Strategy to diagnose ultra-lean (φ＜ 0.6) premixed flames by acetone-OH simultaneous PLIF with one-laser and one-detector combination

摘要

A strategy to diagnose ultra-lean flames utilizing the "acetone-OH simultaneous PLIF" concept via a one-laser and one-detector combination system is presented. The main aim of the present work is to overcome difficulties encountered in our previous studies; namely, that the seeding amount of acetone used for visualization purposes must be sufficiently small in order to avoid its effect on flame structure (at least ＜5% of fuel), while clear imaging also must be accomplished under such conditions. For this purpose, several important revisions have been made: (1) the 266-nm excitation line has been added to improve the fluorescence from acetone, (2) a dual-peak band-pass filter has been introduced instead of conventional blue filter and (3) controllability of fine acetone seeding has been improved. The effects of these changes on flame imaging are also investigated. Clear visualization of the flame zone of a very lean premixed flame, of which the limiting equivalence ratio is below 0.6, has been successfully achieved for the first time with one-laser and one-detector system. The time-dependent, near-extinction flame behavior is also clearly imaged, suggesting that this method could utilize to investigate the flame extinction study.