scholarly journals Sensitivity of Nitrate Aerosol Production to Vehicular Emissions in an Urban Street

Atmosphere ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 212 ◽  
Author(s):  
Minjoong J. Kim
Keyword(s):  
Ammonium Nitrate ◽  
Nox Emissions ◽  
Vehicular Emissions ◽  
Street Canyons ◽  
Urban Streets ◽  
Urban Street ◽  
Nitrate Production ◽  
Volatile Organic ◽  
Computational Fluid Dynamics Cfd ◽  
Nitrate Aerosol

This study investigated the sensitivity of nitrate aerosols to vehicular emissions in urban streets using a coupled computational fluid dynamics (CFD)–chemistry model. Nitrate concentrations were highest at the street surface level following NH3 emissions from vehicles, indicating that ammonium nitrate formation occurs under NH3-limited conditions in street canyons. Sensitivity simulations revealed that the nitrate concentration has no clear relationship with the NOx emission rate, showing nitrate changes of only 2% across among 16 time differences in NOx emissions. NOx emissions show a conflicting effect on nitrate production via decreasing O3 and increasing NO2 concentrations under a volatile organic compound (VOC)-limited regime for O3 production. The sensitivity simulations also show that nitrate aerosol is proportional to vehicular VOC and NH3 emissions in the street canyon. Changes of VOC emissions affect the nitrate aerosol and HNO3 concentrations through changes in the O3 concentration under a VOC-limited regime for O3 production. Nitrate aerosol concentration is influenced by vehicular NH3 emissions, which produce ammonium nitrate effectively under an NH3-limited regime for nitrate production. This research suggests that, when vehicular emissions are dominant in winter, the control of vehicular VOC and NH3 emissions might be a more effective way to degrade PM2.5 problems than the control of NOx.

scholarly journals Impacts of the Tree Canopy and Chemical Reactions on the Dispersion of Reactive Pollutants in Street Canyons

Atmosphere ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 34
Author(s):  
Franchesca G. Gonzalez Olivardia ◽  
Tomohito Matsuo ◽  
Hikari Shimadera ◽  
Akira Kondo
Keyword(s):  
Chemical Reactions ◽  
Urban Areas ◽  
Numerical Experiments ◽  
Tree Canopy ◽  
Observation Data ◽  
Street Canyons ◽  
Urban Street ◽  
Proposed Model ◽  
Tree Canopies ◽  
Computational Fluid Dynamics Cfd

Traffic-related air pollution in street canyons can cause health problems for pedestrians. In order to clarify the behavior of reactive pollutants, such as NOx and O3, in street canyons, a computational fluid dynamics (CFD) model coupled with a chemistry model and tree canopy model was developed, and then, a set of numerical experiments were performed to investigate the impacts of chemical reactions and aerodynamic effects of trees planted in a canyon. The results were compared with the observation data. Through the results of the numerical experiments designed to simulate a realistic urban street canyon, it was found that chemical reactions have a dominant impact on the NO/NO2 ratio and O3 concentration. While the tree canopy had little impact on the NO/NO2 ratio, it had a moderate impact on the flow field in the canyon and the amount of NOx and O3 in the canyon. In accordance with the aerodynamic effects of tree canopies, the local NOx concentration in the experiments increased and decreased by up to 51% and 11%, respectively. The current findings of this study demonstrate the utility of the proposed model for conducting air quality investigations in urban areas.

scholarly journals Numerical Study of Traffic Pollutant Dispersion within Different Street Canyon Configurations

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Yucong Miao ◽  
Shuhua Liu ◽  
Yijia Zheng ◽  
Shu Wang ◽  
Yuan Li
Keyword(s):  
Software Package ◽  
Street Canyon ◽  
Numerical Study ◽  
Turbulence Models ◽  
Pollutant Dispersion ◽  
Pollution Level ◽  
Street Canyons ◽  
Urban Street ◽  
Urban Street Canyons ◽  
Computational Fluid Dynamics Cfd

The objective of this study is to numerically study flow and traffic exhaust dispersion in urban street canyons with different configurations to find out the urban-planning strategies to ease the air pollution. The Computational Fluid Dynamics (CFD) model used in this study—Open Source Field Operation and Manipulation (OpenFOAM) software package—was firstly validated against the wind-tunnel experiment data by using three differentk-εturbulence models. And then the patterns of flow and dispersion within three different kinds of street canyon configuration under the perpendicular approaching flow were numerically studied. The result showed that the width and height of building can dramatically affect the pollution level inside the street canyon. As the width or height of building increases, the pollution at the pedestrian level increases. And the asymmetric configuration (step-up or step-down street canyon) could provide better ventilation. It is recommended to design a street canyon with nonuniform configurations. And the OpenFOAM software package can be used as a reliable tool to study flows and dispersions around buildings.

scholarly journals Comparative Exergy Analysis of Units for the Porous Ammonium Nitrate Granulation

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 280
Author(s):  
Dmytro Levchenko ◽  
Andrii Manzharov ◽  
Artem Artyukhov ◽  
Nadiya Artyukhova ◽  
Jan Krmela
Keyword(s):  
Ammonium Nitrate ◽  
Exergy Analysis ◽  
Evaporative Cooling ◽  
Energy Resources ◽  
Unit Mass ◽  
Brayton Cycle ◽  
Basic Scheme ◽  
Target Parameter ◽  
Effective Implementation ◽  
Nitrate Production

The article deals with the study on the efficiency of units for porous ammonium nitrate production. The ways which increase the effective implementation of energy resources are determined by including the ejector recycling module, heat and mass exchangers that utilize principles of regenerative indirect evaporative cooling, and the sub-atmospheric inverse Brayton cycle. Mixed exergy analysis evaluates all flows of the system contour as those of the same value. The target parameter for determining the efficiency of both systems is the ratio of the unit’s productivity to the exergy expenditures to produce the unit mass of the product. As a result, it is found that the mentioned devices and units enable to increase the efficiency of the basic scheme by 87%.

A review of strategies for mitigating roadside air pollution in urban street canyons

2021 ◽  
pp. 116971
Author(s):  
Yuhan Huang ◽  
Chengwang Lei ◽  
Chun-Ho Liu ◽  
Pascal Perez ◽  
Hugh Forehead ◽  
...  
Keyword(s):  
Air Pollution ◽  
Street Canyons ◽  
Urban Street ◽  
Urban Street Canyons

Positional error modeling of sky‐view factor measurements within urban street canyons

2021 ◽  
Author(s):  
Zian Wang ◽  
Guoan Tang ◽  
Guonian Lü ◽  
Cheng Ye ◽  
Fangzhuo Zhou ◽  
...  
Keyword(s):  
Error Modeling ◽  
View Factor ◽  
Positional Error ◽  
Street Canyons ◽  
Urban Street ◽  
Sky View Factor ◽  
Urban Street Canyons

Estimating the Effects of Urban Street Incidents on Capacity

2017 ◽  
Vol 2615 (1) ◽  
pp. 55-61 ◽  
Author(s):  
Aidin Massahi ◽  
Mohammed Hadi ◽  
Maria Adriana Cutillo ◽  
Yan Xiao
Keyword(s):  
Network Performance ◽  
Field Measurements ◽  
Signalized Intersection ◽  
Limited Information ◽  
Microscopic Simulation ◽  
Highway Capacity ◽  
Highway Capacity Manual ◽  
Urban Streets ◽  
Urban Street ◽  
Incident Duration

The effect of incidents on capacity is the most critical parameter in estimating the influence of incidents on network performance. The Highway Capacity Manual 2010 (HCM 2010) provides estimates of the drop in capacity resulting from incidents as a function of the number of blocked lanes and the total number of lanes in the freeway section. However, there is limited information on the effects of incidents on the capacity of urban streets. This study investigated the effects on capacity of the interaction between the drop in capacity below demand at a midblock urban street segment location and upstream and downstream of signalized intersection operations. A model was developed to estimate the drop in capacity at the incident location as a function of the number of blocked lanes, the distance from the downstream intersection, and the green time–to–cycle length (g:C) ratio of the downstream signal. A second model was developed to estimate the reduction in the upstream intersection capacity resulting from the drop in capacity at the midblock incident location as estimated by the first model. The second model estimated the drop in capacity of the upstream links feeding the incident locations as a function of incident duration time, the volume-to-capacity (V/C) ratio at the incident location, and distance from an upstream signalized intersection. The models were developed on the basis of data generated with the use of a microscopic simulation model calibrated by comparison with parameters suggested in HCM 2010 for incident and no-incident conditions and by comparison with field measurements.

scholarly journals EFFECT OF GALLERIES ON THE WIND FLOW STRUCTURE AND POLLUTANT TRANSPORT WITHIN STREET CANYONS WITH OR WITHOUT FACADE ROUGHNESS ELEMENTS (BALCONIES)

2020 ◽  
Vol 7 (12) ◽  
pp. 45-59
Author(s):  
V. A. Karkoulias ◽  
P. E. Marazioti ◽  
D. P. Georgiou ◽  
E. A. Maraziotis
Keyword(s):  
Flow Field ◽  
Concentration Distribution ◽  
Cfd Simulation ◽  
Field Structure ◽  
Flow Structures ◽  
Street Canyons ◽  
Ansys Fluent ◽  
Roughness Elements ◽  
Computational Fluid Dynamics Cfd ◽  
The Vertical Distribution

This paper investigates how the structure of the flow field and the vertical distribution of the pollutant concentration near the wall facades of street canyons are affected by the presence of some elements such as street level galleries. Numerical results are presented for various gallery geometries in combination with facade roughness elements (balconies) for a canyon of an aspect ratio equal to h/w=2.33. The results were obtained by a Computational Fluid Dynamics (CFD) simulation employing the ANSYS-FLUENT suite that incorporated the k-e turbulent (RNG) model. The simulation generated several flow structures inside the canyon (mainly vortices), whose characteristic properties (e.g. number, strength and size) are discussed in terms of the effect of the galleries on the flow field structure and the roughness generated by the building façade balconies. The results indicate a significant influence on both the flow field structure and the mass concentration distribution of the polluting particles.

scholarly journals Probabilistic Health Risk Assessment of Vehicular Emissions as an Urban Health Indicator in Dhaka City

2019 ◽  
Vol 11 (22) ◽  
pp. 6427
Author(s):  
Asif Iqbal ◽  
Shirina Afroze ◽  
Md. Mizanur Rahman
Keyword(s):  
Health Risk ◽  
Urban Health ◽  
Environmental Planning ◽  
Nox Emissions ◽  
Vehicular Emissions ◽  
Dhaka City ◽  
Health Indicator ◽  
Road Vehicles ◽  
Monte Carlo Simulation Technique ◽  
Emissions Modelling

Emissions modelling is an important tool for assessing the urban health status of any city, but often the assessments are affected by the uncertainty of the data used for the modelling. Therefore, a Monte Carlo simulation technique was used for a probabilistic emissions modelling of Dhaka City by simulating 20,000 scenarios for the highest and lowest values of traffic volume and speed profiles for each of the major road links. Only nitrogen oxide (NOx) emissions from on-road vehicles were considered, as vehicular sources are major contributors. Each dataset included two peak periods and an offpeak period of the day to cover the diurnal variation within each road link. Using the probability of the magnitude of emissions along with the corresponding health risk, a series of spatial urban health risk severity scenarios was generated for 2018 and 2024, suggesting that transportation and environmental planning is required for urban sustainability.

scholarly journals A Numerical Investigation on De-NOx Technology and Abnormal Combustion Control for a Hydrogen Engine with EGR System

Processes ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1178
Author(s):  
Hao Guo ◽  
Song Zhou ◽  
Jiaxuan Zou ◽  
Majed Shreka
Keyword(s):  
Hot Spots ◽  
Three Dimensional ◽  
Pressure Rise ◽  
Nox Emissions ◽  
Combustion Duration ◽  
Rise Rate ◽  
Peak Heat Release Rate ◽  
Combustion Emissions ◽  
Computational Fluid Dynamics Cfd ◽  
Gas Recirculation

The combustion emissions of the hydrogen-fueled engines are very clean, but the problems of abnormal combustion and high NOx emissions limit their applications. Nowadays hydrogen engines use exhaust gas recirculation (EGR) technology to control the intensity of premixed combustion and reduce the NOx emissions. This study aims at improving the abnormal combustion and decreasing the NOx emissions of the hydrogen engine by applying a three-dimensional (3D) computational fluid dynamics (CFD) model of a single-cylinder hydrogen-fueled engine equipped with an EGR system. The results indicated that peak in-cylinder pressure continuously increased with the increase of the ignition advance angle and was closer to the top dead center (TDC). In addition, the mixture was burned violently near the theoretical air–fuel ratio, and the combustion duration was shortened. Moreover, the NOx emissions, the average pressure, and the in-cylinder temperature decreased as the EGR ratio increased. Furthermore, increasing the EGR ratio led to an increase in the combustion duration and a decrease in the peak heat release rate. EGR system could delay the spontaneous combustion reaction of the end-gas and reduce the probability of knocking. The pressure rise rate was controlled and the in-cylinder hot spots were reduced by the EGR system, which could suppress the occurrence of the pre-ignition in the hydrogen engine.

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