Experimental Investigation of Cool Flame Behavior of Isolated n-Decane/Ethanol Droplet under Microgravity
Experimental Investigation of Cool Flame Behavior of Isolated n-Decane/Ethanol Droplet under Microgravity
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DOI：
10.1007/s12217-021-09893-5
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发表时间：
2021-08
影响因子：
1.8
通讯作者：
S. Ando;Kei Shimada;Daijiro Eto;O. Moriue
中科院分区：
文献类型：
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作者：
S. Ando;Kei Shimada;Daijiro Eto;O. Moriue
为了研究乙醇浓度对分离的二元燃料液滴冷却火焰特性的影响，对乙醇体积分数不同的正十一烷/乙醇液滴进行了实验和数值模拟。将环境压力设置为大气压，温度在600~660℃之间变化。在此条件下，正十一烷虽然观察到冷焰，但不会引起热焰着火。分别用CCD型摄像机和K型热电偶测量了液滴直径和冷却火焰温度。并用全瞬变数值模型进行了一维数值模拟。在对多组分液滴的蒸发过程进行模拟时，除了对组分流量、温度连续性、逸度平衡等假设外，还假设了多组分液滴的蒸发过程。将正十二烷液滴插入到高温环境中后，由于蒸发的冷却作用，蒸发突然加速，液滴表面温度降低。冷火焰点火后，离液滴最近的热电偶的温度最高，说明液滴附近有较大的热释放。乙醇加入正十二烷后，冷火焰着火延迟期延长。这可能是因为乙醇的高挥发性推迟了正庚烷的蒸气形成。然而，乙醇的体积分数对冷火焰温度的影响不大。这可能是因为在所有条件下，在冷火焰位置积累的正十一烷和OC10H19OOH几乎是相同的。
To investigate the effect of ethanol concentration on the cool flame characteristics of isolated binary fuel droplet, experiments and numerical simulations onn-decane/ethanol droplet were conducted, varying the volume fractions of ethanol. Ambient pressure was set to atmospheric pressure and the temperature was varied from 600 to 660 K. Under these conditions, although cool flame was observed forn-decane, it did not induce hot flame ignition. CCD camera and K-type thermocouple were used to measure the droplet diameter and cool flame temperature, respectively. Moreover, one dimensional numerical simulation was performed with the fully transient numerical model. In addition to the assumptions on species flux, temperature continuity, fugacity equilibrium was assumed to simulate the evaporation process of multicomponent droplet. After then-decane droplet was inserted into the hot ambience, evaporation was suddenly promoted and the temperature near the droplet surface decreased due to the cooling effect of evaporation. After the ignition of cool flame, the thermocouple nearest to the droplet showed the highest temperature, which implies that large heat release occurred near the droplet. When ethanol was added ton-decane, the cool flame ignition delay became longer. This is probably because the vapor formation ofn-decane was delayed due to the high volatility of ethanol. However, the cool flame temperature was not significantly varied by the volume fraction of ethanol. This is probably becausen-decane and OC10H19OOH accumulating at the cool flame location was almost the same for all conditions.