Influence of Water Marbles on Efficiency, Blade Fracture and Water Erosion of Steam Turbines

By analyzing the status of blade fracture and water erosion occurring in an extraction condensing turbine unit, the failure is found to be caused mainly by the braking force from water marbles, which inhibits the rotation of the rotor, and therefore directly affects the efficiency of the steam turbine. The formation mechanism of secondary water droplets from water marbles is compared with that from water films at blade trailing edge torn and broken by high-speed steam flows. It is pointed out that the number of water marbles can be effectively decreased by changing the structure of corresponding baffle plates, so as to reduce the mentioned braking force, economize the energy consumption, and therefore elongate the blade life and raise the unit efficiency.