Abstract: A new method for measuring the void fraction in lubricating oil is put forward based on image processing. The homogeneous property of the sampled images is analyzed and the differences of the sampled images under different background are compared. By means of the color-difference formula, the differences between sampled images are calculated and the linear fit curve about the relationship between void fraction and color-value is obtained. The void fraction in lubricating oil in oil-air lubrication system is measured by using this method and the results are satisfactory, which shows that this measuring method is reliable. The method can be used not only in the void fraction measuring in oil-air lubrication system, but also in other two-phase fluid.

Key words: Color difference, Image processing, Lubricating oil, Void fraction