Simultaneous measurements of fine and coarse droplets of wet steam in a 330 MW steam turbine by using imaging method

Abstract

In order to fully comprehend the properties of fine and coarse droplets of wet steam flow in the steam turbine, the simultaneous imaging measurements method for fine and coarse droplets of wet steam was proposed based on RGB three wavelength bands light extinction and single frame single exposure principles. The innovative probe based on that method, which consisted of a telecentric lens and a color camera, was developed. The algorithm of RGB three wavelength bands light extinction was proposed for measuring the size distribution and wetness of fine droplets. And an imaging method based on single frame single exposure was used for the measurement of size, velocity, flow direction, and amount concentration of coarse water. The probe was applied to measure the wet steam in downstream of the last stage of a 330 MW steam turbine. The measured size and wetness of the fine droplets are in the range of 0.7–0.9 µm and between 6% and 9%, respectively. The maximum velocity and diameter of the coarse water droplet could reach 225.7 m/s and about 200 µm, respectively. Furthermore, several kinds of special forms coarse droplets images were obtained. And the characteristic and forming reasons of these coarse droplets were preliminarily discussed for the further experimental study.

Keywords

Steam turbine wet stream fine droplets coarse droplets imaging method

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