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高温壁面含氧液滴蒸发及微爆特性的试验研究

EXPERIMENTAL STUDY ON EVAPORATION AND MICRO-EXPLOSION CHARACTERISTICS OF OXYGEN-CONTAINING DROPLETS ON HIGH-TEMPERATURE WALL

  • 摘要: 以含氧燃料液滴为研究对象, 搭建了一套高温壁面液滴蒸发试验平台, 并进行了试验系统一致性验证; 在此基础上, 分别开展了乙醇生物柴油、聚甲氧基二甲醚柴油(PODE柴油)以及二硝酰胺铵(ADN)溶液3种含氧燃料在沸点温度及Leidenfrost温度时的蒸发及微爆特性研究. 结果表明, 3种燃料在两种特定温度下的蒸发及微爆特性均会呈现不同的现象: 与沸点温度时不同, 乙醇生物柴油液滴在Leidenfrost温度下, 大部分时间在高温壁面上进行弹跳或者移动, 液滴微爆延迟时间和持续时间明显变长, 液滴微爆强度也相对较高; PODE柴油液滴在Leidenfrost温度下, 最后的蒸发过程中并没较大铺展开, 基本一直都在壁面弹跳或移动中消失, 液滴微爆延迟时间和微爆持续时间相对变短, 但液滴微爆强度变化较小; ADN推进剂液滴在Leidenfrost温度下, 会不停地进行弹跳或者移动, 直至液滴完全消失, 液滴微爆对液滴体积影响较小(当量蒸发速率为0), 液滴微爆延迟时间变短, 且液滴微爆强度有一定的变小. 另外, 通过3种燃料微爆特性对比发现: ADN推进剂液滴在沸点温度下, 蒸发时除了有气泡产生, 内部组成成分之间还会发生剧烈的热解反应, 进而产生着火现象, 直至液滴消失, 其微爆延迟时间相对最短, 微爆持续时间占液滴生存时间的百分比也最小, 但液滴微爆强度相对较大; PODE柴油液滴在沸点温度下的微爆延迟时间相对较长, 微爆持续时间占液滴生存时间的百分比也较大.

     

    Abstract: Oxygen-containing fuel droplet is taken as the research object in this article, a high-temperature wall droplet evaporation test platform is built, and the consistency of the test system is verified. On this basis, the evaporation and micro-explosion characteristics of three oxygen-containing fuels, namely ethanol-biodiesel, polymethoxy dimethyl ether diesel (PODE-diesel), and ammonium dinitramide (ADN) solution, were studied at boiling point temperature and Leidenfrost temperature. The results show that the evaporation and micro-explosion characteristics of the three fuels exhibit different phenomena at two specific temperatures: unlike at boiling point temperature, ethanol-biodiesel droplets bounce or move mostly on high-temperature wall at Leidenfrost temperature, resulting in significantly longer delay and duration of droplet micro explosion, and relatively higher droplet micro-explosion intensity; At the Leidenfrost temperature, PODE-diesel droplets do not spread out significantly during the final evaporation process, and they basically disappear during wall bouncing or movement. The delay time and duration of droplet micro-explosion are relatively shorter, but the droplet micro-explosion intensity changes less; At the Leidenfrost temperature, ADN droplets will continuously bounce or move until the droplets completely disappear. The droplet micro-explosion has a small impact on the droplet volume (equivalent evaporation rate is 0), the delay time of droplet micro explosion becomes shorter, and the droplet micro-explosion intensity decreases to a certain extent. In addition, by comparing the micro-explosion characteristics of three types of fuels, it was found that at the boiling point temperature, ADN droplets not only produce bubbles during evaporation, but also undergo intense pyrolysis reactions between internal components, leading to ignition until the droplets disappear. The delay time of micro-explosion is relatively short, and the percentage of micro-explosion duration to droplet survival time is also the smallest, but the micro-explosion intensity of droplets is relatively large; The delay time of micro-explosion of PODE diesel droplets at boiling point temperature is relatively long, and the percentage of micro-explosion duration to droplet survival time is also large.

     

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