Heat transfer characteristics of premixed methane-air flame jet impinging on a hemispherical surface

A combined experimental and numerical investigation was conducted to study the heat transfer characteristics of premixed methane-air flame jet impinging on a hemispherical surface. The effects of the mixture equivalence ratio (phi = 0.9-1.5), burner to plate distance (H/d = 1-6), the mixture Reynolds number (Re = 300-800) and curvature ratio (d/D = 0.1-0.133) on the heat transfer characteristics were investigated. CFD software was used to simulate the laminar methane-air flame impinging on a hemispherical surface for different operation conditions, and the heat flux distribution and average heat flux on the impingement surface were obtained. The heat transfer efficiency is presented to quantify the thermal performance of impinging flame jet. It was found that the equivalence ratio has an important effect on the flame height, which in turn affects the heat transfer efficiency, and the stoichiometric mixture has the lowest heat transfer efficiency because its lowest flame height. The burner-to-plate distance plays a decisive role in the heat transfer characteristics of impinging flame jet, and when the flame premixed cone just touches the impingement surface, it has the best thermal performance. Higher mixture Reynolds number has higher flame height, temperature and heat flux distribution, but lower heat transfer efficiency. The configuration of impinging flame jet with smaller curvature ratio has better thermal performance.