Abstract
This chapter presents the basic thermodynamic and aerodynamic characteristics of axial-flow turbines. It covers the preliminary design and analysis of single- and multi-stage axial turbines. The main goal in the preliminary stage design of a turbine is to fix the shapes of the velocity triangles, either by setting the flow angles or by choosing values for the three dimensionless design parameters— φ, ψ, and R . A consideration of the ways the preliminary design choices affect the turbine basic layout and the efficiency can provide useful guidance to the designer .The development of the axial-flow turbine clearly depends upon the design advances made in the field of steam turbines. Three key non-dimensional parameters such as design flow coefficient, stage loading coefficient, and stage reaction are related to the shape of the turbine velocity triangles and are used in fixing the preliminary design of a turbine stage. The calculations needed to fix the size, the number of stages, the number of aerofoils in each blade row, and the velocity triangles are covered in the chapter. It covers the merits of different styles of turbine design including the implications for mechanical design such as centrifugal stress levels and cooling in high speed and high temperature turbines. Through the use of some relatively simple correlations, the trends in turbine efficiency with the main turbine parameters are also presented in the chapter.
Published Version
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