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单选题
Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.
A
heat conduction into the injected fuel oil
B
heat conduction into the water jacket wall
C
water circulation through passages in the holder
D
fuel oil circulation through passages in the holder
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更多 “单选题Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.A heat conduction into the injected fuel oilB heat conduction into the water jacket wallC water circulation through passages in the holderD fuel oil circulation through passages in the holder” 相关考题
考题
If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at theA.fuel line connections to the cylinder injection valvesB.gasket surfaces of the fuel oil filtersC.discharge fittings of the fuel injector pumpsD.suction side of the fuel oil transfer pump
考题
Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily byA.heat conduction into the injected fuel oilB.heat conduction into the water jacket wallC.water circulation through passages in the holderD.fuel oil circulation through passages m the holder
考题
第一组Older loop scavenged engines may have a single injector mounted centrally in the cylinder head. Because the exhaust valve is in the center of the cylinder head on modern uniflow scavenged engines the fuel valves (2 or 3) are arranged around the periphery of the head. The pressure at which the injector operates can be adjusted by adjusting the loading on the spring. The pressures at which the injectors operate vary depending on the engine, but can be as high as 540 bar. Some injectors have internal cooling passages in them extending into the nozzle through which cooling water is circulated. This is to prevent overheating and burning of the nozzle tip. Injectors on modern engines do not have internal cooling passages. They are cooled by a combination of the intensive bore cooling in the cylinder head being close to the valve pockets and by the fuel which is re-circulated through the injector when the follower is on the base of the cam or when the engine is stopped. As well as cooling the injector, re-circulating the fuel when the engine is stopped keeps the fuel at the correct viscosity for injection by preventing it from cooling down. Fuel injectors must be kept in good condition to maintain optimum efficiency, and to prevent conditions arising which could lead to damage within the cylinder. Injectors should be changed in line with manufacturers recommendations, overhauled and tested. Springs can weaken with repeated operation leading to the injector opening at a lower pressure than designed. The needle valve and seat can wear which together with worn nozzle holes will lead to incorrect atomization and dribbling.Modern uniflow scavenged engines have______.A.a single injector mounted in the center of the cylinder headB.several injectors mounted around the external boundary of the cylinder headC.a single injector mounted at the external boundary of the cylinder headD.several injectors mounted in the center of the cylinder head
考题
Cooling water is circulated through______in some injectors.A.the nozzleB.the nozzle tipC.the internal passagesD.the fuel re-circulated
考题
_______can be a direct cause of faulty operation of diesel engine fuel injection nozzles.A.Excessive fuel nozzle holder coolingB.Sediment in the fuel supplyC.Distortion of the fuel spray patternD.Improper atomization of the fuel
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When the opening pressure of a diesel fuel injector is greater than that specified by the engine manufacturer，the （）A
quantity of fuel injected is decreasedB
quantity of fuel injected will always be increasedC
start of injection is advancedD
duration of injection will always be greater
考题
单选题Fuel oil discharged to the diesel engine cylinder is atomized at the （）A
turbochargerB
injection nozzle tipC
carburetorD
fuel oil pump
考题
单选题White smoke exhausting from a diesel engine can be caused by （）A
low combustion temperatureB
a leaking fuel nozzle check valveC
late fuel injectionD
plugged oil-scraper ring hole
考题
单选题Heat damage to fuel injection nozzles on small high-speed diesel engines, can be prevented by（）A
employing fuel oil as a cooling mediumB
preventing hard carbon deposit on nozzle tipsC
avoiding fuel oil temperature exceeding builder’s specificationD
ensuring good metallic contact between nozzles and cylinder heads
考题
单选题A leaking diesel engine fuel injector will cause（）A
prolonged maintenance intervalsB
improved atomizationC
greater fuel economyD
incomplete combustion
考题
单选题As the plunger moves up, the ports are closed and the fuel （） and delivered to the injector nozzle at very high pressure.A
being compressedB
to be pumped upC
is pressurizedD
are built up
考题
单选题A sudden drop in diesel engine cylinder compression pressure can be caused by（）A
a leaking fuel injector nozzleB
a clogged air filterC
excessively early fuel injectionD
malfunctioning valves
考题
单选题When the opening pressure of a diesel engine fuel injector is greater than that specified by the engine manufacturer, which of the following problems can be expected?（）A
Quantity of fuel injected tends to be decreasedB
Quantity of fuel injected will always be increasedC
Start of injection tends to be advancedD
Duration of injection will always greater
考题
单选题In a unit injector the amount of fuel that will be forced through the spray nozzle on each stroke of the plunger depends on （）A
the pump supply pressureB
the slope of the fuel camC
how the plunger is rotatedD
the number of sleeve segments engaged with the rack
考题
单选题To successfully reduce an excessively high diesel engine exhaust gas temperature, you should （）.A
reduce the engine driven fuel pump outlet pressureB
retard the fuel injector timing to reduce powerC
increase the fuel rack settingD
reduce the load on the engine
考题
单选题A change in the quality of fuel atomization by a diesel engine fuel injector would be caused by a/an （）A
increase in engine speedB
increase in cylinder turbulenceC
leaking needle valveD
reduction in cylinder turbulence
考题
单选题The amount of fuel injection into a diesel engine cylinder by a unit injector, is controlled by（）A
the firing pressure in the cylinderB
a metering helix inside the pumpC
varying the physical length of the plunger strokeD
varying the clearance between the injector cam and the injector rocker arm
考题
单选题The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to （）.A
assist in a quick cutoff of fuel injectionB
allow oil backflow from the injector to the helixC
reduce fuel oil pressure between injection strokesD
meter the quantity of fuel delivered
考题
单选题Indirect cooling of fuel injector nozzle holders for diesel engines is accomplished primarily by （）.A
heat conduction into the injected fuel oilB
heat conduction into the water jacket wallC
water circulation through passages in the holderD
fuel oil circulation through passages in the holder
考题
单选题A defective injector nozzle in a propulsion diesel engine can cause（）A
engine power lossesB
smoking due to unburned fuelC
high exhaust temperature readingsD
all of the above
考题
单选题A distorted spray pattern from a fuel injector can cause a diesel engine to have （）A
higher firing pressureB
more power outputC
lower fuel pressureD
less power output
考题
单选题Faulty operation of diesel engine fuel injection nozzles can be a direct cause of（）.A
excessive fuel nozzle holder coolingB
sediment in the fuel supplyC
distortion of the fuel spray patternD
improper atomization of the fuel
考题
单选题One remedy for a high firing pressure, in addition to a high exhaust temperature in one cylinder of a diesel engine, is to （）A
increase scavenge air pressureB
reduce fuel booster pump pressureC
adjust the fuel rackD
retard fuel injector timing
考题
单选题Faulty operation of diesel engine fuel injection nozzles can be directly caused by （）.A
water in the fuel oil supplyB
excessive fuel nozzle holder coolingC
a distorted fuel spray patternD
leakage past the plunger into the oil drain
考题
单选题In the cylinder of a diesel engine fuel is ignited by the（）A
spark from a plug in the pre-combustion chamberB
electrical discharge from the distributorC
heat of compression within the cylinderD
heat from the fuel injection nozzle
考题
单选题A sudden drop in compression pressure in one cylinder of a diesel engine can be caused by（）A
a leaking fuel injector nozzleB
a clogged air filterC
excessively early fuel injectionD
malfunctioning valves
考题
单选题If you suspect a diesel engine is misfiring due to air leakage into the fuel system, you should begin looking for the leak at the （）A
fuel line connections to cylinder injection valvesB
gasket surfaces of the fuel oil filtersC
discharge fitting of the fuel injector pumpsD
suction side of the fuel oil tran
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