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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 decreased
B
quantity of fuel injected will always be increased
C
start of injection is advanced
D
duration of injection will always be greater
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更多 “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” 相关考题
考题
A smoking exhaust from an operating diesel engine could be caused by( ).A.low sulfur content in the fuelB.a loose injector inlet connectionC.late fuel injectionD.high injection pressure
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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
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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
Fuel is admitted to a diesel engine cylinder through the ______.A.injector nozzlesB.carburetorC.exhaust portsD.intake valves
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The fuel injector injects a fine spray of fuel into the hot air and combustion （）, producing much high pressure in the gases.A
has begunB
takes placeC
occursD
happens
考题
单选题A practical way of checking for excessive fuel injection in one cylinder of an operating diesel engine is to （）A
feel the high pressure fuel lineB
check the cylinder exhausts for white smoke frequentlyC
check the cylinder exhaust temperatureD
isolate each cylinder and inspect the injector
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A smoking exhaust from an operating diesel engine could be caused by （）A
low sulfur content in the fuelB
a loose injector inlet connectionC
late fuel injectionD
high injection pressure
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The （） in the injector will lift at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.A
needle valveB
nozzlesC
pistonD
spring
考题
单选题Which one is not the normal operation for boiler shutdown?（）A
Carry out soot blowing if permissibleB
Change fuel supply to diesel oilC
Close steam stop valves on boiler when pressure is reducedD
Drain boiler empty when it has cooled down
考题
单选题If a diesel engine is smoking excessively under load, the cause could be （）A
low exhaust back pressureB
early fuel injection in one of the cylindersC
compression pressure in one of the cylindersD
plugged injector holes
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Injection lag in a diesel engine may be caused by（）A
a higher cetane number of fuel oilB
the diesel fuel used having a high viscosityC
mechanical rigidity in the lube pump mechanismD
a decrease rigidity in the fuel pump delivery pressure
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A fuel injection valve opening at pressure lower than normal will result in（）.A
late fuel injectionB
early fuel injectionC
high exhaust temperature from that cylinderD
decreased effective stroke from that injector
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 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
考题
单选题When comparing different fuels for different engines, the ignition quality of diesel fuel oils becomes a less critical consideration as （）A
the amount of lube oil additives increaseB
piston speeds increaseC
injection pressure decreaseD
engine speeds decrease
考题
单选题The minimum fuel oil delivery pressure required for diesel engine injection depends primarily on the（）A
degree of cylinder air turbulenceB
firing pressure in the engineC
quality of fuel to be injectedD
duration of the ignition delay period
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