In Chapter 2 we introduced the principles of the chemical kinetics of gas-phase reactions. In particular, we discussed the fundamental dependence of reaction rates on temperature, pressure, and reactant concentrations. We studied the concept of multistep reactions, and then categorized the reaction mechanisms and showed how they can affect the reaction rate in qualitatively different manners.

In this chapter, we discuss the oxidation mechanisms of specific fuel systems involving hydrogen, carbon monoxide, and various hydrocarbons. The formation of pollutants will also be covered. In particular, the reaction pathways leading to fuel consumption, the formation and destruction of intermediate species, and the final product formation are discussed in a qualitative manner. We shall see that numerous elementary chemical reactions are involved in the conversion of reactants to products, and that even for a given fuel these reactions often play different roles in different combustion environments. The intricate paths followed by hydrocarbon oxidation illustrate the complexity of chemical kinetics in combustion. Nevertheless, in spite of such apparent complexity, we shall also show that there appears to be only a finite number of reactions that exert significant influence in a combustion process, providing the possibility that the reaction mechanisms of fuel oxidation can be largely understood.