Francis Turbine vs. Kaplan Turbine

Attribute	Francis Turbine	Kaplan Turbine
Runner Type	Radial flow	Axial flow
Application	Medium to high head	Low to medium head
Efficiency	High	Very high
Blade Adjustment	Fixed blades	Adjustable blades
Runner Diameter	Large	Small to medium
Flow Control	Partially regulated	Fully regulated
Specific Speed	Medium	High
Installation	Vertical or horizontal	Vertical
Head Range	10-600 meters	2-70 meters

Introduction

Hydropower is a renewable energy source that harnesses the power of flowing water to generate electricity. Turbines play a crucial role in this process by converting the kinetic energy of water into mechanical energy, which is then used to generate electricity. Two commonly used types of turbines in hydropower plants are the Francis turbine and the Kaplan turbine. While both turbines serve the same purpose, they have distinct attributes that make them suitable for different applications. In this article, we will compare the attributes of the Francis turbine and the Kaplan turbine, exploring their design, efficiency, operating range, and applications.

Design

The Francis turbine is a reaction turbine that was developed by James B. Francis in the mid-19th century. It consists of a spiral casing, guide vanes, runner blades, and a draft tube. The spiral casing directs the water flow towards the guide vanes, which control the flow rate and direction. The water then enters the runner blades, which are curved to efficiently convert the water's kinetic energy into mechanical energy. The Kaplan turbine, on the other hand, is an axial-flow turbine that was invented by Viktor Kaplan in the early 20th century. It features adjustable blades that can be rotated to optimize performance under varying flow conditions. The design of the Kaplan turbine allows it to operate efficiently at low head and high flow rates.

Efficiency

When it comes to efficiency, both the Francis turbine and the Kaplan turbine have their strengths. The Francis turbine is known for its high efficiency at medium to high head applications. It can achieve efficiencies of up to 95%, making it an excellent choice for hydropower plants with moderate head and flow conditions. On the other hand, the Kaplan turbine excels in low head applications. Its adjustable blades allow it to maintain high efficiency even at low head and high flow rates. The Kaplan turbine can achieve efficiencies of up to 90%, making it ideal for hydropower plants located in rivers or areas with low head but high flow rates.

Operating Range

Another important attribute to consider when comparing the Francis turbine and the Kaplan turbine is their operating range. The Francis turbine operates best at medium to high head conditions, typically ranging from 10 to 600 meters. It is well-suited for hydropower plants located in mountainous regions or areas with significant water head. On the other hand, the Kaplan turbine is designed for low head conditions, typically ranging from 2 to 30 meters. It is commonly used in run-of-river hydropower plants or installations where the available head is limited. The adjustable blades of the Kaplan turbine allow it to adapt to varying flow conditions, making it versatile in its operating range.

Applications

The different attributes of the Francis turbine and the Kaplan turbine make them suitable for different applications in the hydropower industry. The Francis turbine is commonly used in large-scale hydropower plants with high head and flow conditions. Its high efficiency and ability to handle large volumes of water make it ideal for generating significant amounts of electricity. The Kaplan turbine, on the other hand, is often employed in small to medium-sized hydropower plants with low head and high flow conditions. Its adjustable blades and versatility in operating range make it a preferred choice for installations in rivers or areas with limited head.

In addition to their primary applications, both turbines can also be used in pumped storage hydropower plants. These plants store excess electricity by pumping water from a lower reservoir to an upper reservoir during periods of low demand. When electricity demand is high, the stored water is released, flowing through the turbines to generate electricity. The Francis turbine and the Kaplan turbine can both be utilized in this process, depending on the specific requirements of the pumped storage plant.

Conclusion

In conclusion, the Francis turbine and the Kaplan turbine are two widely used turbines in the hydropower industry. While the Francis turbine is known for its high efficiency at medium to high head conditions, the Kaplan turbine excels in low head applications. The Francis turbine operates best in mountainous regions or areas with significant water head, while the Kaplan turbine is designed for installations with limited head. Both turbines have their unique attributes that make them suitable for different applications, whether it be large-scale hydropower plants or small to medium-sized installations. Understanding the design, efficiency, operating range, and applications of these turbines is crucial in selecting the most appropriate turbine for a specific hydropower project.