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During the valve overlap period, the exhaust pressure of a turbocharged four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure ______.
A.effective cylinder scavenging and cooling
B.constant pressure from the turbochargers
C.cooler operation of the exhaust system
D.effective constant pressure for turbocharger operation
参考答案
更多 “ During the valve overlap period, the exhaust pressure of a turbocharged four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure ______.A.effective cylinder scavenging and coolingB.constant pressure from the turbochargersC.cooler operation of the exhaust systemD.effective constant pressure for turbocharger operation ” 相关考题
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Any increase in the exhaust back pressure of a four-stroke/cycle diesel enginewill( ).A.reduce engine horsepower outputB.aid in silencing the exhaust noiseC.increase the mean effective pressureD.contribute to effective cylinder scavenging
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单选题The period of valve overlap is when （）.A
the inlet valve is openB
the exhaust valve is openC
both valves are closeD
both valves are open
考题
单选题Valve overlap is the period during which （）.A
the inlet valve is openB
the exhaust valve is openC
both valves are closedD
both valves are open
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单选题A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) MEP is lower and the scavenging air is cooling the exhaust gases (2) valve overlap in a four-strokeA
(1) only is correctB
(2) only is correctC
both (1) and (2) are correctD
Neither (1) or (2) are correct
考题
单选题The size of the exhaust valve opening is （）A
most critical in a four-stroke cycle diesel engineB
most critical in a two-stroke/cycle diesel engineC
most critical in a four-stroke/cycle diesel engine if it is turbochargedD
of equal importance in a two-stroke/cycle diesel engine as in a four-stroke/cycle diesel engine
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单选题During the fuel injection period, fuel pressure must exceed cylinder gas pressure to （）.A
ensure penetration and distribution of the fuel in the combustion chamberB
ensure the needle valve is flushed clean during each injectionC
prevent combustion gas blowback into the open needle valveD
prevent reflected pressure waves when the needle valve closes
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单选题The exhaust system for a turbocharged two-stroke/cycle diesel engine functions to（）A
discharge exhaust gases and smokeB
furnish energy to the turbochargerC
reduce engine room noiseD
all of the above
考题
单选题High exhaust temperatures from all of cylinder of a turbocharged, four-stroke/cycle diesel engine can be caused by an（）A
inoperative turbochargerB
inadequate fuel supplyC
overload on one cylinderD
unequal load distribution
考题
单选题In a closed cooling system for a turbocharged, four-stroke/cycle diesel engine, fluctuating water pressure can be caused by （）A
improper venting of the cooling systemB
carrying the expansion tank water level too highC
a totally clogged impeller in the cooling water pumpD
an incorrectly set cooling system temperature control
考题
单选题During the valve overlap period, the exhaust pressure of a turbochargers, four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure （）A
effective cylinder scavenging and coolingB
constant pressure from the turbochargersC
cooler operation of the exhaust systemD
effective constant pressure for turbocharger operation
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Scavenging in a four-stroke/cycle diesel engine occurs during the （）.A
last part of the exhaust stroke, and the first part of the intake strokeB
last part of the intake stroke onlyC
early part of the injection stroke onlyD
early part of the power stroke
考题
单选题A turbocharged diesel engine will have an intake manifold pressure（）A
constantly decreasing as engine load increaseB
constantly increasing as the amount of supercharging increasesC
approximately equal to exhaust manifold pressure at all timesD
approximately equal to atmospheric pressure at all times
考题
单选题Exhaust valve openings in a diesel engine cylinder head are made as large as practical to （）A
increase back pressure during the exhaust processB
facilitate periodic replacement of the valvesC
reduce the pumping loss associated with scavengingD
reduce tension on valve springs
考题
单选题Clearance volume scavenging in a turbocharged, four-stroke/cycle diesel engine is accomplished （）.A
during the valve overlap periodB
with only the exhaust valve openC
at a pressure below atmosphericD
without cooling the cylinders or pistons
考题
单选题In an engine with air inlet valve and exhaust valve on its cylinder heads the fresh air will enter into the cylinder （） and the gases exhaust （）, there being an adequate overlap between the inlet opening and the exhaust closing.A
downwards；upwardsB
upwards；downwardsC
downwards；downwardsD
upwards；upwards
考题
单选题Any increase in the exhaust back pressure of a four-stroke/cycle diesel engine will （）.A
reduce engine horsepower outputB
aid in silencing the exhaust noiseC
increase the mean effective pressureD
contribute to effective cylinder scavenging
考题
单选题Which of the following statements is correct regarding a turbocharged four-stroke/cycle diesel generator?（）A
At zero load the intake manifold pressure is greater than the exhaust manifold pressureB
At full load the intake manifold pressure and exhaust manifold pressure are equalC
At full load the intake manifold pressure is less than the exhaust manifold pressureD
At full load the intake manifold pressure is greater than the exhaust manifold pressure
考题
单选题A turbocharged, four-stroke/cycle diesel engine has a larger valve overlap than a naturally aspirated four-stroke/cycle diesel engine, in order to in crease the （）.A
temperature of the exhaust gasesB
energy supplied to the turbochargerC
air pressure to the intake manifoldD
purge of exhausted gases from the cylinders
考题
单选题Turbocharged four-stroke/cycle diesel engines utilize valve overlap for（）.A
improving cylinder scavengingB
preheating the combustion chamberC
reducing air charge densityD
preventing valve wear
考题
单选题Scavenging in a turbocharged, four-stroke/cycle diesel engine is accomplished（）A
during the valve overlap periodB
with only the exhaust valve openC
at a pressure below atmosphericD
without cooling the cylinders or pistons
考题
单选题A four-stroke cycle, turbocharged, 1000 horsepower diesel engine has been operating under loadThe load suddenly increases, causing excessive black exhaust smoke, and a rapid rise in the lube oil temperatureIn response to this condition, you should:（）A
reduce loadB
check your exhaustC
adjust cooling water temperatureD
increase lube oil flow
考题
单选题Which of the listed components is considered to separate the high pressure side of a refrigeration cycle from the low pressure side of the cycle?（）A
The condenser and the expansion valveB
The king valve and the solenoid valveC
The compressor and the expansion valveD
The condenser and the solenoid valve
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单选题A four-stroke/cycle, 1000horsepower diesel engine fails to start at normal cranking speed with normal fuel pressure and ambient temperatureThe reason for the failure could be（）A
glazed liners or pistonsB
high lube oil pressureC
excessive compression ratioD
worn valve seats and valves
考题
单选题If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.A
open；short；afterB
closed；short；afterC
open；long；beforeD
closed；long；before
考题
单选题In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to（）.A
produce a scavenging effect in the combustion spaceB
equalize cylinder and exhaust manifold pressuresC
alleviate the difference in valve size between the intake and exhaustD
flush out condensate that collects after each compression stroke
考题
单选题A piston in a four-stroke/cycle diesel engine makes four strokes during each （）.A
crankshaft revolutionB
mechanical cycle of operationC
period of two combustion cyclesD
cycle of two events
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