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.Awill liftBwill be liftedCwill closeDwill be closed

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


参考解析

解析: 暂无解析

相关考题:

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

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

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

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

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

单选题() are used to limit the pressure in any particular portion and mainly control the pressure after the valve.ARelief valvesBCheck valvesCSafety valvesDReducing valve

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.Abe jammedBbe openedCbe seatedDbe broken

单选题The injector pump is operated by a cam which drives () up and down.Athe needle valveBthe plungerCthe pistonDthe cylinder

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 ().Aa pressure reducing valveBa pilot valveCan operating pistonDdownstream pressure

单选题During the fuel injection period, fuel pressure must exceed cylinder gas pressure to ().Aensure penetration and distribution of the fuel in the combustion chamberBensure the needle valve is flushed clean during each injectionCprevent combustion gas blowback into the open needle valveDprevent reflected pressure waves when the needle valve closes

单选题If the head pressure of a reciprocating refrigeration compressor is excessive, ().Athe relief valve should open before the high pressure cutoutBthe relief valve should open and allow the excess refrigerant to flow to the receiverCthe high pressure cutout switch should operate before the relief valve opensDyou should close in on the suction valve

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.Atape faceBtapered faceCsurfaceDthinner face

单选题If the head pressure is too high,()Athe relief valve should open before the high-pressure cutoutBthe relief valve should open and let excess refrigerant go to receiverCthe high-pressure cutout switch should operate before the relief valve opensDclose in on the suction valve

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.Aneedle valveBnozzlesCpistonDspring

单选题Which of the following would not cause high suction pressure?()Ainsufficient refrigerationBleaky suction valvesCexpansion valve stuck openDsuction valve not adjusted properly

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?()Aspeed, torque, and horsepower productionBfiring order, valve timing, and valve liftCfuel consumption, efficiency, and cylinder pressureDscavenge pressure, compression ratio, and exhaust pressure

单选题A change in the quality of fuel atomization by a diesel engine fuel injector would be caused by a/an ()Aincrease in engine speedBincrease in cylinder turbulenceCleaking needle valveDreduction in cylinder turbulence

单选题The amount of fuel injection into a diesel engine cylinder by a unit injector, is controlled by()Athe firing pressure in the cylinderBa metering helix inside the pumpCvarying the physical length of the plunger strokeDvarying the clearance between the injector cam and the injector rocker arm

单选题Differential needle valves used in fuel injectors are directly closed by()Acam actionBspring forceCfuel oil pressureDfiring pressure

单选题A thermostatic expansion valve is properly controlling evaporator superheatAdjusting this valve to lower the superheat will result in a/an ().Aevaporator pressure decreaseBevaporator coil over-feedCevaporator capacity increaseDexpansion valve diaphragm rupture

单选题A fuel injection valve opening at pressure lower than normal will result in().Alate fuel injectionBearly fuel injectionChigh exhaust temperature from that cylinderDdecreased effective stroke from that injector

单选题The purpose of the delivery check valve used in a diesel fuel injection jerk pump is to ().Aassist in a quick cutoff of fuel injectionBallow oil backflow from the injector to the helixCreduce fuel oil pressure between injection strokesDmeter the quantity of fuel delivered

单选题When the heat load begins to increase, the needle valve of an expansion valve will()Amove in an opening directionBmove in a closing directionCeither open or closeDnot move at all

单选题The thermostatic valve has a throttling action, that is to say the valve can()Astop the refrigerant from flowingBforce the refrigerant to flowCcause the refrigerant pressure to riseDcause the refrigerant pressure to fall

单选题The low pressure side of a refrigeration system is considered to exist from the ().Aexpansion valve to the compressorBreceiver to the expansion coilCexpansion valve to the evaporatorDcondenser to the expansion valve

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?()AThe condenser and the expansion valveBThe king valve and the solenoid valveCThe compressor and the expansion valveDThe condenser and the solenoid valve

单选题A spring-loaded centrifugal flyweight governor responds to reduced engine load with an immediate increase in ()Apilot valve oil pressureBspeeder spring forceCcompensation needle valve clearanceDcentrifugal force on the flyweights