Theory of Turbomachinery Stages

The energy transfer in turbomachinery is established by means of the stages. A

turbomachinery stage

comprises a row of fixed, guide vanes called

stator blades

, and a row of rotating blades termed

rotor

. To elevate the total pressure of a working fluid,

compressor stages

are used that partially converts the mechanical energy into potential energy. According to the conservation law of energy, this energy increase requires an external energy input which must be added to the system in the form of mechanical energy. Figure 5.1 shows the schematic of an axial compressor stage that consists of one stator and two rotor rows. In general, a

compressor component

starts with a rotor row followed by a stator row. Compressor configurations are also found that starts with an

inlet guide vane

. To define a unified station nomenclature for compressor and turbine stages, we identify with station number 1 as the inlet of the stator, followed by station 2 as the rotor inlet, and 3, rotor exit. The absolute and relative flow angles are counted counterclockwise from a horizontal line. This convention allows an easier calculation of the off-design behavior of compressor and turbine stages during a transient operation, as we will see later. This angle definition is different the angle conventions used in literature, [1], [2], [3], and [4].