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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 rings
B
allow for the expansion of the piston during operation
C
prevent crankcase vapors from entering the combustion chamber
D
reduce wearing of the upper cylinder liner
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此题为判断题(对，错)。
考题
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B) less than ten inches per year
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考题
单选题The piston rings are manufactured with a diameter （） the bore of the cylinder.A
larger thanB
smaller thanC
equal toD
none of the above
考题
单选题The carbon deposits on the piston crown and in the ring grooves （）.A
should be scrapedB
should be derustedC
should be drilled outD
to be brushed off
考题
单选题Which method listed below is acceptable by classification society to perform hose testing to weather tight hatch covers and closing appliances（）A
This is to be carried out at a maximum distance of 1,5m with a hose pressure not less than 2,0 kgf/cm2. The nozzle diameter is not to be less than 12mm.B
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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 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
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考题
单选题In a trunk type diesel engine piston, the thickness of the head or crown is determined by the（） Ⅰ.statically balanced Ⅱ.heat dissipation requirementA
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Ⅱ onlyC
both Ⅰ and ⅡD
neither Ⅰ nor Ⅱ
考题
单选题The lower end of each piston rod is reduced in diameter to fit a bore in （）, this being secured to the piston rod by a nut.A
the crank-webB
the connecting rodC
the main bearingD
the cross-head
考题
单选题The lower end of each piston rod is reduced in diameter to fit a bore in （）.A
the crossheadB
the journals of the crossheadC
the crosshead shoesD
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考题
单选题The lower end of each piston rod is reduced in diameter to fit a bore in the （）, this being secured to the piston rod by a nut.A
piston gudgeon pinB
piston skirtC
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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
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insert shims between the crankpin bearing box and the connecting rod footD
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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The bore of a diesel engine cylinder describes the （）A
swept volume of the cylinderB
inside diameter of the cylinderC
piston displacement in the cylinderD
length of the piston stroke
考题
单选题The position of the piston parts in relation to each other is secured by means of （） in the crown.A
a markB
a boltC
a dowel pinD
a measuring tool
考题
单选题The lower end of each piston rod is reduced in diameter to fit a bore in the cross-head, this being secured to the piston rod by （）.A
a boltB
a capC
a discD
a nut
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The outside diameter of the pipe is （） the diameter of the bore of the piston rod, the result being that an annular space formed between the piston rod and the pipe.A
less thanB
greater thanC
equal toD
twice larger than
考题
单选题They usually have less money at the end of the month than ______ at the beginning.A
whichB
which wasC
they haveD
it is
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Cold clearances between the skirt of an aluminum piston and the cylinder liner is about （）A
twice as large as with a cast iron pistonB
the same size as with a cast iron pistonC
half as large as with a cast iron pistonD
the same size as the crown of an aluminum piston
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