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单选题
The starting air entering the cylinder begins when the piston（）
A
has nearly come to the TDC
B
has just past the TDC
C
has nearly come to the BDC
D
has just past the BDC
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考题
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
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
考题
In the event of the cylinder starting valve leakage ______would pass into the air pipes and ignite the oil deposited.A.cooling waterB.vapor from the boilerC.starting airD.hot gases
考题
______device is provided to prevent starting air from being admitted to the cylinder before the reversing is completed.A.An automaticB.A transmissionC.A self-regulatingD.An interlocking
考题
单选题Vessels having main engines arranged for air starting are to be provided with at least （）A
one automatic drain serving both containersB
two air starting containers of approximately equal sizeC
one control air container and one starting air containerD
one additional means of starting the main engine
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When the order （） is received from the bridge, the main air stop valve in the starting air line should be shut.A
stand-by engineB
full aheadC
finished with engineD
full away
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（） device is provided to prevent starting air from being admitted to the cylinder before the reversing is completed.A
An automaticB
A transmissionC
A self-regulatingD
An interlocking
考题
单选题When used in conjunction with a turbocharger, the main function of an after-cooler is to （）A
increase the density of the cylinder air chargeB
prevent turbocharger overheatingC
liminate the need for a pre-coolerD
remove moisture from air compressed by the turbocharger
考题
单选题When an air started, four-stroke/cycle diesel engine is being cranked, the starting air is admitted to each cylinder during what would normally be the（）A
intake strokeB
compression strokeC
power strokeD
exhaust stroke
考题
单选题Which of the following methods is used to prevent throttling of compressed air through the diesel engine air starting valves?（）A
Holding the valve open for a long periodB
Increasing the starting air pressure usedC
Opening the stating air valve quicklyD
Reducing the starting air valve size
考题
单选题Intercoolers installed on starting air compressors, reduce the possibility of（）A
dust entering the high pressure stageB
lube oil carbonizationC
discharge pulsationsD
inter-stage vapor lock
考题
单选题When starting an engine, the compressed air enters the cylinder when the corresponding piston is in position of its（）A
suction strokeB
compression strokeC
power strokeD
exhaust stroke
考题
单选题The compressed air is admitted to each cylinder through a cam operated by starting air valve when the piston has just passed its （）.A
BDCB
TDCC
BBDCD
ATDC
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Each cylinder has one starting valve which is usually opened by air pressure and closed by （）A
nuts and boltsB
new jointsC
spring forceD
sealing rings
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In the event of the cylinder starting valve leakage （） would pass into the air pipes and ignite the oil deposited.A
cooling waterB
vapor from the boilerC
starting airD
hot gases
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When starting air is admitted, a diesel engine turns over very slowly without firingThe cause may be （）A
an obstruction in an cylinderB
water accumulation in some engine cylindersC
low starting air pressureD
low scavenge air pressure
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The air distributor is conventionally driven by（） and distributes into each cylinder by（） certain sequence.A
camshaft；fresh airB
camshaft；starting airC
electronic motor which is controlled by a computer；fresh airD
electronic motor which is controlled by a computer；starting air
考题
单选题When an engine is starting and has got a sufficiently high speed, say about 20 rpm,（）A
the starting air supply is cut off and fuel is injected into the cylindersB
the fuel feeding is cut off and the turning gear is put inC
the starting air supply is cut off and turning gear is taken outD
the electric blower is shut down and fuel is injected into the cylinders
考题
单选题The highest pressure in a diesel engine cylinder normally occurs （）.A
at TDCB
before TDCC
after TDCD
during air starting
考题
单选题In slow speed two-stroke engines,（）the fresh air entering begins when and stops as（）A
the inlet port is opened by the up coming piston； the port is closed by the down goingB
the inlet valve is opened by the down going piston；the inlet valve is closedC
the inlet port is opened by the down going piston；the port is closed by the up comingD
the inlet valve is opened
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