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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 piston
B
the same size as with a cast iron piston
C
half as large as with a cast iron piston
D
the same size as the crown of an aluminum piston
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考题
Cold weather starting of a diesel engine is more difficult than warm weather starting due toA.use of low viscosity oil in cold weatherB.increased moisture content of inlet air in cold weatherC.increased drag of pistons and bearings due to increased oil viscosityD.higher compression pressures reached due to smaller clearances existing in the engine during cold weather
考题
If clearance between a piston and the cylinder wall is excessive, piston slap will occur. The slap itself is caused by_____.A.alternation of side thrustB.a breakdown of the lube oil film on the cylinderC.worn piston boss piston pin bearingsD.fluctuating gas pressure in tile combustion space
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单选题Abnormal crankpin bearing and piston skirt surface wear indicate（）A
a restricted air intakeB
a clogged connecting rod oil passageC
incorrect connecting rod alignmentD
high cylinder firing temperatures
考题
单选题The （） chamber is enclosed between the cylinder head and piston.A
lubricationB
injectionC
coolingD
combustion
考题
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
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Scuffed cylinder liner wearing surfaces in a diesel engines can result from （）A
chromium plating piston ringsB
knurling the piston skirtC
extended maximum power operationD
applying load to a cold diesel engine
考题
单选题Which of the listed conditions can cause lacquer to be deposited on a piston skirt?（）A
High sulphur content fuelB
High lube oil temperaturesC
High vanadium content fuelD
Excessive piston slap
考题
单选题Oil is supplied to the cylinder wall and （） by means of mechanical lubricators.A
the cylinder coverB
the piston ringsC
the piston crownD
the piston skirt
考题
单选题Cold weather starting of a diesel engine is more difficult than warm weather starting due to（）A
use of low viscosity oil in cold weatherB
increased moisture content of inlet air in cold weatherC
increased drag of pistons and bearings due to increased oil viscosityD
higher compression pressures reached due to smaller clearances existing in the engine during cold weather
考题
单选题Oil control rings used in two-stroke/cycle diesel engines are located near the bottom of the piston skirt in order to （）A
increase the liner area covered by the oil filmB
maintain an oil film on the lower liner where scuffing is prevalentC
keep excess oil away from intake and exhaust portsD
help cushion piston skirt side thrust by providing a hydrodynamic oil wedge
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The function of the piston compression rings used in a diesel engine is to （）A
seal the space between the piston and linerB
transmit heat from the piston to the cylinder linerC
reduce the amount of combustion gas blow-byD
all of the above
考题
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
考题
单选题The gudgeon pin is carried in （） in the piston skirt.A
the bearingB
the crossheadC
bossesD
bridges
考题
单选题Operating a rotary pump at speeds in excess of design requirements could cause（）.A
decreased clearances between rotating partsB
decreased slippage to the suction side of the pumpC
air binding in the discharge portsD
erosion and excessive wear
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In an auxiliary diesel engine, the reason for knurling the piston skirt is to（）A
improve skirt lubricationB
allow for expansionC
transmit forces evenlyD
improve the piston seal
考题
单选题Which of the following statements concerning cylinder liner wear is true?（）A
Liner wear is distributed equally between the upper and lower portions of the cylinderB
Excessive liner wear causes wear between piston ring and grooveC
Excessive, but uniform liner wear will not cause wear between piston ring and grooveD
Liner wear is normally greatest in the middle of the cylinder
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Before replacing a piston you should check the rings to see that all clearances and gaps are within the permissible （）.A
deflectionB
discrepancyC
errorD
tolerance
考题
单选题Before replacing a piston you should check the rings to see that all clearances and gaps are （） the permissible tolerances.A
aboveB
atC
overD
within
考题
单选题Ring groove inserts are occasionally used on aluminum alloy piston to（）A
reduce the ring groove wear rateB
seal against crankcase vaporsC
lessen the wear on aluminum part of the cylinderD
allow for the greater expansion rate of aluminum
考题
单选题If clearance between a piston and the cylinder wall is excessive, piston slap will occurThe slap itself is caused by （）A
alternation of side thrustB
a breakdown of the lube oil film on the cylinder wallC
worn piston boss piston pin bearingsD
fluctuating gas pressure in the combustion space
考题
单选题The cold ocean current which meets the warm Gulf Stream between latitudes 40°and 43°N to form the cold wall is called the（）.A
North Cape CurrentB
Labrador CurrentC
Greenland CurrentD
North Atlantic Current
考题
单选题An aluminum piston has lower inertia and higher coefficient of （） compared to that of cast iron.A
viscosityB
twisting momentsC
inertiaD
thermal expansion
考题
单选题We find that some birds _____ twice a year between hot and cold countries.A
transferB
commuteC
migrateD
emigrate
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