Curtis stage identification in steam turbines In steam turbine terminology, a Curtis turbine refers to which type of staging/compounding arrangement used to reduce rotor speed while extracting work efficiently?

Introduction / Context:
The Curtis turbine (often called a Curtis stage) is a classic configuration in steam turbine design. It is used to handle a large available pressure drop by converting it into high jet velocity in one set of nozzles and then extracting work over two or more moving blade rows separated by one or more intermediate guide (fixed) rows. Recognizing what “Curtis” means helps students connect blade velocity triangles with practical compounding strategies for speed control.

Given Data / Assumptions:

• A high-pressure steam supply expands through nozzles to produce high jet velocity.
• Multiple moving blade rows are arranged with intermediate fixed guide rows.
• Total pressure drop occurs mainly in the first nozzle set; subsequent rows primarily redirect and extract kinetic energy.

Concept / Approach:

In velocity compounding, the entire pressure drop is taken in one nozzle set, creating a very high jet velocity V. That kinetic energy is then extracted over multiple moving rows (e.g., two) so that each moving row operates at a lower relative velocity, keeping rotor speed within manageable limits. This is precisely the Curtis concept, distinguishing it from pressure compounding (Rateau) where pressure drop is split across several nozzle stages, and from reaction staging where pressure drops in both fixed and moving blades.

Step-by-Step Solution:

Verification / Alternative check:

Blade-to-jet speed ratios and velocity triangles for the Curtis stage show reduction of jet velocity in steps across successive moving rows, consistent with velocity compounding principles.

Why Other Options Are Wrong:

Pressure compounded turbine: that is Rateau staging, not Curtis.Simple reaction turbine: involves pressure drop in moving blades, unlike Curtis.Pressure-velocity compounded: combines both methods; Curtis specifically refers to velocity compounding.Simple impulse without compounding: lacks multiple moving rows used in Curtis.

Common Pitfalls:

Confusing “Curtis” (velocity compounding) with “Rateau” (pressure compounding). Remember: Curtis = velocity-compounded impulse stage.

Final Answer:

velocity compounded turbine