The cavitation phenomenon in hydraulic turbines typically occurs at
- AThe inlet of the guide vanes.
- BThe exit of the runner or the entrance of the draft tube where pressure is lowest.Correct
- CThe center of the main shaft.
- DThe surface of the trash rack.
Solution
Concept
Cavitation in Hydraulic Turbines
Formula
N/A
Step-by-step solution
1. Identify the question regarding where cavitation typically occurs in a hydraulic turbine. 2. Recall that cavitation occurs at regions of lowest pressure, which is at the exit of the runner or the entrance of the draft tube. 3. Select Option B as the correct choice.
Explanation
Option B is correct because cavitation occurs when water pressure drops very low, causing vapor bubbles to form. In a hydraulic turbine, the pressure reaches its lowest point right where the water leaves the runner and enters the draft tube, making it the primary location for cavitation.
Shortcut
To remember where cavitation occurs in hydraulic turbines, use the rule "Lowest Pressure = Exit/Draft Entrance": - Cavitation = Low Pressure: Vapor bubbles form where fluid pressure drops to its lowest level. - Key Location: Right where water exits the runner and enters the draft tube.
Common mistake
A common mistake is selecting Option A by confusing the high-velocity inlet region with the minimum-pressure region. In hydraulic turbines, pressure continually decreases as fluid passes through the runner, reaching its lowest point at the runner exit or draft tube entrance where cavitation actually occurs.
Correct answer: B) The exit of the runner or the entrance of the draft tube where pressure is lowest.