单选题Differential needle valves used in fuel injectors are directly closed by（）Acam actionBspring forceCfuel oil pressureDfiring pressure
单选题
Differential needle valves used in fuel injectors are directly closed by（）
A
cam action
B
spring force
C
fuel oil pressure
D
firing pressure
参考解析
解析：
暂无解析
相关考题：
If the engine does not start on air, it may be due toA.low compression of the fuel pumpsB.incorrect timing of fuel pumpsC.the starting air valves stuckD.air-locks in fuel oil pipeline
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
Cooling water is circulated through______in some injectors.A.the nozzleB.the nozzle tipC.the internal passagesD.the fuel re-circulated
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
Injectors for use with heavy fuel oil must be cooled by either water or light oil to_____.A.prevent heat corrosion to internal componentsB.increase fuel delivery rate and economyC.prevent pre-ignitionD.avoid carbonization of the nozzle tips
_______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
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Maintaining the close tolerances in diesel fuel pumps and injectors requires the use of（）.Afuel/water separatorsBday tanksCinjector test standDfuel filters
单选题Which of the valves listed should be used either in the fully opened or the fully closed position?（）AA gate valveBA globe valveCAny check valveDAny needle valve
单选题If the needle valve in a fuel injection nozzle sticks open （）.Ano fuel will be delivered through the nozzleBthe nozzle will overheat and crackCtime of injection will changeDfuel will leak into the drain line
单选题If the engine can be started and maneuvered on high viscosity fuel, the （）of the fuel reaching the injectors should be raised to such a point that the viscosity is less than the required value, ie27c St.ApressureBtemperatureCviscosityDdensity
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In the cylinder head of a two-stroke/cycle diesel engine, valves are used for（）Aair intakeBa fuel outletCcooling water inletsDexhausting combustion gas
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Injectors for use with heavy fuel oil must be cooled by either water or light oil to （）Aprevent heat corrosion to internal componentsBincrease fuel delivery rate and economyCprevent pre-ignitionDavoid carbonization of the nozzle tips
单选题Thermostatic steam pressure reducing valves are used in the fuel oil service system to control the（）Adouble bottom fuel oil tank temperatureBheater supply steam flowCpressure of the fuel supplied to the burnersDattemperator steam flow in the heater discharge circuit
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If the engine does not start on air, it may be due to （）Alow compression of the fuel pumpsBincorrect timing of fuel pumpsCthe starting air valves stuckDair-locks in fuel oil pipeline
单选题Starting air valves are held firmly on their seats by（）Acam rollers on the camshaftBspring forceCair pressure on top of the valve differential pistonDair pressure on the bottom of the valve differential piston
单选题In an elector-hydraulic steering system, rudder shock is limited by（）Aa differential gearBreturn springsCa hydraulic accumulatorDrelief valves
单选题Faulty operation of diesel engine fuel injection nozzles can be a direct cause of（）.Aexcessive fuel nozzle holder coolingBsediment in the fuel supplyCdistortion of the fuel spray patternDimproper atomization of the fuel
单选题Movement of the diaphragm or bellows is （） by a linkage to a needle or pointer display to indicate the differential pressure between two sides of the diaphragm or bellows.AmeasuredBrecordedCtransferredDcontrolled
单选题Which of the fuel injection systems listed uses a spring loaded differential spray needle valve and individual pump for each cylinder?（）ACommon-rail injectionBAir injectionCJerk pump injectionDDistribution injection
单选题Fuel injectors used in heavy fuel oil systems are usually provided with cooling to reduce（）.Acold corrosion of the nozzlesBfuel viscosity for better atomizationCcarbon accumulation on the nozzlesDfuel detonation in the cylinders
单选题Proper filtering and straining of fuel oil is important because the （）.Afuel oil pump will over-speed if dirt is not removedBfuel oil transfer pumps cannot tolerate small amounts of dirt in the oilCfuel injectors may be damaged by foreign particles in the fuel oilDdirty fuel will clog the intake air filter
单选题The direct acting mechanical governor used with some small diesel engines, controls fuel flow to the engine by（）Agovernor flyweight action on a pilot valve which controls fuel injectionBgovernor flyweight motion acting on fuel controls through suitable linkageCpositioning a butterfly valve in the fuel delivery system positioningDa servomotor piston attached to the fuel controls
单选题In some type of two-stroke engines, besides some small holes for（）, starting valve, safety valve, indicator cock, and central opening in each cylinder cover for mounting the（）Afuel valves；exhaust valveBexhaust valves；inlet valveCfuel valves；inlet valveDexhaust valves；fuel valve