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首页> 外文期刊>International Journal of Heat and Mass Transfer >Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures
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Leidenfrost behavior in drop-wall impacts at combustor-relevant ambient pressures

机译：燃烧器相关环境压力下滴墙影响的莱顿弗洛斯特行为

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Liquid-fueled combustion systems demand optimal performance over a range of operating conditions-requiring predictable fuel injection events, spray breakup, and vaporization across a range of temperatures and pressures. In direct injection combustors, these sprays impinge directly on combustion chamber surfaces. Although the outcome of fuel droplets impacting a wall is primarily driven by the wall temperature and the Leidenfrost effect, the shifting liquid-vapor saturation point with pressure may influence the droplet-wall heat transfer rate and transition from nucleate to film boiling. In this paper, the role of ambient pressure on the droplet impact regimes, spreading rate, and droplet rebound velocity during impact are explored for representative low boiling point and high boiling point pure hydrocarbon liquids (n-heptane and n-decane). High-speed image sequences of the drop-wall impact were acquired for ambient pressures of 1-20 bar and wall temperatures ranging from 35-300 °C with a drop Weber number of - 50. Droplet impact sequences were recorded using a high-speed CMOS camera and were processed to measure the droplet spread, droplet rebound velocity and track the droplet centroid motion. The dynamics of the drop spreading and rebound show similar behavior across a range of ambient pressures with the largest differences observed for wetted versus non-wetted cases (above the Leidenfrost temperature). For both fluids, the onset of drop rebound remains bounded by the saturation temperature (shifting with ambient pressure) and the thermodynamic limit of liquid superheat. This leads to a decrease in the superheat temperature above the saturation point as the critical pressure is approached.
机译：液体燃料燃烧系统需要一系列操作条件的最佳性能 - 需要可预测的燃料喷射事件，喷雾分解和跨各种温度和压力的汽化。在直接喷射燃烧器中，这些喷雾直接冲击燃烧室表面。尽管施加墙壁的燃料液滴的结果主要由壁温和leidenFROST效果驱动，但是具有压力的变速液 - 蒸汽饱和点可能影响液滴 - 壁传热率和从核心转变为薄膜沸腾。在本文中，探讨了对液滴冲击制度，扩散率和液滴回弹速度的影响，探讨了施加期间的液滴冲击制度，扩散率和液滴回弹速度，用于代表性的低沸点和高沸点纯烃液（N-庚烷和N-癸烷）。获得落墙冲击的高速图像序列，用于1-20巴的环境压力，壁温度范围为35-300°C，滴落次数为50.使用高速记录液滴冲击序列CMOS相机并被加工以测量液滴扩散，液滴回弹速度并跟踪液滴质心运动。下降扩散和反弹的动态表明，在一系列环境压力范围内具有相似的行为，涉及湿润与非湿润的情况（在Leidenfrost温度上方）观察到的最大差异。对于这两个流体，液滴反弹的开始仍然受饱和温度的界限（与环境压力转移）和液体过热的热力学极限。当接近临界压力时，这导致高于饱和点高于饱和点的降低。

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