Development of Equivalence Ratio Measurement Model of Premixed Methane Flames Using Hyperspectral Imaging of C₂* and CH* Chemiluminescence and Random Forest Algorithm

The C-2*/CH* model is often used to measure the equivalence ratio of combustion. But only the band of C-2*(0,0) at 516.5 nm of the C-2* swan band system was employed as the input of the C-2*/CH* model for equivalence ratio measurement. The relations of other components of the C-2 swan band system with flame equivalence ratios and their impact on this equivalence ratio measurement are unreported. In this study, the visible emission spectrum of premixed methane flame, ranging from 425 to 700 nm, was measured/obtained by a hyperspectral imaging system under equivalence ratios from 0.72 to 1.52. The influence of the C-2* swan bands on the C-2*/CH* model was analyzed, and the intrinsic characteristics of the C-2* swan bands were found. After that, a more sensitive soft measurement model for equivalence ratio measurement based on the ratio of C-2*(0,0)/C-2*(2,0) was proposed. The monotonicity and stability of the proposed model were discussed. At last, the proposed model was further validated by the random forest (RF) algorithm.