The Role of Reactant Mixedness, Strain Rate, and Length
Scale on Premixed Combustor Performance
S. Samuelson, Principal Investigator;
J.C. LaRue, Co-investigator;
S. Vilayanur, D.W.
Guillaume,
Lean premixed combustion provides a means to reduce pollutant formation and increase combustion efficiency for natural gas fired utility applications. The "fuel-air mixture", however, is rarely uniform in space and time. The variability of the mixture is characterized by the term "mixedness" and a major question is the extent of pre-mixing is necessary to minimize pollutants. Furthermore, another question is how to control and predict the degree of mixedness. Although turbulence properties such as length scales and strain rate are known to effect mixedness, the exact relationships are unknown. This paper presents an approach that is being used to determine the relationship between length scales, strain rate and mixedness. The facilities used in this premixing study are amenable to parametric variation of length scale, strain rate and reactant mixedness. They are used with a controlled reactor and a research combustor operated at atmospheric and practical pressures. Methods of defining and measuring mixedness are discussed. Critical emphasis is placed on minimizing pollutant information without sacrificing efficiency while maintaining a wide range of stable operation.