Browsing by Subject "Emissions"
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Item A microsimulation analysis of highway intersections near highway-railroad grade crossings(Texas A&M University, 2004-11-15) Tydlacka, Jonathan MichaelThe purpose of this thesis was to perform microsimulation analyses on intersections near Highway-Railroad Grade Crossings (HRGCs) to determine if controlling mean train speed and train speed variability would improve safety and reduce delays. This research focused on three specific areas. First, average vehicle delay was examined, and this delay was compared for seven specific train speed distributions, including existing conditions. Furthermore, each distribution was associated with train detectors that were placed at the distance the fastest train could travel during the given warning time. Second, pedestrian cutoffs were investigated. These cutoffs represented an occasion when the pedestrian phases were truncated or shortened due to railroad signal preemption. Finally, vehicle emissions were analyzed using a modal emissions model. A microscopic simulation model of the Wellborn Corridor in College Station, Texas was created using VISSIM. The model was run twenty times in each train speed distribution for each of three train lengths. Average vehicle delay was collected for three intersections, and delays were compared using the Pooled t-test with a 95% confidence interval. Comparisons were made between the distributions, and generally, distributions with higher mean train speeds were associated with lower average delay, and train length was not a significant factor. Unfortunately, pedestrian cutoffs were not specifically controlled in this project; therefore, no statistical conclusions can be made with respect to the pedestrian cutoff problem. However, example cases were devised to demonstrate how these cutoffs could be avoided. In addition, vehicle emissions were examined using the vehicle data from VISSIM as inputs for CMEM (Comprehensive Modal Emissions Model). For individual vehicles, as power (defined as the product of velocity and acceleration) increased, emissions increased. When comparing emissions from different train speed distributions, few significant differences were found. However, a scenario with no train was tested, and it was shown to have significantly higher emissions than three of the distributions with trains. Ultimately, this thesis shows that average vehicle delay and vehicle emissions could be lowered by specific train speed distributions. Also, work could be done to investigate the pedestrian cutoff problem.Item An Optimization Model for Eco-Driving at Signalized Intersection(2013-07-15) Chen, ZhiThis research develops an optimization model for eco-driving at signalized intersection. In urban areas, signalized intersections are the ?hot spots? of air emissions and have significant negative environmental and health impacts. Eco-driving is a strategy which aims to reduce exclusive fuel consumption and emissions by modifying or optimizing drivers? behaviors. With the help of vehicle-to-vehicle (V2V) communication and vehicle-to-infrastructure communication (V2I), eco-driving could utilize the signal phase and the queue-discharging time information to optimize the speed trajectories for the vehicles approaching an intersection in order to reduce fuel consumption and emissions. A few research studies have been conducted on the development of algorithms that utilize traffic signal information to reduce fuel consumption and emissions. Hence, the goal of this research is to develop an optimization model to determine the optimal eco-driving trajectory (the speed profile) at a signalized intersection, which aims to achieve the minimization of a linear combination of emissions and travel time. Then enumeration method, simplex optimization and genetic algorithm are investigated to determine a practicable and efficient method to solve the proposed optimization problem. As various scenarios of distance from the vehicle to the intersection, queue discharging time and weights of emission/travel time will lead to different optimal trajectories and different emissions and travel times. A sensitivity study is conducted to analyze and compare the performance of the optimal solution in various scenarios of different such parameters. In addition, a baseline study is conducted to investigate the benefits of eco-driving when drivers only decelerate in advance but not apply the recommended speed trajectory. The results of case study show that genetic algorithm is a preferred method to solve the proposed optimization problem; Eco-driving could achieve satisfied reduction in emissions without significantly increasing travel time and emissions is more sensitive to various scenarios than travel time; Eco-driving still could achieve reduction in emissions as long as the drivers decelerate earlier even though the they would not apply the recommended speed trajectory under certain conditions.Item Analysis of a novel thermoelectric generator in the built environment(2011-08) Lozano, Adolfo; Webber, Michael E., 1971-; Schmidt, Philip S.This study centered on a novel thermoelectric generator (TEG) integrated into the built environment. Designed by Watts Thermoelectric LLC, the TEG is essentially a novel assembly of thermoelectric modules whose required temperature differential is supplied by hot and cold streams of water flowing through the TEG. Per its recommended operating conditions, the TEG nominally generates 83 Watts of electrical power. In its default configuration in the built environment, solar-thermal energy serves as the TEG’s hot stream source and geothermal energy serves as its cold stream source. Two systems-level, thermodynamic analyses were performed, which were based on the TEG’s upcoming characterization testing, scheduled to occur later in 2011 in Detroit, Michigan. The first analysis considered the TEG coupled with a solar collector system. A numerical model of the coupled system was constructed in order to estimate the system’s annual energetic performance. It was determined numerically that over the course of a sample year, the solar collector system could deliver 39.73 megawatt-hours (MWh) of thermal energy to the TEG. The TEG converted that thermal energy into a net of 266.5 kilowatt-hours of electricity in that year. The second analysis focused on the TEG itself during operation with the purpose of providing a preliminary thermodynamic characterization of the TEG. Using experimental data, this analysis found the TEG’s operating efficiency to be 1.72%. Next, the annual emissions that would be avoided by implementing the zero-emission TEG were considered. The emission factor of Michigan’s electric grid, RFCM, was calculated to be 0.830 tons of carbon dioxide-equivalent (CO2e) per MWh, and with the TEG’s annual energy output, it was concluded that 0.221 tons CO2e would be avoided each year with the TEG. It is important to note that the TEG can be linearly scaled up by including additional modules. Thus, these benefits can be multiplied through the incorporation of more TEG units. Finally, the levelized cost of electricity (LCOE) of the TEG integrated into the built environment with the solar-thermal hot source and passive ground-based cold source was considered. The LCOE of the system was estimated to be approximately $8,404/MWh, which is substantially greater than current generation technologies. Note that this calculation was based on one particular configuration with a particular and narrow set of assumptions, and is not intended to be a general conclusion about TEG systems overall. It was concluded that while solar-thermal energy systems can sustain the TEG, they are capital-intensive and therefore not economically suitable for the TEG given the assumptions of this analysis. In the end, because of the large costs associated with the solar-thermal system, waste heat recovery is proposed as a potentially more cost-effective provider of the TEG’s hot stream source.Item Comparison of emissions and energy consumptions between a conventional diesel school bus and a plug-in hybrid school bus, emphasizes on recharging(2010-05) Florette, Claire Anne; Matthews, Ronald D.Quantifying the emissions due to the charging of the batteries of the plug-in hybrid electricity school bus operated by the Austin Independent School District (AISD) is the focus of this work. This plug-in hybrid school bus is one of only nineteen in the country, and was manufactured by IC Corporation. This hybrid school bus reduces fuel consumption and CO₂, NOx and PM emissions in comparison with conventional diesel buses. This reduction is good for the health of the children who take the school bus everyday as they are part of the population the most at risk because their lungs are still developing. In order to evaluate CO₂, NOx and PM emissions, measurements of the charging of the batteries versus time were taken for the two charging periods each day during the months of April and May 2009. These measurements were repeated in October 2009 when the route was changed for the new school year: 2009-2010. An analysis of the Austin electricity mix that provides electricity to the bus center was done hour by hour to evaluate the emissions, calculated on a g/mile basis. Measurements of the vehicle speed versus time and altitude were taken during February 2010 in order to explain some of the differences observed between the two routes. Different parameters were studied to analyze the results. The first parameter studied was the impact of the season on the emissions. The second parameter studied was the impact of the route and its characteristics (road length, traffic, grade, etc.). The last parameter studied was the difference between two methods used to evaluate the emissions using the electricity mix data. These two methods are different but each of them brings something to the analysis of the results.Item Comprehensive assessment of fine particulate matter emissions inventories and development of improved allocation profiles(2006-12) Simon, Heather Aliza, 1979-; Allen, David T.Emission inventories of fine particulate matter (PM) were compared to estimates of emissions based on observational data emerging from the EPA Particulate Matter Supersites and other field programs. Six source categories for fine PM emissions were considered: on-road mobile sources, non-road mobile sources, cooking, biomass combustion, fugitive dust and stationary sources. Regional emission inventories of PM in the exhaust from on-road and non-road sources were generally consistent with ambient observations. In contrast, emission inventories of road dust were an order of magnitude larger than ambient observations, and estimated brake wear and tire dust emissions were half as large as ambient observations in urban areas. Although a comprehensive nationwide emission inventory of fine PM from cooking sources and biomass burning is not yet available, observational data in urban areas suggest that cooking sources account for roughly 5-20% of total primary emissions (excluding dust) and the magnitude of biomass burning emissions are highly dependent on the region. Finally, relatively few observational data were available to assess the accuracy of emission estimates for stationary sources. Overall, the uncertainties in primary emissions for fine PM are substantial. Because of these uncertainties, the design of fine PM control strategies should be based on inventories that have been refined by a combination of bottom-up and top-down methods, as demonstrated in this work. This approach was used in the development of a primary PM emissions inventory for air quality modeling. This emissions inventory improved upon previous inventories by updating some source strengths, temporal allocations, and chemical speciation profiles; in addition, size resolution information was incorporated into the inventory.Item Dynamic traffic assignment-based modeling paradigms for sustainable transportation planning and urban development(2014-05) Shah, Rohan Jayesh; Boyles, Stephen David, 1982-Transportation planning and urban development in the United States have synchronously emerged over the past few decades to encompass goals associated with sustainability, improved connectivity, complete streets and mitigation of environmental impacts. These goals have evolved in tandem with some of the relatively more traditional objectives of supply-side improvements such as infrastructure and capacity expansion. Apart from the numerous federal regulations in the US transportation sector that reassert sustainability motivations, metropolitan planning organizations and civic societies face similar concerns in their decision-making and policy implementation. However, overall transportation planning to incorporate these wide-ranging objectives requires characterization of large-scale transportation systems and traffic flow through them, which is dynamic in nature, computationally intense and a non-trivial problem. Thus, these contemporary questions lie at the interface of transportation planning, urban development and sustainability planning. They have the potential of being effectively addressed through state-of-the-art transportation modeling tools, which is the main motivation and philosophy of this thesis. From the research standpoint, some of these issues have been addressed in the past typically from the urban design, built-environment, public health and vehicle technology and mostly qualitative perspectives, but not as much from the traffic engineering and transportation systems perspective---a gap in literature which the thesis aims to fill. Specifically, it makes use of simulation-based dynamic traffic assignment (DTA) to develop modeling paradigms and integrated frameworks to seamlessly incorporate these in the transportation planning process. In addition to just incorporating them in the planning process, DTA-based paradigms are able to accommodate numerous spatial and temporal dynamics associated with system traffic, which more traditional static models are not able to. Besides, these features are critical in the context of the planning questions of this study. Specifically, systemic impacts of suburban and urban street pattern developments typically found in US cities in past decades of the 20th century have been investigated. While street connectivity and design evolution is mostly regulated through local codes and subdivision ordinances, its impacts on traffic and system congestion requires modeling and quantitative evidence which are explored in this thesis. On the environmental impact mitigation side, regional emission inventories from the traffic sector have also been quantified. Novel modeling approaches for the street connectivity-accessibility problem are proposed. An integrated framework using the Environmental Protection Agency's regulatory MOVES model has been developed, combining it with mesoscopic-level DTA simulation. Model demonstrations and applications on real and large-sized study areas reveal that different levels of connectivity and accessibility have substantial impacts on system-wide traffic---as connectivity levels reduce, traffic and congestion metrics show a gradually increasing trend. As regards emissions, incorporation of dynamic features leads to more realistic emissions inventory generation compared to default databases and modules, owing to consideration of the added dynamic features of system traffic and region-specific conditions. Inter-dependencies among these sustainability planning questions through the common linkage of traffic dynamics are also highlighted. In summary, the modeling frameworks, analyses and findings in the thesis contribute to some ongoing debates in planning studies and practice regarding ideal urban designs, provisions of sustainability and complete streets. Furthermore, the integrated emissions modeling framework, in addition to sustainability-related contributions, provides important tools to aid MPOs and state agencies in preparation of state implementation plans for demonstrating conformity to national ambient air-quality standards in their regions and counties. This is a critical condition for them to receive federal transportation funding.Item Effect of relative humidity on chemical off-gassing in residences(2011-05) Nnadili, Miriam Nchekwubechukwn; Corsi, Richard L.; Kinney, Kerry A.Relative humidity (RH) is an important parameter associated with occupant comfort in buildings. However, the effects of RH on indoor source off-gassing and interactions between air pollutants and indoor materials are poorly understood. For this study, air samples were collected in residential buildings to characterize “background” concentrations of volatile organic compounds (VOCs) in air. The interior space was then humidified for several hours prior to collection of another air sample to characterize the effects of increased RH on VOC concentrations. Samples were analyzed by GC/FID with abundance “binning” by elution time. Some samples were also analyzed using GC/MS to identify specific VOCs. Results indicate that increasing RH is associated with increases in VOC concentrations in residential indoor air. Many of the chemicals that show enhanced off-gassing are associated with architectural coating, moth repellents, and cleaning agents. The results of this study are novel and may have implications with respect to health effects associated with damp buildings and increased respiratory effects of children during sleep in bedrooms with elevated RH.Item Energy and environmental contexts of cities, transportation systems, and emerging vehicle technologies : how plug-in electric vehicles and urban design influence energy consumption and emissions(2013-12) Nichols, Brice G.; Kockelman, KaraThis thesis is divided into two parts. The first evaluates the role of the built environment in life-cycle energy consumption, by comparing different neighborhood and city styles. Through a holistic modeling and accounting framework, this work identifies the largest energy-consuming sectors, among residential and commercial buildings, personal vehicles and transit trips, and supporting infrastructure (roads, sidewalks, parking lots, water pipes, street lighting). Life-cycle energy calculations include operational energy use (e.g., gasoline for vehicles, electricity and natural gas for buildings) and embodied energy used to produce materials and construct buildings and infrastructure. Case study neighborhoods in Austin, Texas, and larger-scale regional models suggest that building energy demands comprise around 50% of life-cycle energy demands, while transportation demands (from driving and infrastructure alike) contribute around 40%, across all cases. However, results also suggest that population density and average residential unit size play a major role in defining per-capita energy consumption. Operational demands made up about 90% of life-cycle energy demands, suggesting that v most urban energy savings can be obtained from reduced personal vehicle trips and more efficient vehicles and buildings. Case study comparisons suggest that neighborhoods and regions with greater density and higher share of multi-family housing units tend to reduce operational (and thus life-cycle) energy demands with less travel demand and decreased home and work energy use, per capita. The second part of this modeled plug-in electric vehicle (PEV) emissions impacts in Texas, by considering four possible vehicle adoption scenarios (where PEVs make up 1, 5, 10, and 25% of total passenger vehicles). The analysis anticipates PEV electricity demand and emissions rates, based on current Texas power grid data. Results indicate that PEV emissions depend significantly on which specific power plants are used to power the vehicles, but that PEVs' average per-mile emissions rates for NO[subscript x], PM, and CO₂ are all likely to be lower than today's average passenger car, when today's average mix is used. Power produced from 100% coal plants could produce 14 times as much NO[subscript x], 3,200 times as much SO₂, nearly 10 times as much CO₂ and CO₂eq, 2.5 times as much PM₁₀, and VOCs, and nearly 80 times the NO₂ compared to a grid with 100% natural gas plants.Item Engineering analysis of the air pollution regulatory process impacts on the agricultural industry(Texas A&M University, 2008-10-10) Lange, Jennifer MarieThe EPA press release dated February 23, 2004 states that the three Buckeye Egg Farm facilities had the potential to emit more than a combined total of 1850 tons per year of particulate matter (PM). This number was based on flowrate calculations that were three times higher than those measured as well as a failure to include particle size distributions in the emissions calculations. The annual PM emission for each facility was approximately 35 tons per year. The EPA was unjustified in requiring Buckeye Egg Farm to obtain Title V and PSD permits as the facilities could not have met the thresholds for these permits. Engineers need to be concerned with correctly measuring and calculating emission rates in order to enforce the current regulations. Consistency among regulators and regulations includes using the correct emission factors for regulatory permitting purposes. EPA has adopted AERMOD as the preferred dispersion model for regulatory use on the premise that it more accurately models the dispersion of pollutants near the surface of the Earth than ISCST3; therefore, it is inappropriate to use the same emission factor in both ISCST3 and AERMOD in an effort to equitably regulate PM sources. For cattle feedlots in Texas, the ISCST3 emission factor is 7 kg/1000 hd-day (16 lb/1000 hd-day) while the AERMOD emission factor is 5 kg/1000 hd-day (11 lb/1000 he-day). The EPA is considering implementing a crustal exclusion for the PM emitted by agricultural sources. Over the next five years, it will be critical to determine a definition of crustal particulate matter that researchers and regulators can agree upon. It will also be necessary to develop a standard procedure to determine the crustal mass fraction of particulate matter downwind from a source to use in the regulatory process. It is important to develop a procedure to determine the particulate matter mass fraction of crustal downwind from a source before the crustal exclusion can be implemented to ensure that the exclusion is being used correctly and consistently among all regulators. According to my findings, the mass fraction of crustal from cattle feedlot PM emissions in the Texas High Plains region is 52%.Item Estimating emissions impacts to the bulk power system of increased electric vehicle and renewable energy usage(2013-12) Meehan, Colin Markey; Webber, Michael E., 1971-; Baldick, RossThe research presented in this thesis examines the use of electric vehicles and renewable energy to reduce emissions of CO₂, SO₂ and NO[subscript x], and within the state of Texas. The analysis examines the impact of increased renewable energy output and electric vehicle charging on the emissions of fossil fuel electric generators used to serve the bulk power system within Texas. The analysis then compares those impacts to alternative scenarios in which fossil fuel generation replaces some renewable energy generation, and Internal Combustion Engine (ICE) vehicles of varying efficiency are used instead of electric vehicles. This research uses temporally-resolved regression analysis combined with a unit commitment and dispatch model that incorporates several different scenarios for EV charging and fuel mixes to evaluate emissions outcomes based on a variety of conditions. Hourly historical generation and emission data for each fossil fuel generator, combined with hourly output data for non-fossil fuel units aggregated by fuel type (i.e. nuclear, wind, hydro-electric) within the Electric Reliability Council of Texas (ERCOT) footprint is regressed to assess the impact of wind generation output on fossil-fuel generation emissions. The regression analysis is used to assess potential increases in emissions resulting from the ramping of fossil-fuel Electric Generation Units (EGUs) to compensate for variability in wind generation output due to changing weather conditions. The unit commitment dispatch model is used to evaluate the impact of changes in customer demand due to increased usage and charging of electric vehicles on the ERCOT system and any resulting increase in emissions from generation used to meet this new demand. The model uses detailed cost, performance and emissions data for EGUs in the ERCOT footprint to simulate the impact of a variety of charging scenarios and fuel mixes on EGU dispatch patterns and any resulting change in system-wide emissions. The results of this model are combined with the results of the regression analysis to present a more complete analysis of the combined impacts of increase EV and renewable energy usage on the emissions of CO₂, SO₂ and NO[subscript x] within the ERCOT footprint. Based on these analyses the increases in renewable energy generation demonstrate clear benefits in terms of emission reductions when the impacts of increased emissions due to more frequent ramping of fossil-fuel units are taken into account. This analysis also finds that EV charging generally has emissions benefits across a range of charging patterns and bulk power system fuel mixes, although in certain circumstances EV charging might result in higher emissions than the use of ICE vehicles. This research finds when future ICE vehicles with reduced emissions are taken into account, approximately half of the modeled scenarios show net emissions benefits from EV charging, while half show net emissions costs when emissions impacts across pollutants are taken into account.Item Impact of variable emissions on ozone formation in the Houston area(2009-12) Pavlovic, Radovan Thomas, 1971-; Allen, David T.; McDonald-Buller, ElenaGround level ozone is one of the most ubiquitous air pollutants in urban areas, and is generated by photochemical reactions of oxides of nitrogen (NOx) and volatile organic compounds (VOCs). The effectiveness of emission reduction strategies for ozone precursors is typically evaluated using gridded, photochemical air quality models. One of the underlying assumptions in these models is that industrial emissions are nearly constant, since many industrial facilities operate continuously at a constant rate of output. However, recent studies performed in the Houston-Galveston-Brazoria area indicate that some industrial emission sources exhibit high temporal emission variability that can lead to very rapid ozone formation, especially when emissions are composed of highly reactive volatile organic compounds. This work evaluates the impact of variable emissions from industrial sources on ground-level ozone formation in Houston area, utilizing a unique hourly emission inventory, known as the 2006 Special Inventory, created as a part of the second Texas Air Quality Study. Comparison of the hourly emissions inventory data with ambient measurements indicated that the impact of the variability of industrial source emissions on ozone can be significant. Photochemical modeling predictions showed that the variability in industrial emissions can lead to differences in local ozone concentrations of as much as 27 ppb at individual ozone monitor locations. The hourly emissions inventory revealed that industrial source emissions are highly variable in nature with diverse temporal patterns and stochastic behavior. Petrochemical and chemical manufacturing flares, which represent the majority of emissions in the 2006 Special Inventory, were grouped into categories based on industrial process, chemical composition of the flared gas, and the temporal patterns of their emissions. Stochastic models were developed for each categorization of flare emissions with the goal of simulating the characterized temporal emission variability. The stochastic models provide representative temporal profiles for flares in the petrochemical manufacturing and chemical manufacturing sectors, and as such serve as more comprehensive input for photochemical air quality modeling.Item Indoor air quality in retail stores(2011-05) Rhodes, Joshua Daniel; Siegel, Jeffrey A.; Xu, YingRetail stores are understudied given the energy, occupant health, and potential sales impacts associated with poor indoor air quality (IAQ). There is also evidence of elevated pollutants in retail environments. This thesis is an exploration of the indoor air quality of retail stores. The first section of this thesis is a literature review on field investigations of the indoor air quality in retail buildings. Sixteen investigations report different measurements in 17 specific types of retail environments. Measurements vary depending on the specific investigation, but include VOCs, SVOCs, particles, microbiological species, and radon. When reported, indoor to outdoor ratios of almost all pollutants are greater than unity, suggesting the importance of indoor sources in retail environments. The second section of this thesis is an analysis of the whole store net emission factor for different retail environments. From the types of pollutants found in the retail store investigations, VOCs were the only pollutant group studied frequently enough to merit this analysis. The final section is an analysis of the potential for pollutant remediation strategies. Two methods, increasing air change rate and air cleaning, are considered with an analysis of the energy penalties associated with each.Item Investigation of acoustically forced non-premixed jet flames in crossflow(2011-05) Marr, Kevin Chek-Shing; Clemens, Noel T.; Ezekoye, Ofodike A.; Hall, Matthew J.; Raman, Venkat; Varghese, Philip L.The work presented here discusses the effects of strong acoustic forcing on jet flames in crossflow (JFICF) and the physical mechanisms behind theses effects. For forced non-premixed JFICF, the jet fuel flow is modulated using an acoustic speaker system, which results in a drastic decrease in flame length and soot luminosity. Forced JFICF are characterized by periodic ejections of high-momentum, deeply penetrating vortical structures, which draws air into the jet nozzle and enhances mixing in the nearfield region of the jet. Mixture fraction images of the non-reacting forced jet in crossflow are obtained from acetone planar laser-induced fluorescence and show that the ejected jet fluid is effectively partially premixed. Flame luminosity images and exhaust gas measurements show that forced non-premixed JFICF exhibit similar characteristics to unforced partially-premixed JFICF. Both strong forcing and air dilution result in net reductions in NOx, but increases in CO and unburned hydrocarbons. NOx scaling analysis is presented for both forced non-premixed and unforced partially-premixed flames. Using flame volume arguments, EINOx scales with amplitude ratio for forced non- premixed flames, but does not scale with air dilution for unforced partially-premixed flames. The difference in scaling behavior is attributed to differences in flame structure. The effect of forcing on the flowfield dynamics of non-premixed JFICF is investigated using high-speed stereoscopic particle image velocimetry and luminosity imaging. The frequency spectra of the windward and lee-side flame base motions obtained from luminosity movies of the forced JFICF show a peak at the forcing frequency in the lee-side spectrum, but not on the windward-side spectrum. The lee-side flame base responds to the forcing frequency because the lee-side flame base stabilizes closer to the jet exit. The windward-side flame base does not respond to the forcing frequency because the integrated effect of the incident crossflow and vortical ejections leads to extinction of the flame base. From the PIV measurements, flowfield statistics are conditioned at the flame base. The local gas velocity at the flame base did not collapse for forced and unforced JFICF and was found to exceed 3SL. The flame propagation velocity was determined from the motion of the flame base, which is inferred from regions of evaporated seed particles in the time-resolved PIV images. The flame propagation velocity collapses for forced and unforced JFICF, which implies that the flame base is an edge flame; however, the most probable propagation velocity, approximately 2-3SL, is larger than propagation velocity predicted by edge flame theories. A possible explanation is that the flame propagation is enhanced by turbulent intensities and flame curvature.Item The metallic elephant in the room : short range flights, high-speed rail, and the environment(2011-05) Johnson, Donovan Theodore; Zhang, Ming, 1963 Apr. 22-; Loftus-Otway, Lisa D.It is of nearly universal acceptance that one of the pillars of American economic success over the course of the 20th century was the rapid development of infrastructure. Transportation infrastructure has been of particular importance in the rise of the United States and attributed to the spread of an increasingly mobile culture. Americans undoubtedly enjoy traveling, and the ability to do so with relative ease is of immense value to many. In Texas, the majority of economic activity takes place within what is colloquially known as the “Texas Triangle”, an area bounded by the large metropolitan areas of Houston, Dallas-Ft. Worth, and San Antonio. Intensive population growth in Texas, anchored by the triangle, has led to increasing road congestion on many routes, especially along Interstates 35 and 10. This congestion, and the wasted time and money that comes with it, are of increasing concern to the future economic vitality of the state. The Texas Triangle is also served by extensive aviation links via major airports in the major metropolitan areas, as well as smaller airports in other parts of the region. These flights, operated by American Airlines, Continental Airlines, and Southwest Airlines are frequent, but emit large amounts of greenhouse gases that contribute to ground level pollution and possibly climate change. High-speed rail has been considered by many to be a superior environmental option for intercity routes with lengths inherent to the Texas Triangle. However, given the fact that Texas is the top emitter of carbon dioxide in the U.S. and relies on an energy mix that is primarily fossil fuel powered; would a potential high-speed rail in Texas outperform the current air system environmentally, given similar passenger miles traveled? This report examines the environmental emissions of high-speed rail and compares it to the environmental emissions of our current aviation system, taking into account a life-cycle perspective.Item Minimizing vehicle emissions through transportation road network design incorporating demand uncertainty(2010-05) Ferguson, Erin Molly; Waller, S. Travis; Machemehl, Randy B.Traditionally, transportation road networks have been designed for minimal congestion. Unfortunately, such approaches do not guarantee minimal vehicle emissions. Given the negative impacts of vehicle pollutants as well as tighter national air quality standards, it is critical for regions to be able to identify capacity modifications to road networks such that vehicle emissions are minimal. This ability combined with land use changes and opportunities for non-auto travel are paramount in helping regions improve air quality. However, network design research has yet to directly address this topic. To fill this apparent gap in network design research, an emissions network design problem and solution method are proposed in this thesis. Three air pollutants are considered: hydrocarbons, nitrogen oxides, and carbon monoxide. The proposed model is applied to two road networks: Sioux Falls, ND and Anaheim, CA. The model is a bi-level optimization problem solved using a genetic algorithm and incorporates the influence of demand uncertainty. Findings indicate designing for minimal congestion tends to increase emissions of criteria air pollutants. However, not adding capacity to a road network also increases emissions of pollutants. Therefore, an optimization problem and solution method, such as the model presented here, is useful for identifying capacity additions that reduce vehicle emissions. It is also useful for understanding the tradeoffs between designing a network for minimal congestion versus minimal vehicle emissions.Item Nitrogen oxides emission control through reburning with biomass in coal-fired power plants(Texas A&M University, 2005-02-17) Arumugam, SenthilvasanOxides of nitrogen from coal-fired power stations are considered to be major pollutants, and there is increasing concern for regulating air quality and offsetting the emissions generated from the use of energy. Reburning is an in-furnace, combustion control technology for NOx reduction. Another environmental issue that needs to be addressed is the rapidly growing feedlot industry in the United States. The production of biomass from one or more animal species is in excess of what can safely be applied to farmland in accordance with nutrient management plans and stockpiled waste poses economic and environmental liabilities. In the present study, the feasibility of using biomass as a reburn fuel in existing coal-fired power plants is considered. It is expected to utilize biomass as a low-cost, substitute fuel and an agent to control emission. The successful development of this technology will create environment-friendly, low cost fuel source for the power industry, provide means for an alternate method of disposal of biomass, and generate a possible revenue source for feedlot operators. In the present study, the effect of coal, cattle manure or feedlot biomass, and blends of biomass with coal on the ability to reduce NOx were investigated in the Texas A&M University 29.31 kW (100,000 Btu/h) reburning facility. The facility used a mixture of propane and ammonia to generate the 600 ppm NOx in the primary zone. The reburn fuel was injected using air. The stoichiometry tested were 1.00 to 1.20 in the reburn zone. Two types of injectors, circular jet and fan spray injectors, which produce different types of mixing within the reburn zone, were studied to find their effect on NOx emissions reduction. The flat spray injector performed better in all cases. With the injection of biomass as reburn fuel with circular jet injector the maximum NOx reduction was 29.9 % and with flat spray injector was 62.2 %. The mixing time was estimated in model set up as 936 and 407 ms. The maximum NOx reduction observed with coal was 14.4 % and with biomass it was 62.2 % and the reduction with blends lay between that of coal and biomass.Item Ozone transport to and removal in porous materials with applications for low-energy indoor air purification(2013-05) Gall, Elliott Tyler; Corsi, Richard L.; Siegel, Jeffrey A.In the U.S. and other developed countries, humans spend the vast majority of their time within the built environment. As a result, a substantial portion of our collective exposure to airborne pollutants, even those of outdoor origin, occurs in indoor environments. In addition, building construction materials and operational practices are changing as we endeavor to reduce the energy burden of the built environment. These changes result in barriers and opportunities in mitigating exposure to indoor pollutants and the accompanying implications for human health. This dissertation advances knowledge regarding low-energy control of indoor ozone. Ozone is often considered a pollutant of outdoor concern. However, ozone in indoor environments presents important challenges regarding exposure, intake, and chemistry in the built environment. The investigations in this dissertation extend the state understanding of indoor transport and transformation of ozone, and the potential for using material-surface interactions in buildings to suppress concentrations of indoor ozone. The first objective relates to the determination of magnitudes of ozone removal and product emissions at room or building scales. This objective provides new data on reactive uptake and product generation in large-scale environments, develops Monte Carlo models describing indoor ozone removal by materials in homes, and compares active and passive methods of indoor ozone removal. The second objective addresses the need to develop improved air cleaning materials through experiments and modeling that address material-ozone reactions in porous materials. This objective advances the state of modeling heterogeneous reactive uptake of ozone by characterizing material physical properties and transport phenomena, determining their impact on ozone removal, and using these data to develop a more mechanistic model of material-ozone reactions. Ultimately, these investigations advance the engineering concepts that support the development of passive indoor pollutant controls, an important tool for reducing concentrations of indoor pollutants while supporting low-energy building initiatives. The combination of experimental characterization of ozone deposition velocities and product emission rates, whole-building Monte Carlo modeling, and mechanistic material/pollutant models provide important new data and approaches that expand the state of knowledge of the fate and transport of reactive pollutants in indoor environments.Item Synthesis of portland cement and calcium sulfoaluminate-belite cement for sustainable development and performance(2009-12) Chen, Irvin Allen; Juenger, Maria C.G.Portland cement concrete, the most widely used manufactured material in the world, is made primarily from water, mineral aggregates, and portland cement. The production of portland cement is energy intensive, accounting for 2% of primary energy consumption and 5% of industrial energy consumption globally. Moreover, Portland cement manufacturing contributes significantly to greenhouse gases and accounts for 5% of the global CO2 emissions resulting from human activity. The primary objective of this research was to explore methods of reducing the environmental impact of cement production while maintaining or improving current performance standards. Two approaches were taken, 1.) incorporation of waste materials in portland cement synthesis, and 2.) optimization of an alternative environmental friendly binder, calcium sulfoaluminate-belite cement. These approaches can lead to less energy consumption, less emission of CO2, and more reuse of industrial waste materials for cement manufacturing. In the portland cement part of the research, portland cement clinkers conforming to the compositional specifications in ASTM C 150 for Type I cement were successfully synthesized from reagent-grade chemicals with 0% to 40% fly ash and 0% to 60% slag incorporation (with 10% intervals), 72.5% limestone with 27.5% fly ash, and 65% limestone with 35% slag. The synthesized portland cements had similar early-age hydration behavior to commercial portland cement. However, waste materials significantly affected cement phase formation. The C3S–C2S ratio decreased with increasing amounts of waste materials incorporated. These differences could have implications on proportioning of raw materials for cement production when using waste materials. In the calcium sulfoaluminate-belite cement part of the research, three calcium sulfoaluminate-belite cement clinkers with a range of phase compositions were successfully synthesized from reagent-grade chemicals. The synthesized calcium sulfoaluminate-belite cement that contained medium C4A3 S and C2S contents showed good dimensional stability, sulfate resistance, and compressive strength development and was considered the optimum phase composition for calcium sulfoaluminate-belite cement in terms of comparable performance characteristics to portland cement. Furthermore, two calcium sulfoaluminate-belite cement clinkers were successfully synthesized from natural and waste materials such as limestone, bauxite, flue gas desulfurization sludge, Class C fly ash, and fluidized bed ash proportioned to the optimum calcium sulfoaluminate-belite cement synthesized from reagent-grade chemicals. Waste materials composed 30% and 41% of the raw ingredients. The two calcium sulfoaluminate-belite cements synthesized from natural and waste materials showed good dimensional stability, sulfate resistance, and compressive strength development, comparable to commercial portland cement.