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单选题
The main bearing metal is a lining （）.
A
inside the bearing
B
outside the bearing
C
covering the crankshaft
D
none of the above
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考题
In an engine with a pot-shaped piston, some lubricating oil from the main bearing will pass along a drilled passage in the crankshaft to the bottom end bearing and then up a connection rod to theA.crossheadB.crankpinC.crank journalD.gudgeon pin
考题
Adjust ______by means of lead wire.A.the clearance of the main bearingB.the diameter of main bearingC.the gap of main bearingD.the tolerance of main bearing
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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On a large low-speed main propulsion diesel engine, lower main bearing wear is usually measured by using a/an （）A
dial indicatorB
outside caliperC
bridge gaugeD
tram rod
考题
单选题The external circumference of a pair of main bearing shells is slightly larger than that of the bore of the housing which receives themThe difference is termed （）.A
nipB
napC
gapD
lip
考题
单选题The main bearing shells often have a thin （） of lead or indium to provide a layer giving protection against corrosion.A
flangeB
flashC
plateD
sheet
考题
单选题Adjust （） by means of lead wire.A
the clearance of the main bearingB
the diameter of main bearingC
the gap of main beatingD
the tolerance of main bearing
考题
单选题Worn main bearing will cause the compression ratio of an auxiliary diesel engine to（）A
increaseB
decreaseC
remain the sameD
increase on compression decrease on expansion
考题
单选题As to the bearing, of the following, which statement is not true?（）A
ff overheat is found, the engine must be stopped for inspectionB
Much heat of the crankcase door indicates that the bearing is overheatedC
If bearing clearance is too large, knocking will be heard in the crankcaseD
If bearing clearance is too large or too small, the white metal may be melted
考题
单选题In an engine with a pot-shaped piston, some lubricating oil from the main bearing will pass along a drilled passage in the crankshaft to the bottom end bearing and then up a connection rod to the （）.A
crossheadB
crankpinC
crank journalD
gudgeon pin
考题
单选题In an engine with a pot-shaped piston, some lubricating oil from the main bearing will pass along a （） in the crankshaft to the bottom end bearing andthen up a connection rod to the gudgeon pin.A
telescopic pipesB
large boreC
drilled passageD
tied rod
考题
单选题Which of the listed bearing types is an example of a solid bearing?（）A
Piston wrist pin bushingB
turbine bearingC
Spring bearingD
Diesel engine main bearing
考题
单选题（） clearances in the main or crank pin bearings will sometimes be indicated by loss of pressure in the lubricating system before any bearing knock is heard.A
Too largerB
Too smallerC
ExcessD
Excessive
考题
单选题The external circumference of a pair of main bearing shells is slightly （） that of the bore of the housing which receives themWhat’s the meaning of “that” in the sentence above?A
less thanB
lighter thanC
larger thanD
smaller than
考题
单选题Measure （） by means of lead wire.A
the clearance of the main bearingB
the play of the miler bearingC
the gap of the main bearingD
the tolerance of the main bearing
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An indirect radar echo is caused by a reflection of the main lobe of the radar beam off the observer’s vessel. Which of the following is NOT a characteristic of indirect echoes?（）.A
Their bearing is almost constant，even when the true bearing of the contact changes appreciablyB
They always appear on a bearing of 90°from the true bearing of the contactC
The indirect echoes usually appear in shadow sectorsD
When plotted，their movements are usually abnormal
考题
单选题In the shafting management （） should be paid more attention. Ⅰ.f the while metal tailshaft bearing is dripping oil Ⅱ.f some area become blue during the running Ⅲ.he deformation of crankshaftA
ⅠB
ⅡC
ⅢD
Ⅱ+Ⅲ
考题
单选题The main bearing shells are made of steel with a lining of bearing metal which may be white metal, copper-lead or aluminum-tin alloy What is the meaning of “which” in the sentence above?（）A
main bearing shellsB
main bearingC
steelD
bearing metal
考题
单选题The main bearings are provided with thin-walled （）, lined with a copper-lead alloy.A
steel guidesB
steel shellsC
steel bearing capsD
pig iron
考题
单选题To determine the main bearing clearance of a propulsion diesel engine, you should measure the main bearing shell using a ball anvil outside micrometer and measure the crankshaft journal using a/an （）A
telescopingB
ring ‘snap’ gaugeC
inside vernier caliperD
outside micrometer
考题
单选题While inspecting the main bearings on a diesel engine you find impregnated dirt and scratches in the bearing surface you would, therefore, suspect that （）A
the bearing had been overheatedB
water was present in the oilC
the lube oil was not being properly filteredD
the maximum allowable bearing pressure had been exceeded
考题
单选题The design of （） is similar to that of the main bearing.A
the block bearingB
the camshaft bearingC
the connecting rod small end bearingD
the connecting rod large end bearing
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