Transcritical phenomena of autoignited fuel droplet at high pressures under microgravity
Transcritical phenomena of autoignited fuel droplet at high pressures under microgravity
复制标题
微重力高压下自燃燃料液滴的跨临界现象
DOI：
10.1007/bf02872083
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发表时间：
2005
期刊：
影响因子：
--
通讯作者：
Toshikazu Kadoka
中科院分区：
文献类型：
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作者：
D. Segawa;Tomoki Kajikawa;Toshikazu Kadoka
为深入了解超临界气体环境中自燃的单燃料液滴燃烧现象，进行了微重力条件下的实验研究。实验利用了落井舱内和飞机抛物线飞行期间的微重力环境。悬浮在高压燃烧室冷段细石英纤维尖端的十八醇液滴被快速转移到电炉中的热气体介质中，随后在超临界气体环境中自燃和燃烧燃料液滴。使用氧气和氮气的高压气态混合物作为环境气体。利用嵌入式热电偶测量了超临界气体环境中燃料液滴温度随时间的变化。在氧气浓度降低的超临界气体环境中，获得了自燃燃料液滴或燃料块的连续背光图像。所观察到的点火延迟的压力依赖性和与嵌入热电偶的液滴的燃烧时间与以前的结果是一致的。同时成像与测温表明，燃料的外观显着改变周围的纯燃料的临界温度测量燃料温度。在超临界气体环境中，燃料的界面温度远远超过了纯燃料的临界温度。在超临界气体环境中，燃料在燃烧结束之前很久就气化了。气化时间占燃烧时间的比例随环境压力的增加而单调减小。
An experimental study has been performed under microgravity to obtain the detailed information needed for the deep understanding of the combustion phenomena of single fuel droplets which autoignite in supercritical gaseous environment. The microgravity environments both in a capsule of a drop shaft and during the parabolic flight of an aircraft were utilized for the experiments. An octadecanol droplet suspended at the tip of a fine quartz fiber in the cold section of the high-pressure combustion chamber was transferred quickly to be subjected to a hot gaseous medium in an electric furnace, this followed by autoignition and combustion of the fuel droplet in supercritical gaseous environment. High-pressure gaseous mixture of oxygen and nitrogen was used as the ambient gas. Temporal variation of temperature of the fuel droplet in supercritical gaseous environment was examined using an embedded fine thermocouple. Sequential backlighted images of the autoignited fuel droplet or the lump of fuel were acquired in supercritical gaseous environment with reduced oxygen concentration. The observed pressure dependence of the ignition delay and that of the burning time of the droplet with the embedded thermocouple were consistent with the previous results. Simultaneous imaging with thermometry showed that the appearance of the fuel changed remarkably at measured fuel temperatures around the critical temperature of the pure fuel. The interface temperature of the fuel rose well beyond the critical temperature of the pure fuel in supercritical gaseous environment. The fuel was gasified long before the end of combustion in supercritical gaseous environment. The proportion of the gasification time to the burning time decreased monotonically with increasing the ambient pressure.