Simulation of smoke from a burning vehicle and pollution levels caused by traffic jam in a road tunnel

Detailed analyses of smoke movement from a burning vehicle in a road tunnel have been carried out for the westbound Melbourne City Link tunnel. The time-averaged equations for velocity, pressure, temperature, and mass fraction of emissions were solved for transient condition using the CFD software FLUENT 6.0. For the analysis, a burning bus was assumed to release an equivalent energy of burning 500 l of diesel in 6 min, with vehicles upstream of the fire at a standstill. On the other hand, the vehicles downstream of the fire had enough time to escape from the tunnel through the exit portal. Due to the action of jet fans, most of the smoke was pushed downstream of the fire. The smoke had also dispersed about 55 m upstream of the fire, putting the passengers in this region at great risk. The emissions released from the vehicles in the jam, with their engines running, also posed a threat to human health. Within 8 min after the fire had started, the mass concentrations of O₂, CO₂ and CO were in the ranges of 0.12–0.15, 0.08–0.11 and 0.0006–0.0014, respectively. Therefore, quick evacuation of the passengers is essential in the event of a fire in the tunnel.     

Estimation of automobile emissions and control strategies in India

Rapid, but unplanned urban development and the consequent urban sprawl coupled with economic growth have aggravated auto dependency in India over the last two decades. This has resulted in congestion and pollution in cities. The central and state governments have taken many ameliorative measures to reduce vehicular emissions. However, evolution of scientific methods for emission inventory is crucial. Therefore, an attempt has been made to estimate the emissions (running and start) from on-road vehicles in Chennai using IVE model in this paper. GPS was used to collect driving patterns.The estimated emissions from motor vehicles in Chennai in 2005 were 431, 119, 46, 7, 4575, 29, and 0.41 tons/days respectively for CO, VOC, NO_x, PM, CO_2, CH₄ and N₂O. It is observed from the results that air quality in Chennai has degraded. The estimation revealed that two and three-wheelers emitted about 64% of the total CO emissions and heavy-duty vehicles accounted for more than 60% and 36% of the NO_x and PM emissions respectively. About 19% of total emissions were that of start emissions. It is also estimated that on-road transport contributes about 6637 tons/day CO₂ equivalent in Chennai. This paper has further examined various mitigation options to reduce vehicular emissions. The study has concluded that advanced vehicular technology and augmentation of public transit would have significant impact on reducing vehicular emissions.     

Effect of vehicular technology on energy consumption and emissions

Sustainable development requires inter al the reduction of energy consumption and of traffic-induced pollutant emissions. Hybrid electric vehicles (HEVs) are one of the most promising approaches to decrease emissions. This paper considers the influence of hybridization of transport on energy consumption and emissions on single lanes of road traffic. We have developed a micro-simulation tool which integrates instantaneous consumption and emission models. We have modelled microscopic behaviour of vehicles using a full velocity difference model for longitudinal moving. Then, we have used two macroscopic energy consumption models (COPERT and HBEFA) and an instantaneous energy-consumption model concerning the conventional Internal Combustion Engine (ICE) vehicle to illustrate the relevance of microscopic modelling of energy consumption. Furthermore, we have compared the energy consumption of the HEV Toyota Prius with that of the conventional ICE vehicle. An emission model emissions from traffic (EMIT) was also implemented and extended in order to estimate HEV emissions. The model is used to quantify CO₂ and CO emissions for the HEV Toyota Prius and the conventional ICE vehicle. Moreover, we have studied the influence of fleet hybridization level on energy consumption for congested and uncongested traffic flow state. HEVs can offer major environmental improvements as well as substantial reductions of energy consumption and road traffic emissions. Hybridization is a relevant solution to reduce energy consumption and emissions.     

High resolution modeling of the effects of alternative fuels use on urban air quality: Introduction of natural gas vehicles in Barcelona and Madrid Greater Areas (Spain)

The mitigation of the effects of on-road traffic emissions on urban air pollution is currently an environmental challenge. Air quality modeling has become a powerful tool to design environment-related strategies. A wide range of options is being proposed; such as the introduction of natural gas vehicles (NGV), biofuels or hydrogen vehicles. The impacts on air quality of introducing specific NGV fleets in Barcelona and Madrid (Spain) are assessed by means of the WRF-ARW/HERMES/CMAQ modeling system with high spatial-temporal resolution (1 km², 1 h). Seven emissions scenarios are defined taking into account the year 2004 vehicle fleet composition of the study areas and groups of vehicles susceptible of change under a realistic perspective. O₃ average concentration rises up to 1.3% in Barcelona and up to 2.5% in Madrid when introducing the emissions scenarios, due to the NO_x reduction in VOC-controlled areas. Nevertheless, NO₂, PM10 and SO₂ average concentrations decrease, up to 6.1%, 1.5% and 6.6% in Barcelona and up to 20.6%, 8.7% and 14.9% in Madrid, respectively. Concerning SO₂ and PM10 reductions the most effective single scenario is the introduction of 50% of NGV instead of the oldest commercial vehicles; it also reduces NO₂ concentrations in Barcelona, however in Madrid lower levels are attained when substituting 10% of the private cars. This work introduces the WRF-ARW/HERMES/CMAQ modeling system as a useful management tool and proves that the air quality improvement plans must be designed considering the local characteristics.     

Influence of traffic force on pollutant dispersion of CO,NO and particle matter (PM2.5) measured in an urban tunnel in Changsha,China

Environmental safety issues and ventilation problems caused by the construction of urban tunnel have increasingly been attracting people’s attention. Previous studies in China have mainly focused on vehicle emissions and ventilation control technologies in road tunnels, resulting in a research gap on urban tunnel ventilation engineering design. Therefore, a detailed monitoring investigation was conducted from May 22 to June 2, 2013 in Changsha Yingpan Road Tunnel, China. The study aim was to measure the traffic characteristics, air velocity and the carbon monoxide (CO), nitrogen oxides (NO_x) and fine particulate matter (PM_2.5) concentrations in this tunnel, which has two lanes per bore and multiple ramps. Measurement results show that during the workday morning peak, the maximum traffic flow was 1560 passenger-car-unit/h per lane with vehicle speed around 33.6 km/h in the eastbound tunnel, the average air velocity was 3.07 m/s, and the proportion of the light-duty vehicles (LDV) was 97.3%. Under the traffic force (not open fan), the CO and NO average concentrations at the main tunnel outlet were 20.3 ppm and 1.65 ppm, respectively. The gas pollutant concentrations are effectively controlled within the multiple-ramps tunnel and the design air volume flow is noticeably reduced. The traffic air flow was found to provide 32.5% of the required air volume to dilute NO_x in blocked traffic condition (vehicle speed of 10 km/h). In addition, the PM_2.5 concentration is mainly affected by the value of background outside the tunnel. The result can provide a quantitative assessment method to support pollutant concentration control and contribution of requested air volume by traffic flow in urban complex structure tunnel.     

Traffic-related air pollution modeling during the 2008 Beijing Olympic Games: the effects of an odd-even day traffic restriction scheme

An integrated urban air quality modeling system was applied to assess the effects of a short-term odd-even day traffic restriction scheme (TRS) on traffic-related air pollution in the urban area of Beijing (UAB) before, during and after the 2008 Olympic Games. Using traffic flow data retrieved from an on-line traffic monitoring system, concentration levels of CO, PM₁₀, NO₂ and O₃ on the 2nd, 3rd, 4th Ring Roads (RR) and Linkage Roads (LRs), the main roads distributed around the UAB, were predicted for the pre- (10th-19th, July), during- (20th July-20th September) and post-TRS (21st-30th, September) periods. A widely used statistical framework for model evaluation was adopted, the dependences of model performance on time-of-the-day and on wind direction were investigated, and the model predictions turned out reasonably satisfactory. Results showed that daily average concentrations on the 2nd, 3rd, 4th RR and LRs decreased significantly during the TRS period, by about 35.8, 38.5, 34.9 and 35.6% for CO, about 38.7, 31.8, 44.0 and 34.7% for PM₁₀, about 30.3, 31.9, 32.3 and 33.9% for NO₂, and about 36.7, 33.0, 33.4 and 34.7% for O₃, respectively, compared with the pre-TRS period. Hourly average concentrations were also reduced significantly, particularly for the morning and evening peaks for CO and PM₁₀, for the evening peak for NO₂, and for the afternoon peak for O₃. Consequently, both the daily and hourly concentration level of CO, PM₁₀, NO₂ and O₃ conformed to the China National Ambient Air Quality Standards Grade II during the Games. In addition, notable reduction of concentration levels was achieved in different regions of Beijing, with the traffic-related air pollution in the downwind northern and western areas relieved most significantly. The TRS policy was therefore effective in alleviating traffic-related air pollution and improving short-term air quality in Beijing during the Games.     

A tool for the assessment of the potential benefits of electric and hybrid cars for emissions reduction in urban areas

ABSTRACT

A simulation tool was developed to evaluate variations in exhaust emissions from cars when replacing conventional powertrains with electric or hybrid propulsion systems. The model permits calculation of direct emissions (released at the vehicles’ exhaust) and indirect emissions (released when producing electricity for batteries recharging). To verify model outputs, a reference scenario was defined selecting the urban area of Genoa, Italy, considering the number of vehicles and mileage of eight vehicle categories. A simulated scenario was then designed, replacing cars belonging to older legally defined classes with electric and hybrid ones. Significant reductions were estimated for regulated pollutants, with higher benefits estimated for CO and NO_X emissions, deriving from calculated reductions and contributions of cars in the reference scenario. No advantages were estimated for CO₂, outlining that a change in the national mix for electricity production is also required.     

Performance and emission characteristics of cashew nut shell oil on the CI engine

This article is an effort to address the need for a non-cooking oil-based biodiesel. Here, the experimental work is done on a single cylinder, direct injection CI engine using cashew nut shell oil biodiesel blends under constant speed. The cashew nut shell liquid (CNSL) biodiesel is blended with the diesel fuel and used as biodiesel blend. Blends used for testing are B20, B40 and B60. The effect of the fuels on engine power, brake thermal efficiency (BTE) and exhaust gas temperature was determined by performance tests. The influences of blends on CO, CO₂, HC and NO_x emissions were investigated by emission tests. The BTE values of biodiesel are closer to diesel. Compared to diesel, all the biodiesel blends gave lesser unburnt hydrocarbon (HC), carbon monoxide (CO) and smoke emissions. Slightly higher NO_x emissions were found in CNSL biodiesel blends, which is typical of the other biodiesels.     

Characterization of Emissions from Liquid Fuel and Propane Open Burns

The effect of accidental fires are simulated to understand the response of items such as vehicles, fuel tanks, and military ordnance and to remediate the effects through re-design of the items or changes in operational procedures. The comparative combustion emissions of using jet propellant (JP-5) liquid fuel pools or a propane manifold grid to simulate the effects of accidental fires was investigated. A helium-filled tethered aerostat was used to maneuver an instrument package into the open fire plumes to measure CO, CO₂, fine particulate matter (PM_2.5), polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), and elemental/organic/total carbon (EC/OC/TC). The results showed that all emissions except CO₂ were significantly higher from JP-5 burns than from propane. The major portion of the PM mass from fires of both fuels was less than 1 µm in diameter and differed in carbon content. The PM_2.5 emission factor from JP-5 burns (129 ± 23 g/kg Fuel_c) was approximately 150 times higher than the PM_2.5 emission factor from propane burns (0.89 ± 0.21 g/kg Fuel_c). The PAH emissions as well as some VOCs were more than one hundred times higher for the JP-5 burns than the propane burns. Using the propane test method to study flammability responses, the environmental impact of PM_2.5, PAHs, and VOCs would be reduced by 2300, 700, and 100 times per test, respectively.     

Two smart energy management models for the Spanish electricity system

This paper evaluates two smart energy management models for the Spanish electricity system in terms of power consumption savings, CO₂ emissions, and dependence upon primary energy from abroad. We compare a baseline scenario with two alternatives. The first model entails the reduction of the power demand through energy savings measures, smart meters, and self-supply. The second model entails the application of all measures included in first scenario, plus measures oriented to electric vehicles. For each model a sensitivity analysis was performed. Results show that both models can result in reductions of peak loads, CO₂ emissions, and energy dependence.     

CO2, CO, and Hg emissions from the Truman Shepherd and Ruth Mullins coal fires, eastern Kentucky, USA

Carbon dioxide (CO₂), carbon monoxide (CO), and mercury (Hg) emissions were quantified for two eastern Kentucky coal-seam fires, the Truman Shepherd fire in Floyd County and the Ruth Mullins fire in Perry County. This study is one of the first to estimate gas emissions from coal fires using field measurements at gas vents. The Truman Shepherd fire emissions are nearly 1400 t CO₂/yr and 16 kg Hg/yr resulting from a coal combustion rate of 450-550 t/yr. The sum of CO₂ emissions from seven vents at the Ruth Mullins fire is 726 ± 72 t/yr, suggesting that the fire is consuming about 250-280 t coal/yr. Total Ruth Mullins fire CO and Hg emissions are estimated at 21 ± 1.8 t/yr and > 840 ± 170 g/yr, respectively. The CO₂ emissions are environmentally significant, but low compared to coal-fired power plants; for example, 3.9 × 10⁶ t CO₂/yr for a 514-MW boiler in Kentucky. Using simple calculations, CO₂ and Hg emissions from coal-fires in the U.S. are estimated at 1.4 × 10⁷-2.9 × 10⁸ t/yr and 0.58-11.5 t/yr, respectively. This initial work indicates that coal fires may be an important source of CO₂, CO, Hg and other atmospheric constituents.     

Assessment of gaseous emissions and radiative forcing in Indian forest fires

This paper reports a study of the gaseous emissions from Indian forest fires from 2005 to 2016 and their potential impact on radiative forcing. Initially, forest burned area is quantified using MODIS-MCD45A1 data. Results showed that annual burned area of the study period ranges from 8439 km² to 25,442 km² and the maximum forest area is burned during February, March, and April in any year. Gaseous emissions are estimated using emission factors, the mass of fuel available for combustion, combustion factor, and burned area. CO₂, CO, and CH₄ are the major emissions during forest fires with an annual average of 105 × 10⁶ tonnes, 6 × 10⁶ tonnes, and 3.25 × 10⁵ tonnes, respectively. The average radiative forcing (RF) for CO₂, CH_4, and N₂O is estimated as 1.8 Wm^?2, 0.49 Wm^?2, and 0.177 Wm^?2, respectively. An important finding in the present study is the recurrence of forest fires during the pre-monsoon season.     

Species Transport from Post-Flashover Fires

A study was performed to determine the use of an equivalence ratio to predict gas levels (CO, CO₂, O₂, and unburned hydrocarbons) transported to locations remote from a post-flashover compartment fire. A series of tests were conducted in a reduced-scale facility to measure the evolution of post-flashover compartment fire gases flowing down a hallway. Test variables included air entrainment into gases in the hallway, stoichiometry of the compartment fire gases entering the hallway, mass flow rate of compartment fire gases, and the presence of a vitiated smoke layer accumulated in the hallway. In cases with no layer accumulated in the hallway, species yields in the hallway were found to correlate with a control volume equivalence ratio. The control volume equivalence ratio is the ratio of the mass loss rate of fuel inside the compartment to the air flow into the compartment plus the air entrained into compartment fire gases flowing along the hallway. Layers that accumulate in the hallway were determined to limit oxidation, which in some cases resulted in CO yields transported to remote locations being 20% higher than those inside the compartment. Based on the experimental data, a methodology was developed for predicting species levels transported to remote locations.     

Performance,emission and combustion characteristics of a single cylinder spark ignition engine using ethanol–petrol-blended fuels

The performance, exhaust emission and combustion analyses of a single cylinder spark ignition engine fuelled with extended range of ethanol–petrol blends were carried out successfully at full load conditions. Ethanol produced from raffia trunks was blended with petrol at different proportions by volume. In order to establish a baseline for comparison, the engine was first run on neat petrol. The engine performance parameters (engine torque, brake power, brake specific fuel consumption, brake mean effective pressure and brake thermal efficiency), exhaust emission parameters (CO, HC, CO₂ and O₂ emissions) and combustion parameters were determined for each blend of fuel at different engine speeds. The test results interestingly revealed that the addition of ethanol to petrol causes an improvement in combustion characteristics and significant reduction in exhaust emissions which in turn improved engine performance. In all, ethanol and its blends with petrol exhibited performance characteristics trends similar to that of petrol thus confirming them as suitable alternative fuels for spark ignition engines.     

Gaseous elemental mercury emissions and CO2 respiration rates in terrestrial soils under controlled aerobic and anaerobic laboratory conditions

Mercury (Hg) levels in terrestrial soils are linked to the presence of organic carbon (C). Carbon pools are highly dynamic and subject to mineralization processes, but little is known about the fate of Hg during decomposition. This study evaluated relationships between gaseous Hg emissions from soils and carbon dioxide (CO₂) respiration under controlled laboratory conditions to assess potential losses of Hg to the atmosphere during C mineralization. Results showed a linear correlation (r² = 0.49) between Hg and CO₂ emissions in 41 soil samples, an effect unlikely to be caused by temperature, radiation, different Hg contents, or soil moisture. Stoichiometric comparisons of Hg/C ratios of emissions and underlying soil substrates suggest that 3% of soil Hg was subject to evasion. Even minute emissions of Hg upon mineralization, however, may be important on a global scale given the large Hg pools sequestered in terrestrial soils and C stocks.We induced changes in CO₂ respiration rates and observed Hg flux responses, including inducement of anaerobic conditions by changing chamber air supply from N₂/O₂ (80% and 20%, respectively) to pure N₂. Unexpectedly, Hg emissions almost quadrupled after O₂ deprivation while oxidative mineralization (i.e., CO₂ emissions) was greatly reduced. This Hg flux response to anaerobic conditions was lacking when repeated with sterilized soils, possibly due to involvement of microbial reduction of Hg²⁺ by anaerobes or indirect abiotic effects such as alterations in soil redox conditions. This study provides experimental evidence that Hg volatilization, and possibly Hg²⁺ reduction, is related to O₂ availability in soils from two Sierra Nevada forests. If this result is confirmed in soils from other areas, the implication is that Hg volatilization from terrestrial soils is partially controlled by soil aeration and that low soil O₂ levels and possibly low soil redox potentials lead to increased Hg volatilization from soils.     

Experimental investigation on regulated and unregulated emissions of a diesel/methanol compound combustion engine with and without diesel oxidation catalyst

The use of methanol in combination with diesel fuel is an effective measure to reduce particulate matter (PM) and nitrogen oxides (NOx) emissions from in-use diesel vehicles. In this study, a diesel/methanol compound combustion (DMCC) scheme was proposed and a 4-cylinder naturally-aspirated direct-injection diesel engine modified to operate on the proposed combustion scheme. The effect of DMCC and diesel oxidation catalyst (DOC) on the regulated emissions of total hydrocarbons (THC), carbon monoxide (CO), NOx and PM was investigated based on the Japanese 13 Mode test cycle. Certain unregulated emissions, including methane, ethyne, ethene, 1,3-butadiene, BTX (benzene, toluene, xylene), unburned methanol and formaldehyde were also evaluated based on the same test cycle. In addition, the soluble organic fraction (SOF) in the particulate and the particulate number concentration and size distribution were investigated at certain selected modes of operation. The results show that the DMCC scheme can effectively reduce NOx, particulate mass and number concentrations, ethyne, ethene and 1,3-butadiene emissions but significantly increase the emissions of THC, CO, NO₂, BTX, unburned methanol, formaldehyde, and the proportion of SOF in the particles. After the DOC, the emission of THC, CO, NO₂, as well as the unregulated gaseous emissions, can be significantly reduced when the exhaust gas temperature is sufficiently high while the particulate mass concentration is further reduced due to oxidation of the SOF.     

Determinants of ultrafine particles,black carbon,nitrogen dioxide,and carbon monoxide concentrations inside vehicles in the Paris area: PUF-TAXI study

This study presents real-time concentrations of traffic-related air pollutants during 499 trips conducted by 50 Parisian taxi drivers from PUF-TAXI project. Ultrafine particles (UFP), black carbon (BC), and nitrogen dioxide (NO₂)/carbon monoxide (CO) were measured inside vehicles by Diffusion Size Classifier Miniature^®, microAeth^®, and Gas-Pro^®, respectively, for nine hours. Vehicle/trip data characteristics were collected by questionnaires and on ambient conditions by monitoring stations. The associations between pollutant levels and their potential determinants were analyzed using generalized estimating equation model. Determinants of in-vehicle pollutants levels were identified: (1) ambient factors (meteorology and ambient pollution)—affecting BC, NO_2, and CO; (2) vehicle characteristics—affecting all pollutants; and (3) trip-related driving habits—affecting UFP, BC, and CO. We highlight that commuters can, therefore, avoid high in-vehicle air pollutant concentrations mainly by (1) closing windows and activating air-conditioning under air recirculation mode in congested traffic; (2) smooth driving; and (3) maintaining cabin air filters.     

Embodied and operational carbon dioxide emissions from housing: A case study on the effects of thermal mass and climate change

A 100-year lifecycle carbon dioxide (CO₂) emissions analysis is reported for a two-bedroom, 65 m² floor area, semi-detached house in south-east England. How the balance between the embodied (ECO₂) and operational CO₂ emissions of the building are affected by the inclusion of thermal mass and the impacts of climate change is quantified. Four ‘weights’ of thermal mass were considered, ranging from lightweight timber frame to very heavyweight concrete construction. For each case, total ECO₂ quantities were calculated and predictions for operational CO₂ emissions obtained from a 100-year dynamic thermal modelling simulation under a medium-high emissions climate change scenario for south-east England. At the start of the lifecycle, the dwellings were passively cooled in summer, but air conditioning was installed when overheating reached a certain threshold. The inclusion of thermal mass delayed the year in the lifecycle when this occurred, due to the better passive control of summertime overheating. Operational heating and cooling energy needs were also found to decrease with increasing thermal mass due to the beneficial effects of fabric energy storage. The calculated initial ECO₂ was higher in the heavier weight cases, by up to 15% (4.93 t) of the lightweight case value, but these difference were offset early in the lifecycle due to the savings in operational CO₂ emissions, with total savings of up to 17% (35.7 t) in lifecycle CO₂ found for the heaviest weight case.     

Effects of urban form on air quality in China: An analysis based on the spatial autoregressive model

Understanding how urban air quality depends on urban form can have important implications for improving urban air quality by optimizing urban planning and management policies. This study employed the spatial autoregressive model to explore the effect of urban form on urban air quality in 288 prefecture-level cities in China. Information on the air quality (AQI) and six criteria pollutants (PM_2.5, PM₁₀, CO, SO₂, NO₂, O₃) were obtained from the hourly observation data of 1333 in-situ air monitoring stations throughout 2015. Urban form is characterized by five metrics, including urban size, shape, sprawl, fragmentation and traffic accessibility, and it is calculated based on land cover data. Results show that urban shape complexity and population density have a significant negative impact on urban air quality. Large city size is strongly related to comparatively poor air quality for cities in Southern China and only shows a slight association with emissions in Northern China. In general, lower-sized, scattered, polycentric cities provide better air quality in China. It is suggested that higher air quality and fewer pollutant emissions can be achieved through urban form planning and management policies, which aim to restrict the blind expansion of urban land and encourage moderately scattered, polycentric urban development.     

Application of field model and two-zone model to flashover fires in a full-scale multi-room single level building

This paper presents a comparison of the results from a computational fluid dynamics (CFD) model and a two-zone model against a comprehensive set of data obtained from one flashover fire experiment. The experimental results were obtained from a full-scale prototype apartment building under flashover conditions. Three polyurethane mattresses were used as fuel. The CFAST two-zone model (version 2.0) was also used to predict results for this flashover fire test. The mass release rate, gas temperature, radiation heat flux and gas compositions (O₂, CO₂ and CO) were measured. A CFD program, CESARE-CFD Fire Model, has been developed and was used also to predict results for polyurethane-slab fire. A simple flame spread model was incorporated into the CFD program to predict the mass release rate and heat release rate during the fire instead of providing it as an input as is required for most zone and CFD models. It was found that the CFD model provided reasonable predictions of the magnitude and the trends for the temperatures in the burn room and the species concentrations, but over-predicted the temperatures in the adjacent enclosures. From a life safety perspective, the CFD model conservatively predicted the concentrations of CO and CO₂. The predicted temperatures from the CFAST fire model agreed well with the experimental results in most areas. However, the CFAST model under predicted the temperature in the lower layer of the room of fire origin and the concentration of CO in most areas.