The Effect of Engine Deposit Layers on Hydrocarbon Emissions from Closed Vessel Combustion

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Abstract
-The effects of engine deposit layers on the product gas emissions from combustion bombs manufactured from engine combustion chambers were studied for various fuel-deposit systems. Nine fuels (methane, ethane, propane, n-butane, n-pentane, n-hexane, benzene, n-heptane and iso-octane) were tested in combination with two in-situ engine deposit layers-one thin (0.0017 cm) and one thick (∼0.05-0.1 cm). Gas samples from the reactors were analyzed by gas chromatography. For the thin deposit, the results show that the principal exhaust effluent is unburnt fuel. Additionally, as the solubility of the fuel is increased, the HC emission increases in direct proportion to the change in relative solubility and the absolute HC level can be estimated from the deposit composition and estimated fuel solubility. For the thick deposit, the results show that the principal exhaust effluent is also unburnt fuel, that the exhaust HC level increases with fuel solubility and that a small fraction of the HC emission may arise from the porous structure of the deposit. Additionally, however, they show that the exhaust HC emission decreases as the loading and sampling times of the reactor are reduced and is proportional to the square root of the loading time, suggesting that time-dependent loading processes will be important at the proportionally shorter time scales of engines even at the elevated temperature found in typical engine combustion chambers.