Britannica Sources used in this answer

How do Kaplan and propeller turbines differ from Francis and Deriaz turbines?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Rows of white wind turbines with spinning blades stand on a dry, grassy landscape at a wind farm near Tehachapi, California. — turbine Wind turbines near Tehachapi, California.

In mechanical engineering, Kaplan, propeller, Francis, and Deriaz turbines are all classified as reaction turbines, but they differ significantly in their flow patterns and blade adjustability.1

Flow Characteristics

Kaplan and Propeller Turbines: These operate using an axial flow, meaning the water moves parallel to the turbine's main shaft.1
Francis and Deriaz Turbines: These utilize a mixed-flow design. Water enters the turbine radially inward and discharges axially.1

Blade Adjustability

Fixed-Blade: Propeller and Francis turbines are designed with fixed blading.1
Adjustable-Blade: Kaplan and Deriaz turbines feature blades that can be rotated about their axis, which is positioned at a right angle to the main shaft.1

The ability to adjust blades allows Kaplan and Deriaz turbines to maintain higher efficiency across varying load conditions. While Francis turbines are widely used for their versatility across medium-head ranges, the Deriaz design is specifically noted for its utility in medium-sized machines and pumped storage applications, offering a lower runaway speed than the Kaplan turbine.23