So one of the primary jobs of the burner is to mix the gas and air in the desired manner. Despite many examples of successful burners, the most desirable manner of mixing for particular applications is not always clear at the start. GRI has been sponsoring research on turbulent flames to determine how turbulence affects the mixing of molecules, flame chemistry, the temperature and concentrations of reactants at any point in the flame, and the length of time that the reactants are kept at those conditions. Initially, sophisticated photography was used to visualize the density gradients in the flame. Later, to identify the precise locations of gas and air molecules and where combustion was really occurring, new techniques involving lasers were developed.
Lasers can identify and measure phenomena that are undetectable by the human eye.
GRI contractors have shown that, although a flame may appear smooth and homogeneous, it contains great variations in chemical activity and temperature. We now know that flames pull in air in sequential gulps, not continuously, that all of the mixing takes place in very thin regions, and that the resulting thin flamelets are continually being ignited and extinguished due to stretching by turbulence. The capabilities of these new diagnostic techniques are amazing. Not only can they create a static image, but they can actually follow dynamic processes and measure the rates of chemical reactions and fluid mixing. These measurements are creating a new view of turbulent flames that will have an impact on the reduction of pollutant emissions and the design of better combustion systems.