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The effect of fuel additives in a natural gas and gasoline engine




Falloon, Thomas, author
Marchese, Anthony, advisor
Olsen, Daniel, advisor
Reardon, Kenneth, committee member

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Fuel additives are used worldwide for a variety of applications including increasing fuel efficiency, decreasing emissions, decreasing knock propensity and/or modifying storage/handling properties. Because of the high percentage of global fossil fuel consumption attributed to internal combustion engines, fuel additives that increase the efficiency of fossil fuel powered internal combustion engines can greatly impact global fossil fuel consumption and greenhouse gas emissions. In this study, the effect of various fuel additives on spark ignited natural gas and gasoline internal combustion engines was examined. The natural gas work focused primarily on using fuel additives to extend the lean limit, while the gasoline additives work focused on lean limit extension, decreased knock propensity and increased power. Experiments were performed in using a constant speed, single cylinder, variable compression ratio Cooperative Fuel Research (CFR) engine, which has the capability to operate with both gaseous and liquid fuels. The gaseous fuel system used compressed air to simulate a turbocharged engine, while the liquid fuel system used a naturally aspirated carburetor. In-cylinder pressure data were acquired using a high-speed piezoelectric pressure transducer, which is used to calculate indicated power, peak pressure and to quantify engine knock. In this study, four natural gas and three gasoline additives were considered. For the natural gas fuel additives, the primary hypothesis for the fuel additives was that the lean limit would be decreased with the addition of the additives. By holding the power of the engine constant and decreasing the equivalence ratio, this hypothesis was tested and it was concluded that the additives had a negative impact on the lean limit. For the gasoline additives, the hypothesis was that the additives would either increase engine power, decrease the knock propensity (i.e. increase the octane number), or decrease the lean limit. It was found that one of the additives increased engine efficiency slightly and decreased the knock propensity, while the other two gasoline additives had negative impacts on both metrics. One of the gasoline additives appeared to slightly extend the lean limit, but further testing will be required to confirm this result.


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