2.2.3. Effect on turbine design
The different characteristics of impulse and reaction blading means that there are significant differences in the turbine designs. Impulse-turbine moving blades are carried on discs which are either integral with or attached to a small diameter shaft. The axial thrust on the rotor is small since there is no pressure drop across the blades and therefore no pressure forces across the discs. The presence of a pressure drop across the moving blades of the reaction turbine makes discs unviable. Instead, the discs are replaced by a greatly expanded hollow shaft known as a drum rotor.