Introduction of a New Family of Steam Turbine Low Pressure Stages - A Comprehensive Review of 10 Years of Experience in Design, Manufacturing, Experimental Validation and Field Application

Abstract

Low Pressure stage design characteristics play a key role in steam turbine product line as they typically set limits to the maximum turbine flow and rotating speed and have a strong influence on the overall turbine efficiency. LP stages design presents a combination of structural and aerodynamics challenges that oblige the manufacturers to develop and test the design well in advance with respect to the turbine design schedule. For the same reason (development complexity) an LP stages design is usually scaled to cover a wide range of rotating speed and annulus area. The set of scaled LP stage is referred to as LP stage family. 10 years ago the author’s company has started the design of a new family of LP stages for power generation and mechanical drive application. The initial phase of the development has focused on the design, manufacturing and experimental validation (wheel box test and full scale turbine test) of the master size for the reaction product line. Then master size design has been scaled to generate a wide family of LP stages. In parallel to this activity the application of this LP stage family on the impulse product line has been carried out leading to a hybrid rotor design. Eventually the dynamic behavior of the scaled blades design has been experimentally validated employing a combination of strain gages and tip timing frequency test. This paper will present a comprehensive review of all the phases of development and the major experimental results on the master and on the scaled designs with the intent to share the key technical aspects involved in the development of this components.