Re-Recognition of the MILD Combustion Regime by Initial Conditions of T-in and X-O2 for Methane in a Nonadiabatic Well-Stirred Reactor
Re-Recognition of the MILD Combustion Regime by Initial Conditions of T-in and X-O2 for Methane in a Nonadiabatic Well-Stirred Reactor
复制标题
非绝热充分搅拌反应器中甲烷的 T-in 和 X-O2 初始条件重新识别 MILD 燃烧状态
DOI：
10.1021/acs.energyfuels.9b04177
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发表时间：
2020
期刊：
影响因子：
5.3
通讯作者：
Liu Zhaohui
中科院分区：
文献类型：
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作者：
Luan Congcong;Xu Shunta;Shi Bing;Tu Yaojie;Liu Hao;Li Pengfei;Liu Zhaohui
基于Cavaliere和de Joannon（Prog.能量燃烧2004，30，329 - 366）。此外，不同的燃烧制度下的非绝热条件下的详细演变进行了全面检查。结果表明，存在一个临界XO 2（XO 2 *），在此临界值以下，只要Tin超过自燃点（Tsi），就可以无条件地建立MILD燃烧，超过此临界值，Tin需要显著提升，以满足MILD燃烧的数学判据。因此，这两个区域分别被称为无条件温和燃烧（UMC）和有条件温和燃烧（CMC）。对于绝热条件，XO 2 * 计算为9.7%，表明与富氧对应物相比，用氧稀释的氧化剂将更容易实现MILD燃烧。有趣的是，XO 2 * 被发现攀升的热损失比（EAR）的增加，这表明，提高WSR的EAR将有助于扩大UMC区域，即，更容易建立MILD燃烧。此外，通过增大燃烧室的容积，高温燃烧（HTC）可以转变为CMC甚至UMC，为在实际应用中实现MILD燃烧提供了一种潜在的解决方案。然而，一旦过热，燃烧区将进一步向不稳定燃烧（USC）甚至无反应（NR）区转移。因此，在强热提取场景（例如锅炉）中的MILD燃烧应用将是一个挑战。有趣的是，在较大的HLR条件下，较高的Tin和较低的XO 2能够拓宽UMC区域。此外，与N2稀释相比，CO2或H2O稀释将导致更宽的UMC区域，而CO2由于其最高的XO 2 * 而更明显。此外，通过热提取将燃烧状态从HTC转移到MILD燃烧，CO2稀释比N2或H2O稀释更有效。
A more straightforward combustion map for identifying moderate or intense low-oxygen dilution (MILD) combustion regime in a well-stirred reactor (WSR) using initial inlet temperature (Tin) and oxygen mole fraction (XO2) has been proposed based on previous mathematical criteria provided by Cavaliere and de Joannon (Prog. Energy Combust. Sci.2004, 30, 329−366). Furthermore, the detailed evolution of different combustion regimes under the nonadiabatic condition has been comprehensively examined. Results show that there exists a criticalXO2(XO2*), below which MILD combustion can be established unconditionally as long asTinexceeds the self-ignition point (Tsi) and beyond whichTinneeds to be remarkably promoted to fulfill the mathematical criteria of MILD combustion. Thus, the two regions are termed unconditional MILD combustion (UMC) and conditional MILD combustion (CMC), respectively. For the adiabatic condition,XO2*is calculated to be 9.7%, indicating that MILD combustion will be more easily achieved with an oxygen-diluted oxidizer than the oxygen-enriched counterpart. Interestingly,XO2*is found to climb as the heat loss ratio (HLR) increases, suggesting that enhancing the HLR of the WSR would help expand the UMC region, namely, more readily establishing MILD combustion. In addition, high-temperature combustion (HTC) can shift to CMC or even UMC by just enlarging HLR, providing a potential solution to realize MILD combustion in practical applications. However, the combustion regime would further shift to unsteady combustion (USC) or even no reaction (NR) regions once the heat is overextracted. Hence, it would be a challenge for MILD combustion application in intense heat extraction scenarios, such as boilers. Interestingly, higherTinand lowerXO2are found able to widen the UMC region under larger HLR conditions. Moreover, CO2or H2O dilution would result in a wider UMC region compared to N2dilution, while it is more pronounced for CO2due to its highestXO2*. Besides, the shifting of the combustion regime from HTC to MILD combustion by heat extraction would be more effective with CO2dilution than either N2or H2O dilution.