Curtis turbine is

The Curtis turbine is a type of impulse turbine that uses velocity compounding to extract energy from high-velocity steam efficiently.

In an impulse turbine, the steam undergoes a complete pressure drop in the nozzles, converting pressure energy into kinetic energy before it strikes the turbine blades.

Velocity compounding involves expanding steam through a single set of nozzles to produce high-velocity jets, which then pass through multiple rows of moving blades separated by fixed blades.

The fixed blades redirect the steam flow onto the next row of moving blades without changing its pressure, helping to gradually reduce its velocity and extract more work.

This configuration is specifically known as the Curtis stage and is used to limit the high speed of turbine rotors, making the design more practical and efficient.

Option A is incorrect because a Curtis turbine is not a reaction turbine.

Option B is incorrect because “pressure velocity compounded” is not an accurate classification; Curtis turbines use velocity compounding only.

Option C is incorrect because it describes pressure compounding, not velocity compounding.

Option D is correct because it correctly identifies the Curtis turbine as a velocity compounded impulse steam turbine.