Droplet evaporation characterization, although of great significance, is still challenging. The recently developed phase rainbow refractometry (PRR) is proposed as an approach to measuring the droplet temperature, size as well as evaporation rate simultaneously, and is applied to a single flowing n-heptane droplet produced by a droplet-on-demand generator. The changes of droplet temperature and evaporation rate after a transient spark heating are reflected in the time-resolved PRR image. Results show that droplet evaporation rate increases with temperature, from −1.28$\times {10}^{-8}$ m²/s at atmospheric 293 K to a range of (−1.5, −8)$\times {10}^{-8}$ m²/s when heated to (294, 315) K, agreeing well with the Maxwell and Stefan–Fuchs model predictions. Uncertainty analysis suggests that the main source is the indeterminate gradient inside droplet, resulting in an underestimation of droplet temperature and evaporation rate. With the demonstration on simultaneous measurements of droplet refractive index as well as droplet transient and local evaporation rate in this work, PRR is a promising tool to investigate single droplet evaporation in real engine conditions.

液滴蒸发表征尽管具有重要意义，但仍具有挑战性。提出了最近开发的相彩虹折光法（PRR）作为一种同时测量微滴温度，大小和蒸发速率的方法，并将其应用于按需微滴发生器产生的单个流动的正庚烷微滴。时间分辨的PRR图像反映了瞬态火花加热后液滴温度和蒸发速率的变化。结果表明，液滴的蒸发速率随温度的升高而增加，从-1.28开始$\times {10}^{-8}$大气293 K下的m ² / s至（-1.5，-8）的范围$\times {10}^{-8}$加热至（294，315）K时为m ² / s，与麦克斯韦和斯特凡-福克斯模型的预测非常吻合。不确定性分析表明，主要来源是液滴内部的不确定梯度，从而导致对液滴温度和蒸发速率的估计不足。通过在这项工作中同时测量液滴折射率以及液滴瞬态和局部蒸发率的演示，PRR是研究实际发动机条件下单个液滴蒸发的有前途的工具。