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单选题
Many diesel engine exhaust valves are being constructed with hollow stems filled with sodium in order to （）
A
provide added wear protection against today’s corrosive quality of fuel
B
increase overall valve strength due to the high gas pressures
C
assist in dissipating heat due to the extreme operating temperatures
D
reduce the overall weight of the valve thus helping eliminate valve spring surge and hammering
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更多 “单选题Many diesel engine exhaust valves are being constructed with hollow stems filled with sodium in order to （）A provide added wear protection against today’s corrosive quality of fuelB increase overall valve strength due to the high gas pressuresC assist in dissipating heat due to the extreme operating temperaturesD reduce the overall weight of the valve thus helping eliminate valve spring surge and hammering” 相关考题
考题
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.①B.②C.① and ②D.Neither ① nor ② is correct
考题
The closing of the exhaust valves used on a modern, large, low-speed, main propulsion diesel engine may be directly provided by_______.A.large conical springsB.compressed air pressureC.hydraulic pressureD.exhaust gas pressure
考题
Fuel is admitted to a diesel engine cylinder through the ______.A.injector nozzlesB.carburetorC.exhaust portsD.intake valves
考题
单选题For an ordinary four-stroke diesel engine the exhaust valves close （）.A
after TDCB
before TDCC
after BDCD
before BDC
考题
单选题Diesel oil may be used to cool （） of a diesel engine.A
cylindersB
exhaust valvesC
pistonsD
fuel valves
考题
单选题Air scavenging of a diesel engine cylinder（）A
blows out the exhaust gasesB
supplies oxygen for combustionC
cools the valves and cylinder wallsD
all of the above
考题
单选题In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressureA
ⅠonlyB
ⅡonlyC
bothⅠand ⅡD
neitherⅠnor Ⅱ
考题
单选题Diesel engine mufflers or silencers reduce the engine exhaust noise by （）A
passing the exhaust through long head pipesB
diffusing exhaust vibrations through activated carbon bafflesC
increasing the exhaust gas velocityD
reducing the exhaust gas velocity
考题
单选题Clogged or partially obstructed exhaust ports on a diesel engine can cause（）A
over-speeding of the engineB
failure of the engine to shut downC
no effect of engine mounting boltsD
high exhaust temperatures
考题
单选题Diesel engine exhaust noise can be reduced in an exhaust muffler by （）A
changing the direction of exhaust gas flowB
increasing the exhaust gas velocityC
changing the exhaust gas weightD
increasing the exhaust gas static pressure
考题
单选题The satisfactory operation of diesel engine exhaust valves usually depends on（）A
the proper back pressureB
the cooling water temperatureC
correct timing and proper seatingD
accurate metering and the exhaust temperature
考题
单选题The exhaust system of a diesel engine is usually designed to remove exhaust gases and to （）A
provide exhaust back pressureB
prevent exhaust smoke emissionsC
power a reciprocating superchargerD
muffle exhaust gas noise
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
考题
单选题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 temperatureB
Low firing pressure and high exhaust temperatureC
Low compression pressure and low exhaust temperatureD
Low firing pressure and low exhaust temperature
考题
单选题What is the purpose of the intake/exhaust valves in a diesel engine? （）A
They regulate the combustion cycleB
They supply cooling waterC
They synchronize the ignition sparkD
They supply and regulate the lubricant flow
考题
单选题The intake valves in a diesel engine are reseated by （）.A
cam followersB
push rodsC
combustion gasesD
valve springs
考题
单选题In a diesel engine exhaust system, the cooling of the exhaust gases below their dew point, will result in （）A
increased engine back pressureB
sulfuric acid corrosionC
surface pitting of the turbochargerD
moisture impingement on the turbocharger compressor blade
考题
单选题Diesel engine valve springs function to （）A
hold the valves openB
keep the valves off their seats until the exhaust stroke is completedC
close the valvesD
open inlet valves when the air injection cycle begins
考题
单选题The pressure in an operating diesel engine cylinder continues to rise for a short period after the piston passes top dead center as a result of the （）A
expansion of the combustion gasesB
exhaust and intake valves just closingC
maximum compression is just being attainedD
fuel injection occurring at that point and combustion begins
考题
单选题Which of the following conditions can cause above normal air temperature to develop in the intake manifold of a four-stroke/cycle turbo-charged diesel engine?（）A
Clogged air intake faltersB
Piston blow-byC
A defective after-coolerD
Faulty exhaust valves
考题
单选题Low compression pressure in a diesel engine may be the result of （）A
insufficient fuel supply due to fuel pump valves sticking or leakingB
excessive mechanical clearance between the piston crown and cylinder headC
excessively worn fuel pump plungerD
excessive exhaust back pressure
考题
单选题In comparison to exhaust valves, intake valves of diesel engines may be fabricated from low alloy steels because （）.A
the beveled edges of the intake valves provide for serf-centering during seatingB
intake valves utilize stellite-coated valve seat inserts which reduce wearC
the volume of air passing through intake valves is less than the volume of air passing through exhaust valvesD
intake valves are less affected to the corrosive action of exhaust gases
考题
单选题An indication of a diesel engine air intake being partially clogged, is （）.A
low firing pressure and low exhaust temperaturesB
low firing pressure and normal exhaust temperaturesC
high firing pressure and low exhaust temperaturesD
high firing pressure and high exhaust temperatures
考题
单选题If you observe smoke coming from the turbocharger of an auxiliary diesel engine, you should（）A
check the air filter for obstructionB
check for an exhaust leakC
check the exhaust temperatureD
secure the engine
考题
单选题The closing of the exhaust valves used on a modern, large, low-speed, main propulsion diesel engine may be directly provided by （）.A
large conical springsB
compressed air pressureC
hydraulic pressureD
exhaust gas pressure
考题
单选题“This increase in charge air density is accomplished on most modern diesel engine types by use of exhaust gas turbo-charging, in which a turbine wheel driven by exhaust from the engine is rigidly coupled to a centrifugal type air compressor” According to this sentence, we can know that increases density（）, drives the compressor directly（）A
a modern diesel engine；a turbine wheelB
a modem diesel engine；exhaust gasesC
a compressor；an exhaust gas turbochargerD
a compressor；a turbine wheel
考题
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) scavenging air is cooling the exhaust gases (2) exhaust cycle time is longerA
(1) onlyB
(2) onlyC
both (1) and (2)D
neither (1) nor (2)
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