The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses

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• （）is harmful for fuel pumps, fuel valves, cylinder liner, exhaust valve seats, and the turbocharger blades as well.

  A . Bad combustion of the fuel B . Bad atomization of the fuel C . Liquid contaminants D . Solid contaminant

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• For an ordinary four-stroke engine the exhaust valves open （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• Exhaust temperature increases in all cylinders, the possible cause may be（） (1) increased scavenging air temperature (2) air in fuel pumps and fuel valves (3) fouling of air and gas passages

  A . (1)+(2) B . (1)+(3) C . (2)+(3) D . (1)+(2)+(3)

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• 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 （）

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• In an engine with air inlet valve and exhaust valve on its cylinder heads the fresh air will enter into the cylinder （） and the gases exhaust （）, there being an adequate overlap between the inlet opening and the exhaust closing.

  A . downwards；upwards B . upwards；downwards C . downwards；downwards D . upwards；upward

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• The bypass valve on a self-contained breathing device should be opened if（）.

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• 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-stroke

  A . (1) only is correct B . (2) only is correct C . both (1) and (2) are correct D . Neither (1) or (2) are correct

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  A . A gate valve B . A globe valve C . Any check valve D . Any needle valve

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• Excessive valve lash in an auxiliary diesel engine will cause the valves to open（）

  A . later and close sooner B . sooner and close later C . sooner and close sooner D . later and close later

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• The satisfactory operation of diesel engine exhaust valves usually depends on（）

  A . the proper back pressure B . the cooling water temperature C . correct timing and proper seating D . accurate metering and the exhaust temperature

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• The opening of an exhaust valve on a modem, large, low-speed, main propulsion diesel engine may be actuated by （）.

  A . direct action of cam shaft B . compressed air pressure C . hydraulic “push rods” D . direct action of the main piston moving dow

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• If the engine is naturally aspirated, or is a small high-speed type with a centrifugal turbocharger, the period of valve overlap（）,ie when both valves are（）, will be and the exhaust valve will close some 10°top dead canter（）.

  A . open；short；after B . closed；short；after C . open；long；before D . closed；long；before

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• For an ordinary four-stroke diesel engine the exhaust valves close （）.

  A . after TDC B . before TDC C . after BDC D . before BDC

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• （） in what position the engine stops there will always be at least one of the cylinders with its starting air valve open to admit compressed air to start the engine.

  A . Because B . Owing to C . For D . No matter

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• In a diesel engine, exhaust valves open before the intake ports are uncovered to （） Ⅰ.reduce pumping losses Ⅱ.reduce back pressure

  A . Ⅰonly B . Ⅱonly C . bothⅠand Ⅱ D . neitherⅠnor Ⅱ

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• Exhaust valve openings in a diesel engine cylinder head are made as large as practical to （）

  A . increase back pressure during the exhaust process B . facilitate periodic replacement of the valves C . reduce the pumping loss associated with scavenging D . reduce tension on valve spring

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• Leaky exhaust valve will result in which of the following?（） (1) high exhaust temperature; (2) low compression pressure; (3) low firing pressure.

  A . (1) and (2) B . (1) only C . (2) only D . (1),(2) and (3)

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• When the relief valve opens it discharges high pressure refrigerant vapor to the （）.

  A . liquid strainer B . refrigerant inlet of the condenser C . inlet side of the evaporator D . suction side of the compressor

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• In an ordinary four-stroke engine the exhaust valves open （）

  A . after TDC B . before TDC C . after BDC D . before BDC

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• Leaky exhaust valve will result in which of the following？①high exhausttemperature ②low compression ③low firing pressure

  A.① and ② B.② and ③ C.① ② and ③

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• 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_______.

  A.produce a scavenging effect in the combustion space B.equalize cylinder and exhaust manifold pressures C.alleviate the difference in valve size between the intake and exhaust D.flush out condensate that collects after each compression stroke

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• The exhaust valve opens before bottom dead center in a four stroke engine to______Iallow for blow down IIReduce pumping losses

  A.I only B.II only C.both I and II D.neither I nor II

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