A concentric flow conical nozzle burner for highly stabilized partially premixed flames

A new burner design is presented in this work for highly stabilized partially premixed flames using gaseous fuel. The partially premixed flow is created in a concentric flow tube and the flames are stabilized by a relatively large diverging conical nozzle. The concentric flow conical nozzle burner (CFCN) creates highly stabilized flames at high Reynolds number, up to 60000. Three versions of the burner have been investigated and a maximum load of about 250 kW with 20 mm diameter nozzle has been achieved in partially premixed flame. Higher load is expected for larger burner size. The stability characteristics of the CFCN burner show that it is suitable for industrial applications. The burner turndown ratio is between 15 and 20. Fundamental research studies and modeling of the flames in CFCN are feasible because of the simple flow geometry of the burner. Therefore, four flames have been selected in the present work for detailed thermal reaction zone structure investigation and OH radical distribution using simultaneous two-dimensional imaging of Rayleigh scattering and Laser Induced Predissociation Fluorescence (LIPF). The reaction zone structure is relatively thin and may be classified in the thin reaction zones regime. The OH signal correlates well with temperature at the reaction zone. More fine structure in the preheat zone can be observed from the temperature images as compared with those of the OH radical. Stable flame structure with continuous reaction zone at high stretch conditions has been observed.