中文摘要：

通过雷诺平均纳维叶斯托克斯方程模型数值模拟研究了同流热气中氧浓度对CH_4／H_2射流火焰扩散燃烧的影响。研究基于JHC开放火焰实验装置，采用涡耗散概念模型和GRI．3．0详细化学反应机制进行数值模拟，研究同流热气中氧浓度变化的影响。结果显示，随着同流热气中氧浓度的减小，下游温度峰值及中间组分OH的质量分数峰值明显下降，温度分布更均匀。OH质量分数峰值位置比温度峰值位置略微靠外（同流热气侧）。H_2CO主要分布在计算域内的低温区，高温时该组分被快速消耗；不同的燃烧模式下H_2CO浓度分布差别很大。通过分析发现，要使传统窄小区域的快速燃烧模式过渡到大空间的慢速弥散燃烧，应减小同流热气中氧浓度。

英文摘要：

This paper reported an investigation by Reynolds averaged Navier Stokes （RANS） modeling on diffusion combustion of a CH_4/H_2 jet issuing into a hot coflow （JHC）. The simulations were conducted with the eddy dissipation concept （EDC） model and the detailed reaction mechanisms （GRI-Mech 3.0）. The JHC configuration in the simulation was modified by removing the outside air and the coflow oxygen level was decreased from 23.3% to 3% （by mass）. Results suggest that by decreasing the oxygen level in the coflow, the peak temperature and OH mass fraction decrease, and the temperature distributuion becomes more uniform. It is found the location of the OH mass fraction peak is outside of that of the temperature peak slightly. Moreover, the H_2CO is generated mainly in the lowtemperature region and consumed very quickly at high temperatures; in different combustion regimes, the H_2CO distribution is quite different. The combustion mode may be transformed from traditional to moderate ＆ intense low oxygen dilution （MILD） regime by reducing the oxygen level in the hot coflow.