Numerous investigations have been conducted to determine the effect of fuel composition and molecular structure on particulate emissions using exhaust gas analysis, but relatively few measurements have been obtained in-cylinder or under conditions where fuel effects can be isolated from other variables. In this work, dimethoxymethane was used as the base fuel to produce a non-sooting flame in a constant volume combustion vessel at 1000 K, and a density of 16.6 kg/m3. A second fuel was then added incrementally to determine an incipient soot limit. Line-of-sight extinction measurements were used as the primary diagnostic tool to determine if a correlation exists between soot and fuel properties. These data indicate that fuels with carbon double bonds are more prone to soot than the single bonded fuels. Each of the four pure additives tested began to soot at a structure-weighted available oxygen-to-carbon ratio near one. The commonly used two-color method for measuring temperature and soot concentration (KL) was used as a secondary method. A method for calibrating and analyzing the uncertainty of the temperature and KL measurements with a single color RGB digital camera was demonstrated. Images of reacting jets of different soot concentrations are shown along with an uncertainty analysis. The resulting temperature and KL maps show uneven distributions for flames of various fuels. Analysis shows that the temperature and KL values of heavily sooting fuels are primarily a result of conditions (temperature and soot concentration) within a 1—2 mm region on the surface of the jet, where a turbulent diffusion flame is present. As soot concentration decreases, the region of influence affecting the result thickens, allowing more influence from within the jet, lowering the measured temperature. Therefore, a low-sooting jet appears to have a lower temperature than a high-sooting jet. Extinction and two-color soot measurement results were compared. The two-color KL values were seen to level off at around 0.5, but continue to increase monotonically as soot increased. The broad band method is therefore not good for absolute soot measurements. Natural luminosity measurements were sensitive to the first appearance of soot, but were non-linear.

Carbonaceous deposits accumulate on the majority of the inner surfaces of internal combustion engines. The presence of these deposits is known to cause impaired engine performance. This is manifested as increased knocking, higher fuel consumption, higher emissions and other adverse effects. One of the proposed mechanisms for this behaviour is the adsorption and desorption of fuel components in the pores within the deposit. The porous nature of the deposits promotes this behaviour, altering the fuel composition and reducing the amount of fuel entering the combustion chamber. Previous research in this area was aimed at determining the porous structure of the deposits by combining experimental procedures with molecular simulations to investigate adsorption interactions with fuel components. Using a characterisation procedure regularly applied to activated carbons, a molecular model was developed that was able to provide new insights into the deposit structure. This model enabled predictions to be made for the single-component adsorption of normal heptane and iso-octane, two species commonly used as a gasoline reference fuel. Results showed significant adsorption of both species, and highlighted the impact of adsorption into the internal porous structure of the engine deposits. The aim of this thesis is to further investigate adsorption in engine deposits by expanding the studies to more complex systems. We develop a model to predict the adsorption of normal heptane, iso-octane, toluene and their mixtures in deposits of different origins and under different conditions. The study of multi-component mixtures provides insight into selectivity effects of adsorption under confinement, while at the same time bringing the systems under consideration closer to realistic multi-component mixtures that better represent fuel blends. The study also considers for the first time adsorption of aromatic species, both as a single component and in mixtures, since aromatics have a high presence in gasoline fuel. We explore the influence of molecular structure of adsorbing species, composition of the bulk mixture and temperature on the uptake and selectivity behaviour of the engine deposits. We demonstrate that under equilibrium conditions, deposits can adsorb substantial amounts of hydrocarbon species of all types. However, selectivity behaviour in engine deposits was found to be a subtle and complex property, highly sensitive to both pore size and system pressure.

Combustion phenomena are complex in theory and expensive to test, analysis techniques<br>provide handles with which we may describe them. Just as simultaneous experimental tech-<br>niques provide complementary descriptions of flame behavior, one might assume that no<br>analysis technique for any kind of flame measurement would cover the full description of<br>the flame. To this end, the search continues for complementary descriptions of engineering<br>flames that capture enough information for the engine designer to make informed decisions.<br>The kinds of flames I have encountered are high pressure transverse jet flames issuing into a<br>vitiated crossflow which is itself generated from combustion of a gaseous fuel and oxidizer.<br>Summarizing the behavior of these flames has required my understanding of experimen-<br>tal techniques such as Planar Laser Induced Fluorescence of a reaction intermediate -OH,<br>Particle Image Velocimetry of a passive tracer in the flame and OH * chemiluminescence of<br>another reaction intermediate. The analysis tools applied to these measurements must reveal<br>as much information as is laden in these measurements.<br>In this work I have also used wavelet optical flow to track flow features in the visualization<br>of combustion intermediates using OH * chemiluminescence. There are many limitations to<br>the application of this technique to engineering flames especially due to the interpretation<br>of the data as a 2-D motion field in 3-D world. The interpretation of such motion fields<br>as generated by scalar fields is one subject matter discussed in this dissertation. Some<br>inferences from the topology of the ensuing velocity field has provided insight to the behavior<br>of reacting turbulent flows which appear attached to an injector in the mean field. It gives<br>some understanding to the robustness of the attachment mechanism when such flames are<br>located near walls.

The potential of Solid Oxide Fuel Cell Gas Turbine (SOFC/GT) hybrid systems for fuel flexibility makes this technology greatly attractive for system hybridization with various fuel processing units in advanced power generation systems and/or polygeneration plants. Such hybrid technologies open up the possibility and opportunities for improvement of system reliabilities and operabilities. However, SOFC/GT hybrid systems have not yet reached their full potential in term of capitalizing on the synergistic benefits of fuel cell and gas turbine cycles. Integrating fuel cells with gas turbine and other components for transient operations increases the risk for exposure to rapid and significant changes in process dynamics and performance, which are primarily associated with fuel cell thermal management and compressor surge. This can lead to severe fuel cell failure, shaft overspeed, and gas turbine damage. Sufficient dynamic control architectures should be made to mitigate undesirable dynamic behaviours and/or system constraint violations before this technology can be commercialized. But, adequate understanding about dynamic coupling interactions between system components in the hybrid configuration is essential. Considering this critical need for system identification of SOFC/GT hybrid in fuel flexible systems, this thesis investigates the dynamic performance of SOFC/GT hybrid technology in response to fuel composition changes. Hardware-based simulations, which combined actual equipment of direct-fired recuperated gas turbine system and simulated fuel cell subsystem, are used to experimentally investigate the impacts of fuel composition changes on the SOFC/GT hybrid system, reducing potentially large inaccuracies in the dynamic study. The impacts of fuel composition in a closed loop operation using turbine speed control were first studied for the purpose of simplicity. Quantification of safe operating conditions for dynamic operations associated with carbon deposition and compressor stall and surge was done prior to the execution of experimentation. With closed loop tests, the dynamic performance of SOFC/GT hybrid technology due to a transition in gas composition could be uniquely characterized, eliminating the interactive effects of other process variables and disturbances. However, for an extensive system analysis, open loop tests (without turbine speed control) were also conducted such that potential coupling impacts exhibited by the SOFC/GT hybrid during fuel transients could be explored. Detailed characterization of SOFC/GT dynamic performance was performed to identify the interrelationship of each fuel cell variable in response to fuel composition dynamics and their contributions to operability of the system. As a result of lowering LHV content in the fuel feed, which involved a transition from coal-derived syngas to humidified methane composition in the SOFC anode, the system demonstrated a dramatic transient increase in fuel cell thermal effluent with a time scale of seconds, resulting from the conversion of fuel cell thermal energy storage into chemical energy. This transient was highly associated with the dynamics of solid and gas temperatures, heat flux, heat generation in the fuel cell due to perturbations in methane reforming, water-gas shifting, and electrochemical hydrogen oxidation. In turn, the dramatic changes in fuel cell thermal effluent resulting from the anode composition changes drove the turbine transients that caused significant cathode airflow fluctuations. This study revealed that the cathode air mass flow change was a major linking event during fuel composition changes in the SOFC/GT hybrid system. Both transients in cathode air mass flow and anode composition significantly affected the hybrid system performance. Due to significant coupling between fuel composition transitions and cathode air mass flow changes, thermal management of SOFC/GT hybrid systems might be challenging. Yet, it was suggested that modulating cathode air flow offered promise for effective dynamic control of SOFC/GT hybrid systems with fuel flexibility. / Thesis / Doctor of Philosophy (PhD)

Controlled Auto Ignition (CAI) combustion is a new combustion principle in internal combustion engines which has in recent years attracted increased attention. In CAI combustion, which combines features of spark ignition (SI) and compression ignition (CI) principles, air/fuel mixture is premixed, as in SI combustion and auto-ignited by piston compression as in CI combustion. Ignition is provided in multiple points, and thus the charge gives a simultaneous energy release. This results in uniform and simultaneous auto-ignition and chemical reaction throughout the whole charge without flame propagation. CAI combustion is controlled by the chemical kinetics of air/fuel mixture with no influence of turbulence. The CAI engine offers benefits in comparison to spark ignited and compression ignited engines in higher efficiency due to elimination of throttling losses at part and idle loads. There is a possibility to use high compression ratios since it is not knock limited, and in significant lower NOx emission (≈90%) and particle matter emission (≈50%), due to much lower combustion temperature and elimination of fuel rich zones. However, there are several disadvantages of the CAI engine that limits its practical application, such as high level of hydrocarbon and carbon monoxide emissions, high peak pressures, high rates of heat release, reduced power per displacement and difficulties in starting and controlling the engine. Controlling the operation over a wide range of loads and speeds is probably the major difficulty facing CAI engines. Controlling is actually two-components as it consists of auto-ignition phasing and controlling the rates of heat release. As CAI combustion is controlled by chemical kinetics of air/fuel mixture, the auto-ignition timing and heat release rate are determined by the charge properties such as temperature, composition and pressure. Therefore, changes in engine operational parameters or in types of fuel, results in changing of the charge properties. Hence, the auto-ignition timing and the rate of heat release. The Thesis investigates a controlled auto-ignition (CAI) combustion in internal combustion engines suitable for transport applications. The CAI engine environment is simulated by using a single-zone, homogeneous reactor model with a time variable volume according to the slider-crank relationship. The model uses detailed chemical kinetics and distributed heat transfer losses according to Woschini's correlation [1]. The fundamentals of chemical kinetics, and their relationship with combustion related problems are presented. The phenomenology and principles of auto-ignition process itself and its characteristics in CAI combustion are explained. The simulation model for representing CAI engine environment is established and calibrated with respect to the experimental data. The influences of fuel composition on the auto-ignition timing and the rate of heat release in a CAI engine are investigated. The effects of engine parameters on CAI combustion in different engine concepts fuelled with various fuels are analysed. The effects of internal gas recirculation (IEGR) in controlling the auto-ignition timing and the heat release rate in a CAI engine fuelled with different fuels are investigated. The effects of variable valve timings strategy on gas exchange process in CAI engine fuelled with commercial gasoline (95RON) are analysed.

The topic of this diploma thesis is the operational efficiency of heat sources. The work had several goals. The first was to determine the efficiency of the wood boiler according to available calculation methods and to compare the methods among them. The second was to determine the difference in the performance of the flue gas analyzer and the real calculation. Further, to determine the efficiency of a boiler firing different wood species - spruce and hornbeam based on their properties and elemental composition. Experimental measurement of various operating states of effectiveness took place in an older two-generation family house, which was also the subject of the project part. Due to lack of project documentation, it was necessary to focus and plot the object. Afterwards, the building was thermally inspected and the design of the heating system and the reconstruction of the whole heating system was carried out. The project was developed in two variants for two different heat sources - a heat pump and a solid fuel boiler for heating and water preparation. The thesis deals with the technical report, the conceptual solution of the related professions, the evaluation of the heat source variants and the project documentation.