Aeromechanic Validation of a New Steam Turbine LP Section: Test Major Outcomes

Abstract

To enhance the Steam Turbine product line rotating speed and efficiency, GE Company has developed a new generation of high rotating speed Steam Turbine Low Pressure (LP) Sections named HS family (see also Cosi at al., [1.]). The master component of the family, and its smallest size, is the 4-stage LP section HS8, capable of variable speed operation up to 11250 rpm. The aeromechanical validation of HS8 was carried out in two steps: a full-scale rotating test in a vacuum chamber (so called wheel Box Test, WBT) and a full-size test vehicle campaign in steam (Low Pressure Development Turbine, LPDT). During both tests the 4-stage rotors were equipped with a reliable system of strain gages and thermocouples. Aim of the present paper is to present an overview of the experimental results and post-processed data from both tests. Measured blades modes frequencies, responses and quality factors from both WBT and LPDT are described and compared, and the behavior of these parameters at different mass-flows and backpressures is explored. Then, interesting results from the comparison of damping (or Q factors), in WBT and LPDT test are presented. Finally, a methodology for nodal diameter configuration identification is described. To the best of authors’ knowledge the present paper is the deepest investigation about damping in WBT and prototypical test for steam turbine last stage blades.