Effect of N-2 dilution and preheat temperature on combustion dynamics of syngas in a reverse-flow combustor

摘要

The present study investigates the combustion dynamics of low-calorific value syngas in the reverse-flow configuration at P = 1 atm using OH* chemiluminescence (5 kHz), noise (50 kHz), and emissions (NOx and CO) measurements. The combustion dynamics have been investigated as a function of the global equivalence ratio (0.32-0.89), percentage O-2 in the coflow (7.6-21%), and the oxidizer preheat temperature (similar to 400-800 K). The variation of these parameters resulted in different operating conditions such as conventional, ultra-lean, transition, and MILD combustion modes. For all the cases, autoignition kernels were observed arid appear to be a possible mode of flame stabilization - highlighting the role of H-2 in reducing the ignition delay. The combustion chamber demonstrated stable operation over the range of equivalence ratio and percentage O-2 investigated, with the conventional mode displaying the highest SPL and fluctuations in the reaction zone (OH*). The most stable operation was obtained for the MILD case where the SPL decreased by similar to 6 dB caused by a suppression of the high-frequency (> 800 Hz) longitudinal modes. However, the operation of the combustion chamber became unstable as the oxidizer preheat temperature decreased from 603-547 K due to the emergence of very high-frequency (similar to 9-15 kHz) oscillations.