网友您好, 请在下方输入框内输入要搜索的题目:
题目内容
(请给出正确答案)
单选题
The needle valve in the injector () at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.
A
will lift
B
will be lifted
C
will close
D
will be closed
参考答案
参考解析
解析:
暂无解析
更多 “单选题The needle valve in the injector () at a pre-set pressure which ensures that the fuel will atomize once it enters the cylinder.A will liftB will be liftedC will closeD will be closed” 相关考题
考题
Which of the listed pressure control valves would be used to establish the maximum operating pressure of a hydraulic system?A.Pressure-reducing valveB.Unloading valveC.Counterbalance valveD.Pressure-relief valve
考题
The( )in the injector will lift at a pre-set pressure which ensures that the fuelwill atomize once it enters the cylinder.A.needle valveB.nozzlesC.pistonD.spring
考题
If the head pressure of a reciprocating refrigeration compressor is excessiveA.the relief valve should open before the high pressure cutoutB.the relief valve should open and allow the excess refrigerant to flow to the receiverC.the high pressure cutout switch should operate before the relief valve opensD.you should close the discharging valve
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
Springs in fuel injectors will become not strong enough to work because______.A.the injector opens at a lower pressure than designedB.the needle valve and seat wear outC.the nozzle holes wear outD.long time in use
考题
单选题() are used to limit the pressure in any particular portion and mainly control the pressure after the valve.A
Relief valvesB
Check valvesC
Safety valvesD
Reducing valve
考题
单选题The needle valve in a fuel valve will () when the fuel pressure action on the needle valve tapered face exerts a force lower than that of the spring compression.A
be jammedB
be openedC
be seatedD
be broken
考题
单选题The injector pump is operated by a cam which drives () up and down.A
the needle valveB
the plungerC
the pistonD
the cylinder
考题
单选题A more sophisticated pressure reducing valve incorporates a pilot valve which controls the fluid above the valve operating piston in response to downstream pressureThe bold and italic word “which” means ().A
a pressure reducing valveB
a pilot valveC
an operating pistonD
downstream pressure
考题
单选题During the fuel injection period, fuel pressure must exceed cylinder gas pressure to ().A
ensure penetration and distribution of the fuel in the combustion chamberB
ensure the needle valve is flushed clean during each injectionC
prevent combustion gas blowback into the open needle valveD
prevent reflected pressure waves when the needle valve closes
考题
单选题If the head pressure of a reciprocating refrigeration compressor is excessive, ().A
the relief valve should open before the high pressure cutoutB
the relief valve should open and allow the excess refrigerant to flow to the receiverC
the high pressure cutout switch should operate before the relief valve opensD
you should close in on the suction valve
考题
单选题The needle valve will open when the fuel pressure acting on the needle valve () exerts a sufficient force to overcome the spring compression.A
tape faceB
tapered faceC
surfaceD
thinner face
考题
单选题If the head pressure is too high,()A
the relief valve should open before the high-pressure cutoutB
the relief valve should open and let excess refrigerant go to receiverC
the high-pressure cutout switch should operate before the relief valve opensD
close in on the suction valve
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 of the following would not cause high suction pressure?()A
insufficient refrigerationB
leaky suction valvesC
expansion valve stuck openD
suction valve not adjusted properly
考题
单选题The arrangement and shape of the cams on a diesel engine camshaft directly control which of the listed groups of operating conditions?()A
speed, torque, and horsepower productionB
firing order, valve timing, and valve liftC
fuel consumption, efficiency, and cylinder pressureD
scavenge pressure, compression ratio, and exhaust pressure
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Differential needle valves used in fuel injectors are directly closed by()A
cam actionB
spring forceC
fuel oil pressureD
firing pressure
考题
单选题A thermostatic expansion valve is properly controlling evaporator superheatAdjusting this valve to lower the superheat will result in a/an ().A
evaporator pressure decreaseB
evaporator coil over-feedC
evaporator capacity increaseD
expansion valve diaphragm rupture
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When the heat load begins to increase, the needle valve of an expansion valve will()A
move in an opening directionB
move in a closing directionC
either open or closeD
not move at all
考题
单选题The thermostatic valve has a throttling action, that is to say the valve can()A
stop the refrigerant from flowingB
force the refrigerant to flowC
cause the refrigerant pressure to riseD
cause the refrigerant pressure to fall
考题
单选题The low pressure side of a refrigeration system is considered to exist from the ().A
expansion valve to the compressorB
receiver to the expansion coilC
expansion valve to the evaporatorD
condenser to the expansion valve
考题
单选题Which of the listed components is considered to separate the high pressure side of a refrigeration cycle from the low pressure side of the cycle?()A
The condenser and the expansion valveB
The king valve and the solenoid valveC
The compressor and the expansion valveD
The condenser and the solenoid valve
考题
单选题A spring-loaded centrifugal flyweight governor responds to reduced engine load with an immediate increase in ()A
pilot valve oil pressureB
speeder spring forceC
compensation needle valve clearanceD
centrifugal force on the flyweights
热门标签
最新试卷