Development of Steam Turbine Inlet Control Valve for Supercritical Pressure at Siemens Industrial Turbomachinery AB

Sammanfattning: The development in the steam turbine business is heading for applications with much higher steam parameters since this enables a raised efficiency. Steam parameters refer to the pressure and the temperature of the steam. The aim of this study was to generate concepts for steam turbine inlet control valves designed for higher pressure and temperature in comparison with the present design. Future steam power plants using solar energy, based on tower technology, request this kind of performance and are an important potential market. This master thesis at Linköping University has been written in collaboration with Siemens Industrial Turbomachinery AB. The performed work has incorporated literature studies, functional analysis and solid mechanics analysis, flow analysis, evaluation of sealings and cup springs and development of the dimensioning data for the future control valve. The aim was to find a design concept that sustains the new and higher steam parameters and is tolerant concerning vibrations. A systematical way to work has been applied during the project and a detailed planning was continuously followed and adjusted. Major methods used were product design specification, quality function deployment, morphological matrices, decision matrices and failure mode and effect analysis. Important programs used during the project were Pro/ENGINEER, MATLAB, FloEFD and MS Excel. Today’s valves are dimensioned for much lower performance than the new requirements in terms of pressure and temperature. The main problem for the present design is that the opening and closing forces requirements, with the new higher pressure, get unreasonably large. Therefore were many of the developed concepts equipped with a pressure balancing feature. This feature also gives another desirable result; the vibrations (that is the source of many of the problems with the present design) will also be reduced. During the early concept development phase, 15 different concepts were generated and after the concept evaluation only three concepts remained. These concepts were further developed in different areas of interest and finally one of the three was chosen to be the winning concept. The new valve design will most likely meet the requirements and has the potential to be refined for even higher pressure for future demands.