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单选题
The carbon deposits on the piston crown and in the ring grooves （）.
A
should be scraped
B
should be derusted
C
should be drilled out
D
to be brushed off
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考题
In a diesel engine, when refitting piston rings you should ①check the ring gap at the smallest diameter of the cylinder ②remove carbon from the ring grooveA.①B.②C.①②D.neither ① nor ②
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In a diesel engine, when refitting piston rings you should______. I. check the ring gap at the smallest diameter of the cylinder II. remove carbon from the ring grooveA.I onlyB.II onlyC.both I and IID.neither I nor II
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单选题The lowest ring of a piston is （）.A
a coil springB
a sealing ringC
an oil distributor ringD
main seal ring
考题
单选题“The use of a poor quality oil can lead to rapid deterioration of its properties with the resultant formation of deposits in the piston crown which in turn results in a considerable reduction in heat transfer with subsequent overheating and thermal cracking” According to this sentence, we can know that the principle reason of the overheating and thermal cracking is（）A
the use of a poor quality oilB
the deterioration of its propertiesC
the formation of depositsD
the reduction in heat transfer ability
考题
单选题In some diesel engine designs,（）the injection of cylinder oil is timed to impinge when the piston and only impinge on（）A
is coming upward；cylinder ring beltB
is going downward；piston ring beltC
is coming upward；piston ring beltD
is going downward；cylinder ring belt
考题
单选题A diesel engine piston ring face is in direct contact with the （）.A
top of the ring grooveB
cylinder liner oil filmC
bottom of the ring grooveD
back of the ring groove
考题
单选题The cooling of the piston is carried out by circulating （） across the underside of the crown and inside the ring belt or through specially shaped passages.A
sea waterB
scavenging airC
lubricating oilD
fuel oil
考题
单选题In a diesel engine, when refitting piston rings you should （） Ⅰ.check the ring gap at the smallest diameter of the cylinder Ⅱ. Remove carbon from the ring grooveA
Ⅰ onlyB
Ⅱ onlyC
both Ⅰ and ⅡD
neither Ⅰ nor Ⅱ
考题
单选题A condition contributing to diesel engine piston rings sticking in the ring grooves, is insufficient ring clearance at the ring（） Ⅰ.gap Ⅱ.sideA
ⅠonlyB
Ⅱ onlyC
both Ⅰ and ⅡD
neither Ⅰ nor Ⅱ
考题
单选题Cracking of a diesel piston crown can result from（）A
Excessive piston to liner clearanceB
The underside of the piston crown being excessively dirty lowering the rate of heat transferC
Faulty nozzle sprayD
All of the above
考题
单选题The diameter of a piston is usually less at the crown than at the skirt, in order to （）.A
facilitate the installation of piston ringsB
allow for the expansion of the piston during operationC
prevent crankcase vapors from entering the combustion chamberD
reduce wearing of the upper cylinder liner
考题
单选题The piston crown employs the usual jet-shaker principle with an arrangement of cooling bores in the crown so that the surface temperatures of the crown are moderate with a very even distribution（）A
water coolingB
oil coolingC
air coolingD
combined cooling
考题
单选题Visual inspection of chrome-plated piston compression rings reveals a black ring face at the position of the cylinder liner portsThis condition indicates a ring which（）A
has a crown-faceB
exceeds wear limits through normal wearC
has excessive blow-byD
is in good condition
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单选题In a medium speed diesel engine, a trunk type piston may be cooled by（） Ⅰ.oil circulation though passages in the piston crown Ⅱ.heat transfer through piston rings and liner wallA
Ⅰ onlyB
Ⅱ onlyC
either Ⅰ or ⅡD
neither Ⅰ or Ⅱ
考题
单选题Which of the following characteristic of lube oil helps to reduce the amount of deposits in the piston ring belt during the combustion process in a diesel engine?（）A
Low viscosity indexB
Low carbon forming tendenciesC
High film strengthD
High non-corrosive qualities
考题
单选题Diesel engine piston ring blow-by is usually caused by excessive ring clearance at the ring（）A
backB
sideC
gapD
bottom
考题
单选题The clearance volume for a single stage compressor is defined as the space created between the （）.A
top of the piston and bottom side of head, with the piston at BDCB
piston and head, including the space around the piston to the top of the upper ring and under the valves, with the piston at TDCC
bottom of the piston and bottom side of the head at TDC, regardless of upper ring location and valve placementD
top of the piston and bottom side of the head at TDC as compared to that which exists between the top of the piston and bottom side of head at BDC
考题
单选题In the sentence “In some designs the cylinder oil is timed so that the oil injects only on the piston ring belt, the "piston ring belt" means （）.A
piston crownB
piston ring grooveC
piston skirtD
piston ring area
考题
单选题A condition contributing to diesel engine piston rings sticking in the ring grooves, is insufficient ring clearance at the ring（）A
gapB
sideC
backD
radial
考题
单选题In a large, low-speed diesel engine the clearance between the piston crown and cylinder head is found to be excessiveIn order to correct for this, you should（）A
build up the piston crown by metal sprayingB
build up the cylinder head by metal sprayingC
insert shims between the crankpin bearing box and the connecting rod footD
install a thinner head gasket
考题
单选题Persistent knocking in one cylinder of a diesel engine could be caused by（）.A
a low load on that cylinderB
sluggish piston ring actionC
excessive piston crown coolingD
excessive clearance of piston pin
考题
单选题Why is the ring belt narrower in diameter than the skirt of a piston designed for a diesel engine?（）A
To allow for greater expansion due to higher operating temperatureB
To seal the cylinder against leakage of combustion gasesC
To provide an additional surface for oil coolingD
To provide an additional strength for the crown and lower structure
考题
单选题If the compression rings on a diesel engine piston become stuck in the ring groove, the cause may be due to（）A
excessive ring actionB
excessive ring temperatureC
improper ring rotationD
excessive ring face wear
考题
单选题The sealing function of the piston ring is brought about by the gas pressure above and behind the piston ring, which forces it （） against the bottom of the ring groove, and （） against the cylinder wall.A
upwards；inwardsB
upwards；outwardsC
downwards；inwardsD
downwards；outwards
考题
单选题A diesel engine piston crown can crack from （）A
excessive piston to liner clearanceB
excessive dirt beneath the piston crown that reduces heat transferC
faulty nozzle sprayD
all of the above
考题
单选题If due to thick and hard deposits of carbon, the piston rings cannot move freely in their grooves, dark areas will often appear on the upper part of the cylinder wall (may not be the risible at port inspection)What condition of the piston rings can result in this phenomenon?（）A
micro-seizureB
stickingC
scratchedD
breakage/ollapse
考题
单选题Which of the following conditions would cause carbon deposits to form in the piston ring belt of a diesel engine?（）A
faulty combustionB
excessive ring temperatureC
over lubricationD
all of the above
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