Effects of Equivalence Ratio and Iodine Number on NOx Emissions from the Flames of Biofuels and Hydrocarbons

Abstract

Increased energy consumption in the United States has led to a demand for the development of new bio-derived fuels. As biofuels are used more frequently in diesel and gasoline engines it has become increasingly important to test the emissions resulting from the combustion of these fuels. This study was motivated by the need to test these fuels, predict their combustion and pollutant formation potential when used in engines, and provide quick feedback to fuel researchers on the combustion characteristics.

This dissertation presents a technique that characterizes the combustion properties of liquid fuels based on the chemistry of the fuel alone. This includes the development of the method for the rapid characterization of combustion properties, such as emission index and flame radiation. Using this method provides a way of predicting the combustion behavior of the fuels without the use of an engine for existing hydrocarbon fuels and newly developed fuels such as biodiesel. This technique in comparison to engine testing studies requires only small amounts of fuel, time, and provides a method to compare fuels on a normalized basis.

Increased pollutant emission NO was observed when burning biodiesel when compared to petroleum based diesel. This same trend has also been documented for various diesel engine studies; however, reasons for this increase have not been determined. Using the developed experimental method the cause of the formation of NO in diesel and biodiesel fuels was then studied. Equivalence ratio and iodine number were varied and their effect on the formation of NO studied for five different fuels: canola methyl ester, soy methyl ester, diesel, methyl stearate, and normal dodecane fuels.