Effects of the cone angle on the stability of turbulent nonpremixed flames downstream of a conical bluff body

Abstract

The effects of a stabilizer and the annular co-flow air speed on turbulent nonpremixed methane flames stabilized downstream of a conical bluff body were investigated. Four bluff body variants were designed by changing the outer diameter of a conically shaped object. The co-flow velocity was varied from zero to 7.4 m/s, while the fuel velocity was kept constant at 15 m/s. Radial distributions of temperature and velocity were measured in detail in the recirculation zone at vertical locations of 0.5D, 1D and 1.5D. Measurements also included the CO2, CO, NOx and O2 emissions at points downstream of the recirculation region. Flames were visualized under 20 different conditions, revealing various modes of combustion. The results evidenced that not only the co-flow velocity but also the bluff body diameter play important roles in the structure of the recirculation zone and, hence, the flame behavior.