Question

According to the direction of flow through the runner, Kaplan turbine is a:

• A. Tangential flow turbine
• B. Inward radial flow turbine
• C. Outward radial flow turbine
• D. Axial flow turbine

Hint:

Think of the flow path in different turbines. Pelton hits buckets tangentially, Francis flows radially (and axially), and Kaplan flows primarily along the axis of the shaft, like a propeller.

Answer 1

The Correct Option is D

Step 1: Understand the classification of turbines based on the direction of flow.
Hydraulic turbines are classified based on the direction of water flow through the runner (rotating part). The main classifications are:
Tangential flow turbine: The water flows along the tangent of the runner. Example: Pelton turbine.
Radial flow turbine: The water flows radially, either from the periphery to the center (inward radial flow) or from the center to the periphery (outward radial flow). Examples: Francis turbine (mixed flow, but primarily radial), Kaplan turbine (has a radial component at the inlet of the runner blades).
Axial flow turbine: The water flows parallel to the axis of rotation of the runner. Example: Propeller turbine, Kaplan turbine.
Mixed flow turbine: The water flow has both radial and axial components. Example: Francis turbine. Step 2: Focus on the Kaplan turbine.
The Kaplan turbine is a reaction turbine that operates with a relatively low head and high flow rate. It is a further development of the propeller turbine, featuring adjustable runner blades. Step 3: Determine the direction of flow in a Kaplan turbine runner.
In a Kaplan turbine, the water enters the runner with a significant radial component but turns to flow essentially parallel to the axis of the shaft as it passes through the runner blades. The primary direction of flow through the main working section of the Kaplan runner is axial. Step 4: Compare the Kaplan turbine flow with the turbine classifications.
Based on the predominant direction of flow through the runner being parallel to the axis of rotation, the Kaplan turbine is classified as an axial flow turbine. While there might be a radial component at the very inlet of the runner blades, the overall flow is directed axially. Step 5: Evaluate the other options.
Option 1 (Tangential flow turbine): This is incorrect as the water does not flow tangentially to the Kaplan runner.
Option 2 (Inward radial flow turbine): While there is an initial radial component, the flow is not primarily inward radial.
Option 3 (Outward radial flow turbine): The flow in a Kaplan turbine is not outward radial. Step 6: Select the correct answer.
According to the direction of flow through the runner, a Kaplan turbine is an axial flow turbine.