Effects of Natural Gas Constituents on Engine Performance, Emissions, and Combustion in Compressed Natural Gas-Assisted Diesel Combustion

The current state of transportation in the United States is unsustainable in that it is based on fossil fuels, which are limited in quantity and are imported from foreign countries. Recent exploitations of the shale gas in North America has provided an abundant supply of relatively easily processed natural gas. In addition to being abundant, natural gas burns cleanly in engines as it is a gaseous fuel similar to gasoline. Therefore, to help move the transportation sector of the Unites States to a more sustainable future, it is possible to supplement diesel combustion with natural gas. The combustion characteristics of natural gas along with precise control of combustion with the diesel pilot provides an opportunity for investigations into low temperature combustion. To aid in achieving low temperature combustion, it is often advantageous to employ exhaust gas recirculation. As part of a multi-discipline effort at the University of Kansas to study sustainable biodiesel, a single-cylinder engine has been outfitted with state of the art upgrades and instrumentation, which provides a unique opportunity to investigate compressed natural gas assisted diesel combustion, or dual-fuel. This work uses the advanced engine test cell to investigate the effects of the constituents within natural gas on the performance and emissions of the dual-fuel operation. In order to allow for future experimental opportunities with low temperature combustion, the existing manually-operated exhaust gas recirculation system was upgraded to a dynamic, fully-electronic system. This upgrade, which is presented in detail, provides the final piece necessary for the single cylinder test cell to examine "advanced" engine operation, such as low temperature combustion. Finally, to aid in the examination of the large amount of data gathered in the test cell, a tutorial for an in-house developed post-processing program is included.