Previously we learned about Impulse Turbine and Pelton Wheel Turbine. We can even learn about the turbines today but this turbine is used where the water heads are very low or moderate. The Turbine we learn today is Reaction Turbine.
Reaction Turbines are the turbines which are mostly used in generation of Hydro-electric power. Reaction Turbines are commonly used in emergency situations where the water level is low but has a high flow rate. The water from outside comes at right angles on to the blades. Then due to the force power is generated. The reaction turbine can also be used in applications of low level water pressure.
These turbines operate under Hydraulic energy, Pressure energy and a part of Kinetic Energy too. There are mainly two types of Reaction Turbines. They are as follows-
- Radially Outward Flow Reaction Turbine
- Radially Inward Flow Reaction Turbine
Radially Outward based Flow Reaction Turbine-
Most of all the time, we just read the sub heading and grasp the entire concept of the whole paragraph or even a book. Isn’t it? The people who are fluent and proficient in English read the English paper from top to down rather than left to right. The same way when the flow of the Reaction Turbine is radially outward, it is said to be Radially Outward Flow Reaction Turbine. It consists of a Cylindrical disc mounted directly on its shaft. The water flows into the wheel at the center and then glides through radially towards the vanes. The guide vanes are also present which are used to direct the water into the moving vanes in correct direction. It also helps to regulate the amount of water striking the vanes. The wheel gets enclosed by a water tight casing.
Radially Inward based Flow Reaction Turbine-
All the details of the turbine area identically equal to that of Outward Flow Turbine except the way the guide vanes surround the moving vanes. This is mostly preferred when compared to others because of its non-racing capability. In this turbine, the centrifugal force on inward moving water decreases the relative velocity. So the speed of the turbine can be easily controlled without any difficulty.
Working of Reaction Turbines-
The reaction turbine consists of rotor blades that are shaped more likely to aerofoils which are so arranged that the cross sectional area of chambers formed gets diminished from inlet side to exhaust side of the blades. The steam when passed through the chambers, its velocity gets drastically increased which at the same time, its pressure immediately gets reduced just as nozzles formed by some of fixed blades. This will cause a further decrease in pressure in both the fixed and also in the moving blades. So the steam comes out as a jet, creates a reactive force on blade which further causes turning movement of rotor. This is the complete and very clearful explanation of a Reaction Turbine.
Advantages of Reaction Turbine-
- It has an extreme capacity to use high pressures and high temperatures.
- It is a oil free exhaust system.
- Its blade efficiency is very high.
- Very high rotational speed.
- Less space required for the installation.
Disadvantages of Reaction Turbines-
- If gears are implemented it would be possible to vary speed on the requirement.
- The reversibility of steam turbine cannot be prepared.
- It recovers less energy per space.
- The blade tips wear a lot.
- Generates opposite thrust force.