Indian Journal of Science and Technology

Abstract

Background/Objectives: Porous medium burners are presented as an alternative technology in order to improve the thermal efficiency and emission characteristics of domestic cooking stoves. In this paper CFD analysis of a 90mm top diameter porous medium burner (PMB) which is made of two different sections, namely pre-heating and combustion section is considered. Methods/Statistical Analysis: Silicon carbide foam having a thickness of 25mm and 10ppi porosity in the combustion section and 6.5mm diameter steel balls in pre-heating section was used. The variation in the model was due to different measurement values of centre pipe length and fluid inlet diameter. The centre pipe length was 27.5mm, 55mm, 110mm and 220mm each, whereas the fluid inlet diameter was 15mm, 20mm and 25mm. The mass flow rate of air and fuel were 0.05kg/m3 and 0.009kg/m3 with temperature of air 300k and fuel 285k respectively. Wall temperature was taken as 300k and 5% turbulence intensity at all inlet and outlet. Air and LPG are used as oxidizer and Fuel. Findings: ANSYS Fluent was used to simulate the mixing and reaction of Fuel and Oxidizer through a two layer porous burner. The burner was evaluated considering turbulence model and Species Model. Total six 3D models are considered for simulation and results are taken as Contours of Temperature. It was found that porous burner having centre pipe diameter of 27.5mm and 25mm fluid inlet diameter gives the maximum surface temperature of 2250k. Increasing the centre pipe length by half (27.5mm – 55mm) caused a slight drop of surface temperature which is almost negligible. Furthermore, from the temperature contours, it was observed that increasing the center pipe length above 55mm reduced the surface temperature by 300k. From the four models considered the minimum surface temperature was 2087k, for porous burner model having 110mm centre pipe length and 25mm fluid inlet diameter. Based on the insight obtained from the CFD simulation, increasing the center pipe length above the range of 27mm to 55mm, might increase the chance of flashback. Considering the fluid inlet diameter, increasing the fluid inlet diameter by 5mm caused an increase of surface temperature by about 300k. Improvements/Applications: Porous medium combustion has been center of interest amongst researchers due to its higher thermal efficiencies and lower emission of Nox and CO gases. They are employing a porous media for various applications, such as: IC engines, heat exchangers, gas turbine and propulsion, hydrogen production and cooking applications. 

Keywords: Computational Fluid Dynamics (CFD), Cooking Application, Porous Burner (PB), Porous Medium Combustion (PMC), LPG