6 - 10 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
pg 8
Peloton wheels:
A) Are usually installed with the shaft vertical
B) Are usually used where head is between 450 and 850 feet
C) Are always used in pairs, with the generator between 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
page 4
Power available at the nozzle varies:
A) Inversely with the head and the quantity of water
B) Inversely with the head and directly with the quantity of water
C) Directly with the head and inversley with the quantity of water
D) Directly with the head and quantity of water
D) Directly with the head and quantity of water
pg 13
Water hammer:
A) May be a nuisance but will not cause any serious change to a penstock
B) Can damage a penstock if not kept within reasonable limits
C) Is more likely to occure in a short penstock than in 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
pg 25
The purpose of the Auxiliary needle is to: water stream
A) Provide a means for reducing flow to an impulse wheel rapidly while reducing the flow more slowly through the penstock
B) Providing 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 develope 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
pg 25
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 slay ring is designed to provide
C) The entire circumference of the runner of the reaction turbine is being acted on by the
D)The impulse wheel must be large enough to permit the use of multiple nozzels
C) The entire circumference of the runner of the reaction turbine is being acted on by the
pg 29
Which of the following would not be found on a reaction turbine?
A) Servomotor
B) Draft Tube
C) Wicket Gates
D) Stripper
D) Stripper
pg 26
For most reaction turbines, greatest efficiency is obtained when the wicket gates are?
A) Wide open
B) 90-100% open
C) 80-90% open
D) 70-80% open
C) 80-90% open
pg 35
Draft tube
A) Is required only for reaction turbines operating under low head
B) Is required only for reaction turbines operating under high heads
C) Increase 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
pg 40
Readings from a pressure gauge placed on top of a crown plate of a reaction turbine givea good indication of what?
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
pg 40
What is the advantage of the Kaplan turbine
A) Is used mainly where heads are over 200 feet
B) The propeller blades adjust automatically to maintaining the best efficiency for gate position and also variations of 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) The propeller blades adjust automatically to maintaining the best efficiency for gate position and also variations of head
pg 52
Net head most nearly means:
A) Gross head plus friction loss
B) Static head plus friction loss
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 tail water 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
pg 57
How much head would be required to develope 10,000 horsepower from a turbine operating at 80% efficiency from a stream with a flow of 100cu.ft/sec?
A) 110 feet
B) 800 feet
C) 880 feet
D) 1,100 feet
D) 1100 ft
E=8.8 P1/Qh
.8=(8.8 x 10,000)/100 x h
.8 x 100h=88,000
80h=88,000
h=1,100
pg 59
What is the best speed of rotation in RPMs for a Pelton wheel 54” in diameter, on which the net head is 625 feet?
A) 160
B) 260
C) 360
D) 460
C) 360
N=(19.1 x U1)/D
N=(19.1 x 120)/54
N=42.44
180=N/60 x π54
N=360 rpm
pg 51
