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单选题
In a four-stroke/cycle diesel engine, badly worn intake valve guides can cause excessive（）.
A
exhaust pressure
B
exhaust temperatures
C
cooling water temperatures
D
lube oil consumption
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Proper lubrication of the main bearings is more easily obtained in a single acting, four-stroke/cycle diesel engine than in a tow-stroke/cycle diesel engine because________.A.The direction of pressure on the journal in four-stroke engine is continuouslyB.positive feed lubricators are installed on all bearings of four-stroke engine, whereas as a splash feed system is used on tow-stroke engineC.four-stroke engines usually utilize a heavier grade of oil than tow-stroke enginesD.Low-stroke engines usually consume less lube oil than four-stroke engines
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If all other conditions such as bore, stroke, speed, and mean effective pressures are equal, a two stroke/cycle diesel engine will develop approximatelyA.the same indicated horsepower as a four-stroke/cycle engineB.twice the indicated horsepower as a four-stroke/cycle engineC.one half the indicated horsepower as a four-stroke/cycle engineD.one power stroke for every two crankshaft revolutions
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During the valve overlap period, the exhaust pressure of a turbocharged four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure ______.A.effective cylinder scavenging and coolingB.constant pressure from the turbochargersC.cooler operation of the exhaust systemD.effective constant pressure for turbocharger operation
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单选题Exhaust gases are generally removed from the cylinders of a two-stroke/cycle diesel engine by（）A
natural aspirationB
masked intake valvesC
air cellsD
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单选题In a four-stroke cycle diesel engine the intake valves open （）A
before TDC and close after BDCB
after TDC and close after BDCC
before TDC and close before BDCD
after TDC and close before BDC
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单选题Air motion is induced in a four-stroke/cycle diesel engine cylinder to improve air fuel mixing, and is known as（）A
superchargingB
scavengingC
turbulenceD
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单选题The size of the exhaust valve opening is （）A
most critical in a four-stroke cycle diesel engineB
most critical in a two-stroke/cycle diesel engineC
most critical in a four-stroke/cycle diesel engine if it is turbochargedD
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单选题Proper lubrication of the main bearings is more easily obtained in a single acting, four-stroke/cycle diesel engine than in a tow-stroke/cycle diesel engine because（）.A
The direction of pressure on the journal in four-stroke engine is continuouslyB
positive feed lubricators are installed on all bearings of four-stroke engine, whereas as a splash feed system is used on tow-stroke engineC
four-stroke engines usually utilize a heavier grade of oil than tow-stroke enginesD
Low-stroke engines usually consume less lube oil than four-stroke engines
考题
单选题Worn diesel engine intake valve guides can result in （）A
increased engine breathing efficiencyB
excessive valve lashC
excessive lube oil consumptionD
lower than normal fuel consumption
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单选题During the valve overlap period, the exhaust pressure of a turbochargers, four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure （）A
effective cylinder scavenging and coolingB
constant pressure from the turbochargersC
cooler operation of the exhaust systemD
effective constant pressure for turbocharger operation
考题
单选题Proper lubrication of the main bearing is more easily obtained in a single acting four-stroke/cycle diesel engine than in a single acting two-stroke/cycle diesel engine because （）A
bearing pressure in a four-stroke/cycle acting single diesel engine is continually reversedB
bearing pressure in a two-stroke/cycle single acting diesel engine is continually reversedC
the maximum bearing pressure is higher in a single acting two-stroke/cycle diesel engineD
two-stoke/cycle diesel engines require more complicated lubrication piping
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单选题Scavenging in a four-stroke/cycle diesel engine occurs during the （）.A
last part of the exhaust stroke, and the first part of the intake strokeB
last part of the intake stroke onlyC
early part of the injection stroke onlyD
early part of the power stroke
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单选题Which of the following statements is true regarding the installation of piston rings on two-stroke/cycle, diesel engines as compared to four-stroke/cycle, diesel engines?（）A
In a two-stroke/cycle engine, the rings run hotter, requiring the end gap to be greaterB
Some provision must be made in a two-stroke/cycle engine to keep the rings from binding in the portsC
No gap is required to exist between the ends of the ring when cold in a two-stroke/cycle engine, but a small gap is required in a four-stoke/cycle engineD
The gaps should be staggered on either side of a piston in a two-stroke/cycle engine, while staggering is not necessary in a four-stroke/cycle engine
考题
单选题If all other conditions such as bore, stroke, speed, and mean effective pressures are equal, a two-stroke/cycle diesel engine will develop approximately（）A
the same indicated horsepower as a four-stroke/cycle engineB
twice the indicated horsepower as a four-stroke/cycle engineC
one half indicated horsepower as a four-stroke/cycle engineD
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单选题Any increase in the exhaust back pressure of a four-stroke/cycle diesel engine will （）.A
reduce engine horsepower outputB
aid in silencing the exhaust noiseC
increase the mean effective pressureD
contribute to effective cylinder scavenging
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单选题A two-stroke/cycle diesel engine requires less starting air than a four-stroke/cycle diesel engine, of equal displacement, because the two-stroke/cycle diesel engine（）A
has little or no internal frictionB
has a lower effective compression ratioC
operates with scavenge air under a positive pressureD
operates without energy absorbing intake and exhaust strokes
考题
单选题The speed of the turbocharger for a four-stroke/cycle diesel engine driving a generator at constant speed depends on the （）A
engine speedB
kilowatt loadC
fuel injection pressureD
air intake manifold temperature
考题
单选题Which of the following conditions can cause above normal air temperature to develop in the intake manifold of a four-stroke/cycle turbo-charged diesel engine?（）A
Clogged air intake faltersB
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Faulty exhaust valves
考题
单选题During which of the listed piston stroke of a four-stroke/cycle diesel engine, is the piston moving downward?（）A
Intake strokeB
Compression strokeC
Exhaust strokeD
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考题
单选题Fuel oil begins injection into the cylinder of a four-stroke/cycle diesel engine during the （）.A
intake strokeB
exhaust strokeC
power strokeD
compression stroke
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单选题For a given size engine, the two-stroke/cycle diesel engine will deliver more power than a four-stroke/cycle diesel engine because （）.A
it has a longer power strokeB
more air gets into the cylinder each strokeC
it develops twice as many power strokes at the same speedD
higher combustion pressure is developed
考题
单选题If a four-stroke/cycle diesel engine is started by injecting air into the cylinder, the pistons receiving the charge of starting air must be（）A
on the power strokeB
on the exhaust strokeC
at the end of the power strokeD
at the start of the intake stroke
考题
单选题A turbocharged, four-stroke/cycle diesel engine has a larger valve overlap than a naturally aspirated four-stroke/cycle diesel engine, in order to in crease the （）.A
temperature of the exhaust gasesB
energy supplied to the turbochargerC
air pressure to the intake manifoldD
purge of exhausted gases from the cylinders
考题
单选题The camshaft on a four-stroke/cycle diesel engine provides a means to operate the （）.A
fuel injectorsB
exhaust valvesC
intake valvesD
all of the above
考题
单选题In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to（）.A
produce a scavenging effect in the combustion spaceB
equalize cylinder and exhaust manifold pressuresC
alleviate the difference in valve size between the intake and exhaustD
flush out condensate that collects after each compression stroke
考题
单选题A piston in a four-stroke/cycle diesel engine makes four strokes during each （）.A
crankshaft revolutionB
mechanical cycle of operationC
period of two combustion cyclesD
cycle of two events
考题
单选题The intake ports of a two-strike/cycle diesel engine are opened and closed by the action of the （）A
camshaftB
piston movementC
exhaust valvesD
vertical drive
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