In impulse turbine theory, energy transfer to the blades is primarily achieved by which phenomenon?

• A. Steam velocity increases through the rotating blades
• B. Steam flow is reduced through the nozzles
• C. Steam pressure is reduced in the nozzles
• D. Steam pressure decreases across the rotating blades

Answer: (C)

The energy transfer to the blades in an impulse turbine comes from the high-velocity steam jet created by expanding the steam in the stationary nozzles. The nozzles convert pressure energy into kinetic energy by lowering the steam pressure, accelerating the jet to a high speed. When this jet strikes and is deflected by the rotating blades, its change in momentum exerts a force on the blades and delivers work to the shaft. In this setup, the key driver is the pressure drop in the nozzles that produces the high-velocity jet, not a large pressure change across the blades themselves.