De Laval (single-stage impulse) steam turbine practice:\nIn a De Laval impulse turbine, the nozzle that accelerates the steam jet is positioned how relative to the moving blades?

Introduction / Context:
The De Laval turbine is a classic single-stage impulse turbine that uses a convergent–divergent nozzle to accelerate steam to very high velocity before it strikes the moving blades. Understanding why the nozzle is placed very close to the rotor blades helps minimize losses and improve stage efficiency in impulse machines.

Given Data / Assumptions:

• Impulse principle: pressure drop occurs almost entirely in the nozzle; blades ideally see velocity change only.
• Nozzle produces a high-velocity jet at a designed exit angle α.
• Mixing with ambient and jet spreading increase with free-jet travel distance.

Concept / Approach:
In an impulse stage, the goal is to preserve as much nozzle exit kinetic energy as possible until it is transferred to the rotor. If the nozzle is far from the blades, the jet spreads, entrains surrounding steam, and slows down due to turbulence and viscous effects before reaching the blade inlet. Placing the nozzle very close to the blade inlet edge reduces these free-jet dissipation losses and maintains the desired incidence angle, improving diagram efficiency.

Step-by-Step Solution:

Verification / Alternative check:
Practical De Laval designs show nozzle rings closely hugging the blade periphery. Computational and experimental studies confirm reduced incidence losses and less jet dissipation when spacing is minimized.

Why Other Options Are Wrong:

• “No”: Placing the nozzle far away allows jet decay, increased incidence losses, and lower efficiency.

Common Pitfalls:
Confusing impulse and reaction staging; in reaction stages, pressure drop also occurs across blades, but proximity of fixed and moving rows remains important to control losses.

Final Answer:
Yes