TABLE OF CONTENTS The mechanical design of the turbine steam path begins after completion of the selection of the cycle equipment, its arrangement, the determination of the number of stages, and the thermal sizing of the blade rows. The thermal design provides information on the number of stages, the blade geometries, and the variation of thermal conditions throughout the steam path. At completion of the thermal process, there can still be a number of thermal variables that are to be evaluated by the mechanical process, but essentially the scope of the unit and its general arrangement has been established.
Normally, before the heat balance has been prepared, the thermal design engineer and the mechanical designer will have determined the basic arrangement, including the number of flows at each pressure range, the points at which steam will be extracted for regenerative feed heating, and any other extractions which may be required.
Therefore, the requirements of the mechanical process will, in general, have been defined, if only in broad scope. What the mechanical process is to do, is size the various components so thermal requirements are met and stress levels and natural frequencies are within acceptable ranges that will not endanger the structural integrity of the unit.
The mechanical design process accepts the detailed data developed by the thermal design engineer. Then, to complete the mechanical design of the unit, there is a certain amount of data that must be provided from the thermal sizing calculations, and the requirements specified...
