Abstract

Measurement of the temperature field is crucial to understanding combustion in practical devices. Imaging of laser-induced fluorescence (LIF) from NO molecules seeded into the flow is an attractive method to determine the temperature field.¹ If the seeded NO does not react or become diluted in the flow, accurate temperature measurements can be made from single line excitation with careful consideration of energy transfer and quenching collisions, overlap of laser and transition bandwidth, and detector bandwidth.² However, NO reacts in the flame front of hydrocarbon flames via reburning phenomena. We investigate the accuracy of LIF measurements of gas temperature using NO seeded into a premixed, laminar, low-pressure methane/air flame. The NO LIF temperature measurements are compared with temperatures determined from rotational distributions measured with LIF using OH as a function of height above the burner. Using the OH temperature profile, the chemical composition of the flame is predicted from a model of the combustion chemistry. This model predicts the amount of NO as a function of reaction time (height above the burner) including reburning in the flame front, the dilution from the combustion products, and the axial transport. The predicted major species concentrations are used to calculate the rate for NO(A) collisional quenching which are compared to measured quenching rates. In the flame front CH temperature measurements using LIF from A-X and B-X electronic transitions are compared to the OH results.

© 1996 Optical Society of America