Coal Water Slurry Combustion in a Simulated Diesel Engine Cylinder

Uncertainty about the reliability of the imported oil supply to the United States has led to research into alternative sources for domestic energy needs. Because of the relative abundance of coal reserves in the United States, much of this research has focused on developing methods of using coal for fuel where oil products have traditionally been used. This thesis reports results of a study to determine the suitability of using coal water slurry fuels in diesel engine operation. The primary focus of this study was to determine if the ignition and combustion characteristics of a coal water slurry are comparable to those of diesel fuel and are suitable for use in a diesel engine. This testing was done using a Parr combustion bomb modified to allow injection of a test fuel and recording of the bomb pressure. Prior to injecting the test fuel, the combustion bomb was brought to the high temperature and high pressure conditions typical of a diesel engine cylinder by combustion of a hydrogen, oxygen, and nitrogen gas mixture. Two types of coal water slurry fuels were tested and a standard number two diesel fuel was used for baseline testing. One of the slurry fuels was produced from a low rank lignite coal, while the other was produced from a higher rank bituminous coal. Besides the slurry type, the primary test variables in this study were bomb pressure and temperature at the time of fuel injection. The pressures and temperatures ranged from 400 to 800 psia and 900 to 1300°K, respectively. The time required for ignition and combustion of the test fuel were measured. It was found that increasing the bomb injection temperature decreased the time required to ignite and burn the test fuel. This effect was more pronounced when using the less volatile bituminous coal slurry. The lignite slurry ignited and burned at about the same rate as did the baseline diesel fuel, while the bituminous coal slurry took slightly longer to ignite and burn. Changing the bomb injection pressure did not have a significant effect