Flame Speeds

THE GLOBAL CONSUMPTION SPEEDS OF PREMIXED LARGE-HYDROCARBON FUEL/AIR TURBULENT BUNSEN FLAME

Pre-mixed, turbulent, vaporized jet-fuel air Bunsen flame shot with 1/8000th of a second shutter speed

In 2014 the United States consumed 18.49 million barrels of oil a day, 70 percent of which was used in transportation. Reducing this dependence on fossil fuel technologies is critical to the nation's security, economic stability, and environmental stewardship. Oil is a politically volatile, increasingly scarce resource that releases greenhouse gases when combusted and, as a result, is not sustainable at its current rate of consumption.

Reactions in internal combustion and gas turbine engines operate at elevated temperatures and pressures, and are primarily driven by turbulent premixed and partially premixed combustion of hydrocarbon fuels. Current estimates suggest there is nearly one passenger car per individual living in the United States. This statistic excludes delivery, public transit, and emergency vehicles as well as air and water transport vehicles. These vehicles use large-hydrocarbon liquid fuels such as gasoline, diesel, and jet fuel and will for the foreseeable future.

The turbulent flame speed is the rate at which a flame front propagates in an unburned turbulent fuel-air mixture. This measure is important to the fidelity of combustion models used in engine design and provides a means of directly analyzing and comparing fuels. However, turbulent flame speeds for most large-hydrocarbon fuels are not known. Thus, an accurate understanding of turbulent flame speeds is required to help overcome current challenges present in engine design.

An improved understanding of the turbulent combustion of large-hydrocarbon fuels used in transportation technologies is currently needed. This is motivated by the significance of the turbulent flame speeds in evaluating combustion models, and the ubiquity of large-hydrocarbon fuels. In my thesis I investigate the effects of local turbulent fluctuation on global combustion phenomenon such as the turbulent flame speed for these large-hydrocarbon fuels.