Typical application of De Laval (single-stage impulse) turbines De Laval turbines are most commonly applied in which operating range, considering their single-stage impulse design and very high rotor speeds?

Introduction / Context:
The De Laval turbine is a classic single-stage impulse turbine with a convergent-divergent nozzle that accelerates steam to very high velocities. Because only one rotor row extracts work, the optimum rotor speed is extremely high, making it suitable for specific applications rather than large power plants.

Given Data / Assumptions:

• Single set of nozzles and a single moving blade row (no compounding).
• High jet velocity and corresponding high optimum blade speed.
• Mechanical constraints require gear reduction if driving moderate-speed machinery.

Concept / Approach:

Single-stage impulse machines extract only part of the kinetic energy efficiently unless the rotor spins very fast. Thus, De Laval turbines are best for small power duties where compactness and simplicity are desired and high-speed operation (often with reduction gears) is acceptable. For large power outputs, multi-stage (compounded) impulse or reaction turbines are preferred to achieve reasonable shaft speeds and higher overall efficiency.

Step-by-Step Solution:

Verification / Alternative check:

Historical and modern micro-turbine applications of De Laval-type stages confirm their use as high-speed, small-output prime movers.

Why Other Options Are Wrong:

Large power service requires multi-staging to control speed and improve efficiency.“Low speed” options contradict the fundamental velocity-triangle requirements of single-stage impulse turbines.

Common Pitfalls:

Assuming all turbines are interchangeable across power ranges; staging dictates practical speed and scale.

Final Answer:

for small power purposes and high speeds