Reaction Kinetics Modeling of OH*, CH*, and C2* Chemiluminescence

In the combustion processes, spontaneous emission of chemiluminescence species responsible for ultra-violet and visible light is in abundance. Due to its natural occurrence, it offers an inexpensive diagnostic tool for flames and other combustion processes. It is non-intrusive in nature and gives the facility to avoid expensive laser instrumentation. In hydrocarbon oxidation most common electronically excited species are OH*, CH*, C2*, and CO2*, where * represents the electronically excited state of a given radical or molecule. In the early 1970s chemiluminescence has been identified as a marker for heat release, reaction zone, and equivalence ratio, thereby providing a relatively easy diagnostics alternative for online measurement of these features in practical combustion applications. However, the quantitative relationship between chemiluminescence, heat release, and equivalence ratio is mostly unknown except for a few correlations available in literature over small range of conditions. Therefore a reaction kinetic model predicting these species is necessary for the fundamental understanding of the chemiluminescence. This mechanism then can be provided for predicting excited species in simulations of various combustion devices. A detailed reaction mechanism of chemiluminescence is not well studied. Therefore, the objective of this work is to develop a reaction mechanism of chemiluminescent species which can predict their concentrations in shock-tube and one-dimensional laminar flame experiments. The mechanism developed in this thesis is validated against various experimental conditions in shock-tube experiments where it reproduces the ignition delay time very well. In addition, the species profiles which provide a more stringent test on the mechanism validation are calculated to reproduce the measured excited species concentrations in laminar premixed and non-premixed flames. The comparison proves accuracy of the mechanism. The mechanism presented provides therefore a first step to quantitative understanding of the excited species and can be further used in the simulation of practical combustion systems