Analysis on Solid Particle Erosion in the Governing Stage of a High-Parameter Steam Turbine

Abstract

The solid particle erosion (SPE) of flow passage is a universal problem in modern high-parameter steam turbines. With the continuous improvement of the working parameters of the steam turbine, the problem of SPE is becoming more serious. This problem is caused by the ferric oxide exfoliations carried by steam from the inner wall of the boiler tube into the steam turbine flow passage, causing the stator blades, the rotor blades, and the shroud to be eroded under impingement and scuffing failure. The SPE cannot only destroy the blade profile, increase the roughness of the blade surface, and affect the aerodynamic performance of the blade, but it can also shorten the maintenance cycle, prolong the maintenance downtime, and even increase the cost for steam turbine maintenance thereby reducing the unit efficiency and safety. In order to simulate SPE in the governing stage of a high-parameter steam turbine, this study adopts the Lagrange method and the Finnie erosion model. The motion characteristics of five different kinds of solid particle, including the solid particle trajectory, are thoroughly analyzed. The regulation of the erosion distribution in the radial and axial directions to the stator and rotor blades is studied to present the mechanism of SPE. Simulated results show that before their collision with the blades, the particles of the small diameters flow with the main stream, and their trajectories are close to the steam streamlines. By contrast, the particles of the large diameters are hardly influenced by the external factors, and their trajectories are close to the straight line. The SPE distribution of the stator and rotor blades varies with the particle diameter. The eroded area in the stator blade is mainly located at the leading edge and the pressure surface, particularly the mid-rear part of the pressure surface, whereas no eroded area can be observed in the suction surface. The small particles greatly affect the erosion distribution of the stator blade. The eroded area in the rotor blade is primarily at the mid-rear part of the pressure surface and the suction surface, which is close to the leading edge. The eroded area takes on a typical slop shape, and the erosion position has an obvious upward trend. The proposed research reveals both the motion characteristics of the solid particles and the distribution regulation of the SPE in the steam turbine flow passage. The analysis results provide references for the governing stage of a high-parameter steam turbine to prevent SPE.