Wyniki 1-1 spośród 1 dla zapytania: authorDesc:"ANNA GRZYMKOWSKA"

Preliminary design of the last stage of supercritical steam turbine and proposition of anti-erosion coating for blades surface DOI:10.15199/148.2017.9.2

  Modern power plants have to meet high technological and environmental demands, such as increased efficiency and low emission levels. These strong restrictions can be met by supercritical power plants, which produce the power up to 1100 MW. Such a high power level requires considerable live steam mass-flow rate. When the steam flows through turbine stages, its pressure drops and specific volume rises. As the pressure is low and specific volume is high in the last stages, dimensions of turbine blades rise considerably and so does steam velocity. At the same time turbine spins with rotation speed of 3000 rpm, what results in extreme stresses caused by centrifugal and bending forces, especially at blades tips. Steam turbine expansion line goes below the saturation curve and ends in water-steam area. One-phase working medium changes now into two-phase fluid - steam with water droplets. These droplets hit the blades with extreme velocities and are the source of erosion. Droplet impact erosion reduces turbine efficiency and reliability by eroding blades leading edges, what may potentially lead to catastrophic failures. Furthermore, droplets can also erode sealing surface of bypass valve plug during turbine start-up, causing leakage and allowing steam to bypass the turbine [1 - 9]. Problems associated with droplet impact erosion of blades surface in steam turbines last stages are challenging. Such problems have recently occurred in many supercritical and ultra-supercritical units. In some cases, turbine efficiency has decreased by 4% after only two years of operation [10]. Computational model of supercritical power plant In order to determine steam parameters at the inlet and outlet of turbine last stage, a computational model of supercritical thermal cycle have been created. The model was [...]

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