Chemiluminescence-based sensing of flame stoichiometry: Influence of the measurement method

Lean combustion presents many advantages in terms of low NOx emissions, but it has the problems of being close to the lean blowout limit and more susceptible to instabilities and therefore, measuring equivalence ratio in real time with high accuracy is an important objective. Previous works have analyzed the chemiluminescence emission from the flame and its relationship with flame properties by using different measurement methods that led to different kind of results. Therefore, this study has been focused on the analysis of the influence of the measurement method on the chemiluminescence vs. equivalence ratio curves and the experimental results confirmed the existence of a significant influence. In addition, theoretical calculations seem to reveal that the change in the trends observed for different equivalence ratio ranges may be associated to the existence of different combustion regimes, what may have consequences regarding the applicability of this sensing method for very lean flames.