Measuring of Mist Flow Rate with Optical Spatial Filter

Abstract

How to measure the mist flow rate ordering 1 mL/h is the key issue to configure the oil feeding system and/or to monitor the quantity of the lubricating oil for MQL engineering. Here, a new algorithm is reported, which is based on a spatial irregularity of scattered light from the mist particles. The flow rate in the tubing is not even, hence the spatial frequency method was considered not to be applicable to it. However, the core image of scattered light near around the center gives a sharp spectrum of the spatial frequency. To obtain the core image, the light source is focused on the center of fubing flow and the scattered light is formed on a linear CCD. The spatial filter consisted of the combinations of the pixels. And the sinusoidal wiegting-function makes it easy to generate a sharp frequency spectrum. The flow rate is estimated by the spatial velocity and the brightness of scattered light from the mist particles. It has the feasibility to construct a flow transducer for the very low flow rate such as lubricating oil with mist flow. To confirm the effect of proposed technique, a trial model is made and tested with several commercial MQL systems. It has a good agreement with the mass measuring method with bottle and tissu. Furthermore at in-line estimation in the MQL machining process, a transient phenomena of mist flow is detected.