Influence of the inlet channel flow of a steam turbine on solid particle erosion of the control stage nozzles

Based on experiments and numerical simulation, the influence of the inlet flow channel of a steam turbine on the solid particle erosion of nozzle segments was investigated systematically. The results indicate that the upstream channels of the nozzle segment, such as the regulating valve, nozzle chamber and connection pipe, concentrate the solid particle erosion to a small number of nozzles or local regions of the nozzle, which greatly reduces the time for nozzle damage. Compared with the present erosion situation, measures adopted to distribute particles at the inlet of a nozzle chamber uniformly can double the service life of a nozzle segment, while the service life can be increased by eight to ten times through measures to distribute particles uniformly at the inlet of a nozzle segment. This article shows that the service life of a nozzle segment can be doubled through substituting a nozzle chamber with a tangential steam intake for one with a normal steam intake. Moreover, a boride layer with 0.04 mm effective thickness or a CrN layer with 0.01 mm effective thickness can further double the service life of a nozzle segment. In addition, a pocket-trap arranged in the particle-aggregated area after an elbow can reduce the weight loss at nozzle sites with the most serious erosion by over 85%. These investigations are of great significance to the long-term, safe and high-efficiency running of a steam turbine.