An investigation into the origin, measurement and application of chemiluminescent light emissions from premixed flames

Abstract

The chemiluminescent species CH* and OH* are studied in premixed methane combustion to investigate the possible application of their light emissions in gas turbine combustion monitoring systems. The interpretation of integrated and local chemiluminescence measurements are shown to give important qualitative insights into the burning process. The formation path of OH* chemiluminescence is clarified and an accurate chemical kinetic model predicting OH* chemiluminescence emission is developed using GRIMECH 3.0 as a starting point for methane oxidation. CH* chemiluminescence is also modeled but difficulties in obtaining quenching data make the modeling efforts somewhat less successful than that for OH* chemiluminescence. Two combustion models are developed. The first is a semi-empirical model for a Bunsen type flame. The second is a 1-D model for a ceramic honeycomb flat-flame burner using the full chemical kinetics description of the conversion from fuel to products along with a detailed energy equation, accounting for the radiation energy exchange between hot gases and the honeycomb burner ceramic. The results of the modeling calculations show that OH* is superior to CH* chemiluminescence in terms of indicating heat-release rate. The formation of the ratio between CH* and OH* chemiluminescence is shown to be an accurate indicator of equivalence ratio.