Experimental study on the lean premixed combustion of xylene in porous media

Xylene is a widely used solvent in coating and chemical industries and a major volatile organic compound with neurotoxic and pathogenic effects. It is also a key precursor of ozone depletion and fine particulate matter, posing serious environmental and occupational risks. This study experimentally investigates lean premixed xylene–air combustion in a porous-medium burner, focusing on how the equivalence ratio affects flame stability, heat feedback, and extinction. A dual-layer reactor comprising ceramic foam and alumina beads is operated at Φ = 0.25–0.8, and axial thermocouples record temperature profiles to analyze flame propagation and conduction–radiation coupling. As Φ increases from 0.5 to 0.8, the flame front shifts upstream, stabilizes more rapidly, and the peak temperature rises markedly. At Φ = 0.8, a super-adiabatic peak of about 1320 K appears due to coupled thermal cracking and secondary oxidation of xylene, and steady combustion is reached after roughly 40–50 min. The most favorable condition is Φ ≈ 0.7, with a nearly uniform temperature field (T6 ≈ 1250 K) and minimal fluctuations. Under leaner conditions (Φ ≤ 0.45), insufficient heat feedback causes upstream-to-downstream extinction, yielding a stability limit of Φ ≈ 0.45. These results clarify heat-feedback kinetics and guide the design of low-emission, high-efficiency porous-medium burners.