For measuring size, concentration and velocity of droplets from the cyclone separator inlet and outlet, a measurement system based on trajectory image processing was developed. Principles of measurement were introduced. Droplets from cyclone separator were always spherical under the surface tension of water. It was reasonable to approximate the width of trajectory particle image as the diameter of droplets. The distance over which droplets moved in exposure time was obtained from trajectory image by processing, and the velocity of droplets could be easily calculated. Telecentric lens was used as an important part of measurement system. Common lens exhibited varying magnification for objects at different distances from the lens, but telecentric lens provided the same magnification at all distances, so droplets at different distances were the same size in the image. Firstly, images of particles were taken by capture system, and images were processed with a computer program. Then the particle size, concentration and velocity could be calculated. The system was installed in an experimental set-up that was used to study the performance of the cyclone separator. The experiment results showed that the system avoided the inversing process and had high size resolution as compared with traditional measurement system with the light scattering method. And it could make a measurement in line, and was better than other systems.
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