<scp>DC</scp> non‐transferred plasma current effects in methane‐hydrogen (40% H ₂ ) non‐premixed flames

Abstract Methane and hydrogen () mixtures represent a prominent research focus, motivated by their potential for low‐carbon emissions and superior combustion performance. The investigation of advanced techniques, including plasma‐assisted combustion, aims to optimize the combustion dynamics of these fuels further. To investigate the coupled mechanisms of flame‐thermal plasma interactions, a direct current (DC) non‐transferred plasma torch was positioned at the center of a quartz combustion chamber. The fuel composition used was 60 vol% and 40 vol% ; for safety considerations related to the plasma combustion system, the hydrogen addition did not exceed this 40% threshold. Experiments were conducted at five different plasma current levels. The findings indicate that the diffusion flame temperatures of the methane‐hydrogen mixture were significantly less sensitive to variations in plasma current and exhibited 4% less fluctuation compared to a reference 100% methane flame. Emission measurements for the 60% + 40% mixture revealed a distinct trend: nitrogen oxide () and carbon monoxide () concentrations decreased with increasing plasma current, while carbon dioxide () levels increased. The plasma current range of 25–30 amperes (A) has been identified as the optimum region for high efficiency and low emissions. Analysis of the flame morphology showed a general reduction in both flame length and thickness with increasing DC non‐transferred plasma current, suggesting a more compact and, intensified combustion zone. Plasma current accelerates combustion kinetics by increasing the flame propagation speed by up to 2.5 times. Plasma significantly enhances flame stability, reducing the oscillation amplitude by 89%.