Operability Study With Spatial Resolved Temperature and Water Molar Concentration Measurements of a New Pressurised Optical Modular Staged Combustor

A new optical modular staged combustor has been developed to facilitate the study of the staged combustion of alternative fuels, both liquid and gaseous, at elevated inlet pressures and temperatures. Initial testing to characterize the combustor was carried out at pressures of up to 6 bara, for both premixed and non-premixed methane/air swirling flames with a combustor inlet temperature of 450 K. Exhaust gas analysis together with OH* and CH* chemiluminescence was used to evaluate the operability of the combustor and the quenching effect of the secondary air flow for a range of primary and global equivalence ratios. Laser Induced Grating Spectroscopy (LIGS) was used to obtain instantaneous local temperatures of the mixture across the secondary air mixing zone. A previously developed analytic approach was used to extract temperature from the measured signal frequencies within the primary flame brush and secondary mixing region, where both burnt and unburnt gases were present. The development of such modular apparatus specifically to allow for the application of novel optical techniques, such as LIGS, enables the future evaluation of different combustor architectures for unconventional fuels. Additionally, this work further demonstrates the development of the LIGS technique for obtaining measurements within complex high-pressure, turbulent swirling flames.