The demands on tomorrows diesel engines regarding fuel consumption and emission levels keep getting more difficult to fulfill. Due to this fact, the control demand is getting bigger and bigger. To be able to comply with the Euro 6 standards, it is believed that engine control need to be conducted individually from cylinder to cylinder if the need for after-treatment systems should be minimized. Scania’s approach to handle emission levels so far has been to use exhaust gas recirculation (EGR). To be able to optimize the use of EGR it is necessary to know how the inert gases, water and carbon dioxide, are distributed between the cylinders. The distribution variation become even more difficult to predict since the EGR is cooled, sometimes leading to condensation of some of the water content. The condensation of water and its behavior in the inlet manifold is studied in this thesis. Different ways of measuring non-uniformity in the gas composition between cylinders with respect to EGR in general and water content in particular are evaluated. Using these results, measurements have been conducted on an engine and conclusions are drawn from them. The conclusions are that uneven distribution of above all liquid water, due to puddle formation, have an impact on emission formation that should be accounted for in some of the examined operating conditions.

Memory is subdivided into short- and long-term memory. The interaction between transcription factors (TF) and expressed genes are essential steps in memory formation. Some TFs that might be involved in memory formation include CREB, NF-kB and Egr-2. We hypothesized that there would be a difference in the expression levels of these TFs following learning in the Morris Water Maze (MWM). In study one, CD1 mice were categorized into two groups. Group 1 assigned as non-trained control group. Group 2 (experimental group) underwent 9 consecutive days of MWM training. In the second study, male C57BL/6 mice were categorized into four groups. Group 1 was a non-trained control group (allowed to swim randomly). Groups 2, 3, and 4 (experimental groups) had variations in their MWM training. Search strategies, escape latency, time spending in the target quadrant and number of attempts passing the missing platform, were measured. To evaluate the expression levels of TFs pre- versus post-learning, mice were sacrificed at the end of MWM. Hippocampi were separated and Western blot and immunohistochemical procedures were done. In study one, the escape latency decreased progressively toward the end of the acquisition phase in the trained group. The search pattern showed that the mice used primarily spatial strategies. Mice spent more time in the target quadrant during the retention phase. The number of passes over the missing platform peaked on the first day of the retention phase. NF-kB and CREB were expressed significantly higher in the control group versus the MWM trained mice (p = 0.0031 and p < 0.0001 respectively). There was no statistically significant difference in expression of Egr-2 between the two groups (p = 0.3092). In study two, Group 4 showed the highest and Group 1 the lowest levels of CREB expression. CREB and NF-kB were decreased following MWM training in study one. In study two CREB levels were highest in the Group 4 which had interval between the acquisition and retention phases. These differences could be due to multiphasic expression patterns and/or other experimental design issues. Further studies are warranted to examine time dependent differential expression of TFs in memory.

Previous research has shown that nitric oxide signalling in the lateral nucleus of the amygdala is required for the consolidation of Pavlovian conditioned fear. Given the evidence that nitric oxide can act as a retrograde signalling molecule in in vitro models of memory consolidation the question arises whether this is also occurring within behavioural memory models? Using auditory fear conditioning this research shows that nitric oxide does indeed act as retrograde signalling molecule in the fear system. Its synthesis in the lateral nucleus of the amygdala regulates conditioning induced expression of the immediate early gene early growth response gene 1 (EGR-1) in cells of the auditory thalamus that project to the lateral nucleus of the amygdala. The regulation of EGR-1 expression by the lateral nucleus of the amygdala was proven to be dependent on amygdala-based cellular excitation, nitric oxide synthesis and NR2B-NMDA receptor activation but not ERK/MAPK activity. Using an EGR-1 antisense oligonucleotide to prevent training induced EGR-1 expressions in the auditory thalamus it was shown that this gene upregulation is necessary for the consolidation of conditioned fear. Finally, inhibition of EGR-1 upregulation in the auditory thalamus was proven to impair conditioning induced increases in the presynaptic proteins synaptophysin, and synapsin II and II back in the lateral nucleus of the amygdala. Overall, the results of this dissertation have shown that nitric oxide acts as a retrograde messenger in a mammalian memory system by modulating gene expression in presynaptic cells. This modulation of gene expression serves to increase levels of presynaptic proteins back at the origin of nitric oxide synthesis. This supports the long standing doctrine that nitric oxide acts as a retrograde signalling molecule to coordinate presynaptic changes associated with memory formation.

Memory is subdivided into short- and long-term memory. The interaction between transcription factors (TF) and expressed genes are essential steps in memory formation. Some TFs that might be involved in memory formation include CREB, NF-kB and Egr-2. We hypothesized that there would be a difference in the expression levels of these TFs following learning in the Morris Water Maze (MWM). In study one, CD1 mice were categorized into two groups. Group 1 assigned as non-trained control group. Group 2 (experimental group) underwent 9 consecutive days of MWM training. In the second study, male C57BL/6 mice were categorized into four groups. Group 1 was a non-trained control group (allowed to swim randomly). Groups 2, 3, and 4 (experimental groups) had variations in their MWM training. Search strategies, escape latency, time spending in the target quadrant and number of attempts passing the missing platform, were measured. To evaluate the expression levels of TFs pre- versus post-learning, mice were sacrificed at the end of MWM. Hippocampi were separated and Western blot and immunohistochemical procedures were done. In study one, the escape latency decreased progressively toward the end of the acquisition phase in the trained group. The search pattern showed that the mice used primarily spatial strategies. Mice spent more time in the target quadrant during the retention phase. The number of passes over the missing platform peaked on the first day of the retention phase. NF-kB and CREB were expressed significantly higher in the control group versus the MWM trained mice (p = 0.0031 and p < 0.0001 respectively). There was no statistically significant difference in expression of Egr-2 between the two groups (p = 0.3092). In study two, Group 4 showed the highest and Group 1 the lowest levels of CREB expression. CREB and NF-kB were decreased following MWM training in study one. In study two CREB levels were highest in the Group 4 which had interval between the acquisition and retention phases. These differences could be due to multiphasic expression patterns and/or other experimental design issues. Further studies are warranted to examine time dependent differential expression of TFs in memory.

Previous research has shown that nitric oxide signalling in the lateral nucleus of the amygdala is required for the consolidation of Pavlovian conditioned fear. Given the evidence that nitric oxide can act as a retrograde signalling molecule in in vitro models of memory consolidation the question arises whether this is also occurring within behavioural memory models? Using auditory fear conditioning this research shows that nitric oxide does indeed act as retrograde signalling molecule in the fear system. Its synthesis in the lateral nucleus of the amygdala regulates conditioning induced expression of the immediate early gene early growth response gene 1 (EGR-1) in cells of the auditory thalamus that project to the lateral nucleus of the amygdala. The regulation of EGR-1 expression by the lateral nucleus of the amygdala was proven to be dependent on amygdala-based cellular excitation, nitric oxide synthesis and NR2B-NMDA receptor activation but not ERK/MAPK activity. Using an EGR-1 antisense oligonucleotide to prevent training induced EGR-1 expressions in the auditory thalamus it was shown that this gene upregulation is necessary for the consolidation of conditioned fear. Finally, inhibition of EGR-1 upregulation in the auditory thalamus was proven to impair conditioning induced increases in the presynaptic proteins synaptophysin, and synapsin II and II back in the lateral nucleus of the amygdala. Overall, the results of this dissertation have shown that nitric oxide acts as a retrograde messenger in a mammalian memory system by modulating gene expression in presynaptic cells. This modulation of gene expression serves to increase levels of presynaptic proteins back at the origin of nitric oxide synthesis. This supports the long standing doctrine that nitric oxide acts as a retrograde signalling molecule to coordinate presynaptic changes associated with memory formation.

This research work characterises diesel engine soot physiochemical properties and engine performance and emissions for the combustion of two common mineral diesel fuels (low and medium sulphur) and a RME B100 biodiesel fuel at two geometric compression ratios (19.5:1 and 16.5:1) and a broad range of EGR (10 to 55%) for an otherwise unmodified VW 1.9TDI 130PS engine. The principal focus of the research is the physiochemical characterisation of soot sampled from the engine exhaust manifold and also a DPF in the exhaust and exploring how the fuel type, compression ratio and EGR influence the soot properties and how these properties then influence the evolution of the soot in the exhaust.

With an increased urgency for global action towards climate change mitigation, this research was undertaken with the aim of evaluating post-combustion CO2 capture as an emission abatement strategy for gas-fired power plants. A dynamic rate-based model of a capture plant with MEA solvent was built, with imposed chemical equilibrium, and validated at pilot scale under transient conditions. The model predicted plant behaviour under multiple process inputs and disturbances. The validated model was next used to analyse the process and it was found that CO2 absorption is mass transfer limited. The model was then improved by explicitly adding reactions rate in the model continuity, the first such dynamic model to be reported for the capture process. The model is again validated and is observed to provide better predictions than the previous model. Next, high fidelity models of a gas-fired power plant, a scaled-up capture plant and a compression train were built and integrated for 90% CO2 capture. Steam for solvent regeneration is extracted from the power plant IP/LP crossover pipe. Net efficiency drops from 59% to 49%, with increased cooling water demand. A 40% exhaust gas recirculation resulted in a recovery of 1% efficiency, proving that enhanced mass transfer in the capture plant reduces solvent regeneration energy demands. Economic analysis reveals that overnight cost increases by 58% with CO2 capture, and cost of electricity by 30%. While this discourages deployment of capture technology, natural gas prices remain the largest driver for cost of electricity. Other integration approaches – using a dedicated boiler and steam extraction from the LP steam drum – were explored for operational flexibility, and their net efficiencies were found to be 40 and 45% respectively. Supplementary firing of exhaust gas may be a viable option for retrofit, as it is shown to minimise integrated plant output losses at a net efficiency of 43.5%. Areas identified for further study are solvent substitution, integrated plant part load operation, flexible control and use of rotating packed beds for CO2 capture.

With an increased urgency for global action towards climate change mitigation, this research was undertaken with the aim of evaluating post-combustion CO2 capture as an emission abatement strategy for gas-fired power plants. A dynamic rate-based model of a capture plant with MEA solvent was built, with imposed chemical equilibrium, and validated at pilot scale under transient conditions. The model predicted plant behaviour under multiple process inputs and disturbances. The validated model was next used to analyse the process and it was found that CO2 absorption is mass transfer limited. The model was then improved by explicitly adding reactions rate in the model continuity, the first such dynamic model to be reported for the capture process. The model is again validated and is observed to provide better predictions than the previous model. Next, high fidelity models of a gas-fired power plant, a scaled-up capture plant and a compression train were built and integrated for 90% CO2 capture. Steam for solvent regeneration is extracted from the power plant IP/LP crossover pipe. Net efficiency drops from 59% to 49%, with increased cooling water demand. A 40% exhaust gas recirculation resulted in a recovery of 1% efficiency, proving that enhanced mass transfer in the capture plant reduces solvent regeneration energy demands. Economic analysis reveals that overnight cost increases by 58% with CO2 capture, and cost of electricity by 30%. While this discourages deployment of capture technology, natural gas prices remain the largest driver for cost of electricity. Other integration approaches – using a dedicated boiler and steam extraction from the LP steam drum – were explored for operational flexibility, and their net efficiencies were found to be 40 and 45% respectively. Supplementary firing of exhaust gas may be a viable option for retrofit, as it is shown to minimise integrated plant output losses at a net efficiency of 43.5%. Areas identified for further study are solvent substitution, integrated plant part load operation, flexible control and use of rotating packed beds for CO2 capture.

The high demands on low fuel consumption and low emissions on the combustion engines of both today, and the future, is highly dependent on advanced control systems in order to fulfill these demands. The control systems and strategies are based on models which describe the physical system. The more accuratly the models describe the real world system, the more accurate the control will be, leading to better fuel economy and lower emissions. This master's thesis investigates and improves the mass flow model used for a compressible restriction, such as over the throttle valve, EGR valve, or the wastegate valve, for example. The standard model is evaluated and an improvement is proposed which does not assume isentropic flow. This seems to explain the deviation from the isentropic Psi-function shown in earlier research such as (Andersson:2005). Furthermore a throttle valve is analyzed in ANSYS in order to show the generation of entropy. The presence of pressure pulsations in a combustion engine is also evaluated, especially how they effect the otherwise assumed steady flow model. It is tested if a mean value pressure is sufficient or if one needs to take the pulsations in to account, and the result shows that a mean pressure is sufficient, at least for the throttle when typical intake manifold pulsations is present. A dynamic flow model is also derived which can be useful for pressure ratios close to one. The dynamic flow model is based on the standard equation but with an extra dynamic term, however it is not implemented and tested due to complexity and time limitation. The proposed new non-isentropic flow model has proven promising and can hopefully lead to lower emissions and better fuel economy.

Los motores de combusti'on interna est'an inmersos en una constante evoluci'on tecnol'ogica con el ¿n de mejorar sus prestaciones y satisfacer adem'as las cada vez m'as restrictivas normas anticontaminantes. En el caso de los motores diesel esto concierne especialmente a las emisiones de NOx y part'¿culas. Los sistemas destinados a reducir estas emisiones (inyecci'on directa common-rail, sobrealimentaci'on con geometr'¿a variable, recirculaci'on de gases de escape, trampas de part'¿culas, catalizadores, etc.) requieren de una cada vez m'as so¿sticada gesti'on electr'onica. En a¿nos recientes est'an disponibles en el mercado sensores capaces de medir las emisiones contaminantes del motor durante su operaci'on, lo que permite reformular el sistema tradicional de control del motor, hist'oricamente basado en el uso de variables intermedias como el gasto de aire. La presente Tesis Doctoral explora el potencial de estrategias de control del motor basadas en la medida proporcionada por un sensor de concentraci'on de NOx en el escape. En ella, tal medida es aplicada a la regulaci'on del sistema de recirculaci'on de gases de escape y, de forma m'as novedosa, al control coordinado de la inyecci'on y de la renovaci'on de la carga del motor. Adem'as, la capacidad de identi¿car modelos que predigan el comportamiento del motor permite la aplicaci'on de t'ecnicas de control predictivo basadas en modelos. La consecuci'on de estos objetivos se basa en los siguientes elementos: Puesta a punto de una instalaci'on experimental compuesta por un sistema de adquisici'on de se¿nales en tiempo real que permita la adquisici'on de las se¿nales de los sensores de serie del motor y la instalaci'on de nuevos sensores adicionales al motor, tanto convencionales como experimentales, as'¿ como la programaci'on y ejecuci'on de l'ogicas de control en tiempo real. El desarrollo de tal sistema de prototipado presenta una especial di¿cultad y es el primer paso para obtener los resultados que pretende esta Tesis. Obtenci'on de modelos matem'aticos capaces de predecir el comportamiento del motor, que permiten conocer el sistema y desarrollar algoritmos de control. Tales modelos permiten adem'as realizar una selecci'on de los emparejamientos entre sensores y actuadores, as'¿ como compensar el efecto que tengan las actuaciones sobre el par motor. Realizaci'on del control en bucle cerrado de los NOx medidos bas'andose en los modelos obtenidos y los sensores dispuestos en el motor. Se comparan distintas estrategias de control, incluyendo la evaluaci'on de sistemas de control conjunto del bucle de aire y de la inyecci'on. La Tesis Doctoral demuestra la posibilidad de emplear la medida de NOx para el control de los motores diesel sobrealimentados. / Cabrera López, P. (2013). Aplicación de la medida de NOx para el control de motores diesel sobrealimentados [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31205 / TESIS