Reaction turbine working principle

In summary, in a reaction turbine, the rotor blades act as convergent nozzles for the steam to accelerate through. This causes a reaction force that drives the rotor. However, due to the direction of the rotor blades, the absolute velocity of the steam decreases even though its velocity relative to the blades increases. This can be seen in the diagram where w3 is greater than w2 but c3 is less than c2. The pressure drop in both the stator and rotor also contributes to the decrease in absolute velocity.
  • #1
Absentee
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Let me start this question with a quote:

"In the reaction turbine, the rotor blades themselves are arranged to form convergent nozzles. This type of turbine makes use of the reaction force produced as the steam accelerates through the nozzles formed by the rotor. Steam is directed onto the rotor by the fixed vanes of the stator. It leaves the stator as a jet that fills the entire circumference of the rotor. The steam then changes direction and increases its speed relative to the speed of the blades. A pressure drop occurs across both the stator and the rotor, with steam accelerating through the stator and decelerating through the rotor."

So: "... reaction force produced as the steam accelerates through the nozzles formed by the rotor," but... "with steam decelerating through the rotor."

What? As i understand it, increasing the velocity of the fluid requires a force to be acted on a fluid, therefore, fluid exerts an equal force and opposite force to drive the rotor.

Therefore, If the reaction turbine acts as a lawn sprinkler, shouldn't velocity in the rotor increase? But somehow, viewing the diagrams I noticed the velocity drops across the rotor blades. If the rotors acts as a converging nozzle then yes, i understand why pressure drops, but i can't understand why velocity drops.

Thanks!
 
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  • #2
The steam velocity relative to the blades is increasing, but because the rotor blades are moving in the opposite direction, it slows down the absolute steam velocity.

In the following image, w are the velocities relative to the rotor blades, c are the absolute velocities and u is the velocity of the blades. w3 > w2, but c3 < c2.

Velocity_triangle_for_an_axial_turbine_stage.jpg
 

1. What is a reaction turbine?

A reaction turbine is a type of turbine that converts the kinetic energy of a moving fluid into mechanical energy. It is used in power plants to generate electricity from water, steam, or gas.

2. How does a reaction turbine work?

A reaction turbine works by using the pressure and kinetic energy of a fluid to rotate the blades of the turbine. As the fluid passes through the blades, its pressure and velocity decreases, causing the blades to rotate and generate mechanical energy.

3. What is the difference between a reaction turbine and an impulse turbine?

The main difference between a reaction turbine and an impulse turbine is the way they convert energy. In a reaction turbine, the fluid's pressure and kinetic energy are both used to rotate the blades, while in an impulse turbine, only the fluid's kinetic energy is used.

4. What are the common applications of reaction turbines?

Reaction turbines are commonly used in hydroelectric power plants, steam turbines, and gas turbines. They are also used in some wind turbines and marine propulsion systems.

5. What are the advantages of using a reaction turbine?

Some advantages of using a reaction turbine include high efficiency, ability to handle a wide range of fluid flow rates, and low maintenance requirements. They are also environmentally friendly and have a long lifespan.

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