Numerical investigation of the effect of the slit profile on the combustion characteristics of a micro-combustor with a centrally slotted bluff body

Abstract

Numerical studies are performed on a micro-combustor with a centrally slotted bluff body by varying the slit profile. The slit profiles is modified to alter the velocity of the fluid stream through the slit. Three different slit profiles are considered viz., straight, converging and diverging slits. The combustion characteristics are evaluated in terms of the hydrogen combustion efficiency, combustion progress parameter and blow-off limits. The converging slit is found to exhibit better combustion efficiency compared to the other two slit profiles. The converging slit resulted in the formation of a secondary recirculation zone near the rear end of the bluff body. A novel approach towards understanding the flame splitting which finally results in blow-off is presented. Total viscosity is considered as the means to quantify the shear stress which is responsible for the flame stretching and eventual flame splitting. It is observed that the flame blows off at smaller inlet velocities in the combustor with the converging slit compared to the other slit profiles.