Abstract 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.

中文翻译：

---

在燃烧室相关环境压力下落壁撞击中的 Leidenfrost 行为

摘要 液体燃料燃烧系统需要在一系列运行条件下实现最佳性能——需要在一系列温度和压力下实现可预测的燃料喷射事件、喷雾破裂和汽化。在直喷燃烧器中，这些喷雾直接撞击燃烧室表面。尽管燃料液滴撞击壁面的结果主要受壁面温度和莱顿弗罗斯特效应的影响，但随着压力变化的液汽饱和点可能会影响液滴壁面传热速率和从成核到薄膜沸腾的转变。在本文中，环境压力对液滴撞击状态、扩散速率和液滴在撞击过程中的回弹速度的作用探讨了具有代表性的低沸点和高沸点纯烃液体（正庚烷和正癸烷）。在 1-20 bar 的环境压力和 35-300 ∘C 的壁温范围内获得了落壁撞击的高速图像序列，并且韦伯数为 ~ 50。使用高速记录液滴撞击序列CMOS 相机并被处理以测量液滴扩散、液滴回弹速度并跟踪液滴质心运动。液滴扩散和回弹的动力学在一系列环境压力下表现出类似的行为，在润湿与非润湿情况下（莱顿弗罗斯特温度以上）观察到的差异最大。对于这两种流体，液滴反弹的开始仍受饱和温度（随环境压力变化）和液体过热的热力学极限的限制。