Q3 - Pelton Turbine Flashcards
Explain the purpose of a deflector plate in a Pelton turbine
Deflector Plate - At the outlet of the nozzle, there is a tile diverter which deflects the jet from the impellor blades when the turbine requires to be stopped.
Deflector: After striking the buckets, the water jet exits the runner and is deflected away from it. The deflector helps in preventing water from interfering with the next bucket, allowing the turbine to operate more smoothly.
Draw and label a Pelton turbine and its components. Explain the nozzle and spear rod components and how they effect performance
A Pelton turbine is a type of hydropower turbine designed to extract energy from the flow of water. It is particularly suited for high-head, low-flow conditions. The operation of a Pelton turbine involves several components working together to convert the kinetic energy of water into mechanical energy, which is then used to generate electricity.
Nozzle - The nozzle is equipped with a Doble valve central plug that contains a tapered shape. The valve moving axially, regulates the flow rate through gradually closing of the outlet section.
Spear Rod - This spear rod actuates the doble valve. The spear is driven through by a servo motor and is supplied by fins which reduce the rotational components of the flow
These two components regulate the water flow of the turbine by not changing the external diameter of the water jet, but by decreasing the inner diameter.
Explain the purpose of the Pelton bucket/blade
Buckets: Buckets are the curved blades or cups attached to the runner. They are designed to efficiently capture the kinetic energy of the water jet. The shape of the buckets is crucial for maximizing the energy transfer and overall turbine efficiency.
The bucket has a specific shape to deflect the liquid stream. Due to the variation of the momentum of the water jet, the blade receives a force that makes the impellor rotate. Blades are mounted on a disc integral with the rotary shaft that transmits torque and power
There are usually 18-24 buckets shaped as a double spoon. This number is chosen to avoid the water jet missing on a bucket and leaving the impellor without so.
The bucket is shaped as a double spoon. In the middle, a thin sharp edge called the cutting edge divides the impinging jet between the two spoons. It is inclined at a 1-15 degree angle to optimise the jet action. Each two flows is guided by the blade and is diverted 180 degrees.
At the end of the blade, there is a notch. This notch prevents an incoming blade intercepting the water jet that is working on a previous blade.
It makes the water jet imping the cutting edge perpendicularly.
Write the Euler equation expression for a Pelton Turbine
W= C1 U1 COS@1 - C2 U2 COS@2
U1=U2=U
W=CL U COS@1 - C2 U COS@2
COS@1=0
W=C1U-C2UCOS@2
U = (C1-C2 COS@2)
Describe the trend of work as a function of peripheral speed.
The trend of work as a function of peripheral speed on a Pelton turbine:
There is an optimal range where efficiency and work output is maximised.
Deviation from this range results in a reduced efficiency
Design factors such as blade number and flow rates are specifically designed to ensure optimal range of the peripheral speed
Draw graph
W and u as axis
U= c1/2 C1= square root 2gHa
