APPSC AEE (Civil/Mechanical) 2012
⭕ A. Causes noise and vibration of various parts
⭕ B. Makes the surface rough
⭕ C. Reduces the discharge of a turbine
⭕ D. Causes sudden drop in power output and efficiency
📚 Explanation:
Cavitation in a hydraulic machine occurs when the local pressure of the fluid falls below its vapor pressure, leading to formation and collapse of vapor bubbles.
🔹 The collapse of these bubbles near a surface generates shock waves that damage the metal surface.
🔹 This produces noise and vibration and reduces turbine efficiency.
🧮 Cavitation Factor Formula:
Where:
σ = Cavitation factor
Hₐ = Atmospheric pressure head (m of water)
Hᵥ = Vapour pressure head (m of water)
Hₛ = Suction pressure
H = Net head on the turbine (m)
Cavitation in a hydraulic machine occurs when the local pressure of the fluid falls below its vapor pressure, leading to formation and collapse of vapor bubbles.
🔹 The collapse of these bubbles near a surface generates shock waves that damage the metal surface.
🔹 This produces noise and vibration and reduces turbine efficiency.
🧮 Cavitation Factor Formula:
σ = (Hₐ - Hᵥ - Hₛ) / H
Where:
σ = Cavitation factor
Hₐ = Atmospheric pressure head (m of water)
Hᵥ = Vapour pressure head (m of water)
Hₛ = Suction pressure
H = Net head on the turbine (m)
👉 Therefore, the correct answer is: A. Causes noise and vibration of various parts
Key Points on Cavitation:
- Cavitation: Formation and collapse of vapor bubbles in liquid.
- Effects: Noise, vibration, and metal erosion.
- Prevention: Maintain high pressure at turbine inlet.
- Applications: Hydraulic turbines, pumps, propellers.
