by Luk Shiu-fai. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / Includes bibliographical references (p. 234-240). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

The indirect effects of a nearby lightning strike on an airborne vehicle with its long trailing conducting plume is not well understood. Since airborne vehicles and its payload are expensive, their loss as a result of either a direct strike or due to the induced current and voltage of a nearby lightning strike is not desirable. The electromagnetic field generated due to the induced current on the skin of the vehicle may get coupled with the internal circuitry through the apertures on the vehicle body. If the coupled electromagnetic energy is more than the damage threshold level of the sensitive devices of the control circuit, they may fail which may lead to aborting the mission or a possible degradation in the vehicle performance. It has been reported that lightning induced phenomena was the cause of malfunctioning as well as aborting of some of the lunar missions. So in the present work, the computation of induced current and voltage on the skin of the vehicle body in the presence of an ionized long trailing exhaust plume has been attempted. The lightning channel is assumed to be vertical to the ground plane and extends up to a height of 7.5 km. The radiated electric and magnetic fields from the lightning channel at different heights from 10 m to 10 km and for lateral distances varying from 20 m to 10 km from the lightning channel are computed and the field waveforms are presented. For the computation of the radiated electric and magnetic fields from the lightning channel, modified transmission line with exponential current decay (MTLE) model for representing the lightning channel and the Heidler’s expression for the lightning channel base current are used. The peak amplitude of the lightning current used is 12 kA with a maximum current derivative of 40 kA/µs. It is seen that the vertical electric field in general, is bipolar in nature and that the height at which the change in polarity reversal takes place increases with increase of lateral distance from the lightning channel. The vertical electric field just above the ground is unipolar for all lateral distances from the channel and this is because the contribution due to the image of the lightning channel dominates the vertical electric field. The horizontal electric field is always unipolar for all heights and all lateral distances from the lightning channel studied. The effect of variation in the rate of rise of lightning current (di/dt) and the velocity of lightning current on the radiated electric and magnetic fields for the above heights and distances have also been studied. It is seen that the variation in maximum current derivative does not have a significant influence on the electric field when ground is assumed as a perfect conductor but it influences significantly the horizontal electric field when ground has finite conductivity. The velocity of propagation of lightning current on the other hand has a significant influence for both perfectly as well as finitely conducting ground conditions. For the computation of the induced current and voltage on the body of the airborne vehicle due to the coupling of the above mentioned electromagnetic fields radiated from a near by lightning discharge, the vehicle and its exhaust plume have been modeled as a transmission line and Finite Difference Time Domain (FDTD) numerical technique has been used for the computation. Regardless of the vehicle size, the structure can be modeled as a nonuniform transmission line consisting of a series of sections consisting of capacitive and inductive components. These components of the vehicle and its exhaust plume are computed using the Method of Moment (MoM) technique. The interaction of the electromagnetic wave with the plume depends on the electrical conductivity as well as the gas dynamic characteristics of the plume. Hence, in this research work an attempt has also been made to study the electrical conductivity (σe) and permittivity (εe) as well as the gas dynamic properties of the exhaust plume taking into consideration its turbulent nature. In general, the airborne vehicle can be considered as perfectly conducting (conductivity 3x107 S/m) where as the plume has finite conductivity. The electrical properties of an airborne vehicle exhaust plume such as electrical conductivity and the permittivity and their distribution along axial and radial directions depend on several factors. They are (i) propellant composition, (ii) impurity content in the propellants which generate ionic charge particles in the exhaust and (iii) the characteristics of the exhaust plume intensive parameters such as temperature, pressure, velocity and the presence of shock waves. These properties of the exhaust plume are computed in the two separate regions of interest as discussed next. The first region is inside the combustion chamber and up to the nozzle throat of the vehicle and the second region is from the throat to the exterior i.e., the ambient atmosphere or the downstream of the plume. In the first region where chemical reaction kinetics have to be considered, NASA Chemical Equilibrium with Application (CEA) software package has been used to compute the intensive parameters of the fluid at the throat of the nozzle. The pressure in the combustion chamber is taken as 4410 kPa and the back pressure at the exit plane is taken as 101.325 kPa. In the second region, FLUENT software package have been used for the fluid dynamic study of the exhaust plume from the vehicle nozzle throat to the exterior domain. The data obtained from the first region using CEA provides the parameters at the nozzle throat that are used as input parameters for the second region. In the study, a conical nozzle configuration of throat radius (rt) of 0.0185 m (nozzle exit plane radius is 0.05 m), half cone angle of 18º and nozzle expansion ratio (Ae/At) of 7.011 are used. The contour plot of the intensive parameters of the exhaust plume and the mass fraction of the charged particles are presented. The vehicle exhaust flow passes through different types of expansion and compression waves. In the present work, simulation is done for a slightly under expanded nozzle i.e. nozzle exit static pressure is slightly more than the ambient static pressure. Since the exit pressure is more than the ambient pressure, the exhaust gases expand to reach the ambient pressure. As the expansion waves reach the contact discontinuity (i.e. the boundary where the outer edge of the gas flow meets the free stream air), they again reflect back inward to create compression waves. These compression waves force the flow to turn back inward and increase its pressure. If the compression waves are strong enough, they will merge into an oblique shock wave. In the present work, more than eight such barrel shocks are captured. When the shock waves are generated, Mach number reduces sharply and static temperature and static pressure increases where as the total temperature of the exhaust remains constant in the shock wave formations. The characteristics of the plume such as pressure, temperature, velocity and concentration of the charged particles (i.e., e¯, Na+ and Cl¯) and neutral species such as CO, CO2 , Cl, H, HCl, H2O, H2 , N2, Na, NaCl, O, OH and O2 along axial and radial directions in the external domain have been studied. The above parameters are used to compute the collision frequencies and plasma frequencies of the charged particles as well as the number density of the species along axial and radial directions of the exhaust plume. These parameters are used to compute the effective conductivity distribution in the axial and radial directions for an incident electromagnetic field of frequency 1 MHz. The peak value of the conductivity computed is 0.12 S/m near the exit plane and it reduces to 0.02 S/m at an axial distance of 7.5 m from the exit plane which is well within the range suggested in the published literature. It has been observed that the oscillation in the conductivity along axial direction is a reflection of the shock wave formation in the exhaust plume. The electrical conductivity and the relative permittivity of the exhaust plume have been computed for three different radii of the nozzle at the exit plane i.e., 0.025 m, 0.05 m and 0.075 m. It is seen that the distribution of the conductivity and relative permittivity along the axial direction of the exhaust are independent of the nozzle exit plane radius. To study the coupling of lightning electromagnetic field with the vehicle and its exhaust plume two cases have been considered. These are (i) when the vehicle and its exhaust plume are at certain height above the ground and (ii) when the exhaust plume is touching the ground. The dimensions of the vehicle used in the study are as follows: length of the vehicle is 20 m and the length of its exhaust plume is 75 m. The radius of the vehicle is taken as 0.5 m. The vehicle and its exhaust plume are assumed to be at a lateral distance of 250 m from the lightning channel. In case one, when the vehicle and its inhomogeneous exhaust plume tip is at a height of 10 m above the ground, both the ends are open. So the reflection coefficients of the current wave and voltage wave at the end points are -1 and +1 respectively irrespective of the characteristic impedances of the vehicle and its exhaust plume. So when the reflected current propagates it will tend to reduce along the length of the object. Hence, the induced current at the end points are zero and the currents in the end segments are less than those in the intermediate segments. The spatial distribution of the peak magnitude of the time varying induced current, |Imax|, in each segment along the length of the vehicle without and with the exhaust plume are presented. In case of vehicle without plume, the maximum value of the induced current is at the middle segment of the vehicle and its value is 4.8 A. The presence of the inhomogeneous plume enhances the maximum value of the induced current to 33 A and its position is shifted to the exhaust plume side. When the voltage wave propagates, it will enhance the induced voltage in the vehicle body. The time varying potential difference between the end points of the vehicle without plume and the vehicle with its exhaust plume which drives the induced current are computed and it is seen that the potential difference for the vehicle without plume is unipolar whereas it is bipolar for the vehicle with exhaust plume. The lightning induced current on the skin of the vehicle will generate an electromagnetic field which may couple with the internal electronic devices and circuits through the apertures. The amount of electromagnetic energy that will be transmitted through an aperture on the vehicle skin and coupled with the internal electronic equipments depends on the characteristics of the induced current on the skin of the vehicle, the electrical size, shape, orientation and location of the aperture and the location of the internal electronic devices with respect to the aperture. So the time varying induced current and its di/dt at three different locations on the vehicle body i.e., tail of the vehicle, middle of the vehicle and vehicle nose are computed. It is seen that the induced current on the vehicle and its di/dt in the absence of the plume are oscillating in nature but they are critically damped in the presence of the trailing inhomogeneous exhaust plume. It also shows that the enhancement of induced current and its di/dt at the tail are much more than at the middle or at the nose of the vehicle which is true for an electrically short vehicle i.e., lv/λmin ≈ 0.067 as cited in the literature. So the presence of an aperture on the skin of the vehicle near to tail will transmit maximum electromagnetic energy into the inside of the vehicle. Therefore during design of the electrically short airborne vehicles, any aperture should be avoided near the tail of the vehicle or internal electronic devices should be placed away from the tail of the vehicle. In case 2, when the plume is touching the ground, the transient induced current in the plume will propagate into the soil. The effective impedance for smaller currents will be quite high (the inductance and capacitance effect are not taken into consideration for calculating the impedance. So the impedance of the soil is dominated by only the resistance). However, as soon as the current exceeds a certain value, the resulting soil gradient can reach the breakdown gradient of the soil i.e., 200-500 kV/m as cited in literature resulting in soil ionization. This will effectively lower the soil impedance. These dynamic characteristics of the soil resistance with induced current are incorporated by considering the expression for the soil resistance. To study the effect of soil resistivity on the time varying induced current and the voltage, computations have been done for various resistivities of the soil i.e., 0 Ωm, 100 Ωm and 200 Ωm. For soil resistivity of 0 Ωm, the reflection coefficients at the ground and at the open ends for the current wave are +1 and -1 respectively. So at the ground end, the reflected current wave will enhance and at the open end it will diminish as it propagates along the length of the vehicle and its exhaust. As the resistivity of the soil increases, the reflection coefficient of the current at the ground end decreases from +1, so the peak magnitude of the current reduces along the length till the length is half of the total length of the plume and the vehicle. Therefore, the peak magnitude of the induced current in the ground segment is much more than the peak magnitude of the current in the segment at the open end. For a finitely conducting plume, the peak value of the potential difference between the two ends of the vehicle and its exhaust plume are 92 kV, 91 kV and 90 kV for soil resistivities of 0 Ωm 100 Ωm and 200 Ωm respectively. Therefore the influence of the soil resistivity on the induced current is found to be not much significant. The spatial distribution of the peak magnitude of the time varying induced current in each segment along the length of the vehicle with inhomogeneous exhaust plume for the above three different soil resistivities are presented at a lateral distance of 250 m from the lightning channel. It is seen that when the plume is touching the ground, the induced current on the vehicle at the tail, middle and nose sections are marginally more than when the vehicle and its exhaust are at a height of 10 m above the ground. The effects of different parameters such as peak value and maximum di/dt of lightning current, velocity of lightning current, lateral distance of the vehicle from lightning channel and the height of the tip of the exhaust plume above the ground on the induced current and voltage on the airborne vehicle have also been studied. The peak amplitude of the lightning current used are 30 kA and 100 kA in addition to 12 kA mentioned earlier for the field computation. Also maximum di/dt values of 40 kA/µs and 120 kA/µs for the lightning current have been used for the computation. It is observed that the induced current increases with increase of the peak value, maximum di/dt as well as the velocity of propagation of the lightning current where as the induced current will reduce with increase of lateral distance and height of the tip of the exhaust plume above the ground. As an offshoot of the present work, the axial and radial distribution of the parameter, σe/ωεe (loss tangent of the exhaust plume) for an incident electromagnetic wave (lightning electromagnetic field) frequency of 1 MHz have been computed to study the conducting properties of the exhaust plume. σe/ωεe of the exhaust plume at 1 MHz frequency varies from 2324 to 365. Since σe/ωεe >>1, the plume behaves as a good conductor and the displacement currents can be neglected. In addition to this, the variation of parameter σe/ωεe for frequency ranges of 0.1 MHz to 5 GHz are also studied where σe and εe are the maximum effective conductivity and permittivity of the exhaust plume at the chosen frequency of an incident EM wave. It shows that the parameter σe/ωεe is 1.8x104 at 0.1 MHz and reduces to 0.45 for 5 GHz and its value is 1 at a frequency of 2.285 GHz. Therefore at lower EM wave frequency, the exhaust plume behaves as a good conductor and that conductivity reduces with increase of the frequency. The exhaust plume in the present study behaves as a good conductor below or at the EM wave frequency of 2.285 GHz. The microwave attenuation of electromagnetic wave through the ionized plume (the angle of incidence of microwave is 90o and transmission of microwave is always transverse to the exhaust plume) has also been studied using the above electrical characteristics computed and it is seen that the attenuation follows the axial variation in the conductivity of each cross section of the plume. In the present work, a theoretical model has also been developed to compute the microwave attenuation through the vehicle exhaust plume using the electrical conductivity computed earlier for any angle of incidence of the microwave. The thesis also lists some additional topics for further studies.

In the last decades, the focus of internal combustion engine development has moved towards more efficient and less pollutant engines. In a Diesel engine, approximately 30-40% of the energy provided by combustion is lost through the exhaust gases. The exhaust gases are hot and therefore rich of energy. Some of this energy can be recovered by recycling the exhaust gases into turbocharger. However, the energy losses in the exhaust port are highly undesired and the mechanisms driving the total pressure losses in the exhaust manifold not fully understood. Moreover, the efficiency of the turbine is highly dependent on the upstream flow conditions. Thus, a numerical study of the flow in the exhaust port geometry of a Scania heavy-duty Diesel engine is carried out mainly by using the Large Eddy Simulation (LES) approach. The purpose is to characterize the flow in the exhaust port, analyze and identify the sources of the total pressure losses. Unsteady Reynolds Averaged Navier-Stokes (URANS) simulation results are included for comparison purposes. The calculations are performed with fixed valve and stationary boundary conditions for which experimental data are available. The simulations include a verification study of the solver using different grid resolutions and different valve lift states. The calculated numerical data are compared to existent measured pressure loss data. The results show that even global parameters like total pressure losses are predicted better by LES than by URANS. The complex three-dimensional flow structures generated in the flow field are qualitatively assessed through visualization and analyzed by statistical means. The near valve region is a major source of losses. Due to the presence of the valve, an annular, jet-like flow structure is formed where the high-velocity flow follows the valve stem into the port. Flow separation occurs immediately downstream of the valve seat on the walls of the port and also on the surface of the valve body. Strong longitudinal, non-stationary secondary flow structures (i.e. in the plane normal to the main flow direction) are observed in the exhaust manifold. Such structures can degrade the efficiency of a possible turbine of a turbocharger located downstream on the exhaust manifold. The effect of the valve and piston motion has also been studied by the Large Eddy Simulation (LES) approach. Within the exhaust process, the valves open while the piston continues moving in the combustion chamber. This process is often analyzed modeling the piston and valves at fixed locations, but conserving the total mass flow. Using advanced methods, this process can be simulated numerically in a more accurate manner. Based on LES data, the discharge coefficients are calculated following the strict definition. The results show that the discharge coefficient can be overestimated (about 20 %) when using simplified experiments, e. g. flow bench. Simple cases using fixed positions for valve and piston are contrasted with cases which consider the motion of piston and/or valves. The overall flow characteristics are compared within the cases. The comparison shows it is impossible to rebuild the dynamic flow field with the simplification with fixed valves. It is better to employ LES to simulate the dynamic flow and associated losses with valve and piston motion. / <p>QC 20131204</p>

In the last few decades India has advanced socioeconomically due to the rapid growth of industries and automobile sector. This in turn increases the use of fossil fuel and diesel. The atmosphere gets polluted due to the harmful substances, which comes from the burning of fuel. These pollutants can be in the form of gaseous, liquid or solid particulate. Diesel engines, the major source of power in industries and automobiles, play a significant part in causing air pollution. The major pollutants in diesel exhaust are oxides of nitrogen (NOX), sulphur dioxide (SO2), carbon monoxide (CO), hydrocarbons (HC), particulate matter (PM), volatile organic compounds (VOC), aldehydes and alcohols. Due to the heavy consumption of diesel as a fuel there is an urgent need to control diesel exhaust. Diesel exhaust is a complex mixture of several gases and fine particles (commonly known as soot) that contains more than 40 toxic air contaminants. Amongst the gaseous pollutants in diesel exhaust, the major concern and a challenging task is to control oxides of nitrogen, commonly referred to as NOX as it is the major contributor for acid rain, photochemical smog etc. Successful control of emissions from diesel engines is yet to be achieved. The conventional techniques which are available to control emission now are either difficult to operate or does not satisfy the stringent emission standards. This has made the researchers throughout the world to find an alternative and effective non-conventional after treatment technique to reduce diesel engine emission. The failure of conventional techniques lead to the development of non-conventional techniques such as high voltage electric discharge based plasma which has already been proved to be economical and highly efficient in industrial electrostatic precipitators. Electric discharge plasma or non-thermal plasma produce energetic electrons which react with background molecules in flue gas leading to active species such as radicals. These radicals being chemically active selectively react with the harmful pollutants facilitating their removal/reduction. The present thesis work is an attempt to provide a technical solution to achieve higher removal efficiencies of oxides of nitrogen in the backdrop of shortcomings that exist in conventional technologies to do so. The current thesis describes the research in four stages: (i) studies on NOX removal from diesel exhaust by cross-flow DBD reactor, where design and fabrication of cross-flow DBD reactor, exhaust treatment using cross-flow DBD reactor and exhaust treatment with cascaded plasma-adsorbent technique is described (ii) studies on NOX removal from diesel exhaust by compact discharge plasma sources, where design and fabrication of high frequency high voltage AC (HVAC) using old television flyback transformer, Design and fabrication of high voltage pulse (HVPulse) using automobile ignition coil, exhaust treatment with both HVPulse and HVAC and exhaust treatment with cascaded plasma-adsorbent technique is described (iii) studies on NOX removal from diesel exhaust using solar powered discharge plasma source is described (iv) studies on the NOX removal from diesel exhaust using red mud, where exhaust treatment with red mud and Exhaust treatment cascaded plasma-red mud is covered. The results have been discussed in light of enhancing the NOX removal efficiency for stationary and automobile engine exhausts.

SammanfattningIntroduktion: Sedan år 2000 har antalet byggnader i Sverige ökat kraftigt. Enligt Statiska centralbyrån (SCB) fanns över 5 miljoner bostäder i Sverige i slutet av år 2021. Av dessa bostäder är cirka 42 % villor, 51 % flerbostadshus och resterande är lägenheter i specialbostäder. Energiförbrukningen i småhus har ökat med cirka 22% sedan 1970-talet, främst på grund av ökad användning av cirkulationspumpar, golvvärme och ventilation. Detta har resulterat i ökad miljöpåverkan från byggsektorn. Effektivisering av ventilationssystem har varit ett fokusområde under lång tid, eftersom användningsfasen av ventilationssystemen har visat sig ha hög energianvändning och stor miljöpåverkan. En studie visar att VVS-systemen påverkar miljön både vid tillverknings- och användningsfasen. Dessutom har nya lågenergihus en högre miljöpåverkan i byggfasen på grund av användningen av mer material för att minska driftanvändningen. Valet av ventilationssystem är avgörande för villor, eftersom ett effektivt ventilationssystem inte bara förbättrar inomhusluften utan också minskar risken för hälsoproblem som kan uppstå vid otillräcklig ventilation. Nyckelord: Livscykelkostnad, LCC, Ventilationssystem, Självdragssystem, FTX-system, VIP-Energy, Från- och tilluftssystem, Värmeåtervinning. Syfte: Syftet med examensarbetet är att visa att valet av ventilationssystem har betydelse för minskad klimatpåverkan vid tillverknings- och användningsfasen under 30 års tid. Mål: Målet är att ta fram vilket av självdragsventilation och från- och tilluftssystem med värmeåtervinning som är mest ekonomiskt och ger lägst klimatpåverkan baserat på ett livscykelperspektiv på ett småhus under en kalkylperiod på 30 år. Frågeställningar: Vilken av självdrag och FTX är mest effektivt med tanke på energiförbrukningen under tillverknings- och användningsfasen?Hur påverkar självdrag respektive FTX-systemet uppvärmningskostnaderna för ett småhus under förutsättning att uppvärmningen sker med fjärrvärme?Vilket av de två ventilationssystemen är mest ekonomisk lönsamt enligt en jämförande LCC, baserad på ett småhus med en kalkylperiod på 30 år?Vilket av ventilationssystemen orsakar störst klimatpåverkan? Metod: Metoden är en fallstudie där VIP-Energy används för att visa byggnadens energiförbrukning timme för timme under ett helt år. En LCC-beräkning utförs för att bestämma kostnaden för ventilationssystemet under dess livslängd, inklusive uppskattade underhållskostnader och nyinvesteringar. Slutsats: Baserat på energiförbrukningen under tillverknings- och användningsfasen är det mer effektivt att använda självdrag istället för ett FTX-system. Självdrag med vedeldning har ett lägre fjärrvärmebehov jämfört med FTX-systemet och ger därmed lägre årliga uppvärmningskostnader. Över en 30-årsperiod har självdragssystemet en lägre total livscykelkostnad än FTX-systemet. FTX-systemet har en högre elförbrukning och därmed en större påverkan på klimatet än självdragssystemet. / AbstractIntroduction: Since the year 2000, the number of buildings in Sweden has seen a significant increase. According to the Statistics Sweden (SCB), there were over 5 million dwellings in Sweden at the end of 2021. Out of these dwellings, approximately 42% are single-family houses, 51% are multi-family buildings, and the remaining is apartments in specialized housing. The energy consumption in single-family houses has increased by around 22% since the 1970’s, primarily due to the increased use of circulation pumps, underfloor heating, and ventilation. This has resulted in an increased environmental impact from the construction sector. Efficiency improvements in ventilation systems have been a longstanding focus due to the high energy consumption and significant environmental impact associated with their operational phase. A study reveals that HVAC systems impact the environment both during the manufacturing and the operational phases. Furthermore, new low-energy buildings have a higher environmental footprint during the construction phase due to the increased use of materials aimed at reducing operational energy consumption. The choice of a ventilation system is crucial for homes, as an efficient ventilation system not only improves indoor air quality but also reduces the risk of health problems that can arise from inadequate ventilation. Keywords: Life Cycle Cost, LCC, Ventilation System, Self-Exhaust Ventilation, Supply and Exhaust Ventilation, VIP-Energy, Supply and Exhaust Air System, Heat Recovery. Purpose: The purpose of the thesis is to demonstrate that the choice of ventilation system has a significant impact on reducing environmental emissions during the manufacturing and operational phases over a 30-year period. Goal: The objective is to determine which of self-exhaust ventilation and supply and exhaust ventilation with heat recovery is the most cost-effective and has the lowest climate impact based on a life-cycle perspective for a single-family building over a calculation period of 30 years.Questions: Which of self-exhaust ventilation and supply and exhaust ventilation is the most efficient in terms of energy consumption during the manufacturing and usage phases?How do self-exhaust ventilation and supply and exhaust ventilation affect the heating costs for a single-family building assuming that heating is provided through district heating?Which of the two ventilation systems is most economically viable according to a comparative Life Cycle Cost (LCC) analysis, based on a single-family building with a calculation period of 30 years?Which of the two ventilation systems causes the greatest climate impact?

Mobile source emissions are a major contributor to global and local air pollution. Governments and regulatory agencies have been increasing the stringency of regulations in the transportation sector for the last ten years to help curb transportation sector air pollution. The need for regulations has been emphasized by scientific research on the impacts from ambient pollution, especially research on the effect of particulate matter on human health. The particulate emissions from diesel vehicles, diesel particulate matter (DPM) is considered a known or probable carcinogen in various countries and increased exposure to DPM is linked to increased cardiovascular health problems in humans. The toxicity of vehicle emissions and diesel particulate emissions in particular, in conjunction with an increased awareness of potential petroleum fuel shortages, international conflict over petroleum fuel sources and climate change science, have all contributed to the increase of biodiesel use as an additive to or replacement for petroleum fuel. The goal of this research is to determine how this increased use of biodiesel in the particular emission testing setup impacts urban air quality. To determine if biodiesel use contributes to a health or climate benefit, both the size range and general composition were investigated using a comprehensive comparison of the particulate component of the emissions in real time. The emissions from various biodiesel and diesel mixtures from a common diesel passenger vehicle were measured with a cavity ring-down transmissometer (CRDT) coupled with a condensation particle counter, a SMPS, a nephelometer, NOx, CO, CO2, and O3 measurements. From these data, key emission factors for several biodiesel and diesel fuel mixtures were developed. This approach reduces sampling artifacts and allows for the determination of optical properties, particle number concentration, and size distributions, along with several important gas phase species' concentrations. Findings indicate that biodiesel additions to diesel fuel do not necessarily have an air quality benefit for particulate emissions in this emission testing scenario. The often cited linear decrease in particulate emissions with increasing biodiesel content was not observed. Mixtures with half diesel and half biodiesel tended to have the highest particulate emissions in all size ranges. Mixtures with more than 50% biodiesel had slightly lower calculated mass for light absorbing carbon, but this reduction in mass is most likely a result of a shift in the size of the emission particles to a smaller size range, not a reduction in the total number of particles. Evaluation of the extensive optical properties from this experimental set-up indicates that biodiesel additions to diesel fuel has an impact on emission particle extinction in both visible and near-IR wavelengths. The B99 mixture had the smallest emission factor for extinction at 532 nm and at 1064 nm. For the extinction at 532 nm, the trend was not linear and the emission factor peaked at the B50 mixture. Results from intensive properties indicate that emissions from B5 and B25 mixtures have Ångström exponents close to 1, typical for black carbon emissions. The mixtures with a larger fraction of biodiesel have Ångström exponent values closer to 2, indicating more absorbing organic matter and/or smaller particle size in the emissions. Additional experimental testing should be completed to determine the application of these results and emission factors to other diesel vehicles or types of diesel and biodiesel fuel mixtures.

This research examines the use of archived weigh-in-motion (WIM) data to estimate link-based heavy-vehicle emissions for Oregon highways. This research combined data on vehicle speed, highway grade, and gross vehicle weight and relationship between these elements in published research to estimate the carbon dioxide (CO2) and nitrogen oxide (NOx) emissions from trucks. Sensitivity analysis was conducted on the impact of uphill grade and gross vehicle weight on truck speed and emissions. The results suggest that with the data available in the weigh-in-motion archive and with a reasonable set of assumptions, link-based emissions for heavy-duty vehicles can be estimated. The carbon dioxide (CO2) and nitrogen oxide (NOx) emissions are found to increase when the speed, gross vehicle weight, or road grade increases. The relationship between nitrogen oxide (NOx) emissions and vehicle weight was estimated to be linear. The potential to estimate the link-based heavy-vehicle emissions for Oregon highways using the weigh-in-motion data archive, which was mainly designed to estimate truck counts, has a great value in setting new measures to mitigate the heavy-vehicle emissions.

In 2009, Cobb County School District (CCSD) and Georgia Institute of Technology (Georgia Tech) received a competitive federal grant to implement an idle and tailpipe emission reduction program in the CCSD bus fleet. The project is designed to reduce school bus idling by installing GPS and idle detection systems in the bus, providing bus dispatchers with a web system to track vehicle activity and idling in real-time, and to automatically shut off the engine when idle thresholds at specific locations are exceeded. A team of Georgia Tech researchers is implementing the anti-idle program and estimating the emissions and fuel savings from the project using approved modeling methods. This thesis presents the results of the emission modeling process, as well as an analysis of baseline school bus idling activity. EPA's MOVES mobile source emission model was used to develop emission rates for school buses for each operating mode, which are defined by the instantaneous vehicle speed, acceleration and scaled tractive power. Local data for Cobb County and Atlanta were collected and input into the MOVES model. The pollutants modeled include carbon dioxide, carbon monoxide, particulate matter (coarse and fine), oxides of nitrogen, and gaseous hydrocarbons. The vehicle activity data collected through the GPS and communications equipment installed in the buses were classified into the operating mode bins for each second of recorded data, and multiplied by the corresponding emission rate to determine the total modal emissions before and after project implementation. Preliminary results suggest that thousands of gallons of diesel fuel and thousands of dollars can be saved with the project, improving overall fleet fuel efficiency by 2%, as well as reducing emissions in some categories by as much as 38%.

In the last few decades India has advanced socioeconomically due to the rapid growth of industries and automobile sector. This in turn increases the use of fossil fuel and diesel. The atmosphere gets polluted due to the harmful substances, which comes from the burning of fuel. These pollutants can be in the form of gaseous, liquid or solid particulate. Air pollution, both indoor and outdoor, is a significant cause of health problems worldwide. In the automobile sector diesel engine exhaust is the major contributor for the air pollution amounting to about 60%. Exhaust generally contains oxides of Carbon, Nitrogen, Sulfur, Soot, Oil mist etc. Due to the heavy consumption of diesel as a fuel there is an urgent need to control diesel exhaust. Successful control of emissions from combustion engines particularly from diesel engines is yet to be achieved. The conventional techniques which are available to control emission now are either difficult to operate or does not satisfy the stringent emission standards. Among the major pollutants of diesel exhaust NOx is one of the pollutants to be taken care of as it is the major contributor for acid rain, photochemical smog etc. Further the NOx cause health problems leading to respiratory diseases, pneumonia, asthma etc. Till date, despite improvement in aftertreatment technologies, diesel engine continues to emit large amounts of NOx. The failure of conventional techniques lead to the development of non-conventional techniques such as high voltage electric discharge based plasma which has already been proved to be economical and highly efficient in Industrial Electrostatic Precipitators. Till now all the research regarding control of NOx has been done at the laboratory level using conventional DC and rotary spark gap based high voltage power supply. However, this is not a feasible option for Automobiles. The objective of this thesis is, therefore, to design and fabricate a solar powered high voltage power supply to be retrofitted into a vehicle. This leads to the development of power supply which will be of smaller size & capable of supplying high voltage to the gas treatment reactor. In the present work emphasis has been made on the design and development of a DC/HVAC power unit based on switch mode power supply approach. The thesis mainly presents the following issues:  Design & fabrication of solar powered high voltage high frequency power supply for the production of Electric Discharge Plasma.  Actual diesel exhausts treatment with the Electric Discharge Plasma.  Exhaust treatment with conventional 3 way CAT.  Exhaust treatment with cascaded plasma & catalyst/adsorbent system  Comparative analysis. The high voltage power supply gives an output of 16kV peak to peak at 12.2 kHz with a 50W power rating. This high frequency high voltage is applied to the gas treatment reactor and studies on actual diesel exhaust cleaning were carried out. It was observed that there was substantial improvement in the NOx removal under this high frequency AC application when compared to conventional 3-way catalytic converter. Studies have also been carried out at different engine loads and a comparative analysis has been made by cascading the NTP with adsorbents & catalysts and results as discussed in detail.

Diss. (sammanfattning) Umeå : Umeå universitet, 2009. / Härtill 5 uppsatser. Även tryckt utgåva.