Water Turbines and their Characteristics | Civil Engineering Optional Notes for UPSC PDF Download

Water Turbine Defined

• A water turbine is a machine that converts the energy of moving water into mechanical energy or electricity.
• Water turbines were invented in the nineteenth century and have initially been utilized for industrial purposes such as grain milling and water pumping.
• Today, water turbines are used to generate electricity. Dams typically use this energy to generate electricity using the fluid's potential energy. The operational efficiency of modern water turbines exceeds 90%.

Types of Water Turbines

Impulse Turbine

• Impulse turbines alter the velocity of a water jet, and the jet pushes against the curved blades of the turbine, changing the flow direction.
• The momentum change (impulse) exerts a push on the turbine blades. Because the turbine is spinning, the force applies over a longer distance (work), and the redirected water flow has less energy.
• The pressure of the fluid flowing over the rotor blades remains constant in an impulse turbine, and all work output is attributable to changes in the fluid's kinetic energy.
• A nozzle transforms the water's pressure (potential energy) into kinetic energy before focusing on the turbine blades without pressure change. The high-speed water hits the turbine, causing the turbine shaft to start running. The rotating motion of the shaft rotates the generator coil, which generates electricity.

Reaction Turbine

• The combined action of pressure and flowing water generates power in reaction water turbines. The turbine alters the water's pressure, velocity, and direction as it runs past it.
• The water flow creates pressure between the front and rear of the blades, creating a reverse reaction force on the runner and forming rotation torque to rotate the runner.
• The energy contained in piped water is subsequently turned into mechanical or electrical energy via these activities. The reaction turbine must be entirely enclosed to control the water pressure, and the turbine must be submerged in the water flow.
• Reaction turbines are often utilized for lower head and greater flow applications than impulse turbines. At the exit of the reaction, the turbine is an expansion section (the draft tube).
• The draft tube's job is to collect the flow's kinetic energy at the runner's exit and convert it into pressure to recover it. The kinetic energy recovery of the draft tube has a considerable impact on the turbine's efficiency.

Components of A Water Turbine

Runner

• The runner is a wheel-like component that rotates and has blades attached. Water flows over the blades and causes the runner to rotate.
• As the runner rotates, it turns into a generator that produces electricity. The runner must be carefully designed to maximize efficiency.

Wicket Gates

• Wicket gates are located around the circumference of the turbine runner.
• They direct the water flow onto the blades at the proper angle and prevent the water from striking them head-on, damaging them.
• The wicket gates are opened and closed by a governor, controlled by the amount of electricity generated.
• As the electricity demand increases, more water is allowed to flow through the turbine, and vice versa.

Stays

• Stays are horizontal bars that connect the wicket gates to the runner.
• They help to keep the wicket gates in place and distribute the weight of the gates evenly around the runner.

Stay Vanes

• Stay vanes are vertical bars that are attached to the stays.
• They help keep the water flowing smoothly over the blades by directing it towards the runner's center.

Draft Tube

• The draft tube is a cone-shaped tube that is connected to the turbine runner.
• It is located at the bottom of the turbine and helps direct the water flow away from the turbine.

Scroll Case

• The scroll case is a curved housing that encloses the turbine runner and wicket gates.
• It helps direct the water flow onto the blades and prevents them from striking the blades head-on.

Characteristics of Water Turbine

Several characteristics are important to consider when selecting a water turbine for a particular application.
Some of these characteristics include:

• Efficiency: The efficiency of a water turbine is the ratio of the power output to the power input. Water turbines typically have an efficiency of 85-90%.
• Capacity: The capacity of a water turbine is the amount of water that can flow through it per second. Water turbines are typically rated in gallons per minute (gpm).
• Head: The head is the height of the water above the turbine. Water turbines can operate with heads as low as 10 or 1000 feet.
• Pressure: The pressure of the water flowing through the turbine is an important consideration when selecting a water turbine. Water turbines are typically rated in pounds per square inch (psi).
• Temperature: Water turbines are generally designed to operate with temperatures up to 120 degrees Fahrenheit.

Advantages and Disadvantages of Water Turbines

Water turbines have several advantages and disadvantages that should be considered when selecting a turbine for a particular application.
Some of the advantages of water turbines include:

• Relatively efficient and can convert a large amount of the energy in the water into electricity.
• It can be used in a wide range of applications, from small hydroelectric systems to large power plants.
• Easy to maintain and operate.
• Can create small lakes and provide irrigation support, flood control, and clean drinking water.
• Produce zero emissions.

Some of the disadvantages of water turbines include:

• Expensive to install and require a large amount of infrastructure.
• They can be damaged by debris in the water, so they must be protected appropriately.
• They can be noisy, so they must be properly designed to minimize noise pollution.

Applications

Water turbines can be used in various applications, from small hydroelectric systems to large power plants.
Some of the most common applications for water turbines include:

1. Hydroelectric power plants: Water turbines generate electricity in hydroelectric power plants.
2. Irrigation systems: Water turbines can pump water from a lower elevation to a higher elevation.
3. Water treatment plants: Water turbines can pump water into water treatment plants.
4. Manufacturing: Water turbines can be used to power manufacturing facilities.

The Bottom Line

• Water turbines are devices that convert the energy in flowing water into electricity. There are two main types of water turbines: impulse and reaction.
• They are relatively efficient and can be used in various applications, from small hydroelectric systems to large power plants.
• Water turbines are used in various applications, from small hydroelectric systems to large power plants.
• Selection is based on several factors: efficiency, capacity, head, pressure, and temperature.
• Water turbines have several advantages and disadvantages that should be considered when selecting a turbine for a particular application.