Concentrations Of Nitrogen Oxides Research Articles

The Research on Influencing Factors of Housing Price

This paper analyzed the various factors affecting housing prices in the Boston area. Given that housing prices are one of the most highly influential elements in the social economy and individual decisions, this study aimed to trace the main key determinants driving fluctuations in this market. The results from an MLR model applied on 509 observations of characteristics describing housing in the Boston area, using a dataset from Kaggle against housing prices, have been reported. The empirical results of the study reveal that crime rate, number of rooms, air quality (nitrogen oxide concentration), pupil-teacher ratio, property tax rate, distance to employment centers, and highway accessibility affect housing prices. A higher crime rate and nitrogen oxide concentration lead to a decrease in housing prices, whereas an increase in the number of rooms and better highway accessibility leads to an increase in housing prices. Other variables that the study identified as likely to have multicollinearity problems are property tax and highway accessibility. Such conclusions assist in gaining a better understanding of the dynamics associated with determinants in housing price and offer invaluable advice to policymakers, investors, and potential homebuyers in making decisions regarding real estate policy and investments within Boston's real estate market.

Analysis of the influence of combustion air humidification technology on low nitrogen combustion law of the gas boiler

ABSTRACT A significant amount of nitrogen oxides (NOx) produced by gas boilers is directly released into the atmosphere, posing serious risks to both the environment and human health. To mitigate NOx emissions from gas boilers, this study investigated the effects of varying humidity levels on flue gas temperature, NOx concentration, and boiler operational stability using both experimental and simulation methods. Results show that humidifying combustion air to 79.0 g/kg reduces NOx concentration in the flue gas to 38.1 mg/m3, achieving a maximum NOx reduction rate of 72.0%. However, at this level, the boiler’s operational stability is severely compromised. When the air is humidified to 57.3 g/kg, the CO concentration at the furnace outlet increases significantly, further degrading operational stability. Overall, increasing the water vapor content in combustion air negatively impacts the inherent stability of gas boiler operation. The air humidification method proposed in this study offers a promising technical framework for low-NOx retrofitting of existing gas boiler systems.

Using Air Plasma‐generated High‐Valence NOx for Olive Oil Activation to Produce High‐Performance Antimicrobial Agents

ABSTRACTThis study develops a time‐ and performance‐efficient process for oil activation with enhanced bioreactivity. Instead of ozone foaming, plasma‐activated gas (PAG) bubbling has been, for the first time, employed for potent olive oil activation. A parallel system integrating dielectric barrier discharge (DBD) and gliding arc discharge (GAD) devices generates air‐PAG rich in high‐valence nitrogen oxides (NOx) and O3. By adjusting DBD and GAD power ratios, PAG composition is controlled. At a power ratio of 1:1, NOx content and the sterilization performance of thus‐obtained plasma‐activated oil (PAO) reach their peaks. Compared to traditional ozonated oil and plasma‐activated water (PAW), PAO demonstrates superior bacterial‐killing ability and extended storage stability, showing outstanding capacity in medical and food applications as a green agent.

Air distribution to reduce nitrogen oxide emissions in the furnace of a boiler with tangential combustion scheme

Relevance. Determined by the importance of analyzing the combustion characteristics and factors affecting the emission of nitrogen oxides (NOx) in the furnace chamber of pulverized coal-fired power boiler unit when installing tertiary air nozzles and changing the air flow rate through them, to ensure the reduction of negative anthropogenic impact on the environment. It should be noted that the use of tertiary nozzles is the most cost-effective technology of the internal furnace measures of NOx emission reduction. Aim. To analyze the effect of oxidant redistribution between secondary air and tertiary blast in the range of 40% on the burnout and NOx emission in the furnace chamber of a boiler unit with tangential burner arrangement. Objects. Power pulverized coal-fired boiler unit with natural circulation. Straight-flow burner devices are arranged according to the tangential scheme, tertiary blast nozzles are installed above the burners. Methods. Computational fluid dynamics modeling methods. For the simulation study of furnace processes the tested software FIRE-3D was used. The averaged equations of conservation of mass, momentum and enthalpy were solved to predict the velocity, temperature and concentration of components of the furnace medium in the furnace volume. The turbulent flow was modeled by the standard k-ε model. Coal particle transport was modeled using a discrete-phase model. The P-1 model was used for radiant heat transfer. Results. The authors have carried out the analysis of O₂, CO, and NOₓ concentrations, as well as velocity fields and temperature to examine the effects of varying the ratio of secondary and tertiary air in the furnace volume of a boiler unit with tangentially arranged burners and tertiary blast nozzles. Numerical modeling results revealed that with tertiary blast nozzles, the active combustion zone shifts upward. However, at higher proportions of tertiary blast, NOₓ reduction is not achieved due to increased temperatures at the furnace outlet. Taking into account NOx emissions and completeness of fuel burnout, the most optimal for modernization of the investigated boiler is the value of tertiary blast fraction equal to 0.2.

Assessment of the influence of thermal characteristics of non-design lignite on their suitability for combustion in the furnace of an energy boiler

The possibility of burning various brown coals (LC) in the furnace of the BKZ-420-140-6 boiler was studied using numerical simulation. To check the compiled numerical model of solid fuel combustion, it was previously validated in relation to the combustion of BU of a certain composition by comparing the calculation results with data obtained during the operation of a real boiler. A method was developed for averaging the characteristics of coal and dependencies were obtained that determine the composition of coal based on an analysis of the composition of 14 types of coal in the range of values of the lower calorific valueQnr from 7.5 to 16 MJ/kg. Based on the obtained dependencies for 4 values of Qnr, the theoretical average composition (ATC) of coals was determined. For one of the TUSs, the humidity varied by 10% up and down. As indicators of the efficiency of the combustion chamber of the boiler, the temperature of the gases at the exit from the combustion chamber, mechanical underburning and the concentration of nitrogen oxides in the flue gases are taken. The results of numerical modeling show that with the calorific value of the fuelQnr ≤10 MJ/kg, the mechanical underburning q4 exceeds the permissible standards. The highest concentration of nitrogen oxides at the level of 800–900 mg/nm3 is observed for brown coals with highQnr and the highest carbon content. It is also shown that the use of direct-flow burners with the organization of staged fuel combustion makes it possible to reduce the formation of nitrogen oxides in the furnace by 3.25 times compared to the original combustion scheme using existing vortex burner devices. The influence of the lower calorific value of fuel on the gas temperature at the exit from the combustion chamber in the rangeQnr from 11.75 to 16.45 MJ/kg is insignificant. The effect of increasing fuel humidity on the gas temperature at the outlet of the combustion chamber and on mechanical underburning is insignificant up to a working fuel humidity of approximately 45%. In general, studies have shown that the firebox under consideration allows the combustion of various brown coals with changes in the physico-chemical composition and thermal characteristics within a wide range.

CALCULATION PROGRAM OF THE ABSORPTION PROCESS IN NITRIC ACID PRODUCTION

The modern technological process is a product of design and modeling. Verification of theories and technical solutions can be carried out not on existing equipment but on mathematical models, by means of calculations. This increases the safety of research activities and speeds up the design process. For large research institutions and manufacturers, it is advisable to use specialized software such as MatLab, ASPEN or SimSci. Such environments have a large number of libraries and applications, which make them multifunctional. At the same time, the vast majority of users use only a small number of narrowly specialized functions that correspond to the direction of their activity. Mastering programming skills has become an integral part of modern education. Creating calculation programs based on mathematical models is not a difficult task for scientists. The rapid development of programming languages and technologies allows choosing the most appropriate ways of creating programs. According to experts, C# has been in the top 5 popular programming languages for many years. The use of this language is closely related to the .NET technology, which is intended for creating cross-platform applications. Microsoft Corporation provides the possibility of free use of its product MS Visual Studio, which also includes C#. The article describes a program created for use in researching the operation of an absorption column for the absorption of nitrogen oxides in the production of nitric acid. When developing the program, a standard calculation algorithm was used, according to which industrial devices operating in Ukraine were calculated. The algorithm also takes into account the latest information on the influence of technological parameters and physico-chemical processes. The program is created with a minimalistic interface and data entry options both from the program window and from a text file. The results of calculating the influence of oxygen addition on the concentration of nitrogen oxides in the discharge gas are given. The main purpose of the program is to study the operation of the column as an object of automation. The proposed program can be supplemented with new options, such as automatic calculation of gain coefficients for specified channels, batch processing based on data from a file, and others. Also, the program can be used for teaching students and performing research.

The potential of drone observations to improve air quality predictions by 4D-Var

Abstract. Vertical profiles of atmospheric pollutants, acquired by uncrewed aerial vehicles (UAVs, known as drones), represent a new type of observation that can help to fill the existing observation gap in the planetary boundary layer (PBL). This article presents the first study of assimilating air pollutant observations from drones to evaluate the impact on local air quality analysis. The study uses the high-resolution air quality model EURAD-IM (EURopean Air pollution Dispersion – Inverse Model), including the four-dimensional variational data assimilation system (4D-Var), to perform the assimilation of ozone (O3) and nitrogen oxide (NO) vertical profiles. 4D-Var is an inverse modelling technique that allows for simultaneous adjustments of initial values and emissions rates. The drone data were collected during the MesSBAR (automated airborne measurement of air pollution levels in the near-earth atmosphere in urban areas) field campaign, which was conducted in Wesseling, Germany, on 22–23 September 2021. The results show that the 4D-Var assimilation of high-resolution drone measurements has a beneficial impact on the representation of regional air pollutants within the model. On both days, a significant improvement in the vertical distribution of O3 and NO is noticed in the analysis compared to the reference simulation without data assimilation. Moreover, the validation of the analysis against independent observations shows an overall improvement in the bias, root mean square error, and correlation for O3, NO, and NO2 (nitrogen dioxide) ground concentrations at the measurement site as well as in the surrounding region. Furthermore, the assimilation allows for the deduction of emission correction factors in the area near the measurement site, which significantly contributes to the improvement in the analysis.

Effect of Acids on Biomass Growth and Development of Chlorella vulgaris Culture

Background. Influence of dissolved nitrogen and sulfur oxides, as components of flue gases, on the cultivation of microalgae Chlorella vulgaris. Objective. To study biomass production and changes in cells of the microalgae Chlorella vulgaris with the introduction of nitrogen and sulfate acids tor simulate the effects of dissolved nitrogen and sulfur oxides, aiming to develop biotechnology for the utilization of gas emissions by microalgae. Methods. The effect of the constant introduction of small concentrations of nitrogen (up to 0.47%) and sulfate (up to 1.5%) acids on the development of Chlorella vulgaris cultures, pH changes in the cultural envi­ronment, and biomass growth were studied. Results. The utilization of gaseous emissions by Chlorella vulgaris depends on the content of nitrogen and sulfur oxides that are constantly supplied to the cultivation medium, the initial biomass concentration, and pH. It was determined that for an initial cells concentration of (85 ± 5)×104 cells/ml in the culture medium, the threshold values of acids that do not cause significant changes in the cultivation process are 0.1% H₂SO₄ and 0.19% HNO₃. At a sulfuric acid concentration of 0.2%, the culture cells become discolored. Conclusions. It is shown that with a constant supply of sulfuric or nitric acids above the threshold values of 0.1% H2SO4 and 0.19% HNO3, the pH of the culture medium decreases, leading to the suspension of deve­lopment and the death of the Chlorella vulgaris culture. Therefore, controling these parameters will improve the ecological state of the environment and form the basis for developing biotechnology for the utilization of gas emissions by microalgae.

Additives to cracking catalyst based on MeOx/Al2O3 systems (Me = Cu, Fe, Ce, Co, Mn and La) to reduce the content of nitrogen oxides in regeneration gases

The influence of the nature of nitrogen-containing compounds introduced into a model cracking feedstock (n-hexadecane) on the composition of regeneration gases formed during catalyst regeneration was studied. An increase in the content of CO and NOx in the composition of regeneration gases was observed with an increase in the basicity and molecular weight of nitrogen compounds in the range: pyridine < n-butylamine < pyrrole < quinoline < indole. The effect of a Pt-based CO promoter on the composition of regeneration gases was studied. The use of a CO promoter reduces CO emissions by 99.4% but leads to a significant increase in NOx emissions. Additives were synthesized and studied to reduce the content of nitrogen oxides in the regeneration gases of a cracking catalyst. The additives were mixed oxides containing Cu, Fe, Ce, Co, Mn and La deposited on γ-alumina. The use of these additives at the stage of regeneration of the cracking catalyst led to a decrease in the content of nitrogen oxides formed during regeneration. For an additive based on copper oxide, the efficiency of reducing the content of nitrogen oxides in regeneration gases reached 12.2%.

Deactivation Mechanism of Spent TiO2-Based Selective Catalytic Reduction (SCR) Catalysts and State-of-the-Art Recycling Technologies.

Nitrogen oxides (NOx) make up a group of gases that are mainly formed during the combustion of fossil fuels at high temperatures. NOx contributes to environmental degradation by forming acid rain and enhancing global warming. Exposure to air with a high concentration of NOx can aggravate respiratory diseases, particularly asthma. The elimination of NOx in practical applications mainly proceeds through selective catalytic reduction (SCR) of NOx with NH3 to harmless N2 and H2O. One practical issue of the SCR process is the deactivation of TiO2-based SCR catalysts. In addition, growing numbers of spent SCR catalysts present a serious waste-management challenge for recyclers at end of life. It is therefore crucial to disclose the deactivation mechanism of the spent TiO2-based NH3-SCR catalysts and propose effective recycling technologies for waste valorization. Here we outline the catalyst deactivation pathways for TiO2-based SCR catalysts and critically review methods of improving the direct sustainability of spent catalysts, in areas such as direct regeneration and recovery of spent catalysts. Through this review, the challenges, solutions, and future strategies for handling spent SCR catalysts are clarified for future studies of application on an industrial scale.

Indoor Air Quality in a Museum Storage Room: Conservation Issues Induced in Plastic Objects

This study focuses on assessing the indoor air quality in a storage room (SR) belonging to Museo Nazionale Scienza e Tecnologia Leonardo da Vinci in Milan (MUST), covering pollutants originating from outdoor sources and emissions from historical plastic objects made from cellulose acetate (CA), cellulose nitrate (CN), and urea–formaldehyde (UF) stored in metal cabinets. The concentrations of SO2 (sulphur dioxide), NO2 (nitrogen dioxide), NOx (nitrogen oxides), HONO (nitrous acid), HNO3 (nitric acid), O3 (ozone), NH3 (ammonia), CH3COOH (acetic acid), and HCOOH (formic acid) were determined. The concentrations of SO₂, O₃, and NOx measured inside the metal cabinets were consistently lower compared to the other sampling sites. This result was expected due to their reactivity and the lack of internal sources. The SR and metal cabinets showed similar concentrations of NO and NO2, except for CA, where a high NO concentration was detected. The interaction between the CA surfaces and NO2 altered the distribution of NO and NO2, leading to a significant increase in NO. The presence of HNO3 potentially led to the formation of ammonium nitrate, as confirmed by ER-FTIR measurements. High levels of HONO and HNO3 in CN and NH3 in the UF indicate object deterioration, while elevated concentrations of CH3COOH in CA and HCOOH in the SR suggest specific degradation pathways for cellulose acetate and other organic materials, respectively. These results could direct conservators towards the most appropriate practical actions.

Research on optimization technology of ventilation system in an industrial X-ray inspection workshop

Objective: To investigate the reasonable airflow organization and exhaust system facilities during the operation of the inspection workshop, and solve the problem of the accumulation of harmful gases such as ozone and nitrogen oxides in the workshop. Methods: In May 2023, computational fluid dynamics (CFD) technology was used to numerically simulate the diffusion of ozone and nitrogen oxides generated by industrial radiographic inspection operations, and the comparative detection method was used to analyze the ozone and nitrogen oxides concentrations before and after the renovation of the ventilation system of the inspection workshop. Results: After the renovation of ventilation system, the average concentration of ozone in the inspection workshop decreased from 0.81 mg/m(3) to 0.03 mg/m(3), and the average concentration of nitrogen oxides decreased from 0.42 mg/m(3) to 0.01 mg/m(3), and the differences were statistically significant (t=20.51, 10.38, P<0.001) . Conclusion: The ventilation facilities of the inspection workshop are set up in the airflow organization mode of sending up and down the exhaust, and the ventilation pipes are scientifically designed through the calculation of ventilation hydraulic balance, which can effectively control the concentration of harmful gases in the inspection workshop.

Combustion characteristics of a 660 MW tangentially fired pulverized coal boiler considering different loads, burner combinations and horizontal deflection angles

In the context of transitioning energy structures, thermal power generation is adapting to peak load regulation, highlighting the need for comprehensive studies on boiler combustion characteristics under varying load conditions. This study focuses on a 660 MW tangentially fired boiler, evaluating its combustion and pollutant generation at different operational loads: boiler maximum continuous rate (BMCR), turbine heat acceptance (THA), 75% of THA, and 40% of THA. The findings reveal a general decline in temperature, and nitrogen oxide concentration as the load decreases. However, at 40% THA, increased oxygen mole fractions lead to higher carbon dioxide and sulfur dioxide levels compared to other conditions. Through the Analytic Network Process, each parameter's impact is evaluated and scored to identify the most effective burner and deflection angle combinations. Optimal configurations are identified: a 10-degree rightward adjustment for ABDE layer burners at BMCR and a 10-degree leftward adjustment for BD layer burners at 40% THA, both enhancing combustion performance and reducing pollutants at the furnace outlet. For THA and 75% THA conditions, the industrial standard combination is recommended.

Forecast of NOx Emissions for a 660MW Coal-Fired Boiler with Multilayered Gradient Boosting Decision Tree Considering Multiple Operating Modes.

Nitrogen oxides (NOx) are among the primary pollutants emitted by coal-fired power plants. Accurate prediction of NOx concentrations at the boiler outlet is crucial for optimizing unit control and reducing emissions. This study introduces a data-driven NOx emissions prediction methodology based on a multilayered Gradient Boosting Decision Tree (mGBDT) framework. Initially, Kernel Independent Component Analysis (KICA) is employed to eliminate nonlinear correlation among collected auxiliary variables. Subsequently, high-quality variables, grounded in physical mechanisms, are integrated with the extracted independent features. The robust Gaussian Mixture Model (RGMM) is then applied to capture the intrinsic multimode operational characteristics from these integrated features. Finally, local mGBDT-based NOx emissions prediction models are developed for each identified mode. The optimal hyperparameters for each local model are determined using Particle Swarm Optimization (PSO) and 10-fold cross-validation techniques. Utilizing historical measurements from the studied boiler, the proposed framework achieved a square of correlation coefficient (R 2) of 0.947, a root-mean-square error (RMSE) of 6.09 mg/m3, and a mean absolute error (MAE) of 4.009 mg/m3, outperforming five comparison models.

Research on the impact of nitromethane on the combustion mechanism of ammonia/methanol blends

Ammonia/methanol co-combustion is considered an effective liquid-liquid blending strategy to enhance the combustion performance of ammonia. However, both methanol and ammonia have high latent heats of vaporization, which necessitate significant heat absorption during the vaporization process. This often results in excessively low ambient temperatures before the ignition of the mixture, negatively affecting low-temperature ignition and combustion. To improve the combustion characteristics of ammonia/methanol blends, this study proposes the addition of nitromethane, forming a ternary blend of ammonia/methanol/nitromethane to enhance fuel performance. To evaluate the impact of nitromethane on the combustion mechanism of ammonia/methanol blends, this study utilizes synchronous vacuum ultraviolet photoionization mass spectrometry to analyze the oxidation reactions of the ammonia/methanol/nitromethane blends. Based on the Brequigny model, cross-reactions involving C-N bonds and reactions related to nitromethane were incorporated for model modification, resulting in the newly modified model, termed A-M. Pathway and sensitivity analyses, as well as ignition delay time simulations, were conducted to further understand the combustion process. The results indicate that the addition of nitromethane to the ammonia/methanol blend lowers the initial reaction temperature from 860 K to 740 K and increases nitrogen oxide (NOx) concentrations at 1050 K. At 800 K, nitromethane reduces the conversion of NH2 to NH3, thereby enhancing ammonia consumption and altering the NOx consumption pathway. Furthermore, at 1020 K, 98.6 % of H2NO reacts with H to form NH2, which is a crucial species in ammonia regeneration. Additionally, at 1020 K, 90.8 % of nitromethane decomposes through the reaction CH3NO2(+M) = CH3 + NO2(+M), contributing to increased NOx emissions. Moreover, the incorporation of nitromethane significantly reduces the ignition delay time of ammonia/methanol blends, demonstrating its potential to improve the overall combustion performance of these mixtures.

FeTiO3: A low-cost and efficient photocatalytic mineral for sustainable NOx abatement

This study investigates the potential of FeTiO3 as a photocatalyst for the removal of nitrogen oxides (NOx) from gas streams, a critical environmental and health concern. The photocatalytic activity of FeTiO3 was evaluated across a range of operational parameters, with initial NO concentrations set from 5 to 50 ppmv and gas hourly space velocity (GHSV) values of 18, 36, and 54 h−1. The findings demonstrate that FeTiO3 effectively converts NOx, even at room temperature and under saturated atmosphere, with a clear correlation between the photocatalytic removal efficiency and both the initial NO concentration and GHSV. A rigorous mechanism for the photooxidation of NO to nitrate via NO2 was proposed based on these experimental results and the surface characterization of raw and used ilmenite, corroborated by DFT calculations. These outcomes would allow widening the application of air pollution control strategies to flue gas with relatively low NOx concentration and low temperature, where other NOx control techniques show severe drawbacks. Therefore, this research contributes to the development of efficient and sustainable approaches for air quality improvement using photocatalytic systems.

In-tunnel pollutant concentration measurement and ventilation control indexes for highway tunnels in mountainous area: A case study of no.1 Qinling tunnel, China

The pollutant concentration and hygiene standards in mountain tunnels are key factors determining the ventilation effectiveness of tunnel operation. Previous studies have mainly focused on the spatiotemporal distribution patterns of in-tunnel pollutants, while research on ventilation control indexes for pollutants in long mountain tunnels are relatively limited. Therefore, this paper aims to discussing the hygiene control indexes for operational ventilation of mountain tunnels. Field tests were conducted in the No.1 Qinling Tunnel of Xi'an to Han zhong Highway in China, and the distribution laws of traffic flow, wind speed, and concentrations of particulate matter (PM), carbon monoxide (CO), and nitrogen oxide (NOX) were on-site measured. The spatiotemporal distribution characteristics of pollutants in the long mountain tunnel were revealed, and the ventilation hygiene control indexes for harmful gases were calculated and compared to those of urban highway tunnels. The results show that the traffic volume of operational highway tunnels in mountainous areas of China is increasing rapidly, and the particulate matter emitted from diesel vehicle exhaust will pose a threat to the normal environmental quality in the tunnel. The average value of CO base emission factor in 2000 for the upline of No.1 Qinling tunnel was 0.0019 m3/(veh·km) by back-calculation, and the annual decline rate of CO in the ventilation design for mountain highway tunnels should be 6 %–8 % and revised every 8 years. It is recommended to consider the geographical location and traffic conditions of mountain tunnels when calculating the air demand required for diluting NO2. NOx has basically replaced CO as the primary pollutant with the most significant impact on human health in mountain tunnels. It is recommended that NOX be considered as the primary hygiene control indicator in the ventilation design of mountain tunnels in China. The pollutant distribution and ventilation control indexes of mountain and urban highway tunnels are quite different, which should be treated differently in engineering applications. The research results can provide a significant reference for ventilation design and environmental evaluation of highway tunnels in mountainous areas.

Implementation of Regenerative Thermal Oxidation Device Based on High-Heating Device for Low-Emission Combustion

In this paper, a heating device is implemented by considering two large factors in a 100 cmm RTO design. First, when the combustion chamber is used for a long time with a high temperature of 750–1100 °C depending on the high concentration VOC gas capacity, there is a problem that the combustion chamber explodes or the function of the rotary is stopped due to the fatigue and load of the device. To prevent this, the 100 cmm RTO design with a changed rotary position is improved. Second, an RTO design with a high-heating element is implemented to combust VOC gas discharged from the duct at a stable temperature. Through this, low-emission combustion emissions and energy consumption are reduced. By implementing a high heat generation device, the heat storage combustion oxidation function is improved through the preservation of renewable heat. Over 177 h of demonstration time, we improved the function of 100 cm by discharging 99% of VOC’s removal efficiency, 95.78% of waste heat recovery rate, 21.95% of fuel consumption, and 3.9 ppm of nitrogen oxide concentration.

Numerical investigation of pre-chamber holes diameter geometry on combustion parameters in a hydrogen-powered Turbulent Jet Ignition engine

The search for substitutes for conventional fuels leads to the use of hydrocarbon-free or synthetic fuels. One of them is hydrogen. The use of hydrogen in combination with a two-stage charge creation system leads to the combustion of lean (λ &gt; 1) or very lean (λ &gt; 3) charges. The simulation tests carried out were aimed at determining the best configuration of the chamber connecting the prechamber with the main combustion chamber. Three variants of the diameter of the holes connecting the chambers were selected (d = 0.5; 1.0 and 1.5 mm) in combination with different fuel doses fed to the prechamber. A passive chamber (qo_PC = 0 mg) and an active chamber (qo_PC = 0.4 and 1.2 mg) were used, while simultaneously sending a dose of fuel to the main chamber (qo_MC = 6 mg). The research was conducted using AVL Fire 2022.1 software using the moving mesh of the LDV engine. As a result of simulation work, the most favorable conditions for carrying out the process were determined, considering the thermodynamic effects of the process and the accepted values of nitrogen oxide concentration. The resulting correlation maps of the sizes of the chamber openings and the fuel doses fed to the prechamber may determine the initial selection of possibilities for controlling hydrogen combustion in the TJI system.

How do meteorological conditions impact the effectiveness of various traffic measures on NOx concentrations in a real hot-spot?

Recently, air quality has become a major concern for policy makers around the world, which has led to the implementation of mitigation measures. In particular, in urban areas most measures affect the road transport sector, as this is one of the main contributors to air pollution in those areas. Recent studies have pointed out the need to determine the importance of external factors such as the meteorological conditions on the net effect on air quality of mitigation strategies. Due to the strong spatial variability of urban air pollution, high spatial resolution modelling is necessary. In this work, the impacts on emissions and nitrogen oxides (NOx) concentrations of several mitigation strategies on a real air pollution hot spot in southern Madrid (Spain) are simulated at microscale under different meteorological conditions. The results show that the meteorological conditions affect local NOx concentrations, and its net changes can be comparable to those due to emission reductions. In particular, meteorological conditions in 2019 induced higher NOx concentrations than in 2016, despite the local emissions were reduced by 50 % from 2016 to 2019. On the other hand, the impact of the implementation of a Low Emissions Zone (LEZ) on NOx concentrations is small and consistent with values found in other LEZs around Europe. However, this impact varies up to 70 % depending on the meteorological conditions. The impacts of a mitigation strategy are largely influenced by the meteorological conditions, and therefore the achievement of the target reduction of concentrations pursued by these measures will depend on the meteorological conditions.