Experimental investigation of diffusion flames with different baffle-plate air-hole diameters.

Diffusion flames are widely used in industrial combustion systems; however, the influence of baffle-plate air-hole diameter on flame characteristics and combustion performance remains insufficiently quantified through experimental studies. The present work experimentally investigates Liquefied Petroleum Gas (LPG) diffusion flames stabilized by multi-hole baffle plates with varying air-hole diameters. Five baffle-plate configurations with eight radially distributed air holes were tested at a constant thermal load of 32 kW over air–fuel ratios (AFR) of 15–30, while flame stability, temperature distributions, flame length, species concentrations, and combustion efficiency were systematically measured. The experimental facility consisted of an integrated setup linking air and fuel supply lines to the baffle plate and combustor chamber. The study involved the development of an empirical relation expressing flame length in terms of air-hole diameter (da) and AFR, where the discrepancy between predicted and experimental results averaged approximately 2.5%. Combustion efficiency decreased with increasing air hole diameters. Specifically, the da increased from 10 mm to 15 mm, the combustion efficiency dropped by approximately 10.17% at AFR = 15 and 11.04% at AFR = 20.