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单选题
The intake ports of a two-strike/cycle diesel engine are opened and closed by the action of the （）
A
camshaft
B
piston movement
C
exhaust valves
D
vertical drive
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Exhaust gases are generally removed from the cylinders of a two-stroke/cycle diesel engine byA.natural aspirationB.masked intake valvesC.air ceilsD.scavenging air
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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
scavenging air
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单选题Intake air flow from a diesel engine turbocharger is directly proportional to engine（）A
exhaust gas pressureB
exhaust gas temperatureC
speedD
load
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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In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressureA
ⅠonlyB
ⅡonlyC
bothⅠand ⅡD
neitherⅠnor Ⅱ
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单选题In order to keep excess oil from the intake ports in two-stroke/cycle diesel engines, （）A
wide compression rings are usedB
oil rings are located above the pistonC
chromium plating is used on all piston ringsD
oil rings are located near the bottom of the piston skirt
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单选题If a single cylinder relief valve on a diesel engine lists frequently while the engine is running, the cause may be an （）A
excessively late injection timing for each cylinderB
incorrectly adjusted intake valve timingC
incorrectly adjusted fuel injectorD
incorrectly adjusted intake valve clearance
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单选题When inspecting piston rings through the ports of a two-stroke/cycle diesel engine, black areas on the sealing surfaces are the result of （）A
insufficient lubricationB
improper piston coolingC
blow-byD
overload operation
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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
of equal importance in a two-stroke/cycle diesel engine as in a four-stroke/cycle diesel engine
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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The intake valves in a diesel engine are reseated by （）.A
cam followersB
push rodsC
combustion gasesD
valve springs
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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In diesel engines, the four basic events (intake, compression, power and exhaust) are performed once in （）.A
two crankshaft revolutions in a two-stroke/cycle engineB
two power strokes in a two-stroke/cycle engineC
one power stroke in a two-stroke/cycle engineD
two piston strokes in a two-stroke/cycle engine
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单选题What is the effect of heated intake air on a diesel engine? （）A
Increases efficiencyB
Increases engine horsepowerC
Increases engine lifeD
Reduces engine horsepower
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单选题A large two-stroke/cycle direct reversing diesel engine is to be reversedPrior to the admission of starting air you must （）A
line up the engine fore restarting with light diesel oilB
reposition the fuel injection camC
change the intake and exhaust valve cam positionsD
place the starting cam in the intermediate position
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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
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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
Piston blow-byC
A defective after-coolerD
Faulty exhaust valves
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单选题The process of scavenging a two-stroke/cycle diesel engine serves to（）A
improve fuel flow volumeB
cool the exhaust valvesC
reduce the intake air charge densityD
increase the temperature of exhaust gases
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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
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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In a naturally aspirated diesel engine, the volume of air intake is directly related to engine （）.A
compression ratioB
valve sizeC
fuel pressureD
cylinder clearance volume
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
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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
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