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单选题
The purpose of compressing the air within the cylinder of a diesel engine is to （）
A
produce the heat for ignition
B
decrease injection lag
C
increase ignition delay
D
aid in exhausting burnt gases
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更多 “单选题The purpose of compressing the air within the cylinder of a diesel engine is to （）A produce the heat for ignitionB decrease injection lagC increase ignition delayD aid in exhausting burnt gases” 相关考题
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Diesel engines are started by supplying into the cylinders in the appropriate sequence for the required direction.A.cooling waterB.compressing airC.compressed airD.cylinder oil
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Diesel engines are started by supplying_____into the cylinders in the appropriate sequence for the required direction.A.cooling waterB.compressing airC.compressed airD.cylinder oil
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_______is usually driven by the engine camshaft and supplies pilot air to the cylinder air start valve.A.An air receiverB.An operating valveC.An automatic valveD.An air distributor
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In an operating diesel engine, which of the following conditions is an indication of a leaking air starting valve?A.Noise coming from that air starting valveB.Continuous operation of the starting air compressorC.Zero air pressure in the air starting systemD.Overheated starting air pipe to the cylinder head
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第一组： The Wartsila 50DF operates on the lean-bum principle: the mixture of air and gas in the cylinder has more air than is needed for complete combustion. Lean combustion reduces peak temperatures and therefore NOx emissions. Efficiency is increased and higher output is reached while avoiding knocking. Combustion of the lean air-fuel mixture is initiated by injecting a small amount of LFO (pilot fuel) into the cylinder. The pilot fuel is ignited in a conventional diesel process, providing a high-energy ignition source for the main engine. To obtain the best efficiency and lowest emissions, every cylinder is individually controlled to ensure operation at the correct air-fuel ratio and with the correct amount and timing of pilot fuel rejection. Wartsila has developed a special electronic control system to cope with the demanding task of controlling the combustion in each cylinder, and to ensure optimal performance in terms of efficiency and emissions under all conditions by keeping each cylinder within the operating window. Stable and well-controlled combustion also contributes to less mechanical and thermal load on the engine components. Current stringent emission regulations demand the reduction of NOx emissions. In an internal combustion engine this means controlling peak temperature and residence time, which are the main parameters governing NOx formations. In the Wartsila 50DF engine, the air-fuel ratio is very high (typically 2.2). Since the same specific heat quantity released by combustion is used to heat up a larger mass of air, the maximum temperature and consequently NOx formation are lower. The mixture is uniform. throughout the cylinder since the fuel and air are premixed before introduction into the cylinders, which helps to avoid local NOx formation points within the cylinder. Benefiting from this unique feature, NOx emissions from the Wartsila 50DF are extremely and comply with the most stringent existing legislation.What is the combustion feature of the Wartsila 50DF?A.Lean air in the cylinderB.Excessive fuel in the cylinderC.Excessive air in the cylinderD.Spark ignition
考题
How does combustion air enter the cylinder of a two-cycle diesel engine ? Through _______．A.Cylinder head valvesB.PortsC.Turbo chargersD.Bleeder valves
考题
What is the most probable cause of reduced capacity in a reciprocating air compressor ________．A.Carbon on cylinder headsB.Faulty unloaderC.Leaking air valvesD.Plugged air cooler
考题
单选题The opening or closing of the cylinder starting valve is controlled by （）.A
the starting air distributorB
the cut-off valve on the air mainC
the main starting valveD
the air bottle control valve
考题
单选题The main purpose of starting the diesel engine on air briefly is（）A
to inspect if the cylinder has the water leakageB
to expel out the residual water/gas/oil from the cylinderC
to check if fuel supply is normalD
A and B
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
考题
单选题Air motion is induced in a four-stroke/cycle diesel engine cylinder to improve air fuel mixing, and is known as（）A
superchargingB
scavengingC
turbulenceD
swept volume charging
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单选题Which of the conditions listed may occur in an operating diesel engine if air pockets form within the cylinder head circulating water passages? （）A
Hydraulic stress and distortion will developB
Hot spots will developC
Fuel oil viscosity will increasedD
An increase in trapped deposits of scale and dirt
考题
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
考题
单选题The term diesel engine scavenging means（）A
delivering more air into the cylinder than it would normally receive during an ordinary charging processB
forcing the products of combustion out of the cylinder with the fresh air chargeC
collecting the air charge at the cleanerD
combustion and expansion of hot gas
考题
单选题Opening of the cylinder （） will admit compressed air into the cylinder.A
safety valveB
indicator cockC
blow-down valveD
start valve
考题
单选题In the starting system, the automatic valve is controlled by（）, and the cylinder start valves are controlled by（）A
pilot air；pilot airB
handle；solenoidC
handle；pilot air coming through the distributorD
solenoid；pilot air coming through the distributor
考题
单选题Compressed air is supplied by air compression to （）.A
the air receiversB
the starting valvesC
the cylinder coversD
the distributors
考题
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（） is usually driven by the engine camshaft and supplies pilot air to the cylinder air start valve.A
An air receiverB
An operating valveC
An automatic valveD
An air distributor
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（） supplies pilot air to control the cylinder air start valves.A
An air compressorB
An indicator cockC
An air distributorD
A safety valve
考题
单选题The principal difference between loop scavenging and crossflow scavenging, as used in single acting diesel engines, is the （）A
direction of air flow within the cylinderB
sequence of port openingC
method of opening exhaust portsD
volume of air admitted to the cylinder
考题
单选题If the piston ring gap remains insufficient when installing new rings, youshould（）A
install oversized ringsB
hone the cylinder liner to allow ring installationC
compress the rings tighter with a compressing toolD
file the ends of the rings
考题
单选题In the suction stroke air is induced into the cylinder （）In the compression stroke the air is compressed.A
by an fuel valveB
through an inlet valveC
with an exhaust valveD
from an outlet valve
考题
单选题When the starting air valve closes on one cylinder, another starting air valve has （） opened on another cylinder whose piston has just commenced its downward stroke.A
justB
nearlyC
merelyD
already
考题
单选题In an operating diesel engine, which of the following condition is an indication of a leaking air starting valve?（）A
noise coming from that air starting valveB
continuous operation of the starting air compressorC
zero air pressure in the air starting systemD
overheated starting air pipe to the cylinder head
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