designs for these combustion systems which reduce the formation of NOx. The present study includes an in depth analysis of a state-of-the art prefilming airblast injector which is designed for achieving low NOx. The design has been studied through the use of turbulence resolving simulation to differentiate what is important for the design of this system. The OpenFOAM CFD software, with a Delayed Detached Eddy Simulation (DDES) model recently developed at Iowa State University, is shown to provide a suitable design tool which has been used to accurately predict a variety of parameters important to this combustion system. Of particular interest are the mixing characteristics of the atomizer, which have been studied through a series of CFD simulations including single-phase, multi-species, and multi-phase simulations. Turbulence simulations are validated by comparison to United Technologies Aerospace Systems (UTAS) data with air only. It is shown how DDES is able to capture the downstream mixing of air streams. Finally, a novel atomizer has been designed with these methods which is intended to promote thorough mixing. The CFD mixing characteristics are described and compared to the existing injector.

Flame Stability Limit and Exhaust Emissions of Low Calorific Fuel Combustion in Turbulent Diffusion Combustor for a Small-Scale Fuel Cell

NASA Astrophysics Data System (ADS)

Koseki, Hidenori

This paper describes an investigation conducted on flame stability and exhaust emissions from a turbulent diffusion combustor, fueled with low-calorific gas, for a small-scale fuel cell. It is important to maintain flame stability in the combustor, even under lean fuel conditions, and to suppress CO emission in the exhaust gas. An imitation off-gas, in which hydrogen and methane were diluted by adding nitrogen, with Wobbe indices ranging from ca. 4400-8700, corresponding to the fuel utility ratio of 90%-60%in the fuel cell, was supplied to the combustor, and the blow-off limits, CO, and NOx emissions were experimentally investigated. The results show that the blow-off excess air ratios increases with an increasing Wobbe index and with decreasing fuel input to the combustor, and that they are proportional to the hydrogen concentration in the fuel to the power of 0.5-1.0. In addition, it was found that the Damköhler numbers at blow-off limits decreased with decreasing fuel input and with increasing Wobbe indices, and that the product of (SS / V·M)A[H2][O2]0.5 was constant at blow-off limits. Furthermore, NOx emissions from the combustor were low, less than 20ppmV (O2=0%), it was also found that the apparent activation energy of NOx emission derived from Arrhenius plots was almost equal to that of prompt NO in the combustion of imitation off-gas.

Emissions Benefits From Renewable Fuels and Other Alternatives for Heavy-Duty Vehicles

NASA Astrophysics Data System (ADS)

Hajbabaei, Maryam

There is a global effort to expand the use of alternative fuels due to their several benefits such as improving air quality with reducing some criteria emissions, reducing dependency on fossil fuels, and reducing greenhouse gases such as carbon dioxide. This dissertation is focused on investigating the impact of two popular alternative fuels, biodiesel and natural gas (NG), on emissions from heavy-duty engines. Biodiesel is one of the most popular renewable fuels with diesel applications. Although biodiesel blends are reported to reduce particulate matter, carbon monoxide, and total hydrocarbon emissions; there is uncertainty on their impact on nitrogen oxides (NOx) emissions. This dissertation evaluated the effect of biodiesel feedstock, biodiesel blend level, engine technology, and driving conditions on NOx emissions. The results showed that NOx emissions increase with 20% and higher biodiesel blends. Also, in this study some strategies were proposed and some fuel formulations were found for mitigating NOx emissions increases with biodiesel. The impact of 5% biodiesel on criteria emissions specifically NOx was also fully studied in this thesis. As a part of the results of this study, 5% animal-based biodiesel was certified for use in California based on California Air Resources Board emissions equivalent procedure. NG is one of the most prominent alternative fuels with larger reserves compared to crude oil. However, the quality of NG depends on both its source and the degree to which it is processed. The current study explored the impact of various NG fuels, ranging from low methane/high energy gases to high methane/low energy gases, on criteria and toxic emissions from NG engines with different combustion and aftertreatment technologies. The results showed stronger fuel effects for the lean-burn technology bus. Finally, this thesis investigated the impact of changing diesel fuel composition on the criteria emissions from a variety of heavy-duty engine technologies. Emissions from an average diesel fuel used throughout the U.S. were compared with a 10% aromatic, ultra-low sulfur diesel fuel used in California with more stringent air quality regulations. The results showed that the emerging aftertreatment technologies eventually eliminate the benefits of the lower aromatic content/higher cetane number diesel fuels.

Atmospheric emission of NOx from mining explosives: A critical review

NASA Astrophysics Data System (ADS)

Oluwoye, Ibukun; Dlugogorski, Bogdan Z.; Gore, Jeff; Oskierski, Hans C.; Altarawneh, Mohammednoor

2017-10-01

High-energy materials such as emulsions, slurries and ammonium-nitrate fuel-oil (ANFO) explosives play crucial roles in mining, quarrying, tunnelling and many other infrastructure activities, because of their excellent transport and blasting properties. These explosives engender environmental concerns, due to atmospheric pollution caused by emission of dust and nitrogen oxides (NOx) from blasts, the latter characterised by the average emission factor of 5 kg (t AN explosive)-1. This first-of-its-kind review provides a concise literature account of the formation of NOx during blasting of AN-based explosives, employed in surface operations. We estimate the total NOx emission rate from AN-based explosives as 0.05 Tg (i.e., 5 × 104 t) N per annum, compared to the total global annual anthropogenic NOx emissions of 41.3 × 106 t N y-1. Although minor in the global sense, the large localised plumes from blasting exhibit high NOx concentration (500 ppm) exceeding up to 3000 times the international standards. This emission has profound consequences at mining sites and for adjacent atmospheric environment, necessitating expensive management of exclusion zones. The review describes different types of AN energetic materials for civilian applications, and summarises the essential properties and terminologies pertaining to their use. Furthermore, we recapitulate the mechanisms that lead to the formation of the reactive nitrogen species in blasting of AN-based explosives, review their implications to atmospheric air pollution, and compare the mechanisms with those experienced in other thermal and combustion operations. We also examine the mitigation approaches, including guidelines and operational-control measures. The review discusses the abatement technologies such as the formulation of new explosive mixtures, comprising secondary fuels, spin traps and other additives, in light of their effectiveness and efficiency. We conclude the review with a summary of unresolved problems, identifying possible future developments and their impacts on the environment with emphasis on local and workplace loads.

Alkali- and Sulfur-Resistant Tungsten-Based Catalysts for NOx Emissions Control.

PubMed

Huang, Zhiwei; Li, Hao; Gao, Jiayi; Gu, Xiao; Zheng, Li; Hu, Pingping; Xin, Ying; Chen, Junxiao; Chen, Yaxin; Zhang, Zhaoliang; Chen, Jianmin; Tang, Xingfu

2015-12-15

The development of catalysts with simultaneous resistance to alkalis and sulfur poisoning is of great importance for efficiently controlling NOx emissions using the selective catalytic reduction of NOx with NH3 (SCR), because the conventional V2O5/WO3-TiO2 catalysts often suffer severe deactivation by alkalis. Here, we support V2O5 on a hexagonal WO3 (HWO) to develop a V2O5/HWO catalyst, which has exceptional resistance to alkali and sulfur poisoning in the SCR reactions. A 350 μmol g(-1) K(+) loading and the presence of 1,300 mg m(-3) SO2 do not almost influence the SCR activity of the V2O5/HWO catalyst, and under the same conditions, the conventional V2O5/WO3-TiO2 catalysts completely lost the SCR activity within 4 h. The strong resistance to alkali and sulfur poisoning of the V2O5/HWO catalysts mainly originates from the hexagonal structure of the HWO. The HWO allows the V2O5 to be highly dispersed on the external surfaces for catalyzing the SCR reactions and has the relatively smooth surfaces and the size-suitable tunnels specifically for alkalis' diffusion and trapping. This work provides a useful strategy to develop SCR catalysts with exceptional resistance to alkali and sulfur poisoning for controlling NOx emissions from the stationary source and the mobile source.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Partridge Jr, William P.; Choi, Jae-Soon

By directly resolving spatial and temporal species distributions within operating honeycomb monolith catalysts, spatially resolved capillary inlet mass spectrometry (SpaciMS) provides a uniquely enabling perspective for advancing automotive catalysis. Specifically, the ability to follow the spatiotemporal evolution of reactions throughout the catalyst is a significant advantage over inlet-and-effluent-limited analysis. Intracatalyst resolution elucidates numerous catalyst details including the network and sequence of reactions, clarifying reaction pathways; the relative rates of different reactions and impacts of operating conditions and catalyst state; and reaction dynamics and intermediate species that exist only within the catalyst. These details provide a better understanding of how themore » catalyst functions and have basic and practical benefits; e.g., catalyst system design; strategies for on-road catalyst state assessment, control, and on-board diagnostics; and creating robust and accurate predictive catalyst models. Moreover, such spatiotemporally distributed data provide for critical model assessment, and identification of improvement opportunities that might not be apparent from effluent assessment; i.e., while an incorrectly formulated model may provide correct effluent predictions, one that can accurately predict the spatiotemporal evolution of reactions along the catalyst channels will be more robust, accurate, and reliable. In such ways, intracatalyst diagnostics comprehensively enable improved design and development tools, and faster and lower-cost development of more efficient and durable automotive catalyst systems. Beyond these direct contributions, SpaciMS has spawned and been applied to enable other analytical techniques for resolving transient distributed intracatalyst performance. This chapter focuses on SpaciMS applications and associated catalyst insights and improvements, with specific sections related to lean NOx traps, selective catalytic reduction catalysts, oxidation catalysts, and particulate filters. The objective is to promote broader use and development of intracatalyst analytical methods, and thereby expand the insights resulting from this detailed perspective for advancing automotive catalyst technologies.« less

The impact of air pollution to central nervous system in children and adults.

PubMed

Sram, Radim J; Veleminsky, Milos; Veleminsky, Milos; Stejskalová, Jana

2017-12-01

The aim of this paper was to review studies analyzing the associations between air pollution and neurodevelopment in children as well as the effect on adult population. Effect of prenatal exposure to polycyclic aromatic hydrocarbons (PAHs, benzo[a]pyrene, B[a]P) were already studied on cohorts from New York, Poland, China, and Spain. All results indicate changes of child behavior and neurodevelopment at the age of 3-9 years, decrease of IQ, increase of Attention Deficit Hyperactivity Disorder (ADHD), decrease of brain-derived neurotrophic factor (BDNF), reduction of left hemisphere white matter. Effect of traffic-related air pollution (TRAP) to neurobehavioral development in children, measured as PM2.5 (particulate matter <2.5 µm), PM10, elemental carbon (EC), black smoke (BC), NO2, NOx, were studied in USA, Spain, Italy, and South Korea. Increased concentrations of TRAP were associated with the increase of ADHD, autism, affected cognitive development; PM2.5 decreased the expression of BDNF in placenta. Increased concentrations of PM2.5 affected adults cognition (episodic memory), increased major depressive disorders. Increased concentrations of NO2 were associated with dementia, NOx with Parkinson's disease. Increased concentrations of PAHs, PM2.5 and NO2 in polluted air significantly affect central nervous system in children and adults and represent a significant risk factor for human health.

Operational evaluation of the RLINE dispersion model for studies of traffic-related air pollutants

NASA Astrophysics Data System (ADS)

Milando, Chad W.; Batterman, Stuart A.

2018-06-01

Exposure to traffic-related air pollutants (TRAP) remains a key public health issue, and improved exposure measures are needed to support health impact and epidemiologic studies and inform regulatory responses. The recently developed Research LINE source model (RLINE), a Gaussian line source dispersion model, has been used in several epidemiologic studies of TRAP exposure, but evaluations of RLINE's performance in such applications have been limited. This study provides an operational evaluation of RLINE in which predictions of NOx, CO and PM2.5 are compared to observations at air quality monitoring stations located near high traffic roads in Detroit, MI. For CO and NOx, model performance was best at sites close to major roads, during downwind conditions, during weekdays, and during certain seasons. For PM2.5, the ability to discern local and particularly the traffic-related portion was limited, a result of high background levels, the sparseness of the monitoring network, and large uncertainties for certain processes (e.g., formation of secondary aerosols) and non-mobile sources (e.g., area, fugitive). Overall, RLINE's performance in near-road environments suggests its usefulness for estimating spatially- and temporally-resolved exposures. The study highlights considerations relevant to health impact and epidemiologic applications, including the importance of selecting appropriate pollutants, using appropriate monitoring approaches, considering prevailing wind directions during study design, and accounting for uncertainty.

Cation Movements during Dehydration and NO2 Desorption in a Ba-Y,FAU zeolite: an in situ Time-resolved X-ray Diffraction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xianqin; Hanson, Jonathan C.; Kwak, Ja Hun

2013-02-28

Synchrotron-based in situ time-resolved X-ray diffraction and Rietveld analysis were used to probe the interactions between BaY, FAU zeolite frameworks and H2O or NO2 molecules. These results provided information about the migration of the Ba2+ cations in the zeolite framework during dehydration and during NO2 adsorption/desorption processes in a water free zeolite. In the hydrated structure water molecules form four double rings of hexagonal ice-like clusters [(H2O)6] in the 12-ring openings of the super-cage. These water rings interacted with the cations and the zeolite framework through four cation/water clusters centered over the four 6-membered rings of the super-cage (site II).more » Interpenetrating tetrahedral water clusters [(H2O)4] and tetrahedral Ba+2 cation clusters were observed in the sodalite cage. Consistent with the reported FT-IR results, three different ionic NOx species (NO+, NO+-NO2, and NO3-) were observed following NO2 adsorption by the dehydrated Ba-Y,FAU zeolite. The structure of the water and the NOx species were correlated with the interactions between the adsorbates, the cations, and the framework. The population of Ba2+ ions at different cationic positions strongly depended on the amount of bound water or NOx species. Both dehydration and NO2 adsorption/desorption resulted in facile migration of Ba2+ ions among the different cationic positions. Data obtained in this work have provided direct evidence for the Ba2+ cation migration to accommodate the binding of gas molecules. This important feature may play a pivotal role in the strong binding of NO2 to Ba-Y,FAU zeolite, a prerequisite for high catalytic activity in lean NOx reduction catalysis.« less

Hydrogen-powered flight

NASA Technical Reports Server (NTRS)

Smith, Timothy D.

2005-01-01

As the Nation moves towards a hydrogen economy the shape of aviation will change dramatically. To accommodate a switch to hydrogen the aircraft designs, propulsion, and power systems will look much different than the systems of today. Hydrogen will enable a number of new aircraft capabilities from high altitude long endurance remotely operated aircraft (HALE ROA) that will fly weeks to months without refueling to clean, zero emissions transport aircraft. Design and development of new hydrogen powered aircraft have a number of challenges which must be addressed before an operational system can become a reality. While the switch to hydrogen will be most outwardly noticeable in the aircraft designs of the future, other significant changes will be occurring in the environment. A switch to hydrogen for aircraft will completely eliminate harmful greenhouse gases such as carbon monoxide (CO), carbon dioxide (CO2), sulfur oxides (SOx), unburnt hydrocarbons and smoke. While these aircraft emissions are a small percentage of the amount produced on a daily basis, their placement in the upper atmosphere make them particularly harmful. Another troublesome gaseous emission from aircraft is nitrogen oxides (NOx) which contribute to ozone depletion in the upper atmosphere. Nitrogen oxide emissions are produced during the combustion process and are primarily a function of combustion temperature and residence time. The introduction of hydrogen to a gas turbine propulsion system will not eliminate NOx emissions; however the wide flammability range will make low NOx producing, lean burning systems feasible. A revolutionary approach to completely eliminating NOx would be to fly all electric aircraft powered by hydrogen air fuel cells. The fuel cells systems would only produce water, which could be captured on board or released in the lower altitudes. Currently fuel cell systems do not have sufficient energy densities for use in large aircraft, but the long term potential of eliminating greenhouse gas emissions makes it an intriguing and important field of research.

Electrochemical high-temperature gas sensors

NASA Astrophysics Data System (ADS)

Saruhan, B.; Stranzenbach, M.; Yüce, A.; Gönüllü, Y.

2012-06-01

Combustion produced common air pollutant, NOx associates with greenhouse effects. Its high temperature detection is essential for protection of nature. Component-integration capable high-temperature sensors enable the control of combustion products. The requirements are quantitative detection of total NOx and high selectivity at temperatures above 500°C. This study reports various approaches to detect NO and NO2 selectively under lean and humid conditions at temperatures from 300°C to 800°C. All tested electrochemical sensors were fabricated in planar design to enable componentintegration. We suggest first an impedance-metric gas sensor for total NOx-detection consisting of NiO- or NiCr2O4-SE and PYSZ-electrolyte. The electrolyte-layer is about 200μm thickness and constructed of quasi-single crystalline columns. The sensing-electrode (SE) is magnetron sputtered thin-layers of NiO or NiCr2O4. Sensor sensitivity for detection of total NOx has been measured by applying impedance analysis. The cross-sensitivity to other emission gases such as CO, CO2, CH4 and oxygen (5 vol.%) has been determined under 0-1000ppm NO. Sensor maintains its high sensitivity at temperatures up to 550°C and 600°C, depending on the sensing-electrode. NiO-SE yields better selectivity to NO in the presence of oxygen and have shorter response times comparing to NiCr2O4-SE. For higher temperature NO2-sensing capability, a resistive DC-sensor having Al-doped TiO2-sensing layers has been employed. Sensor-sensitivity towards NO2 and cross-sensitivity to CO has been determined in the presence of H2O at temperatures 600°C and 800°C. NO2 concentrations varying from 25 to 100ppm and CO concentrations from 25 to 75ppm can be detected. By nano-tubular structuring of TiO2, NO2 sensitivity of the sensor was increased.

Product Module Rig Test

NASA Technical Reports Server (NTRS)

Holdeman, James D. (Technical Monitor); Chiappetta, Louis, Jr.; Hautman, Donald J.; Ols, John T.; Padget, Frederick C., IV; Peschke, William O. T.; Shirley, John A.; Siskind, Kenneth S.

2004-01-01

The low emissions potential of a Rich-Quench-Lean (RQL) combustor for use in the High Speed Civil Transport (HSCT) application was evaluated as part of Work Breakdown Structure (WBS) 1.0.2.7 of the NASA Critical Propulsion Components (CPC) Program under Contract NAS3-27235. Combustion testing was conducted in cell 1E of the Jet Burner Test Stand at United Technologies Research Center. Specifically, a Rich-Quench-Lean combustor, utilizing reduced scale quench technology implemented in a quench vane concept in a product-like configuration (Product Module Rig), demonstrated the capability of achieving an emissions index of nitrogen oxides (NOx EI) of 8.5 gm/Kg fuel at the supersonic flight condition (relative to the program goal of 5 gm/Kg fuel). Developmental parametric testing of various quench vane configurations in the more fundamental flametube, Single Module Rig Configuration, demonstrated NOx EI as low as 5.2. All configurations in both the Product Module Rig configuration and the Single Module Rig configuration demonstrated exceptional efficiencies, greater than 99.95 percent, relative to the program goal of 99.9 percent efficiency at supersonic cruise conditions. Sensitivity of emissions to quench orifice design parameters were determined during the parametric quench vane test series in support of the design of the Product Module Rig configuration. For the rectangular quench orifices investigated, an aspect ratio (length/width) of approximately 2 was found to be near optimum. An optimum for orifice spacing was found to exist at approximately 0.167 inches, resulting in 24 orifices per side of a quench vane, for the 0.435 inch quench zone channel height investigated in the Single Module Rig. Smaller quench zone channel heights appeared to be beneficial in reducing emissions. Measurements were also obtained in the Single Module Rig configuration on the sensitivity of emissions to the critical combustor parameters of fuel/air ratio, pressure drop, and residence time. Minimal sensitivity was observed for all of these parameters.

Experimental and Computational Study of Trapped Vortex Combustor Sector Rig With Tri-Pass Diffuser

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Shouse, D. T.; Roquernore, W. M.; Burrus, D. L.; Duncan, B. S.; Ryder, R. C.; Brankovic, A.; Liu, N.-S.; Gallagher, J. R.; Hendricks, J. A.

2004-01-01

The Trapped Vortex Combustor (TVC) potentially offers numerous operational advantages over current production gas turbine engine combustors. These include lower weight, lower pollutant emissions, effective flame stabilization, high combustion efficiency, excellent high altitude relight capability, and operation in the lean burn or RQL modes of combustion. The present work describes the operational principles of the TVC, and extends diffuser velocities toward choked flow and provides system performance data. Performance data include EINOx results for various fuel-air ratios and combustor residence times, combustion efficiency as a function of combustor residence time, and combustor lean blow-out (LBO) performance. Computational fluid dynamics (CFD) simulations using liquid spray droplet evaporation and combustion modeling are performed and related to flow structures observed in photographs of the combustor. The CFD results are used to understand the aerodynamics and combustion features under different fueling conditions. Performance data acquired to date are favorable compared to conventional gas turbine combustors. Further testing over a wider range of fuel-air ratios, fuel flow splits, and pressure ratios is in progress to explore the TVC performance. In addition, alternate configurations for the upstream pressure feed, including bi-pass diffusion schemes, as well as variations on the fuel injection patterns, are currently in test and evaluation phases.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulyshen, Michael D.; Hanula, James L.; Horn, Scott

Pitfall traps provide an easy and inexpensive way to sample ground-dwelling arthropods (Spence and Niemela 1994; Spence et al. 1997; Abildsnes and Tommeras 2000) and have been used exclusively in many studies of the abundance and diversity of ground beetles (Coleoptera: Carabidae). Despite the popularity of this trapping technique, pitfall traps have many disadvantages. For example, they often fail to collect both small (Spence and Niemela 1994) and trap-shy species (Benest 1989), eventually deplete the local carabid population (Digweed et al. 1995), require a species to be ground-dwelling in order to be captured (Liebherr and Mahar 1979), and produce differentmore » results depending on trap diameter and material, type of preservative used, and trap placement (Greenslade 1964; Luff 1975; Work et al. 2002). Further complications arise from seasonal patterns of movement among the beetles themselves (Maelfait and Desender 1990), as well as numerous climatic factors, differences in plant cover, and variable surface conditions (Adis 1979). Because of these limitations, pitfall trap data give an incomplete picture of the carabid community and should be interpreted carefully. Additional methods, such as use of Berlese funnels and litter washing (Spence and Niemela 1994), collection from lights (Usis and MacLean 1998), and deployment of flight intercept devices (Liebherr and Mahar 1979; Paarmann and Stork 1987), should be incorporated in surveys to better ascertain the species composition and relative numbers of ground beetles. Flight intercept devices, like pitfall traps, have the advantage of being easy to use and replicate, but their value to carabid surveys is largely unknown. Here we demonstrate the effectiveness of Malaise traps for sampling ground beetles in a bottomland hardwood forest.« less

Identification of combustion intermediates in low-pressure premixed pyridine/oxygen/argon flames.

PubMed

Tian, Zhenyu; Li, Yuyang; Zhang, Taichang; Zhu, Aiguo; Qi, Fei

2008-12-25

Combustion intermediates of two low-pressure premixed pyridine/oxygen flames with respective equivalence ratios of 0.56 (C/O/N = 1:4.83:0.20) and 2.10 (C/O/N = 1:1.29:0.20) have been identified with tunable synchrotron vacuum ultraviolet (VUV) photoionization and molecular-beam mass spectrometry techniques. About 80 intermediates in the rich flame and 60 intermediates in the lean flame, including nitrogenous, oxygenated, and hydrocarbon intermediates, have been identified by measurements of photoionization mass spectra and photoionization efficiency spectra. Some radicals and new nitrogenous intermediates are identified in the present work. The experimental results are useful for studying the conversion of volatile nitrogen compounds and understanding the formation mechanism of NO(x) in flames of nitrogenous fuels.

Premix fuels study applicable to duct burner conditions for a variable cycle engine

NASA Technical Reports Server (NTRS)

Venkataramani, K. S.

1978-01-01

Emission levels and performance of a premixing Jet-A/air duct burner were measured at reference conditions representative of take-off and cruise for a variable cycle engine. In a parametric variation sequence of tests, data were obtained at inlet temperatures of 400, 500 and 600K at equivalence ratios varying from 0.9 to the lean stability limit. Ignition was achieved at all the reference conditions although the CO levels were very high. Significant nonuniformity across the combustor was observed for the emissions at the take-off condition. At a reference Mach number of 0.117 and an inlet temperature of 600K, corresponding to a simulated cruise condition, the NOx emission level was approximately 1 gm/kg-fuel.

Experimental study of the effects of secondary air on the emissions and stability of a lean premixed combustor

NASA Technical Reports Server (NTRS)

Roffe, G.; Raman, R. S. V.; Marek, C. J.

1982-01-01

A study of the effects of secondary air addition on the stability and emissions of a gas turbine combustor has been performed. Tests were conducted with two types of flameholders and varying amounts of dilution air addition. Results indicate that NO(x) decreases with increasing dilution air injection, whereas CO is independent of the amount of dilution air and is related to the gas temperature near the walls. The axial location of the dilution air addition has no effect on the performance or stability. Results also indicate that the amount of secondary air entrained by the flameholder recirculation zone is dependent on the amount of dilution air and flameholder geometry.

Atomization and Dispersion of a Liquid Jet Injected Into a Crossflow of Air

NASA Technical Reports Server (NTRS)

Seay, J. E.; Samuelson, G. S.

1996-01-01

In recent years, environmental regulations have become more stringent, requiring lower emissions of mainly nitrogen oxides (NOx), as well as carbon monoxide (CO) and unburned hydrocarbons (UHC). These regulations have forced the gas turbine industry to examine non-conventional combustion strategies, such as the lean burn approach. The reasoning behind operating under lean conditions is to maintain the temperature of combustion near and below temperatures required for the formation of thermal nitric oxide (NO). To be successful, however, the lean processes require careful preparation of the fuel/air mixture to preclude formation of either locally rich reaction zones, which may give rise to NO formation, or locally lean reaction zones, which may give rise to inefficient fuel processing. As a result fuel preparation is crucial to the development and success of new aeroengine combustor technologies. A key element of the fuel preparation process is the fuel nozzle. As nozzle technologies have developed, airblast atomization has been adopted for both industrial and aircraft gas turbine applications. However, the majority of the work to date has focused on prefilming nozzles, which despite their complexity and high cost have become an industry standard for conventional combustion strategies. It is likely that the new strategies required to meet future emissions goals will utilize novel fuel injector approaches, such as radial injection. This thesis proposes and demonstrates an experiment to examine, on a mechanistic level (i.e., the physics of the action), the processes associated with the atomization, evaporation, and dispersion of a liquid jet introduced, from a radial, plain-jet airblast injector, into a crossflow of air. This understanding requires the knowledge not only of what factors influence atomization, but also the underlying mechanism associated with liquid breakup and dispersion. The experimental data acquired identify conditions and geometries for improved performance of radial airblast injectors.

Using malaise traps to sample ground beetles (Coleoptera: Carabidae).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulyshen, Michael D., James L. Hanula, and Scott Horn

2005-01-01

Pitfall traps provide an easy and inexpensive way to sample ground-dwelling arthropods (Spence and Niemela 1994; Spence et al. 1997; Abildsnes and Tommeras 2000) and have been used exclusively in many studies of the abundance and diversity of ground beetles (Coleoptera: Carabidae). Despite the popularity of this trapping technique, pitfall traps have many disadvantages. For example, they often fail to collect both small (Spence and Niemela 1994) and trap-shy species (Benest 1989), eventually deplete the local carabid population (Digweed et al. 1995), require a species to be ground-dwelling in order to be captured (Liebherr and Mahar 1979), and produce differentmore » results depending on trap diameter and material, type of preservative used, and trap placement (Greenslade 1964; Luff 1975; Work et al. 2002). Further complications arise from seasonal patterns of movement among the beetles themselves (Maelfait and Desender 1990), as well as numerous climatic factors, differences in plant cover, and variable surface conditions (Adis 1979). Because of these limitations, pitfall trap data give an incomplete picture of the carabid community and should be interpreted carefully. Additional methods, such as use of Berlese funnels and litter washing (Spence and Niemela 1994), collection from lights (Usis and MacLean 1998), and deployment of flight intercept devices (Liebherr and Mahar 1979; Paarmann and Stork 1987), should be incorporated in surveys to better ascertain the species composition and relative numbers of ground beetles. Flight intercept devices, like pitfall traps, have the advantage of being easy to use and replicate, but their value to carabid surveys is largely unknown. Here we demonstrate the effectiveness of Malaise traps for sampling ground beetles in a bottomland hardwood forest.« less

Switching Oxide Traps

NASA Technical Reports Server (NTRS)

Oldham, Timothy R.

2003-01-01

We consider radiation-induced charge trapping in SiO2 dielectric layers, primarily from the point of view of CMOS devices. However, SiO2 insulators are used in many other ways, and the same defects occur in other contexts. The key studies, which determined the nature of the oxide charge traps, were done primarily on gate oxides in CMOS devices, because that was the main radiation problem in CMOS at one time. There are two major reviews of radiation-induced oxide charge trapping already in the literature, which discuss the subject in far greater detail than is possible here. The first of these was by McLean et al. in 1989, and the second, ten years later, was intended as an update, because of additional, new work that had been reported. Basically, the picture that has emerged is that ionizing radiation creates electron-hole pairs in the oxide, and the electrons have much higher mobility than the holes. Therefore, the electrons are swept out of the oxide very rapidly by any field that is present, leaving behind any holes that escape the initial recombination process. These holes then undergo a polaron hopping transport toward the Si/SiO2 interface (under positive bias). Near the interface, some fraction of them fall into deep, relatively stable, long-lived hole traps. The nature and annealing behavior of these hole traps is the main focus of this paper.

Regulating NETosis: Increasing pH Promotes NADPH Oxidase-Dependent NETosis

PubMed Central

Khan, Meraj A.; Philip, Lijy M.; Cheung, Guillaume; Vadakepeedika, Shawn; Grasemann, Hartmut; Sweezey, Neil; Palaniyar, Nades

2018-01-01

Neutrophils migrating from the blood (pH 7.35–7.45) into the surrounding tissues encounter changes in extracellular pH (pHe) conditions. Upon activation of NADPH oxidase 2 (Nox), neutrophils generate large amounts of H+ ions reducing the intracellular pH (pHi). Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET) formation (NETosis) is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS) and neutrophil protease activity, stimulating NETosis. Here, we found that raising pHe (ranging from 6.6 to 7.8; every 0.2 units) increased pHi of both activated and resting neutrophils within 10–20 min (Seminaphtharhodafluor dual fluorescence measurements). Since Nox activity generates H+ ions, pHi is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging) during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs). In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots) and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative)-, and Staphylococcus aureus (Gram-positive)-induced NETosis. Thus, higher pHe promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pHe-mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM) increases NETosis. Each Tris molecule can bind 3H+ ions, whereas each bicarbonate HCO3− ion binds 1H+ ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar bicarbonate solution. For that reason, regulating NETosis by pH with specific buffers such as THAM could be more effective than bicarbonate in managing NET-related diseases. PMID:29487850

Regulating NETosis: Increasing pH Promotes NADPH Oxidase-Dependent NETosis.

PubMed

Khan, Meraj A; Philip, Lijy M; Cheung, Guillaume; Vadakepeedika, Shawn; Grasemann, Hartmut; Sweezey, Neil; Palaniyar, Nades

2018-01-01

Neutrophils migrating from the blood (pH 7.35-7.45) into the surrounding tissues encounter changes in extracellular pH (pH e ) conditions. Upon activation of NADPH oxidase 2 (Nox), neutrophils generate large amounts of H + ions reducing the intracellular pH (pH i ). Nevertheless, how extracellular pH regulates neutrophil extracellular trap (NET) formation (NETosis) is not clearly established. We hypothesized that increasing pH increases Nox-mediated production of reactive oxygen species (ROS) and neutrophil protease activity, stimulating NETosis. Here, we found that raising pH e (ranging from 6.6 to 7.8; every 0.2 units) increased pH i of both activated and resting neutrophils within 10-20 min (Seminaphtharhodafluor dual fluorescence measurements). Since Nox activity generates H + ions, pH i is lower in neutrophils that are activated compared to resting. We also found that higher pH stimulated Nox-dependent ROS production (R123 generation; flow cytometry, plate reader assay, and imaging) during spontaneous and phorbol myristate acetate-induced NETosis (Sytox Green assays, immunoconfocal microscopy, and quantifying NETs). In neutrophils that are activated and not resting, higher pH stimulated histone H4 cleavage (Western blots) and NETosis. Raising pH increased Escherichia coli lipopolysaccharide-, Pseudomonas aeruginosa (Gram-negative)-, and Staphylococcus aureus (Gram-positive)-induced NETosis. Thus, higher pH e promoted Nox-dependent ROS production, protease activity, and NETosis; lower pH has the opposite effect. These studies provided mechanistic steps of pH e -mediated regulation of Nox-dependent NETosis. Raising pH either by sodium bicarbonate or Tris base (clinically known as Tris hydroxymethyl aminomethane, tromethamine, or THAM) increases NETosis. Each Tris molecule can bind 3H + ions, whereas each bicarbonate HCO3 - ion binds 1H + ion. Therefore, the amount of Tris solution required to cause the same increase in pH level is less than that of equimolar bicarbonate solution. For that reason, regulating NETosis by pH with specific buffers such as THAM could be more effective than bicarbonate in managing NET-related diseases.

Experimental investigation of aerodynamics, combustion, and emissions characteristics within the primary zone of a gas turbine combustor

NASA Astrophysics Data System (ADS)

Elkady, Ahmed M.

2006-04-01

The present work investigates pollutant emissions production, mainly nitric oxides and carbon monoxide, within the primary zone of a highly swirling combustion and methods with which to reduce their formation. A baseline study was executed at different equivalence ratios and different inlet air temperatures. The study was then extended to investigate the effects of utilizing transverse air jets on pollutant emission characteristics at different jet locations, jet mass ratio, and overall equivalence ratio as well as to investigate the jets' overall interactions with the recirculation zone. A Fourier Transform Infrared (FTIR) spectrometer was employed to measure emissions concentrations generated during combustion of Jet-A fuel in a swirl-cup assembly. Laser Doppler Velocimetry (LDV) was employed to investigate the mean flow aerodynamics within the combustor. Particle Image Velocimetry (PIV) was utilized to capture the instantaneous aerodynamic behavior of the non-reacting primary zone. Results illustrate that NOx production is a function of both the recirculation zone and the flame length. At low overall equivalence ratios, the recirculation zone is found to be the main producer of NOx. At near stoichiometric conditions, the post recirculation zone appears to be responsible for the majority of NOx produced. Results reveal the possibility of injecting air into the recirculation zone without altering flame stability to improve emission characteristics. Depending on the jet location and strength, nitric oxides as well as carbon monoxide can be reduced simultaneously. Placing the primary air jet just downstream of the fuel rich recirculation zone can lead to a significant reduction in both nitric oxides and carbon monoxide. In the case of fuel lean recirculation zone, reduction of nitric oxides can occur by placing the jets below the location of maximum radius of the recirculation zone.

Effects of Spent Cooling and Swirler Angle on a 9-Point Swirl-Venturi Injector

NASA Technical Reports Server (NTRS)

He, Zhuohui J.; Tacina, Kathleen M.; Lee, Chi-Ming; Tacina, Robert R.; Lee, Phil

2014-01-01

This paper presents multipoint Lean-Direct-Injection (LDI) emissions results for flame tube combustion tests at an inlet pressure of 1034 kPa and inlet temperatures between 835 and 865 K; these are the combustor inlet conditions that the High Speed Research (HSR) program used for supersonic cruise. It focuses on one class of LDI geometry, 9-point swirl-venturi LDI (SV-LDI). Two parameters are compared in this paper: the use of dome cooling air and the swirler blade angle. Dome cooling air is called "spent cooling" and is at combustor inlet conditions. Three cooling variations are studied: cooling at the venturi throat, cooling at the dome face, and no cooling at all. Two swirler blade angles are studied: 45deg and 60deg. The HSR 9-point SV-LDI emissions are also compared to a similar 9-point SV-LDI design which was used in the later ultra-efficient engine technology (UEET) program. The HSR and UEET designs cannot be compared directly due to different UEET combustor conditions. Therefore, this paper uses previously published UEET correlation equations to make comparisons. Results show that using a 45deg swirler produces lower NOx emissions than using a 60deg swirler. This is consistent with the later UEET results. The effects of spent cooling depend on swirler angle, spent cooling location, and the test conditions. For the configuration with 45deg swirlers, spent cooling delivers lower NOx emissions when it is injected at the throat. For the 60deg swirler, spent cooling does not have much effect on NOx emissions. These results might be caused by the location and the intensity of the flame recirculation zone.

Effects of Spent Cooling and Swirler Angle on a 9-point Swirl-Venturi Injector

NASA Technical Reports Server (NTRS)

He, ZH., Joe; Tacina, Kathleen M.; Lee, Chi-Ming; Tacina, Robert R.; Lee, Phil

2013-01-01

This paper presents multipoint lean-direct-injection (LDI) emissions results for flame tube combustion tests at an inlet pressure of 1034 kPa and inlet temperatures between 835 and 865 K; these are the combustor inlet conditions that the High Speed Research (HSR) program used for supersonic cruise. It focuses on one class of LDI geometry, 9-point swirl-venturi LDI (SV-LDI). Two parameters are compared in this paper: the use of dome cooling air and the swirler blade angle. Dome cooling air is called 'spent cooling' and is at combustor inlet conditions. Three cooling variations are studied: cooling at the venturi throat, cooling at the dome face, and no cooling at all. Two swirler blade angles are studied: 45 deg and 60 deg. The HSR 9-point SV-LDI emissions are also compared to a similar 9-point SV-LDI design which was used in the later ultra-efficient engine technology (UEET) program. The HSR and UEET designs cannot be compared directly due to different UEET combustor conditions. Therefore, this paper uses previously published UEET correlation equations to make comparisons. Results show that using a 45 deg swirler produces lower NOx emissions than using a 60 deg swirler. This is consistent with the later UEET results. The effects of spent cooling depend on swirler angle, spent cooling location, and the test conditions. For the configuration with 45 deg swirlers, spent cooling delivers lower NOx emissions when it is injected at the throat. For the 60 deg swirler, spent cooling does not have much effect on NOx emissions. These results might be caused by the location and the intensity of the flame recirculation zone.

Experiments on Nitrogen Oxide Production of Droplet Arrays Burning under Microgravity Conditions

NASA Astrophysics Data System (ADS)

Moesl, Klaus; Sattelmayer, Thomas; Kikuchi, Masao; Yamamoto, Shin; Yoda, Shinichi

The optimization of the combustion process is top priority in current aero-engine and aircraft development, particularly from the perspectives of high efficiency, minimized fuel consumption, and a sustainable exhaust gas production. Aero-engines are exclusively liquid-fueled with a strong correlation between the combustion temperature and the emissions of nitric oxide (NOX ). Due to safety concerns, the progress in NOX reduction has been much slower than in stationary gas turbines. In the past, the mixing intensity in the primary zone of aero-engine combustors was improved and air staging implemented. An important question for future aero-engine combustors, consequently, is how partial vaporization influences the NOX emissions of spray flames? In order to address this question, the combustion of partially vaporized, linear droplet arrays was studied experimentally under microgravity conditions. The influence of fuel pre-vaporization on the NOX emissions was assessed in a wide range. The experiments were performed in a drop tower and a sounding rocket campaign. The microgravity environment provided ideal experiment conditions without the disturbing ef-fect of natural convection. This allowed the study of the interacting phenomena of multi-phase flow, thermodynamics, and chemical kinetics. This way the understanding of the physical and chemical processes related to droplet and spray combustion could be improved. The Bremen drop tower (ZARM) was utilized for the precursor campaign in July 2008, which was com-prised of 30 drops. The sounding rocket experiments, which totaled a microgravity duration of 6 minutes, were finally performed on the flight of TEXUS-46 in November 2009. On both campaigns the "Japanese Combustion Module" (JCM) was used. It is a cooperative experi-ment on droplet array combustion between the Japan Aerospace Exploration Agency (JAXA) and ESA's (European Space Agency) research team, working on the combustion properties of partially premixed sprays. One droplet array consisted of five droplets (for sounding rocket) and 9 -17 droplets (for drop tower) of the hydrocarbon n-decane (C10 H22 ). While keeping the pressure at 1.0 bar (+/-20 mbar), the combustion chamber temperature and the fuel vaporization time were varied in the range of 300 -500 K and 0.5 -18 s, respectively. Consequently, the total amount of fuel, the local equivalence ratio Φ along the droplet array, and the dimensionless droplet spacing S/d0 , with d0 being the initial droplet diameter, were adapted. Ignition was initiated by a hot-wire igniter from one end of the droplet array. Representative gas samples were collected from every single combustion sequence after flame extinction and stored in specially treated gas sampling cylinders for their succeeding analysis on ground. Visual observation of the combustion process, as well as temperature and pressure logging, supported the scientific interpretation of the gas analysis. With an increase of the preheating temperature, NOX emissions increase due to a higher effec-tive flame temperatures. However, with an increasing pre-vaporization, NOX emissions become lower due to the dropping number and the dropping size of burning droplets, acting as hot spots. A correction for the effect of the preheating temperature was developed. It reveals the effect of pre-vaporization and shows that the NOX emissions are almost independent of it for near-stoichiometric operation. At overall lean conditions the NOX emissions drop non-linearly with the degree of vaporization. Up to now, this leads to the conclusion that a high degree of vaporization is required in order to achieve substantial NOX abatement.

NASA 9-Point LDI Code Validation Experiment

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Anderson, Robert C.; Locke, Randy J.

2007-01-01

This presentation highlights the experimental work to date to obtain validation data using a 9-point lean direct injector (LDI) in support of the National Combustion Code. The LDI is designed to supply fuel lean, Jet-A and air directly into the combustor such that the liquid fuel atomizes and mixes rapidly to produce short flame zones and produce low levels of oxides of nitrogen and CO. We present NOx and CO emission results from gas sample data that support that aspect of the design concept. We describe this injector and show high speed movies of selected operating points. We present image-based species maps of OH, fuel, CH and NO obtained using planar laser induced fluorescence and chemiluminescence. We also present preliminary 2-component, axial and vertical, velocity vectors of the air flow obtained using particle image velocimetry and of the fuel drops in a combusting case. For the same combusting case, we show preliminary 3-component velocity vectors obtained using a phase Doppler anemometer. For the fueled, combusting cases especially, we found optical density is a technical concern that must be addressed, but that in general, these preliminary results are promising. All optical-based results confirm that this injector produces short flames, typically on the order of 5- to-7-mm long at typical cruise and high power engine cycle conditions.

Diesel Combustion and Emission Using High Boost and High Injection Pressure in a Single Cylinder Engine

NASA Astrophysics Data System (ADS)

Aoyagi, Yuzo; Kunishima, Eiji; Asaumi, Yasuo; Aihara, Yoshiaki; Odaka, Matsuo; Goto, Yuichi

Heavy-duty diesel engines have adopted numerous technologies for clean emissions and low fuel consumption. Some are direct fuel injection combined with high injection pressure and adequate in-cylinder air motion, turbo-intercooler systems, and strong steel pistons. Using these technologies, diesel engines have achieved an extremely low CO2 emission as a prime mover. However, heavy-duty diesel engines with even lower NOx and PM emission levels are anticipated. This study achieved high-boost and lean diesel combustion using a single cylinder engine that provides good engine performance and clean exhaust emission. The experiment was done under conditions of intake air quantity up to five times that of a naturally aspirated (NA) engine and 200MPa injection pressure. The adopted pressure booster is an external supercharger that can control intake air temperature. In this engine, the maximum cylinder pressure was increased and new technologies were adopted, including a monotherm piston for endurance of Pmax =30MPa. Moreover, every engine part is newly designed. As the boost pressure increases, the rate of heat release resembles the injection rate and becomes sharper. The combustion and brake thermal efficiency are improved. This high boost and lean diesel combustion creates little smoke; ISCO and ISTHC without the ISNOx increase. It also yields good thermal efficiency.

NO.sub.x catalyst and method of suppressing sulfate formation in an exhaust purification system

DOEpatents

Balmer-Millar, Mari Lou [Chillicothe, IL; Park, Paul W [Peoria, IL; Panov, Alexander G [Peoria, IL

2007-06-26

The activity and durability of a zeolite lean-burn NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NO.sub.x catalyst. The NO.sub.x catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.

NO.sub.x catalyst and method of suppressing sulfate formation in an exhaust purification system

DOEpatents

Balmer-Millar, Mari Lou; Park, Paul W.; Panov, Alexander G.

2006-08-22

The activity and durability of a zeolite lean-bum NOx catalyst can be increased by loading metal cations on the outer surface of the zeolite. However, the metal loadings can also oxidize sulfur dioxide to cause sulfate formation in the exhaust. The present invention is a method of suppressing sulfate formation in an exhaust purification system including a NO.sub.x catalyst. The NO.sub.x catalyst includes a zeolite loaded with at least one metal. The metal is selected from among an alkali metal, an alkaline earth metal, a lanthanide metal, a noble metal, and a transition metal. In order to suppress sulfate formation, at least a portion of the loaded metal is complexed with at least one of sulfate, phosphate, and carbonate.

Ammonia reactions with the stored oxygen in a commercial lean NO x trap catalyst

DOE PAGES

Bartova, Sarka; Mracek, David; Koci, Petr; ...

2014-10-12

Ammonia is an important intermediate of the NO x reduction in a NO x storage and reduction catalyst (aka lean NO x trap). NH 3 formed under rich conditions in the reduced front part of the catalyst is transported by convection downstream to the unregenerated (still oxidized) zone of the catalyst, where it further reacts with the stored oxygen and NO x. In this paper, the kinetics and selectivity of NH 3 reactions with the stored oxygen are studied in detail with a commercial Ba-based NO x storage catalyst containing platinum group metals (PGM), Ba and Ce oxides. Furthermore, steady-statemore » NH 3 decomposition, NH 3 oxidation by O 2 and NO, and N 2O decomposition are examined in light-off experiments. Periodic lean/rich cycling is measured first with O 2 and NH 3, and then with NO x + O 2 and NH 3 to discriminate between the NH 3 reactions with the stored oxygen and the stored NO x. The reaction of NH 3 with the stored O 2 is highly selective towards N 2, however a certain amount of NO x and N 2O is also formed. The formed NO x by-product is efficiently adsorbed on the NO x storage sites such that the NO x is not detected at the reactor outlet except at high temperatures. The stored NO x reacts with NH 3 feed in the next rich phase, contributing to the N 2O formation. Water inhibits the reactions of NH 3 with the stored oxygen. On the contrary, the presence of CO 2 increases the NH 3 consumption. Furthermore, CO 2 is able to provide additional oxygen for NH 3 oxidation, forming –CO in analogy to the reverse water gas shift reaction.« less

Flame stabilization and mixing characteristics in a Stagnation Point Reverse Flow combustor

NASA Astrophysics Data System (ADS)

Bobba, Mohan K.

A novel combustor design, referred to as the Stagnation Point Reverse-Flow (SPRF) combustor, was recently developed that is able to operate stably at very lean fuel-air mixtures and with low NOx emissions even when the fuel and air are not premixed before entering the combustor. The primary objective of this work is to elucidate the underlying physics behind the excellent stability and emissions performance of the SPRF combustor. The approach is to experimentally characterize velocities, species mixing, heat release and flame structure in an atmospheric pressure SPRF combustor with the help of various optical diagnostic techniques: OH PLIF, chemiluminescence imaging, PIV and Spontaneous Raman Scattering. Results indicate that the combustor is primarily stabilized in a region downstream of the injector that is characterized by low average velocities and high turbulence levels; this is also the region where most of the heat release occurs. High turbulence levels in the shear layer lead to increased product entrainment levels, elevating the reaction rates and thereby enhancing the combustor stability. The effect of product entrainment on chemical timescales and the flame structure is illustrated with simple reactor models. Although reactants are found to burn in a highly preheated (1300 K) and turbulent environment due to mixing with hot product gases, the residence times are sufficiently long compared to the ignition timescales such that the reactants do not autoignite. Turbulent flame structure analysis indicates that the flame is primarily in the thin reaction zones regime throughout the combustor, and it tends to become more flamelet like with increasing distance from the injector. Fuel-air mixing measurements in case of non-premixed operation indicate that the fuel is shielded from hot products until it is fully mixed with air, providing nearly premixed performance without the safety issues associated with premixing. The reduction in NOx emissions in the SPRF combustor are primarily due to its ability to stably operate under ultra lean (and nearly premixed) condition within the combustor. Further, to extend the usefulness of this combustor configuration to various applications, combustor geometry scaling rules were developed with the help of simplified coaxial and opposed jet models.

Kinetic and spectroscopic study of catalysts for water-gas shift and nitrogen oxide removal

NASA Astrophysics Data System (ADS)

Kispersky, Vincent Frederick

Nitrogen oxides (NOx) are formed in high temperature combustion processes such as in power generation and motor vehicles. Increasingly stringent regulation of these harmful emissions continues to drive interest in developing, understanding and studying new catalytic formulations for exhaust aftertreatment. For mobile sources, predominantly heavy duty diesel engines, selective catalytic reduction (SCR) with NH3 has become the principal means of NO x abatement. An alternative technology developed, but now surpassed by SCR, is NOx Storage Reduction (NSR) catalysis. Both technologies have been studied in our laboratory and are the basis for this dissertation. We studied seven different lean NOx trap (LNT) monolith formulations for NSR ranging from 0.6 to 6.2 wt.% Pt and 4 to 20 wt.% Ba loadings on γ-Al 2O3. The noble metal component of a LNT oxidizes NO to NO 2 aiding in the storage of NO2 on the alkaline earth component. Before the storage component saturates, a reductant such as H2 is introduced into the vehicular exhaust and the stored NOx is released and reduced to N2. Once the storage component is free of NOx, reductant flow is ceased and storage is begun anew. Our research focused on understanding the effects that CO2 and H2O have on the storage capacity of the LNT over short as well as extended periods of time. We found that for high Ba loadings, CO 2 had a consistently detrimental effect on the fast NOx storage capacity (NSC), defined as the amount of NOx the catalyst can store before 1% of the inlet NOx is measured in the reactor outlet. Over long NOx storage periods, CO2 continued to inhibit storage compared to the same catalyst in CO2 free conditions. On low loadings of Ba, however, the inhibition of CO2 was significantly reduced. We found that the loading dependent characteristics of the Ba phase affected the way in which CO2 adsorbed on the storage component, which greatly affected the stability of the species on lower Ba loadings. The less stable adsorbed CO2 proved less competitive for NOx sorption sites, explaining the weak reduction of NSC by CO2 on low Ba loadings. Contrary to CO2, H2O exhibited both beneficial and inhibitory effects on the NSC. Over long periods of time, and at high Ba loadings, the addition of H2O in the feed increased the NSC, attributed to enhanced O2 spillover on the hydroxylated Ba surface allowing greater access to available NOx storage sites. When the Ba loading was reduced, the interaction sphere of Pt particles with the Ba storage component required for O2 to spillover to assist in NOx storage was reduced. Thus, despite the enhanced spillover capacity of oxygen on the hydroxylated storage component other NSC decreasing effects of H2O addition, such as Ba agglomeration, became more dominant and reduced the NSC. Recent developments in selective catalytic reduction have shown Cu and Fe/chabazite (CHA) based zeolites to be particularly well suited to sustaining high catalytic rates without degradation in the harsh environment of diesel engine exhaust. Little has been published about these catalysts as the academic community has just recently learned about the materials and their commercial implementation. Using operando X-ray absorption spectroscopy, combined with first-principles thermodynamics simulations and kinetic analysis, we have studied the nature of the Cu active site on Cu/SSZ-13, Cu/SAPO-34 and Cu/ZSM-5. Examining the catalysts under operando standard SCR conditions (300 ppm NO, 300 ppm NH3, 5% O2, 5% H2O and 5% CO2) showed the catalyst to be in a mixed Cu(I)-Cu(II) oxidation state. Neither the amount of Cu(I) nor Cu(II) individually correlated with the different rates measured on the various zeolite catalysts, and so we proposed that the SCR reaction progresses via a redox mechanism requiring both Cu(I) and Cu(II). First principles thermodynamic calculations found that the redox couple of Cu(I)H2O and Cu(II)(OH)2 were the most thermodynamically stable species of any of the OxHy variants modeled on Cu. The redox nature of the Cu active site was further investigated in a follow up study isolating the reducing portion of the SCR by removing O 2 from the reaction feed. Cutting off O2 drove the catalyst into a highly reduced state dominated by Cu(I) while removing a reductant drove the Cu into the fully oxidized state. Our research shows that not only is redox a vital part of the SCR reaction on Cu/zeolites, but that the oxidation state of the active site is highly sensitive to the gas environment. The water-gas shift (WGS) reaction is an industrially important step in H2 generation from steam reforming. I have had the opportunity to contribute to a number of studies in WGS by studying the catalysts in FTIR. We studied numerous catalytic formulations including Fe promoted Pd/Al 2O3 and Au/TiO2. We found that the Fe promoted the WGS rate of the catalyst by a factor of 160 compared to the Fe free Pd/Al 2O3. The reduced Fe promoter efficiently split H2O, typically the role performed by reducible supports, and the nearby noble metal particles provided spillover H2 to maintain the reduced Fe phase necessary to split H2O. Our study of Au/TiO2 involved the development of a modified operando transmission IR cell with ultra-low dead volume allowing for fast switching isotope experiments over the catalyst. The isotope switching experiments showed that only CO adsorbed on Au0 sites was an active surface intermediate at 120°C. Counting the amount of active surface Au atoms for the reaction ruled out the Au particle surface and perimeter atoms as the dominant active sites and confirmed our previous finding that the active site was composed mostly of low coordinated corner Au atoms.

FreedomCAR - Aftertreatment Subsystem Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lisa A. Prentiss

2005-09-30

The primary objective of this program was to develop generic aftertreatment technologies applicable for LDV and LDT engines ranging from 55 kW to 200kW, to develop an optimized and integrated aftertreatment system for a LDT (Light Duty Truck) type vehicle, and to demonstrate the technology which will enable light duty diesel engines to meet Federal Tier II regulation with minimum impact on fuel economy. Specifically, the development targets for emissions reduction and fuel injection penalty are given below: (1) NOx conversion efficiency > 90% (hot), > 84% (combined); (2) PM conversion efficiency > 90% (hot), > 84% (combined); (3) Fuelmore » penalty over FTP-75 Less than 5%; and (4) Fuel penalty at Cruise condition Less than 3%. Development of cost-effective, highly efficient diesel exhaust aftertreatment systems in combination with very low engine out emission combustion development are essential elements for realization of Federal Tier II emission standards for Light Duty Trucks and Vehicles. Evaluation of several aftertreatment technologies was completed as part of this program. A combination of Diesel Oxidation Catalyst, NOx Adsorbing Catalyst and Catalyzed Soot Filter was found to provide the levels of conversion efficiency required to achieve the emission targets. While early systems required relatively large catalyst volumes, external dosing, sulfur traps, full bypass configurations and high levels of Platinum metals; the final system is a compact, scalable, flow-through, fully-integrated and engine-managed aftertreatment system capable of commercial application for Light Duty Vehicles and Trucks. NOx adsorber/particulate filter technology is particularly attractive for Light Duty applications due to the lower exhaust flow and temperature requirements as compared to Heavy Duty engines. Despite these strong positive aspects, NOx Adsorbers are challenged by their regeneration requirements and susceptibility to sulfur poisoning and thermal degradation. Capability was developed to regenerate the NOx Adsorber for NOx and SOx as well as the Particulate Filter for soot. This system was fully integrated into a truck and evaluated over the chassis dynamometer for emissions capability and in real-world winter field testing. Durability of the system was evaluated over a variety of accelerated and real-time dynamometer tests. Excellent NOx and PM conversion efficiency was demonstrated, even following 3000 hrs of endurance testing. Unregulated emissions emitted by the system were evaluated as was the fuel penalty associated with the DeNOx and DeSOx regeneration processes. In the final evaluation, the system demonstrated 90% NOx conversion and 99% PM conversion at a 6% fuel penalty over the FTP-75 test cycle. While target fuel penalty levels were demonstrated using full-bypass configuration systems, the cost associated with those systems was prohibitively high and would preclude successful commercialization of the technology. Although the flow-through configuration fell 1% short of the 5% fuel penalty target, the cost of this configuration is such that commercial application is feasible. Cost drivers for the final system configuration were identified and demonstrate areas where future development areas could focus.« less

Advanced materials for automobiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Narula, C.K.; Allison, J.E.; Bauer, D.R.

Quite early on, manufacturers realized that lighter automobiles (with gas and diesel engines) would be more fuel efficient and produce fewer tailpipe emissions. They also realized that burning diesel fuel at elevated temperatures (1,315 C) would result in similar improvements. However, materials limitations prevent the operation of diesel vehicles at high temperatures. The fuel efficiency of gasoline-powered vehicles is currently improved by reducing the weight of the automobile and treated the emissions with a three-way catalyst. Additional improvements can be achieved with the use of advanced materials that reduce the weight of vehicles without compromising safety. The use of ceramics,more » fiber-reinforced plastics, and metal-matrix composites are discussed. The paper also discusses automotive catalysts and their components, electrically heated catalyst devices, a lean-burn NOx catalyst, and the future for materials chemistry.« less

Catalytic combustion of coal-derived liquids

NASA Technical Reports Server (NTRS)

Bulzan, D. L.; Tacina, R. R.

1981-01-01

A noble metal catalytic reactor was tested with three grades of SRC 2 coal derived liquids, naphtha, middle distillate, and a blend of three parts middle distillate to one part heavy distillate. A petroleum derived number 2 diesel fuel was also tested to provide a direct comparison. The catalytic reactor was tested at inlet temperatures from 600 to 800 K, reference velocities from 10 to 20 m/s, lean fuel air ratios, and a pressure of 3 x 10 to the 5th power Pa. Compared to the diesel, the naphtha gave slightly better combustion efficiency, the middle distillate was almost identical, and the middle heavy blend was slightly poorer. The coal derived liquid fuels contained from 0.58 to 0.95 percent nitrogen by weight. Conversion of fuel nitrogen to NOx was approximately 75 percent for all three grades of the coal derived liquids.

A comparison of emissions from vehicles fueled with diesel or compressed natural gas.

PubMed

Hesterberg, Thomas W; Lapin, Charles A; Bunn, William B

2008-09-01

A comprehensive comparison of emissions from vehicles fueled with diesel or compressed natural gas (CNG) was developed from 25 reports on transit buses, school buses, refuse trucks, and passenger cars. Emissions for most compounds were highest for untreated exhaust emissions and lowest for treated exhaust CNG buses without after-treatment had the highest emissions of carbon monoxide, hydrocarbons, nonmethane hydrocarbons (NMHC), volatile organic compounds (VOCs; e.g., benzene, butadiene, ethylene, etc.), and carbonyl compounds (e.g., formaldehyde, acetaldehyde, acrolein). Diesel buses without after-treatment had the highest emissions of particulate matter and polycyclic aromatic hydrocarbons (PAHs). Exhaust after-treatments reduced most emissions to similar levels in diesel and CNG buses. Nitrogen oxides (NO(x)) and carbon dioxide (CO2) emissions were similar for most vehicle types, fuels, and exhaust after-treatments with some exceptions. Diesel school buses had higher CO2 emissions than the CNG bus. CNG transit buses and passenger cars equipped with three-way catalysts had lower NO(x) emissions. Diesel buses equipped with traps had higher nitrogen dioxide emissions. Fuel economy was best in the diesel buses not equipped with exhaust after-treatment.

A preliminary study of the effect of equivalence ratio on a low emissions gas turbine combustor using KIVA-2

NASA Astrophysics Data System (ADS)

Yang, S. L.; Chen, R.; Cline, M. C.

The staged turbine combustor (STC) concept has drawn more and more attention since the late 70's because of its potential in reducing pollutant emissions where a high power output is required. A numerical study is performed to investigate the chemically reactive flow with sprays inside a STC combustor using a modified version of the KIVA-II code. This STC combustor consists of a fuel nozzle (FN), a rich-burn (RB) zone, a converging connecting section, a quick-quench (QQ) zone, a diverging connecting section, and a lean-combustion (LC) zone. An advanced airblast fuel nozzle, which has two fuel injection passages and four air flow passages for providing swirl, is used in this study. The effect of the equivalence ratio phi on the performance of the STC combustor is reported in this paper for phi range of 1.2 to 2.0. Preliminary results reveal some major features of the flow and temperature fields inside the STC combustor. Distributions of velocity, temperature, and some critical species information inside the FN/RB zone illustrate the effect of phi on the flame temperature and the NO(x) formation in rich burning. The co- and counter-rotating bulk flow, and the sandwiched-ring-shape temperature field in the QQ/LC zone, typical of the confined inclined jet-in-cross flow, are clearly shown from the computation. The predicted mass-weighted standard deviation and the pattern factor of temperature show that the mixing performance of the STC combustor is very good. The temperature of the fluid leaving the LC zone is very uniform. As expected. lower value of the emission index of NO can be achieved with larger value of phi. Prediction of the NO(x) emission shows that there is no excessive thermal NO(x) produced in the QQ/LC zone for all the cases studied.

Response mechanisms of attached premixed flames subjected to harmonic forcing

NASA Astrophysics Data System (ADS)

Shreekrishna

The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the vicinity of typical screech frequencies in gas turbine combustors. The nonlinear response problem is exclusively studied in the case of equivalence ratio coupling. Various nonlinearity mechanisms are identified, amongst which the crossover mechanisms, viz., stoichiometric and flammability crossovers, are seen to be responsible in causing saturation in the overall heat release magnitude of the flame. The response physics remain the same across various preheat temperatures and reactant pressures. Finally, comparisons between the chemiluminescence transfer function obtained experimentally and the heat release transfer functions obtained from the reduced order model (ROM) are performed for lean, CH4/Air swirl-stabilized, axisymmetric V-flames. While the comparison between the phases of the experimental and theoretical transfer functions are encouraging, their magnitudes show disagreement at lower Strouhal number gains show disagreement.

Dedicated exhaust gas recirculation control systems and methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sczomak, David P.; Narayanaswamy, Kushal; Keating, Edward J.

An engine control system of a vehicle includes a fuel control module that controls fuel injection of a first cylinder of an engine based on a first target air/fuel ratio that is fuel lean relative to a stoichiometric air/fuel ratio and that controls fuel injection of a second cylinder of the engine based on a second target air/fuel ratio that is fuel rich relative to stoichiometry. The first cylinder outputs exhaust to a first three way catalyst (TWC), and the second cylinder outputs exhaust to an exhaust gas recirculation (EGR) valve. An EGR control module controls opening of the EGRmore » valve to: (i) a second TWC that reacts with nitrogen oxides (NOx) in the exhaust and outputs ammonia to a selective catalytic reduction (SCR) catalyst; and (ii) a conduit that recirculates exhaust back to an intake system of the engine.« less

Optical diagnostics in gas turbine combustors

NASA Astrophysics Data System (ADS)

Woodruff, Steven D.

1999-01-01

Deregulation of the power industry and increasingly tight emission controls are pushing gas turbine manufacturers to develop engines operating at high pressure for efficiency and lean fuel mixtures to control NOx. This combination also gives rise to combustion instabilities which threaten engine integrity through acoustic pressure oscillations and flashback. High speed imaging and OH emission sensors have been demonstrated to be invaluable tools in characterizing and monitoring unstable combustion processes. Asynchronous imaging technique permit detailed viewing of cyclic flame structure in an acoustic environment which may be modeled or utilized in burner design . The response of the flame front to the acoustic pressure cycle may be tracked with an OH emission monitor using a sapphire light pipe for optical access. The OH optical emission can be correlated to pressure sensor data for better understanding of the acoustical coupling of the flame. Active control f the combustion cycle can be implemented using an OH emission sensor for feedback.

Sensitivity of Combustion-Acoustic Instabilities to Boundary Conditions for Premixed Gas Turbine Combustors

NASA Technical Reports Server (NTRS)

Darling, Douglas; Radhakrishnan, Krishnan; Oyediran, Ayo

1995-01-01

Premixed combustors, which are being considered for low NOx engines, are susceptible to instabilities due to feedback between pressure perturbations and combustion. This feedback can cause damaging mechanical vibrations of the system as well as degrade the emissions characteristics and combustion efficiency. In a lean combustor instabilities can also lead to blowout. A model was developed to perform linear combustion-acoustic stability analysis using detailed chemical kinetic mechanisms. The Lewis Kinetics and Sensitivity Analysis Code, LSENS, was used to calculate the sensitivities of the heat release rate to perturbations in density and temperature. In the present work, an assumption was made that the mean flow velocity was small relative to the speed of sound. Results of this model showed the regions of growth of perturbations to be most sensitive to the reflectivity of the boundary when reflectivities were close to unity.

Emissions of Jatropha oil-derived biodiesel blend fuels during combustion in a swirl burner

NASA Astrophysics Data System (ADS)

Norwazan, A. R.; Mohd. Jaafar, M. N.; Sapee, S.; Farouk, Hazir

2018-03-01

Experimental works on combustion of jatropha oil biodiesel blends of fuel with high swirling flow in swirl burner have been studied in various blends percentage. Jatropha oil biodiesel was produced using a two-step of esterification-transesterification process. The paper focuses on the emissions of biodiesel blends fuel using jatropha oil in lean through to rich air/fuel mixture combustion in swirl burner. The emissions performances were evaluated by using axial swirler amongst jatropha oil blends fuel including diesel fuel as baseline. The results show that the B25 has good emissions even though it has a higher emission of NOx than diesel fuel, while it emits as low as 42% of CO, 33% of SO2 and 50% of UHC emissions with high swirl number. These are due to the higher oxygen content in jatropha oil biodiesel.

Parametric Design of Injectors for LDI-3 Combustors

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Mongia, Hukam; Lee, Phil

2015-01-01

Application of a partially calibrated National Combustion Code (NCC) for providing guidance in the design of the 3rd generation of the Lean-Direct Injection (LDI) multi-element combustion configuration (LDI-3) is summarized. NCC was used to perform non-reacting and two-phase reacting flow computations on several LDI-3 injector configurations in a single-element and a five-element injector array. All computations were performed with a consistent approach for mesh-generation, turbulence, spray simulations, ignition and chemical kinetics-modeling. Both qualitative and quantitative assessment of the computed flowfield characteristics of the several design options led to selection of an optimal injector LDI- 3 design that met all the requirements including effective area, aerodynamics and fuel-air mixing criteria. Computed LDI-3 emissions (namely, NOx, CO and UHC) will be compared with the prior generation LDI- 2 combustor experimental data at relevant engine cycle conditions.

Gas turbine power plant with supersonic shock compression ramps

DOEpatents

Lawlor, Shawn P [Bellevue, WA; Novaresi, Mark A [San Diego, CA; Cornelius, Charles C [Kirkland, WA

2008-10-14

A gas turbine engine. The engine is based on the use of a gas turbine driven rotor having a compression ramp traveling at a local supersonic inlet velocity (based on the combination of inlet gas velocity and tangential speed of the ramp) which compresses inlet gas against a stationary sidewall. The supersonic compressor efficiently achieves high compression ratios while utilizing a compact, stabilized gasdynamic flow path. Operated at supersonic speeds, the inlet stabilizes an oblique/normal shock system in the gasdynamic flow path formed between the rim of the rotor, the strakes, and a stationary external housing. Part load efficiency is enhanced by use of a lean pre-mix system, a pre-swirl compressor, and a bypass stream to bleed a portion of the gas after passing through the pre-swirl compressor to the combustion gas outlet. Use of a stationary low NOx combustor provides excellent emissions results.

Joining of Silicon Carbide: Diffusion Bond Optimization and Characterization

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Singh, Mrityunjay

2008-01-01

Joining and integration methods are critically needed as enabling technologies for the full utilization of advanced ceramic components in aerospace and aeronautics applications. One such application is a lean direct injector for a turbine engine to achieve low NOx emissions. In the application, several SiC substrates with different hole patterns to form fuel and combustion air channels are bonded to form the injector. Diffusion bonding is a joining approach that offers uniform bonds with high temperature capability, chemical stability, and high strength. Diffusion bonding was investigated with the aid of titanium foils and coatings as the interlayer between SiC substrates to aid bonding. The influence of such variables as interlayer type, interlayer thickness, substrate finish, and processing time were investigated. Optical microscopy, scanning electron microscopy, and electron microprobe analysis were used to characterize the bonds and to identify the reaction formed phases.

Low-Temperature Pd/Zeolite Passive NO x Adsorbers: Structure, Performance, and Adsorption Chemistry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zheng, Yang; Kovarik, Libor; Engelhard, Mark H.

Pd/zeolite passive NOx adsorber (PNA) materials were prepared with solution ion-exchange between NH4/zeolites (Beta, ZSM-5 and SSZ-13) and PdCl2 solutions. The nature of Pd (dispersion, distribution and oxidation states) in these materials was characterized with Na+ ion-exchange, TEM imaging, CO titration with FTIR and in situ XPS. The NOx trapping and release properties were tested using feeds with different compositions. It is concluded that multiple Pd species coexist in these materials: atomically dispersed Pd in the cationic sites of zeolites, and PdO2 and PdO particles on the external surfaces. While Pd is largely atomically dispersed in ZSM-5, the small poremore » opening for SSZ-13 inhibits Pd diffusion such that the majority of Pd stays as external surface PdO2 clusters. NOx trapping and release are not simple chemisorption and desorption events, but involve rather complex chemical reactions. In the absence of CO in the feed, cationic Pd(II) sites with oxygen ligands and PdO2 clusters are reduced by NO to Pd(I) and PdO clusters. These reduced sites are the primary NO adsorption sites. In the presence of H2O, the as-formed NO2 desorb immediately. In the presence of CO in the feed, metallic Pd, “naked” Pd2+, and Pd+ sites are responsible for NO adsorption. For Pd adsorption sites with the same oxidation states but in different zeolite frameworks, NO binding energies are not expected to vary greatly. However, NO release temperatures do vary substantially with different zeolite structures. This indicates that NO transport within these materials play an important role in determining release temperatures. Finally, some rational design principles on efficient PNA materials are suggested. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle. Discussions with Drs. A. Yezerets, J.Y. Luo, K. Kamasamudram and N. Currier Cummins, Inc., and H.Y. Chen from Johnson-Matthey are greatly appreciated.« less

Field Effects of Buoyancy on Lean Premixed Turbulent Flames

NASA Technical Reports Server (NTRS)

Cheng, R. K.; Johnson, M. R.; Greenberg, P. S.; Wernet, M. P.

2003-01-01

The study of field effects of buoyancy on premixed turbulent flames is directed towards the advancement of turbulent combustion theory and the development of cleaner combustion technologies. Turbulent combustion is considered the most important unsolved problem in combustion science and laboratory studies of turbulence flame processes are vital to theoretical development. Although buoyancy is dominant in laboratory flames, most combustion models are not yet capable to consider buoyancy effects. This inconsistency has impeded the validation of theories and numerical simulations with experiments. Conversely, the understanding of buoyancy effects is far too limited to help develop buoyant flame models. Our research is also relevant to combustion technology because lean premixed combustion is a proven method to reduce the formation of oxides of nitrogen (NOx). In industrial lean premixed combustion systems, their operating conditions make them susceptible to buoyancy thus affecting heat distribution, emissions, stability, flashback and blowoff. But little knowledge is available to guide combustion engineers as to how to avoid or overcome these problems. Our hypothesis is that through its influence on the mean pressure field, buoyancy has direct and indirect effects on local flame/turbulence interactions. Although buoyancy acts on the hot products in the farfield the effect is also felt in the nearfield region upstream of the flame. These changes also influence the generation and dissipation of turbulent kinetic energy inside the flame brush and throughout the flowfield. Moreover, the plume of an open flame is unstable and the periodic fluctuations make additional contributions to flame front dynamics in the farfield. Therefore, processes such as flame wrinkling, flow acceleration due to heat release and flame- generated vorticity are all affected. Other global flame properties (e.g. flame stabilization limits and flame speed) may all be coupled to buoyancy. This problem poses major challenges to combustion modeling due to its need for a computation domain extending into the farfield and full specifications of upstream, wall and downstream boundary conditions.

Measurements of HONO, NO, NOy and SO2 in aircraft exhaust plumes at cruise

NASA Astrophysics Data System (ADS)

Jurkat, T.; Voigt, C.; Arnold, F.; Schlager, H.; Kleffmann, J.; Aufmhoff, H.; Schäuble, D.; Schaefer, M.; Schumann, U.

2011-05-01

Measurements of gaseous nitrogen and sulfur oxide emissions in young aircraft exhaust plumes give insight into chemical oxidation processes inside aircraft engines. Particularly, the OH-induced formation of nitrous acid (HONO) from nitrogen oxide (NO) and sulfuric acid (H2SO4) from sulfur dioxide (SO2) inside the turbine which is highly uncertain, need detailed analysis to address the climate impact of aviation. We report on airborne in situ measurements at cruise altitudes of HONO, NO, NOy, and SO2 in 9 wakes of 8 different types of modern jet airliners, including for the first time also an A380. Measurements of HONO and SO2 were made with an ITCIMS (Ion Trap Chemical Ionization Mass Spectrometer) using a new ion-reaction scheme involving SF5- reagent ions. The measured molar ratios HONO/NO and HONO/NOy with averages of 0.038 ± 0.010 and 0.027 ± 0.005 were found to decrease systematically with increasing NOx emission-index (EI NOx). We calculate an average EI HONO of 0.31 ± 0.12 g NO2 kg-1. Using reliable measurements of HONO and NOy, which are less adhesive than H2SO4 to the inlet walls, we derive the OH-induced conversion fraction of fuel sulfur to sulfuric acid $\\varepsilon$ with an average of 2.2 ± 0.5 %. $\\varepsilon$ also tends to decrease with increasing EI NOx, consistent with earlier model simulations. The lowest HONO/NO, HONO/NOy and $\\varepsilon$ was observed for the largest passenger aircraft A380.

Performance of a Laser Ignited Multicylinder Lean Burn Natural Gas Engine

DOE PAGES

Almansour, Bader; Vasu, Subith; Gupta, Sreenath B.; ...

2017-06-06

Market demands for lower fueling costs and higher specific powers in stationary natural gas engines has engine designs trending towards higher in-cylinder pressures and leaner combustion operation. However, Ignition remains as the main limiting factor in achieving further performance improvements in these engines. Addressing this concern, while incorporating various recent advances in optics and laser technologies, laser igniters were designed and developed through numerous iterations. Final designs incorporated water-cooled, passively Q-switched, Nd:YAG micro-lasers that were optimized for stable operation under harsh engine conditions. Subsequently, the micro-lasers were installed in the individual cylinders of a lean-burn, 350 kW, inline 6-cylinder, open-chamber,more » spark ignited engine and tests were conducted. To the best of our knowledge, this is the world’s first demonstration of a laser ignited multi-cylinder natural gas engine. The engine was operated at high-load (298 kW) and rated speed (1800 rpm) conditions. Ignition timing sweeps and excess-air ratio (λ) sweeps were performed while keeping the NOx emissions below the USEPA regulated value (BSNOx < 1.34 g/kW-hr), and while maintaining ignition stability at industry acceptable values (COV_IMEP <5 %). Through such engine tests, the relative merits of (i) standard electrical ignition system, and (ii) laser ignition system were determined. In conclusion, a rigorous combustion data analysis was performed and the main reasons leading to improved performance in the case of laser ignition were identified.« less

Performance of a Laser Ignited Multicylinder Lean Burn Natural Gas Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almansour, Bader; Vasu, Subith; Gupta, Sreenath B.

Market demands for lower fueling costs and higher specific powers in stationary natural gas engines has engine designs trending towards higher in-cylinder pressures and leaner combustion operation. However, Ignition remains as the main limiting factor in achieving further performance improvements in these engines. Addressing this concern, while incorporating various recent advances in optics and laser technologies, laser igniters were designed and developed through numerous iterations. Final designs incorporated water-cooled, passively Q-switched, Nd:YAG micro-lasers that were optimized for stable operation under harsh engine conditions. Subsequently, the micro-lasers were installed in the individual cylinders of a lean-burn, 350 kW, inline 6-cylinder, open-chamber,more » spark ignited engine and tests were conducted. To the best of our knowledge, this is the world’s first demonstration of a laser ignited multi-cylinder natural gas engine. The engine was operated at high-load (298 kW) and rated speed (1800 rpm) conditions. Ignition timing sweeps and excess-air ratio (λ) sweeps were performed while keeping the NOx emissions below the USEPA regulated value (BSNOx < 1.34 g/kW-hr), and while maintaining ignition stability at industry acceptable values (COV_IMEP <5 %). Through such engine tests, the relative merits of (i) standard electrical ignition system, and (ii) laser ignition system were determined. In conclusion, a rigorous combustion data analysis was performed and the main reasons leading to improved performance in the case of laser ignition were identified.« less

Can Water-Injected Turbomachines Provide Cost-Effective Emissions and Maintenance Reductions?

NASA Technical Reports Server (NTRS)

Hendricks, Robert C.; Daggett, David L.; Shouse, Dale T.; Roquemore, William M.; Brankovic, Andreja; Ryder, Robert C., Jr.

2011-01-01

An investigation has been performed to evaluate the effect of water injection on the performance of the Air Force Research Laboratory (AFRL, Wright-Patterson Air Force Base (WPAFB)) experimental trapped vortex combustor (TVC) over a range of fuel-to-air and water-to-fuel ratios. Performance is characterized by combustor exit quantities: temperature and emissions measurements using rakes, and overall pressure drop, from upstream plenum to combustor exit. Combustor visualization is performed using gray-scale and color still photographs and high-frame-rate videos. A parallel investigation evaluated the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid fueled combustor (e.g., TVC) that uses water injection for control of pollutant emissions and turbine inlet temperature. Generally, reasonable agreement is found between data and NO(x) computations. Based on a study assessing the feasibility and performance impact of using water injection on a Boeing 747-400 aircraft to reduce NO(x) emissions during takeoff, retrofitting does not appear to be cost effective; however, an operator of a newly designed engine and airframe might be able to save up to 1.0 percent in operating costs. Other challenges of water injection will be discussed.

Flame Stability in a Trapped-Vortex Spray-Combustor

NASA Astrophysics Data System (ADS)

Chakka, P.; Mancilla, P. C.; Acharya, S.

1999-11-01

Flame stabilization mechanisms in a Trapped-Vortex (TV) cavity is investigated experimentally and computationally in the current research. The TV-cavity is placed coaxially in the combustor and the flame is maintained through injection of liquid fuel spray and air from the inside face of the afterbody. This concept was introduced by Roquemore and company of Wright-Patterson AFB for gaseous fuel injection into the cavity and is extended for liquid fuel sprays in the current research. The flame holding capability of the TV-cavity is studied for different equivalence ratios of the secondary injection and overall Lean Blow-Out (LBO) limits are presented for different primary and secondary flow rates. The interaction and mixing of the main flow with the secondary vortex flow is investigated through the Laser Doppler Velocimetry measurements taken through a quartz window near the cavity. Also, temperature distribution through IR measurements and pressure fluctuations inside the chamber are presented for complete performance analysis of the TV cavity combustor.

Determination of cyclic volatile methylsiloxanes in biota with a purge and trap method.

PubMed

Kierkegaard, Amelie; Adolfsson-Erici, Margaretha; McLachlan, Michael S

2010-11-15

The three cyclic volatile methylsiloxanes (cVMS), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6), are recently identified environmental contaminants. Methods for the trace analysis of these chemicals in environmental matrices are required. A purge and trap method to prepare highly purified sample extracts with a low risk of sample contamination is presented. Without prior homogenization, the sample is heated in water, and the cVMS are purged from the slurry and trapped on an Isolute ENV+ cartridge. They are subsequently eluted with n-hexane and analyzed with GC/MS. The method was tested for eight different matrices including ragworms, muscle tissue from lean and lipid-rich fish, cod liver, and seal blubber. Analyte recoveries were consistent within and between matrices, averaging 79%, 68%, and 56% for D4, D5, and D6, respectively. Good control of blank levels resulted in limits of quantification of 1.5, 0.6, and 0.6 ng/g wet weight. The repeatability was 12% (D5) and 15% (D6) at concentrations 9 and 2 times above the LOQ. The method was applied to analyze cVMS in fish from Swedish lakes, demonstrating that contamination in fish as a result of long-range atmospheric transport is low as compared to contamination from local sources.

Quick-Mixing Studies Under Reacting Conditions

NASA Technical Reports Server (NTRS)

Leong, May Y.; Samuelsen, G. S.

1996-01-01

The low-NO(x) emitting potential of rich-burn/quick-mix/lean-burn )RQL) combustion makes it an attractive option for engines of future stratospheric aircraft. Because NO(x) formation is exponentially dependent on temperature, the success of the RQL combustor depends on minimizing high temperature stoichiometric pocket formation in the quick-mixing section. An experiment was designed and built, and tests were performed to characterize reaction and mixing properties of jets issuing from round orifices into a hot, fuel-rich crossflow confined in a cylindrical duct. The reactor operates on propane and presents a uniform, non-swirling mixture to the mixing modules. Modules consisting of round orifice configurations of 8, 9, 10, 12, 14, and 18 holes were evaluated at a momentum-flux ratio of 57 and jet-to-mainstream mass-flaw ratio of 2.5. Temperatures and concentrations of O2, CO2, CO, HC, and NO(x) were obtained upstream, down-stream, and within the orifice plane to determine jet penetration as well as reaction processes. Jet penetration was a function of the number of orifices and affected the mixing in the reacting system. Of the six configurations tested, the 14-hole module produced jet penetration close to the module half-radius and yielded the best mixing and most complete combustion at a plane one duct diameter from the orifice leading edge. The results reveal that substantial reaction and heat release occur in the jet mixing zone when the entering effluent is hot and rich, and that the experiment as designed will serve to explore satisfactorily jet mixing behavior under realistic reacting conditions in future studies.

Reinforcement-learning-based output-feedback control of nonstrict nonlinear discrete-time systems with application to engine emission control.

PubMed

Shih, Peter; Kaul, Brian C; Jagannathan, Sarangapani; Drallmeier, James A

2009-10-01

A novel reinforcement-learning-based output adaptive neural network (NN) controller, which is also referred to as the adaptive-critic NN controller, is developed to deliver the desired tracking performance for a class of nonlinear discrete-time systems expressed in nonstrict feedback form in the presence of bounded and unknown disturbances. The adaptive-critic NN controller consists of an observer, a critic, and two action NNs. The observer estimates the states and output, and the two action NNs provide virtual and actual control inputs to the nonlinear discrete-time system. The critic approximates a certain strategic utility function, and the action NNs minimize the strategic utility function and control inputs. All NN weights adapt online toward minimization of a performance index, utilizing the gradient-descent-based rule, in contrast with iteration-based adaptive-critic schemes. Lyapunov functions are used to show the stability of the closed-loop tracking error, weights, and observer estimates. Separation and certainty equivalence principles, persistency of excitation condition, and linearity in the unknown parameter assumption are not needed. Experimental results on a spark ignition (SI) engine operating lean at an equivalence ratio of 0.75 show a significant (25%) reduction in cyclic dispersion in heat release with control, while the average fuel input changes by less than 1% compared with the uncontrolled case. Consequently, oxides of nitrogen (NO(x)) drop by 30%, and unburned hydrocarbons drop by 16% with control. Overall, NO(x)'s are reduced by over 80% compared with stoichiometric levels.

An Experimental Investigation of Self-Excited Combustion Dynamics in a Single Element Lean Direct Injection (LDI) Combustor

NASA Astrophysics Data System (ADS)

Gejji, Rohan M.

The management of combustion dynamics in gas turbine combustors has become more challenging as strict NOx/CO emission standards have led to engine operation in a narrow, lean regime. While premixed or partially premixed combustor configurations such as the Lean Premixed Pre-vaporized (LPP), Rich Quench Lean burn (RQL), and Lean Direct Injection (LDI) have shown a potential for reduced NOx emissions, they promote a coupling between acoustics, hydrodynamics and combustion that can lead to combustion instabilities. These couplings can be quite complex, and their detailed understanding is a pre-requisite to any engine development program and for the development of predictive capability for combustion instabilities through high-fidelity models. The overarching goal of this project is to assess the capability of high-fidelity simulation to predict combustion dynamics in low-emissions gas turbine combustors. A prototypical lean-direct-inject combustor was designed in a modular configuration so that a suitable geometry could be found by test. The combustor comprised a variable length air plenum and combustion chamber, air swirler, and fuel nozzle located inside a subsonic venturi. The venturi cross section and the fuel nozzle were consistent with previous studies. Test pressure was 1 MPa and variables included geometry and acoustic resonance, inlet temperatures, equivalence ratio, and type of liquid fuel. High-frequency pressure measurements in a well-instrumented metal chamber yielded frequencies and mode shapes as a function of inlet air temperature, equivalence ratio, fuel nozzle placement, and combustor acoustic resonances. The parametric survey was a significant effort, with over 105 tests on eight geometric configurations. A good dataset was obtained that could be used for both operating-point-dependent quantitative comparisons, and testing the ability of the simulation to predict more global trends. Results showed a very strong dependence of instability amplitude on the geometric configuration of the combustor, i.e., its acoustic resonance characteristics, with measured pressure fluctuation amplitudes ranged from 5 kPa (0.5% of mean pressure) to 200 kPa ( 20% of mean pressure) depending on combustor geometry. The stability behavior also showed a consistent and pronounced dependence on equivalence ratio and inlet air temperature. Instability amplitude increased with higher equivalence ratio and with lower inlet air temperature. A pronounced effect of fuel nozzle location on the combustion dynamics was also observed. Combustion instabilities with the fuel nozzle at the throat of the venturi throat were stronger than in the configuration with fuel nozzle 2.6 mm upstream of the nozzle. A second set of dynamics data was based on high-response-rate laser-based combustion diagnostics using an optically accessible combustor section. High-frequency measurements of OH*-chemiluminescence and OH-PLIF and velocity fields using PIV were obtained at a relatively stable, low equivalence ratio case and a less stable case at higher equivalence ratio. PIV measurements were performed at 5 kHz for non-reacting flow but glare from the cylindrical quartz chamber limited the field of view to a small region in the combustor. Quantitative and qualitative comparisons were made for five different combinations of geometry and operating condition that yielded discriminating stability behavior in the experiment with simulations that were carried out concurrently. Comparisons were made on the basis of trends and pressure mode data as well as with OH-PLIF measurements for the baseline geometry at equivalence ratios of 0.44 and 0.6. Overall, the ability of the simulation to match experimental data and trends was encouraging. Dynamic Mode Decomposition (DMD) analysis was performed on two sets of computations - a global 2-step chemistry mechanism and an 18-step chemistry mechanism - and the OH-PLIF images to allow comparison of dynamic patterns of heat release and OH distribution in the combustion zone. The DMD analysis was able to identify similar dominant unstable modes in the combustor. Recommendations for future work are based on the continued requirement for quantitative and spatio-temporally resolved data for direct comparison with computational efforts to develop predictive capabilities for combustion instabilities at relevant operating conditions. Discriminating instability behavior for the prototypical combustor demonstrated in this study is critical for any robust validation effort Unit physics based scaling of the current effort to multi-element combustors along with improvement in diagnostic techniques and analysis efforts are recommended for advancement in understanding of the complex physics in the multi-phase, three dimensional and turbulent combustion processes in the LDI combustor.

AGT-102 automotive gas turbine

NASA Technical Reports Server (NTRS)

1981-01-01

Development of a gas turbine powertrain with a 30% fuel economy improvement over a comparable S1 reciprocating engine, operation within 0.41 HC, 3.4 CO, and 0.40 NOx grams per mile emissions levels, and ability to use a variety of alternate fuels is summarized. The powertrain concept consists of a single-shaft engine with a ceramic inner shell for containment of hot gasses and support of twin regenerators. It uses a fixed-geometry, lean, premixed, prevaporized combustor, and a ceramic radial turbine rotor supported by an air-lubricated journal bearing. The engine is coupled to the vehicle through a widerange continuously variable transmission, which utilizes gearing and a variable-ratio metal compression belt. A response assist flywheel is used to achieve acceptable levels of engine response. The package offers a 100 lb weight advantage in a Chrysler K Car front-wheel-drive installation. Initial layout studies, preliminary transient thermal analysis, ceramic inner housing structural analysis, and detailed performance analysis were carried out for the basic engine.

CFD Analysis of Emissions for a Candidate N+3 Combustor

NASA Technical Reports Server (NTRS)

Ajmani, Kumud

2015-01-01

An effort was undertaken to analyze the performance of a model Lean-Direct Injection (LDI) combustor designed to meet emissions and performance goals for NASA's N+3 program. Computational predictions of Emissions Index (EINOx) and combustor exit temperature were obtained for operation at typical power conditions expected of a small-core, high pressure-ratio (greater than 50), high T3 inlet temperature (greater than 950K) N+3 combustor. Reacting-flow computations were performed with the National Combustion Code (NCC) for a model N+3 LDI combustor, which consisted of a nine-element LDI flame-tube derived from a previous generation (N+2) thirteen-element LDI design. A consistent approach to mesh-optimization, spraymodeling and kinetics-modeling was used, in order to leverage the lessons learned from previous N+2 flame-tube analysis with the NCC. The NCC predictions for the current, non-optimized N+3 combustor operating indicated a 74% increase in NOx emissions as compared to that of the emissions-optimized, parent N+2 LDI combustor.

CFD Analysis of Emissions for a Candidate N+3 Combustor

NASA Technical Reports Server (NTRS)

Ajmani, Kumud

2015-01-01

An effort was undertaken to analyze the performance of a model Lean-Direct Injection (LDI) combustor designed to meet emissions and performance goals for NASA's N+3 program. Computational predictions of Emissions Index (EINOx) and combustor exit temperature were obtained for operation at typical power conditions expected of a small-core, high pressure-ratio (greater than 50), high T3 inlet temperature (greater than 950K) N+3 combustor. Reacting-flow computations were performed with the National Combustion Code (NCC) for a model N+3 LDI combustor, which consisted of a nine-element LDI flame-tube derived from a previous generation (N+2) thirteen-element LDI design. A consistent approach to mesh-optimization, spray-modeling and kinetics-modeling was used, in order to leverage the lessons learned from previous N+2 flame-tube analysis with the NCC. The NCC predictions for the current, non-optimized N+3 combustor operating indicated a 74% increase in NOx emissions as compared to that of the emissions-optimized, parent N+2 LDI combustor.

Research and Development of Natural Draft Ultra-Low Emissions Burners for Gas Appliances

DOE Office of Scientific and Technical Information (OSTI.GOV)

Therkelsen, Peter; Cheng, Robert; Sholes, Darren

Combustion systems used in residential and commercial cooking appliances must be robust and easy to use while meeting air quality standards. Current air quality standards for cooking appliances are far greater than other stationary combustion equipment. By developing an advanced low emission combustion system for cooking appliances, the air quality impacts from these devices can be reduced. This project adapted the Lawrence Berkeley National Laboratory (LBNL) Ring-Stabilizer Burner combustion technology for residential and commercial natural gas fired cooking appliances (such as ovens, ranges, and cooktops). LBNL originally developed the Ring-Stabilizer Burner for a NASA funded microgravity experiment. This natural draftmore » combustion technology reduces NOx emissions significantly below current SCAQMD emissions standards without post combustion treatment. Additionally, the Ring-Stabilizer Burner technology does not require the assistance of a blower to achieve an ultra-low emission lean premix flame. The research team evaluated the Ring-Stabilizer Burner and fabricated the most promising designs based on their emissions and turndown.« less

Hyperinsulinemia fails to augment ET-1 action in the skeletal muscle vascular bed in vivo in humans

PubMed Central

Lteif, Amale A.; Fulford, Angie D.; Considine, Robert V.; Gelfand, Inessa; Baron, Alain D.; Mather, Kieren J.

2008-01-01

Endogenous endothelin action is augmented in human obesity and type 2 diabetes and contributes to endothelial dysfunction and impairs insulin-mediated vasodilation in humans. We hypothesized that insulin resistance-associated hyperinsulinemia could preferentially drive endothelin-mediated vasoconstriction. We applied hyperinsulinemic-euglycemic clamps with higher insulin dosing in obese subjects than lean subjects (30 vs. 10 mU·m−2·min−1, respectively), with the goal of matching insulin's nitric oxide (NO)-mediated vascular effects. We predicted that, under these circumstances, insulin-stimulated endothelin-1 (ET-1) action (assessed with the type A endothelin receptor antagonist BQ-123) would be augmented in proportion to hyperinsulinemia. NO bioactivity was assessed using the nitric oxide synthase inhibitor NG-monomethyl-l-arginine. Insulin-mediated vasodilation and insulin-stimulated NO bioavailability were well matched across groups by this approach. As expected, steady-state insulin levels were approximately threefold higher in obese than lean subjects (109.2 ± 10.2 pmol/l vs. 518.4 ± 84.0, P = 0.03). Despite this, the augmentation of insulin-mediated vasodilation by BQ-123 was not different between groups. ET-1 flux across the leg was not augmented by insulin alone but was increased with the addition of BQ-123 to insulin (P = 0.01 BQ-123 effect, P = not significant comparing groups). Endothelin antagonism augmented insulin-stimulated NO bioavailability and NOx flux, but not differently between groups and not proportional to hyperinsulinemia. These findings do not support the hypothesis that insulin resistance-associated hyperinsulinemia preferentially drives endothelin-mediated vasoconstriction. PMID:18957616

Final Report of a CRADA Between Pacific Northwest National Laboratory and the Ford Motor Company (CRADA No. PNNL/265): “Deactivation Mechanisms of Base Metal/Zeolite Urea Selective Catalytic Reduction Materials, and Development of Zeolite-Based Hydrocarbon Adsorber Materials”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Feng; Kwak, Ja Hun; Lee, Jong H.

2013-02-14

Reducing NOx emissions and particulate matter (PM) are primary concerns for diesel vehicles required to meet current LEV II and future LEV III emission standards which require 90+% NOx conversion. Currently, urea SCR as the NOx reductant and a Catalyzed Diesel Particulate Filter (CDPF) are being used for emission control system components by Ford Motor Company for 2010 and beyond diesel vehicles. Because the use of this technology for vehicle applications is new, the relative lack of experience makes it especially challenging to satisfy durability requirements. Of particular concern is being able to realistically simulate actual field aging of themore » catalyst systems under laboratory conditions. This is necessary both as a rapid assessment tool for verifying improved performance and certifiability of new catalyst formulations, and to develop a good understanding of deactivation mechanisms that can be used to develop improved catalyst materials. In addition to NOx and PM, the hydrocarbon (HC) emission standards are expected to become much more stringent during the next few years. Meanwhile, the engine-out HC emissions are expected to increase and/or be more difficult to remove. Since HC can be removed only when the catalyst becomes warm enough for its oxidation, three-way catalyst (TWC) and diesel oxidation catalyst (DOC) formulations often contain proprietary zeolite materials to hold the HC produced during the cold start period until the catalyst reaches its operating temperature (e.g., >200°C). Unfortunately, much of trapped HC tends to be released before the catalyst reaches the operating temperature. Among materials effective for trapping HC during the catalyst warm-up period, siliceous zeolites are commonly used because of their high surface area and high stability under typical operating conditions. However, there has been little research on the physical properties of these materials related to the adsorption and release of various hydrocarbon species found in the engine exhaust. For these reasons, automakers and engine manufacturers have difficulty improving their catalytic converters for meeting the stringent HC emission standards. In this collaborative program, scientists and engineers in the Institute for Integrated Catalysis at Pacific Northwest National Laboratory and at Ford Motor Company have investigated laboratory- and engine-aged SCR catalysts, containing mainly base metal zeolites. These studies are leading to a better understanding of various aging factors that impact the long-term performance of SCR catalysts and improve the correlation between laboratory and engine aging, saving experimental time and cost. We have also studied materials effective for the temporary storage of HC species during the cold-start period. In particular, we have examined the adsorption and desorption of various HC species produced during the combustion with different fuels (e.g., gasoline, E85, diesel) over potential HC adsorber materials, and measured the kinetic parameters to update Ford’s HC adsorption model. Since this CRADA has now been completed, in this final report we will provide brief summaries of most of the work carried out on this CRADA over the last several years.« less

Constitutive NADPH-dependent electron transferase activity of the Nox4 dehydrogenase domain.

PubMed

Nisimoto, Yukio; Jackson, Heather M; Ogawa, Hisamitsu; Kawahara, Tsukasa; Lambeth, J David

2010-03-23

NADPH oxidase 4 (Nox4) is constitutively active, while Nox2 requires the cytosolic regulatory subunits p47(phox) and p67(phox) and activated Rac with activation by phorbol 12-myristate 13-acetate (PMA). This study was undertaken to identify the domain on Nox4 that confers constitutive activity. Lysates from Nox4-expressing cells exhibited constitutive NADPH- but not NADH-dependent hydrogen peroxide production with a K(m) for NADPH of 55 +/- 10 microM. The concentration of Nox4 in cell lysates was estimated using Western blotting and allowed calculation of a turnover of approximately 200 mol of H(2)O(2) min(-1) (mol of Nox4)(-1). A chimeric protein (Nox2/4) consisting of the Nox2 transmembrane (TM) domain and the Nox4 dehydrogenase (DH) domain showed H(2)O(2) production in the absence of cytosolic regulatory subunits. In contrast, chimera Nox4/2, consisting of the Nox4 TM and Nox2 DH domains, exhibited PMA-dependent activation that required coexpression of regulatory subunits. Nox DH domains from several Nox isoforms were purified and evaluated for their electron transferase activities. Nox1 DH, Nox2 DH, and Nox5 DH domains exhibited barely detectable activities toward artificial electron acceptors, while the Nox4 DH domain exhibited significant rates of reduction of cytochrome c (160 min(-1), largely superoxide dismutase-independent), ferricyanide (470 min(-1)), and other electron acceptors (artificial dyes and cytochrome b(5)). Rates were similar to those observed for H(2)O(2) production by the Nox4 holoenzyme in cell lysates. The activity required added FAD and was seen with NADPH but not NADH. These results indicate that the Nox4 DH domain exists in an intrinsically activated state and that electron transfer from NADPH to FAD is likely to be rate-limiting in the NADPH-dependent reduction of oxygen by holo-Nox4.

Functions and regulation of the Nox family in the filamentous fungus Podospora anserina: a new role in cellulose degradation.

PubMed

Brun, Sylvain; Malagnac, Fabienne; Bidard, Frédérique; Lalucque, Hervé; Silar, Philippe

2009-10-01

NADPH oxidases are enzymes that produce reactive oxygen species. Studies in mammals, plants and fungi have shown that they play important roles in differentiation, defence, host/pathogen interaction and mutualistic symbiosis. In this paper, we have identified a Podospora anserina mutant strain impaired for processes controlled by PaNox1 and PaNox2, the two Nox isoforms characterized in this model ascomycete. We show that the gene mutated is PaNoxR, the homologue of the gene encoding the regulatory subunit p67(phox), conserved in mammals and fungi, and that PaNoxR regulates both PaNox1 and PaNox2. Genome sequence analysis of P. anserina reveals that this fungus posses a third Nox isoform, PaNox3, related to human Nox5/Duox and plant Rboh. We have generated a knock-out mutant of PaNox3 and report that PaNox3 plays a minor role in P. anserina, if any. We show that PaNox1 and PaNox2 play antagonist roles in cellulose degradation. Finally, we report for the first time that a saprobic fungus, P. anserina, develops special cell structures dedicated to breach and to exploit a solid cellulosic substrate, cellophane. Importantly, as for similar structures present in some plant pathogens, their proper differentiation requires PaNox1, PaNox2, PaNoxR and the tetraspanin PaPls1.

Characteristics of NOx emission from Chinese coal-fired power plants equipped with new technologies

NASA Astrophysics Data System (ADS)

Ma, Zizhen; Deng, Jianguo; Li, Zhen; Li, Qing; Zhao, Ping; Wang, Liguo; Sun, Yezhu; Zheng, Hongxian; Pan, Li; Zhao, Shun; Jiang, Jingkun; Wang, Shuxiao; Duan, Lei

2016-04-01

Coal combustion in coal-fired power plants is one of the important anthropogenic NOx sources, especially in China. Many policies and methods aiming at reducing pollutants, such as increasing installed capacity and installing air pollution control devices (APCDs), especially selective catalytic reduction (SCR) units, could alter NOx emission characteristics (NOx concentration, NO2/NOx ratio, and NOx emission factor). This study reported the NOx characteristics of eight new coal-fired power-generating units with different boiler patterns, installed capacities, operating loads, and coal types. The results showed that larger units produced less NOx, and anthracite combustion generated more NOx than bitumite and lignite combustion. During formation, the NOx emission factors varied from 1.81 to 6.14 g/kg, much lower than those of older units at similar scales. This implies that NOx emissions of current and future units could be overestimated if they are based on outdated emission factors. In addition, APCDs, especially SCR, greatly decreased NOx emissions, but increased NO2/NOx ratios. Regardless, the NO2/NOx ratios were lower than 5%, in accordance with the guidelines and supporting the current method for calculating NOx emissions from coal-fired power plants that ignore NO2.

Nitrogen Stable Isotope Composition of Various Fossil-fuel Combustion Nitrogen Oxide Sources

NASA Astrophysics Data System (ADS)

Walters, W.; Michalski, G. M.; Fang, H.

2015-12-01

Nitrogen oxides (NOx = NO + NO2) are important trace gases that impact atmospheric chemistry, air quality, and climate. In order to help constrain NOx source contributions, the nitrogen (N) stable isotope composition of NOx (δ15N-NOx) may be a useful indicator for NOx source partitioning. However, despite anthropogenic emissions being the most prevalent source of NOx, there is still large uncertainty in the δ15N-NOx values for anthropogenic sources. To this end, this study provides a detailed analysis of several fossil-fuel combustion NOx sources and their δ15N-NOx values. To accomplish this, exhaust or flue samples from several fossil-fuel combustion sources were sampled and analyzed for their δ15N-NOx that included airplanes, gasoline-powered vehicles not equipped with a catalytic converter, gasoline-powered lawn tools and utility vehicles, diesel-electric buses, diesel semi-trucks, and natural gas-burning home furnace and power plant. A relatively large range of δ15N-NOx values were measured from -28.1 to 0.3‰ for individual exhaust/flue samples with cold started diesel-electric buses contributing on average the lowest δ15N-NOx values at -20.9‰, and warm-started diesel-electric buses contributing on average the highest values of -1.7‰. The NOx sources analyzed in this study primarily originated from the "thermal production" of NOx and generally emitted negative δ15N-NOx values, likely due to the kinetic isotope effect associated with its production. It was found that there is a negative correlation between NOx concentrations and δ15N-NOx for fossil-fuel combustion sources equipped with catalytic NOx reduction technology, suggesting that the catalytic reduction of NOx may have an influence on δ15N-NOx values. Based on the δ15N-NOx values reported in this study and in previous studies, a δ15N-NOx regional and seasonal isoscape was constructed for the contiguous United States. The constructed isoscape demonstrates the seasonal importance of various NOx sources to particular regions and will be helpful in evaluating the N isotopes in nitrate deposition studies.

Optimizing the CSP Tower Air Brayton Cycle System to Meet the SunShot Objectives - Final Technical Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bryner, Elliott; Brun, Klaus; Coogan, Shane

The objective of this project is to increase Concentrated Solar Power (CSP) tower air receiver and gas turbine temperature capabilities to 1,000ºC by the development of a novel gas turbine combustor, which can be integrated on a megawatt-scale gas turbine, such as the Solar Turbines Mercury 50™. No combustor technology currently available is compatible with the CSP application target inlet air temperature of 1,000°C. Autoignition and flashback at this temperature prevent the use of conventional lean pre-mix injectors that are currently employed to manage NOx emissions. Additional challenges are introduced by the variability of the high-temperature heat source provided bymore » the field of solar collectors, the heliostat in CSP plants. For optimum energy generation from the power turbine, the turbine rotor inlet temperature (TRIT) should remain constant. As a result of changing heat load provided to the solar collector from the heliostat, the amount of energy input required from the combustion system must be adjusted to compensate. A novel multi-bank lean micro-mix injector has been designed and built to address the challenges of high-temperature combustion found in CSP applications. The multi-bank arrangement of the micro-mix injector selectively injects fuel to meet the heat addition requirements to maintain constant TRIT with changing solar load. To validate the design, operation, and performance of the multi-bank lean micro-mix injector, a novel combustion test facility has been designed and built at Southwest Research Institute® (SwRI®) in San Antonio, TX. This facility, located in the Turbomachinery Research Facility, provides in excess of two kilograms per second of compressed air at nearly eight bar pressure. A two-megawatt electric heater raises the inlet temperature to 800°C while a secondary gas-fired heater extends the operational temperature range of the facility to 1,000°C. A combustor test rig connected to the heater has been designed and built to test the multi-bank lean micro-mix injector over the range of CSP operating conditions. The fuel is controlled and selectively delivered to the banks of the injector based on combustor inlet conditions that correspond to turbine operating points. The combustor rig is equipped with a data acquisition system and a suite of instrumentation for measuring temperature, pressure, and species concentration. This unique test facility has been built and commissioned and a prototype of the multi-bank lean micro-mix injector design has been tested. Operation of the combustor and injector has been demonstrated over the full range of CSP inlet conditions and for the range of turbine load conditions specified. The multi-bank operation of the injector has been proven to be an effective design for managing the variable flow rates of air and fuel due to changing inlet conditions from the solar field and turbine loads.« less

40 CFR 96.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 96.188 Section 96.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.188 CAIR NOX allowance allocations to CAIR NOX opt...

40 CFR 97.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 97.188 Section 97.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... CAIR NOX Opt-In Units § 97.188 CAIR NOX allowance allocations to CAIR NOX opt-in units. (a) Timing...

40 CFR 96.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 96.188 Section 96.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.188 CAIR NOX allowance allocations to CAIR NOX opt...

40 CFR 96.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 96.188 Section 96.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.188 CAIR NOX allowance allocations to CAIR NOX opt...

40 CFR 97.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 97.188 Section 97.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... CAIR NOX Opt-In Units § 97.188 CAIR NOX allowance allocations to CAIR NOX opt-in units. (a) Timing...

40 CFR 97.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 97.188 Section 97.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... CAIR NOX Opt-In Units § 97.188 CAIR NOX allowance allocations to CAIR NOX opt-in units. (a) Timing...

40 CFR 97.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 97.188 Section 97.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... CAIR NOX Opt-In Units § 97.188 CAIR NOX allowance allocations to CAIR NOX opt-in units. (a) Timing...

40 CFR 96.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 96.188 Section 96.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.188 CAIR NOX allowance allocations to CAIR NOX opt...

40 CFR 96.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 96.188 Section 96.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.188 CAIR NOX allowance allocations to CAIR NOX opt...

40 CFR 97.188 - CAIR NOX allowance allocations to CAIR NOX opt-in units.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false CAIR NOX allowance allocations to CAIR NOX opt-in units. 97.188 Section 97.188 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... CAIR NOX Opt-In Units § 97.188 CAIR NOX allowance allocations to CAIR NOX opt-in units. (a) Timing...

Involvement of NADPH oxidase isoforms in the production of O2− manipulated by ABA in the senescing leaves of early-senescence-leaf (esl) mutant rice (Oryza sativa)

PubMed Central

Wang, Fubiao; Zhao, Qian; Liu, Jianchao; Cheng, Fangmin

2018-01-01

In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the esl mutant generated more O2- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O2- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O2- generation. The esl mutant exhibited significantly higher expression of OsNox2, OsNox5, OsNox6, and OsNox7 in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of OsNox1, OsNox3, and OsFR07 in the flag leaf of the esl mutant were significantly lower than those in the wild-type cultivar. The expression levels of OsNox2, OsNox5, OsNox6, and OsNox7 were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of OsNox2 and OsNox6 were dependent on the duration of ABA treatment. The inducible expression levels of OsNox5 and OsNox7 were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of OsNox1, OsNox3, and OsFR07 in the detached leaf segments. Therefore, OsNox2, OsNox5, OsNox6, and OsNox7 were probably involved in the ABA-induced O2- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the esl mutant. Conversely, OsNox1, OsNox3, and OsFR07 were not associated with ABA-induced O2- generation during leaf senescence. PMID:29309410

Involvement of NADPH oxidase isoforms in the production of O2- manipulated by ABA in the senescing leaves of early-senescence-leaf (esl) mutant rice (Oryza sativa).

PubMed

Li, Zhaowei; Wang, Fubiao; Zhao, Qian; Liu, Jianchao; Cheng, Fangmin

2018-01-01

In this study, the differences in reactive oxygen species (ROS) generation and abscisic acid (ABA) accumulation in senescing leaves were investigated by early-senescence-leaf (esl) mutant and its wild type, to clarify the relationship among ABA levels, ROS generation, and NADPH oxidase (Nox) in senescing leaves of rice (Oryza sativa). The temporal expression levels of OsNox isoforms in senescing leaves and their expression patterns in response to ABA treatment were determined through quantitative real-time reverse transcription PCR (qRT-PCR). Results showed that the flag leaf of the esl mutant generated more O2- concentrations and accumulated higher ABA levels than the wild-type cultivar did in the grain-filling stage. Exogenous ABA treatment induced O2- generation; however, it was depressed by diphenyleneiodonium chloride (DPI) pretreatment in the detached leaf segments. This finding suggested the involvement of NADPH oxidase in ABA-induced O2- generation. The esl mutant exhibited significantly higher expression of OsNox2, OsNox5, OsNox6, and OsNox7 in the initial of grain-filling stage, followed by sharply decrease. The transcriptional levels of OsNox1, OsNox3, and OsFR07 in the flag leaf of the esl mutant were significantly lower than those in the wild-type cultivar. The expression levels of OsNox2, OsNox5, OsNox6, and OsNox7 were significantly enhanced by exogenous ABA treatments. The enhanced expression levels of OsNox2 and OsNox6 were dependent on the duration of ABA treatment. The inducible expression levels of OsNox5 and OsNox7 were dependent on ABA concentrations. By contrast, exogenous ABA treatment severely repressed the transcripts of OsNox1, OsNox3, and OsFR07 in the detached leaf segments. Therefore, OsNox2, OsNox5, OsNox6, and OsNox7 were probably involved in the ABA-induced O2- generation in the initial stage of leaf senescence. Subsequently, other oxidases activated in deteriorating cells were associated with ROS generation and accumulation in the senescing leaves of the esl mutant. Conversely, OsNox1, OsNox3, and OsFR07 were not associated with ABA-induced O2- generation during leaf senescence.

Nitrogen Isotope Composition of Thermally Produced NOx from Various Fossil-Fuel Combustion Sources.

PubMed

Walters, Wendell W; Tharp, Bruce D; Fang, Huan; Kozak, Brian J; Michalski, Greg

2015-10-06

The nitrogen stable isotope composition of NOx (δ(15)N-NOx) may be a useful indicator for NOx source partitioning, which would help constrain NOx source contributions in nitrogen deposition studies. However, there is large uncertainty in the δ(15)N-NOx values for anthropogenic sources other than on-road vehicles and coal-fired energy generating units. To this end, this study presents a broad analysis of δ(15)N-NOx from several fossil-fuel combustion sources that includes: airplanes, gasoline-powered vehicles not equipped with a three-way catalytic converter, lawn equipment, utility vehicles, urban buses, semitrucks, residential gas furnaces, and natural-gas-fired power plants. A relatively large range of δ(15)N-NOx values was measured from -28.1‰ to 8.5‰ for individual exhaust/flue samples that generally tended to be negative due to the kinetic isotope effect associated with thermal NOx production. A negative correlation between NOx concentrations and δ(15)N-NOx for fossil-fuel combustion sources equipped with selective catalytic reducers was observed, suggesting that the catalytic reduction of NOx increases δ(15)N-NOx values relative to the NOx produced through fossil-fuel combustion processes. Combining the δ(15)N-NOx measured in this study with previous published values, a δ(15)N-NOx regional and seasonal isoscape was constructed for the contiguous U.S., which demonstrates seasonal and regional importance of various NOx sources.

Nebivolol ameliorated kidney damage in Zucker diabetic fatty rats by regulation of oxidative stress/NO pathway: comparison with captopril.

PubMed

Wang, Yan; An, Wenjing; Zhang, Fei; Niu, Mengzhen; Liu, Yu; Shi, Ruizan

2018-06-23

The aim was to evaluate the effects and mechanisms of nebivolol on renal damage in Zucker diabetic fatty (ZDF) rats, in comparison with those of atenolol and captopril. Animals were divided into: control lean Zucker rats, ZDF rats, ZDF rats orally treated with nebivolol (10 mg/kg), atenolol (100 mg/kg) or captopril (40 mg/kg) for 6 months. Systolic blood pressure (SBP), blood glucose, kidney structure and function, plasma and kidney levels of nitric oxide (NO) and asymmetric dimethylarginine (ADMA), and oxidant status were evaluated. Kidney expressions of AMP-activated protein kinase (AMPK), NADPH oxidase (NOX) isoforms 2 and 4 and subunit p22 phox , nitric oxide synthase (NOS) isoforms, eNOS uncoupling, protein arginine N-methyltransferase (PRMT) 1, and dimethylarginine dimethylaminohydrolase (DDAH) 1 and 2 were tested. All drugs induced a similar control of SBP. Nebivolol did not affect the increased plasma glucose. Unlike atenolol, nebivolol prevented the decrease in plasma insulin, and, like captopril, it reduced plasma lipid contents. Nebivolol ameliorated, to a greater extent than captopril, damages to renal structure and function, which were associated with an improvement in interlobular artery dysfunction. Nebivolol elevated kidney phosphorylation of AMPK, attenuated NOX4 and p22 phox expression and oxidative stress marker levels. Nebivolol increased plasma and renal NO, enhanced expressions of eNOS, p-eNOS and nNOS, and suppressed eNOS uncoupling and iNOS expression. High ADMA in plasma and kidney were decreased by nebivolol through increasing DDAH2 and decreasing PRMT1. Long-term treatment of nebivolol ameliorated diabetic nephropathy, at least in part, via regulation of renal oxidative stress/NO pathway. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

NADPH Oxidase 5 Is a Pro-Contractile Nox Isoform and a Point of Cross-Talk for Calcium and Redox Signaling-Implications in Vascular Function.

PubMed

Montezano, Augusto C; De Lucca Camargo, Livia; Persson, Patrik; Rios, Francisco J; Harvey, Adam P; Anagnostopoulou, Aikaterini; Palacios, Roberto; Gandara, Ana Caroline P; Alves-Lopes, Rheure; Neves, Karla B; Dulak-Lis, Maria; Holterman, Chet E; de Oliveira, Pedro Lagerblad; Graham, Delyth; Kennedy, Christopher; Touyz, Rhian M

2018-06-15

NADPH Oxidase 5 (Nox5) is a calcium-sensitive superoxide-generating Nox. It is present in lower forms and higher mammals, but not in rodents. Nox5 is expressed in vascular cells, but the functional significance remains elusive. Given that contraction is controlled by calcium and reactive oxygen species, both associated with Nox5, we questioned the role of Nox5 in pro-contractile signaling and vascular function. Transgenic mice expressing human Nox5 in a vascular smooth muscle cell-specific manner (Nox5 mice) and Rhodnius prolixus , an arthropod model that expresses Nox5 endogenoulsy, were studied. Reactive oxygen species generation was increased systemically and in the vasculature and heart in Nox5 mice. In Nox5-expressing mice, agonist-induced vasoconstriction was exaggerated and endothelium-dependent vasorelaxation was impaired. Vascular structural and mechanical properties were not influenced by Nox5. Vascular contractile responses in Nox5 mice were normalized by N -acetylcysteine and inhibitors of calcium channels, calmodulin, and endoplasmic reticulum ryanodine receptors, but not by GKT137831 (Nox1/4 inhibitor). At the cellular level, vascular changes in Nox5 mice were associated with increased vascular smooth muscle cell [Ca 2+ ] i , increased reactive oxygen species and nitrotyrosine levels, and hyperphosphorylation of pro-contractile signaling molecules MLC20 (myosin light chain 20) and MYPT1 (myosin phosphatase target subunit 1). Blood pressure was similar in wild-type and Nox5 mice. Nox5 did not amplify angiotensin II effects. In R. prolixus , gastrointestinal smooth muscle contraction was blunted by Nox5 silencing, but not by VAS2870 (Nox1/2/4 inhibitor). Nox5 is a pro-contractile Nox isoform important in redox-sensitive contraction. This involves calcium-calmodulin and endoplasmic reticulum-regulated mechanisms. Our findings define a novel function for vascular Nox5, linking calcium and reactive oxygen species to the pro-contractile molecular machinery in vascular smooth muscle cells. © 2018 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley.

Studying biofuel aerosol evaporation rates with single particle manipulation

NASA Astrophysics Data System (ADS)

Corsetti, S.; Miles, R. E. H.; Reid, J. P.; Kiefer, J.; McGloin, D.

2014-09-01

The significant increase in the air pollution, and the impact on climate change due to the burning of fossil fuel has led to the research of alternative energies. Bio-ethanol obtained from a variety of feedstocks can provide a feasible solution. Mixing bio-ethanol with gasoline leads to a reduction in CO emission and in NOx emissions compared with the use of gasoline alone. However, adding ethanol leads to a change in the fuel evaporation. Here we present a preliminary investigation of evaporation times of single ethanol-gasoline droplets. In particular, we investigated the different evaporation rate of the droplets depending on the variation in the percentage of ethanol inside them. Two different techniques have been used to trap the droplets. One makes use of a 532nm optical tweezers set up, the other of an electrodynamics balance (EDB). The droplets decreasing size was measured using video analysis and elastic light scattering respectively. In the first case measurements were conducted at 293.15 K and ambient humidity. In the second case at 280.5 K and a controlled environment has been preserved by flowing nitrogen into the chamber. Binary phase droplets with a higher percentage of ethanol resulted in longer droplet lifetimes. Our work also highlights the advantages and disadvantages of each technique for such studies. In particular it is challenging to trap droplets with low ethanol content (such as pure gasoline) by the use of EDB. Conversely such droplets are trivial to trap using optical tweezers.

Reduction of nitrogen oxides (NOx) by superalkalis

NASA Astrophysics Data System (ADS)

Srivastava, Ambrish Kumar

2018-03-01

NOx are major air pollutants, having negative impact on environment and consequently, human health. We propose here the single-electron reduction of NOx (x = 1, 2) using superalkalis. We study the interaction of NOx with FLi2, OLi3 and NLi4 superalkalis using density functional and single-point CCSD(T) calculations, which lead to stable superalkali-NOx ionic complexes with negatively charged NOx. This clearly reveals that the NOx can successfully be reduced to NOx- anion due to electron transfer from superalkalis. It has been also noticed that the size of superalkalis plays a crucial in the single-electron reduction of NOx.

Nitrogen stable isotope composition (δ15N) of vehicle-emitted NOx.

PubMed

Walters, Wendell W; Goodwin, Stanford R; Michalski, Greg

2015-02-17

The nitrogen stable isotope ratio of NOx (δ(15)N-NOx) has been proposed as a regional indicator for NOx source partitioning; however, knowledge of δ(15)N values from various NOx emission sources is limited. This study presents a detailed analysis of δ(15)N-NOx emitted from vehicle exhaust, the largest source of anthropogenic NOx. To accomplish this, NOx was collected from 26 different vehicles, including gasoline and diesel-powered engines, using a modification of a NOx collection method used by the United States Environmental Protection Agency, and δ(15)N-NOx was analyzed. The vehicles sampled in this study emitted δ(15)N-NOx values ranging from -19.1 to 9.8‰ that negatively correlated with the emitted NOx concentrations (8.5 to 286 ppm) and vehicle run time because of kinetic isotope fractionation effects associated with the catalytic reduction of NOx. A model for determining the mass-weighted δ(15)N-NOx from vehicle exhaust was constructed on the basis of average commute times, and the model estimates an average value of -2.5 ± 1.5‰, with slight regional variations. As technology improvements in catalytic converters reduce cold-start emissions in the future, it is likely to increase current δ(15)N-NOx values emitted from vehicles.

NADPH oxidase 4 induces cardiac fibrosis and hypertrophy through activating Akt/mTOR and NFκB signaling pathways.

PubMed

Zhao, Qingwei David; Viswanadhapalli, Suryavathi; Williams, Paul; Shi, Qian; Tan, Chunyan; Yi, Xiaolan; Bhandari, Basant; Abboud, Hanna E

2015-02-17

NADPH oxidase 4 (Nox4) has been implicated in cardiac remodeling, but its precise role in cardiac injury remains controversial. Furthermore, little is known about the downstream effector signaling pathways activated by Nox4-derived reactive oxygen species in the myocardium. We investigated the role of Nox4 and Nox4-associated signaling pathways in the development of cardiac remodeling. Cardiac-specific human Nox4 transgenic mice (c-hNox4Tg) were generated. Four groups of mice were studied: (1) control mice, littermates that are negative for hNox4 transgene but Cre positive; (2) c-hNox4 Tg mice; (3) angiotensin II (AngII)-infused control mice; and (4) c-hNox4Tg mice infused with AngII. The c-hNox4Tg mice exhibited an ≈10-fold increase in Nox4 protein expression and an 8-fold increase in the production of reactive oxygen species, and manifested cardiac interstitial fibrosis. AngII infusion to control mice increased cardiac Nox4 expression and induced fibrosis and hypertrophy. The Tg mice receiving AngII exhibited more advanced cardiac remodeling and robust elevation in Nox4 expression, indicating that AngII worsens cardiac injury, at least in part by enhancing Nox4 expression. Moreover, hNox4 transgene and AngII infusion induced the expression of cardiac fetal genes and activated the Akt-mTOR and NFκB signaling pathways. Treatment of AngII-infused c-hNox4Tg mice with GKT137831, a Nox4/Nox1 inhibitor, abolished the increase in oxidative stress, suppressed the Akt-mTOR and NFκB signaling pathways, and attenuated cardiac remodeling. Upregulation of Nox4 in the myocardium causes cardiac remodeling through activating Akt-mTOR and NFκB signaling pathways. Inhibition of Nox4 has therapeutic potential to treat cardiac remodeling. © 2015 American Heart Association, Inc.

NADPH Oxidase 4 Induces Cardiac Fibrosis and Hypertrophy through Activating Akt/mTOR and NFκB Signaling Pathways

PubMed Central

Zhao, Qingwei David; Viswanadhapalli, Suryavathi; Williams, Paul; Shi, Qian; Tan, Chunyan; Yi, Xiaolan; Bhandari, Basant; Abboud, Hanna E.

2015-01-01

Background NADPH oxidase 4 (Nox4) has been implicated in cardiac remodeling, but its precise role in cardiac injury remains controversial. Furthermore, little is known about the downstream effector signaling pathways activated by Nox4-derived ROS in the myocardium. We investigated the role of Nox4 and Nox4 associated signaling pathways in the development of cardiac remodeling. Methods and Results Cardiac-specific human Nox4 transgenic mice (c-hNox4Tg) were generated. Four groups of mice were studied: 1) control mice (CTL): littermates that are negative for hNox4 transgene but Cre positive; 2) c-hNox4 Tg mice; 3) angiotensin II (AngII)-infused CTL mice and 4) c-hNox4Tg mice infused with AngII. The c-hNox4Tg mice exhibited approximately 10-fold increase in Nox4 protein expression and 8-fold increase in the production of reactive oxygen species, and manifested cardiac interstitial fibrosis. AngII-infusion to CTL mice increased cardiac Nox4 expression and induced fibrosis and hypertrophy. The Tg mice receiving AngII exhibited more advanced cardiac remodeling and robust elevation in Nox4 expression, indicating that AngII worsens cardiac injury, at least partially by enhancing Nox4 expression. Moreover, hNox4 transgene and/or AngII-infusion induced the expression of cardiac fetal genes and activated the Akt-mTOR and NFκB signaling pathways. Treatment of AngII-infused c-hNox4Tg mice with GKT137831, a Nox4/Nox1 inhibitor, abolished the increase in oxidative stress, suppressed Akt-mTOR and NFκB signaling pathway and attenuated cardiac remodeling. Conclusion Upregulation of Nox4 in the myocardium causes cardiac remodeling through activating Akt-mTOR and NFκB signaling pathways. Inhibition of Nox4 has therapeutic potential to treat cardiac remodeling. PMID:25589557

Both cardiomyocyte and endothelial cell Nox4 mediate protection against hemodynamic overload-induced remodelling.

PubMed

Zhang, Min; Mongue-Din, Heloise; Martin, Daniel; Catibog, Norman; Smyrnias, Ioannis; Zhang, Xiaohong; Yu, Bin; Wang, Minshu; Brandes, Ralf P; Schröder, Katrin; Shah, Ajay M

2018-03-01

NADPH oxidase-4 (Nox4) is an important reactive oxygen species (ROS) source that is upregulated in the haemodynamically overloaded heart. Our previous studies using global Nox4 knockout (Nox4KO) mice demonstrated a protective role of Nox4 during chronic abdominal aortic banding, involving a paracrine enhancement of myocardial capillary density. However, other authors who studied cardiac-specific Nox4KO mice reported detrimental effects of Nox4 in response to transverse aortic constriction (TAC). It has been speculated that these divergent results are due to cell-specific actions of Nox4 (i.e. cardiomyocyte Nox4 detrimental but endothelial Nox4 beneficial) and/or differences in the model of pressure overload (i.e. abdominal banding vs. TAC). This study aimed to (i) investigate whether the effects of Nox4 on pressure overload-induced cardiac remodelling vary according to the pressure overload model and (ii) compare the roles of cardiomyocyte vs. endothelial cell Nox4. Global Nox4KO mice subjected to TAC developed worse cardiac remodelling and contractile dysfunction than wild-type littermates, consistent with our previous results with abdominal aortic banding. Next, we generated inducible cardiomyocyte-specific Nox4 KO mice (Cardio-Nox4KO) and endothelial-specific Nox4 KO mice (Endo-Nox4KO) and studied their responses to pressure overload. Both Cardio-Nox4KO and Endo-Nox4KO developed worse pressure overload-induced cardiac remodelling and dysfunction than wild-type littermates, associated with significant decrease in protein levels of HIF1α and VEGF and impairment of myocardial capillarization. Cardiomyocyte as well as endothelial cell Nox4 contributes to protection against chronic hemodynamic overload-induced cardiac remodelling, at least in part through common effects on myocardial capillary density. © The Author 2017 Published by Oxford University Press on behalf of the European Society of Cardiology.

System and method for diagnosing EGR performance using NOx sensor

DOEpatents

Mazur, Christopher John

2003-12-23

A method and system for diagnosing a condition of an EGR valve used in an engine system. The EGR valve controls the portion exhaust gases produced by such engine system and fed back to an intake of such engine system. The engine system includes a NOx sensor for measuring NOx in such exhaust. The method includes: determining a time rate of change in NOx measured by the NOx sensor; comparing the determined time rate of change in the measured NOx with a predetermined expected time rate of change in measured NOx; and determining the condition of the EGR valve as a function of such comparison. The method also includes: determining from NOx measured by the NOx sensor and engine operating conditions indications of instances when samples of such measured NOx are greater than an expected maximum NOx level for such engine condition and less than an expected minimum NOx level for such engine condition; and determining the condition of the EGR valve as a function of a statistical analysis of such indications. The method includes determining whether the NOx sensor is faulty and wherein the EGR condition determining includes determining whether the NOx sensor is faulty.

Enhanced xylose fermentation by engineered yeast expressing NADH oxidase through high cell density inoculums.

PubMed

Zhang, Guo-Chang; Turner, Timothy L; Jin, Yong-Su

2017-03-01

Accumulation of reduced byproducts such as glycerol and xylitol during xylose fermentation by engineered Saccharomyces cerevisiae hampers the economic production of biofuels and chemicals from cellulosic hydrolysates. In particular, engineered S. cerevisiae expressing NADPH-linked xylose reductase (XR) and NAD + -linked xylitol dehydrogenase (XDH) produces substantial amounts of the reduced byproducts under anaerobic conditions due to the cofactor difference of XR and XDH. While the additional expression of a water-forming NADH oxidase (NoxE) from Lactococcus lactis in engineered S. cerevisiae with the XR/XDH pathway led to reduced glycerol and xylitol production and increased ethanol yields from xylose, volumetric ethanol productivities by the engineered yeast decreased because of growth defects from the overexpression of noxE. In this study, we introduced noxE into an engineered yeast strain (SR8) exhibiting near-optimal xylose fermentation capacity. To overcome the growth defect caused by the overexpression of noxE, we used a high cell density inoculum for xylose fermentation by the SR8 expressing noxE. The resulting strain, SR8N, not only showed a higher ethanol yield and lower byproduct yields, but also exhibited a high ethanol productivity during xylose fermentation. As noxE overexpression elicits a negligible growth defect on glucose conditions, the beneficial effects of noxE overexpression were substantial when a mixture of glucose and xylose was used. Consumption of glucose led to rapid cell growth and therefore enhanced the subsequent xylose fermentation. As a result, the SR8N strain produced more ethanol and fewer byproducts from a mixture of glucose and xylose than the parental SR8 strain without noxE overexpression. Our results suggest that the growth defects from noxE overexpression can be overcome in the case of fermenting lignocellulose-derived sugars such as glucose and xylose.

Vehicle NOx emission plume isotopic signatures: Spatial variability across the eastern United States

NASA Astrophysics Data System (ADS)

Miller, David J.; Wojtal, Paul K.; Clark, Sydney C.; Hastings, Meredith G.

2017-04-01

On-road vehicle nitrogen oxide (NOx) sources currently dominate the U.S. anthropogenic emission budgets, yet vehicle NOx emissions have uncertain contributions to oxidized nitrogen (N) deposition patterns. Isotopic signatures serve as a potentially valuable observational tool to trace source contributions to NOx chemistry and N deposition, yet in situ emission signatures are underconstrained. We characterize the spatiotemporal variability of vehicle NOx emission isotopic signatures (δ15N-NOx) representative of U.S. vehicle fleet-integrated emission plumes. A novel combination of on-road mobile and stationary urban measurements is performed using a field and laboratory-verified technique for actively capturing NOx in solution to quantify δ15N-NOx at hourly resolution. On-road δ15N-NOx upwind of Providence, RI, ranged from -7 to -3‰. Simultaneous urban background δ15N-NOx observations showed comparable range and variations with on-road measurements, suggesting that vehicles dominate NOx emissions in the Providence area. On-road spatial δ15N-NOx variations of -9 to -2‰ were observed under various driving conditions in six urban metropolitan areas and rural interstate highways during summer and autumn in the U.S. Northeast and Midwest. Although isotopic signatures were insensitive to on-road driving mode variations, statistically significant correlations were found between δ15N-NOx and NOx emission factor extremes associated with heavy diesel emitter contributions. Overall, these results constrain an isotopic signature of fleet-integrated roadway NOx emission plumes, which have important implications for distinguishing vehicle NOx from other sources and tracking emission contributions to NOx chemistry and N deposition.

40 CFR 97.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 97.388 Section 97.388 Protection of Environment... NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in Units § 97.388 CAIR NOX Ozone Season...

40 CFR 97.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 97.388 Section 97.388 Protection of Environment... NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in Units § 97.388 CAIR NOX Ozone Season...

40 CFR 97.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 97.388 Section 97.388 Protection of Environment... NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in Units § 97.388 CAIR NOX Ozone Season...

40 CFR 97.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 97.388 Section 97.388 Protection of Environment... NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in Units § 97.388 CAIR NOX Ozone Season...

40 CFR 97.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 97.388 Section 97.388 Protection of Environment... NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in Units § 97.388 CAIR NOX Ozone Season...

40 CFR 96.52 - NOX Allowance Tracking System responsibilities of NOX authorized account representative.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false NOX Allowance Tracking System... SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS NOX Allowance Tracking System § 96.52 NOX Allowance Tracking System responsibilities of NOX authorized account representative. (a) Following the...

40 CFR 96.52 - NOX Allowance Tracking System responsibilities of NOX authorized account representative.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Allowance Tracking System... SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS NOX Allowance Tracking System § 96.52 NOX Allowance Tracking System responsibilities of NOX authorized account representative. (a) Following the...

Expression and functional significance of NADPH oxidase 5 (Nox5) and its splice variants in human blood vessels

PubMed Central

Pandey, Deepesh; Patel, Anand; Patel, Vijay; Chen, Feng; Qian, Jin; Wang, Yusi; Barman, Scott A.; Venema, Richard C.; Stepp, David W.; Daniel Rudic, R.

2012-01-01

The expression and functional significance of NADPH oxidase 5 (Nox5) and its five isoforms in vascular cells is poorly understood. The goal of this study was to determine whether Nox5-α, -β, -δ, -γ, and -ε (short) are expressed in human blood vessels and evaluate their respective functions. Nox5 mRNA and protein were detected in human blood vessels, cultured human vascular smooth muscle (HVSMC) and endothelium, but not fibroblasts. The most abundant isoforms were α and β, whereas δ and γ were not detected. Nox5-α and -β produced reactive oxygen species (ROS), but -δ, -γ, and -ε were not catalytically active. Coexpression of the active Nox5 isoforms with inactive Nox5 variants suppressed ROS production, and coimmunoprecipitation revealed that Nox5-β binds the inactive ε variant, which may account for reduced ROS production. In HVSMC, angiotensin II, endothelin-1 and TNF-α increased endogenous Nox5 mRNA levels, while adenovirus-mediated overexpression of Nox5 promoted p38 MAPK, JAK2, JNK, and ERK1/2 phosphorylation in endothelial cells (EC), but only increased ERK1/2 phosphorylation in HVSMC. At higher levels of Nox5, there was evidence of increased apoptosis in EC, but not in HVSMC, as detected by the presence of cleaved caspase-3 and cleaved poly(ADP-ribose)polymerase. Although catalytically inactive, Nox5-ε potently activated ERK in HVSMC, and increased expression of Nox5-ε promoted HVSMC proliferation. Nox5 is expressed in human blood vessels. The Nox5-α and -β splice variants are the major isoforms that are expressed and the only variants capable of ROS production. Nox5-ε can inhibit Nox5 activity and activate ERK and HVSMC proliferation. PMID:22427510

Gaseous ligand selectivity of the H-NOX sensor protein from Shewanella oneidensis and comparison to those of other bacterial H-NOXs and soluble guanylyl cyclase.

PubMed

Wu, Gang; Liu, Wen; Berka, Vladimir; Tsai, Ah-Lim

2017-09-01

To delineate the commonalities and differences in gaseous ligand discrimination among the heme-based sensors with Heme Nitric oxide/OXygen binding protein (H-NOX) scaffold, the binding kinetic parameters for gaseous ligands NO, CO, and O 2 , including K D , k on , and k off , of Shewanella oneidensis H-NOX (So H-NOX) were characterized in detail in this study and compared to those of previously characterized H-NOXs from Clostridium botulinum (Cb H-NOX), Nostoc sp. (Ns H-NOX), Thermoanaerobacter tengcongensis (Tt H-NOX), Vibrio cholera (Vc H-NOX), and human soluble guanylyl cyclase (sGC), an H-NOX analogue. The K D (NO) and K D (CO) of each bacterial H-NOX or sGC follow the "sliding scale rule"; the affinities of the bacterial H-NOXs for NO and CO vary in a small range but stronger than those of sGC by at least two orders of magnitude. On the other hand, each bacterial H-NOX exhibits different characters in the stability of its 6c NO complex, reactivity with secondary NO, stability of oxyferrous heme and autoxidation to ferric heme. A facile access channel for gaseous ligands is also identified, implying that ligand access has only minimal effect on gaseous ligand selectivity of H-NOXs or sGC. This comparative study of the binding parameters of the bacterial H-NOXs and sGC provides a basis to guide future new structural and functional studies of each specific heme sensor with the H-NOX protein fold. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Evolution of NADPH Oxidase Inhibitors: Selectivity and Mechanisms for Target Engagement.

PubMed

Altenhöfer, Sebastian; Radermacher, Kim A; Kleikers, Pamela W M; Wingler, Kirstin; Schmidt, Harald H H W

2015-08-10

Oxidative stress, an excess of reactive oxygen species (ROS) production versus consumption, may be involved in the pathogenesis of different diseases. The only known enzymes solely dedicated to ROS generation are nicotinamide adenine dinucleotide phosphate (NADPH) oxidases with their catalytic subunits (NOX). After the clinical failure of most antioxidant trials, NOX inhibitors are the most promising therapeutic option for diseases associated with oxidative stress. Historical NADPH oxidase inhibitors, apocynin and diphenylene iodonium, are un-specific and not isoform selective. Novel NOX inhibitors stemming from rational drug discovery approaches, for example, GKT137831, ML171, and VAS2870, show improved specificity for NADPH oxidases and moderate NOX isoform selectivity. Along with NOX2 docking sequence (NOX2ds)-tat, a peptide-based inhibitor, the use of these novel small molecules in animal models has provided preliminary in vivo evidence for a pathophysiological role of specific NOX isoforms. Here, we discuss whether novel NOX inhibitors enable reliable validation of NOX isoforms' pathological roles and whether this knowledge supports translation into pharmacological applications. Modern NOX inhibitors have increased the evidence for pathophysiological roles of NADPH oxidases. However, in comparison to knockout mouse models, NOX inhibitors have limited isoform selectivity. Thus, their use does not enable clear statements on the involvement of individual NOX isoforms in a given disease. The development of isoform-selective NOX inhibitors and biologicals will enable reliable validation of specific NOX isoforms in disease models other than the mouse. Finally, GKT137831, the first NOX inhibitor in clinical development, is poised to provide proof of principle for the clinical potential of NOX inhibition.

Lake Holloman Recreational Area Development Environmental Assessment

DTIC Science & Technology

2009-08-01

facilities Total daily trips are applied to the following factors depending on the corresponding years. Year 2005 through 2009: VOCE = .016...Trips NOxE = .015 * Trips PM10E = .0022 * Trips COE = .262 * Trips Year 2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E = .0022...Trips COE = .262 * Trips To convert from pounds per day to tons per year: VOC (tons/yr) = VOCE * DPYII/2000 NOx (tons/yr) = NOxE * DPYII/2000

40 CFR 97.52 - NOX Allowance Tracking System responsibilities of NOX authorized account representative.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false NOX Allowance Tracking System... NOX AND SO2 TRADING PROGRAMS NOX Allowance Tracking System § 97.52 NOX Allowance Tracking System... Tracking System account, all submissions to the Administrator pertaining to the account, including, but not...

40 CFR 97.52 - NOX Allowance Tracking System responsibilities of NOX authorized account representative.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Allowance Tracking System... NOX AND SO2 TRADING PROGRAMS NOX Allowance Tracking System § 97.52 NOX Allowance Tracking System... Tracking System account, all submissions to the Administrator pertaining to the account, including, but not...

40 CFR 97.20 - General NOX Budget Trading Program permit requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false General NOX Budget Trading Program... (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.20 General NOX Budget Trading Program permit requirements. (a) For each NOX Budget source...

40 CFR 97.23 - NOX Budget permit contents.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget permit contents. 97.23... (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.23 NOX Budget permit contents. (a) Each NOX Budget permit will contain, in a format prescribed by the permitting...

40 CFR 97.20 - General NOX Budget Trading Program permit requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false General NOX Budget Trading Program... (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.20 General NOX Budget Trading Program permit requirements. (a) For each NOX Budget source...

40 CFR 96.23 - NOX Budget permit contents.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget permit contents. 96.23... (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.23 NOX Budget permit contents. (a) Each NOX Budget permit (including any draft or proposed...

40 CFR 97.21 - Submission of NOX Budget permit applications.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Submission of NOX Budget permit... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.21 Submission of NOX Budget permit applications. (a) Duty to apply. The NOX authorized account...

40 CFR 96.25 - NOX Budget permit revisions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget permit revisions. 96.25... (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.25 NOX Budget permit revisions. (a) For a NOX Budget source with a title V operating permit...

40 CFR 97.24 - NOX Budget permit revisions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget permit revisions. 97.24... (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.24 NOX Budget permit revisions. (a) For a NOX Budget source with a title V operating permit, except as provided...

40 CFR 96.24 - Effective date of initial NOX Budget permit.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Effective date of initial NOX Budget... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.24 Effective date of initial NOX Budget permit. The initial NOX Budget permit...

40 CFR 96.21 - Submission of NOX Budget permit applications.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Submission of NOX Budget permit... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.21 Submission of NOX Budget permit applications. (a) Duty to apply. The NOX...

40 CFR 97.20 - General NOX Budget Trading Program permit requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false General NOX Budget Trading Program... (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.20 General NOX Budget Trading Program permit requirements. (a) For each NOX Budget source...

40 CFR 97.20 - General NOX Budget Trading Program permit requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false General NOX Budget Trading Program... (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.20 General NOX Budget Trading Program permit requirements. (a) For each NOX Budget source...

40 CFR 97.20 - General NOX Budget Trading Program permit requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false General NOX Budget Trading Program... (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.20 General NOX Budget Trading Program permit requirements. (a) For each NOX Budget source...

Sera from cancer patients contain two oscillating ECTO-NOX activities with different period lengths

NASA Technical Reports Server (NTRS)

Wang, Sui; Morre, Dorothy M.; Morre, D. James

2003-01-01

ECTO-NOX protein's are cell surface-associated and growth-related hydroquinone oxidases with both protein disulfide-thiol interchange activity and the capacity to oxidize NAD(P)H. The activities of these ECTO-NOX proteins are not steady state but fluctuate to create a repeating pattern of oscillations. Two forms of ECTO-NOX activities have been distinguished. The constitutive ECTO-NOX (CNOX), is hormone responsive and refractory to quinone-site inhibitors. A tumor-associated NOX (tNOX) is unregulated, refractory to hormones and growth factors and responds to quinone-site inhibitors. CNOX proteins are widely distributed and exhibit oscillations in enzymatic activity with a period length of 24 min. tNOX proteins are cancer specific and exhibit oscillations with a period length of about 22 min. Our findings now demonstrate the presence of the novel oscillating tNOX activity in sera of patients with cancer whereas the constitutive NOX of non-cancer cells is present in sera of both cancer patients and healthy volunteers. We conclude that ECTO-NOX proteins in sera exhibit oscillatory characteristics similar to those of ECTO-NOX forms of the cell surface.

Direct infusion MS-based lipid profiling reveals the pharmacological effects of compound K-reinforced ginsenosides in high-fat diet induced obese mice.

PubMed

Shon, Jong Cheol; Shin, Hwa-Soo; Seo, Yong Ki; Yoon, Young-Ran; Shin, Heungsop; Liu, Kwang-Hyeon

2015-03-25

The serum lipid metabolites of lean and obese mice fed normal or high-fat diets were analyzed via direct infusion nanoelectrospray-ion trap mass spectrometry followed by multivariate analysis. In addition, lipidomic biomarkers responsible for the pharmacological effects of compound K-reinforced ginsenosides (CK), thus the CK fraction, were evaluated in mice fed high-fat diets. The obese and lean groups were clearly discriminated upon principal component analysis (PCA) and partial least-squares discriminant analysis (PLS-DA) score plot, and the major metabolites contributing to such discrimination were triglycerides (TGs), cholesteryl esters (CEs), phosphatidylcholines (PCs), and lysophosphatidylcholines (LPCs). TGs with high total carbon number (>50) and low total carbon number (<50) were negatively and positively associated with high-fat diet induced obesity in mice, respectively. When the CK fraction was fed to obese mice that consumed a high-fat diet, the levels of certain lipids including LPCs and CEs became similar to those of mice fed a normal diet. Such metabolic markers can be used to better understand obesity and related diseases induced by a hyperlipidic diet. Furthermore, changes in the levels of such metabolites can be employed to assess the risk of obesity and the therapeutic effects of obesity management.

40 CFR 97.23 - NOX Budget permit contents.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false NOX Budget permit contents. 97.23 Section 97.23 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.23 NOX Budget permit contents. (a) Each NOX Budget permit...

40 CFR 96.85 - NOX Budget opt-in permit contents.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget opt-in permit contents. 96... (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.85 NOX Budget opt-in permit contents. (a) Each NOX Budget opt-in permit...

40 CFR 97.85 - NOX Budget opt-in permit contents.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false NOX Budget opt-in permit contents. 97... (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins. § 97.85 NOX Budget opt-in permit contents. (a) Each NOX Budget opt-in permit will contain all elements...

Cardiac and renal upregulation of Nox2 and NF-κB and repression of Nox4 and Nrf2 in season- and diabetes-mediated models of vascular oxidative stress in guinea-pig and rat.

PubMed

Gajos-Draus, Anna; Duda, Monika; Beręsewicz, Andrzej

2017-11-01

The superoxide-forming NADPH oxidase homologues, Nox1, Nox2, and Nox5, seem to mediate the pro-atherosclerotic vascular phenotype. The hydrogen peroxide-forming Nox4 afforded vascular protection, likely via NF-E2-related factor-2 (Nrf2) activation and/or Nox2 downregulation in transgenic mice. We hypothesized that oxidative stress in the intact vasculature involves, aside from the upregulation of the superoxide-forming Noxs, the downregulation of the Nox4/Nrf2 pathway. Guinea-pigs and rats were studied either in winter or in summer, and the streptozotocin diabetic rats in winter. Plasma nitrite, and superoxide production by isolated hearts were measured, while frozen tissues served in biochemical analyses. Summer in both species and diabetes in rats downregulated myocardial Nox4 while reciprocally upregulating Nox2 and Nox5 in guinea-pigs, and Nox2 in rats. Simultaneously, myocardial Nrf2 activity and the expression of the Nrf2-directed heme oxygenase-1 and endothelial NO synthase were reduced while activity of the nuclear factor κ B (NF- κ B) and the expression of NF- κ B-directed inducible NO synthase and the vascular cell adhesion molecule-1 were increased. Cardiac superoxide production was increased while plasma nitrite was decreased reciprocally. Analogous disregulation of Noxs, Nrf2, and NF- κ B, occurred in diabetic rat kidneys. Given the diversity of the experimental settings and the uniform pattern of the responses, we speculate that: (1) chronic vascular oxidative stress is a nonspecific (model-, species-, organ-independent) response involving the induction of Nox2 (and Nox5 in guinea-pigs) and the NF- κ B pathway, and the repression of Nox4 and the Nrf2 pathway; and (2) the systems Nox2-NF- κ B and Nox4-Nrf2 regulate each other negatively. © 2017 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.

The Nox1/4 dual inhibitor GKT137831 or Nox4 knockdown inhibits Angiotensin-II-induced adult mouse cardiac fibroblast proliferation and migration. AT1 physically associates with Nox4

PubMed Central

Somanna, Naveen K.; Valente, Anthony J.; Krenz, Maike; Fay, William P.; Delafontaine, Patrice; Chandrasekar, Bysani

2017-01-01

Both oxidative stress and inflammation contribute to chronic hypertension-induced myocardial fibrosis and adverse cardiac remodeling. Here we investigated whether angiotensin (Ang)-II-induced fibroblast proliferation and migration are NADPH oxidase (Nox) 4/ROS and IL-18 dependent. Our results show that the potent induction of mouse cardiac fibroblast (CF) proliferation and migration by Ang-II is markedly attenuated by Nox4 knockdown and the Nox inhibitor DPI. Further, Nox4 knockdown and DPI pre-treatment attenuate Ang-II-induced IL-18, IL-18Rα and collagen expression, and MMP9 activation. While neutralization of IL-18 blunted Ang-II-induced CF proliferation and migration, knockdown of MMP9 attenuated CF migration. The antioxidant NAC and the cell-permeable SOD mimetics Tempol, MnTBAP, and MnTMPyP attenuated oxidative stress and inhibit CF proliferation and migration. The Nox1/Nox4 dual inhibitor GKT137831 also blunted Ang-II-induced H2O2 production and CF proliferation and migration. Further, AT1 binds Nox4, and Ang-II enhanced their physical association. Notably, GKT137831 attnuated the AT1/Nox4 interaction. These results indicate that Ang-II induces CF proliferation and migration in part via Nox4/ROS-dependent IL-18 induction and MMP9 activation, and may involve AT1/Nox4 physical association. Thus, either (i) neutralizing IL-18, (ii) blocking AT1/Nox4 interaction or (iii) use of the Nox1/Nox4 inhibitor GKT137831 may have therapeutic potential in chronic hypertension-induced adverse cardiac remodeling. PMID:26445208

Characterization of N-glycosylation sites on the extracellular domain of NOX1/NADPH oxidase.

PubMed

Matsumoto, Misaki; Katsuyama, Masato; Iwata, Kazumi; Ibi, Masakazu; Zhang, Jia; Zhu, Kai; Nauseef, William M; Yabe-Nishimura, Chihiro

2014-03-01

Extensive evidence demonstrates the pathophysiological importance of NOX1, the catalytic subunit of superoxide-generating enzyme NADPH oxidase, as a source of reactive oxygen species in nonphagocytic cells. However, the biochemical properties of NOX1 have not been extensively characterized due to a lack of specific immunological tools. We used a newly raised NOX1 polyclonal antibody to investigate posttranslational modifications of NOX1 overexpressed in cultured cells and in the colon, where endogenous NOX1 is highly expressed. Immunoblots of lysates from cells expressing NOX1 revealed a doublet of 56 and 60kDa accompanied by a broad band of 60-90kDa. Based on differential sensitivity to glycosidases, the doublet was identified as two high-mannose-type glycoforms of NOX1, whereas the broad band represented NOX1 with complex-type N-linked oligosaccharides. Deglycosylated NOX1 migrated at ~53kDa and N-glycosylation was demonstrated in NOX1 derived from both rat and human. Site-directed mutagenesis identified N-glycosylation sites at Asn(161) and Asn(241) on the extracellular loop of mouse NOX1. Elimination of N-glycosylation on NOX1 did not affect its electron transferase activity, protein stability, targeting to the cell surface, or localization in F-actin-positive membrane protrusions. Taken together, these data identify the two specific sites of N-linked glycosylation of murine NOX1 and demonstrate that they are not required for normal enzyme activity, protein stability, and membrane trafficking. As is true for NOX2, the contribution of glycosylation in NOX1 to its biologic function(s) merits further study. Copyright © 2013 Elsevier Inc. All rights reserved.

Final Environmental Assessment for the Military Family Housing Privatization Initiative Columbus Air Force Base, Mississippi

DTIC Science & Technology

2005-05-03

daily trips are applied to the following factors depending on the corresponding years. Year 2005 through 2009: VOCE = .016 * Trips NOxE = .015...Trips PM10E = .0022 * Trips COE = .262 * Trips Year 2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E = .0022 * Trips COE...262 * Trips To convert from pounds per day to tons per year: VOC (tons/yr) = VOCE * DPYII/2000 NOx (tons/yr) = NOxE * DPYII/2000 PM10 (tons/yr

Final Environmental Assessment for the Okaloosa Regional Airport Expansion at Eglin Air Force Base, FL

DTIC Science & Technology

2006-06-01

construction Total daily trips are then applied to the following factors depending on the corresponding years. Year 2005 through 2009: VOCE ...016 * Trips NOxE = .015 * Trips PM10E = .0022 * Trips COE = .262 * Trips Year 2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E...0022 * Trips COE = .262 * Trips To convert from pounds per day to tons per year: VOC (tons/yr) = VOCE * DPYII/2000 Nox (tons/yr) = NOxE

The role of Nox1 and Nox2 in GPVI-dependent platelet activation and thrombus formation☆

PubMed Central

Walsh, T.G.; Berndt, M.C.; Carrim, N.; Cowman, J.; Kenny, D.; Metharom, P.

2014-01-01

Background Activation of the platelet-specific collagen receptor, glycoprotein (GP) VI, induces intracellular reactive oxygen species (ROS) production; however the relevance of ROS to GPVI-mediated platelet responses remains unclear. Objective The objective of this study was to explore the role of the ROS-producing NADPH oxidase (Nox)1 and 2 complexes in GPVI-dependent platelet activation and collagen-induced thrombus formation. Methods and results ROS production was measured by quantitating changes in the oxidation-sensitive dye, H2DCF-DA, following platelet activation with the GPVI-specific agonist, collagen related peptide (CRP). Using a pharmacological inhibitor specific for Nox1, 2-acetylphenothiazine (ML171), and Nox2 deficient mice, we show that Nox1 is the key Nox homolog regulating GPVI-dependent ROS production. Nox1, but not Nox2, was essential for CRP-dependent thromboxane (Tx)A2 production, which was mediated in part through p38 MAPK signaling; while neither Nox1 nor Nox2 was significantly involved in regulating CRP-induced platelet aggregation/integrin αIIbβ3 activation, platelet spreading, or dense granule and α-granule release (ATP release and P-selectin surface expression, respectively). Ex-vivo perfusion analysis of mouse whole blood revealed that both Nox1 and Nox2 were involved in collagen-mediated thrombus formation at arterial shear. Conclusion Together these results demonstrate a novel role for Nox1 in regulating GPVI-induced ROS production, which is essential for optimal p38 activation and subsequent TxA2 production, providing an explanation for reduced thrombus formation following Nox1 inhibition. PMID:24494191

40 CFR 97.521 - Recordation of TR NOX Ozone Season allowance allocations and auction results.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Recordation of TR NOX Ozone Season... SO2 TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.521 Recordation of TR NOX Ozone Season... Ozone Season source's compliance account the TR NOX Ozone Season allowances allocated to the TR NOX...

40 CFR 97.521 - Recordation of TR NOX Ozone Season allowance allocations and auction results.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Recordation of TR NOX Ozone Season... SO2 TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.521 Recordation of TR NOX Ozone Season... Ozone Season source's compliance account the TR NOX Ozone Season allowances allocated to the TR NOX...

40 CFR 97.521 - Recordation of TR NOX Ozone Season allowance allocations and auction results.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Recordation of TR NOX Ozone Season... SO2 TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.521 Recordation of TR NOX Ozone Season... Ozone Season source's compliance account the TR NOX Ozone Season allowances allocated to the TR NOX...

40 CFR 75.71 - Specific provisions for monitoring NOX and heat input for the purpose of calculating NOX mass...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 17 2014-07-01 2014-07-01 false Specific provisions for monitoring NOX... MONITORING NOX Mass Emissions Provisions § 75.71 Specific provisions for monitoring NOX and heat input for...-diluent continuous emission monitoring system (consisting of a NOX pollutant concentration monitor, an O2...

40 CFR 75.71 - Specific provisions for monitoring NOX and heat input for the purpose of calculating NOX mass...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 17 2012-07-01 2012-07-01 false Specific provisions for monitoring NOX... MONITORING NOX Mass Emissions Provisions § 75.71 Specific provisions for monitoring NOX and heat input for...-diluent continuous emission monitoring system (consisting of a NOX pollutant concentration monitor, an O2...

40 CFR 75.71 - Specific provisions for monitoring NOX and heat input for the purpose of calculating NOX mass...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 17 2013-07-01 2013-07-01 false Specific provisions for monitoring NOX... MONITORING NOX Mass Emissions Provisions § 75.71 Specific provisions for monitoring NOX and heat input for...-diluent continuous emission monitoring system (consisting of a NOX pollutant concentration monitor, an O2...

Identification of NoxD/Pro41 as the homologue of the p22phox NADPH oxidase subunit in fungi.

PubMed

Lacaze, Isabelle; Lalucque, Hervé; Siegmund, Ulrike; Silar, Philippe; Brun, Sylvain

2015-03-01

NADPH oxidases (Nox) are membrane complexes that produce O2(-). Researches in mammals, plants and fungi highlight the involvement of Nox-generated ROS in cell proliferation, differentiation and defense. In mammals, the core enzyme gp91(phox)/Nox2 is associated with p22(phox) forming the flavocytochrome b558 ready for activation by a cytosolic complex. Intriguingly, no homologue of the p22(phox) gene has been found in fungal genomes, questioning how the flavoenzyme forms. Using whole genome sequencing combined with phylogenetic analysis and structural studies, we identify the fungal p22(phox) homologue as being mutated in the Podospora anserina mutant IDC(509). Functional studies show that the fungal p22(phox), PaNoxD, acts along PaNox1, but not PaNox2, a second fungal gp91(phox) homologue. Finally, cytological analysis of functional tagged versions of PaNox1, PaNoxD and PaNoxR shows clear co-localization of PaNoxD and PaNox1 and unravel a dynamic assembly of the complex in the endoplasmic reticulum and in the vacuolar system. © 2014 John Wiley & Sons Ltd.

Scoparone attenuates RANKL-induced osteoclastic differentiation through controlling reactive oxygen species production and scavenging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sang-Hyun; Jang, Hae-Dong, E-mail: haedong@hnu.kr

Scoparone, one of the bioactive components of Artemisia capillaris Thunb, has various biological properties including immunosuppressive, hepatoprotective, anti-allergic, anti-inflammatory, and antioxidant effects. This study aims at evaluating the anti-osteoporotic effect of scoparone and its underlying mechanism in vitro. Scoparone demonstrated potent cellular antioxidant capacity. It was also found that scoparone inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast differentiation and suppressed cathepsin K and tartrate-resistant acid phosphatase (TRAP) expression via c-jun N-terminal kinase (JNK)/extracellular signal-regulated kinase (ERK)/p38-mediated c-Fos–nuclear factor of activated T cells, cytoplasmic 1 (NFATc1) signaling pathway. During osteoclast differentiation, the production of general reactive oxygen speciesmore » (ROS) and superoxide anions was dose-dependently attenuated by scoparone. In addition, scoparone diminished NADPH (nicotinamide adenine dinucleotide phosphate) oxidase 1 (Nox1) expression and activation via the tumor necrosis factor receptor-associated factor 6 (TRAF6)–cSrc–phosphatidylinositol 3-kinase (PI3k) signaling pathway and prevented the disruption of mitochondrial electron transport chain system. Furthermore, scoparone augmented the expression of superoxide dismutase 1 (SOD1) and catalase (CAT). The overall results indicate that the inhibitory effect of scoparone on RANKL-induced osteoclast differentiation is attributed to the suppressive effect on ROS and superoxide anion production by inhibiting Nox1 expression and activation and protecting the mitochondrial electron transport chain system and the scavenging effect of ROS resulting from elevated SOD1 and CAT expression. - Highlights: • Scoparone dose-dependently inhibited RANKL-induced osteoclast differentiation. • Scoparone diminished general ROS and superoxide anions in a dose-dependent manner. • Scoparone inhibited Nox1 expression and activation. • Scoparone prevented the disruption of mitochondrial electron transport chain system. • Scoparone augmented superoxide dismutase and catalase expression.« less

Matrix metalloproteinase-3 causes dopaminergic neuronal death through Nox1-regenerated oxidative stress.

PubMed

Choi, Dong-Hee; Kim, Ji-Hye; Seo, Joo-Ha; Lee, Jongmin; Choi, Wahn Soo; Kim, Yoon-Seong

2014-01-01

In the present study we investigated the interplay between matrix metalloproteinase 3 (MMP3) and NADPH oxidase 1 (Nox1) in the process of dopamine (DA) neuronal death. We found that MMP3 activation causes the induction of Nox1 via mitochondrial reactive oxygen species (ROS) production and subsequently Rac1 activation, eventually leading to Nox1-derived superoxide generation in a rat DA neuronal N27 cells exposed to 6-OHDA. While a MMP3 inhibitor, NNGH, largely attenuated mitochondrial ROS and subsequent Nox1 induction, both apocynin, a putative Nox inhibitor and GKT137831, a Nox1 selective inhibitor failed to reduce 6-OHDA-induced mitochondrial ROS. However, both inhibitors for MMP3 and Nox1 similarly attenuated 6-OHDA-induced N27 cell death. RNAi-mediated selective inhibition of MMP3 or Nox1 showed that knockdown of either MMP3 or Nox1 significantly reduced 6-OHDA-induced ROS generation in N27 cells. While 6-OHDA-induced Nox1 was abolished by MMP3 knockdown, Nox1 knockdown did not alter MMP3 expression. Direct overexpression of autoactivated MMP3 (actMMP3) in N27 cells or in rat substantia nigra (SN) increased expression of Nox1. Selective knockdown of Nox1 in the SN achieved by adeno-associated virus-mediated overexpression of Nox1-specific shRNA largely attenuated the actMMP3-mediated dopaminergic neuronal loss. Furthermore, Nox1 expression was significantly attenuated in Mmp3 null mice treated with N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Together we established novel molecular mechanisms underlying oxidative stress-mediated dopaminergic neuronal death in which MMP3 activation is a key upstream event that leads to mitochondrial ROS, Nox1 induction and eventual dopaminergic neuronal death. Our findings may lead to the development of novel therapeutic approach.

NOx adsorber and method of regenerating same

DOEpatents

Endicott, Dennis L [Peoria, IL; Verkiel, Maarten [Metamora, IL; Driscoll, James J [Dunlap, IL

2007-01-30

New technologies, such as NOx adsorber catalytic converters, are being used to meet increasingly stringent regulations on undesirable emissions, including NOx emissions. NOx adsorbers must be periodically regenerated, which requires an increased fuel consumption. The present disclosure includes a method of regenerating a NOx adsorber within a NOx adsorber catalytic converter. At least one sensor positioned downstream from the NOx adsorber senses, in the downstream exhaust, at least one of NOx, nitrous oxide and ammonia concentrations a plurality of times during a regeneration phase. The sensor is in communication with an electronic control module that includes a regeneration monitoring algorithm operable to end the regeneration phase when a time rate of change of the at least one of NOx, nitrous oxide and ammonia concentrations is after an expected plateau region begins.

REVIEW ARTICLE: Emission measurement techniques for advanced powertrains

NASA Astrophysics Data System (ADS)

Adachi, Masayuki

2000-10-01

Recent developments in high-efficiency low-emission powertrains require the emission measurement technologies to be able to detect regulated and unregulated compounds with very high sensitivity and a fast response. For example, levels of a variety of nitrogen compounds and sulphur compounds should be analysed in real time in order to develop aftertreatment systems to decrease emission of NOx for the lean burning powertrains. Also, real-time information on the emission of particulate matter for the transient operation of diesel engines and direct injection gasoline engines is invaluable. The present paper reviews newly introduced instrumentation for such emission measurement that is demanded for the developments in advanced powertrain systems. They include Fourier transform infrared spectroscopy, mass spectrometry and fast response flame ionization detection. In addition, demands and applications of the fuel reformer developments for fuel cell electric vehicles are discussed. Besides the detection methodologies, sample handling techniques for the measurement of concentrations emitted from low emission vehicles for which the concentrations of the pollutants are significantly lower than the concentrations present in ambient air, are also described.

Highly-basic large-pore zeolite catalysts for NOx reduction at low temperatures

DOEpatents

Penetrante, Bernardino M.; Brusasco, Raymond M.; Merritt, Bernard T.; Vogtlin, George E.

2004-02-03

A high-surface-area (greater than 600 m2/g), large-pore (pore size diameter greater than 6.5 angstroms), basic zeolite having a structure such as an alkali metal cation-exchanged Y-zeolite is employed to convert NO.sub.x contained in an oxygen-rich engine exhaust to N.sub.2 and O.sub.2. Preferably, the invention relates to a two-stage method and apparatus for NO.sub.x reduction in an oxygen-rich engine exhaust such as diesel engine exhaust that includes a plasma oxidative stage and a selective reduction stage. The first stage employs a non-thermal plasma treatment of NO.sub.x gases in an oxygen-rich exhaust and is intended to convert NO to NO.sub.2 in the presence of O.sub.2 and added hydrocarbons. The second stage employs a lean-NO.sub.x catalyst including the basic zeolite at relatively low temperatures to convert such NO.sub.2 to environmentally benign gases that include N.sub.2, CO.sub.2, and H.sub.2 O.

Passive control of thermoacoustic oscillations with adjoint methods

NASA Astrophysics Data System (ADS)

Aguilar, Jose; Juniper, Matthew

2017-11-01

Strict pollutant regulations are driving gas turbine manufacturers to develop devices that operate under lean premixed conditions, which produce less NOx but encourage thermoacoustic oscillations. These are a form of unstable combustion that arise due to the coupling between the acoustic field and the fluctuating heat release in a combustion chamber. In such devices, in which safety is paramount, thermoacoustic oscillations must be eliminated passively, rather than through feedback control. The ideal way to eliminate thermoacoustic oscillations is by subtly changing the shape of the device. To achieve this, one must calculate the sensitivity of each unstable thermoacoustic mode to every geometric parameter. This is prohibitively expensive with standard methods, but is relatively cheap with adjoint methods. In this study we first present low-order network models as a tool to model and study the thermoacoustic behaviour of combustion chambers. Then we compute the continuous adjoint equations and the sensitivities to relevant parameters. With this, we run an optimization routine that modifies the parameters in order to stabilize all the resonant modes of a laboratory combustor rig.

CRISPR-Cas9 Mediated NOX4 Knockout Inhibits Cell Proliferation and Invasion in HeLa Cells.

PubMed

Jafari, Naser; Kim, Hyunju; Park, Rackhyun; Li, Liqing; Jang, Minsu; Morris, Andrew J; Park, Junsoo; Huang, Cai

2017-01-01

Increased expression of NOX4 protein is associated with cancer progression and metastasis but the role of NOX4 in cell proliferation and invasion is not fully understood. We generated NOX4 knockout HeLa cell lines using the CRISPR-Cas9 gene editing system to explore the cellular functions of NOX4. After transfection of CRISPR-Cas9 construct, we performed T7 endonuclease 1 assays and DNA sequencing to generate and identify insertion and deletion of the NOX4 locus. We confirmed the knockout of NOX4 by Western blotting. NOX4 knockout cell lines showed reduced cell proliferation with an increase of sub-G1 cell population and the decrease of S/G2/M population. Moreover, NOX4 deficiency resulted in a dramatic decrease in invadopodium formation and the invasive activity. In addition, NOX4 deficiency also caused a decrease in focal adhesions and cell migration in HeLa cells. These results suggest that NOX4 is required for both efficient proliferation and invasion of HeLa cells.

40 CFR 75.71 - Specific provisions for monitoring NOX and heat input for the purpose of calculating NOX mass...

Code of Federal Regulations, 2010 CFR

2010-07-01

... and heat input for the purpose of calculating NOX mass emissions. 75.71 Section 75.71 Protection of... MONITORING NOX Mass Emissions Provisions § 75.71 Specific provisions for monitoring NOX and heat input for the purpose of calculating NOX mass emissions. (a) Coal-fired units. The owner or operator of a coal...

40 CFR 75.19 - Optional SO2, NOX, and CO2 emissions calculation for low mass emissions (LME) units.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (or group of identical units) equipped with SCR (or SNCR) and uses dry low-NOX technology to control... with add-on NOX emission controls, and for units that use dry low-NOX technology, the owner or operator... mass emissions unit that uses dry low-NOX premix technology to control NOX emissions, proper operation...

Early NADPH oxidase-2 activation is crucial in phenylephrine-induced hypertrophy of H9c2 cells.

PubMed

Hahn, Nynke E; Musters, René J P; Fritz, Jan M; Pagano, Patrick J; Vonk, Alexander B A; Paulus, Walter J; van Rossum, Albert C; Meischl, Christof; Niessen, Hans W M; Krijnen, Paul A J

2014-09-01

Reactive oxygen species (ROS) produced by different NADPH oxidases (NOX) play a role in cardiomyocyte hypertrophy induced by different stimuli, such as angiotensin II and pressure overload. However, the role of the specific NOX isoforms in phenylephrine (PE)-induced cardiomyocyte hypertrophy is unknown. Therefore we aimed to determine the involvement of the NOX isoforms NOX1, NOX2 and NOX4 in PE-induced cardiomyocyte hypertrophy. Hereto rat neonatal cardiomyoblasts (H9c2 cells) were incubated with 100 μM PE to induce hypertrophy after 24 and 48h as determined via cell and nuclear size measurements using digital imaging microscopy, electron microscopy and an automated cell counter. Digital-imaging microscopy further revealed that in contrast to NOX1 and NOX4, NOX2 expression increased significantly up to 4h after PE stimulation, coinciding and co-localizing with ROS production in the cytoplasm as well as the nucleus. Furthermore, inhibition of NOX-mediated ROS production with apocynin, diphenylene iodonium (DPI) or NOX2 docking sequence (Nox2ds)-tat peptide during these first 4h of PE stimulation significantly inhibited PE-induced hypertrophy of H9c2 cells, both after 24 and 48h of PE stimulation. These data show that early NOX2-mediated ROS production is crucial in PE-induced hypertrophy of H9c2 cells. Copyright © 2014 Elsevier Inc. All rights reserved.

NOX EMISSION CONTROL OPTIONS FOR COAL-FIRED ELECTRIC UTILITY BOILERS

EPA Science Inventory

The paper reviews NOx control options for coal-fired electric utility boilers. (NOTE: Acid Rain NOx regulations, the Ozone Transport Commission's NOx Budget Program, revision of the New Source Performance Standards (NSPS) for NOx emissions from utility sources, and Ozone Transpor...

Final Environmental Assessment for Construction of a Precision Measurement Equipment Laboratory Facility on Eglin Air Force Base, FL

DTIC Science & Technology

2006-10-01

daily trips are then applied to the following factors depending on the corresponding years. Year 2005 through 2009: VOCE = .016 * Trips NOxE...015 * Trips PM10E = .0022 * Trips COE = .262 * Trips Year 2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E = .0022 * Trips COE...262 * Trips E = emissions To convert from pounds per day to tons per year: VOC (tons/yr) = VOCE * DPYII/2000 lbs/ton NOx (tons/yr) = NOxE * DPYII

Revised Final Environmental Review for the Construction of a New Base Exchange at Kadena Air Base, Okinawa, Japan

DTIC Science & Technology

2007-05-01

factors depending on the corresponding years. Year 2005 through 2009: VOCE = .016 * Trips NOxE = .015 * Trips PM10E = .0022 * Trips COE = .262...Trips Year 2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E = .0022 * Trips COE = .262 * Trips To convert from pounds per day to...tons per year: VOC (tons/yr) = VOCE * DPYII/2000 Nox (tons/yr) = NOxE * DPYII/2000 PM10(tons/yr) = PM10E * DPYII/2000 CO (tons/yr) = COE * DPYII

Navy Explosive Ordnance Disposal School Master Development Plan for Test Area D-51, Eglin Air Force Base, Florida

DTIC Science & Technology

2008-01-25

depending on the corresponding years. Year 2005 through 2009: VOCE = .016 * Trips NOxE = .015 * Trips PM10E = .0022 * Trips COE = .262 * Trips Year...2010 and beyond: VOCE = .012 * Trips NOxE = .013 * Trips PM10E = .0022 * Trips COE = .262 * Trips To convert from pounds per day to tons per year...VOC (tons/yr) = VOCE * DPYII/2000 NOx (tons/yr) = NOxE * DPYII/2000 PM10 (tons/yr) = PM10E * DPYII/2000 CO (tons/yr) = COE * DPYII/2000

Transcriptional regulation of NADPH oxidase isoforms, Nox1 and Nox4, by nuclear factor-{kappa}B in human aortic smooth muscle cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manea, Adrian, E-mail: adrian.manea@icbp.ro; Tanase, Laurentia I.; Raicu, Monica

Inflammation-induced changes in the activity and expression of NADPH oxidases (Nox) play a key role in atherogenesis. The molecular mechanisms of Nox regulation are scantily elucidated. Since nuclear factor-{kappa}B (NF-{kappa}B) controls the expression of many genes associated to inflammation-related diseases, in this study we have investigated the role of NF-{kappa}B signaling in the regulation of Nox1 and Nox4 transcription in human aortic smooth muscle cells (SMCs). Cultured cells were exposed to tumor necrosis factor-{alpha} (TNF{alpha}), a potent inducer of both Nox and NF-{kappa}B, up to 24 h. Lucigenin-enhanced chemiluminescence and dichlorofluorescein assays, real-time polymerase chain reaction, and Western blot analysismore » showed that inhibition of NF-{kappa}B pathway reduced significantly the TNF{alpha}-dependent up-regulation of Nox-derived reactive oxygen species production, Nox1 and Nox4 expression. In silico analysis indicated the existence of typical NF-{kappa}B elements in the promoters of Nox1 and Nox4. Transient overexpression of p65/NF-{kappa}B significantly increased the promoter activities of both isoforms. Physical interaction of p65/NF-{kappa}B proteins with the predicted sites was demonstrated by chromatin immunoprecipitation assay. These findings demonstrate that NF-{kappa}B is an essential regulator of Nox1- and Nox4-containing NADPH oxidase in SMCs. Elucidation of the complex relationships between NF-{kappa}B and Nox enzymes may lead to a novel pharmacological strategy to reduce both inflammation and oxidative stress in atherosclerosis and its associated complications.« less

Role of NADPH Oxidase-4 in Human Endothelial Progenitor Cells

PubMed Central

Hakami, Nora Y.; Ranjan, Amaresh K.; Hardikar, Anandwardhan A.; Dusting, Greg J.; Peshavariya, Hitesh M.

2017-01-01

Introduction: Endothelial progenitor cells (EPCs) display a unique ability to promote angiogenesis and restore endothelial function in injured blood vessels. NADPH oxidase 4 (NOX4)-derived hydrogen peroxide (H2O2) serves as a signaling molecule and promotes endothelial cell proliferation and migration as well as protecting against cell death. However, the role of NOX4 in EPC function is not completely understood. Methods: EPCs were isolated from human saphenous vein and mammary artery discarded during bypass surgery. NOX4 gene and protein expression in EPCs were measured by real time-PCR and Western blot analysis respectively. NOX4 gene expression was inhibited using an adenoviral vector expressing human NOX4 shRNA (Ad-NOX4i). H2O2 production was measured by Amplex red assay. EPC migration was evaluated using a transwell migration assay. EPC proliferation and viability were measured using trypan blue counts. Results: Inhibition of NOX4 using Ad-NOX4i reduced Nox4 gene and protein expression as well as H2O2 formation in EPCs. Inhibition of NOX4-derived H2O2 decreased both proliferation and migration of EPCs. Interestingly, pro-inflammatory cytokine tumor necrosis factor alpha (TNFα) decreased NOX4 expression and reduced survival of EPCs. However, the survival of EPCs was further diminished by TNF-α in NOX4-knockdown cells, suggesting that NOX4 has a protective role in EPCs. Conclusion: These findings suggest that NOX4-type NADPH oxidase is important for proliferation and migration functions of EPCs and protects against pro-inflammatory cytokine induced EPC death. These properties of NOX4 may facilitate the efficient function of EPCs which is vital for successful neovascularization. PMID:28386230

NOX2-mediated arterial dysfunction in smokers: acute effect of dark chocolate.

PubMed

Loffredo, Lorenzo; Carnevale, Roberto; Perri, Ludovica; Catasca, Elisa; Augelletti, Teresa; Cangemi, Roberto; Albanese, Fabiana; Piccheri, Cristina; Nocella, Cristina; Pignatelli, Pasquale; Violi, Francesco

2011-11-01

Cocoa seems to exert artery dilatation via oxidative stress inhibition but the mechanism is still unclear. To investigate whether in smokers, dark chocolate elicits artery dilatation via down-regulation of NOX2, the catalytic core of NADPH oxidase. Flow-mediated dilatation (FMD), oxidative stress (as assessed by urinary isoprostanes excretion), nitric oxide generation (as assessed by serum levels of nitrite/nitrate (NOx)), NOX2 activity (as assessed by blood levels of soluble NOX2 derived peptide (sNOX2-dp)) and serum epicatechin were studied in 20 smokers and 20 healthy subjects (HS) in a crossover, single-blind study. Patients were randomly allocated to 40 g dark chocolate (>85% cocoa) or 40 g of milk chocolate (≤35% cocoa). FMD, urinary isoprostanes, NOx and sNOX2-dp were assessed at baseline and 2 h after chocolate ingestion. Smokers had lower FMD and NOx and higher sNOX2-dp compared to HS. After dark chocolate intake, urinary isoprostanes and sNOX2-dp significantly decreased and FMD and NOx significantly increased in smokers but not in HS. No changes of the above variables were observed after milk chocolate intake. Multiple linear regression analysis showed that in smokers the only independent predictive variable associated with a change in FMD was a change in sNOX2-dp. Serum epicatechin increased in either group only after dark chocolate intake, reaching values higher than 0.1 μM. Platelets from smokers (n=5), but not from HS (n=5), showed lower p47(phox) translocation to platelet membrane and higher NOx when incubated with 0.1-10 μM epicatechin. Results suggest that in smokers, cocoa enhances artery dilatation by lowering of NOX2 activation.

MENU OF NOX EMISSION CONTROL OPTIONS FOR COAL-FIRED ELECTRIC UTILITY BOILERS

EPA Science Inventory

The paper reviews NOx control options for coal-fired electric utility boilers. (NOTE: Acid Rain NOx regulations, the Ozone Transport Commission's NOx Budget Program, revision of the New Source Performance Standards (NSPS) for NOx emissions from utility sources, and Ozone Transpor...

40 CFR Appendix A to Subpart IIIi... - States With Approved State Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in...

Code of Federal Regulations, 2010 CFR

2010-07-01

... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units A Appendix A to Subpart IIII of Part...) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units 1. The following States have State...

40 CFR Appendix A to Subpart IIIi... - States With Approved State Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units A Appendix A to Subpart IIII of Part...) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units 1. The following States have State...

40 CFR Appendix A to Subpart IIIi... - States With Approved State Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in...

Code of Federal Regulations, 2012 CFR

2012-07-01

... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units A Appendix A to Subpart IIII of Part...) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units 1. The following States have State...

40 CFR Appendix A to Subpart IIIi... - States With Approved State Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in...

Code of Federal Regulations, 2013 CFR

2013-07-01

... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units A Appendix A to Subpart IIII of Part...) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units 1. The following States have State...

40 CFR Appendix A to Subpart IIIi... - States With Approved State Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in...

Code of Federal Regulations, 2011 CFR

2011-07-01

... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units A Appendix A to Subpart IIII of Part...) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season Opt-in... Implementation Plan Revisions Concerning CAIR NOX Ozone Season Opt-in Units 1. The following States have State...

Agriculture is a major source of NOx pollution in California

PubMed Central

Almaraz, Maya; Bai, Edith; Wang, Chao; Trousdell, Justin; Conley, Stephen; Faloona, Ian; Houlton, Benjamin Z.

2018-01-01

Nitrogen oxides (NOx = NO + NO2) are a primary component of air pollution—a leading cause of premature death in humans and biodiversity declines worldwide. Although regulatory policies in California have successfully limited transportation sources of NOx pollution, several of the United States’ worst–air quality districts remain in rural regions of the state. Site-based findings suggest that NOx emissions from California’s agricultural soils could contribute to air quality issues; however, a statewide estimate is hitherto lacking. We show that agricultural soils are a dominant source of NOx pollution in California, with especially high soil NOx emissions from the state’s Central Valley region. We base our conclusion on two independent approaches: (i) a bottom-up spatial model of soil NOx emissions and (ii) top-down airborne observations of atmospheric NOx concentrations over the San Joaquin Valley. These approaches point to a large, overlooked NOx source from cropland soil, which is estimated to increase the NOx budget by 20 to 51%. These estimates are consistent with previous studies of point-scale measurements of NOx emissions from the soil. Our results highlight opportunities to limit NOx emissions from agriculture by investing in management practices that will bring co-benefits to the economy, ecosystems, and human health in rural areas of California. PMID:29399630

STAT5A-mediated NOX5-L expression promotes the proliferation and metastasis of breast cancer cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dho, So Hee; Radioisotope Research Division, Department of Research Reactor Utilization, Korea Atomic Energy Research Institute, Daejeon 305-353; Kim, Ji Young

NADPH oxidase (NOX) generates reactive oxygen species (ROS) and has been suggested to mediate cell proliferation in some cancers. Here, we show that an increase in the expression of NOX5 long form (NOX5-L) is critical for tumor progression in breast tumor tissues. Immunostaining of clinical samples indicated that NOX5 was overexpressed in 41.1% of breast ductal carcinoma samples. NOX5-L depletion consistently suppressed cell proliferation, invasion, and migration in vitro. Antibody-mediated neutralization of NOX5-L attenuated tumor progression in a mouse xenograft model. Promoter analysis revealed that NOX5-L expression is regulated by STAT5A in breast cancer cells. Based on our novel findings,more » we suggest that inhibition of NOX5-L may be a promising therapeutic strategy that exerts anti-cancer effects via the modulation of ROS-mediated cell signaling. - Highlights: • The ROS-generating protein, NOX5-L, determines cellular proliferation and metastasis in subset of breast tumor. • Tumor growth was attenuated by the treatment of anti-NOX5-L antibody in a xenograft model. • NOX5-L expression is transcriptionally regulated by STAT5A in breast cancer cells.« less

Differential Expression of NADPH Oxidases Depends on Skeletal Muscle Fiber Type in Rats.

PubMed

Loureiro, Adriano César Carneiro; do Rêgo-Monteiro, Igor Coutinho; Louzada, Ruy A; Ortenzi, Victor Hugo; de Aguiar, Angélica Ponte; de Abreu, Ewerton Sousa; Cavalcanti-de-Albuquerque, João Paulo Albuquerque; Hecht, Fabio; de Oliveira, Ariclécio Cunha; Ceccatto, Vânia Marilande; Fortunato, Rodrigo S; Carvalho, Denise P

2016-01-01

NADPH oxidases (NOX) are important sources of reactive oxygen species (ROS) in skeletal muscle, being involved in excitation-contraction coupling. Thus, we aimed to investigate if NOX activity and expression in skeletal muscle are fiber type specific and the possible contribution of this difference to cellular oxidative stress. Oxygen consumption rate, NOX activity and mRNA levels, and the activity of catalase (CAT), glutathione peroxidase (GPX), and superoxide dismutase (SOD), as well as the reactive protein thiol levels, were measured in the soleus (SOL), red gastrocnemius (RG), and white gastrocnemius (WG) muscles of rats. RG showed higher oxygen consumption flow than SOL and WG, while SOL had higher oxygen consumption than WG. SOL showed higher NOX activity, as well as NOX2 and NOX4 mRNA levels, antioxidant enzymatic activities, and reactive protein thiol contents when compared to WG and RG. NOX activity and NOX4 mRNA levels as well as antioxidant enzymatic activities were higher in RG than in WG. Physical exercise increased NOX activity in SOL and RG, specifically NOX2 mRNA levels in RG and NOX4 mRNA levels in SOL. In conclusion, we demonstrated that NOX activity and expression differ according to the skeletal muscle fiber type, as well as antioxidant defense.

Mycoplasma bovis NADH oxidase functions as both a NADH oxidizing and O2 reducing enzyme and an adhesin.

PubMed

Zhao, Gang; Zhang, Hui; Chen, Xi; Zhu, Xifang; Guo, Yusi; He, Chenfei; Anwar Khan, Farhan; Chen, Yingyu; Hu, Changmin; Chen, Huanchun; Guo, Aizhen

2017-03-03

Mycoplasma bovis causes considerable economic losses in the cattle industry worldwide. In mycoplasmal infections, adhesion to the host cell is of the utmost importance. In this study, the amino acid sequence of NOX was predicted to have enzymatic domains. The nox gene was then cloned and expressed in Escherichia coli. The enzymatic activity of recombinant NOX (rNOX) was confirmed based on its capacity to oxidize NADH to NAD + and reduce O 2 to H 2 O 2 . The adherence of rNOX to embryonic bovine lung (EBL) cells was confirmed with confocal laser scanning microscopy, enzyme-linked immunosorbent assay, and flow cytometry. Both preblocking EBL cells with purified rNOX and preneutralizing M. bovis with polyclonal antiserum to rNOX significantly reduced the adherence of M. bovis to EBL cells. Mycoplasma bovis NOX- expressed a truncated NOX protein at a level 10-fold less than that of the wild type. The capacities of M. bovis NOX- for cell adhesion and H 2 O 2 production were also significantly reduced. The rNOX was further used to pan phage displaying lung cDNA library and fibronectin was determined to be potential ligand. In conclusion, M. bovis NOX functions as both an active NADH oxidase and adhesin, and is therefore a potential virulence factor.

Identification of stable cytotoxic factors in the gas phase extract of cigarette smoke and pharmacological characterization of their cytotoxicity.

PubMed

Noya, Yoichi; Seki, Koh-Ichi; Asano, Hiroshi; Mai, Yosuke; Horinouchi, Takahiro; Higashi, Tsunehito; Terada, Koji; Hatate, Chizuru; Hoshi, Akimasa; Nepal, Prabha; Horiguchi, Mika; Kuge, Yuji; Miwa, Soichi

2013-12-06

Smoking is a major risk factor for atherosclerotic vascular diseases, but the mechanism for its genesis is unknown. We have recently shown that the gas phase of cigarette smoke (nicotine- and tar-free cigarette smoke extract; CSE) likely to reach the systemic circulation contains stable substances which cause cytotoxicity like plasma membrane damage and cell death in cultured cells, and also that the plasma membrane damage is caused through sequential activation of protein kinase C (PKC) and NADPH oxidase (NOX) and the resulting generation of reactive oxygen species (PKC/NOX-dependent mechanism), whereas cell death is caused through PKC/NOX-dependent and -independent mechanisms. To identify these stable substances, the CSE was prepared by passing the main-stream smoke of 10 cigarettes through a Cambridge glass fiber filter, trapping of the smoke in a vessel cooled at -80°C, and subsequent dissolution in 10ml of water. The CSE was fractionated into nine fractions using reversed-phase HPLC, and each fraction was screened for cytotoxicity in cultured cells, using propidium iodide uptake assay for cell membrane damage and MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium] reduction assay for cell viability. The cytotoxicity was positive in two of the nine fractions (Fr2 and Fr5). After extraction of the active fractions into dichloromethane, GC/MS analysis identified 2-cyclopenten-1-one (CPO) in Fr5 but none in Fr2. After derivatization of the active fractions with O-(2,3,4,5,6-pentafluorobenzyl) hydroxylamine hydrochloride, GC/MS analysis identified acrolein, acetone and propionaldehyde in Fr2, and methyl vinyl ketone (MVK) in Fr5. After 4-h incubation, authentic acrolein and MVK induced concentration-dependent cytotoxicity with EC50 values of 75.9±8.2 and 47.0±8.0μM (mean±SEM; n=3), respectively, whereas acetone, propionaldehyde and CPO were without effect. However, after 24-h incubation, CPO induced concentration-dependent cytotoxicity with an EC50 value of 264.0±16.9μM (n=3). The concentrations of acrolein, MVK and CPO in the CSE were 3368±334, 2429±123 and 392.9±31.8μM (n=4), respectively, which were higher than the cytotoxic concentrations. The cytotoxicity of acrolein and MVK consisted of plasma membrane damage and decreased cell viability: the plasma membrane damage was totally prevented by treatment with an inhibitor of PKC or NOX, whereas the decreased cell viability was only partially prevented by these inhibitors. The cytotoxicity of CPO consisted only of decreased cell viability, which was totally resistant to these inhibitors. These results show that acrolein and MVK are responsible for the acute cytotoxicity of the CSE through PKC/NOX-dependent and -independent mechanisms, whereas CPO is responsible for the delayed cytotoxicity of the CSE through a PKC/NOX-independent mechanism. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Angiotensin II stimulates superoxide production in the thick ascending limb by activating NOX4

PubMed Central

Hong, Nancy J.; Garvin, Jeffrey L.

2012-01-01

Angiotensin II (ANG II) stimulates production of superoxide (O2−) by NADPH oxidase (NOX) in medullary thick ascending limbs (TALs). There are three isoforms of the catalytic subunit (NOX1, 2, and 4) known to be expressed in the kidney. We hypothesized that NOX2 mediates ANG II-induced O2− production by TALs. To test this, we measured NOX1, 2, and 4 mRNA and protein by RT-PCR and Western blot in TAL suspensions from rats and found three catalytic subunits expressed in the TAL. We measured O2− production using a lucigenin-based assay. To assess the contribution of NOX2, we measured ANG II-induced O2− production in wild-type and NOX2 knockout mice (KO). ANG II increased O2− production by 346 relative light units (RLU)/mg protein in the wild-type mice (n = 9; P < 0.0007 vs. control). In the knockout mice, ANG II increased O2− production by 290 RLU/mg protein (n = 9; P < 0.007 vs. control). This suggests that NOX2 does not contribute to ANG II-induced O2− production (P < 0.6 WT vs. KO). To test whether NOX4 mediates the effect of ANG II, we selectively decreased NOX4 expression in rats using an adenovirus that expresses NOX4 short hairpin (sh)RNA. Six to seven days after in vivo transduction of the kidney outer medulla, NOX4 mRNA was reduced by 77%, while NOX1 and NOX2 mRNA was unaffected. In control TALs, ANG II stimulated O2− production by 96%. In TALs transduced with NOX4 shRNA, ANG II-stimulated O2− production was not significantly different from the baseline. We concluded that NOX4 is the main catalytic isoform of NADPH oxidase that contributes to ANG II-stimulated O2− production by TALs. PMID:22875785

Characterization of NOx emission in the suburbs of Tokyo based on simultaneous and real-time observations of atmospheric Ox and NOx

NASA Astrophysics Data System (ADS)

Matsumoto, J.

2013-12-01

Nitrogen oxides, NOx (NO, NO2), and volatile organic compounds, VOCs, are important as precursors of photochemical oxidants (tropospheric ozone, O3). To predict and control photochemical oxidants, NOx emission should be captured precisely. In addition, the ratio of NO2/NOx in the exhaust gas is also important as the initial balance between NO and NO2 in the atmosphere. Monitoring the NO2/NOx ratio in the exhaust gases is essential. Especially, the influence of the NOx emission on the real atmosphere should be explored. However, conversion reactions among NO, NO2 and O3 are typically in the time scale of minutes. The NO2/NOx ratio can change rapidly just after emission. Real-time observations of these compounds in the second time scale are essential. In view of photochemical oxidant, near emission sources of NO, ozone concentration can be easily perturbed by reaction with locally emitted NO. As an index of oxidant, the sum of O3 and NO2 (Ox = O3 + NO2) is useful. In this study, a simultaneous and real-time analyzer of atmospheric Ox and NOx has been developed utilizing the dual NO2 detectors based on laser-induced fluorescence technique (LIF), and characterization of NOx emission was explored through the observations of Ox and NOx in the suburbs of Tokyo. The dual LIF detectors consisted of one laser head, two LIF cells, and one common vacuum pump. As the Ox monitor, the excess NO was added to the sample and O3 was converted to NO2, and then the sum of O3 and NO2 in the sample was quantified at the 1st LIF cell. As the NOx monitor, the excess O3 was added to the sample and NO was converted to NO2, and then the sum of NO and NO2 in the sample was quantified at the 2nd LIF cell. Both the ';Ox' and ';NOx' channels in the dual LIF analyzer were simultaneously monitoring Ox and NOx in the sample air, respectively. The temporal resolution of observed data was 1 s. Typical conversion efficiencies of O3 and NO to NO2 were more than 0.98. The lower detection limits were 0.1 ppbv for Ox and 0.5 ppbv for NOx (60-s integration, S/N = 3). The observation test in the suburbs of Tokyo was conducted in April 2013 at Tokorozawa Campus, Waseda University. During the campaign, 48 cases of ';NOx spikes', for which NOx levels significantly varied in the second time scale due to local NOx emission, were captured. NO2/NOx ratio in the exhaust gas was estimated as the slope of regression line between 1-s series data of Ox and those of NOx observed during each spike. The average of acquired NO2/NOx ratio was 0.10. Thus, as a result of observations of real atmosphere, the present NO2/NOx ratio in the exhaust gases in the suburbs of Tokyo was 0.10 as average, which was mainly due to exhausts of automobiles. However, when the individual cases were considered, NO2/NOx could vary from 0.00 to 0.30. Such a wide range of NO2/NOx ratio may be due to (1) difference of source types (eg. automobiles, power generator) and (2) difference of conditions of sources (eg. engines, filters of exhaust). For example, NO2/NOx ratio for hybrid electric vehicles may be different from those for conventional cars. When diffusion of such new model cars can change NOx emission in near future, the present method of simultaneous and real-time monitoring of Ox and NOx in the atmosphere can be useful and promising for characterization of NOx emission.

Exhaust particle characterization for lean and stoichiometric DI vehicles operating on ethanol-gasoline blends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Storey, John Morse; Barone, Teresa L; Thomas, John F

2012-01-01

Gasoline direct injection (GDI) engines can offer better fuel economy and higher performance over their port fuel-injected (PFI) counterparts, and are now appearing in increasingly more U.S. and European vehicles. Small displacement, turbocharged GDI engines are replacing large displacement engines, particularly in light-duty trucks and sport utility vehicles, in order for manufacturers to meet the U.S. fuel economy standards for 2016. Furthermore, lean-burn GDI engines can offer even higher fuel economy than stoichiometric GDI engines and have overcome challenges associated with cost-effective aftertreatment for NOx control. Along with changes in gasoline engine technology, fuel composition may increase in ethanol contentmore » beyond the current 10% due to the recent EPA waiver allowing 15% ethanol. In addition, the Renewable Fuels Standard passed as part of the 2007 Energy Independence and Security Act (EISA) mandates the use of biofuels in upcoming years. GDI engines are of environmental concern due to their high particulate matter (PM) emissions relative to port-fuel injected (PFI) gasoline vehicles; widespread market penetration of GDI vehicles may result in additional PM from mobile sources at a time when the diesel contribution is declining. In this study, we characterized particulate emissions from a European certified lean-burn GDI vehicle operating on ethanol-gasoline blends. Particle mass and particle number concentration emissions were measured for the Federal Test Procedure urban driving cycle (FTP 75) and the more aggressive US06 driving cycle. Particle number-size distributions and organic to elemental carbon ratios (OC/EC) were measured for 30 MPH and 80 MPH steady-state operation. In addition, particle number concentration was measured during wide open throttle accelerations (WOTs) and gradual accelerations representative of the FTP 75. Fuels included certification gasoline and 10% (E10) and 20% (E20) ethanol blends from the same supplier. The particle mass emissions were approximately 3 and 7 mg/mile for the FTP75 and US06, respectively, with lower emissions for the ethanol blends. The data are compared to a previous study on a U.S.-legal stoichiometric GDI vehicle operating on the same ethanol blends. The lean-burn GDI vehicle emitted a higher number of particles, but had an overall smaller average size. Particle number per mile decreased with increasing ethanol content for the transient tests. For the 30 and 80 mph tests, particle number concentration decreased with increasing ethanol content, although the shape of the particle size distribution remained the same. Engine-out OC/EC ratios were highest for the stoichiometric GDI vehicle with E20, but tailpipe OC/EC ratios were similar for all vehicles.« less

40 CFR 96.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Trading Program. 96.186 Section 96.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.186 Withdrawal from CAIR NOX Annual Trading...

40 CFR 97.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins. § 97.86 Withdrawal from NOX Budget Trading Program. (a) Requesting withdrawal. To...

40 CFR 97.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Trading Program. 97.186 Section 97.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Opt-In Units § 97.186 Withdrawal from CAIR NOX Annual Trading Program. Except as provided...

40 CFR 97.22 - Information requirements for NOX Budget permit applications.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Budget permit applications. 97.22 Section 97.22 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.22 Information requirements for NOX Budget permit applications. A complete NOX Budget permit...

40 CFR 97.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins. § 97.86 Withdrawal from NOX Budget Trading Program. (a) Requesting withdrawal. To...

40 CFR 97.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Trading Program. 97.186 Section 97.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Opt-In Units § 97.186 Withdrawal from CAIR NOX Annual Trading Program. Except as provided...

40 CFR 96.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Trading Program. 96.186 Section 96.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.186 Withdrawal from CAIR NOX Annual Trading...

40 CFR 96.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Trading Program. 96.186 Section 96.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO 2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.186 Withdrawal from CAIR NOX Annual Trading...

40 CFR 97.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Trading Program. 97.186 Section 97.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Opt-In Units § 97.186 Withdrawal from CAIR NOX Annual Trading Program. Except as provided...

40 CFR 96.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Trading Program. 96.186 Section 96.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.186 Withdrawal from CAIR NOX Annual Trading...

40 CFR 97.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Trading Program. 97.186 Section 97.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Opt-In Units § 97.186 Withdrawal from CAIR NOX Annual Trading Program. Except as provided...

40 CFR 96.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Trading Program. 96.186 Section 96.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Opt-in Units § 96.186 Withdrawal from CAIR NOX Annual Trading...

40 CFR 97.186 - Withdrawal from CAIR NOX Annual Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Trading Program. 97.186 Section 97.186 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Opt-In Units § 97.186 Withdrawal from CAIR NOX Annual Trading Program. Except as provided...

40 CFR 75.70 - NOX mass emissions provisions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 17 2012-07-01 2012-07-01 false NOX mass emissions provisions. 75.70... (CONTINUED) CONTINUOUS EMISSION MONITORING NOX Mass Emissions Provisions § 75.70 NOX mass emissions... subpart to the extent that compliance is required by an applicable State or federal NOX mass emission...

Plasma Levels of Nitrite and Nitrate in Early and Recent Classes of Fish

PubMed Central

Williams, Donna A; Flood, Mary H; Lewis, Debra A; Miller, Virginia M; Krause, William J

2008-01-01

The stable metabolite of nitric oxide in plasma is NOx, the sum of nitrite plus nitrate. Measures of plasma NOx may provide information about the nitric oxide tonus of the entire endothelium including capillary microvessels. Although data are available for mammalian species, plasma NOx measurements in early vertebrate species are scarce. The purpose of this study was to test the hypothesis that plasma NOx would be similar to the NOx in the water environment for fish in early classes (Agnatha and Chondrichthye) and would exceed water NOx levels in the known nitrite-sensitive fish (Osteichthye). Plasma samples were obtained from 18 species of adult fish (n = 167) and from their housing or natural water environment. NOx was measured by using chemiluminescence. Plasma NOx was detected in all species and ranged from 0.5 nmol/ml (skate) to 453.9 nmol/ml (shortnose gar). Average plasma NOx was significantly higher in sea lamprey than in Atlantic hagfish whereas that of little skate was 3-fold lower than in spiny dogfish shark. Plasma NOx differed significantly among early bony fish (paddlefish, pallid sturgeon, gar) yet was similar among modern bony fish, with the exception of rainbow trout. Plasma NOx reflected water NOx in only 2 species (hagfish and shark), and levels did not coincide with nitrite sensitivity. This study provides an expanded comparative view of plasma NOx levels across 3 groups of early fish. The data obtained suggest a nitric oxide system in early and modern fish. PMID:19004368

ROS-induced ROS release orchestrated by Nox4, Nox2, and mitochondria in VEGF signaling and angiogenesis.

PubMed

Kim, Young-Mee; Kim, Seok-Jo; Tatsunami, Ryosuke; Yamamura, Hisao; Fukai, Tohru; Ushio-Fukai, Masuko

2017-06-01

Reactive oxygen species (ROS) derived from NADPH oxidase (NOX) and mitochondria play a critical role in growth factor-induced switch from a quiescent to an angiogenic phenotype in endothelial cells (ECs). However, how highly diffusible ROS produced from different sources can coordinate to stimulate VEGF signaling and drive the angiogenic process remains unknown. Using the cytosol- and mitochondria-targeted redox-sensitive RoGFP biosensors with real-time imaging, here we show that VEGF stimulation in human ECs rapidly increases cytosolic RoGFP oxidation within 1 min, followed by mitochondrial RoGFP oxidation within 5 min, which continues at least for 60 min. Silencing of Nox4 or Nox2 or overexpression of mitochondria-targeted catalase significantly inhibits VEGF-induced tyrosine phosphorylation of VEGF receptor type 2 (VEGFR2-pY), EC migration and proliferation at the similar extent. Exogenous hydrogen peroxide (H 2 O 2 ) or overexpression of Nox4, which produces H 2 O 2 , increases mitochondrial ROS (mtROS), which is prevented by Nox2 siRNA, suggesting that Nox2 senses Nox4-derived H 2 O 2 to promote mtROS production. Mechanistically, H 2 O 2 increases S36 phosphorylation of p66Shc, a key mtROS regulator, which is inhibited by siNox2, but not by siNox4. Moreover, Nox2 or Nox4 knockdown or overexpression of S36 phosphorylation-defective mutant p66Shc(S36A) inhibits VEGF-induced mtROS, VEGFR2-pY, EC migration, and proliferation. In summary, Nox4-derived H 2 O 2 in part activates Nox2 to increase mtROS via pSer36-p66Shc, thereby enhancing VEGFR2 signaling and angiogenesis in ECs. This may represent a novel feed-forward mechanism of ROS-induced ROS release orchestrated by the Nox4/Nox2/pSer36-p66Shc/mtROS axis, which drives sustained activation of angiogenesis signaling program. Copyright © 2017 the American Physiological Society.

Variation of radiative forcings and global warming potentials from regional aviation NOx emissions

NASA Astrophysics Data System (ADS)

Skowron, Agnieszka; Lee, David S.; De León, Ruben R.

2015-03-01

The response to hemispherical and regional aircraft NOx emissions is explored by using two climate metrics: radiative forcing (RF) and Global Warming Potential (GWP). The global chemistry transport model, MOZART-3 CTM, is applied in this study for a series of incremental aircraft NOx emission integrations to different regions. It was found that the sensitivity of chemical responses per unit emission rate from regional aircraft NOx emissions varies with size of aircraft NOx emission rate and that climate metric values decrease with increasing aircraft NOx emission rates, except for Southeast Asia. Previous work has recognized that aircraft NOx GWPs may vary regionally. However, the way in which these regional GWPs are calculated are critical. Previous studies have added a fixed amount of NOx to different regions. This approach can heavily bias the results of a regional GWP because of the well-established sensitivity of O3 production to background NOx whereby the Ozone Production Efficiency (OPE) is greater at small background NOx. Thus, even a small addition of NOx in a clean-air area can produce a large O3 response. Using this 'fixed addition' method of 0.035 Tg(N) yr-1, results in the greatest effect observed for North Atlantic and Brazil, ∼10.0 mW m-2/Tg(N) yr-1. An alternative 'proportional approach' is also taken that preserves the subtle balance of local NOx-O3-CH4 systems with the existing emission patterns of aircraft and background NOx, whereby a proportional amount of aircraft NOx, 5% (N) yr-1, is added to each region in order to determine the response. This results in the greatest effect observed for North Pacific that with its net NOx RF of 23.7 mW m-2/Tg(N) yr-1 is in contrast with the 'fixed addition' method. For determining regional NOx GWPs, it is argued that the 'proportional' approach gives more representative results. However, a constraint of both approaches is that the regional GWP determined is dependent on the relative global emission pattern, so if that changes in the future, the regional NOx GWP will change.

Molecular evolution of Phox-related regulatory subunits for NADPH oxidase enzymes

PubMed Central

Kawahara, Tsukasa; Lambeth, J David

2007-01-01

Background The reactive oxygen-generating NADPH oxidases (Noxes) function in a variety of biological roles, and can be broadly classified into those that are regulated by subunit interactions and those that are regulated by calcium. The prototypical subunit-regulated Nox, Nox2, is the membrane-associated catalytic subunit of the phagocyte NADPH-oxidase. Nox2 forms a heterodimer with the integral membrane protein, p22phox, and this heterodimer binds to the regulatory subunits p47phox, p67phox, p40phox and the small GTPase Rac, triggering superoxide generation. Nox-organizer protein 1 (NOXO1) and Nox-activator 1 (NOXA1), respective homologs of p47phox and p67phox, together with p22phox and Rac, activate Nox1, a non-phagocytic homolog of Nox2. NOXO1 and p22phox also regulate Nox3, whereas Nox4 requires only p22phox. In this study, we have assembled and analyzed amino acid sequences of Nox regulatory subunit orthologs from vertebrates, a urochordate, an echinoderm, a mollusc, a cnidarian, a choanoflagellate, fungi and a slime mold amoeba to investigate the evolutionary history of these subunits. Results Ancestral p47phox, p67phox, and p22phox genes are broadly seen in the metazoa, except for the ecdysozoans. The choanoflagellate Monosiga brevicollis, the unicellular organism that is the closest relatives of multicellular animals, encodes early prototypes of p22phox, p47phox as well as the earliest known Nox2-like ancestor of the Nox1-3 subfamily. p67phox- and p47phox-like genes are seen in the sea urchin Strongylocentrotus purpuratus and the limpet Lottia gigantea that also possess Nox2-like co-orthologs of vertebrate Nox1-3. Duplication of primordial p47phox and p67phox genes occurred in vertebrates, with the duplicated branches evolving into NOXO1 and NOXA1. Analysis of characteristic domains of regulatory subunits suggests a novel view of the evolution of Nox: in fish, p40phox participated in regulating both Nox1 and Nox2, but after the appearance of mammals, Nox1 (but not Nox2) became independent of p40phox. In the fish Oryzias latipes, a NOXO1 ortholog retains an autoinhibitory region that is characteristic of mammalian p47phox, and this was subsequently lost from NOXO1 in later vertebrates. Detailed amino acid sequence comparisons identified both putative key residues conserved in characteristic domains and previously unidentified conserved regions. Also, candidate organizer/activator proteins in fungi and amoeba are identified and hypothetical activation models are suggested. Conclusion This is the first report to provide the comprehensive view of the molecular evolution of regulatory subunits for Nox enzymes. This approach provides clues for understanding the evolution of biochemical and physiological functions for regulatory-subunit-dependent Nox enzymes. PMID:17900370

Effects of NOx and SO2 on the secondary organic aerosol formation from photooxidation of α-pinene and limonene

NASA Astrophysics Data System (ADS)

Zhao, Defeng; Schmitt, Sebastian H.; Wang, Mingjin; Acir, Ismail-Hakki; Tillmann, Ralf; Tan, Zhaofeng; Novelli, Anna; Fuchs, Hendrik; Pullinen, Iida; Wegener, Robert; Rohrer, Franz; Wildt, Jürgen; Kiendler-Scharr, Astrid; Wahner, Andreas; Mentel, Thomas F.

2018-02-01

Anthropogenic emissions such as NOx and SO2 influence the biogenic secondary organic aerosol (SOA) formation, but detailed mechanisms and effects are still elusive. We studied the effects of NOx and SO2 on the SOA formation from the photooxidation of α-pinene and limonene at ambient relevant NOx and SO2 concentrations (NOx: < 1to 20 ppb, SO2: < 0.05 to 15 ppb). In these experiments, monoterpene oxidation was dominated by OH oxidation. We found that SO2 induced nucleation and enhanced SOA mass formation. NOx strongly suppressed not only new particle formation but also SOA mass yield. However, in the presence of SO2 which induced a high number concentration of particles after oxidation to H2SO4, the suppression of the mass yield of SOA by NOx was completely or partly compensated for. This indicates that the suppression of SOA yield by NOx was largely due to the suppressed new particle formation, leading to a lack of particle surface for the organics to condense on and thus a significant influence of vapor wall loss on SOA mass yield. By compensating for the suppressing effect on nucleation of NOx, SO2 also compensated for the suppressing effect on SOA yield. Aerosol mass spectrometer data show that increasing NOx enhanced nitrate formation. The majority of the nitrate was organic nitrate (57-77 %), even in low-NOx conditions (< ˜ 1 ppb). Organic nitrate contributed 7-26 % of total organics assuming a molecular weight of 200 g mol-1. SOA from α-pinene photooxidation at high NOx had a generally lower hydrogen to carbon ratio (H / C), compared to low NOx. The NOx dependence of the chemical composition can be attributed to the NOx dependence of the branching ratio of the RO2 loss reactions, leading to a lower fraction of organic hydroperoxides and higher fractions of organic nitrates at high NOx. While NOx suppressed new particle formation and SOA mass formation, SO2 can compensate for such effects, and the combining effect of SO2 and NOx may have an important influence on SOA formation affected by interactions of biogenic volatile organic compounds (VOCs) with anthropogenic emissions.

Automated, High-resolution Mobile Collection System for the Nitrogen Isotopic Analysis of NOx.

PubMed

Wojtal, Paul K; Miller, David J; O'Conner, Mary; Clark, Sydney C; Hastings, Meredith G

2016-12-20

Nitrogen oxides (NOx = NO + NO2) are a family of atmospheric trace gases that have great impact on the environment. NOx concentrations directly influence the oxidizing capacity of the atmosphere through interactions with ozone and hydroxyl radicals. The main sink of NOx is the formation and deposition of nitric acid, a component of acid rain and a bioavailable nutrient. NOx is emitted from a mixture of natural and anthropogenic sources, which vary in space and time. The collocation of multiple sources and the short lifetime of NOx make it challenging to quantitatively constrain the influence of different emission sources and their impacts on the environment. Nitrogen isotopes of NOx have been suggested to vary amongst different sources, representing a potentially powerful tool to understand the sources and transport of NOx. However, previous methods of collecting atmospheric NOx integrate over long (week to month) time spans and are not validated for the efficient collection of NOx in relevant, diverse field conditions. We report on a new, highly efficient field-based system that collects atmospheric NOx for isotope analysis at a time resolution between 30 min and 2 hr. This method collects gaseous NOx in solution as nitrate with 100% efficiency under a variety of conditions. Protocols are presented for collecting air in urban settings under both stationary and mobile conditions. We detail the advantages and limitations of the method and demonstrate its application in the field. Data from several deployments are shown to 1) evaluate field-based collection efficiency by comparisons with in situ NOx concentration measurements, 2) test the stability of stored solutions before processing, 3) quantify in situ reproducibility in a variety of urban settings, and 4) demonstrate the range of N isotopes of NOx detected in ambient urban air and on heavily traveled roadways.

Native Alanine Substitution in the Glycine Hinge Modulates Conformational Flexibility of Heme Nitric Oxide/Oxygen (H-NOX) Sensing Proteins.

PubMed

Hespen, Charles W; Bruegger, Joel J; Guo, Yirui; Marletta, Michael A

2018-06-15

Heme nitric oxide/oxygen sensing (H-NOX) domains are direct NO sensors that regulate a variety of biological functions in both bacteria and eukaryotes. Previous work on H-NOX proteins has shown that upon NO binding, a conformational change occurs along two glycine residues on adjacent helices (termed the glycine hinge). Despite the apparent importance of the glycine hinge, it is not fully conserved in all H-NOX domains. Several H-NOX sensors from the family Flavobacteriaceae contain a native alanine substitution in one of the hinge residues. In this work, the effect of the increased steric bulk within the Ala-Gly hinge on H-NOX function was investigated. The hinge in Kordia algicida OT-1 ( Ka H-NOX) is composed of A71 and G145. Ligand-binding properties and signaling function for this H-NOX were characterized. The variant A71G was designed to convert the hinge region of Ka H-NOX to the typical Gly-Gly motif. In activity assays with its cognate histidine kinase (HnoK), the wild type displayed increased signal specificity compared to A71G. Increasing titrations of unliganded A71G gradually inhibits HnoK autophosphorylation, while increasing titrations of unliganded wild type H-NOX does not inhibit HnoK. Crystal structures of both wild type and A71G Ka H-NOX were solved to 1.9 and 1.6 Å, respectively. Regions of H-NOX domains previously identified as involved in protein-protein interactions with HnoK display significantly higher b-factors in A71G compared to wild-type H-NOX. Both biochemical and structural data indicate that the hinge region controls overall conformational flexibility of the H-NOX, affecting NO complex formation and regulation of its HnoK.

40 CFR 97.524 - Compliance with TR NOX Ozone Season emissions limitation.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.524 Compliance with TR NOX Ozone Season emissions limitation. (a) Availability for deduction for compliance. TR NOX Ozone Season allowances are available to be...

40 CFR 97.360 - Submission of CAIR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Submission of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Transfers § 97.360 Submission of CAIR NOX Ozone Season allowance transfers. A CAIR authorized account representative seeking recordation of a CAIR NOX Ozone Season allowance...

40 CFR 97.524 - Compliance with TR NOX Ozone Season emissions limitation.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.524 Compliance with TR NOX Ozone Season emissions limitation. (a) Availability for deduction for compliance. TR NOX Ozone Season allowances are available to be...

40 CFR 97.522 - Submission of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Submission of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.522 Submission of TR NOX Ozone Season allowance transfers. (a) An authorized account representative seeking recordation of a TR NOX Ozone Season allowance...

40 CFR 96.342 - CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false CAIR NOX Ozone Season allowance... IMPLEMENTATION PLANS CAIR NOX Ozone Season Allowance Allocations § 96.342 CAIR NOX Ozone Season allowance allocations. (a)(1) The baseline heat input (in mmBtu) used with respect to CAIR NOX Ozone Season allowance...

40 CFR 97.341 - Timing requirements for CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Timing requirements for CAIR NOX Ozone... TRADING PROGRAMS CAIR NOX Ozone Season Allowance Allocations § 97.341 Timing requirements for CAIR NOX Ozone Season allowance allocations. (a) The Administrator will determine by order the CAIR NOX Ozone...

40 CFR 97.341 - Timing requirements for CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Timing requirements for CAIR NOX Ozone... TRADING PROGRAMS CAIR NOX Ozone Season Allowance Allocations § 97.341 Timing requirements for CAIR NOX Ozone Season allowance allocations. (a) The Administrator will determine by order the CAIR NOX Ozone...

40 CFR 97.525 - Compliance with TR NOX Ozone Season assurance provisions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.525 Compliance with TR NOX Ozone Season assurance provisions. (a) Availability for deduction. TR NOX Ozone Season allowances are available to be deducted for...

40 CFR 97.523 - Recordation of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Recordation of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.523 Recordation of TR NOX Ozone Season allowance transfers... NOX Ozone Season allowance transfer that is correctly submitted under § 97.522, the Administrator will...

40 CFR 96.342 - CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false CAIR NOX Ozone Season allowance... IMPLEMENTATION PLANS CAIR NOX Ozone Season Allowance Allocations § 96.342 CAIR NOX Ozone Season allowance allocations. (a)(1) The baseline heat input (in mmBtu) used with respect to CAIR NOX Ozone Season allowance...

40 CFR 97.360 - Submission of CAIR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Submission of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Transfers § 97.360 Submission of CAIR NOX Ozone Season allowance transfers. A CAIR authorized account representative seeking recordation of a CAIR NOX Ozone Season allowance...

40 CFR 97.341 - Timing requirements for CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Timing requirements for CAIR NOX Ozone... TRADING PROGRAMS CAIR NOX Ozone Season Allowance Allocations § 97.341 Timing requirements for CAIR NOX Ozone Season allowance allocations. (a) The Administrator will determine by order the CAIR NOX Ozone...

40 CFR 97.341 - Timing requirements for CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Timing requirements for CAIR NOX Ozone... TRADING PROGRAMS CAIR NOX Ozone Season Allowance Allocations § 97.341 Timing requirements for CAIR NOX Ozone Season allowance allocations. (a) The Administrator will determine by order the CAIR NOX Ozone...

40 CFR 96.342 - CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false CAIR NOX Ozone Season allowance... IMPLEMENTATION PLANS CAIR NOX Ozone Season Allowance Allocations § 96.342 CAIR NOX Ozone Season allowance allocations. (a)(1) The baseline heat input (in mmBtu) used with respect to CAIR NOX Ozone Season allowance...

40 CFR 97.522 - Submission of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Submission of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.522 Submission of TR NOX Ozone Season allowance transfers. (a) An authorized account representative seeking recordation of a TR NOX Ozone Season allowance...

40 CFR 96.342 - CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false CAIR NOX Ozone Season allowance... IMPLEMENTATION PLANS CAIR NOX Ozone Season Allowance Allocations § 96.342 CAIR NOX Ozone Season allowance allocations. (a)(1) The baseline heat input (in mmBtu) used with respect to CAIR NOX Ozone Season allowance...

40 CFR 97.522 - Submission of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Submission of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.522 Submission of TR NOX Ozone Season allowance transfers. (a) An authorized account representative seeking recordation of a TR NOX Ozone Season allowance...

40 CFR 97.360 - Submission of CAIR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Submission of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Transfers § 97.360 Submission of CAIR NOX Ozone Season allowance transfers. A CAIR authorized account representative seeking recordation of a CAIR NOX Ozone Season allowance...

40 CFR 96.342 - CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false CAIR NOX Ozone Season allowance... IMPLEMENTATION PLANS CAIR NOX Ozone Season Allowance Allocations § 96.342 CAIR NOX Ozone Season allowance allocations. (a)(1) The baseline heat input (in mmBtu) used with respect to CAIR NOX Ozone Season allowance...

40 CFR 97.360 - Submission of CAIR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Submission of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Transfers § 97.360 Submission of CAIR NOX Ozone Season allowance transfers. A CAIR authorized account representative seeking recordation of a CAIR NOX Ozone Season allowance...

40 CFR 97.341 - Timing requirements for CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Timing requirements for CAIR NOX Ozone... TRADING PROGRAMS CAIR NOX Ozone Season Allowance Allocations § 97.341 Timing requirements for CAIR NOX Ozone Season allowance allocations. (a) The Administrator will determine by order the CAIR NOX Ozone...

40 CFR 97.523 - Recordation of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Recordation of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.523 Recordation of TR NOX Ozone Season allowance transfers... NOX Ozone Season allowance transfer that is correctly submitted under § 97.522, the Administrator will...

40 CFR 97.524 - Compliance with TR NOX Ozone Season emissions limitation.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.524 Compliance with TR NOX Ozone Season emissions limitation. (a) Availability for deduction for compliance. TR NOX Ozone Season allowances are available to be...

40 CFR 97.360 - Submission of CAIR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Submission of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Transfers § 97.360 Submission of CAIR NOX Ozone Season allowance transfers. A CAIR authorized account representative seeking recordation of a CAIR NOX Ozone Season allowance...

40 CFR 97.523 - Recordation of TR NOX Ozone Season allowance transfers.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Recordation of TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.523 Recordation of TR NOX Ozone Season allowance transfers... NOX Ozone Season allowance transfer that is correctly submitted under § 97.522, the Administrator will...

40 CFR 97.525 - Compliance with TR NOX Ozone Season assurance provisions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.525 Compliance with TR NOX Ozone Season assurance provisions. (a) Availability for deduction. TR NOX Ozone Season allowances are available to be deducted for...

40 CFR 97.525 - Compliance with TR NOX Ozone Season assurance provisions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Compliance with TR NOX Ozone Season... TR NOX Ozone Season Trading Program § 97.525 Compliance with TR NOX Ozone Season assurance provisions. (a) Availability for deduction. TR NOX Ozone Season allowances are available to be deducted for...

40 CFR 96.20 - General NOX Budget trading program permit requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false General NOX Budget trading program... (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.20 General NOX Budget trading program permit requirements. (a...

40 CFR 97.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.120 General CAIR NOX Annual Trading Program permit requirements. (a) For...

40 CFR 96.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.120 General CAIR NOX Annual Trading Program permit...

40 CFR 96.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.86 Withdrawal from NOX Budget Trading Program. (a) Requesting...

40 CFR 96.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.86 Withdrawal from NOX Budget Trading Program. (a) Requesting...

40 CFR 96.20 - General NOX Budget trading program permit requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false General NOX Budget trading program... (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.20 General NOX Budget trading program permit requirements. (a...

40 CFR 96.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.86 Withdrawal from NOX Budget Trading Program. (a) Requesting...

40 CFR 96.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.120 General CAIR NOX Annual Trading Program permit...

40 CFR 97.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins § 97.86 Withdrawal from NOX Budget Trading Program. (a) Requesting withdrawal. To withdraw...

40 CFR 97.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.120 General CAIR NOX Annual Trading Program permit requirements. (a) For...

40 CFR 96.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO 2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.86 Withdrawal from NOX Budget Trading Program. (a) Requesting...

40 CFR 97.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.120 General CAIR NOX Annual Trading Program permit requirements. (a) For...

40 CFR 97.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.120 General CAIR NOX Annual Trading Program permit requirements. (a) For...

40 CFR 96.20 - General NOX Budget trading program permit requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false General NOX Budget trading program... (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.20 General NOX Budget trading program permit requirements. (a...

40 CFR 96.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO 2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.120 General CAIR NOX Annual Trading Program permit...

40 CFR 96.20 - General NOX Budget trading program permit requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false General NOX Budget trading program... (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.20 General NOX Budget trading program permit requirements. (a...

40 CFR 97.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins § 97.86 Withdrawal from NOX Budget Trading Program. (a) Requesting withdrawal. To withdraw...

40 CFR 97.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins § 97.86 Withdrawal from NOX Budget Trading Program. (a) Requesting withdrawal. To withdraw...

40 CFR 96.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.120 General CAIR NOX Annual Trading Program permit...

40 CFR 96.86 - Withdrawal from NOX Budget Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Withdrawal from NOX Budget Trading... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.86 Withdrawal from NOX Budget Trading Program. (a) Requesting...

40 CFR 96.20 - General NOX Budget trading program permit requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false General NOX Budget trading program... (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO 2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.20 General NOX Budget trading program permit requirements. (a...

40 CFR 97.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Permits § 97.120 General CAIR NOX Annual Trading Program permit requirements. (a) For...

40 CFR 96.120 - General CAIR NOX Annual Trading Program permit requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false General CAIR NOX Annual Trading... AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.120 General CAIR NOX Annual Trading Program permit...

Functions of Two Types of NADH Oxidases in Energy Metabolism and Oxidative Stress of Streptococcus mutans

PubMed Central

Higuchi, Masako; Yamamoto, Yuji; Poole, Leslie B.; Shimada, Mamoru; Sato, Yutaka; Takahashi, Nobuhiro; Kamio, Yoshiyuki

1999-01-01

We have previously identified two distinct NADH oxidases corresponding to H2O2-forming oxidase (Nox-1) and H2O-forming oxidase (Nox-2) induced in Streptococcus mutans. Sequence analyses indicated a strong similarity between Nox-1 and AhpF, the flavoprotein component of Salmonella typhimurium alkyl hydroperoxide reductase; an open reading frame upstream of nox-1 also showed homology to AhpC, the direct peroxide-reducing component of S. typhimurium alkyl hydroperoxide reductase. To determine their physiological functions in S. mutans, we constructed knockout mutants of Nox-1, Nox-2, and/or the AhpC homologue; we verified that Nox-2 plays an important role in energy metabolism through the regeneration of NAD+ but Nox-1 contributes negligibly. The Nox-2 mutant exhibited greatly reduced aerobic growth on mannitol, whereas there was no significant effect of aerobiosis on the growth on mannitol of the other strains or growth on glucose of any of the strains. Although the Nox-2 mutants grew well on glucose aerobically, the end products of glucose fermentation by the Nox-2 mutant were substantially shifted to higher ratios of lactic acid to acetic acid compared with wild-type cells. The resistance to cumene hydroperoxide of Escherichia coli TA4315 (ahpCF-defective mutant) transformed with pAN119 containing both nox-1 and ahpC genes was not only restored but enhanced relative to that of E. coli K-12 (parent strain), indicating a clear function for Nox-1 as part of an alkyl hydroperoxide reductase system in vivo in combination with AhpC. Surprisingly, the Nox-1 and/or AhpC deficiency had no effect on the sensitivity of S. mutans to cumene hydroperoxide and H2O2, implying that the existence of some other antioxidant system(s) independent of Nox-1 in S. mutans compensates for the deficiency. PMID:10498705

NOX2 As a Target for Drug Development: Indications, Possible Complications, and Progress

PubMed Central

Diebold, Becky A.; Smith, Susan M.E.; Li, Yang

2015-01-01

Abstract Significance: NOX2 is important for host defense, and yet is implicated in a large number of diseases in which inflammation plays a role in pathogenesis. These include acute and chronic lung inflammatory diseases, stroke, traumatic brain injury, and neurodegenerative diseases, including Alzheimer's and Parkinson's Diseases. Recent Advances: Recent drug development programs have targeted several NOX isoforms that are implicated in a variety of diseases. The focus has been primarily on NOX4 and NOX1 rather than on NOX2, due, in part, to concerns about possible immunosuppressive side effects. Nevertheless, NOX2 clearly contributes to the pathogenesis of many inflammatory diseases, and its inhibition is predicted to provide a novel therapeutic approach. Critical Issues: Possible side effects that might arise from targeting NOX2 are discussed, including the possibility that such inhibition will contribute to increased infections and/or autoimmune disorders. The state of the field with regard to existing NOX2 inhibitors and targeted development of novel inhibitors is also summarized. Future Directions: NOX2 inhibitors show particular promise for the treatment of inflammatory diseases, both acute and chronic. Theoretical side effects include pro-inflammatory and autoimmune complications and should be considered in any therapeutic program, but in our opinion, available data do not indicate that they are sufficiently likely to eliminate NOX2 as a drug target, particularly when weighed against the seriousness of many NOX2-related indications. Model studies demonstrating efficacy with minimal side effects are needed to encourage future development of NOX2 inhibitors as therapeutic agents. Antioxid. Redox Signal. 23, 375–405. PMID:24512192

Method And Apparatus For Regenerating Nox Adsorbers

DOEpatents

Driscoll, J. Joshua; Endicott, Dennis L.; Faulkner, Stephen A.; Verkiel, Maarten

2006-03-28

Methods and apparatuses for regenerating a NOx adsorber coupled with an exhaust of an engine. An actuator drives a throttle valve to a first position when regeneration of the NOx adsorber is desired. The first position is a position that causes the regeneration of the NOx adsorber. An actuator drives the throttle valve to a second position while regeneration of the NOx adsorber is still desired. The second position being a position that is more open than the first position and operable to regenerate a NOx adsorber.

Self-Protection Mechanism of Hexagonal WO3-Based DeNOx Catalysts against Alkali Poisoning.

PubMed

Zheng, Li; Zhou, Meijuan; Huang, Zhiwei; Chen, Yaxin; Gao, Jiayi; Ma, Zhen; Chen, Jianmin; Tang, Xingfu

2016-11-01

A good catalyst for efficiently controlling NO x emissions often demands strong resistance against alkali poisoning. Although the traditional ion-exchange model, based on acid-base reactions of alkalis with Brønsted acid sites, has been established over the past two decades, it is difficult to be used as a guideline to develop such an alkali-resistant catalyst. Here we establish a self-protection mechanism of deNO x catalysts against alkali poisoning by systematically studying the intrinsic nature of alkali resistance of V 2 O 5 /HWO (HWO = hexagonal WO 3 ) that shows excellent resistance to alkali poisoning in selective catalytic reduction of NO x with NH 3 (SCR). Synchrotron X-ray diffraction and absorption spectroscopies demonstrate that V 2 O 5 /HWO has spatially separated catalytically active sites (CASs) and alkali-trapping sites (ATSs). During the SCR process, ATSs spontaneously trap alkali ions such as K + , even if alkali ions initially block CASs, thus releasing CASs to realize the self-protection against alkali poisoning. X-ray photoelectron spectra coupled with theoretical calculations indicate that the electronic interaction between the alkali ions and ATSs with an energy saving is the driving force of the self-protection. This work provides a strategy to design alkali-resistant deNO x catalysts.

An assessment of cruise NOx emissions of short-haul commercial flights

NASA Astrophysics Data System (ADS)

Turgut, Enis T.; Usanmaz, Oznur

2017-12-01

Cruise NOx emissions of aircraft are an important input parameter for studies investigating climate change due to their ability to alter the concentrations of certain trace gases, such as ozone, methane, and hydroxyl in the atmosphere, and to induce positive radiative forcing. Therefore, it is of importance to minimize estimation errors on NOx emitted from aircraft engines at high altitude. In this study, the cruise NOx emissions of a frequently-used narrow-bodied aircraft type operating domestic flights in Turkey, are quantified based on numerous actual flight, actual emissions and actual meteorological data. The overall average cruise NOx emissions index is found to be ∼10 g/kg fuel. In addition, newly-developed parameters of the aircraft cruise NOx footprint and NOx intensity are calculated to be 0.5 g/pa-NM and ∼60 g/NM, respectively. Regarding the effects of flight parameters on cruise NOx emissions, while there is a distinct increase in NOx parameters with an increase in aircraft mass, this may differ for altitude. The results reveal that the NOx emissions index tends to increase slightly by 1-2%, particularly above 28,000 ft, whereas NOx intensity decreases at a rate of 2.4-2.7% per 2000 ft of cruise altitude increase.

High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study.

PubMed

He, Chao; Li, Jiaqiang; Ma, Zhilei; Tan, Jianwei; Zhao, Longqing

2015-09-01

Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%-83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level. Copyright © 2015. Published by Elsevier B.V.

A new method and application for determining the nitrogen isotopic composition of NOx

NASA Astrophysics Data System (ADS)

Hastings, M. G.; Miller, D. J.; Wojtal, P.; O'Connor, M.

2015-12-01

Atmospheric nitrogen oxides (NOx = NO + NO2) play key roles in atmospheric chemistry, air quality, and radiative forcing, and contribute to nitric acid deposition. Sources of NOx include both natural and anthropogenic emissions, which vary significantly in space and time. NOx isotopic signatures offer a potentially valuable tool to trace source impacts on atmospheric chemistry and regional acid deposition. Previous work on NOx isotopic signatures suggests large ranges in values, even from the same emission source, as well as overlapping ranges amongst different sources, making it difficult to use the isotopic composition as a quantitative tracer of source influences. These prior measurements have utilized a variety of methods for collecting the NOx as nitrate or nitrite for isotopic analysis, and testing of some of these methods (including active and passive collections) reveal inconsistencies in efficiency of collection, as well as issues related to changes in conditions such as humidity, temperature, and NOx fluxes. A recently developed method allows for accurately measuring the nitrogen isotopic composition of NOx (NOx = NO + NO2) after capturing the NOx in a potassium permanganate/sodium hydroxide solution as nitrate (Fibiger et al., Anal. Chem., 2014). The method has been thoroughly tested in the laboratory and field, and efficiently collects NO and NO2 under a variety of conditions. There are several advantages to collecting NOx actively, including the ability to collect over minutes to hourly time scales, and the ability to collect in environments with highly variable NOx sources and concentrations. Challenges include a nitrate background present in potassium permanganate (solid and liquid forms), accurately deriving ambient NOx concentrations based upon flow rate and solution concentrations above this variable background, and potential interferences from other nitrogen species. This method was designed to collect NOx in environments with very different emission source loadings in an effort to isotopically characterize NOx sources. Results to date suggest very different values, and less variability than previous work, particularly for vehicle emissions. Ultimately, we aim to determine whether the influence of NOx sources can be quantitatively tracked in the environment.

40 CFR 96.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Withdrawal from CAIR NOX Ozone Season... STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season...

40 CFR 97.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Withdrawal from CAIR NOX Ozone Season... CAIR NOX Ozone Season Opt-in Units § 97.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season opt-in unit may withdraw...

40 CFR 97.353 - Recordation of CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Recordation of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Tracking System § 97.353 Recordation of CAIR NOX Ozone Season allowance allocations. (a) By September 30, 2007, the Administrator will record in the CAIR NOX Ozone Season sources...

40 CFR 97.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Withdrawal from CAIR NOX Ozone Season... CAIR NOX Ozone Season Opt-in Units § 97.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season opt-in unit may withdraw...

40 CFR 96.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Withdrawal from CAIR NOX Ozone Season... STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season...

40 CFR 97.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Withdrawal from CAIR NOX Ozone Season... CAIR NOX Ozone Season Opt-in Units § 97.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season opt-in unit may withdraw...

40 CFR 96.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Withdrawal from CAIR NOX Ozone Season... STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season...

40 CFR 97.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Withdrawal from CAIR NOX Ozone Season... CAIR NOX Ozone Season Opt-in Units § 97.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season opt-in unit may withdraw...

40 CFR 97.511 - Timing requirements for TR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false Timing requirements for TR NOX Ozone... TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.511 Timing requirements for TR NOX Ozone Season allowance allocations. (a) Existing units. (1) TR NOX Ozone Season allowances are allocated, for the control...

40 CFR 97.353 - Recordation of CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Recordation of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Tracking System § 97.353 Recordation of CAIR NOX Ozone Season allowance allocations. (a) By September 30, 2007, the Administrator will record in the CAIR NOX Ozone Season sources...

40 CFR 97.512 - TR NOX Ozone Season allowance allocations to new units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false TR NOX Ozone Season allowance... TR NOX Ozone Season Trading Program § 97.512 TR NOX Ozone Season allowance allocations to new units. (a) For each control period in 2012 and thereafter and for the TR NOX Ozone Season units in each...

40 CFR 97.353 - Recordation of CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Recordation of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Tracking System § 97.353 Recordation of CAIR NOX Ozone Season allowance allocations. (a) By September 30, 2007, the Administrator will record in the CAIR NOX Ozone Season sources...

40 CFR 97.353 - Recordation of CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Recordation of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Tracking System § 97.353 Recordation of CAIR NOX Ozone Season allowance allocations. (a) By September 30, 2007, the Administrator will record in the CAIR NOX Ozone Season sources...

40 CFR 96.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Withdrawal from CAIR NOX Ozone Season... STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season...

40 CFR 97.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Withdrawal from CAIR NOX Ozone Season... CAIR NOX Ozone Season Opt-in Units § 97.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season opt-in unit may withdraw...

40 CFR 97.511 - Timing requirements for TR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false Timing requirements for TR NOX Ozone... TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.511 Timing requirements for TR NOX Ozone Season allowance allocations. (a) Existing units. (1) TR NOX Ozone Season allowances are allocated, for the control...

40 CFR 96.386 - Withdrawal from CAIR NOX Ozone Season Trading Program.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Withdrawal from CAIR NOX Ozone Season... STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.386 Withdrawal from CAIR NOX Ozone Season Trading Program. Except as provided under paragraph (g) of this section, a CAIR NOX Ozone Season...

40 CFR 97.512 - TR NOX Ozone Season allowance allocations to new units.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false TR NOX Ozone Season allowance... TR NOX Ozone Season Trading Program § 97.512 TR NOX Ozone Season allowance allocations to new units. (a) For each control period in 2012 and thereafter and for the TR NOX Ozone Season units in each...

40 CFR 97.353 - Recordation of CAIR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Recordation of CAIR NOX Ozone Season... CAIR NOX Ozone Season Allowance Tracking System § 97.353 Recordation of CAIR NOX Ozone Season allowance allocations. (a) By September 30, 2007, the Administrator will record in the CAIR NOX Ozone Season sources...

40 CFR 97.512 - TR NOX Ozone Season allowance allocations to new units.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false TR NOX Ozone Season allowance... TR NOX Ozone Season Trading Program § 97.512 TR NOX Ozone Season allowance allocations to new units. (a) For each control period in 2012 and thereafter and for the TR NOX Ozone Season units in each...

40 CFR 97.511 - Timing requirements for TR NOX Ozone Season allowance allocations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false Timing requirements for TR NOX Ozone... TRADING PROGRAMS TR NOX Ozone Season Trading Program § 97.511 Timing requirements for TR NOX Ozone Season allowance allocations. (a) Existing units. (1) TR NOX Ozone Season allowances are allocated, for the control...

40 CFR 96.23 - NOX Budget permit contents.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 21 2011-07-01 2011-07-01 false NOX Budget permit contents. 96.23 Section 96.23 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Permits § 96.23 NOX Budget permit contents. (a)...

40 CFR 97.357 - Closing of general accounts.

Code of Federal Regulations, 2011 CFR

2011-07-01

... (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS CAIR NOX Ozone Season... include a correctly submitted allowance transfer under §§ 97.360 and 97.361 for any CAIR NOX Ozone Season allowances in the account to one or more other CAIR NOX Ozone Season Allowance Tracking System accounts. (b...

40 CFR 97.83 - Applying for NOX Budget opt-in permit.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Applying for NOX Budget opt-in permit... PROGRAMS (CONTINUED) FEDERAL NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS Individual Unit Opt-ins. § 97.83 Applying for NOX Budget opt-in permit. (a) Applying for initial NO X Budget opt...

40 CFR 96.83 - Applying for NOX Budget opt-in permit.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Applying for NOX Budget opt-in permit... PROGRAMS (CONTINUED) NOX BUDGET TRADING PROGRAM AND CAIR NOX AND SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS Individual Unit Opt-ins § 96.83 Applying for NOX Budget opt-in permit. (a) Applying for...

NADPH oxidase 4 limits bone mass by promoting osteoclastogenesis

PubMed Central

Goettsch, Claudia; Babelova, Andrea; Trummer, Olivia; Erben, Reinhold G.; Rauner, Martina; Rammelt, Stefan; Weissmann, Norbert; Weinberger, Valeska; Benkhoff, Sebastian; Kampschulte, Marian; Obermayer-Pietsch, Barbara; Hofbauer, Lorenz C.; Brandes, Ralf P.; Schröder, Katrin

2013-01-01

ROS are implicated in bone diseases. NADPH oxidase 4 (NOX4), a constitutively active enzymatic source of ROS, may contribute to the development of such disorders. Therefore, we studied the role of NOX4 in bone homeostasis. Nox4–/– mice displayed higher bone density and reduced numbers and markers of osteoclasts. Ex vivo, differentiation of monocytes into osteoclasts with RANKL and M-CSF induced Nox4 expression. Loss of NOX4 activity attenuated osteoclastogenesis, which was accompanied by impaired activation of RANKL-induced NFATc1 and c-JUN. In an in vivo model of murine ovariectomy–induced osteoporosis, pharmacological inhibition or acute genetic knockdown of Nox4 mitigated loss of trabecular bone. Human bone obtained from patients with increased osteoclast activity exhibited increased NOX4 expression. Moreover, a SNP of NOX4 was associated with elevated circulating markers of bone turnover and reduced bone density in women. Thus, NOX4 is involved in bone loss and represents a potential therapeutic target for the treatment of osteoporosis. PMID:24216508

NOX4 regulates autophagy during energy deprivation.

PubMed

Sciarretta, Sebastiano; Volpe, Massimo; Sadoshima, Junichi

2014-04-01

NADPH oxidase is a cellular enzyme devoted to the production of reactive oxygen species (ROS). NOX4 and NOX2 are the main isoforms of NADPH oxidase in the cardiovascular system. In our recent study, we demonstrated that NOX4, but not NOX2, is a critical mediator of the cardiomyocyte adaptive response to energy stress. NOX4 activity and protein levels are increased in the endoplasmic reticulum (ER) but not in mitochondria of cardiomyocytes during the early phase of energy deprivation. NOX4-derived production of ROS in the ER is a critical event that activates autophagy through stimulation of the EIF2AK3/PERK-EIF2S1/eIF-2α-ATF4 pathway. NOX4-dependent autophagy is an important mechanism to preserve cellular energy and limit cell death in energy-deprived cardiomyocytes. Aside from elucidating a crucial physiological function of NOX4 during cellular energy stress, our study dissects a novel signaling mechanism that regulates autophagy under this condition.

NOX4 regulates autophagy during energy deprivation

PubMed Central

Sciarretta, Sebastiano; Volpe, Massimo; Sadoshima, Junichi

2014-01-01

NADPH oxidase is a cellular enzyme devoted to the production of reactive oxygen species (ROS). NOX4 and NOX2 are the main isoforms of NADPH oxidase in the cardiovascular system. In our recent study, we demonstrated that NOX4, but not NOX2, is a critical mediator of the cardiomyocyte adaptive response to energy stress. NOX4 activity and protein levels are increased in the endoplasmic reticulum (ER) but not in mitochondria of cardiomyocytes during the early phase of energy deprivation. NOX4-derived production of ROS in the ER is a critical event that activates autophagy through stimulation of the EIF2AK3/PERK-EIF2S1/eIF-2α-ATF4 pathway. NOX4-dependent autophagy is an important mechanism to preserve cellular energy and limit cell death in energy-deprived cardiomyocytes. Aside from elucidating a crucial physiological function of NOX4 during cellular energy stress, our study dissects a novel signaling mechanism that regulates autophagy under this condition. PMID:24492492

Unusually high soil nitrogen oxide emissions influence air quality in a high-temperature agricultural region

PubMed Central

Oikawa, P. Y.; Ge, C.; Wang, J.; Eberwein, J. R.; Liang, L. L.; Allsman, L. A.; Grantz, D. A.; Jenerette, G. D.

2015-01-01

Fertilized soils have large potential for production of soil nitrogen oxide (NOx=NO+NO2), however these emissions are difficult to predict in high-temperature environments. Understanding these emissions may improve air quality modelling as NOx contributes to formation of tropospheric ozone (O3), a powerful air pollutant. Here we identify the environmental and management factors that regulate soil NOx emissions in a high-temperature agricultural region of California. We also investigate whether soil NOx emissions are capable of influencing regional air quality. We report some of the highest soil NOx emissions ever observed. Emissions vary nonlinearly with fertilization, temperature and soil moisture. We find that a regional air chemistry model often underestimates soil NOx emissions and NOx at the surface and in the troposphere. Adjusting the model to match NOx observations leads to elevated tropospheric O3. Our results suggest management can greatly reduce soil NOx emissions, thereby improving air quality. PMID:26556236

An experimental and numerical study of nitrogen oxide formation mechanisms in ammonia-hydrogen-air flames

NASA Astrophysics Data System (ADS)

Kumar, Praveen

The demand for sustainable alternative fuels is ever-increasing in the power generation, transportation, and energy sectors due to the inherent non-sustainable characteristics and political constraints of current energy resources. A number of alternative fuels derived from cellulosic biomass, algae, or waste are being considered, along with the conversion of electricity to non-carbon fuels such as hydrogen or ammonia (NH3). The latter is receiving attention recently because it is a non-carbon fuel that is readily produced in large quantities, stored and transported with current infrastructure, and is often a byproduct of biomass or waste conversion processes. However, pure or anhydrous ammonia combustion is severely challenging due to its high auto-ignition temperature (650 °C), low reactivity, and tendency to promote NOx formation. As such, the present study focuses on two major aspects of the ammonia combustion. The first is an applied investigation of the potential to achieve pure NH3 combustion with low levels of emissions in flames of practical interest. In this study, a swirl-stabilized flame typically used in fuel-oil home-heating systems is optimized for NH3 combustion, and measurements of NO and NH3 are collected for a wide range of operating conditions. The second major focus of this work is on fundamental investigation of NO x formation mechanisms in flames with high levels of NH3 in H2. For laminar premixed and diffusion jet flames, experimental measurements of flame speeds, exhaust-gas sampling, and in-situ NO measurements (NO PLIF) are compared with numerically predicted flames using complex chemical kinetics within CHEMKIN and reacting CFD codes i.e., UNICORN. From the preliminary testing of the NOx formation mechanisms, (1) Tian (2) Konnov and (3) GRI-Mech3.0 in laminar premixed H2/NH 3 flames, the Tian and Konnov mechanisms are found to capture the reduction in measured flame speeds with increasing NH3 in the fuel mixture, both qualitatively and quantitatively. The NOx predictions by all the three chemical mechanisms are observed to be in fairly good agreement with the measured NOx, qualitatively, however predictions are found to be 3 to 4 times higher than the measurements for both lean and rich H 2/NH3 premixed flames. For laminar H2/NH3 diffusion flames, detailed 2-D comparisons of in-situ NO measurements with the 2-D simulated NO using the Tian, GRI-Mech3.0 and modified GRI-Mech chemical mechanisms are performed and found to differ from the measured NO by approximately an order of magnitude. For NH3 seeded H2/air diffusion flames, GRI-Mech3.0 seemed to overpredict NO by more than an order of magnitude and failed to capture the fundamental flame characteristics, such as the flame length variation with increasing NH3 in the fuel mixture. On the other hand, the predicted NO profiles by the Tian mechanism were not only found to be in better agreement with the measured NO, but they also captured the in-flame NO distribution as well, both qualitatively and quantitatively. Overall, the Tian mechanism is found to be the superior chemical mechanism to capture the NOx formation chemistry in NH3 seeded flames.

The NOX Family of Proteins Is Also Present in Bacteria.

PubMed

Hajjar, Christine; Cherrier, Mickaël V; Dias Mirandela, Gaëtan; Petit-Hartlein, Isabelle; Stasia, Marie José; Fontecilla-Camps, Juan C; Fieschi, Franck; Dupuy, Jérôme

2017-11-07

Transmembrane NADPH oxidase (NOX) enzymes have been so far only characterized in eukaryotes. In most of these organisms, they reduce molecular oxygen to superoxide and, depending on the presence of additional domains, are called NOX or dual oxidases (DUOX). Reactive oxygen species (ROS), including superoxide, have been traditionally considered accidental toxic by-products of aerobic metabolism. However, during the last decade it has become evident that both O 2 •- and H 2 O 2 are key players in complex signaling networks and defense. A well-studied example is the production of O 2 •- during the bactericidal respiratory burst of phagocytes; this production is catalyzed by NOX2. Here, we devised and applied a novel algorithm to search for additional NOX genes in genomic databases. This procedure allowed us to discover approximately 23% new sequences from bacteria (in relation to the number of NOX-related sequences identified by the authors) that we have added to the existing eukaryotic NOX family and have used to build an expanded phylogenetic tree. We cloned and overexpressed the identified nox gene from Streptococcus pneumoniae and confirmed that it codes for an NADPH oxidase. The membrane of the S. pneumoniae NOX protein (SpNOX) shares many properties with its eukaryotic counterparts, such as affinity for NADPH and flavin adenine dinucleotide, superoxide dismutase and diphenylene iodonium inhibition, cyanide resistance, oxygen consumption, and superoxide production. Traditionally, NOX enzymes in eukaryotes are related to functions linked to multicellularity. Thus, the discovery of a large family of NOX-related enzymes in the bacterial world brings up fascinating questions regarding their role in this new biological context. IMPORTANCE NADPH oxidase (NOX) enzymes have not yet been reported in bacteria. Here, we carried out computational and experimental studies to provide the first characterization of a prokaryotic NOX. Out of 996 prokaryotic proteins showing NOX signatures, we initially selected, cloned, and overexpressed four of them. Subsequently, and based on preliminary testing, we concentrated our efforts on Streptococcus SpNOX, which shares many biochemical characteristics with NOX2, the referent model of NOX enzymes. Our work makes possible, for the first time, the study of pure forms of this important family of enzymes, allowing for biophysical and molecular characterization in an unprecedented way. Similar advances regarding other membrane protein families have led to new structures, further mechanistic studies, and the improvement of inhibitors. In addition, biological functions of these newly described bacterial enzymes will be certainly discovered in the near future. Copyright © 2017 Hajjar et al.

40 CFR 96.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 21 2014-07-01 2014-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 96.388 Section 96.388 Protection of Environment... SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.388 CAIR...

40 CFR 96.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 22 2012-07-01 2012-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 96.388 Section 96.388 Protection of Environment... SO2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.388 CAIR...

40 CFR 96.388 - CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 22 2013-07-01 2013-07-01 false CAIR NOX Ozone Season allowance allocations to CAIR NOX Ozone Season opt-in units. 96.388 Section 96.388 Protection of Environment... SO 2 TRADING PROGRAMS FOR STATE IMPLEMENTATION PLANS CAIR NOX Ozone Season Opt-in Units § 96.388 CAIR...