2ND 6 Flashcards
Which of the following would not be used with
a Pelton wheel:
a) stripper
b) needle
c) wicket gates
d) servomotor
c) wicket gates
Pelton wheels:
a) are usually installed with the shaft vertical
b) are usually used where the head is between 450 and 850 feet
c) are always used in pairs, with the generator between the two wheels
d) may use two or more jets per wheel to obtain increased power
d) may use two or more jets per wheel to obtain increased power
Power available at the nozzle varies:
a) inversely with the head and the quantity of water
b) inversely with the head and directly the quantity of water
c) directly with the head and inversely the quantity of water
d) directly with the head and quantity of water
d) directly with the head and quantity of water
Water hammer:
a) may be a nuisance but will not cause any serious damage to a penstock
b) can damage a penstock if not kept within reasonable limits
c) is more likely to occur in a short penstock than a long one
d) is a form of pressure wave caused when the load is removed too slowly from a wheel
b) can damage a penstock if not kept within reasonable limits
The purpose of an auxiliary needle is to:
a) provide a means for reducing flow to an impulse wheel rapidly while reducing the flow more slowly through the penstock
b) provide a means for bypassing water when the flow is greater than the main needle can handle
c) provide a second point of impact on the wheel to develop additional power
d) provide emergency service in case the main needle should fail
a) provide a means for reducing flow to an impulse wheel rapidly while reducing the flow more slowly through the penstock
To deliver the same amount of power, a smaller diameter runner is required for a reaction turbine than for an impulse wheel because:
a) the reaction turbine has a lower head requirement
b) the angle of the stay ring is designed to provide additional power to the water stream
c) the entire circumference of the runner of the reaction turbine is being acted on by the water stream
d) the impulse wheel must be large enough to permit the use of multiple nozzles
c) the entire circumference of the runner of the reaction turbine is being acted on by the water stream
Which of the following would not be found on a reaction turbine?
a) servomotor
b) draft tube
c) wicket gates
d) stripper
d) stripper
For most reaction turbines, greatest efficiency is obtained when the wicket gates are:
a) wide open
b) 90 – 100 percent open
c) 80 – 90 percent open
d) 70 – 80 percent open
c) 80 – 90 percent open
A draft tube:
a) is required only for reaction turbines operating under low heads
b) is required only for reaction turbines operating under high heads
c) increases the velocity of discharge at exit from the draft tube
d) increases the effective head of the turbine
d) increases the effective head of the turbine
Readings from a pressure gauge on the crown plate of a reaction turbine give a good indication of the:
a) seal ring effectiveness
b) penstock pressure
c) squeeze applied to wicket gates by the servomotor
d) amount of vacuum on the discharge side of the runner
a) seal ring effectiveness
The Kaplan turbine:
a) is used mainly where heads are over 200 feet
b) propeller blades adjust automatically to maintain best efficiency for gate position and variations in head.
c) has high efficiency only when carrying near maximum load
d) is more similar in principle to the impulse wheel than to the reaction turbine
b) propeller blades adjust automatically to maintain best efficiency for gate position and variations in head.
Net head most nearly means:
a) gross head plus friction losses
b) static head plus frictional losses
c) gross head plus static head
d) gross or static head less the frictional losses in feet
d) gross or static head less the frictional losses in feet
Which of the below factors would not generally contribute to cavitation damage?
a) variation in distance of runner above tailwater level
b) variation in outlet velocity of water from runner
c) frequent load variations
d) little or no variation in effective head
d) little or no variation in effective head
How much head would be required to develop 10,000 horsepower from a turbine operating at 80 percent efficiency from a stream with a flow of 100 cu. ft/sec?
a) 110 feet
b) 800 feet
c) 880 feet
d) 1100 feet
d) 1100 feet
What is the best speed of rotation in rpm for a Pelton wheel 54 inches in diameter, on which the net head is 625 feet?
a) 160
b) 260
c) 360
d) 460
c) 360
