Effects of hydrogen addition on the laminar methanol-air flame under different initial temperatures

Methanol has been regarded as a promising alternative fuel. However, the problem in cold start and the resulting high emissions consistently constrain the development of methanol engines. Meanwhile, blending hydrogen in methanol has the potential to alleviate the above problem. Effects of blending hydrogen on the laminar flames of methanol under changing initial temperatures was then investigated. The experiments were undertaken in a constant volume chamber. The chemical mechanism investigation was conducted using CHEMKIN. The hydrogen fraction increased from 0 to 0.8. The initial temperature changed from 350 K to 450 K. The results show that increasing the initial temperature and hydrogen component accelerate the flame propagation. For flames at 450 K and Φ = 1.2, when the hydrogen fraction increases from 0 to 0.8, the laminar flame speeds are 4.80, 4.85, 7.00, 9.27, 15.50 (m/s), respectively. Markstein length decreases and then increases with the increase in hydrogen fraction. For flames at 400 K and Φ = 1.0, when the hydrogen fraction increases from 0 to 0.8, the maximum mole fraction of H atom increases from 0.008 to 0.025 (a threefold increase). The rapidly accumulating hydrogen atoms promote the chain branching reaction (R5: O₂+H[dbnd]O + OH) and accelerate the combustion process.