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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 cooling
B
oil cooling
C
air cooling
D
combined cooling
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the use of a poor quality oilB
the deterioration of its propertiesC
the formation of depositsD
the reduction in heat transfer ability
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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
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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
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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
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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 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
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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
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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
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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
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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
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单选题The main purpose of the piston oil scraper rings is to （）.A
seal the space between the piston and the linerB
reduce the amount of lube oil burned in the combustion chamberC
transmit heat from the piston to the cylinder linerD
damp out fluctuations of the piston side thrust
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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
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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
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单选题When students learn apple, orange, the teacher gives students another word fruit.Which principle does the teacher follow in his/her vocabulary teaching?A
Word-choice principle.B
Presentation principle.C
Culture principle.D
Systematic principle.
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Word-choice principle,B
Presentation principle.C
Culture principle.D
Systematic principle.
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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
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单选题Low compression pressure in a diesel engine may be the result of （）A
insufficient fuel supply due to fuel pump valves sticking or leakingB
excessive mechanical clearance between the piston crown and cylinder headC
excessively worn fuel pump plungerD
excessive exhaust back pressure
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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Many cast iron pistons are designed with heat dams, which serve to （）A
keep piston crown temperatures elevated for smoother combustionB
reduce the possibility of overheating the top compression ringC
help retain the heat of compression to prevent ignition delayD
help retain the heat of compression to prevent combustion knock
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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
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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
考题
单选题Piston cooling fins are located（）A
atop the piston crownB
beneath the piston crownC
at the base of the piston skirtD
inside the cylinder liner cooling water jacket
考题
单选题The usual number of single-acting pistons used in a variable stroke axial-piston pump is （）.A
3 or 5B
5 or 7C
7 or 9D
9 or 11
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