Performance evaluation of novel surface flame self-aspirated porous radiant burners for cooking applications

Abstract

Porous radiant burners (PRBs) are based on the principle of porous media combustion (PMC) in which both combustion and stabilization of the flame take place towards the end of combustion zone (CZ). It has lot of advantages over conventional free flame burners. The porous matrix has high thermal conductivity and high emissivity. Hence, contributions to conduction, convection and radiation in the PMC are significant. This paper presents experimental results on the thermal and emission performance of newly developed, bi-layered, self-aspirated porous radiant surface flame burners used in cooking applications. It comprises firebrick material in the CZ and steel balls in the preheating zone (PZ). Performance of this burner is compared to that of a conventional cooking burner (CB) within the operating range of 0.5–2 kW. The effect of burner geometry (one is circular and the other one is square in cross section) on the thermal performance and emission using liquefied petroleum gas (LPG) as the fuel is also studied and their thermal performances are compared to the conventional ones. The experimental results have revealed that the thermal efficiencies of circular and square PRBs are much higher than those of the conventional burner. The maximum thermal efficiency of the self-aspirated circular porous radiant burner (SCPRB) is found to be 71.78% at the flow rate (V) of 2.0 m/s with a porosity of 85%, whereas the thermal efficiency obtained from self-aspirated square porous radiant burner (SSPRB) is marginally less than that of SCPRB at the corresponding flow rate and porosity. The emission levels are much lower in these novel PRBs as compared with the conventional burner and these values are well below the World Health Organization (WHO) standard. The NOx emission values corresponding to the optimum velocity of 2.0 m/s are 87 ppm for CB, and 24 and 27 ppm, respectively, for SCPRB and SSPRB. CO emission values are 32, 33 and 155 ppm for SCPRB, SSPRB and CB, respectively, corresponding to the optimum velocity of flow.