Implementation of Local Chemiluminescence Method on a Premixed Laminar Propane/Air Flame

In this work, the local chemiluminescent intensities of OH* and CH* of a premixed laminar Propane/air bunsen burner flame have been measured. To achieve high spatial resolution a multi-color integrated Cassegrain receiving optics (MICRO) is developed. The Cassegrain-based optical system consists of two mirrors so it is free of chromatic aberration. The design of the optical system is optimized to minimize other kinds of aberration, especially spherical aberration. The optimization process is done in Zemax program. The effective light collection volume of the MICRO system is estimated to be a cylinder with 58 micrometers in diameter and 3.4 millimeters in depth. To measure chemiluminescent emissions of OH* and CH* a photodetection unit is developed. The photodetection unit has the ability to separate CH* emission which its maximum is in wavelength of 430.5 nanometers and OH* emission which its maximum is in wavelength of 310.4 nanometers through a dichroic filter. Photomultiplier tubes (PMTs) are used as light detectors and the output voltage is measured through a data acquisition system. The Temporal resolution of the data acquisition system is 2 microseconds. The effect of the equivalence ratio on the OH*/CH* signal is investigated and the calibration curve is extracted between the equivalence ratio and the OH*/CH* signal in a certain range of equivalence ratios for Propane/air combustion. The effort in this work is put into the design of the Cassegrain-based optical system and the process of the design is discussed in detail.