Effect of surface emissivity on the radiative efficiency of divergent porous burner

A two-dimensional numerical study is performed on a divergent radiant porous burner to study the surface emissivity (?r) on the radiative efficiency (?) and uniform distribution of heating temperature. It is shown that the ?r has a significant impact on both the ? and uniformity distribution of heating temperature over the whole investigation range for inlet velocity of 0.4 m/s- 7.5 m/s and equivalence ratio range of 0.45-1.0. The ? is always increased with the ?r. For example, the ? at an equivalence ratio of 0.75 and an inlet velocity of 1.8 m/s is increased from 0.0817 to 0.155 with ?r. Meanwhile, a significant expansion of the upper limit of the modeled burner is validated, compared to the conventional one. The increased ?r leads to the slightly narrower stability limit. Furthermore, uniform heating temperature is predicted over the whole investigation. The maximum Root Mean Square of the heating temperature is in the order of 30 K. The divergent two-section porous burner achieves wider stability limits with comparable ? compared to the conventional one.