Research And Development Of Laser Particle Sizers Based On Combined Spectrum Technology

Science and technologies are developing rapidly and there are more connections with particles size in many areas. Particle diameters can influence products qualities, energy consumption, pollution, etc. So it is important to measure particle size exactly. The laser particle sizer has advantages of high repeatability, accuracy, and broad measurable range. It is a kind of leading instruments in the particle size measurement area.The history and recent developments of the theories and technologies of particle size measurements are expatiated. This dissertation is focused on laser particle size measurement technologies. A lot of work was done in theories, key technologies, and research and development of sizer prototypes. Finally, the expected results are attained.The following are the main innovations.1. The combined spectrum technology in laser particle size measurement is presented. Two laser particle size measurement methods are then proposed, where signals are detected on two coaxial focal planes. As a result, the measurable size ranges and the dynamic ranges are extended.2. The improved conjugate gradient algorithm is proposed. The algorithm is based on the objective functions of the optimization algorithm. By adequately selecting the key parameters, it can be used to invert unimodal and multimodal particle size distributions. Simultaneity, the accuracy, the repeatability and the resolving of the sizers are enhanced.3. The grey-prediction theory is used to amend the vignette effect of the lens. The vignetted optical signals can be modified. The problem often appears when the sample is much far away from the lens.4. According to the combined spectrum technology, two new laser particle sizers are developed. The joint Si-photoelectric detectors are developed, they are the key part of the sizers. The combined optical lenses systems, the circuit board, and the mechanical systems are designed. In the optical systems, the particulate sample can be set on different positions, and the detectors are selected and jointed according to the optical systems. Therefore, the particle size in the ranges of 0.2 ~ 2000μm and 5 ~ 3500μm can be measured by the two sizers respectively. Experimental results on standarded particulate samples shows that the presented theories are corrected and the prototypes of the sizers are effective.