Structures and performances of laminar impinging multiple premixed LPG-air flames

Three different imaging techniques were utilized to study the laminar, impinging, multiple, premixed liquefied petroleum gas (LPG)-air flames for simulating the premixed impinging flames of practical cooking burners. Two line-of-sight observation techniques are introduced, i.e. direct photography of a typical visible flame and the imaging of flame chemiluminescence, whereas the spatially resolved imaging is carried out by means of the OH-PLIF technique as the in situ visualization. Effects of the key parameters of heating height (H/D) and inter-port spacing (S/Do) on the flame structure and flame interaction are systematically studied and compared. The burner's performances in terms of CO emissions and thermal efficiency are experimentally studied to correlate with the flame structure. Among the three techniques, the OH-PLIF measurement is the most reliable technique to uncover the combustion situation existing in the flames. H/D is a major parameter controlling the multiple flame structure and the corresponding burner's performance, whereas S/Do has a less degree effect as compared with H/D. The optimum condition is found at H/D = 2.1 and S/Do = 1.5, where OH-PLIF profiles are well correlated with the corresponding burner's performance. This study results in better understanding of insights into the structure of the multiple premixed impinging flames, which is valuable for further work of designing an efficient, practical cooking burner.