What is Reaction Turbine ? Parts, Working, Types Explained in detail [Notes & PDF]

what is reaction turbine

A reaction turbine is a type of turbine used in various applications, including power generation and hydroelectric plants. It operates based on the principle of fluid dynamics, specifically the reaction of moving fluid or gas as it passes through the turbine blades.

Reaction turbine

In a reaction turbine, the fluid (typically steam or water) enters the turbine at high pressure and high velocity. As the fluid flows through the blades, its pressure and velocity gradually decrease, while the turbine’s rotor extracts energy from the fluid to produce mechanical work.

The key characteristic of a reaction turbine is that both pressure and velocity changes occur across the blades. This is in contrast to an impulse turbine, where only velocity changes occur. The pressure drop across the blades in a reaction turbine is accompanied by a reaction force that helps generate torque and drive the rotor.

The design of a reaction turbine typically consists of multiple stages, each comprising rows of fixed and moving blades. The fixed blades, called stator or guide vanes, direct the flow of the fluid and convert its pressure into kinetic energy. The moving blades, called rotor blades, extract energy from the fluid by converting its kinetic energy into rotational motion.

The efficiency of a reaction turbine depends on factors such as the design of the blades, the pressure and velocity of the fluid, and the overall turbine configuration. Reaction turbines are commonly used in power plants where large amounts of energy need to be generated, such as in steam turbines or hydroelectric turbines.

Overall, reaction turbines play a crucial role in converting the energy of fluids into useful mechanical work, making them essential in various industrial and power generation applications.

reaction turbine parts

Reaction turbine parts

The following parts of the Reaction turbine are following:

  • Guide vane
  • Draft tube
  • Spiral casing
  • Runner and
  • Volute

1. Guide Vane: The guide vane, also known as the wicket gate, is an essential stationary component present in reaction turbines. Its primary function is to regulate and control the flow of the incoming fluid or steam towards the runner blades. By strategically positioning the guide vanes, the angle and velocity of the working fluid can be manipulated to optimise the turbine’s performance. The guide vanes are typically adjustable, allowing for precise control over the flow and ensuring that the fluid enters the runner at the most favorable angle for energy conversion. This adjustability enables the turbine to operate efficiently across a range of operating conditions.

2. Draft Tube: The draft tube is a crucial component situated at the exit of the runner in a reaction turbine. Its primary purpose is to convert the kinetic energy of the fluid leaving the runner into pressure energy. The draft tube gradually expands in diameter from the runner outlet to the discharge point, creating a cone-shaped structure. This expansion allows the fluid to decelerate while increasing its pressure, thereby preventing the formation of undesired pressure differences and minimizing energy losses. By efficiently converting kinetic energy to pressure energy, the draft tube helps to improve the overall efficiency and performance of the turbine.

3. Spiral Casing: The spiral casing is a curvilinear casing that surrounds the runner of a reaction turbine. It serves as the outer housing of the turbine and incorporates the guide vanes. The spiral casing is designed to efficiently guide the incoming fluid or steam from the penstock (the pipe that delivers the working fluid to the turbine) towards the guide vanes. Its spiral shape enables a smooth and gradual transition of the fluid from a high-pressure, low-velocity state to a lower-pressure, higher-velocity state as it enters the runner. This gradual transformation minimizes turbulence and associated energy losses, facilitating optimal energy conversion and enhancing the overall efficiency of the turbine.

4. Runner: The runner is the central rotating component in a reaction turbine, often referred to as the “heart” of the turbine. It consists of multiple blades or buckets that are attached to a central hub. The runner is directly driven by the fluid or steam and is responsible for converting the kinetic energy of the working fluid into mechanical energy. As the fluid flows through the runner, it imparts a force on the blades, causing the runner to rotate. The design of the runner blades is optimized to efficiently extract the maximum amount of energy from the fluid. Runners can have different configurations and blade shapes, such as Francis, Kaplan, or Pelton, depending on the specific application and working fluid characteristics.

5. Volute: The volute is a component found in certain types of reaction turbines, particularly in centrifugal or radial flow turbines. It is a spiral-shaped casing that surrounds the runner and aids in the efficient conversion of the fluid’s kinetic energy into pressure energy. The volute serves as a diffuser, gradually expanding in diameter as the fluid flows from the runner outlet to the discharge point. This expansion reduces the fluid’s velocity while increasing its pressure, facilitating a smoother energy conversion process. The volute is designed to minimize turbulence and associated energy losses, thereby promoting optimal efficiency in the turbine and ensuring effective energy extraction from the working fluid.

working principle of reaction turbine

Reaction turbine working principles

A reaction turbine operates based on the principle of Newton’s third law of motion, which states that for every action, there is an equal and opposite reaction. It utilizes the reaction force created when a high-velocity fluid or steam passes through the turbine blades, resulting in the rotation of the turbine runner.

The working principle of a reaction turbine can be understood based on the following explanation:

In a reaction turbine, the rotor consists of a moving nozzle and high-pressure water or fluid is directed through the nozzle. As the water exits the nozzle, it experiences a reaction force, which in turn causes the rotor to rotate at a high speed. This concept helps us comprehend the working principle of the reaction turbine.

The impeller blades within the turbine also experience reaction forces generated by the fluid passing over them. These reaction forces result in the rotation of the impellers. After interacting with the impeller blades, the fluid flows into the grooves and eventually reaches the draft tube, which leads to the tailrace.

By employing a rotor with a moving nozzle and high-pressure water or fluid, we can better grasp the working principle of a reaction turbine. The nozzle receives a reaction force when the fluid is expelled from it, leading to the rotation of the rotor at a high speed. Similarly, in a reaction turbine, the movement of fluid over the runner blades generates a reaction force. This reaction force causes the runner to rotate. Subsequently, the fluid exits the runner blades and enters the draft tube before finally reaching the tailrace.

In summary, the working principle of a reaction turbine involves the generation of reaction forces by the fluid as it passes through the moving components of the turbine. These reaction forces drive the rotation of the rotor or runner, enabling the conversion of fluid energy into mechanical energy.

How does Reaction Turbine works?

Here’s a step-by-step explanation of how a reaction turbine works:

  1. Fluid Intake: The working fluid, which can be water or steam, enters the turbine through an intake pipe called the penstock. The fluid is usually pressurized and possesses kinetic energy.
  2. Guide Vanes: The fluid flows through the spiral casing, where it encounters adjustable guide vanes. These vanes direct the fluid flow towards the turbine runner. By adjusting the position of the guide vanes, the flow rate and direction of the fluid can be controlled, optimizing the turbine’s efficiency.
  3. Runner Blades: As the fluid passes through the guide vanes, it enters the runner, which consists of multiple blades or buckets arranged around a central hub. The high-velocity fluid impinges on the curved runner blades, exerting a force on them.
  4. Reaction Force: Due to the curved shape of the blades, the fluid changes its direction as it flows through them. According to Newton’s third law, the change in direction creates an equal and opposite reaction force on the blades. This reaction force causes the runner and the shaft connected to it to rotate.
  5. Energy Conversion: The rotating runner transfers its mechanical energy to a generator or any other mechanical device connected to it. The kinetic energy of the fluid is converted into mechanical energy as the runner rotates, powering the device it is connected to.
  6. Draft Tube: After passing through the runner, the fluid exits the turbine through a component called the draft tube. The draft tube gradually expands in diameter, allowing the fluid to decelerate and convert its remaining kinetic energy into pressure energy. This process reduces losses and enhances the overall efficiency of the turbine.
  7. Discharge: Finally, the fluid is discharged from the turbine and either returned to the natural water source (in the case of water turbines) or utilized in further processes (in the case of steam turbines).

Overall, a reaction turbine harnesses the energy of a high-velocity fluid or steam by converting its kinetic energy into mechanical energy through the interaction of the fluid with the rotating runner blades. This rotational motion can be utilised to generate electricity, drive machinery, or perform other useful tasks.

Types of Reaction Turbine

There are several types of reaction turbines commonly used in various applications. Here are some of the most prominent types:

  1. Francis Turbine:
    The Francis turbine is one of the most widely used reaction turbines. It is suitable for medium to high head applications. The turbine has a radial flow design, where the water or fluid enters the runner in a radial direction and exits axially. Francis turbines have adjustable guide vanes to control the flow rate and optimize efficiency. They are commonly used in hydroelectric power plants and are capable of operating efficiently over a wide range of heads and flow rates.
  2. Kaplan Turbine:
    The Kaplan turbine is a type of axial flow reaction turbine, specifically designed for low head applications with high flow rates. It features adjustable blades on the runner that allow the turbine to maintain high efficiency across a wide range of operating conditions. Kaplan turbines are commonly used in river-based or tidal power generation projects, where the head is relatively low, but the flow rate is substantial.
  3. Pelton Turbine:
    The Pelton turbine, also known as a Pelton wheel, is a type of impulse reaction turbine. Unlike the Francis and Kaplan turbines, which utilize the reaction force of the fluid, the Pelton turbine extracts energy from the high-velocity jets of water. The water is directed onto a series of spoon-shaped buckets mounted on the perimeter of the runner. The high-velocity water jets strike the buckets, causing the runner to rotate. Pelton turbines are suitable for high head applications and are commonly used in mountainous regions or areas with high elevation differences.
  4. Deriaz Turbine:
    The Deriaz turbine is another type of reaction turbine that falls under the category of axial flow turbines. It is a specialized turbine designed for low to medium head applications. The turbine features a unique runner design with multiple curved blades that provide efficient energy conversion. Deriaz turbines are often used in hydropower projects and industrial applications, where moderate heads and flow rates are involved.
  5. Tubular Turbine:
    The tubular turbine is a reaction turbine commonly used in large-scale hydropower plants. It consists of a cylindrical runner with embedded blades and a spiral casing surrounding it. The water or fluid enters the turbine radially and exits axially, passing through the blades of the runner. Tubular turbines are known for their high efficiency and are suitable for both medium and high head applications.

These are just a few examples of the various types of reaction turbines used in different settings. The choice of turbine type depends on factors such as head, flow rate, available resources, and specific project requirements. Each type of turbine is designed to optimize energy conversion and performance under specific operating conditions.

applications of reaction turbine

Reaction turbines are widely used in various industries and applications due to their efficient and versatile nature. Here are some common applications of reaction turbines:

  1. Power Generation: Reaction turbines are extensively used in power plants to generate electricity. They are typically employed in hydropower plants, where the force of flowing water is utilized to rotate the turbine blades. The water enters the turbine and flows through the blades, causing them to spin and drive a generator, thus converting the kinetic energy of the water into electrical energy.
  2. Steam Power Plants: Reaction turbines are also used in steam power plants, where they are driven by high-pressure steam. The steam flows through the turbine blades, expanding and losing pressure as it passes, which imparts energy to the blades and drives the turbine. These turbines are commonly found in coal-fired, nuclear, and geothermal power plants.
  3. Marine Propulsion: Reaction turbines are employed in marine applications for propulsion purposes. Steam turbines are commonly used in steam-powered ships, where high-pressure steam produced by boilers drives the turbine and propels the vessel forward. Gas turbines, which operate based on the Brayton cycle, are also used in naval and commercial ships for efficient propulsion.
  4. Oil and Gas Industry: Reaction turbines find applications in the oil and gas industry, particularly in gas processing plants. They are used to drive compressors, which enhance the pressure of natural gas to facilitate transportation through pipelines. The turbines are typically powered by the gas itself, with the high-pressure gas expanding through the turbine and driving the compressor.
  5. Chemical Processing: Reaction turbines are utilized in chemical processing industries for various applications, such as driving pumps, compressors, and fans. They are often used to convert the kinetic energy of a fluid stream into mechanical energy, which is then utilized for different processes like mixing, agitation, and pumping.
  6. District Heating and Cooling Systems: Reaction turbines are employed in district heating and cooling systems, where they help generate and distribute thermal energy for residential and commercial buildings. These turbines are typically driven by steam or hot water, and they drive the pumps and fans necessary for circulating the heated or cooled fluid throughout the network.

These are just a few examples of the many applications of reaction turbines. Their efficiency, reliability, and ability to convert fluid energy into mechanical energy make them invaluable in various industries that require the conversion or transfer of power.

advantages of reaction turbine

Reaction turbines offer several advantages compared to other types of turbines. Here are some key advantages of reaction turbines:

  1. High Efficiency: Reaction turbines are known for their high efficiency in converting fluid energy into mechanical energy. They can achieve efficiency levels above 90%, resulting in effective energy conversion and reduced energy losses.
  2. Wide Operating Range: Reaction turbines have a wide operating range, allowing them to efficiently operate under varying load conditions. They can adjust their output to match the changing flow rates of the fluid, making them versatile and suitable for applications with fluctuating operating conditions.
  3. Compact Design: Reaction turbines have a compact design, which makes them suitable for installations with limited space. Their compact size allows for easier integration into existing systems or compact environments, making them a preferred choice in various industrial applications.
  4. Smooth Operation: Reaction turbines provide smooth and stable operation due to their design characteristics. The flow of the fluid through the turbine is evenly distributed over the rotor blades, resulting in reduced vibrations and noise levels. This smooth operation improves the overall reliability and longevity of the turbine.
  5. Flexibility in Fluid Selection: Reaction turbines can work with a wide range of fluids, including water, steam, gases, and even liquids with suspended particles. This flexibility in fluid selection allows for their utilization in various industries and applications.
  6. Scalability: Reaction turbines can be designed and manufactured in different sizes and capacities, making them suitable for small-scale applications as well as large-scale power generation. They can be customized to match the specific requirements of the application, ensuring optimal performance and efficiency.
  7. Low Maintenance Requirements: Reaction turbines are generally known for their low maintenance requirements. They have fewer moving parts compared to other types of turbines, resulting in reduced wear and tear. Additionally, the availability of modern materials and manufacturing techniques further contributes to their durability and reduced maintenance needs.
  8. Environmental Benefits: Reaction turbines, especially those used in renewable energy applications like hydropower, are environmentally friendly. They produce clean and renewable energy without emitting greenhouse gases or other pollutants, contributing to a greener and more sustainable energy generation.

Overall, the high efficiency, compact design, smooth operation, flexibility, and other advantages make reaction turbines a preferred choice in various industries where reliable and efficient power generation or fluid energy conversion is required.

disadvantages of reaction turbine

While reaction turbines offer numerous advantages, they also have a few disadvantages that should be considered. Here are some of the disadvantages of reaction turbines:

  1. Complexity of Design: Reaction turbines have a more complex design compared to impulse turbines. They consist of multiple stages and moving parts, including rotor blades, guide vanes, and seals. This complexity can lead to higher manufacturing and maintenance costs, as well as increased chances of mechanical failures or malfunctions.
  2. Sensitivity to Water Quality: Reaction turbines used in hydropower plants are sensitive to the quality of water entering the turbine. Impurities or solid particles in the water can cause erosion or abrasion of the turbine blades, leading to reduced efficiency and increased maintenance requirements. Water treatment and filtration systems may be necessary to ensure the longevity and optimal performance of the turbine.
  3. Limited Suitable Head Range: Reaction turbines are generally not suitable for low head applications. They require a sufficient head (vertical distance between the water source and turbine) to generate the necessary pressure for efficient operation. Therefore, they may not be suitable for locations with low head conditions, limiting their applicability in certain hydropower projects.
  4. Reduced Cavitation Margin: Reaction turbines are more susceptible to cavitation compared to impulse turbines. Cavitation occurs when the pressure of the fluid drops below its vapor pressure, causing the formation and collapse of vapor bubbles. This can lead to erosion, pitting, and damage to the turbine blades, affecting performance and requiring additional maintenance and repairs.
  5. Lower Starting Torque: Reaction turbines may have a lower starting torque compared to some other types of turbines. This can result in slower start-up times or difficulties in initiating rotation, particularly in large-scale applications. Additional systems, such as auxiliary motors or starting mechanisms, may be required to overcome this limitation.
  6. Higher Sensitivity to Operating Conditions: Reaction turbines can be more sensitive to changes in operating conditions, such as variations in flow rate, pressure, or temperature. Sudden changes or fluctuations in these parameters can affect the performance and efficiency of the turbine. Proper monitoring and control systems are necessary to maintain optimal operation under varying conditions.

It is important to note that the disadvantages mentioned above are general considerations and may vary depending on the specific design, application, and operating conditions of the reaction turbine. Manufacturers and engineers continuously work to address these challenges and improve the performance and reliability of reaction turbines in various industries.

difference between impulse and reaction turbine

Here’s a table outlining the key differences between impulse and reaction turbines:

CriteriaImpulse TurbineReaction Turbine
Working PrincipleUtilizes high-velocity jets of fluid to generate powerHarnesses the reaction force of fluid passing through the blades
Runner DesignPelton wheel or similar designBlades or buckets are fixed on the runner
Flow PathFluid passes through nozzles and strikes bucketsFluid flows over blades or buckets and changes direction
Pressure DropLarge pressure drop across nozzlesModerate pressure drop across the runner
EfficiencyEfficient for high head and low flow rateEfficient for medium to high head and varying flow rate
ApplicationsSuitable for high head applicationsSuitable for a wide range of head and flow rate applications
Example TurbinesPelton turbine, Turgo turbineFrancis turbine, Kaplan turbine, Deriaz turbine, Tubular turbine

It’s important to note that while the table highlights some general differences between impulse and reaction turbines, there may be variations and specific characteristics within each type of turbine depending on design variations and specific applications.

reaction turbine example

1. Francis Turbine: Widely used for medium to high head applications in hydroelectric power plants.

2. Kaplan Turbine: Designed for low head applications with high flow rates, commonly used in river-based or tidal power generation projects.

3. Pelton Turbine: Impulse reaction turbine extracting energy from high-velocity water jets, suitable for high head applications.

4. Deriaz Turbine: Axial flow reaction turbine for low to medium head applications in hydropower projects and industrial applications.

5. Tubular Turbine: Efficient reaction turbine for medium to high head applications, commonly used in large-scale hydropower plants.

Reference : https://www.sciencedirect.com/topics/engineering/reaction-turbine

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