Production Of Nitrogen Oxides Research Articles

Current Status of Research on Marine Nitrous Oxide Greenhouse Gases

Nitrous oxide (N2O) is a potent greenhouse gas with a global warming potential 200 times that of carbon dioxide (CO) [1]. N2O not only enhances the greenhouse effect but also breaks down in the stratosphere to produce nitrogen oxides (NO), which catalyze the destruction of the ozone layer [2]. This article reviews studies on N2O, exploring its distribution and generation mechanisms in various marine regions and discussing its environmental impact.The ocean is the largest natural source of N2O, with significant contributions from oxygen-deficient zones (ODZs) where high rates of nitrification and incomplete denitrification occur. Other high-oxygen areas, which cover 97% of the ocean, have different production mechanisms that are not well understood [4].This article aims to summarize the formation mechanisms, distribution, and effects of N2O, providing an overview of its current research status as a greenhouse gas

Analytical formulations for nitrogen oxides emissions estimation of a hydrogen fueled Synergetic Air-Breathing Rocket Engine (SABRE) in air-breathing mode

The space sector is undergoing rapid expansion due to the transformations it is experiencing, evolving from government-funded traditional space initiatives to commercially driven NewSpace activities. The surge of government and private investments in the space domain has positioned it as one of the world's fastest-growing sectors, making it crucial to assess the impact of already operational launch assets and to adopt design-to-sustainability strategies for under-development and future launchers. To actively contribute to this transition, this paper proposes a methodology for deriving novel analytical formulations to estimate nitrogen oxide (NOx) emissions of a hydrogen-fueled reusable access-to-space vehicle. Throughout the paper, the Skylon spaceplane and its Synergetic Air Breathing Rocket Engine are used as a case study. In particular, the SABRE engine presents a highly integrated dual propulsion architecture supporting both air-breathing and rocket modes. This study specifically focuses on the former, enabling the Single Stage To Orbit (SSTO) Skylon reaching the hypersonic speed regime before transitioning to rocket mode. This paper proposes novel analytical formulations to be integrated into the Fuel Flow (FF) and P3-T3 methods for estimating NOx Emission Index (EINOx), since the early design phase. These estimation techniques currently enable the calculation of the emission index of pollutants and GreenHouse Gases (GHGs) produced by any subsonic aero-engines powered by traditional fuels (i.e. kerosene) only. The methodology presented in this paper allows for upgrading the original mathematical formulations of the methods to ensure the applicability to high-speed flight and hydrogen fuel conditions. This involves the propulsive modelling of the engine and the chemical-kinetic modelling of the combustion process, representative of various on-ground and in-flight operating conditions, to generate updated and reliable propulsive and emissive databases for the engine. To this end, 0D chemical-kinetic air/hydrogen combustion numerical simulations are employed. The results of the performance analysis and emission modeling of the SABRE engine are reported and discussed. Regarding the calculated EINOx trend for the air-breathing phase of the engine operation, it reaches a peak of 45 gNOx/kgH2burnt under hypersonic conditions. Through the analysis of correlations between the propulsive characteristics of the SABRE and its NOx production, a series of parameters (such as Mach Number, Fuel to Air Ratio, Water to Fuel Ratio, and others) are selected to be integrated into the original formulations of the P3-T3 and FF methods via mathematical interpolation to adapt them to the case study. Finally, the EINOx trends resulting from the application of the new H2-P3T3 and H2-FF methods to the SABRE are graphically reported, along with the corresponding estimation errors relative to the reference trend from the engine emission database. Additionally, a discussion regarding the chemical-physical justifications for the mathematical contributions to the formulations for EINOx of the newly introduced parameters is provided.

Lightning-Driven Pyrite Oxidation Under Archean Atmosphere Conditions.

Oxidative weathering is a major source of bio-essential micronutrients on Earth today; however, this flux would have been muted on the early Earth or on Mars, where atmospheric O2(g) levels were very low. Here, we explore the hypothesis that nitrogen oxides generated by lightning in an anoxic atmosphere could have elevated pyrite oxidation levels under otherwise anoxic conditions. We performed spark discharge experiments in the presence of pyrite powder and three different gas mixtures, including 80% N2(g) with 20% CO2(g), 95% N2(g) with 5% CO2(g), and modern air. Experiments were run for 30 min, and we tracked the production of NO(g), dissolved nitrate and nitrite, pH, dissolved sulfate, and total dissolved iron. Our results reveal increasing production of nitrogen oxides with increasing CO2(g) and O2(g) levels, which is consistent with previous studies. Dissolved iron and sulfate also increase, indicating that the nitrogen oxides are able to oxidize pyrite abiotically. Extrapolating these data to global conditions suggests that this mechanism was probably insignificant on a global scale on the early Earth; however, in thunderstorm-prone areas, such as in the modern tropics where lightning rates may locally be over 10 times above the global average, lightning could have rivalled abiotic pyrite oxidation by Archean O2 levels. The lightning contribution would have been highest during time periods with elevated CO2(g), which makes it a potentially important contributor to local release of sulphur, iron, and bio-essential micronutrients on prebiotic land surfaces or on other planets with anoxic CO2-rich atmospheres.

Nitrogen isotopes reveal high NOx emissions from arid agricultural soils in the Salton Sea Air Basin

Air quality management commonly aims to mitigate nitrogen oxide (NOx) emissions from combustion, reducing ozone (O3) and particulate matter (PM) pollution. Despite such ongoing efforts, regulations have recently proven ineffective in rural areas like the Salton Sea Air Basin of Southern California, which routinely violates O3 and PM air quality standards. With over $2 billion in annual agricultural sales and low population density, air quality in the region is likely influenced by the year-round farming activity. We conducted a source apportionment of NOx (an important precursor to both O3 and PM) using nitrogen stable isotopes of ambient NO2, which revealed a significant contribution from soil-emitted NOx to the regional budget. The soil source strength was estimated based on the mean δ15N-NOx from each emission category in the California Air Resources Board’s NOx inventory. Our annual average soil emission estimate for the air basin was 11.4 ± 4 tons/d, representing ~ 30% of the extant NOx inventory, 10× larger than the state’s inventory for soil emissions. Unconstrained environmental factors such as nutrient availability, soil moisture, and temperature have a first-order impact on soil NOx production in this agriculturally intensive region, with fertilization and irrigation practices likely driving most of the emissions variability. Without spatially and temporally accurate data on fertilizer application rates and irrigation schedules, it is difficult to determine the direct impacts that these variations have on our observations. Nevertheless, comparative analysis with previous studies indicates that soil NOx emissions in the Imperial Valley are likely underrepresented in current inventories, highlighting the need for more detailed and localized observational data to constrain the sizeable and variable emissions from these arid, agricultural soils.

Seasonal persistence of the nitrogen oxides production in Mexico City

AbstractThis study investigates the seasonal influence on the nitrogen oxide NOx pollution records at four monitoring sites in Mexico City from 2010 to 2018. The analysis employs the second-order structure function to examine the trends in NOx concentration fluctuations. The findings reveal that the fluctuations follow a power law pattern characterized by Hurst exponents, predominantly in the statistical persistence regime, with a scaling range spanning three orders of magnitude. Specifically, the autumn period exhibits fluctuations with an exponent of $$\overline{H}=0.72$$ H ¯ = 0.72 , indicating relatively smaller fluctuations compared to other seasons, but with the potential for NOx concentrations to surpass those in other periods. In contrast, for spring, summer, and winter, the fluctuations are characterized by exponents of$$\overline{H}=0.59$$ H ¯ = 0.59 ,$$\overline{H}=0.61$$ H ¯ = 0.61 , and$$\overline{H}=0.62$$ H ¯ = 0.62 , respectively, demonstrating greater fluctuations with lower NOx concentrations compared to autumn. These results are consistent with various studies conducted worldwide. Additionally, a negative correlation between NOx and ozone (O3) has been established during the winter season, as NOx and O3 fluctuations display persistent and anti-persistent behavior, respectively.

Ammonia Sprays for Combustion: A Review

Ammonia is a globally transported chemical used for a variety of applications, most notably, the production of fertiliser. Over the past decade, attention has been afforded to the use of ammonia as an energy carrier, coupling global supply of renewable energy to demand regions. Ammonia’s advantages as an energy carrier include its ease of liquefaction and established international transportation routes; overcoming its low reactivity, excessive production of nitrogen oxides and its toxicity remain as challenges. For energy applications, fuel delivery is a critical aspect of effective combustion in boilers, burners and engines. Due to its adaptable phase change characteristics, ammonia fuel may be injected as a liquid or vapour, each with respective advantages or disadvantages. The focus of this review concerns the characterisation of liquid ammonia fuel injection for combustion, including recent research findings from experimental and simulation studies. Liquid ammonia injection can result in the highly dynamic so-called ‘flashing’ or ‘flash boiling’ phenomena. Research findings have been drawn from other related applications such as accidental hazardous releases. Bespoke optical experimental rigs together with diagnostic techniques and two-phase computational fluid dynamics (CFD) simulations have enabled studies of the flashing jets under various initial or final conditions, with recent work also examining ammonia spray combustion. The review concludes with an insight into future trends and requirements for liquid ammonia combustion. Reciprocating engines for marine propulsion are cited as potential early adopters of ammonia energy.

Combination of G-Equation and Detailed Chemistry: An application to 3D-CFD hydrogen combustion simulations to predict NOx emissions in reciprocating internal combustion engines

In the recent years, the growing pressure by the European Union to phase out the internal combustion engines has raised the quest for alternative solutions for low-environmental-impact mobility. Nevertheless, concerns on the life-cycle emissions of battery electric vehicles and perplexities on the socio-economic sustainability of the ecological transition suggest that maintaining the interest in internal combustion engines can be strategic, provided that carbon-neutral fuels are adopted. On the basis of the technological neutrality principle, relying on already existing and well-established technologies requires less effort and cost to convert the whole road transport. Moreover, the adoption of bio- or e-fuels obtained from renewable sources widely spread across the globe is not of secondary importance. In fact, cost reduction and worldwide diffusion of the resources are both main promoters of socio-economic sustainability.In this scenario, green hydrogen represents one of the main solutions for the survival of reciprocating engines. Since the production is solely based on renewable energy sources, it is not simply characterized by zero CO2 emissions at the tailpipe, but it can be considered overall carbon neutral. A technical drawback in the use of hydrogen is represented by emissions of nitrogen oxides (NOx), due to the ever-present high temperature combustion process. For this reason, an ad-hoc design is mandatory to minimize NOx production, and CFD can be a valid tool to reduce cost and time to market for the development of hydrogen engines.In this regard, the current work proposes a 3D-CFD numerical methodology, based on the combination of G-Equation and Detailed Chemistry models, for NOx prediction in in-cylinder simulations of reciprocating internal combustion engines fueled with hydrogen. Although the combination of level-set method and chemical kinetics is not a novelty in literature, it is the first time that it is applied to evaluate NOx emissions in H2 engines. The proposed approach is validated against experimental data on a direct injection, spark ignition, hydrogen engine. The methodology is able to properly predict NOx emissions at different mixture qualities, revving speeds and spark times. The total number of investigated cases is 17, which is a large set of simulations compared to the existing literature. Considering the best chemical mechanism (i.e. the one providing the best results among the tested ones), the error in the NOx prediction is always lower than 25% for all the simulations.Once the methodology is validated, the effect of spark and injection timings on NOx is discussed. Such a deepening is useful to emphasize the potential of the CFD to investigate phenomena leading to emission formation and, thus, to optimize engine parameters for NOx reduction.

On the Energy Cost for Nitrogen Fixation in DC Glow Discharges in Atmospheric‐Pressure Air

ABSTRACTModeling of the production of nitrogen oxide molecules in DC discharges in laminar longitudinal flows of atmospheric‐pressure air is performed. Two‐dimensional nonequilibrium discharge model includes the system of gas dynamic equations and balance equations for various plasma components. Simulations are performed for the discharge currents 50–600 mA and gas flow velocities 1–10 m/s. In considered conditions, the gas temperature in the discharge core varies in the range of 3000–6000 K. Spatial profiles of the densities and fluxes of produced species are obtained, both inside the discharge and in the afterglow region. The energy cost for the production of nitrogen oxides is calculated, depending on the discharge current, gap length, and gas flow velocity. The results of the simulation are compared with available experimental data.

Nitrogen Fixation by Atmospheric Microwave Plasma with Local Electric Field Enhancement

Abstract Nitrogen fixation by atmospheric microwave plasma is a promising green technology. However, the energy consumption of nitrogen fixation driven by microwave plasma is still too high in existing reports, and there is a lack of effective methods to reduce it. In this paper, a method of local electric field enhancement in atmospheric microwave plasma is reported, which is achieved in an optimized metal array structure that can increase the electric field intensity by 385 times. The experimental results show that the reduction of energy consumption reaches up to 20% and the nitrogen oxide production increases by up to 26% with the local electric field enhancement. The achieved energy consumption is as low as 1.78 MJ/mol with a corresponding nitrogen oxide production of 3.53%. To the best of our knowledge, this is the first study to explore the role of local electric field enhancement on nitrogen fixation, and the energy consumption in this study is the lowest among the existing studies of nitrogen fixation by atmospheric pressure microwave air plasma.

Hydrogen-natural gas fuel blending in a “rich burn” engine with 3-way catalyst

Interest in hydrogen (H2) fuels is growing, with industry planning to produce it with stranded or excess energy from renewable sources in the future. Natural gas (NG) utility companies are now taking action to blend H2 into their preexisting pipelines to reduce greenhouse gas (GHG) emissions from burning NG. Stoichiometric (“rich burn”) NG engines that operate on pipeline NG and will receive blended fuel as more gas utilities expand H2 production. These engines are typically chosen for their low emissions owing to the 3-way catalyst control, so the focus of this paper is on the change in emissions like carbon monoxide (CO) and nitrogen oxides (NOx) as the fuel is blended with up to 30% H2 by volume. The Caterpillar CG137-8 natural gas engine used for testing was originally designed for industrial gas compression applications and is a good representative for most “rich burn” engines used across industry for applications such as power generation, gas compression, and water pumping. A significant greenhouse gas (GHG) emissions reduction is observed as more H2 is added to the fuel. Increasing H2 in the fuel changes combustion behavior in the cylinder, resulting in faster ignition and higher cylinder pressures, which increase engine-out NOx emissions. Post-catalyst CO and NOx both decrease slightly with increasing H2 while operating at the optimal “air-fuel” equivalence ratio (λ). A “rich burn” engine with 3-way catalyst can tolerate up to 30% H2 (by vol.) while still meeting NOx and CO emissions limits. However, at elevated levels of H2, increased engine-out NOx emissions narrow the λ range of operation. As H2 is added to NG pipelines, some “rich burn” engine systems may require larger catalysts or more precise λ control to accommodate the increased NOx production associated with a H2-NG blend. Sudden step-increases in H2 cause dramatic changes in λ, resulting in large emissions of post-catalyst NOx during the transition. Comparable changes in H2 at elevated concentrations cause larger spikes in NOx than at lower concentrations. Better tuned engine controllers respond more quickly and produce less NOx during H2 step-transitions.

Anti-Inflammatory Effects of Quercetin, Rutin, and Troxerutin Result From the Inhibition of NO Production and the Reduction of COX-2 Levels in RAW 264.7 Cells Treated with LPS.

Flavonols effectively scavenge the reactive nitrogen species (RNS) and reactive oxygen species (ROS) and act as immune-enhancing, anti-inflammatory, anti-diabetic, and anti-carcinogenic agents. Here, we explored the comparative antioxidant and anti-inflammatory properties of plant-originating flavonols, like quercetin, rutin, and troxerutin against acetylsalicylic acid. Quercetin and rutin showed a high ability to remove active ROS, but troxerutin and acetylsalicylic acid exhibited little such function. In RAW 264.7 cells, quercetin, rutin, and troxerutin did not exhibit cellular toxicity at low concentrations. In addition, quercetin, rutin, and troxerutin considerably (p < 0.05) lowered the protein expression of cyclooxygenase 2 (COX-2) as compared to acetylsalicylic acid in cells inflamed with lipopolysaccharides (LPS). Additionally, in inflamed cells, quercetin and rutin significantly down-regulated the nitrogen oxide (NO) level (p < 0.05) at higher concentrations, whereas Troxerutin did not reduce the NO level. In addition, Troxerutin down-regulated the pro-inflammatory protein markers, such as TNF-α, COX-2, NF-κB, and IL-1β better than quercetin, rutin, and acetylsalicylic acid. We observed that troxerutin exhibited a significantly greater anti-inflammatory effect than acetylsalicylic acid did. Acetylsalicylic acid did not significantly down-regulated the expression of COX-2 and TNF-α (p < 0.05) compared to troxerutin. Hence, it can be concluded that the down-regulation of NO levels and the expression of COX-2 and TNF-α proteins could be mechanisms of action for the natural compounds quercetin, rutin, and troxerutin in preventing inflammation.

STUDYING HOW DIESEL ENGINE ADDITIVES USING SILVER OXIDE (Ag2O) NANOPARTICLES AFFECT THE ENVIRONMENT

Abstract: Biodiesel has been defined as an alternative fuel that has the potential to be used instead of diesel fuel for years. In case of complete combustion reaction in engines, the products released do not directly threaten human health. Compared to diesel fuel, biodiesel has worse combustion performance due to some fuel properties. Therefore, incomplete combustion products such as hydrocarbon (HC), carbon monoxide (CO), nitrogen oxide (NOx), smoke emission and complete combustion products such as CO2 are thrown into the atmosphere. In this study, the changes in exhaust emissions of 50 ppm and 75 ppm Ag2O NPs were experimentally examined to improve the adverse combustion performance and emission characteristics of cottonseed oil methyl ester. In experiments, nano additive improved the thermal conductivity, mass dissipation and heat transfer of the test fuels, and resulted in reducing of CO emissions as it provided a higher oxidation rate of hydrocarbon molecules. Due to the improvement in the combustion reaction, CO2 emission increased with product of complete combustion. The increase in CO2 emissions was 3.17% and 3.97% for CAg-50 and CAg-75 fuels, respectively, when compared to C0 fuel at 40 Nm load. The NPs additive increased the lower calorific value of the fuel and cylinder temperature. This situation caused increase of NOx emissions by 3.69% and 7.47% CAg-50 and CAg-75 fuels 40 Nm load. Adding of NPs in base fuel reduced to viscosity and density provided better atomization. So a reduction in smoke emission was obtained with NPs addition by 35.09% and 47.32% in CAg-50 and CAg-75 fuels, respectively, compared to C0 fuel at 10 Nm load, while 7.45% and 19.43% at 40 Nm load.

NO Formation in Combustion Engines Fuelled by Mixtures of Hydrogen and Methane

The present work addresses the production of nitrogen oxides in ICEs burning hydrogen mixed with methane. A mathematical model that allows the calculation of nitrogen oxide emissions from such combustion was built; this model uses the extended chemical kinetic mechanism of Zeldovich. Numerical simulations were carried out on the production of NO, varying the following variables: proportion of H2 to CH4, the equivalence ratio of the reactant mixture, the compression ratio, and the engine speed. The essential purpose was to assess how NO production is affected by the mentioned variables. The main assumptions were (i) Otto cycle; (ii) instantaneous combustion; (iii) chemical equilibrium reached just at the end of combustion; (iv) the formation of NO only during the expansion stroke of pistons. Results were obtained for various proportions of hydrogen and methane, various equivalence ratios, speeds of rotation, and compression ratios of an engine. In short, the results obtained in the current work show that the lowering of the equivalence ratio leads to a lower concentration of NO; that increasing the compression ratio also lowers the concentration of NO; that NO production occurs until shortly after the beginning of the expansion stroke; and finally, that the NO concentration in the engine exhaust is not very sensitive to the H2/CH4 ratio in the fuel mixture.

Lipid metabolites and nitric oxide production in the cerebrospinal fluid and plasma of dogs with meningoencephalitis of unknown origin and idiopathic epilepsy: a pilot study.

Idiopathic epilepsy (IE) and meningoencephalomyelitis of unknown origin (MUO) are common causes of brain diseases leading to seizures in dogs. In this study, the concentrations of 196 lipid metabolites and nitrogen oxide (NO) production in the cerebrospinal fluid (CSF) and plasma of dogs with MUO or IE were measured using a LC-MS/MS and a NOx analyzer, respectively. Nine clinically healthy dogs and 11 and 12 dogs with IE and MUO, respectively, were included in the study. Lipid analysis revealed variations in the levels of four and six lipid metabolites in CSF and plasma, respectively, between the groups. The levels of 6-keto-prostaglandin (PG) F1α (PGF1α), 20-carboxy arachidonic acid (20-carboxy-AA), 9-hydroxyoctadecadienoic acid, and lyso-platelet-activating factor were high in the CSF of dogs with MUO. In addition, the plasma levels of 11,12-dihydroxyeicosatrienoic acid, 20-carboxy-AA, and oleoylethanolamide were high in dogs with IE, and those of PGF1α were high in dogs with MUO. NO production levels were high in CSF but not in plasma in dogs with MUO or IE. It remains unknown whether these changes represent the cause or effect of diseases of the central nervous system; however, lipid metabolites and NO production in CSF and plasma may be used as diagnostic biomarkers and could be exploited for treating idiopathic or inflammatory epilepsy in dogs.

Innovative torque-based control strategy for hydrogen internal combustion engine

Over the past years, several efforts have been made to reduce greenhouse gas emissions coming from the transport sector. Due to the highly efficient CO2-free combustion and low manufacturing costs, Hydrogen Internal Combustion engines (H2ICEs) are considered one of the most promising solutions for the future of medium and heavy duty vehicles. However, the combustion of an air-hydrogen mixture presents challenges related to the production of nitrogen oxides (NOx) and high knock tendency, mainly due to the chemical characteristics of the fuel. Although these problems can be mitigated by the use of a lean mixture, which is also useful to increase the combustion efficiency, the presence of excess air reduces exhaust temperatures and, consequently, the enthalpy content in the exhaust would be limited, leading to a reduced boosting capability. Therefore, a proper control of mixture preparation and combustion phasing is mandatory to limit NOx emissions, avoid abnormal combustions, and maximize efficiency without performance limitations.This paper focuses on the design of a dedicated control strategy for H2ICEs. Starting from a previously validated 1-D engine model operated with hydrogen, a 0-D Artificial Neural Network (ANN) - based engine model has been designed and calibrated. By using the obtained fast running ANN-based model, an innovative torque-based engine controller has been developed and both engine and controller models have been tested covering different torque profiles. The results show good accuracy within a range of ±5% on producing the requested torque by controlling the centre of combustion.

Water Microdroplets in Air: A Hitherto Unnoticed Natural Source of Nitrogen Oxides.

Water microdroplets are widespread in the atmosphere. We report a striking observation that micron-sized water droplets obtained from zero-volt spray sources (sonic spray, humidifier, spray bottle, steamer, etc.) spontaneously generate nitrogen oxides. The mechanistic investigation through the development of custom-designed sampling sources combined with mass spectrometry and isotope labeling experiments confirmed that air nitrogen reacts with the water at the air-water interface, fixing molecular nitrogen to its oxides (NO, NO2, and N2O) and acids (HNO2 and HNO3) at trace levels without any catalyst. These reactions are attributed to the consequence of an experimentally detected feeble corona discharge (breakdown of air) at the air-water interface, likely driven by the high intrinsic electric field at the surface of water microdroplets. The extent of this corona discharge effect varies depending on the pH, salinity/impurity, size, speed, and lifetime of microdroplets in the air. Thus, this study discloses that the air-water interface of microdroplets breaks the strong chemical bond of nitrogen (N2), producing nitrogen oxides in the environment, while lightning strikes and microbial processes in soil are considered their dominant natural sources. As nitrogen oxides are toxic air pollutants, their spontaneous formation at the air-water interface should have important implications in atmospheric reactions, requiring further investigations.

Detonation properties and nitrogen oxide production in ammonia–hydrogen–air mixtures

Ammonia is a promising compound for chemical storage of renewable energy produced from non-continuous sources. However, the low reactivity of ammonia requires to use ammonia–hydrogen blends as a fuel for combustion applications. The present study corresponds to a first numerical assessment of the potential of ammonia–hydrogen–air mixtures as reactive mixtures for detonation engine applications. Both ideal and curved detonation models were employed to calculate the detonation properties, entropy production, and NOx production for mixtures with varying amounts of ammonia and hydrogen under a wide range of initial thermodynamics conditions. Interestingly, our calculations show that the entropy production and the amount of nitrogen oxides produced at the Chapman–Jouguet state respectively decreases and increases with the proportion of hydrogen in the ammonia–hydrogen blend. These aspects could have a great impact on engine efficiency and air pollution and should be considered with care. Our results also demonstrate that only mixtures with relatively low amounts of ammonia, i.e., XNH3 lower than 0.25 of the fuel blend, can be employed for detonation engine applications.

Numerical Investigation of a Hydrogen–Air Flame for NOx Prediction

Abstract Sustainable aviation fuels are a major candidate to reduce pollutant emissions in future aeronautical engines. Recently, the use of hydrogen as a fuel has gained a high interest partly because its combustion is free from carbon dioxide, a greenhouse gas, and produces few pollutants, mainly nitrogen oxides (NOx). Over the last decades, efforts on numerical methods for combustion simulation in aero-engines have largely been focused on kerosene-air combustion. However, the current transition may have a significant impact on the computational methodologies for combustor design. Hydrogen defines novel modeling issues and challenges the current state of art on numerical methodologies. The current study presents a numerical investigation of a hydrogen–air burner using large-eddy simulations (LES) with a focus on NOx prediction. The considered configuration is a two-staged combustor, similar to the well-known RQL (Rich-Quench-Lean) technology, supplied by a single coaxial injector characterized experimentally. Two combustion models are investigated: (i) tabulated chemistry based on premixed flamelets (ii) transported chemistry description by using a 21-species chemical scheme. Numerical results are compared with experimental data (NOx concentrations, temperature distributions, pressure losses). A focus on model predictions is carried out. Results show a good agreement to predict the main flow characteristics and the premixed flame position over different operating points and geometries for both frameworks. In contrast, NOx emissions are more sensitive: while the overall trend is well captured, the quantification is more scattered. Finally, an in-depth analysis is proposed to link NOx production with the nonpremixed flame size.

Co-cultures from Plants and Cyanobacteria: A New Way for Production Systems in Agriculture and Bioprocess Engineering.

Due to the global increase in the world population, it is not possible to ensure a sufficient food supply without additional nitrogen input into the soil. About 30-50% of agricultural yields are due to the use of chemical fertilizers in modern times. However, overfertilization threatens biodiversity, such as nitrogen-loving, fast-growing species overgrow others. The production of artificial fertilizers produces nitrogen oxides, which act as greenhouse gases. In addition, overfertilization of fields also releases ammonia, which damages surface waters through acidification and eutrophication. Diazotrophic cyanobacteria, which usually form a natural, stable biofilm, can fix nitrogen from the atmosphere and release it into the environment. Thus, they could provide an alternative to artificial fertilizers. In addition to this, biofilms stabilize soils and thus protect against soil erosion and desiccation. This chapter deals with the potential of cyanobacteria as the use of natural fertilizer is described. Possible partners such as plants and callus cells and the advantages of artificial co-cultivation will be discussed later. In addition, different cultivation systems for studying artificial co-cultures will be presented. Finally, the potential of artificial co-cultures in the agar industry will be discussed.

An Injectable Puerarin Depot Can Potentiate Chimeric Antigen Receptor Natural Killer Cell Immunotherapy Against Targeted Solid Tumors by Reversing Tumor Immunosuppression.

Chimeric antigen receptor natural killer (CAR-NK) cell therapy represents a potent approach to suppressing tumor growth because it has simultaneously inherited the specificity of CAR and the intrinsic generality of NK cells in recognizing cancer cells. However, its therapeutic potency against solid tumors is still restricted by insufficient tumor infiltration, immunosuppressive tumor microenvironments, and many other biological barriers. Motivated by the high potency of puerarin, a traditional Chinese medicine extract, in dilating tumor blood vessels, an injectable puerarin depot based on a hydrogen peroxide-responsive hydrogel comprising poly(ethylene glycol) dimethacrylate and ferrous chloride is concisely developed. Upon intratumoral fixation, the as-prepared puerarin depot (abbreviated as puerarin@PEGel) can activate nitrogen oxide production inside endothelial cells and thus dilate tumor blood vessels to relieve tumor hypoxia and reverse tumor immunosuppression. Such treatment can thus promote tumor infiltration, survival, and effector functions of customized epidermal growth factor receptor (HER1)-targeted HER1-CAR-NK cells after intravenous administration. Consequently, such puerarin@PEGel-assisted HER1-CAR-NK cell treatment exhibits superior tumor suppression efficacy toward both HER1-overexpressing MDA-MB-468 and NCI-H23 human tumor xenografts in mice without inducing obvious side effects. This study highlights a potent strategy to activate CAR-NK cells for augmented treatment of targeted solid tumors through reprogramming tumor immunosuppression.