Solids Mechanics and hyradaulic machines .pptx

electrical engineering Solid mechanics and Hyradaulic Machines

1. SOLID MECHANICS AND HYRADAULIC MACHINES UNIT-5 TURBINES AND PUMPS CLASSIFICATION OF TURBINES PELTON WHEEL 23RS5A0218 M.POTHANVAAS

2. INTRODUCTION – Pumps and turbines appear many places in hydraulics and other civil and environmental engineering applications – Water supply, distribution and treatment – Power generation Civil and Environmental Engineers need to understand how they work, and how to select appropriate machinery

3. PELTON WHEEL - A Pelton turbine, also known as a Pelton wheel turbine, is an impulse turbine uniquely designed to convert the kinetic energy of water into mechanical energy. Unlike its counterparts – the francis  and kaplan turbines, which are reaction turbines suited for lower-head and higher-flow applications – the Pelton turbine operates efficiently in high-head, low-flow conditions typical of mountainous terrains. It achieves this by directing high-velocity water jets at a series of buckets mounted around the wheel, known as the runner, capturing the water’s momentum with remarkable efficiency.

4. CONSTRUCTION- Buckets The buckets, or impulse blades, are cast into two cup shapes adjacent to each other. These buckets ‘catch’ the water jet and direct the flow gradually backwards. Due to the bucket design, almost all of the kinetic energy from the water is harnessed as torque prior to discharge. Wheel The Pelton wheel is very heavy and acts as a flywheel. A flywheel stores rotational energy and resists changes to rotational speed. The amount of energy stored in the flywheel is the square root of its rotational speed.

5. Drive Shaft The drive shaft connects the turbine runner to the generator, this makes it possible to convert the mechanical energy from the rotating runner into electrical energy. Pelton turbines can be used as prime movers for other rotating assets also e.g. a mechanical pump. Spear/Needle The spear/needle controls the flow of water through the nozzle and thus the amount of force exerted upon the wheel. Not all Pelton wheels have a spear or needle. Spear Adjuster The spear adjuster can be operated manually, electrically or hydraulically. Large Pelton turbines actuate the spear adjuster hydraulically only.

6. WORKING - Water is delivered through a pressurized water conductor known as a penstock. The penstock forms the suction side of the turbine and connects the upper reservoir to the turbine. At the end of the Penstock is a spray nozzle. The spray nozzle converts the potential energy of the water to kinetic energy, this kinetic energy manifests itself as a high velocity jet of water that is sprayed out of the nozzle and towards the Pelton runner buckets. The water jet impacts with the inside surface of each bucket tangentially.

7. Each bucket consists of two halves separated by a high ridge, known as a splitter. The splitter divides the water jet so that the flow to both sides of the bucket is even. A notch on each bucket allows the water jet to flow into each bucket at an optimum angle. The spoon shape of the bucket causes the kinetic energy of the water jet to be converted to mechanical energy gradually, as the water completes a 180-degree turn in the bucket. The mechanical energy manifests itself as torque on the runner shaft, which causes the runner to rotate. After leaving the bucket, the water is discharged through a discharge pit. Because the Pelton runner is connected on a common shaft to a generator, the generator begins to generate electricity as soon as the runner rotates. The generator converts the mechanical energy supplied by the runner to electrical energy, which can then be transferred through an electrical grid to end consumers.

8. ADVANTAGES – They are useful for high jumps and relatively small flow rates. They are more robust. They are less prone to erosion of their buckets. Easier to repair. Very efficient. DISADVANTAGES - Limited operating control

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