Research On Application Of Laser Scattering Method To Measure Exhaust Wetness And Diameter Of Water Droplet In Turbine

For power generation enterprises, the improvement of turbine has significant impact on economy. Now there are many methods to measure droplet size and humidity of turbine's last stage blade based on different principles, which have offered impelling ways to measure droplet size and humidity of turbine's last stage blade, but the existing thermodynamic methods require that the steams used in the experiments be representative sample, while the optical probe method would interfere with the flow. To overcome the above shortcomings, this paper provides a non-contact measurement method based on laser Mie scattering theory.First, this paper introduces the loss caused by the water droplet in last stage of turbine, and presents desiccation method used by the plant. Besides, the progress of the optical probe method is expounded in details, followed by a number of related optical knowledge. When various diameter particles are irradiated by a collimated laser light beam, light scattering phenomenon takes place.The scattering light parameter includes the information of the particles size distribution, but its computations are complicated. When the diameter of the particles satisfies some conditions, Mie theory is used for the calculation,recursive method is used to calculate the Mie scattering coefficient,at the same time, three-wave methods is use to obtain the diameter of the droplet size. If different light energies with different angle are measured, the particle size distribution can be calculated in theory. Many distribution functions are used to approach the particle size distribution, including Rosin-Rammer function in common use, with Matlab to code the corresponding programs. Based on the existing boiler experimental device, experimental platform is designed to simulate the wet steam, selecting the required thermocouple, pressure gauges, valves, and other attachments. And then the light path is designed for the wet steam which need measuring, and choose the photoelectric devices. Part of the experimental results is simply analyzed.