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单选题
The film of oil between the rings and the liner is not only essential for the lubrication but also （） achieving a gas seal.
A
play a great part on
B
run a role in
C
plays an important part in
D
acts as important part at
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考题
Diesel engine blow-by is the leakage of combustion gases past the( ).A.oil rings onlyB.compression and scraper ringsC.cylinder liner sealingD.cylinder liner ring grooves
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材料：Spark erosion is caused by a voltage discharge between the main bearing and journal surface. The cause of the potential is the development of a galvanic element between the ship’s hull, sea water, and the propeller shaft/crankshaft.The oil film acts as a dielectric. The puncture voltage in the bearing depends on the thickness of the oil film. With increasing engine ratings, the specific load in the main bearing is increased. his will reduce the oil film thickness, and enable the discharge to take place at a lower voltage level.Since the hydrodynamic oil film thickness varies through a rotation cycle, the discharge will take place at roughly the same instant during each rotation cycle, i.e. when the film thickness is at its minimum. The roughening will accordingly be concentrated in certain areas on the journal surface. In the early stages, the roughened areas can resemble pitting erosion. but later, as the roughness increases, the small craters will scrape off and pick up white metal-hence the silvery white appearance.Therefore, to ensure protection against spark erosion, the potential level must be kept at maximum 80 mV, which is feasible today with a high efficiency earthing device. If an earthing device is installed, its effectiveness must be checked regularly. Spark erosion is only observed in main bearings and main bearing journals.问题：According to the paragraph one, a voltage between the main bearing and journal surface is produced by______.A.propeller rotationB.leakage from M/E electric control unitC.a galvanic elementD.friction between the main bearing and journal surface______engine ratings increase, the hydrodynamic oil film between the main bearing and journal surface is______.A.The lower/thinnerB.The higher/the thickerC.The lower/thickerD.The higher/thinnerWhen will the spark erosion take place on the journal surface during each rotation cycle?A.when the film thickness is at its minimumB.when the film thickness is at its maximumC.when the engine is on its compression strokeD.when the engine is on its exhaust strokeDuring the engine room watch keeping, which equipment must be noted to ensure protection against spark erosion?A.the antifouling plantB.the earthing deviceC.the main engine electric heating coilsD.the shaft generator请帮忙给出每个问题的正确答案和分析，谢谢！
考题
单选题Around the combustion chamber, all the main components are to give low thermal strains and the smallest, circumferentially symmetric deformations for good sealing between piston rings and liner（）A
drill cooledB
hole cooledC
tube cooledD
bore cooled
考题
单选题Low compression in a diesel engine can be caused by （）A
clogged coolant passagesB
a leaking cylinder head gasketC
low fuel oil pressureD
worn or broken cylinder liner sealing rings
考题
单选题If the piston groove drain holes for the oil control rings become clogged, which of the following is likely to occur?（）A
The oil control rings will seal improperly and wear rapidlyB
The piston will overheat due to insufficient lubricationC
Excessive oil will remain on the cylinder wallD
Light brown smoke will emanate from the engine exhaust
考题
单选题The primary purpose of oil control rings on a diesel piston is to（）A
provide a reservoir for cylinder lubricationB
pump oil into the combustion space for cylinder coolingC
prevent excessive lubricating oil consumptionD
allow hydraulic oil film formation on the cylinder
考题
单选题The film of oil between the rings and the liner is not only essential for the lubrication but also plays an important part in achieving （）.A
an oil sealB
removing heatC
a gas sealD
cooling the piston
考题
单选题In a diesel engine, excessive cylinder liner wear will cause （） (1) increased blow-by (2) wear between the piston ring and grooveA
(1) only is correctB
(2) only is correctC
both (1) and (2) are correctD
neither (1) or (2) axe correct
考题
单选题Improper cooling of a diesel engine cylinder liner due to the accumulation of scale deposits may cause （）.A
low compression pressureB
increased piston wearC
increased cylinder lube oil consumptionD
poor contact between compression rings and liner
考题
单选题The main function of piston compression rings is to （）A
prevent excessive cylinder liner wearB
reduce friction losses in the engineC
seal the space between the piston and the linerD
limit upward flow of lube oil into the combustion space
考题
单选题The main function of the lubrication system in to enable （） of a film of oil between the moving parts.A
the informationB
the formationC
the scatterD
the friction
考题
单选题Low compression pressure in a diesel engine is caused by（）A
low water in the expansion tankB
improperly seated valvesC
low fuel oil pressureD
worn or broken cylinder liner sealing rings
考题
单选题Diesel engine blow-by is the leakage of combustion gases past the （）A
oil rings onlyB
compression and scraper ringsC
cylinder liner sealingsD
cylinder liner ring grooves
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 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All the rings are slightly rounded on their external top and bottom edges to keep the oil film on the cylinder liner during （） for new piston rings.A
the running-in periodB
the running processC
gas exchange processD
the boiler firing
考题
单选题A single piece（） fitted with bronze rings guides the piston in the cylinder liner.A
piston skirtB
piston crownC
guide wayD
cross-head
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If the piston ring gap remains insufficient when installing new rings, youshould（）A
install oversized ringsB
hone the cylinder liner to allow ring installationC
compress the rings tighter with a compressing toolD
file the ends of the rings
考题
单选题There is a support ring between the cylinder block and collar of the cylinder liner, thus carrying both the liner and the cylinder coverIt also passes to the cooling bores and to the cover（）A
cooling waterB
cooling oilC
refrigerantD
lubricate oil
考题
单选题The function of lubricating oil is to （）A
maintain even distribution of bearing wearB
maintain a constant oil temperatureC
maintain a pressurized film between moving surfacesD
remove entrained water
考题
单选题One of function of diesel engine lubricating oil is to （）A
induce carbon formation on cylinder wallsB
improve fuel penetration in the combustion spaceC
form a friction reducing film between mating surfacesD
lubricate the fuel injection
考题
单选题Piston compression rings used in a diesel engine function to （）A
transfer heat from the cylinder to the pistonB
scrape oil from the sides of the pistonC
seal the combustion space from the crankcasesD
prevent any piston contact with the cylinder liner
考题
单选题In order to keep the oil film on the cylinder liner during the running-in period, the piston rings are slightly rounded（）A
on both the external and internal top edgesB
on both the external top and bottom edgesC
on both the external and internal bottom edgesD
on all the four edges
考题
单选题In a diesel engine, excessive cylinder liner wear will cause （） Ⅰ.increased blow-by Ⅱ.wear between the piston ring and grooveA
Ⅰonly is correctB
Ⅱ only is correctC
both Ⅰ and Ⅱ are correctD
neither Ⅰ or Ⅱ are correct
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Around the combustion chamber, all the main components are bore cooled to give low strains and the smallest, circumferentially symmetric deformations for good sealing between piston rings and liner（）A
thermalB
mechanicalC
plasticD
elastic
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