153 Questions
What is the main function of turbines?
Convert hydraulic energy into mechanical energy
Which type of energy is converted into electrical energy by turbines?
Hydraulic energy
What is the difference between Gross Head and Net Head in turbines?
Gross Head considers friction losses, while Net Head doesn't.
What is the formula for calculating the Net Head in a turbine?
$H - hf$
Which of the following does NOT affect the Net Head of a turbine significantly?
Hydraulic energy input
Why is hydroelectric power generation considered cheaper compared to oil or coal?
Hydroelectric power has lower initial setup costs
What is defined as the ratio of power given by water to the runner of a turbine to the power supplied by the water at the inlet of the turbine?
Hydraulic Efficiency
Which efficiency is defined as the ratio of power at the shaft of the turbine to the power delivered by water to the runner?
Mechanical Efficiency
What is the ratio of the volume of water actually striking the runner to the volume of water supplied to the turbine called?
Volumetric Efficiency
If a turbine is classified based on the direction of flow through the vanes, which classification does it fall under?
Radial flow turbine
In an impulse turbine, what type of energy is available at the inlet?
Kinetic energy only
What does the mechanical efficiency of a turbine signify?
Power delivered by water to the runner compared to power available at the shaft
Which specific speed category do Low specific speed turbines fall under?
Low head turbine
What happens to the power as water flows over the vanes in terms of hydraulic efficiency?
Decreases
Which part of a turbine has power going on decreasing due to hydraulic losses as water flows over the vanes?
Runner of a turbine
What is defined as the ratio of power available at the shaft of the turbine to the power supplied by the water at the inlet of the turbine?
Overall Efficiency
What is the diameter of the jet in the design of a Pelton wheel?
5 times the diameter of the wheel
In a Francis Turbine, what is the ratio of the width of the wheel to its diameter?
0.10 to 0.40
Which turbine is suitable for a large quantity of water at low head?
Kaplan Turbine
What is the purpose of a draft tube in a turbine system?
To discharge water from the turbine outlet to the tail race
What is the flow ratio for a Francis Turbine?
0.15 to 0.30
What does a Kaplan Turbine utilize for energy conversion?
Both pressure and kinetic energy
In what direction does water enter the runner of a modern Francis Turbine?
Radial direction
What does 'hub' or 'boss' refer to in an axial flow reaction turbine?
'Hub' acts as a runner for axial flow turbine
'Vi' refers to what in a Francis Turbine?
'Vi' velocity of whirl at outlet
What happens to the position of the fly-balls in the centrifugal governor when the turbine speed increases beyond normal?
Move upward due to increased centrifugal force
How does the control valve respond to the movement of the sleeve in the system?
Piston rod moves downward, closing valve V and opening valve V1
What is the purpose of decreasing the area of flow of water at the outlet of the nozzle in the relay cylinder?
To reduce the rate of flow of water to the turbine
What happens when the speed of the turbine becomes normal after a decrease in generator load?
The fly-balls return to their normal position
Why does the oil under pressure from the control valve move through valve V to the servomotor?
To exert force on face A of the piston in the relay cylinder
What is the role of the horizontal lever supported over a fulcrum in the system?
Connects sleeve and piston rod of control valve
What type of turbine is known as axial flow turbine?
Radial flow turbine
Which part of the Pelton wheel controls the amount of water striking the buckets?
Nozzle and flow regulating arrangement (spear)
What is the purpose of the casing in a Pelton turbine?
To prevent splashing and discharge water to tail race
What material are the buckets of a Pelton wheel typically made of?
Cast iron, cast steel, bronze, or stainless steel
Which turbine is named after L.A. Pelton, an American Engineer?
Pelton wheel or Pelton turbine
What happens when the spear in the nozzle of a Pelton wheel is pushed forward?
Water flow decreases
What is the function of the breaking jet in a Pelton turbine?
To stop the runner in a short time
What is the shape of the buckets in a Pelton wheel?
Double hemispherical cup or bowl
What does the splitter do in a Pelton wheel bucket?
Divide the jet into two equal parts
What direction does water flow through a radial flow turbine?
From outwards to inwards radially
What is the purpose of using a draft-tube in a reaction turbine?
To convert kinetic energy into useful pressure energy
Without a draft-tube, where does the kinetic energy rejected at the outlet of the turbine go?
It goes to waste into the tail race
What is the main purpose of governing a turbine?
To regulate the rate of flow through the turbine
How is governing of a turbine achieved?
Automatically using a governor
What is the role of an oil pressure governor in governing a Pelton turbine?
Regulating the rate of flow through the turbine
What happens to the speed of a generator when there is a decrease in load?
It increases beyond normal speed
Which type of draft-tube requires less space compared to others?
Simple elbow tubes
What is true about turbines directly coupled to electric generators?
They require governing to maintain constant speed under all conditions
Why does a reaction turbine fitted with a draft-tube have increased efficiency?
As it converts kinetic energy into useful pressure energy
What is the role of a gear pump in governing a Pelton turbine?
Regulating flow through the turbine by oil pressure
What is the main purpose of turbines?
Converting hydraulic energy into mechanical energy
What is the difference between Gross Head and Net Head in a turbine?
Gross Head is the total head available; Net Head accounts for losses such as friction
What does the mechanical efficiency of a turbine signify?
Ratio of useful power output to total energy input
Why is hydroelectric power generation considered cheaper compared to oil or coal?
Hydroelectric power utilizes a free source of energy, water
What is the formula for calculating the Net Head in a turbine?
$H = Hg - hf$
Which efficiency of a turbine signifies the ratio of power delivered by water to the runner to the power available at the shaft?
Hydraulic Efficiency
What is the purpose of the draft-tube in a turbine system?
To establish a negative head at the runner outlet
In the design of a Pelton wheel, what is the diameter of the jet?
$5d$
What is the type of turbine that has water flowing parallel to the axis of shaft rotation?
Axial Flow Turbine
For a Kaplan Turbine, what distinguishes it from a propeller turbine?
Adjustability of vanes
What defines the hydraulic efficiency for a Francis Turbine?
$Vw1u1/gH$
In the design of a Pelton wheel, what is the depth of the buckets?
$1.2d$
What does the flow ratio represent in Francis Turbines?
$Vf1/SQ ROOT of 2gH$
What characterizes an inward flow reaction turbine like the Francis Turbine?
$Vi = 0$ at outlet
What is the speed ratio for a Francis Turbine?
$0.6 to 0.9$
For an axial flow reaction turbine, what part acts as the runner?
'hub' or 'boss'
What type of turbine is a Pelton wheel or Pelton turbine?
Tangential flow impulse turbine
Which part of the Pelton turbine helps to prevent splashing of water and discharge water to the tail race?
Casing
What is the purpose of the breaking jet in a Pelton turbine?
To stop the runner quickly
What material are the buckets of a Pelton wheel typically made from?
Cast steel or bronze
What allows the jet of water in a Pelton wheel to get deflected through 160° or 170°?
Splitter shape
What happens when the spear in the nozzle of a Pelton wheel is pushed back?
Water striking the runner increases
Which part of a Pelton turbine does not perform any hydraulic function?
Casing
What is provided to control the amount of water striking the runner in a Pelton turbine nozzle?
Spear
Which part of a Pelton wheel divides the jet of water into two equal parts?
Splitter
What kind of flow does a Pelton turbine utilize?
Tangential flow impulse
What happens to the speed of the generator when the load on the generator decreases?
The speed of the generator increases.
What is the formula for calculating Hydraulic Efficiency?
Power delivered to runner / Power supplied at inlet
What effect does the movement of the fly-balls in the centrifugal governor have on the sleeve?
The sleeve moves upward.
What does Mechanical Efficiency represent in a turbine system?
The power at the shaft of the turbine in relation to power delivered by water to the runner
Which turbine classification is based on the direction of flow through the runner?
Radial flow turbine
How does the control valve respond when the sleeve in the system moves downward?
The control valve opens.
What is the immediate effect of opening valve V, in the relay cylinder system?
Increase in water flow to the turbine.
What does Volumetric Efficiency measure in a turbine?
The volume of water actually striking the runner in relation to volume supplied
Why does the lever turn about the fulcrum when the sleeve moves in the system?
To close valve V
How is Overall Efficiency defined in a turbine system?
Ratio of power available at the shaft to power supplied at the inlet
In a reaction turbine, what happens to pressure energy as water flows through the runner?
Pressure energy decreases as kinetic energy increases
What is the primary role of the centrifugal governor in this turbine system?
To control generator speed
What differentiates Impulse and Reaction turbines based on energy at the inlet?
'Impulse turbines have only kinetic energy; Reaction turbines have kinetic and pressure energy.'
'Hub' or 'boss' in an axial flow reaction turbine refers to what component?
'The rotating part with fixed vanes'
What specific speed category do Medium specific speed turbines fall under?
Medium specific speed turbine
What is the purpose of a draft-tube in a reaction turbine?
To convert kinetic energy into useful pressure energy
What is the governing of a turbine defined as?
Keeping the speed of the turbine constant under varying load conditions
Which type of draft-tube is considered most efficient?
Conical draft-tubes
What is the role of a gear pump in governing a Pelton turbine?
Ensures proper oil pressure for governing operations
Why is governing of a turbine necessary when it is directly coupled to an electric generator?
To keep the speed of the generator constant under fluctuating load conditions
What does governing of a Pelton turbine involve?
Maintaining constant turbine speed with changing loads
What happens to the pressure at the outlet of the runner in a reaction turbine without a draft-tube?
It remains equal to atmospheric pressure
What is the main function of turbines in a hydroelectric power plant?
To generate electrical energy efficiently
What type of turbine is suitable for large quantities of water at low head?
Kaplan Turbine
Which part of a Pelton turbine controls the amount of water striking the buckets?
Nozzle needle or spear rod
What is the primary function of turbines in a hydroelectric power plant?
Convert hydraulic energy into mechanical energy
In a turbine system, what is the Gross Head defined as?
Difference between head race level and tail race level with no water flowing
What is the Net Head in a turbine system primarily affected by?
Head loss due to friction between penstocks and water
Which efficiency of a turbine signifies the ratio of power delivered by water to the runner to the power available at the shaft?
Hydraulic Efficiency
What is the formula for calculating the Net Head in a turbine system?
$H = H_g - h_f$
Which part of a Pelton turbine is responsible for controlling the amount of water striking the buckets?
Splitter
What happens to the speed of the turbine when the load on the generator decreases?
It increases
How does the centrifugal governor respond to an increase in turbine speed?
The fly-balls move upward
What is the role of the oil pressure governor in controlling the turbine speed?
Maintains turbine speed
How does the movement of the fly-balls in the centrifugal governor impact the control valve?
Opens valve V
What effect does increasing the rate of flow of water to the turbine have on turbine speed?
Increases turbine speed
How does a decrease in generator load affect the rate of flow of water to the turbine?
Decreases flow rate
What is the mathematical representation of Hydraulic Efficiency?
Power delivered to the runner / Power supplied at the inlet
What does Volumetric Efficiency represent?
Volume of water actually striking the runner to volume of water supplied to the turbine
What classification is based on the direction of flow through the vanes of a turbine?
Runner direction classification
Which type of turbine has the water completely enclosed in an air-tight casing?
Reaction turbine
What is the role of Overall Efficiency in a turbine system?
To evaluate total efficiency
Which parameter does Mechanical Efficiency measure in a turbine system?
Power available at the shaft
What distinguishes High Head, Medium Head, and Low Head turbines?
Head classification
How are hydraulic losses primarily incurred in a turbine system?
Due to non-smooth vanes
Which part of a turbine system has slightly less volume of water striking it than supplied?
Runner
What differentiates Impulse and Reaction turbines based on energy transfer?
Kinetic energy throughout for Impulse, pressure energy conversion for Reaction
What is the function of the draft tube in a turbine system?
To guide the flow of water from the runner to the tail race
What characterizes a Francis Turbine in terms of water discharge at the outlet?
Radial discharge
What is the main purpose of a splitter in a Pelton wheel design?
To divide the water jet
What is the ratio called that represents the width of the wheel compared to its diameter in Francis Turbines?
N ratio
In a Kaplan Turbine, what differentiates it from a Propeller Turbine?
The adjustability of vanes
What is the design flow ratio for Francis Turbines?
$Vf1/SQ ROOT of 2gH$
What does the speed ratio represent in Francis Turbines?
Ratio of speed at inlet to square root of 2gH
In an Axial Flow Reaction Turbine, what does the hub act as?
Runner for the turbine
What is the significance of zero whirl velocity at the outlet (Vi) in a Francis Turbine?
Indicates radial discharge at outlet
What type of turbine is a Pelton wheel?
Axial flow turbine
Which part of a Pelton turbine controls the amount of water striking the buckets?
Nozzle and flow regulating arrangement
What does the spear in the nozzle of a Pelton wheel control?
Amount of water striking the runner
What material are the buckets of a Pelton wheel primarily made of?
Stainless steel
What is the function of a breaking jet in a Pelton turbine?
Stop the runner quickly
What is the primary purpose of the casing in a Pelton turbine?
Prevent water splashing and discharge to tail race
What is the specific classification of a turbine where water flows from inwards to outwards radially?
Outward radial flow turbine
What happens when a spear in the nozzle of a Pelton wheel is pushed forward?
Reduces the amount of water striking the runner
What part of a Pelton wheel does NOT perform any hydraulic function?
Casing
What does a splitter do in a Pelton wheel bucket?
Splits the jet into two parts
What is the purpose of a draft-tube in a reaction turbine system?
Increases the efficiency of the turbine
How does the use of a draft-tube impact the net head on a reaction turbine?
Increases the net head on the turbine
Which type of draft-tube is considered most efficient among the commonly used ones?
Conical draft-tubes
What is the governing of a turbine defined as?
Regulating the rate of flow through the turbines according to changing load conditions
Why is governing of a turbine necessary in hydroelectric power plants?
To maintain constant speed of the generator under varying load conditions
How is governing of a Pelton turbine typically achieved?
By adjusting oil pressure using a governor system
What part of a Pelton turbine plays a key role in governing by controlling water flow?
The control valve or distribution valve
Which scenario describes what happens when governing adjusts due to decreasing load on a hydroelectric generator?
The speed of both generator and turbine increase
What part is responsible for driving the gear pump in governing a Pelton turbine?
The power obtained from turbine shaft
In hydroelectric power generation, why is maintaining constant speed of the generator important?
To ensure power generation is at optimal levels
Learn about turbines which convert hydraulic energy into mechanical energy to produce hydroelectric power, the cheapest form of electricity generation. Understand how the mechanical energy is then converted into electrical energy using an electric generator.
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