  Turbulent reacting flows occur in a variety of engineering applications such
as chemical reactors and power generating equipment (gas turbines and internal
combustion engines). Turbulent reacting flows are characterized by two main
timescales, namely, flow timescales and chemical (or reaction) timescales.
Understanding the relative timescales of flow and reaction kinetics plays an
important role, not only in the choice of models required for the accurate
simulation of these devices but also their design/optimization studies. There
are several definitions of chemical timescales, which can largely be classified
as algebraic or eigenvalue-based methods. The computational complexity (and
hence cost) depends on the method of evaluation of the chemical timescales and
size of the chemical reaction mechanism. The computational cost and robustness
of the methodology of evaluating the reaction times scales is an important
consideration in large-scale multi-dimensional simulations using detailed
chemical mechanisms. In this work, we present a computational efficient and
robust methodology to evaluate chemical timescales based on the algebraic
method. Comparison of this novel methodology with other traditional methods is
presented for a range of fuel-air mixtures, pressures and temperatures
conditions. Additionally, chemical timescales are also presented for fuel-air
mixtures at conditions of relevance to power generating equipment. The proposed
method showed the same temporal characteristics as the eigenvalue-based methods
with no additional computational cost for all the 1cases studied. The proposed
method thus has the potential for use with multidimensional turbulent reacting
flow simulations which require the computation of the Damkohler number.
