薄层液膜厚度的点测量和空间测量方法综述

液膜现象广泛存在于自然界和工业过程中，特别是在发动机中，燃油雾化通常会形成亚毫米量级乃至微米量级的薄层液膜，其厚度的高精度测量对发动机的设计和改进具有重要意义。介绍了薄层液膜厚度测量中常用的点测量方法和空间测量方法。点测量方法包括电测法和全内反射法，用于单点液膜厚度的测量，具有成本低、操作简单的优点，但不具有空间分辨能力。空间测量方法包括电测法、荧光强度法和平面激光诱导荧光法，可同时测量多个位置乃至连续区间内的液膜厚度，获取液膜分布和运动发展信息。其中电测法操作方便、稳定性高，但是会对液膜产生扰动；而光测法为非侵入方法，适用于高速运动液膜的厚度测量。

A review of the methods of point measurement and spatial measurement on thin liquid film thickness

Liquid film phenomena exist widely in nature and in industry processes. In particular, fuel spray in combustion engines can always form the thin liquid film in sub-millimeter or micron scales. The high precision measurement of the liquid film thickness is vital for the design and improvement of combustion engines. In this paper, we briefly review the point measurement and spatial measurement methods that are commonly used in the thin liquid film thickness measurement. Point measurement methods mainly include electric methods and the total internal reflection (TIR) method for measuring the liquid film thickness at a single position, which are low cost and easily operational but have no spatial resolution. Spatial measurement methods mainly include electric methods, fluorescence intensity method and planar laser induced fluorescence (PLIF) method, which can simultaneously measure the liquid film thickness at multiple positions or in continuous regions and obtain the information about the film thickness distribution and film movement and development. Among spatial measurement methods, electric methods are easily operational and highly stable, but the electrodes can disturb the liquid film. On the other hand, the optical methods are always non-intrusive and suitable for the measurement of the liquid film in high speed motion.