Fundamental Study of a New Gas-Liquid Detection Method in a Small Clearance with an Optical Fiber Probe

Abstract

In many positive displacement compressors, it is important to design oil supply structures to seal and lubricate small clearances with oil, but unknowing of the presence of oil film in them hinders their effective design. In this study, a new gas-liquid detection method in a small clearance is being developed, in which the tip of an optical fiber probe is placed in a small cavity formed on the clearance surface. This method thus requires that a fluid entering the clearance also fills the cavity to ensure that the probe contacts the inlet fluid to be detected. Characteristics of filling the cavity without the probe were investigated by experiment and calculation of two-phase flow, which revealed that the cavity is filled with inlet fluid when the Weber number is less than around one. The calculation with the probe also demonstrated phase changes in 10-µm clearance can be detected by this method.