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The design of steam turbine components is driven by high efficiency demands and also requirements for increased operational flexibility due to more renewable energy sources being added to the grid. Therefore, fossil power plants which operate reliably under these conditions must be designed. Robust low pressure (LP) end stage blades are one key factor for modern steam turbine design to meet current and future market requirements. In operation, LP end stage blades of steam turbines are exposed to complex mechanical load, resulting in stresses mainly due to blade vibration and high centrifugal forces. Design methods accounting for high cycle fatigue (HCF) and low cycle fatigue (LCF) are required for fatigue lifetime calculation. To determine the HCF component strength and to validate the calculation procedure, an HCF component test facility for full-scale LP end stage blades has recently been established at Siemens. Besides the validation of the calculation procedures, the full-scale component tests serve as part of upfront validation to minimize risk for first time implementation of newly developed as well as next generation blades, and to demonstrate operational robustness of the existing fleet. This paper describes the development and setup of the HCF component test facility for full-scale LP end stage blades at Siemens, the successful execution of HCF component tests with blades of different sizes, surface conditions and materials, and the evaluation of the results. In addition, crack growth and threshold behavior has been investigated in detail. Based on the test results, validation of the corresponding calculation methods has been performed. An outlook on further development of test facilities is provided. |
