Impulse Turbine: Definition, Types, Component, Working Principle, Application, Advantages, Disadvantages

What is Impulse Turbine?

An impulse turbine is a type of steam turbine that uses the force of high-pressure steam to generate rotational energy. The turbine is designed with a series of fixed nozzles or blades, known as guide vanes, that direct the flow of high-pressure steam onto a set of moving blades, called impulse blades, mounted on a rotor. As the steam strikes the impulse blades, it imparts a force that causes the rotor to rotate, generating mechanical energy.

The basic operating principle of an impulse turbine is based on the concept of impulse and reaction. In an impulse turbine, the steam flows through a set of nozzles or guide vanes, which direct the steam onto a set of moving blades. The force of the high-pressure steam hitting the impulse blades generates an impulse force, which causes the rotor to rotate. The rotor, in turn, drives a generator or other mechanical device to generate electricity or perform work.

Impulse turbines are typically used in applications where high-speed rotation is required, such as in small-scale power generation, steam locomotives, and hydroelectric power plants. They are known for their simplicity and reliability and are often used in applications where maintenance and repair are difficult or expensive. However, they are generally less efficient than reaction turbines, which use a more complex design to extract more energy from the steam.

Types of Impulse Turbine:

There are two main types of impulse turbine:

1. Pelton turbine: A Pelton turbine is a type of impulse turbine that is used for high head applications, typically in hydroelectric power plants. It uses one or more nozzles to direct a high-pressure jet of water onto a set of spoon-shaped buckets mounted on a wheel. The force of the water hitting the buckets causes the wheel to rotate, generating mechanical energy.
2. Turgo turbine: A Turgo turbine is a type of impulse turbine that is used for medium head applications. It uses one or more nozzles to direct a high-pressure jet of water onto a set of double-curved blades mounted on a wheel. The force of the water hitting the blades causes the wheel to rotate, generating mechanical energy.

Other types of impulse turbines include the Crossflow turbine, which is used for low head applications and has a vertical axis, and the Banki-Michell turbine, which is used for medium head applications and has a diagonal axis. However, Pelton and Turgo turbines are the most common types of impulse turbines in use today.

Components of an Impulse Turbine:

The main components of an impulse turbine include:

1. Nozzles: Nozzles are small openings in the turbine casing that direct high-pressure steam or water onto the turbine blades. They are designed to accelerate the steam or water to high velocities, which helps to maximize the kinetic energy of the fluid.
2. Guide vanes: Guide vanes are stationary blades that are positioned around the turbine rotor to direct the flow of steam or water onto the turbine blades. They are designed to control the direction and velocity of the fluid entering the turbine, which helps to maximize the efficiency of the turbine.
3. Impulse blades: Impulse blades are a set of moving blades that are mounted on the turbine rotor. They are designed to receive the high-velocity steam or water from the nozzles and convert the kinetic energy of the fluid into rotational energy, which drives the turbine rotor.
4. Rotor: The rotor is the rotating component of the turbine that is driven by the impulse blades. It is typically made of steel or other high-strength materials and is designed to withstand the high stresses and temperatures generated during operation.
5. Shaft: The shaft is a rigid component that connects the rotor to the external load, such as a generator or mechanical device. It is designed to transmit the rotational energy generated by the turbine to the load with minimal loss.
6. Casing: The casing is a large, cylindrical structure that encloses the turbine components and provides a sealed environment for the high-pressure steam or water. It is typically made of steel or other high-strength materials and is designed to withstand the high pressures and temperatures generated during operation.

Other components of an impulse turbine may include bearings, seals, and cooling systems, which are necessary to ensure reliable and efficient operation of the turbine.

Working Principle of Impulse Turbine:

The working principle of an impulse turbine is based on the principle of impulse and reaction. When high-pressure steam or water is directed onto a set of impulse blades, it imparts a force on the blades, causing the rotor to rotate.

The operation of an impulse turbine can be described in the following steps:

1. High-pressure steam or water is directed through a nozzle, which accelerates the fluid to a high velocity.
2. The high-velocity fluid is directed onto a set of guide vanes, which control the direction and velocity of the fluid entering the turbine.
3. The fluid then enters a set of impulse blades, which are mounted on the turbine rotor. The force of the high-velocity fluid hitting the blades generates an impulse force, causing the rotor to rotate.
4. As the rotor rotates, it drives a generator or other mechanical device, generating mechanical energy.
5. The low-pressure fluid exits the turbine and is directed to a condenser or other device to recover the heat energy.

The efficiency of an impulse turbine depends on a number of factors, including the design of the nozzle, the size and shape of the blades, and the speed and temperature of the fluid. The design of an impulse turbine is typically optimized for a specific range of operating conditions, such as steam pressure, temperature, and flow rate, to maximize its efficiency and performance.

Advantages and Disadvantages of Impulse Turbine

Advantages of Impulse Turbine:

1. High Efficiency: Impulse turbines are known for their high efficiency, particularly in high head applications, due to their ability to convert the kinetic energy of the fluid into rotational energy with minimal losses.
2. Simple Design: Impulse turbines have a relatively simple design compared to other types of turbines, which makes them easier to manufacture, operate, and maintain.
3. Durable: Impulse turbines are generally very durable and can withstand high temperatures, pressures, and other extreme operating conditions.
4. Easy to Control: The speed and power output of an impulse turbine can be easily controlled by adjusting the flow rate of the fluid and the size of the nozzle.
5. Suitable for High Head Applications: Impulse turbines are particularly well-suited for high head applications, where the fluid has a high velocity and can generate a significant amount of kinetic energy.

Disadvantages of Impulse Turbine:

1. Limited Applications: Impulse turbines are generally not suitable for low head applications, as the fluid velocity is not high enough to generate significant amounts of kinetic energy.
2. Limited Power Output: Impulse turbines are generally not suitable for large-scale power generation applications, as their power output is limited by their size and design.
3. High Maintenance Costs: Impulse turbines require regular maintenance to ensure reliable and efficient operation, which can be costly and time-consuming.
4. Noise and Vibration: Impulse turbines can generate significant amounts of noise and vibration during operation, which can be a concern in some applications.
5. Limited Control Range: While impulse turbines are easy to control, their control range is limited by the size and design of the nozzle, which can restrict their flexibility in certain applications.

Impulse Turbine Application:

Impulse turbines are commonly used in applications where a high head of fluid is available, such as hydroelectric power generation and certain industrial processes. Some specific applications of impulse turbines include:

1. Hydroelectric Power Generation: Impulse turbines are commonly used in hydroelectric power plants, where water is directed from a high head dam through a turbine to generate electricity.
2. Gas Turbine Engines: Gas turbines typically use an impulse turbine to drive the compressor that compresses the air before it enters the combustion chamber.
3. Steam Turbines: Impulse turbines are also used in steam turbine power plants, where high-pressure steam is directed onto the blades of the turbine to generate electricity.
4. Jet Engines: Jet engines use an impulse turbine to drive the fan that draws air into the engine.
5. Industrial Processes: Impulse turbines can also be used in certain industrial processes, such as in the pulp and paper industry, where steam is used to power various equipment and processes.

Overall, the high efficiency and durability of impulse turbines make them well-suited for a wide range of applications where a high head of fluid is available, and where a simple, reliable, and efficient power source is required.

Difference Between Impulse Turbine and Reaction Turbine

The main difference between impulse turbine and reaction turbine is in the way they extract energy from the fluid flowing through them.

In an impulse turbine, the high-pressure fluid is directed onto a set of stationary nozzles, which convert the pressure energy into kinetic energy, creating a high-velocity jet of fluid that impacts a set of moving blades mounted on the turbine rotor. The impact of the fluid on the blades generates an impulse force, which causes the rotor to rotate. Therefore, impulse turbines are also called velocity turbines.

In a reaction turbine, the fluid flows through a set of fixed blades, known as the stator, which converts the pressure energy of the fluid into kinetic energy, creating a high-velocity jet of fluid that flows over a set of moving blades mounted on the turbine rotor. The interaction between the fluid and the blades generates a reaction force, which causes the rotor to rotate. Therefore, reaction turbines are also called pressure turbines.

Other differences between impulse and reaction turbines include:

1. Design: The design of an impulse turbine is generally simpler than that of a reaction turbine, as there are fewer blades and other components.
2. Efficiency: Impulse turbines are generally more efficient than reaction turbines at high heads of fluid, whereas reaction turbines are more efficient at low heads of fluid.
3. Applications: Impulse turbines are generally used in applications where a high head of fluid is available, such as hydroelectric power generation, while reaction turbines are used in applications where a low head of fluid is available, such as wind turbines.
4. Power Output: Impulse turbines generally have a lower power output than reaction turbines for a given size, due to their smaller number of blades and other components.

In summary, impulse and reaction turbines differ in their design, efficiency, applications, and power output, and are used in different types of power generation systems depending on the availability and head of the fluid being used.

Impulse Turbine Example

One example of an impulse turbine is the Pelton turbine, which is commonly used in hydroelectric power generation. The Pelton turbine consists of a set of stationary nozzles that direct a high-pressure jet of water onto a set of double-cupped buckets mounted on a rotor. The impact of the jet on the buckets generates an impulse force that causes the rotor to rotate, and the rotation is transmitted to a generator to produce electricity.

The Pelton turbine is particularly well-suited for use in high-head hydroelectric power plants, where a large amount of pressure energy is available. The design of the Pelton turbine allows it to efficiently convert the pressure energy of the water into mechanical energy, which can then be used to generate electricity.

Other examples of impulse turbines include the Turgo turbine and the Cross-flow turbine, which are also used in hydroelectric power generation and other applications where a high-head of fluid is available.

Read More: Reaction Turbine: Definition, Types, Component, Working Principle, Application, Advantages, Disadvantages