单选题For an ordinary four-stroke engine the exhaust valves open （）.Aafter TDCBbefore TDCCafter BDCDbefore BDC
单选题
For an ordinary four-stroke engine the exhaust valves open （）.
A
after TDC
B
before TDC
C
after BDC
D
before BDC
参考解析
解析：
暂无解析
相关考题：
Any increase in the exhaust back pressure of a four-stroke/cycle diesel enginewill( ).A.reduce engine horsepower outputB.aid in silencing the exhaust noiseC.increase the mean effective pressureD.contribute to effective cylinder scavenging
The closing of the exhaust valves used on a modern, large, low-speed, main propulsion diesel engine may be directly provided by_______.A.large conical springsB.compressed air pressureC.hydraulic pressureD.exhaust gas pressure
Fuel is admitted to a diesel engine cylinder through the ______.A.injector nozzlesB.carburetorC.exhaust portsD.intake valves
单选题For an ordinary four-stroke diesel engine the exhaust valves close （）.Aafter TDCBbefore TDCCafter BDCDbefore BDC
单选题A diesel engine cylinder head can crack as a result of （）Aa leaking seal ringBheat transfer from exhaust valvesCrestricted cooling passagesDoverheated intake valves
单选题For an ordinary modem marine four-stroke engine the inlet valves close （）.Aafter TDCBbefore TDCCafter BDCDbefore BDC
单选题Air scavenging of a diesel engine cylinder（）Ablows out the exhaust gasesBsupplies oxygen for combustionCcools the valves and cylinder wallsDall of the above
单选题The period of valve overlap is when （）.Athe inlet valve is openBthe exhaust valve is openCboth valves are closeDboth valves are open
单选题Valve overlap is the period during which （）.Athe inlet valve is openBthe exhaust valve is openCboth valves are closedDboth valves are open
单选题In a four-stroke cycle diesel engine the intake valves open （）Abefore TDC and close after BDCBafter TDC and close after BDCCbefore TDC and close before BDCDafter TDC and close before BDC
单选题In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressureAⅠonlyBⅡonlyCbothⅠand ⅡDneitherⅠnor Ⅱ
单选题A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) MEP is lower and the scavenging air is cooling the exhaust gases (2) valve overlap in a four-strokeA(1) only is correctB(2) only is correctCboth (1) and (2) are correctDNeither (1) or (2) are correct
单选题The satisfactory operation of diesel engine exhaust valves usually depends on（）Athe proper back pressureBthe cooling water temperatureCcorrect timing and proper seatingDaccurate metering and the exhaust temperature
单选题The size of the exhaust valve opening is （）Amost critical in a four-stroke cycle diesel engineBmost critical in a two-stroke/cycle diesel engineCmost critical in a four-stroke/cycle diesel engine if it is turbochargedDof equal importance in a two-stroke/cycle diesel engine as in a four-stroke/cycle diesel engine
单选题The loss of the diesel engine cylinder air charge through leaky valves, piston rings, worn or scored liners, would be indicated by which of the following sets of conditions?（）ALow compression pressure and high exhaust temperatureBLow firing pressure and high exhaust temperatureCLow compression pressure and low exhaust temperatureDLow firing pressure and low exhaust temperature
单选题The period when both inlet valves and exhaust valves are open is referred to as （）.Avalve loopBvalve uniflowCvalve overlapDvalve grinding
单选题During the valve overlap period, the exhaust pressure of a turbochargers, four-stroke/cycle diesel engine must be less than the intake manifold pressure to ensure （）Aeffective cylinder scavenging and coolingBconstant pressure from the turbochargersCcooler operation of the exhaust systemDeffective constant pressure for turbocharger operation
单选题If the valve tappets in a diesel engine are set at greater clearances than those specified by the engine manufacturer, those valves will （）Aopen late and close earlyBopen late and close lateCfail to open when the engine is coldDfail to open at normal operating temperature
单选题For an ordinary four-stroke engine the inlet valves open （）Aafter TDCBbefore TDCCafter BDCDbefore BDC
单选题Diesel engine valve springs function to （）Ahold the valves openBkeep the valves off their seats until the exhaust stroke is completedCclose the valvesDopen inlet valves when the air injection cycle begins
单选题Any increase in the exhaust back pressure of a four-stroke/cycle diesel engine will （）.Areduce engine horsepower outputBaid in silencing the exhaust noiseCincrease the mean effective pressureDcontribute to effective cylinder scavenging
单选题Which of the following conditions can cause above normal air temperature to develop in the intake manifold of a four-stroke/cycle turbo-charged diesel engine?（）AClogged air intake faltersBPiston blow-byCA defective after-coolerDFaulty exhaust valves
单选题One of the differences between a two-stroke engine and a four-stroke engine is,（）Aa two-stroke engine works without exhaust operationBa two-stroke engine works without compression strokeCa two-stroke engine works without expansion strokeDa two-stroke engine works without suction operation
单选题A turbocharged, four-stroke/cycle diesel engine has a larger valve overlap than a naturally aspirated four-stroke/cycle diesel engine, in order to in crease the （）.Atemperature of the exhaust gasesBenergy supplied to the turbochargerCair pressure to the intake manifoldDpurge of exhausted gases from the cylinders
单选题Scavenging in a turbocharged, four-stroke/cycle diesel engine is accomplished（）Aduring the valve overlap periodBwith only the exhaust valve openCat a pressure below atmosphericDwithout cooling the cylinders or pistons
单选题A two-stroke diesel engine exhaust temperature will be lower than a four-stroke diesel engine of the same displacement because the （） (1) scavenging air is cooling the exhaust gases (2) exhaust cycle time is longerA(1) onlyB(2) onlyCboth (1) and (2)Dneither (1) nor (2)
单选题In a turbocharged four-stroke/cycle diesel engine, the exhaust valve remains open until after top dead center and the intake valve opens before top dead center to（）.Aproduce a scavenging effect in the combustion spaceBequalize cylinder and exhaust manifold pressuresCalleviate the difference in valve size between the intake and exhaustDflush out condensate that collects after each compression stroke