Abstract The effect of water-vapor addition to oxidizer on flame radiation is assessed experimentally and numerically through the study of laminar coflow ethylene-fueled non-premixed flames. Oxygen-deficient conditions were studied to closely represent real confined fire situations. Experimental soot volume fraction distributions, presented in a previous study, are complemented with temperature and radiation measurements. Experimental data are compared and complemented with numerical simulations. The relative importance of the thermal, chemical and dilution effects of water-vapor is also investigated through numerical modeling. Addition of water-vapor to oxidizer leads to a decrease in soot concentration, flame temperature, emitted radiation and radiant fraction, regardless of the Oxygen Index (OI). The measured temperatures in the sooting region by two-color pyrometry are in reasonably good overall agreement with the numerical predictions. Soot is the main radiation emitter in the ethylene flame under all the conditions studied, but its relative importance decreases with the water-vapor addition. CO2 is the second most important contributor. Depending on the OI, the relative importance of the water-vapor addition to flame radiation varies. At lower OI the dominant effect is thermal, while at higher OI (normal air condition) the effect of the water-vapor is shared by the three effects: dilution, chemical, and thermal.

中文翻译：

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缺氧条件下水蒸气加入氧化剂对非预混层流共流乙烯火焰热辐射特性的影响

摘要 通过对层流共流乙烯燃料非预混火焰的研究，通过实验和数值评估了氧化剂中添加水蒸气对火焰辐射的影响。研究了缺氧条件以密切代表真实的密闭火灾情况。先前研究中提出的实验烟尘体积分数分布与温度和辐射测量相辅相成。实验数据与数值模拟进行比较和补充。还通过数值模拟研究了水蒸气的热效应、化学效应和稀释效应的相对重要性。向氧化剂添加水蒸气会导致烟灰浓度、火焰温度、发射辐射和辐射分数的降低，而与氧指数 (OI) 无关。通过双色高温计测得的烟尘区域的温度与数值预测的总体一致性相当好。在所有研究条件下，烟尘是乙烯火焰中的主要辐射源，但其相对重要性随着水蒸气的加入而降低。二氧化碳是第二重要的贡献者。根据 OI，水蒸气添加对火焰辐射的相对重要性各不相同。在较低的 OI 下，主要影响是热效应，而在较高的 OI（正常空气条件）下，水蒸气的效应由三种效应共享：稀释、化学和热效应。但它的相对重要性随着水蒸气的加入而降低。二氧化碳是第二重要的贡献者。根据 OI，水蒸气添加对火焰辐射的相对重要性各不相同。在较低的 OI 下，主要影响是热效应，而在较高的 OI（正常空气条件）下，水蒸气的效应由三种效应共享：稀释、化学和热效应。但其相对重要性随着水蒸气的加入而降低。二氧化碳是第二重要的贡献者。根据 OI，水蒸气添加对火焰辐射的相对重要性各不相同。在较低的 OI 下，主要影响是热效应，而在较高的 OI（正常空气条件）下，水蒸气的效应由三种效应共享：稀释、化学和热效应。