The runner of __________ turbine always be under pressure of above atmospheric pressure.
A
Turgo
B
Girand
C
Kaplan
D
None of the mentioned

Question

The runner of __________ turbine always be under pressure of above atmospheric pressure.

Examoogle · Accepted Answer

Kaplan

Explanation: The Kaplan turbine is a reaction turbine where the fluid enters the runner at a pressure significantly higher than atmospheric pressure. This pressure difference is maintained throughout the flow passage to facilitate energy extraction as the water moves across the runner blades.

Working Principle: In a reaction turbine like the Kaplan, the pressure drop occurs partially in the fixed guide vanes and partially in the moving runner blades. The runner is completely enclosed in a casing, and the water flows under high pressure, ensuring the blades are fully submerged and subjected to a pressure greater than the ambient atmospheric pressure throughout the energy conversion process.

Key Formulas: $P_{inlet} > P_{atm}$ — Inlet pressure is always maintained above atmospheric in reaction turbines; $\eta_h = \frac{P_{runner}}{P_{water}}$ — Hydraulic efficiency definition

Key Points: Kaplan turbines are axial flow reaction turbines.; They are designed for low head and high discharge conditions.; The runner blades are adjustable to maintain high efficiency under variable load.; Draft tubes are mandatory to recover pressure energy.

Advantages: High efficiency at part-load due to adjustable blades.; Compact size compared to other turbines for low head applications.

Disadvantages: Complex mechanical construction.; Risk of cavitation due to reaction principle.

Applications: Low head hydro power plants.; Run-of-river projects.

Additional Info: The Pelton wheel is an impulse turbine where the pressure at the runner is atmospheric.. Turgo turbines are also impulse-type turbines, thus maintaining atmospheric pressure at the runner.

Answer: C is correct — The Kaplan turbine is a reaction turbine which operates with the runner fully enclosed and subjected to pressure higher than atmospheric.

Exam Tip: Remember: Reaction turbines (Kaplan/Francis) have pressure variation across the runner, while Impulse turbines (Pelton/Turgo) maintain constant atmospheric pressure around the runner.

Related Questions

Discussion (0)