Hydrogen is an energy carrier that can be used to create electricity via an electrochemical device called a fuel cell. Thus, many American scientists and policy makers consider hydrogen to be the fuel of the future because it can be produced without depending on petroleum imports. The research described in this dissertation investigates a thermodynamic model to predict results from and to compare methods of producing hydrogen. Hydrogen generation will be explored through modeling two types of processes: steam reforming and supersonic pyrolysis. Results of the model predict that although methanol is a widely used fuel for steam reforming, dimethyl ether can produce the same amount of hydrogen when it is reformed while consuming less energy. Supersonic pyrolysis is a well known process but has only recently been considered as a route to produce hydrogen. The model shows that pyrolysis could be a good alternative to steam reforming. Pyrolysis of fuels occurs at higher temperatures than does steam reforming and hence a higher energy input is necessary, however, hydrogen can be produced ten times faster making pyrolysis a more powerful method to produce hydrogen.

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The second law analysis is a powerful tool for assessing the performance of engines and has been employed for few decades now. Turbocharged diesel engines have been explored in much detail with the help of second law analyses. There is also a need to examine the turbocharged spark-ignition engines in greater detail using second law analyses as they are gaining popularity in high performance and conventional automobiles as well. A thermodynamic simulation was developed in order to investigate the effects of turbocharging on spark-ignition engines from second law perspective. The exergy values associated with the components of the turbocharger along with the engine components were quantified as a percentage of fuel exergy. The exergy balance values indicated that turbocharger does not add considerably to the overall irreversibilities and combustion irreversibility is still the major source of exergy destruction. A comprehensive parametric investigation was also performed to investigate the effects of compression ratio, intercooler effectiveness, etc. for the turbocharged spark-ignition engine over the entire load and speed range. The simulation studies helped in understanding the behavior of turbocharged sparkignition engine with these parameters. A simulation study was also performed to compare the turbocharged engine with the naturally aspirated spark-ignition engine. This study examined the engines for operating parameters like bmep and bsfc over the entire speed range and revealed that turbocharging offers higher bmep and lower bsfc values for most of the operating range. In an additional study, these engines were analyzed for the brake thermal efficiency values at part load. The results indicated that turbocharging offers marginally higher brake thermal efficiency at part loads.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009. / Title from title screen (site viewed February 25, 2010). PDF text: 201 p. : col. ill. ; 4 Mb. UMI publication number: AAT 3386550. Includes bibliographical references. Also available in microfilm and microfiche formats.

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