Bio-Fuels

Bio-fuels offer an attractive solution to the current  constraints imposed by petroleum based hydrocarbon fuels. It may however be noted that biofuels are noticeably different in both physical and chemical properties compared to their hydrocarbon counterparts. One of the distinguishing features is the presence of fuel-bound oxygen. The different chemical structure can significantly alter autoigntion properties. It is of practical interest to clearly understand the role of these differences  so that the suitability  of biofuels to existing devices can be assessed in a logical manner. Also of great fundamental interest is the study of fuel-blends, whose constituents are both traditional  hydrocarbon fuels as well as bio-fuels. The use of bio-fuels is still faced with the challenges of efficient and clean combustion, which requires research attention. As such, fundamental investigations using well charac- terized laboratory-scale apparatus should be the logical starting point.   The acquired knowledge will prove beneficial in real world applications. A similar argument is valid for non-petroleum derived liquid hydrocarbon fuels. The feedstock for the production of such fuel is natural gas, derived typically from coal, or biomass. It is also equally important that the existing fossil fuel resources be utilized in an optimal fashion.

Hydrocarbon Fuels

Petroleum derived liquid hydrocarbon  fuels are unique in their ability to provide an extremely high energy density. It is desirable to have efficient and clean combustion of hydrocarbon fuels. The first step in this direction is to develop a proper scientific understanding of the combustion chemistry of hydrocarbons. Emerging  engine concepts such as the Homogeneous Charge Compression Ignition (HCCI) Engine hold the promise of high efficiency and low emissions. The HCCI process is governed mainly by the combustion kinetics of the fuel. HCCI engine operation requires a clear understanding of the autoignition chemistry of the fuel. The flame propagation characteristics are of importance in the spark ignition mode.   The logical starting point for studying such combustion response is a pure hydrocarbon component. Starting from pure components one can construct complex surrogates that emulate the combustion properties of real fuels.

Conventional Hydrocarbon Fuels

An important task in combustion research is to predict and control the combustion behaviour of practical combustors using real fuels such as gasoline, diesel and kerosene.  As a part of my research, I have investigated the flame and ignition delay response of kerosene type fuels such as Jet-A and JP-8. The studies have explored both the high temperature combustion as well as the low-to-intermediate temperature combustion regime. A wide variation of the thermodynamic operating conditions such as pressure and temperature were explored. The specific purpose of these investigations was to develop an understanding of the various combustion phenomena  such as laminar flame speed, stretch induced extinction, and autoignition. These concepts have significance in engine research. I have conducted extensive spark-ignition engine studies to characterize the effect of operating parameters on engine-out emissions using conventional gasoline, as a part of my M.S. thesis.

Alternative Hydrocarbon Fuels

A natural extension of the study on liquid hydrocarbon fuel combustion is in the area of alternative fuels. The use of hydrocarbon fuels obtained from non-petroleum  feedstock, such as coal, are likely to undergo significant growth in the near future. Such fuels offer the possibility of a seamless transition in hydrocarbon fuel usage patterns, with minimal modification to the existing infrastructure.   How- ever, the combustion chemistry of alternative liquid fuels is significantly different from the conventional liquid fuels. The difference owes its origins to the chemical composition of the fuel. Experimental investigations to quantify the differences, with respect to autoignition trends, between conventional and alternative jet fuels have been conducted. Additionally, studies on the comparative flame propagation characteristics were also conducted.