{"title":"靠近冷表面的液滴燃烧","authors":"S. Chandra, C. Avedisian","doi":"10.1098/rspa.1990.0070","DOIUrl":null,"url":null,"abstract":"The combustion of a liquid droplet adjacent to a cold surface was studied experimentally. To isolate the effect of the proximity of the droplet to the surface, the ambient pressure (0.101 MPa), liquid composition (n-heptane), initial liquid volume (7 x 10-4 ml), surface material (quartz) and ambient temperature (20 ± 2°C) were held constant. A range of distances L from the surface were studied (1 mm < L < ∞). Both horizontal and vertical surface orientations were examined. A more limited set of experiments were carried out in a low gravity (i. e. low buoyancy) environment to provide a basis of comparison with relevant theoretical analyses. The flame shape, soot formation, fuel condensation, and droplet burning rate were all found to be strongly affected by the proximity of the droplet to the surface. For sufficiently large L the flame was observed to be closed around the droplet throughout burning. As L decreased, the flame was truncated. The droplet burning rate decreased as the droplet was brought progressively closer to the surface (in qualitative agreement with a relevant closed form potential flow solution to the analogous problem of a droplet burning adjacent to an adiabatic surface) and the burning rate of a droplet adjacent to a vertical surface was larger than for a horizontal surface. Surface orientation effects were observed to be absent for burning at low gravity. The extent of sooting as revealed by the flame colour was decreased, and fuel vapours condensed in a lens-like shape on the surface, as L was sufficiently reduced.","PeriodicalId":20605,"journal":{"name":"Proceedings of the Royal Society of London. A. 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引用次数: 4
摘要
实验研究了靠近冷表面的液滴的燃烧。为了分离液滴接近表面的影响,环境压力(0.101 MPa)、液体成分(正庚烷)、初始液体体积(7 × 10-4 ml)、表面材料(石英)和环境温度(20±2℃)保持不变。研究了距离表面L的距离范围(1 mm < L <∞)。水平和垂直表面方向都进行了检测。在低重力(即低浮力)环境下进行了一组更有限的实验,以提供与相关理论分析比较的基础。火焰形状、烟尘形成、燃料凝结和液滴燃烧速度都受到液滴接近表面的强烈影响。对于足够大的L,在整个燃烧过程中,火焰在液滴周围是封闭的。随着L的减小,火焰被截断。液滴燃烧速率随着液滴逐渐靠近表面而降低(定性地与液滴在绝热表面附近燃烧的类似问题的相关封闭形式势流解一致),并且液滴在垂直表面附近的燃烧速率大于水平表面。在低重力下燃烧时,表面取向效应不存在。通过火焰颜色显示出的烟熏程度减少了,并且燃料蒸汽在表面上凝结成透镜状,因为L被充分减少了。
The combustion of a liquid droplet adjacent to a cold surface was studied experimentally. To isolate the effect of the proximity of the droplet to the surface, the ambient pressure (0.101 MPa), liquid composition (n-heptane), initial liquid volume (7 x 10-4 ml), surface material (quartz) and ambient temperature (20 ± 2°C) were held constant. A range of distances L from the surface were studied (1 mm < L < ∞). Both horizontal and vertical surface orientations were examined. A more limited set of experiments were carried out in a low gravity (i. e. low buoyancy) environment to provide a basis of comparison with relevant theoretical analyses. The flame shape, soot formation, fuel condensation, and droplet burning rate were all found to be strongly affected by the proximity of the droplet to the surface. For sufficiently large L the flame was observed to be closed around the droplet throughout burning. As L decreased, the flame was truncated. The droplet burning rate decreased as the droplet was brought progressively closer to the surface (in qualitative agreement with a relevant closed form potential flow solution to the analogous problem of a droplet burning adjacent to an adiabatic surface) and the burning rate of a droplet adjacent to a vertical surface was larger than for a horizontal surface. Surface orientation effects were observed to be absent for burning at low gravity. The extent of sooting as revealed by the flame colour was decreased, and fuel vapours condensed in a lens-like shape on the surface, as L was sufficiently reduced.