2.2.5 Modern blading designs
Modern turbines are neither purely impulse or reaction but a combination of both, for the following reasons. Impulse turbines began employing reaction of up to 20% at the root of the moving blades in order to counteract the poor efficiency incurred from zero or even negative reaction.
On the other hand, reaction at the root of reaction turbines has come down to as little as 30-40% resulting in the reduction of the number of stages required and the sustaining of 50% reaction at the midpoint. Today it may be more accurate to describe the two designs as:
- 'Disc and diaphragm' turbine, using low reaction blading.
- 'Drum-rotor' turbine, using high reaction blading .