Which of the following statements is true for a Kaplan turbine?
- AIt has fixed blades and is used for low heads.
- BIt has adjustable runner blades and is used for high heads.
- CIt has adjustable runner blades and is used for low heads.Correct
- DIt is an impulse turbine.
Solution
Concept
Kaplan axial-flow turbine characteristics and operating head
Formula
NONE
Step-by-step solution
1. A Kaplan turbine is an axial-flow reaction turbine designed for low heads (under 30 m) and large volumetric flow rates. 2. Its hallmark feature is that its runner blades are adjustable in pitch during operation in conjunction with guide vanes. 3. Propeller turbines have fixed runner blades, whereas Kaplan turbines have adjustable runner blades. 4. Therefore, statement C is the correct description. Answer: C
Explanation
A Kaplan turbine is an axial-flow reaction turbine designed specifically for low operating heads and very high volume discharges. Its defining engineering feature is that both the guide vanes and runner blades are adjustable during operation, allowing automatic pitch optimization to maintain high part-load hydraulic efficiency.
Why the other options are wrong
A) A low-head turbine with fixed runner blades is a Propeller turbine, not a Kaplan turbine. B) Kaplan turbines operate under low heads, not high heads. D) Kaplan is a reaction turbine, whereas Pelton is an impulse turbine.
Shortcut
Kaplan turbine = Adjustable runner blades + Low head + Axial flow.
Common mistake
Confusing Kaplan turbines (adjustable blades) with Propeller turbines (fixed blades) or Pelton wheels (impulse).
Correct answer: C) It has adjustable runner blades and is used for low heads.