Quantitative Temperature Measurement of High Pressure CH$_{4}$/O$_{2}$/N$_{2}$ Laminar Flames Using Laser Induced Thermal Grating Spectroscopy (LITGS)

Laser diagnostics for quantitative measurements of temperature are important in high pressure and high temperature environments. In this study, Laser Induced Thermal Grating Spectroscopy (LITGS) is employed for oxygen enriched CH$_{4}$/O$_{2}$/N$_{2}$ laminar flames at elevated pressure. The wavelength of the pump beam was set for OH excitation. LITGS is a promising laser diagnostic for quantitative measurements of temperature at high pressure because the magnitude of LITGS signal increases with pressure due to higher quench rates and stronger density perturbations in more dense mixtures. As a result, LITGS signal can be successfully acquired at 0.5 MPa for various equivalence ratios. The derived temperature was close to the adiabatic flame temperatures for each condition and the maximum derived temperature was higher than 2600 K. Therefore, LITGS is also a promising diagnostic for quantitative temperature measurements in high temperature flames, such as rocket motors.