What is the difference between reaction turbine and impulse turbine?

Turbines play a vital role in converting energy into mechanical work. But did you know that there are different types of turbines used in various applications? The two primary types are reaction turbines and impulse turbines. While they both serve the same purpose, their working principles and applications differ significantly. This article will help you understand these differences, explain how each type operates, and highlight where they are commonly used. Whether you’re a student, engineer, or simply curious, this guide will give you a clear understanding of what sets these turbines apart.

What is a Reaction Turbine?

A reaction turbine is a type of turbine that generates power through the combined action of pressure and velocity changes as fluid moves through the blades. It is commonly used in hydroelectric power plants.

How Does a Reaction Turbine Work?

In a reaction turbine, fluid enters the turbine’s blades, causing the pressure to drop as it passes through. This pressure drop creates a reaction force that drives the blades, generating mechanical energy. The fluid’s velocity also changes, contributing to the energy conversion process. The turbine operates in a fully enclosed casing, allowing the fluid to flow smoothly over the blades.

Do You Know?
Reaction turbines work on the principle of Newton’s third law of motion, which states that for every action, there is an equal and opposite reaction.

Where are Reaction Turbines Used?

Reaction turbines are typically used in low to medium head (height) hydroelectric power plants where the water pressure is relatively low but the flow rate is high. They are also used in steam power plants where high efficiency is required. Examples include Francis and Kaplan turbines.

What is an Impulse Turbine?

An impulse turbine is a type of turbine that generates power solely through the change in velocity of a jet of fluid (typically water or steam) striking the blades. It is commonly used in high head hydroelectric power plants.

How Does an Impulse Turbine Work?

In an impulse turbine, fluid is directed through a nozzle, converting all its pressure energy into kinetic energy, forming a high-velocity jet. This jet strikes the turbine blades, causing them to move and generate mechanical energy. The pressure remains constant throughout the process, and only the velocity of the fluid changes. The turbine typically operates in an open environment where the fluid is free to exit after hitting the blades.

Do You Know?
Impulse turbines are designed to operate efficiently in high-head applications, where water falls from a significant height, creating a high-velocity jet.

Where are Impulse Turbines Used?

Impulse turbines are best suited for high-head, low-flow applications where the energy comes from the high velocity of the water or steam. These turbines are often found in mountainous regions or areas with significant elevation differences. Examples include Pelton and Turgo turbines.

What are the Key Differences Between Reaction and Impulse Turbines?

1. Working Principle

• Reaction Turbine: Operates based on the combined action of pressure and velocity changes.
• Impulse Turbine: Operates based on the change in velocity alone, with constant pressure.

2. Fluid Flow

• Reaction Turbine: Fluid flows over the entire blade surface, both in the radial and axial directions.
• Impulse Turbine: Fluid strikes the blades at a specific point, causing a direct change in velocity.

3. Enclosure

• Reaction Turbine: Enclosed in a casing to manage pressure changes and fluid flow.
• Impulse Turbine: Operates in an open environment where the fluid is free to exit after striking the blades.

4. Application

• Reaction Turbine: Suitable for low to medium head applications, such as low-head hydroelectric power plants.
• Impulse Turbine: Ideal for high-head applications, such as mountainous regions with significant elevation differences.

5. Efficiency

• Reaction Turbine: Generally more efficient in low head applications due to the pressure and velocity interaction.
• Impulse Turbine: More efficient in high head applications, where the kinetic energy of the fluid is maximized.

What are the Advantages of Reaction Turbines?

• High Efficiency: Especially in low to medium head applications where pressure and velocity changes work together.
• Compact Design: Enclosed casing allows for smooth fluid flow and reduced energy loss.
• Versatile: Can be used in both water and steam power plants.

What are the Advantages of Impulse Turbines?

• Simple Construction: Open design with fewer components makes it easy to maintain.
• Efficient in High-Head Applications: Maximizes the kinetic energy of high-velocity jets.
• Durable: Designed to withstand the impact of high-speed fluid jets.

What are the Disadvantages of Reaction Turbines?

• Complex Design: Requires a fully enclosed casing and precise engineering to manage pressure and velocity changes.
• Limited to Low and Medium Head Applications: Not suitable for high-head applications where impulse turbines excel.

What are the Disadvantages of Impulse Turbines?

• Less Efficient in Low-Head Applications: Relies solely on velocity changes, making it less efficient in low-head scenarios.
• Open Design: May lose energy if the fluid is not directed properly.

Which Turbine is More Suitable for Hydroelectric Power Plants?

The choice between a reaction and impulse turbine depends on the specific conditions of the hydroelectric power plant. If the plant is located in an area with low to medium head (height), a reaction turbine like the Francis or Kaplan turbine is more suitable. However, if the plant is in a mountainous region with high head, an impulse turbine like the Pelton or Turgo turbine is the better choice.

How to Choose Between Reaction and Impulse Turbines?

When selecting a turbine, consider the following factors:

• Head (Height) of the Water Source: High head favors impulse turbines, while low to medium head favors reaction turbines.
• Flow Rate: High flow rates are better suited for reaction turbines, while low flow rates work well with impulse turbines.
• Efficiency Requirements: Reaction turbines are generally more efficient in low to medium head applications, while impulse turbines excel in high head scenarios.
• Maintenance Needs: Impulse turbines are easier to maintain due to their simple construction.

Top Facts About Turbines

• Fact 1: The Pelton turbine, an impulse turbine, was invented by Lester Allan Pelton in the 1870s.
• Fact 2: Francis turbines, a type of reaction turbine, are the most widely used turbines in hydroelectric power plants.
• Fact 3: Impulse turbines are ideal for generating power in remote locations with high elevation differences.
• Fact 4: Reaction turbines are more commonly used in steam power plants due to their high efficiency.
• Fact 5: Turbines convert mechanical energy into electrical energy, making them a key component in power generation.

FAQs

1. What is the main difference between reaction and impulse turbines?

The main difference lies in their working principles. Reaction turbines operate on the combined action of pressure and velocity changes, while impulse turbines work solely on the change in velocity.

2. Which turbine is more efficient?

Efficiency depends on the application. Reaction turbines are more efficient in low to medium head applications, while impulse turbines are more efficient in high head scenarios.

3. Can reaction turbines be used in high head applications?

No, reaction turbines are not suitable for high head applications. Impulse turbines are better suited for these conditions.

4. What is a Pelton turbine?

A Pelton turbine is a type of impulse turbine used in high head, low flow applications.

5. Where are Francis turbines used?

Francis turbines are commonly used in low to medium head hydroelectric power plants.

6. Are impulse turbines easier to maintain?

Yes, due to their simple construction and open design, impulse turbines are generally easier to maintain.

7. What is the role of a nozzle in an impulse turbine?

The nozzle in an impulse turbine converts pressure energy into kinetic energy, forming a high-velocity jet that strikes the blades.

8. Why are reaction turbines enclosed in a casing?

The casing helps manage pressure changes and ensures smooth fluid flow over the blades in a reaction turbine.

9. What types of fluid are used in turbines?

Water and steam are the most common fluids used in turbines for energy conversion.

10. How do turbines generate electricity?

Turbines convert the mechanical energy produced by the movement of blades into electrical energy using a generator.

Conclusion

Understanding the difference between reaction and impulse turbines is essential for selecting the right type of turbine for a specific application. Reaction turbines are best suited for low to medium head scenarios, offering high efficiency through the combined action of pressure and velocity changes. Impulse turbines, on the other hand, excel in high head applications, where the energy is derived from the high velocity of fluid jets. By carefully considering factors like head, flow rate, and efficiency, you can choose the right turbine for your power generation needs.

Key Takeaways

• Reaction turbines are ideal for low to medium head applications, operating on pressure and velocity changes.
• Impulse turbines are best for high head scenarios, relying solely on velocity changes for energy conversion.
• Efficiency varies based on the application; reaction turbines perform better in low head, while impulse turbines excel in high head.
• Maintenance is easier with impulse turbines due to their simple design.