Short Answer:

A reaction turbine is a type of steam turbine in which steam expands continuously while passing through both fixed and moving blades. The blades act as nozzles, and the pressure of steam decreases in every stage, producing both impulse and reaction forces that rotate the turbine shaft. Unlike an impulse turbine, steam expansion occurs gradually across the blades.

Reaction turbines are commonly used in modern power plants because of their high efficiency and ability to produce large amounts of power smoothly. They work on both impulse and reaction principles, making them ideal for continuous and steady power generation.

Detailed Explanation :

Reaction Turbine

A reaction turbine is a steam turbine that operates by utilizing both the impulse and reaction forces of steam. In this type of turbine, steam expansion takes place in both stationary and moving blades. As the steam passes through each row of blades, its pressure drops and velocity changes, which produces a continuous force on the moving blades. This force causes the turbine rotor to spin and convert steam energy into mechanical energy.

The reaction turbine is commonly used in thermal and nuclear power stations where efficiency and steady operation are essential. It is an improvement over the impulse turbine because it makes better use of the energy of steam through gradual expansion and continuous energy transfer.

Working Principle

The working principle of a reaction turbine is based on Newton’s third law of motion – “For every action, there is an equal and opposite reaction.” In this turbine, steam enters the stationary blades (fixed blades), where its direction and velocity are changed. It then passes over the moving blades, where it expands further, causing a pressure drop. As the steam expands in the moving blades, it exerts a reactive force that drives the rotor.

Thus, both impulse and reaction forces work together:

The impulse force is created when the high-velocity steam from the fixed blades strikes the moving blades.
The reaction force is generated when steam expands within the moving blades.

The combined effect of these forces produces the rotation of the turbine shaft.

Main Components of Reaction Turbine

Fixed Blades (Nozzles):
The stationary blades are attached to the casing. They guide the steam to the moving blades at a proper angle and partially convert pressure energy into kinetic energy.
Moving Blades:
The moving blades are attached to the rotor. Steam expands and changes direction in these blades, producing both impulse and reaction forces.
Rotor (Shaft):
The shaft carries the moving blades and transfers the generated mechanical power to the generator or machine.
Casing:
It encloses all the parts and keeps the steam pressure inside the turbine.
Bearings and Seals:
Bearings support the shaft and ensure smooth rotation, while seals prevent steam leakage.

Working Process Step-by-Step

Steam Entry:
High-pressure steam from the boiler enters the fixed blades of the turbine.
Expansion in Fixed Blades:
The steam expands slightly in the stationary blades, converting some pressure energy into kinetic energy and directing the flow toward the moving blades.
Expansion in Moving Blades:
When the steam strikes the moving blades, it further expands and changes direction. The pressure drops continuously, and the combined effect of impulse and reaction causes the rotor to rotate.
Energy Conversion:
The steam’s energy is gradually converted into mechanical energy through multiple stages, producing smooth and efficient operation.
Exhaust of Steam:
After doing work, the steam leaves the turbine and is condensed in a condenser for reuse.

Features of Reaction Turbine

Steam expands both in fixed and moving blades.
There is a continuous pressure drop across all stages.
The turbine works on both impulse and reaction principles.
High efficiency due to gradual expansion.
Generally used for large-scale power generation.

Types of Reaction Turbine

The main type of reaction turbine is the Parsons Turbine, which is a multi-stage, axial-flow reaction turbine. It is widely used in thermal and nuclear power plants. The expansion of steam takes place in several stages to achieve higher efficiency and smoother operation.

Advantages of Reaction Turbine

High efficiency under steady load conditions.
Smooth and vibration-free operation.
Suitable for large power plants and continuous operation.
Efficient utilization of steam energy through gradual expansion.
Less wear and tear due to balanced forces on blades.

Disadvantages of Reaction Turbine

Complex design and manufacturing.
More expensive than impulse turbines.
Requires accurate sealing to avoid steam leakage.
Difficult to maintain due to more components.

Applications of Reaction Turbine

Widely used in thermal power plants for electricity generation.
Used in nuclear power plants for high-efficiency energy conversion.
Suitable for marine propulsion systems.
Used in industrial processes requiring continuous power supply.

Comparison with Impulse Turbine (for Understanding Only)

In an impulse turbine, pressure drop occurs only in nozzles, while in a reaction turbine, pressure drops in both fixed and moving blades.
Reaction turbines have higher efficiency but more complex design.
Impulse turbines are suitable for small power outputs, while reaction turbines are used for large-scale generation.

Conclusion

In conclusion, a reaction turbine is a highly efficient and continuously operating turbine where steam expands both in stationary and moving blades. The combined impulse and reaction forces drive the rotor and produce mechanical energy. Due to its ability to use steam energy more effectively, the reaction turbine is preferred in most modern power plants. Although it has a more complex design, its high efficiency, smooth operation, and reliability make it essential for large-scale and long-term power generation.