Application Of Digital Image Technique In Measurement Of Bubble Void Fraction

Based on image process, a new method is proposed to measure void fraction without contact. This method breaks through the traditional point measure and sensor technology.According to different optics-reverberation character of water and gas, this paper put forward how to identify gas from the gas-water digital image and how to f -urther calculate void fraction. The result shows that the method possesses relatively satisfactory precision.At first, bubble flow image is acquired using laser and incandescence lamp respectively as light source and using CCD. According to different optics-dispersion character, threshold segmentation method is proposed to identify gas from the gas-water flow, which make steadfast base for further calculate void fraction.The precision of threshold directly affect the calculate precision of void fraction. Via refer to literature and theory study, three methods, namely ENT, OTSU, and iteration method are putted forward to calculate void fraction and via lots of experiment, three methods are compared and induced. In the end, OTSU is recommend which it has satisfactory precision and speed.Based on the former result, the algorithm of two dimension and instantaneous void fraction is proposed and carry out through programming.United with Visual C++ language which face to object, a software is exploitedwhich have functions like gray transform, image improve, bubble identify, voidfraction calculation, which show the strongpoint of object-facing programming.In order to validate the reliability and practicability of the image technique in measurement of bubble void fraction, a test aiming at water-gas field is done. The result shows that the value of void fraction is reliable and can reflect the real status.In this paper the error source is analyzed and discussed and the approach of how to advance measure precision is proposed, which has significant fact meaning.The content in this paper is preparatory attempt that combines image technique and gas water field measurement technology. This research make strong base for the further application of image technique in two phases flow of gas-water and has significant learning and practicable value.