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首页> 外文期刊>Combustion Science and Technology >SIMULATIONS OF AUTOIGNITION AND LAMINAR PREMIXED FLAMES IN METHANE/AIR MIXTURES DILUTED WITH HOT PRODUCTS
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SIMULATIONS OF AUTOIGNITION AND LAMINAR PREMIXED FLAMES IN METHANE/AIR MIXTURES DILUTED WITH HOT PRODUCTS

机译：用热产品稀释的甲烷/空气混合物中的自燃和层状预燃火焰的模拟

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This article considers constant-pressure autoignition and freely propagating premixed flames of cold methane /air mixtures mixed with equilibrium hot products at high enough dilution levels to burn within the moderate to intense low oxygen dilution (MILD) combustion regime. The analysis is meant to provide further insight on MILD regime boundaries and to identify the effect of hot products speciation. As the mass fraction of hot products in the reactouts mixture increases, autoignition occurs earlier. Species profiles show that the products /reactants mixture approximately equilibrates to a new state over a quick transient well before the main autoignition event, but as dilution becomes very high, this equilibration transient becomes more prominent and eventually merges with the primary ignition event. The dilution level at which these two reactive zones merge corresponds well with that marking the transition into the MILD regime, as defined according to conventional criteria. Similarly, premixed flame simulations at high dilutions show evidence of significant reactions involving intermediate species prior to the flame front. Since the premixed flame governing equations system demands that the species and temperature gradients be zero at the "cold" boundary, flame speed cannot be calculated above a certain dilution level Up to this point, which again agrees reasonably well with the transition into the MILD regime according to convention, the laminar burning velocity was found to increase with hot product dilution while flame thickness remained largely unchanged. Some comments on the MILD combustion regime boundary definition for gas turbine applications are included.
机译：本文考虑了恒压自燃和冷甲烷/空气混合物与平衡热产品混合的自由混合火焰，它们在足够高的稀释水平下可以在中等至强烈的低氧稀释（MILD）燃烧方式下燃烧。该分析旨在进一步了解MILD制度的边界，并确定热产品形态的影响。随着反应产物混合物中热产物的质量分数增加，自燃会更早发生。种类分布表明，产物/反应物混合物在主要自燃事件之前的一个快速瞬变过程中大致平衡到一个新状态，但是随着稀释度变得很高，这种平衡瞬变变得更加突出，并最终与一次燃起事件合并。根据常规标准定义，这两个反应区合并的稀释水平与标记过渡到MILD方案的稀释水平非常吻合。同样，高稀释度下的预混合火焰模拟显示了在火焰前沿之前涉及中间物种的重大反应的证据。由于预混合的火焰控制方程系统要求“冷”边界处的物质和温度梯度为零，因此无法计算出高于一定稀释水平的火焰速度。到这一点为止，这再次与过渡到MILD模式相当吻合根据惯例，层流燃烧速度随热产物稀释而增加，而火焰厚度基本保持不变。其中包括对燃气轮机应用的MILD燃烧状态边界定义的一些评论。

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