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单选题
The pistons are cooled by （） oil from the forced lubrication.
A
being given
B
giving
C
supplying
D
being supplied
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更多 “单选题The pistons are cooled by （） oil from the forced lubrication.A being givenB givingC supplyingD being supplied” 相关考题
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Which of the following statements concerning the lubrication of diesel propulsionengines used in vessels over 300 gross tons is most accurate? ( )A.Lubrication systems using engine driven lube oil pumps do not require any additionalindependent arrangement when such arrangements have been proven reliable.B.The use of engine driven pre-lube pumps is permitted on vessels with propulsionsystems developing less than 500 shaft horsepower.C.When forced lubrication is used for propulsion engines , one independently drivenstandby pumps is to be provided in addition to the necessary pumps for normaloperation.D.Lubrication systems where two oil coolers are fitted require a minimum of twotemperature control devices which may be actuated by similar sensors.
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Crankcase explosions in propulsion diesel engines result from ____.A.the splashing of lubrication oil by the crankshaftB.the dilution of crankcase oil with particles of combustionC.broken fuel lines spraying oil on the crankcaseD.the ignition of unburned fuel and air in the crankcase
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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
第二组Displacement pumps are those where the volume of the pump chamber is alternately increased to draw the liquid in from the suction pipe and then decreased to force the liquid out into the delivery pipe. Centrifugal pumps are those wherein an impeller rotating at high speed throws the liquid by centrifugal force from the center to the periphery of the impeller where the liquid is discharged through the delivery outlet.Gear pump consists of two or more meshing gears (spur, single or double helical teeth) enclosed m a close-fitted housing. These are used extensively for pumping fuel oil, lubricating oil and hydraulic oil. When gears are unmeshed on the inlet side, a pressure drop occurs that helps the atmospheric pressure acting on the surface of the oil in the reservoir to force it up the pipe to fill the void, the oil is then transferred around the periphery of the pump housing. As the gear teeth mesh again on the outlet side, they form. a seal that prevents oil from backing up to the inlet, the oil in the void is then be forced out into the discharge line.All vane pumps have a rotor driven within a ring (cam ring) by a drive shaft coupled to a prime mover. A cylindrical rotor with sliding vanes, generally in radial slots, rotates within the ring. The center of the rotor is offset from the center of the ring. In a simple vane pump, as the rotor turns, the vanes are forced outward against the inner surface of the cam ring by centrifugal force. This outward radial movement of the vanes and turning of the rotor causes the chamber between the vanes to increase as the vanes pass further away from the inlet port. This increase in volume results in a lowering of pressure until the atmospheric pressure is sufficient to force oil from the reservoir into the inlet chamber. Oil from the inlet is swept away by the vanes toward the outlet port through a decreasing series of chambers until it is forced through the outlet port. A vane pump of balanced design has an elliptical cam ring so that two pumping chambers are formed. This pump is in hydraulically balance, since the two intake and two outlet ports are diametrically opposed to each other. Therefore the side loads exerted on the rotor cancel out, thereby increasing bearing lift and permitting high operating pressure.According to the last sentence of paragraph 1, from where the liquid is discharged through the delivery outlet?A.from the eye of the impellerB.from passage of impellerC.from the periphery of the impellerD.from the impeller
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The common method of applying oil to the cylinder walls is by means of small pump assembled in units, known asA.mechanical lubricatorB.lubrication functionC.forced feed systemD.bearing lubrication
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Crankcase explosions in propulsion diesel engines result fromA.the splashing of lubrication oil by the crankshaftB.the dilution of crankcase oil with particles of combustionC.broken fuel lines spraying oil on the crankcaseD.the ignition of unburned fuel and air in the crankcase
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Lubrication for the main reduction gears used with diesel engines is usually supplied byA.oil from the main engine sumpB.an independent lube oil systemC.the stern bearing head tankD.the stem bearing sump tank
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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
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Large crosshead type engine generally has two lubrication systems, a function performed only by crankcase oil system is（）A
lubricatingB
coolingC
cleaningD
neutralizing
考题
单选题For diesel engine piston cooling, lubricating oil can be supplied to the pistons by a/an （）.A
oil sprayB
oil bathC
oil control ringsD
drilled passage through the camshaft
考题
单选题In a bypass type lubrication system for a diesel engine, the dirty oil line to the centrifuge should be taken from the （）.A
lube oil pump suction lineB
lube oil pump discharge lineC
bottom of the lube oil sumpD
outlet from the lube oil header
考题
单选题Which of the following will be the function of lubricating oil used in marine engines?（）A
to remove heat from oil cooled pistonsB
to wash away wear detritusC
to neutralize acidic productsD
all of the above
考题
单选题In motor-ships, （）, after passing through main and motion bearings and oil cooled pistons, etcis either retained in the bedplate.A
the fuel oilB
the lubricating oilC
the refrigerating oilD
the hydraulic oil
考题
单选题Which of the following conditions indicates the dilution of diesel engine lube oil by fuel oil?（）A
Water discharging from the water outlet of the lube oil purifierB
Fuel oil discharging from the water outlet of the lube oil purifierC
Lube oil discharging from the water outlet of the lube oil purifierD
A change in the lube oil viscosity
考题
单选题Trunk type diesel engine pistons are effectively cooled when heat is（）A
radiated through the engine blockB
transferred to water cooled cylinder wallsC
conducted through the piston crownD
transferred to escaping exhaust gases
考题
单选题Injectors for use with heavy fuel oil must be cooled by either water or light oil to （）A
prevent heat corrosion to internal componentsB
increase fuel delivery rate and economyC
prevent pre-ignitionD
avoid carbonization of the nozzle tips
考题
单选题Crankcase explosions in propulsion diesel result from（）A
the splashing of lubrication oil by the crankshaftB
the dilution of crankcase oil with particles of combustionC
broken fuel lines spraying oil on the crankcaseD
the ignition of unburned fuel and air in the crankcase
考题
单选题On engines having oil cooled pistons the lubricating oil pre-heater must be put into operation and the rate of heating so （） that the temperature of the piston cooling oil returns are 32℃ to 35℃ over a period of at least two hours.A
slowB
quickC
arrangedD
high
考题
单选题The oil quantity for bearing lubrication should be applied in such an amount as to be sufficient to carry away the （） caused by the friction at the bearings.A
acidsB
additivesC
heatD
gear
考题
单选题Trunk-type diesel engine pistons are most effectively cooled by heat（）A
conducted through the engine blockB
conducted to water cooled cylinder wallsC
conducted through the piston crownD
loss to escaping exhaust gases
考题
单选题（）diesel engines generally have two systems of lubrication:（）a total loss system feeding and a circulating system lubricating the running gear and cooling the pistons.A
Large crosshead type；crossheadsB
High speed；the cylindersC
Large crosshead type；the cylindersD
Four-stroke；pistons and cylinders
考题
单选题Which of the following statements concerning the lubrication of diesel propulsion engines used in vessels over 300 gross tons is most accurate?（）A
Lubrication systems using engine driven lube oil pumps do not require any additional independent arrangement when such arrangements have been proven reliableB
The use of engine driven pre-lube pumps is permitted on vessels with propulsion systems developing less than 500 shaft horsepowerC
When forced lubrication is used for propulsion engines, one independently driven stand-by pumps is to be provided in addition to the necessary pumps for normal operationD
Lubrication systems where two oil coolers are fitted require a minimum of two temperature control devices which may be actuated by similar sensors
考题
单选题（） providing lubricating films, oil used in marine diesel engines have to remove heat from oil cooled piston.A
Except forB
BesideC
ExceptD
In addition to
考题
单选题The lubrication to the cylinders affected by the fire must be （）to prevent seizure and all scavenge drains must be （）to prevent the discharge of sparks and burning oil from the drains into the engine room.A
decreased；openedB
decreased；shutC
increased；openedD
increased；shut
考题
单选题The pistons are cooled by oil supplied from the forced （） system.A
fresh waterB
sea waterC
lubricationD
fuel oil
考题
单选题Two important considerations for the proper lubrication of a diesel engine include the delivery of the oil in sufficient amount and the （）.A
cetane numberB
pour pointC
viscosity temperatureD
quality of the oil
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