Diesel engine mufflers or silencers reduce the engine exhaust noise by （）

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• By far the greatest use is for diesel engine starting using air pressure of 25 bar or more provided by （）.

  A、rotary compressors B、reciprocating compressors C、centrifugal compressors D、screw compressors

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• Excessively worn, or polished ends on a diesel engine valve spring, indicate（）

  A . burned exhaust valves B . excessive spring compression C . spring surge D . worn valve seat

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• The loss of the diesel engine cylinder air charge through leaky valves, piston rings, worn or scored liners, would be indicated by which of the following sets of conditions?（）

  A . Low compression pressure and high exhaust temperature B . Low firing pressure and high exhaust temperature C . Low compression pressure and low exhaust temperature D . Low firing pressure and low exhaust temperature

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• Diesel engines obtain combustion air through turbo chargers，blowers，or（）.

  A . air starters B . carburetors C . natural aspiration D . air receiver

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• A supercharged diesel engine when compared to a similar naturally aspirated diesel engine, will develop an increase in （）

  A . ignition lag B . engine horsepower C . lube oil system pressure D . specific fuel consumptio

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• A two-stroke/cycle diesel engine requires less starting air than a four-stroke/cycle diesel engine, of equal displacement, because the two-stroke/cycle diesel engine（）

  A . has little or no internal friction B . has a lower effective compression ratio C . operates with scavenge air under a positive pressure D . operates without energy absorbing intake and exhaust stroke

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• On a medium-speed main propulsion diesel engine, the crank-pin or crank journal bearings receive lubricating oil from （）.

  A . a spindle lubricator B . an oil jet C . internal splashing D . drilled passages in the crankshaft

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• Diesel engines are considered safer than gasoline engines because（）.

  A . they are more heavily built B . the fuel used is less volatile C . they can be easily reversed D . they operate at a lower speed

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• In a trunk type diesel engine piston, the thickness of the head or crown is determined by the（） Ⅰ.statically balanced Ⅱ.heat dissipation requirement

  A . Ⅰ only B . Ⅱ only C . both Ⅰ and Ⅱ D . neither Ⅰ nor Ⅱ

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• Before shutting off the fuel supply to stop a medium or high–speed diesel engine, why is it necessary to allow the engine to idle for a few minutes?（）

  A . To prevent internal damage form local overheating B . To ensure the fuel nozzles are flushed clean C . To clear the smoke stack D . To let the waste heat boiler reduce its rate of steam generatio

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• The term diesel engine scavenging means（）

  A . delivering more air into the cylinder than it would normally receive during an ordinary charging process B . forcing the products of combustion out of the cylinder with the fresh air charge C . collecting the air charge at the cleaner D . combustion and expansion of hot ga

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• Diesel engine crankshaft deflection readings are generally taken at four crank positionsGood engineering practice requires the deflection gage or indicator to be（）

  A . placed as near the crankpin axis as possible B . removed each time the crankshaft is repositioned C . left in place for all four readings D . reset to zero for all four reading

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• Clogged or partially obstructed exhaust ports on a diesel engine can cause（）

  A . over-speeding of the engine B . failure of the engine to shut down C . no effect of engine mounting bolts D . high exhaust temperature

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• Diesel engine mufflers accomplish noise reduction by （）

  A . reducing exhaust gas velocity B . increasing the frequency of gas vibration C . the use of long head pipes D . the use of zinc electrode

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• Critical speed in diesel engines occurs when engine torque pulsations become （）

  A . opposed to the crankshaft rocking couple B . resonant with the crankshaft natural frequency C . critical fore and aft crankshaft vibrations D . horizontal whipping motions of the crankshaft

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• During the running of the diesel engine, if the supply of cooling water is interrupted or the temperature of cooling water out of the cylinder is too high, the duty engineer should （）

  A . notify the duty officer, reduce the engine speed, take some measures to remove failures B . notify the duty officer and stop the engine immediately, find the cause and remove failures C . notify the C/E D . notify the captai

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• Corrosion inhibitors and/or soluble oils are added to diesel engine cooling systems to （）

  A . maintain low pH in the cooling water B . reduce the cooling water temperature C . increase cooling water hardness D . form a protective film on metal surface

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• All diesel engines are classified as（）.

  A . four cycle B . compression ignition C . vacuum ignition D . external combustio

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• Diesel oil may be used to cool （） of a diesel engine.

  A . cylinders B . exhaust valves C . pistons D . fuel valve

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• The majority of medium speed and high speed marine diesel engines for main or auxiliary drive operate on the （） cycle.

  A . two-stroke B . four-stoke C . long-stroke D . short-stroke

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• Diesel engine exhaust noise can be reduced in an exhaust muffler by （）

  A . changing the direction of exhaust gas flow B . increasing the exhaust gas velocity C . changing the exhaust gas weight D . increasing the exhaust gas static pressure

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• "Scavenging" on a diesel engine means （）.

  A . injecting fuel oil into a cylinder B . removing exhaust gases from the cylinder C . forcing air into the cylinders under pressure after the exhaust valve has dosed D . a combination of all the above

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• 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 isolator B . detuner or viscous fluid damper C . lightened crankshaft flywheel D . spherically seated crankshaft bearing

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• Corrosion inhibitors and/or soluble oils are added to diesel engine cooling systems to __________.

  A.maintain low pH in the cooling water B.reduce the cooling water temperature C.increase cooling water hardness D.form. a protective film on metal surfaces

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