Study on flow resistance characteristics of SiC foam ceramics

Porous media combustion has significant advantages of high thermal efficiency and low pollution emissions. However, the flow state in the porous media will affect the reaction rate. In order to increase the rate of chemical reactions, the fluid flow resistance in the porous media must be reduced. The pressure drop test of SiC foam ceramics was carried out. By changing the pore density of the experimental materials, the pressure drop characteristics of SiC foam ceramic are tested and analyzed. Based on the classical Ergun equation, a semi-empirical formula for calculating the pressure drop gradient of SiC foam ceramics with the airflow velocity is proposed. The two constants in the formula are calculated by measurement, and the applicability of the formula is verified. This formula can quickly analyze the pressure drop characteristics of SiC foam ceramic materials. The accurate measurement of pressure drop is helpful to determine the rated pressure of the head of foam ceramic burner and reduce the investment of front-end fans in industrial burners.

A Numerical Investigation of the Effects of Structural Properties on the Performance of a Two-Section Porous Medium Burner

Porous media combustion is a feasible approach to tackle challenges encountered in free flame burners by offering advantages such as lower pollutant emissions, higher flammability limits and better flame stabilization. This study computationally investigated the premixed combustion of a methane/air mixture in a porous medium burner. The porous medium consisted of two sections: The upstream one was called the preheating section; The downstream one was called the combustion section. For methane oxidation, GRI 3 mechanism including 53 species and 325 reactions was used. After a successful validation against the experiments, a baseline study was conducted. Furthermore, a parametric study was performed to illustrate the effects of the structural properties of the combustion section on the burner performance. Increasing the pore density decreased the temperature difference between the gas and the solid phases. Consequently, a burner with higher pore density in the combustion section exhibited less emissions. When the porosity of the combustion section increased, the gas phase temperature also increased but the solid phase temperature remained virtually unchanged for the porosity values studied. As a result, higher pollutant emissions were observed at the burner outlet. Finally, it was noticed that when the combustion section was elongated, both phases gained higher temperatures and while CO emission decreased, NO emission increased.