<p>While the car fleet becomes increasingly larger it is important to lower the amounts of pollutants from each individual diesel or gasoline engine to almost zero levels. The pollutants from these engines predominantly originate from high NO_x emissions and particulates, in the case when diesel is utilized, and emissions at cold start from gasoline engines. One way of treating the high NO_x levels is to introduce ammonia in the diesel exhausts and let it react with the NO_x to form nitrogen gas and water, which is called SCR (Selective Catalytic Reduction). However, in order to make this system reduce NO_x efficiently enough for meeting future legislations, closed loop control is required. To realize this type of system an NO_x or ammonia sensor is needed. The cold start emissions from gasoline vehicles are primarily due to a high light-off time for the catalytic converter. Another reason is the inability to quickly heat the sensor used for controlling the air-to-fuel ratio in the exhausts, also called the lambda value, which is required to be in a particular range for the catalytic converter to work properly. This problem may be solved utilizing another, more robust sensor for this purpose.</p><p>This thesis presents the efforts made to test the SiC-based field effect transistor (SiC-FET) sensor technology both as an ammonia sensor for SCR systems and as a cold start lambda sensor. The SiC-FET sensor has been shown to be highly sensitive to ammonia both in laboratory and engine measurements. As a lambda sensor it has proven to be both sensitive and selective, and its properties have been studied in lambda stairs both in engine exhausts and in the laboratory. The influence of metal gate restructuring on the linearity of the sensor has also been investigated. The speed of response for both sensor types has been found to be fast enough for closed loop control in each application.</p> / On the day of the public defence of the doctoral thesis, the status of article III was: in press. Report code: LiU-Tek-Lic-2003:50.

It is the need of the hour to reduce the pollutants which poison our atmosphere and harm our health. The diesel engines are the most efficient IC engines in the world today, but paradoxically, they are also the engines which create the largest amounts of NOx, the pollutant that is most difficult to control with the existing technologies. In fact, the existing technologies are unable to meet the increasingly stringent standards for NOx. Even in bio-diesels, which in the future may be adopted as an important alternative fuel, NOx is the major pollutant. Thus not having a safe and stable method for NOx removal from the diesel exhaust stream is a cause for concern. In this thesis, there has been an attempt to address this issue by means of non-thermal plasma and catalysts. In this thesis, first the performance of the three sources was evaluated individually, along with two different HV electrodes, a helical wire and a straight wire. Secondly, the efficiencies of these three different types of sources were compared. Thirdly, a catalyst (Red Mud) and an adsorbent (NaZSM5) were cascaded with the plasma reactor to enhance the performance of the NOx removal process with the AC source as it gave the best results. All the experiments were performed with real diesel engine exhaust. The conclusions drawn from the experiments are as follows: The helical electrode consumes much lower power than the straight electrode. Therefore it is energy efficient. It also causes corona inception at lower voltages due to the strong non-uniformity of its electric field. The drawbacks of the helical electrode are an excess production of NO2 .it also does not work with the HFAC source, because at high frequency, the voltage doesn’t build up owing to the presence of only a dielectric medium of 2 mm thickness between the two electrodes. The performances of the 3 sources were compared. The HVAC unit gave the best NOx removal, followed by the MPC and finally, the HFAC source. The differences in efficiencies were related to both the magnitude of the peak voltage achieved by each device and the time period. It was also seen that when the voltage was high, a better efficiency can be achieved with lower power consumption. The comparison of the sources leads us to conclude that the high voltage AC source can be used as an economic alternative for NOx control. This is because a standard AC unit is easily available at higher voltages, and contains less electrical or mechanical complexity, whereas a pulsed source is comparatively expensive and complex. The NaZSM5 zeolite showed excellent removal at room temperature as an adsorbent when cascaded after the AC source, by reducing the NO2 levels consistently. The Red Mud showed reasonable catalytic activity at 400 C with the AC source. It was also efficient in compensating for the increase in the NO2 and CO concentration in the plasma atmosphere. Hence, both Red Mud and ZSM 5 are good candidates for a hybrid plasma-adsorbent or plasma-catalyst system. The combination better NOx/CO removal is the AC energization coupled with spiral electrode with either ZSM-5 or red mud. Scaling up the plasma/ plasma- catalyst system for handling higher flow rates will be the main task next. A method to optimize the source and load matching for better power transfer to the plasma reactor from the different sources also need to be developed. The design of the compact high frequency AC source must be upgraded for higher powers.

The increasing size of the car fleet makes it important to find ways of lowering the amounts of pollutants from each individual diesel or gasoline engine to almost zero levels. The pollutants from these engines predominantly originate from emissions at cold start, in the case when gasoline is utilized, and high NOx emissions and particulates from diesel engines. The cold start emissions from gasoline vehicles are primarily due to a high light-off time for the catalytic converter. Another reason is the inability to quickly heat the sensor used for controlling the air-to-fuel ratio in the exhausts, also called the lambda value, which is required to be in a particular range for the catalytic converter to work properly. This problem may be solved utilizing another, more robust sensor for this purpose. One way of treating the high NOx levels from diesel engines is to introduce ammonia in the exhausts and let it react with the NOx in a special catalytic converter to form nitrogen gas and water, which is called SCR (selective catalytic reduction). However, in order to make this system reduce NOx efficiently enough for meeting future legislations, closed loop control is required. To realize this type of system an NOx or ammonia sensor is needed. This thesis presents the efforts made to test the SiC-based field effect sensor device both as a cold start lambda sensor for gasoline engines and as an NH3 sensor for SCR systems in diesel engines. The MISiC (metal insulator silicon carbide) lambda sensor has proven to be both sensitive and selective to lambda, and its properties have been studied in lambda stairs both in gasoline engine exhausts and in the laboratory. There is, however, a small cross-sensitivity to CO. The influence of metal gate restructuring on the linearity of the sensor has also been investigated. The metal tends to form islands by time, which decreases the catalytic activity and thereby gives the sensor, which is binary when fresh, a linear behavior. Successful attempts to prevent the restructuring through depositing a protective layer of insulator on top of the metal were made. The influence of increasing the catalytic activity in the measurement cell was also studied. It was concluded that the location of the binary switch point of MISiC lambda sensors could be moved towards the stoichiometric value if the consumption of gases in the measurement cell was increased. The MISiC NH3 sensor for SCR systems has been shown to be highly sensitive to ammonia both in laboratory and diesel engine measurements. The influence of other diesel exhaust gas components, such as NOx, water or N2O has been found to be low. In order to make the ammonia sensor more long-term stable experiments on samples with different types of co-sputtered Pt or Ir/SiO2 gas-sensitive layers were performed. These samples turned out to be sensitive to NH3 even though they were dense and NH3 detection normally requires porous films. The speed of response for both sensor types has been found to be fast enough for closed loop control in each application. / On the day of the ublic defence of the doctoral thesis, the status of article IV was: accepted, article V was: submitted and article VII was: manuscript.

One major aspect of environmental pollution affecting human life and climate is air pollution. The harmful pollutants in the air include mostly hydrocarbons, carbon monoxide, carbon dioxide, nitrogen oxides as well as soot and other particulate matter. These pollutants result in several damaging effects on environment and living beings which include acid rain, photochemical smog, global warming and various health hazards in human beings even cancer. Major contribution of these pollutants is from man-made sources such as industrial and automotive emissions that employ fossil fuels. In our country, diesel constitutes more than 40% of the fossil fuel consumption. Studies show that diesel engine emissions contribute to 80% of nitrogen oxides amongst other air pollutants. In the context of stringent emission regulations being implemented all over the world, exhaust emission control, in general and nitrogen oxide emission in particular, is gaining significant importance. A review of recent literature indicates the significance and popularity of electrical discharge based non thermal plasma for exhaust cleaning applications in general, and NOx cleaning in particular. While the existing pre-combustion and catalyst based post-combustion nitrogen oxides (NOx) abatement techniques have inherent disadvantages owing to short shelf life, saturated engine modifications, cost concerns etc., the electrical discharge based non- thermal plasma techniques offer certain advantages in terms of cost and life factors. Several non-thermal plasma techniques viz., pulsed plasma, surface plasma, dielectric barrier discharge plasma etc., have been studied under different laboratory conditions. Interestingly, due to the high oxidizing environment that prevails in the discharge plasma zone, complete reduction of NOx by the plasma alone is becoming a challenging task. This has led the researchers to utilize additional processing techniques in cascade with discharge plasma. This additional gas cleaning technique may involve the use of adsorbents, catalysts or some other secondary treatment for eliminating the nitrogen oxides produced due to oxidizing reactions in the plasma chamber. One such additive can be an adsorbent, which can be commercially obtained or prepared from industrial wastes. In this thesis the adsorption properties of two industrial wastes were explored for the first time in conjunction with discharge plasma. The synergistic effect of plasma combined with an adsorbent shows promising results in NOx removal thus offering an effective solution to two environmental issues namely air pollution and open waste dumping. While the plasma, generally, refers to direct plasma treatment of exhaust, it can also be used for generation of ozone in a separate reactor which can subsequently be injected into the exhaust stream resulting in indirect plasma treatment. The current work focuses on both direct and indirect dielectric barrier discharge plasma treatment for NOx reduction in diesel engine exhaust cascaded with either oyster shells, a mariculture waste or lignite ash from lignite coal fired plant. Instead of conventional petro-diesel, biodiesel produced from the seeds of pongamia pinnata is used as the fuel. This biofuel, on one hand, causes considerable reduction in volatile organic compounds, particulate matter, soot, oil mist etc., but on the other hand may have higher concentrations of nitrogen oxides, an aspect that has motivated us to take up the research work envisaged in this thesis. It was observed in the laboratory environment that for a given power, both direct and indirect plasma treatments have resulted in NOx removal to the tune of 85 to 95% when cascaded with the adsorbents studied.

Le transport routier est responsable d’une part des émissions de particules fines, notamment dans les grandes agglomérations. Celles-ci ayant des répercussions graves sur la santé humaine et l’environnement, des normes d’émissions des véhicules de plus en plus strictes sont mises en place. Des limites en nombre de particules sont imposées et une obligation de connaitre l’état de santé des organes de post-traitement des gaz d’échappement est également entrée en vigueur (On-Board Diagnostic : OBD).Les capteurs résistifs ont montré de bons résultats pour la mesure de la concentration massique des particules et ont l’avantage d’être simples à mettre en oeuvre, robustes et peu onéreux. Le principe de fonctionnement du capteur est basé sur la mesure de la conductance entre des électrodes de platine. Celle-ci augmente avec le dépôt de suies.L’objectif de ce travail de thèse est de parvenir à déterminer les paramètres clés qui affectent la réponse du capteur. Trois flux de suies présentant des distributions en taille différentes ont été sélectionnés et caractérisés. Un quatrième flux de suies a permis d’appréhender l’impact d’une concentration massique inférieure. La réponse du capteur à ces différents flux de suies a été étudiée. Nous avons montré que la sensibilité et le temps de réponse du capteur sont optimaux pour une tension de polarisation donnée entre les deux électrodes dont la valeur dépend de la distribution en taille des suies. Ce phénomène a été expliqué par les propriétés électriques différentes des suies et modélisé par un équilibre entre accumulation et combustion par effet Joule des suies déposées permettant de simuler la réponse temporelle du capteur. / Road transport contributes to a part of the particulate matter emissions, especially in big cities. Due to the negative effect of these pollutants on the human health and environment, more and more stringent emission standards for automotive are applied. These emissions are now limited in number of particles per kilometer and the vehicle need to indicate when there is some failure of the systems of depollution (OBD: On-Board diagnostic).Resistive sensors have shown good results to measure soot particles mass concentration. They have advantage of being a simple and robust technology that can be easily manufactured at a cheap price. The sensor principle consists of conductance measurement between two platinum electrodes. Conductance increases with soot deposition. This work aims to define the key parameters that affect the sensors response. Three particles flow with different particles size distributions (centered at 90, 70 and 50 nm) were used and characterized. A fourth flow was used to see the impact of a lower mass concentration. The sensor response exposed to these different flows was studied. It was shown that the sensor sensibility and response times are optimal for a given polarization voltage between the electrodes whose value depends on the size distribution. This phenomenon was explained by the different electrical properties of the soot particles and modeled by equilibrium of soot accumulation and their combustion by Joule heating that permitting to simulate the sensor temporal response.

Orientadores: Cristiane Aparecida Martins, Pedro Teixeira Lacava / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T08:17:14Z (GMT). No. of bitstreams: 1 Squaiella_LucasLazaroFerreira_M.pdf: 3325572 bytes, checksum: a305c0e70b83a23effc5931811a53dc0 (MD5) Previous issue date: 2010 / Resumo: Veículos automotores são responsáveis pela maior parte da locomoção no mundo moderno. A principal forma de energia propulsora utilizada baseia-se na queima de combustíveis fósseis. Em sistemas reais de combustão o processo químico envolvido apresenta alto grau de complexidade que se traduz, na emissão de cinco principais espécies de poluentes atmosféricos, a saber, monóxido de carbono, compostos orgânicos (hidrocarbonetos não queimados ou apenas parcialmente queimados), particulados, óxidos sulfurosos e óxidos nitrogenados. Graças a crescente e necessária preocupação ambiental as normas relativas a emissões têm sido periodicamente revistas, sendo uma das principais o Padrão Europeu definido como Euro que disciplina veículos que circulam na Europa e demais países que como o Brasil que a adotam como modelo. Motores a diesel têm como emissão crítica os óxidos nitrogenados, NOx (NO + NO2) e as emissões de material particulado. As diferentes técnicas utilizadas para reduzir a formação destes poluentes podem ser divididas entre aquelas aplicadas durante o processo de combustão e as outras aplicadas somente após a combustão, ou seja, nos gases de exaustão. O presente trabalho utilizou-se de uma técnica que atua no processo de combustão conhecida como EGR, Recirculação Parcial dos Gases de Exaustão. O objeto de estudo é um motor diesel de quatro cilindros em linha, equipado com EGR que atende a Euro III, com limite de NOx igual a 5,0 g/kWh. A premissa do trabalho é a avaliação do potencial deste motor em atingir os níveis de emissões da norma Euro VI, com limite de NOx igual a 0,4 g/kWh. Para tal, serão mantidas as configurações originais do motor, alterando-se somente os componentes que fazem parte do sistema de EGR. O estudo foi realizado em diferentes etapas, I, II e III, durante as quais foram identificados os componentes de EGR que mais influenciam para a redução do NOx. Os resultados obtidos são satisfatórios, alcançando valores próximos ao objetivo, mostrando desta forma que o estudo é de grande aplicabilidade para os motores atuais e futuros / Abstract: Automotive vehicles are responsible for the most of locomotion in the modern world. The mainly propulsive energy used is based on burning of fossil fuels. In real combustion systems the chemical process involved a high complexity which results mainly in five types of air pollutants, that are, carbon monoxide, organic compounds as hydrocarbons unburned or partially burned, ashes, oxides sulfur and nitrogen oxides. Due to growing of necessity to care the environment concern, emissions standards have been reviewed periodically and one of the main is European Standard defined as Euro that discipline European vehicles and other countries like Brazil that concern it as a model. The most critical diesel engine emission are nitrogen oxides, NOx (NO + NO2) and particulate matter. The different techniques used to reduce the formation of these pollutants can be divided into those applied during the combustion process and other applied only after combustion, in the exhaust gases. This study used a technique that operates in the combustion process known as EGR, Exhaust Gas Recirculation. The object of study is a fourcylinder diesel engine, in line, equipped with EGR that meets the ,Euro III emission standards with NOx limit as 5,0 g / kWh. The premise work was evaluated the potential of this engine to achieve the Euro VI emission levels, with NOx limit as 0,4 g / kWh. To do this the original basic engine parts will be kept, to changing only the components that are part of the EGR system. The study was conducted at different stages I, II and III, to identify which EGR components have more influence to reduce NOx. The results are consider satisfactory, reaching values close to the goal, thus demonstrating that the study is of great applicability to current and future engines / Mestrado / Motores / Mestre em Engenharia Automobilistica

No description available.

In India, the expansion of industries and two-fold increase in motor vehicles over the last decade are posing a serious environmental crisis in the form of urban air pollution. Common pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs), and nitrogen oxides produced by industry and motor vehicles. Air pollution results from a variety of sources. The natural sources include volcanoes, forest fire, scattering soil, biological decay, lightning strikes, dust storms etc. and man-made sources include thermal power plants, vehicular exhausts, incinerators and various other industrial emissions. More than 60% of the air pollution is contributed by these man-made sources. Amongst the gaseous pollutants, the major concern and a challenging task is to control oxides of nitrogen, commonly referred to as NOx. In case of diesel engines, despite the modification in engine design and improvement in after treatment technologies, large amount of NOx continues is get emitted and attempts to develop new catalyst to reduce NOx have so far been less successful. Further, with the emission standards becoming more stringent, estimates are that NOx and particulate matter emission must be reduced by as much as 90%. In this context, the emergence of electrical discharge plasma technique in combination with the few existing technologies is providing to be economically viable and efficient technology. In this thesis emphasis has been laid on the discharge based non-thermal plasma for NOx removal. NOx from simulated gas mixture and actual diesel engine exhaust has been treated. The thesis mainly addresses the following issues. . • Performance evaluation of pipe-cylinder and wire-cylinder reactor for NOx removal . • Study of effect of plasma assisted adsorbent reactor on NOx removal . • Study of effect of adsorption and plasma based desorption using different adsorbent material and electrode configuration The first chapter provides introduction about the air pollutants and the existing NOx control technologies, a brief history of electric discharge plasma, a detailed literature survey and scope of the work. A detailed experimental setup consisting of voltage sources, gas system (simulated flue gas and diesel exhaust), gas analyzers, adsorbent materials are discussed in the second chapter. In the third chapter, NOx is treated by three different methods and are described in separate parts. In first part we have done a comparative study of NO/NOx removal using two different types of dielectric barrier discharge electrodes: a) wire-cylinder reactor, b) pipe-cylinder reactor. Investigations were first carried out with synthetic gases to obtain the baseline information on the NO/NOx removal with respect to the two geometries studied. Further, experiments were carried out with raw diesel exhaust under loaded condition. A high NOx removal efficiency 90% was observed for pipe-cylinder reactor when compared to that with wire-cylinder reactor, where it was 53.4%. In second part an analysis has been made on discharge plasma coupled with an adsorbent system. The cascaded plasma-adsorbent system may be perceived as a better alternative for the existing adsorbent based abatement system in the industry. During this study the exhaust is sourced from a diesel generator set. It was observed that better NO removal in a plasma reactor can be made possible by achieving higher average fields and subsequent NO2 removal can be improved using an adsorbent system connected in cascade with the plasma system. This part describes the various findings pertaining to these comparative analyses. The third and last part of chapter 3 consists of gas desorption from an adsorbent by non-thermal plasma, which is an alternative to conventional thermal desorption, has been studied in relation to diesel engine exhaust. In this process saturated adsorbent material is regenerated using high energetic electrons and excited molecules produced by non thermal plasma. The last Chapter lists out the major inferences drawn from this study.

Emissions from airport operations are of significant concern because of their potential impact on local air quality and human health. The currently limited scientific knowledge of aircraft emissions is an important issue worldwide, when considering air pollution associated with airport operation, and this is especially so for ultrafine particles. This limited knowledge is due to scientific complexities associated with measuring aircraft emissions during normal operations on the ground. In particular this type of research has required the development of novel sampling techniques which must take into account aircraft plume dispersion and dilution as well as the various particle dynamics that can affect the measurements of the aircraft engine plume from an operational aircraft. In order to address this scientific problem, a novel mobile emission measurement method called the Plume Capture and Analysis System (PCAS), was developed and tested. The PCAS permits the capture and analysis of aircraft exhaust during ground level operations including landing, taxiing, takeoff and idle. The PCAS uses a sampling bag to temporarily store a sample, providing sufficient time to utilize sensitive but slow instrumental techniques to be employed to measure gas and particle emissions simultaneously and to record detailed particle size distributions. The challenges in relation to the development of the technique include complexities associated with the assessment of the various particle loss and deposition mechanisms which are active during storage in the PCAS. Laboratory based assessment of the method showed that the bag sampling technique can be used to accurately measure particle emissions (e.g. particle number, mass and size distribution) from a moving aircraft or vehicle. Further assessment of the sensitivity of PCAS results to distance from the source and plume concentration was conducted in the airfield with taxiing aircraft. The results showed that the PCAS is a robust method capable of capturing the plume in only 10 seconds. The PCAS is able to account for aircraft plume dispersion and dilution at distances of 60 to 180 meters downwind of moving a aircraft along with particle deposition loss mechanisms during the measurements. Characterization of the plume in terms of particle number, mass (PM2.5), gaseous emissions and particle size distribution takes only 5 minutes allowing large numbers of tests to be completed in a short time. The results were broadly consistent and compared well with the available data. Comprehensive measurements and analyses of the aircraft plumes during various modes of the landing and takeoff (LTO) cycle (e.g. idle, taxi, landing and takeoff) were conducted at Brisbane Airport (BNE). Gaseous (NOx, CO2) emission factors, particle number and mass (PM2.5) emission factors and size distributions were determined for a range of Boeing and Airbus aircraft, as a function of aircraft type and engine thrust level. The scientific complexities including the analysis of the often multimodal particle size distributions to describe the contributions of different particle source processes during the various stages of aircraft operation were addressed through comprehensive data analysis and interpretation. The measurement results were used to develop an inventory of aircraft emissions at BNE, including all modes of the aircraft LTO cycle and ground running procedures (GRP). Measurements of the actual duration of aircraft activity in each mode of operation (time-in-mode) and compiling a comprehensive matrix of gas and particle emission rates as a function of aircraft type and engine thrust level for real world situations was crucial for developing the inventory. The significance of the resulting matrix of emission rates in this study lies in the estimate it provides of the annual particle emissions due to aircraft operations, especially in terms of particle number. In summary, this PhD thesis presents for the first time a comprehensive study of the particle and NOx emission factors and rates along with the particle size distributions from aircraft operations and provides a basis for estimating such emissions at other airports. This is a significant addition to the scientific knowledge in terms of particle emissions from aircraft operations, since the standard particle number emissions rates are not currently available for aircraft activities.

No description available.