Hydraulic Machines MCQ with answer and solution

Concept

Kaplan Turbine Characteristics

Formula

Q = (π/4)(D_o² - D_b²)V_f, P = ηρgQH

Step-by-step solution

1. Review the given question about selecting the most suitable hydraulic turbine for low head (less than 30 m) and high discharge. 2. Recall that Kaplan turbines are axial flow reaction turbines designed specifically for operating efficiently under low head and high discharge conditions. 3. Compare the given options and select Option (c) as the correct choice.

Explanation

A Kaplan Turbine is an axial flow reaction turbine specifically designed to handle large volumes of water (high discharge) at low water pressure or height (low head, less than 30 m). Its adjustable propeller blades allow it to maintain high efficiency even when water flow changes, making it ideal for low-head hydroelectric projects like river dams.

Shortcut

To easily remember turbine selection based on Head and Discharge, use these memory rules: - Kaplan: Low Head, High Discharge (Think "K-L-H": Kaplan = Low Head, High Flow). - Pelton Wheel: High Head, Low Discharge (Think "P-H-L": Pelton = High Head, Low Flow). - Francis: Medium Head, Medium Discharge (Think "Francis = Fairly Medium for both").

Common mistake

A common mistake is selecting Option A (Pelton Wheel) by confusing low-head and high-head turbines, as the Pelton wheel is designed for high head and low discharge conditions. Another frequent mistake is selecting Option B (Francis Turbine) by incorrectly assuming it applies universally to all head and discharge conditions, whereas it is best suited for medium head and medium discharge.