Effect of confinement ratio on LPG diffusion flame characteristics

The behavior of flames can vary significantly in confined spaces compared to open spaces. This variation is influenced by the geometry of the combustor. This study experimentally examines the effect of confinement ratio (C.R.) on the characteristics of Liquefied Petroleum Gas (LPG) diffusion flames, such as visual appearance, length, temperature distribution, and concentrations of different species. The experiments are carried out at C.R.s of 2, 3, 5, and infinity, while maintaining a constant equivalence ratio of 1, a constant blockage ratio (B.R.) of 0.55 for a disc bluff body, and a fuel mass flow rate of 0.55 g/s. At C.R.s of 2 and 3, the confinement exerts a significant impact, resulting in a reduction in flame height. As the C.R. increases from 2 to 5, the flame length experiences an estimated 50 % growth, and the flame behavior is closely resembling that of the unconfined flame. As a result, lower C.R.s cause a decrease in flame size and a reduction in the flame length (Lf). Temperature profiles in both open and confined combustors display a consistent pattern: a quick rise to a maximum followed by a decline. Increasing C.R. slightly reduces CO2 and CO concentrations, with the lowest CO2 in unconfined spaces, while NO emissions show a minor decline as C.R. rises. CFD simulations using ANSYS Fluent were conducted to analyze LPG combustion in a non-premixed flame at C.R. = 5, with results compared to experimental measurements.