The Chemistry of Flames

Abstract

Combustion scientists are primarily concerned with the fuels most often burned as energy sources (coal, petroleum products, and natural gas), with the goal of learning to burn them as efficiently, intensely, and cleanly as possible. Discovering those slight rearrangements of chemical bonds that together account for the net chemical transformation is the key to understanding how combustion proceeds. Once these reactions have been defined, the chemist can determine the rate coefficient of each reaction as a function of temperature and assemble the information into flame models. The computer programs that use these models to predict experimental results combine two sets of equations describing (1) the diffusive and reactive rates of change in concentration of all the molecules in the flame and (2) the flow of the reacting gases. Although the details of hydrocarbon-flame models are still disputed, many of their general features are clear and the basic reactions well-known; computer models for methane combustion already include over 100 elementary reactions. Experimental data on NO/sub x/ formation have led to ingenious methods for purifying postcombustion gases. Currently, the two most actively studied processes in combustion chemistry are the formation and oxidation of soot. The synthetic fuels most likely to replace fossilmore » ones will probably contain less hydrogen, making them more prone to produce soot. How to understand and overcome this problem will be the next challenge for combustion chemists and engineers.« less