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单选题
Small crack in the crankshaft bearing surface of a diesel engine are an indication of()
A
corrosion fretting
B
insufficient lubrication
C
abnormal wear
D
fatigue failure
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更多 “单选题Small crack in the crankshaft bearing surface of a diesel engine are an indication of()A corrosion frettingB insufficient lubricationC abnormal wearD fatigue failure” 相关考题
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An increase in load on a diesel engine results in _____ of speed of the crankshaft.A.a reductionB.an increaseC.an outingD.a downwards
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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
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In a single acting, four-stroke/cycle diesel engine, the power impulse in an individual cylinder occurs ()A
once every crankshaft revolutionB
once every two crankshaft revolutionsC
once every piston strokeD
twice every piston stroke
考题
单选题Diesel engine main and connecting rod precision bearings are made in halvesEach half exceeds one-half the bearing circumference by a small amountThe small amount is termed ().A
clearanceB
crushC
pitchD
thrust
考题
单选题Because the tie bolts are so close to the crankshaft, some engines employ ()to hold the crankshaft main bearing cap in position instead of conventional studs and nuts.A
through boltsB
jack boltsC
tap boltsD
fitted bolts
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A diesel engine which is rated for normal operation at a crankshaft speed of 800 RPM, is commonly classed as a ().A
slow-speed dieselB
medium-speed dieselC
high-speed dieselD
constant-speed diesel
考题
单选题A well-lubricated bearing surface always appears()A
well knurledB
slightly streakedC
lightly glazedD
highly polished
考题
单选题In the management of the shafting, because() carry heavy load and caused high temperature easily, it should be paid attention.A
the bearing near to the diesel engineB
the intermediate bearing near to the thrust bearingC
the intermediate bearing near to the sterntubeD
the bearing located at the middle of the diesel engine and the sterntube
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
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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The camshaft drive is designed to maintain proper camshaft speed relative to crankshaft speedIn maintaining this relationship, the camshaft drive causes the camshaft to rotate at()A
one half crankshaft speed in a two-stroke cycle diesel engineB
crankshaft speed in a two-stroke cycle diesel engineC
two times crankshaft speed in a two-stroke cycle diesel engineD
one-fourth times crankshaft speed in a four-stroke cycle diesel engine
考题
单选题Precision engine bearing inserts are manufactured with a small portion of the bearing ends extending beyond the bearing housing or capsThe installation process of these bearings requires sufficient ().A
overlapB
crushC
lap or leadD
protrusion
考题
单选题Small crack in the crankshaft bearing surface of a diesel engine are an indication of()A
corrosion frettingB
insufficient lubricationC
abnormal wearD
fatigue failure
考题
单选题Proper lubrication of the main bearing is more easily obtained in a single acting four-stroke/cycle diesel engine than in a single acting two-stroke/cycle diesel engine because ()A
bearing pressure in a four-stroke/cycle acting single diesel engine is continually reversedB
bearing pressure in a two-stroke/cycle single acting diesel engine is continually reversedC
the maximum bearing pressure is higher in a single acting two-stroke/cycle diesel engineD
two-stoke/cycle diesel engines require more complicated lubrication piping
考题
单选题Critical speeds occurring within the operating speed range of a main propulsion diesel engine may be changed, or have their damaging effects reduced by a/an ()A
engine support vibration isolatorB
detuner or viscous fluid damperC
lightened crankshaft flywheelD
spherically seated crankshaft bearing
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单选题The crankshaft of diesel engine is supported by ().A
tension stretchB
tie rodsC
through boltsD
main bearings
考题
单选题The bedplate must be rigid enough to support the weight of the rest of the engine, and maintain the crankshaft, which sits in the bearing housings in the (), in alignment.A
longitudinal girdersB
transverse girdersC
fore girdersD
aft girders
考题
单选题Critical speed in diesel engines occurs when engine torque pulsations become ()A
opposed to the crankshaft rocking coupleB
resonant with the crankshaft natural frequencyC
critical fore and aft crankshaft vibrationsD
horizontal whipping motions of the crankshaft
考题
单选题In a single acting, two-stroke/cycle, diesel generator engine, the power impulse in an individual cylinder occurs ()A
once every crankshaft revolutionB
once every two crankshaft revolutionsC
once every piston strokeD
twice every piston stoke
考题
单选题An increase in load on a diesel engine results in () of speed of the crankshaft.A
a reductionB
an increaseC
an outingD
a downwards
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
考题
单选题Lubricating oil used in a diesel engine serves to()A
reduce the wear of bearing surfacesB
cool the bearing surfacesC
assist in sealing bearing surfacesD
all of the above
考题
单选题In a four-stroke/cycle diesel engine, the camshaft rotates at ()A
twice the crankshaft speedB
half the crankshaft speedC
the same speed as that of the crankshaftD
a speed independent of that of the crankshaft
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