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单选题
The cylinder oil is pumped into the cylinder (via non-return valves) when the piston rings pass the lubricating orifices during （）
A
the upward stroke
B
the downward stroke
C
the power stroke
D
the suction stroke
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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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第二组Under normal operation, some lubrication oil mist may be discharged from the air compressor to the air start system. This oil may be from excess compressor cylinder lubrication, from faulty oil scraper rings, or may even be suspended oil vapor contaminating the engine room atmosphere and drawn in at the compressor suction. Oil discharge is kept to a minimum by draining the after cooler, air receiver and starting system. If small quantities of lubrication oil do get passed into the starting air system, they will deposit as thin moist film over internal pipe surfaces but are not readily combustible. If a cylinder non-return valve leak while the engine is in operation, some hot gas, possibly with unburned fuel and cylinder lubrication oil, may be blown through the valve to the adjacent air manifold. With further heating from the leaky valve, this, together with the already deposited oil film, will carbonize and form. incandescent carbon. If starting air is applied to the system while still hot, the high pressure air coming into contact with the burning carbon may cause an explosion. Such an explosion will cause a flame to pass back through the air start pipe system, evaporating the deposited oil film and igniting it in the presence of air. Very high velocities and shockwaves are generated which may rupture pipes and fittings.Alternatively, if excessive oil has entered the air start system, a mixture of air and oil droplets may be discharged through the open cylinder non-return valve during starting. This spray may ignite due to high temperatures in the cylinder, causing a flame through the still open valve to the air manifold.To prevent an explosion, air start valves must be correctly maintained and lubricated to ensure correct timing and free movement with positive closing. Oil in the system must be kept to a minimum, pipe lines must be drained and cleaned internally when necessary and oil discharge from air compressors must be kept to a minimum by good maintenance.The passage is mainly aboutA.crankcase explosionB.scavenge box fireC.starting air pipeD.the danger of explosion in the starting air system
考题
According to this passage, if the cylinder non-return valve were not leakyA.an explosion would not be causedB.there still would be a danger of explosionC.oil would not deposit in the air pipeD.pipe lines would not have to be drained
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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
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单选题Which of the listed problems would be indicated by an accumulation of water in one cylinder, in addition to the crankcase of an idle diesel engine?（）A
Excessive cylinder linerB
water in the fuel systemC
Cracked cylinder linerD
Leaking lube oil cooler
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单选题Fuel oil discharged to the diesel engine cylinder is atomized at the （）A
turbochargerB
injection nozzle tipC
carburetorD
fuel oil pump
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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
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单选题To function properly, oil control rings used on a diesel engine piston must distribute sufficient oil to all parts of the cylinder wall and must also（）.A
prevent any lubricant from reachingB
prevent excessive lubrication from reaching the combustion spaceC
Provide metal-to-metal contact to seal the cylinder against blow-byD
assure a positive means of scraping carbon accumulation from the cylinder
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单选题In addition to lubricating, cylinder oil assists in forming a gas seal and contains （） which clean the cylinder liner.A
additivesB
waterC
greaseD
acid solution
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单选题In some diesel engine designs,（）the injection of cylinder oil is timed to impinge when the piston and only impinge on（）A
is coming upward；cylinder ring beltB
is going downward；piston ring beltC
is coming upward；piston ring beltD
is going downward；cylinder ring belt
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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
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单选题In some designs the cylinder oil is timed so that the oil injects only on the （）.A
piston crownB
piston grooveC
piston skirtD
piston ring belt
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单选题Cylinder wall temperature, fuel oil supplier, and oil passage （）.A
are interdependentB
are not interdependentC
have nothing to do with each otherD
are independent
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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
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单选题Pressurized air enters the cylinder via the inlet ports and pushes the remaining exhaust gas from the cylinder in a process known as “（）”.A
chargingB
super chargingC
scavengingD
exhausting
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单选题Cylinder oil is a high viscosity mineral oil, with a （） machined to the anticipated sulfur content of the fuel.A
TANB
TBNC
SAND
SBN
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单选题（） is used for cylinder and cylinder head, the salt water is used for cooling the lubricating oil, the fresh water in the coolers and the charging air in the air cooler.A
The fuel oilB
The lube oilC
The sea waterD
The fresh water
考题
单选题Maintaining the proper fuel oil temperature will result in （）A
the elimination of valve wearB
improved atomizationC
a decrease in cylinder blow-byD
an increase in cylinder blow-by
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单选题If it becomes necessary to cutout an individual cylinder of a large, low-speed, main propulsion diesel engine, the fuel to that cylinder should be secured and its （）A
fuel pump should be removed and all connections blanked offB
cylinder oil feed rate should be increased slightly above that used at normal sea speedC
cylinder oil feed rate should be reducedD
cylinder oil feed rate should be increased to the maximum flow capable of the metering pump
考题
单选题A condition that can increase the foaming tendency of lube oil is （）A
excessively high oil temperaturesB
water or moisture contaminationC
fuel dilutionD
life its cylinder relief vales
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单选题Engine coolant accumulating in the diesel engine lubricating oil can result from a （）A
low oil pressureB
high coolant pressureC
leaking fuel injectorD
cracked cylinder head or liner
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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
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单选题The function of diesel engine piston compression rings is to （）.A
prevent piston side thrustB
prevent engine friction lossesC
transmit heat from the piston to the cylinder linerD
remove oil from the cylinder combustion space
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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
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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
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单选题Misfiring in a diesel engine at light loads can be caused by（）A
high lube oil temperatureB
low lube oil temperatureC
excessive cylinder coolingD
high air injection pressure
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