Low reaction stages are often used as control stages of steam turbines, ORC turbines, drive and rocket turbopump turbines. Some of the benefits of low reaction stages vs higher reaction stages are:
- Smaller radial size (and weight) for the given power and rotation speed
- Compatibility with use of partial admission, which is used to accommodate low volumetric flow, with the needed low pressure gradients in the rotor blades to reduce leakage penalties
- Both above factors allow increasing of nozzle and rotor blade heights
- Smaller radial size provides lower disk rim speeds and disk stresses
- Low reaction generally means lower axial thrust of the rotor
- Velocity stage configurations are possible for low reaction designs (Curtis stage for example, Fig.1). Velocity stages allow further reduction in radial size and increasing blade heights
