Identify the De Laval Turbine – Classification by Principle Select the correct classification of the classic De Laval turbine based on where pressure drop occurs and how energy conversion is accomplished.

Introduction / Context:
The De Laval turbine is one of the earliest practical steam turbines and underpins much of the elementary theory of impulse stages. Correctly identifying its type clarifies how the stage produces work and how velocity triangles are constructed.

Given Data / Assumptions:

• Classic single-stage design with a convergent–divergent nozzle set and one row of moving blades.
• Large pressure drop through the nozzles; negligible pressure change across the rotor.
• High-velocity jet from the nozzles impinges on the moving blades.

Concept / Approach:

In an impulse turbine stage, nearly the entire pressure drop occurs in stationary nozzles, converting pressure energy into kinetic energy. The moving blades ideally only redirect the flow, reducing its absolute velocity and changing whirl to produce torque, with little static pressure change. This description matches the De Laval turbine. Reaction turbines, in contrast, split the pressure drop between stator and rotor, causing additional acceleration within the moving passages.

Step-by-Step Solution:

Verification / Alternative check:

Historical diagrams and laboratory test data for De Laval wheels show near-constant static pressure across blades with significant velocity changes, consistent with impulse behavior.

Why Other Options Are Wrong:

Reaction and impulse–reaction imply pressure drop in the rotor, which is not the De Laval case. ‘‘None of these’’ is invalid as a clear correct classification exists.

Common Pitfalls:

Confusing multi-row Curtis (velocity-compounded) stages with De Laval; Curtis involves multiple rotor rows but still follows impulse principles.

Final Answer:

simple impulse turbine