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单选题
（） supplies pilot air to control the cylinder air start valves.
A
An air compressor
B
An indicator cock
C
An air distributor
D
A safety valve
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更多 “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” 相关考题
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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
You must take good care of the drainage cock of the air control system. Because lead scale formed which might malfunctions the pilot control valve and other instruments.A.the temperatureB.the rustC.the pressureD.the humidity
考题
_______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
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
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
考题
单选题You must take good care of the drainage cock of the air control systemBecause （） leads scale formed which might malfunction the pilot control valve and other instruments.A
the temperatureB
the rustC
the pressureD
the humidity
考题
单选题Which of the following may lead to the engine NOT to start on air?（）A
starting air pressure too highB
correct timing of starting air valvesC
three of the six starting valves stuckD
the turning gear disengaged
考题
单选题The engine will fail to start unless （）.A
the pressure of the starting air is high enoughB
there is enough air in the air reservoirsC
the air is supplied into the cylinders in the appropriate sequenceD
all of the above
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Diesel engine air start system check valves are opened by （）A
an air start camB
cylinder compression pressureC
starting air pressureD
valve springs
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The pressure of pilot air is usually （） than that of starting air.A
higherB
lowerC
lowD
high
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If an air compressor is used to supply compressed air to outlets throughout the engine room and on deck of a vessel, the system is known as the （）.A
combustion control air systemB
supply air systemC
ships service air systemD
low pressure deck air system
考题
单选题Air compressor cylinder un-loaders enable the compressor to （）.A
vary their speed according to temperature and loadB
start and come up to speed before air compression beginsC
change speed according to overload demandsD
reduce compressed air charge density
考题
单选题If a four-stroke/cycle diesel engine is started by injecting air into the cylinder, the pistons receiving the charge of starting air must be（）A
on the power strokeB
on the exhaust strokeC
at the end of the power strokeD
at the start of the intake stroke
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
考题
单选题If an air compressor is used to supply air primarily to the combustion control system and other pneumatic controllers, the entire system is known as the （）.A
control air systemB
forced draft air systemC
supply air systemD
ships service air system
考题
单选题The timing of diesel engine air starting valves is controlled by（）A
the air start valve timing gears and rodsB
a cylinder check valveC
individual cams and valve gearD
an air manifold poppet valve
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