Nitrogen Monoxide Concentrations Research Articles

The Role of Asprosin in the Regulation and Mechanisms of Oxygen Transport in the Blood and the Gas Transmitter System in Men with Different Body Mass Index

The purpose of this study the role of asprosin in the regulation and mechanisms of oxygen transport in the blood and the gas transmitter system in men with different body mass index. The indicators of lipid and carbohydrate metabolism, as well as the oxygen transport function of the blood and the concentration of gas-transmitters nitrogen monoxide and hydrogen sulfide in it, were determined. A higher concentration of asprosin was found in individuals with an increased body mass index and grade I obesity. With an increased content of asprosin, there is a decrease in the main indicators of blood oxygenation and an increase in the affinity of hemoglobin for oxygen. An increase in the concentration of nitrogen monoxide and a decrease in hydrogen sulfide were revealed at a high content of asprosin, which may be important for the formation of the mechanisms of oxygen transport in the blood.

NO at low concentration can enhance the formation of highly oxygenated biogenic molecules in the atmosphere

The interaction between nitrogen monoxide (NO) and organic peroxy radicals (RO2) greatly impacts the formation of highly oxygenated organic molecules (HOM), the key precursors of secondary organic aerosols. It has been thought that HOM production can be significantly suppressed by NO even at low concentrations. Here, we perform dedicated experiments focusing on HOM formation from monoterpenes at low NO concentrations (0 – 82 pptv). We demonstrate that such low NO can enhance HOM production by modulating the RO2 loss and favoring the formation of alkoxy radicals that can continue to autoxidize through isomerization. These insights suggest that HOM yields from typical boreal forest emissions can vary between 2.5%-6.5%, and HOM formation will not be completely inhibited even at high NO concentrations. Our findings challenge the notion that NO monotonically reduces HOM yields by extending the knowledge of RO2-NO interactions to the low-NO regime. This represents a major advance towards an accurate assessment of HOM budgets, especially in low-NO environments, which prevails in the pre-industrial atmosphere, pristine areas, and the upper boundary layer.

Experimental Investigation of the Influence of NO on a PEM Fuel Cell System and Voltage Recovery Strategies

Air contaminants can have detrimental effects on the performance and durability of proton exchange membrane (PEM) fuel cell vehicles. This research focuses on the experimental investigation of the effect of nitrogen monoxide (NO) in the cathode gas stream, which provokes a cell voltage decrease due to the partially reversible adsorption of NO on the platinum catalyst. The concentration and exposure time of NO in the cathode gas stream are varied at selected constant current densities and load ramps to assess the effects throughout the fuel cell system operating range. The results show the cell voltage loss in the presence of NO and reveal a near-catalyst saturation with increased injected NO mass. Additionally, several voltage recovery and mitigation strategies are introduced and discussed by presenting conclusions about the general effect of NO on a fuel cell system in operation. The most promising recovery strategy for fuel cell systems is identified, and the overall system degradation is discussed. All experiments are performed in a test bed environment on a 25 kW low-temperature fuel cell system via controlled injection of NO into the cathode gas stream.

Oxygen-Dependent Blood Processes in Beck's Sarcoidosis

The objective: to assess the state of oxygen-dependent blood processes in patients with Beck's sarcoidosis.Subjects and Methods. Parameters of blood oxygen transport function and free radical lipid oxidation, as well as the content of nitrogen monoxide and hydrogen sulfide gas transmitters were assessed in the blood of 75 patients (41 women; 34 men) with Beck's sarcoidosis, stage 2 (the pulmonary mediastinal form).Results. In the pulmonary mediastinal form of sarcoidosis versus healthy individuals, there was a decrease in the degree of blood oxygen saturation from 65.4 (60.6; 67.8) to 41.50 (36.0; 49.8), p < 0.05, %, partial oxygen pressure from 40.0 (38.0; 47.0) to 23.0 (18.3; 29.0) mmHg, p < 0.05, and blood pH increased. A decrease in the index of hemoglobin affinity to oxygen p50real (26.80 (24.70; 31.40), p < 0.05, versus healthy individuals 28.2 (27.9; 29.1) mmHg) was revealed. The level of diene conjugates increased in plasma by 86.4% (p < 0.05) and malondialdehyde increased in erythrocytes by 139.2% (p < 0.05), while the following parameters decreased: α-tocopherol (by 42.7 %, p < 0.05), retinol (by 41.9%, p < 0.05), reduced glutathione (by 30.4%, p < 0.05), and ceruloplasmin (by 22.3%, p < 0.05) in plasma. There was an increase in the concentration of nitrogen monoxide (from 15.42 (14.48; 17.71) to 17.09 (7.04; 25.09), mmol/L) and a decrease in hydrogen sulfide (from 29.01 (25.21; 37.03) to 13.08 (8.63; 20.46), mmol/L) in the blood in case of this pathology.Conclusion. There is a deterioration in the blood oxygen-binding properties in patients with Beck's sarcoidosis, stage 2, and as a consequence, tissue needs in oxygen are not adequately provided by blood circulation. There is an increase in the concentration of nitrogen monoxide and a decrease in hydrogen sulfide, which affects the oxygen transport function of blood which may be important for ensuring the processes of oxygen transfer to tissues. In this pathology, activation of lipid peroxidation and a decrease in the level of antioxidant protection factors of blood were revealed which might be important for the genesis of this disease.

Oxygen-binding properties of blood in insulin resistance with different asprosin content.

The oxygen-binding properties of blood were studied in male patients with insulin resistance (IR) with different levels of asprosin. The content of asprosin, parameters of blood oxygen transport function, as well as gas transmitters, nitrogen monoxide and hydrogen sulfide, were determined in the venous blood plasma. In the studied IR patients with increased blood asprosin content, impaired blood oxygenation was noted; IR patients with normal body weight had increased hemoglobin affinity for oxygen, while in IR patients with overweight and the 1st degree obesity, this parameter decreased. The detected increase in the concentration of nitrogen monoxide and the decrease in hydrogen sulfide may be important for the oxygen-binding properties of the blood and the development of metabolic imbalance.

Effect the Addition of Biodiesel from Nyamplung Oil (Calophyllum Inophyllum) on Performance and Emission Characteristics of Diesel Engines

In this study, the use of biodiesel from nyamplung oil (Calophyllum Inophyllum) was studied through a transesterification reaction using a heterogeneous catalyst of CaO from limestone originating from Pamekasan, Madura. The composition ratio used between nyamplung oil and methanol in the transesterification reaction was 1:12 (mol/mol) with the addition of 4% CaO catalyst. The biodiesel that is formed is then tested for its performance and emission characteristics in diesel engines with various fuel mixtures between pure diesel and biodiesel (B-10, B-20, B-30, B-40, B-100 and S-100). The test results for biodiesel blends with the highest power produced from B-10, B-20, B-30 and B-100 fuels were 0.26 kW each at a load of 250 watts. While at a load of 500 watts, the highest power is obtained from the B-40 fuel, which is 0.58 kW. The results of performance testing using S-100 fuel obtained the highest power values ​​of 0.27 and 0.58 kW, respectively, with a load of 250 and 500 watts. Performance testing for biodiesel blends, the highest torque value was obtained when using B-10, B-20, B-30 and B-100 fuels, which were 1.65 N.m each with a load of 250 watts. While at a load of 500 watts, the highest torque is obtained on B-40 fuel, which is 3.69 N.m. The fuel S-100 produces torque of 1.71 and 3.69 N.m, respectively, with a load of 250 and 500 watts. Emission gases characteristics of carbon monoxide (CO), nitrogen monoxide (NO) and nitrogen oxides (NOx) showed the lowest concentrations obtained in B-100 fuel were 387 ppm, 92 ppm and 96 ppm, respectively. Meanwhile, the highest concentrations of CO, NO and NOx emissions were produced from pure diesel fuel (S-100), namely 574 ppm, 126 ppm and 132 ppm, respectively.

Changes in physiological responses and immunity of blunt snout bream Megalobrama amblycephala from transport stress.

This study aimed to investigate the effects of transport stress on the physiological responses and immunity of Megalobrama amblycephala (blunt snout bream). Fish (109.67 ± 1.51g) were sampled at nine time points: before transport (control), at 0h, 1h, 3h, 6h, 12h, 24h, 3days, and 7days after 4h of medium-distance transportation, and four fish were sampled in each time point. The results showed that plasma cortisol, triiodothyronine (T3), complement component 3 (C3), complement component 4 (C4), immunoglobulin M (IgM) and nitrogen monoxide (NO) concentrations, and alternative complement pathway (ACH50), acid phosphatase (ACP), and myeloperoxidase (MPO) activities all reached the peak at 0h after transportation; C4 and NO concentrations as well as ACP and MPO activities returned to the control level after 1h, ACH50 activity as well as cortisol, T3, and IgM concentration returned to the control level after 12h, and C3 concentration returned to the control level after 24h respectively. Plasma glucose and total protein concentrations as well as lysozyme activity all reached the peak at 1h after transportation, total protein concentration and lysozyme activity returned to the control level after 3h, and glucose concentration returned to the control level after 6h (P < 0.05). Liver heat shock protein 70 expression reached the peak at 1h after transportation, and returned to the control level after 24h; liver heat shock protein 90 expression reached the peak at 0h after transportation and returned to the control level after 12h (P < 0.05). Overall, these findings suggested that 4h of medium-distance transportation caused stress response of blunt snout bream, and transport stress had a significant effect on plasma indicators. But the recovery of 24h after transport could return the physiological response, immune indexes, and the expression of heat shock protein to the normal level. This also provided data support for the medium-distance transportation of blunt snout bream in the future.

Effect of corvitin on oxygen homeostasis and blood gas transmitters in ischemia-reperfusion of the lower limbs

Introduction.Reperfusion-reoxygenation syndrome (RRS) after revascularization of the lower limbs in obliterating atherosclerosis of the arteries is accompanied by a violation of the oxygen transport function of the blood (OTFB) and the content of gas transmitters (GTs). Reperfusion injury affects not only the tissues of the lower limbs, but also of anatomically distant organs, which supposes that effective RRS correction is required. Aim. To study the effect of Corvitin on the OTFB parameters and the content of GT of nitrogen monoxide (NO) and hydrogen sulfide (H2S) in the venous blood of the forearm after revascularization of the lower limb in chronic atherosclerotic occlusion of the superficial femoral artery (SFA).Materials and methods.The study included 118 male patients. Revascularization of the lower limb was carried out by the method of loop endaterectomy from the SFA. Patients of group I (n=52) received traditional medication, 51 patients of group II additionally received Corvitin. In the blood from the vein of the elbow bend before the operation, on the 3rdand 8thdays after it, the indices of OTFB and GTs were determined.Results.In group I, on the 3rdday after surgery, pO2increased in relation to healthy individuals by 5.2–18.5%, while pCO2decreased by 4.8–6.7%, depending on the stage of initial ischemia. The concentrations of NO and H2S increased by 9.2–50.1% and 9.2–21.1%, respectively. The increase in the parameters of hyperoxemia, hypocapnemia and GT after the return of blood circulation decreases with the use of Corvitin (p˂0.05). By the end of the early postoperative period, the indicators of OTFB and GT not only return to their initial values, but also do not significantly differ from the group of healthy individuals (p˃0.05).Conclusion.The use of Corvitin effectively corrects violations of OTFB and GT during ischemia-reperfusion of the lower limbs, which prevents tissue reperfusion damage.

A dual-channel incoherent broadband cavity-enhanced absorption spectrometer for sensitive atmospheric NOx measurements.

We describe and characterize a dual-channel incoherent broadband cavity-enhanced absorption spectrometer (DC-IBBCEAS) for the sensitive measurements of NOx: the sum of nitrogen monoxide (NO) and nitrogen dioxide (NO2) in the atmosphere. The instrument employs two 1 m long optical cavities, with air being extracted from a common sampling line. The first channel (cavity-1) spans 340-380 nm and the second channel (cavity-2) spans the 405-460 nm spectral range, both measuring NO2 simultaneously. High absorption cross-sections of NO2 in both channels are effectively utilized for its sensitive quantification. NO is quantified by titrating it with ozone to NO2 in channel-2, where the difference of NO2 measured from that in channel-1 corresponds to the NO concentration in the sampled air. The instrument offers 1-ppb detection sensitivity for both NO and NO2 with a maximum possible uncertainty of ∼9%. The use of close yet different spectral regions in the two channels readily extended measurements to a broader range without compromising its sensitivity to NOx quantification. This would extend the DC-IBBCEAS applicability to simultaneously monitor interfering species with significant absorption cross-sections in the region in either channel, such as glyoxal (CHOCHO), methylglyoxal (CH3COCHO), and nitrous acid (HONO).

Long-term effects of outdoor air pollution on mortality and morbidity–prediction using nonlinear autoregressive and artificial neural networks models

The daily association between mortality and air pollution is alarming and there is consistent evidence that air pollution has short-term effects on mortality and respiratory morbidity. Accurate predictions of these health effects of air pollution are essential for efficient planning of various sectors related to economic performances as well as strategic management to improve human health and air quality. The main objectives of this research were to determine the long-term effects of air pollution on respiratory morbidity and mortality with the Dickey-Fuller test as well as develop accurate prediction of respiratory morbidity and mortality with nonlinear autoregressive and artificial neural network models. This study examined daily variations in respiratory mortality and morbidity attributed to air pollutants in Ahvaz for 9-yrs period. The results showed that nitrogen monoxide and carbon monoxide have significant effect on total respiratory mortality. The sensitivity analysis and ADF test showed that the other pollutants (NO2, SO2, O3, PM10) had no significant effect on the total respiratory morbidity and mortality rate. For the nonlinear autoregressive model, topology 2-10-1 with two input, including nitrogen oxide and carbon oxide, ten hidden layers were the best (MSE = 0.1 and R = 0.82) for predicting the total mortality rate. Artificial neural network and nonlinear autoregressive models are very powerful methods for accurate prediction of respiratory mortality and mobility with at least three inputs. These findings strongly support the need for policymakers to set targets to reduce carbon monoxide and nitrogen monoxide concentrations in the environment.

Risk of Polycystic Ovary Syndrome in Women Exposed to Fine Air Pollutants and Acidic Gases: A Nationwide Cohort Analysis.

Background: Air pollutants cause endocrine disorders and hormone disruption. The relationship between air pollutants and polycystic ovary syndrome (PCOS) must be carefully investigated using a nationwide cohort. Methods: Data were extracted from two nationwide databases, namely Longitudinal Health Insurance Database and Taiwan Air Quality Monitoring Database, and analyzed. The study considered a range of data that began on 1 January 2000 and ended on 31 December 2013. Women diagnosed with PCOS were excluded. From the residential data, the study assessed the daily concentrations of sulfur dioxide (SO2), nitrogen oxides (NOx), nitrogen monoxide (NO), nitrogen dioxide (NO2), and PM2.5 the women were exposed to. A Cox proportional hazard regression model was applied to assess PCOS risk. Results: In total, 91,803 women were enrolled in this study; of those women, 2072 developed PCOS after 12 years of follow-up. The mean daily concentrations of SO2, NOx, NO, NO2, and PM2.5 women were exposed to were 4.25 (±1.44) ppb, 20.41 (±6.65) ppb, 9.25 (±4.36) ppb, 20.99 (±3.33) ppb, and 30.85 (±6.16) μg/m3, respectively. Compared with the first-quartile levels of exposure, the fourth-quartile levels of exposure to SO2, NOx, NO, NO2, and PM2.5 increased PCOS risk by 10.31 times (95% CI = 8.35–12.7), 3.37 times (95% CI = 2.86–3.96), 4.18 times (95% CI = 3.57–4.89), 7.46 times (95% CI = 6.38–8.71), and 3.56 times (95% CI = 3.05–4.15), respectively. Conclusion: Women exposed to a high concentrations of air pollutants, namely SO2, NO, NO2, NOx, and PM2.5, had a high PCOS risk.

Development of an analytical chip for nitrogen monoxide detection using porous glass impregnated with 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl

Nitrogen monoxide (NO) is an important bio-regulatory molecule. NO presence in exhaled breath is a biomarker for an airway inflammation. Thus, measuring NO in the exhaled air is considered a noninvasive method for disease screening. In this study, we developed an analytical chip made of porous glass impregnated with 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl (PTIO) for NO gas detection. The analytical chip had an absorption peaks at 338 and 567 nm, which decreased when exposed to NO, whereas the absorbance at 413 nm increased with an isosbestic point at 477 nm. It was found that there is a linear relationship between the logarithmic change in the absorbance at 338 nm and 567 nm and the cumulative NO concentration. Additionally, the spectrum of the analytical chip was affected by humidity. There was a linear relationship between the PTIO's molar absorption coefficient at 567 nm and the relative humidity. Therefore, the absorbance of PTIO can be corrected in order to take the effect of humidity into consideration. The working ranges of the analytical chip were between 0.15 and 3.7 ppm × h of cumulative NO concentration and at a relative humidity between 40% and 90%. We also measured NO in a small amount of air (1.8 L to mimic the actual exhaled air volume) and we were able to measure the NO concentration of 30 ppb for 24 h.

MODELLING, SIMULATION AND PARAMETER IDENTIFICATION OF ACTIVE POLLUTION REDUCTION WITH PHOTOCATALYTIC ASPHALT

We develop and implement a numerical model to simulate the effect of photocatalytic asphalt on reducing the concentration of nitrogen monoxide (NO) due to the presence of heavy traffic in an urban environment. The contributions in this paper are threefold: we model and simulate the spread and breakdown of pollution in an urban environment, we provide a parameter estimation process that can be used to find missing parameters, and finally, we train and compare this simulation with different data sets. We analyse the results and provide an outlook on further research.

Assessment of Air Pollution over Baghdad City Using Fixed Annual Stations and GIS Techniques

Baghdad, considered one of the most polluted and populated cities in Iraq, waschoosen for mapping the distribution of air pollutants and the overall pollution levels by using the ArcGIS techniques. Six of main observation stations werechoosen in a particular location. Then, the recorded data from these stations were spatially interpolated using two types of ArcGIS interpolation techniques. The spatial interpolation techniques used in this work were Inverse distance weighting (IDW) and fuzzy logic. This study includes measuring the main air pollutants, which were nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen oxide (NOx), and nitrogen monoxide (NO) during the period from January 2018 to December 2018. The data recorded by the stations during the work period and the distribution maps of air pollutants, which resulted from spatial interpolation (IDW) method, showed that the concentration of NO2 was within the International limits of World Health Origination (WHO) which is about 0.11 ppm. SO2 concentrations were exceeding the WHO limits in all stations for the study area. The concentrations of CO ranged from 0.484 ppm to 7.027 ppm that were within acceptable limits of WHO standards that is 9 ppm. NOx concentrations ranged between 0.01506 ppm – 0.214 ppm, which were exceeding acceptable limits of WHO standards (0.01 ppm). The concentrations of NO did not exceed the WHO standard limits, which are 0.08 ppm. Finally, the fuzzsy logic method of spatial interpolation in ArcGIS was applied to evaluate the air pollution over Baghdad city.

In situ NO abatement by photocatalysis—study under continuous NO injection in a 10-m3 experimental chamber

Air pollution is a serious public health concern in France and many other countries. Nitrogen oxides (NOx) include nitrogen monoxide (NO) and nitrogen dioxide (NO2). They are mainly outdoor pollutants produced during combustion of fossil fuel. These gases can easily infiltrate buildings and thus increase indoor pollution. The recommended guideline values for NO2 are 200 μg/m3 (short-term exposure) and 40 μg/m3 (long-term exposure). Although no guideline values exist for NO, this gas can be oxidised by atmospheric ozone and thus produce NO2. This paper studies the depollution efficiency of photocatalysis towards indoor NO. Experiments were conducted at real scale, in a 10-m3 experimental chamber developed at the LMDC and used as a reactor. The interior walls of the chamber were equipped with painted plasterboards treated with photocatalytic coating (3 g/m2 of TiO2). Gas was continuously injected into the chamber according to a specific procedure: (1) pollutant injection at high flow rate to reach 200 ppb of NO, (2) pollutant injection at low flow rate in order to keep the NO concentration constant at 200 ± 10 ppb and (3) photocatalysis activation by switching on the light. Typical indoor lighting systems (fluorescent tubes, LED and halogen bulbs) were tested and UV fluorescent tubes were also used to optimise the photocatalytic efficiency. Results showed that NO indoor concentration was reduced by photocatalysis in real-world conditions. Significant NO degradation was obtained under visible light. In addition, using the experimental procedure presented in this paper, a new method for evaluating air depollution efficiency by photocatalysis at real scale is proposed.

Modeliranje procesa u eksperimentalnoj komori za denitrifikaciju produkata sagorevanja biomase

In spite of the many advantages that promote biomass as a renewable energy source, its combustion emits certain pollutants, as any other fuel. Although these negative effects are less pronounced compared to the combustion of fossil fuels, they need to be identified and controlled. The nitrogen oxides (NOx) emission generated from the biomass combustion is one of the key challenges, and their controlling is necessary in order to meet the legal emission limit and to develop high-quality biomass combustion technologies. For a better understanding of the process of NOx reduction, the experimental apparatus was designed for testing of the secondary denitrification techniques at the biomass combustion. This paper provides a description of the experimental installation. Before accessing extensive experiments, it is very useful and important to carry out calculations and initial numerical simulations of processes that need to be in detail experimentally examined. The reactions of selective non-catalytic reduction of nitrogen-monoxide (NO) using ammonia (NH3) as a reagent are analyzed here first. The paper presents the dependence of the reaction rates of reduction and oxidation on the relation between NO and oxygen concentrations in the NH3-SNCR process under conditions of biomass combustion products. In the framework of the preparation of detailed experiments, a comprehensive CFD modeling of complex industrial denitrification processes has been applied, with a comprehensive process analysis including simulation of flow, mixing of components and monitoring of local chemical reactions, taking into account the effects of turbulence on global chemical kinetics.

NOx removal rate of photocatalytic cementitious materials with TiO2 in wet condition

Photocatalytic cementitious materials used in urban buildings are promising to mitigate air pollution sustainably. The changes of NO concentration in previous studies have been tested in dry condition while photocatalytic cementitious materials are mostly exposed to wetting and its water content continuously changes. This study presents the removal capacity of Nitrogen monoxide (NO) by using Titanium dioxide (TiO2) under wet condition. Under both dry and wet condition, NO removal rates were measured. For dry condition tests, dominant factors such as TiO2 particle size, TiO2 mass replacing ratio with respect to cement, and humidity were under consideration. The specimen under wet condition was subjected to the evaporation and the evolution of NO removal rate was continuously monitored. Results present that the recovery rate of removal capacity initially increased followed by the stationary phase where removal capacity stayed quasi-constant for a considerable time period in spite of continuous evaporation. Upon complete drying, the recovery rate was not fully restored due to the wetting experiment. The phenomena involved unique phases during evaporation were further discussed. The observation emphasizes that the consideration of wet condition is crucial to comprehend the NO removal capacity of photocatalytic cement-based materials in real urban environments.

Ozone Cross-Section Measurement by Gas Phase Titration.

Elevated values of ground-level ozone damage health, vegetation, and building materials and are the subject of air quality regulations. Levels are monitored by networks using mostly ultraviolet (UV) absorption instruments, with traceability to standard reference photometers, relying on the UV absorption of ozone at the 253.65 nm line of mercury. We have redetermined the ozone cross-section at this wavelength based on gas phase titration (GPT) measurements. This is a well-known chemical method using the reaction of ozone (O3) with nitrogen monoxide (NO) resulting in nitrogen dioxide (NO2) and oxygen (O2). The BIPM GPT facility uses state-of-the-art flow measurement, chemiluminescence for NO concentration measurements, a cavity phase shift analyzer (CAPS) for NO2 measurements, and a UV ozone analyzer. The titration experiment is performed over the concentration range 100-500 nmol/mol, with NO and NO2 reactants/calibrants diluted down from standards with nominal mole fractions of 50 μmol/mol. Accurate measurements of NO, NO2, and O3 mole fractions allow the calculation of ozone absorption cross section values at 253.65 nm, and we report a value of 11.24 × 10-18 cm2 molecule-1 with a relative expanded uncertainty of 1.8% (coverage factor k = 2) based on nitrogen monoxide titration values and a value of 11.22 × 10-18 cm2 molecule-1 with a relative expanded uncertainty of 1.4% (coverage factor k = 2) based on nitrogen dioxide titration values. The excellent agreement between these values and recently published absorption cross-section measurements directly on pure ozone provide strong evidence for revising the conventionally accepted value of ozone cross section at 253.65 nm.

Numerical investigation of soot formation and oxidation processes under large two-stroke marine diesel engine-like conditions using integrated CFD-chemical kinetics

In this reported work, multi-dimensional computational fluid dynamics studies of diesel combustion and soot formation processes in a constant volume combustion chamber and a marine diesel engine are carried out. The key interest here is firstly to validate the coupling of a newly developed skeletal n-heptane mechanism and a revised multi-step soot model using laser extinction measurements of diesel soot obtained at different ambient pressure levels in an optical accessible, constant volume chamber experiment. It is revealed that ignition delay times and liftoff lengths generated using the new skeletal model are close to those produced by the larger and more comprehensive chemical mechanisms, apart from those at the low pressure condition. The current study also demonstrates that the variation of averaged soot volume fraction with respect to the change of combustion chamber pressure captured using the revised soot model agrees reasonably well with the measurements in terms of peak values. The numerical model is subsequently applied to investigate the flame development, soot/nitrogen monoxide formation and heat transfer in a two-stroke, low-speed uniflow-scavenged marine diesel engine operating at full load condition, where optical measurements are not available. Comparisons to the experimental data show that the simulated pressure rise starts 1.0 crank angle degree in advance and the calculated peak pressure is 1.7% lower. The associated flame liftoff length is negligible, yielding higher local equivalence ratio and soot volume fraction values as compared to those under similar test condition in the constant volume chamber. With the use of the revised model, the total heat transfer to the walls calculated when soot radiative heat loss is taken into account is approximately 30% higher compared to that when only convective heat loss is considered. The averaged nitrogen monoxide concentration is 7.7% lower when both convective and soot radiative heat losses are accounted for but the net soot mass production is less sensitive to soot radiation. A sensitivity study reveals that neither increasing nor decreasing the soot absorption coefficient by 30% from the baseline setup is influential to nitrogen monoxide formation, soot mass production and heat transfer. The findings here aid to gain insights and provide a better understanding of the combustion and soot processes in large, uniflow-scavenged marine engines. The numerical model developed in this work can also be applied to explore different phenomena in this combustion system.

Dispersion modelling of emissions from vehicles along the urban section of a major highway

Vehicular emissions portend high risk to human health especially to inhabitants of highway environment. However, there is paucity of information on the inventory of air pollutants on Nigerian highways. Therefore, this study aimed at estimating the ground level concentrations of emissions associated with road traffic in the Ogbomoso-section of Ibadan-Ilorin highway. Three sampling locations (Idi-oro, General and Aroje) were selected within the Ogbomoso section of Ibadan-Ilorin highway for this study. Data collections on criteria air pollutants [carbon monoxide (CO), nitrogen monoxide (NO) and sulphur dioxide (SO2)] and total suspended particle (TSP) were made within dry and wet seasons. The results of predicted concentrations of CO, NO, SO2 and TSP ranged between 0.59-352.60, 0.28-213.40, 0.04-33.40 and 0.02-14.20 µg/m3, respectively. All the predicted concentration values of selected pollutants meet-up with the regulatory standards. This study has provided baseline inventory for criteria air pollutants in the Ogbomoso-section of Ibadan-Ilorin highway.