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

A、A.Ⅰ only

B、B.Ⅱ only

C、C.both Ⅰ and Ⅱ

D、D.neither Ⅰ nor Ⅱ

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更多“The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses The exhaust valve opens before bottom dead center in a four stroke engine to（） Ⅰ.allow for blow down Ⅱ.Reduce pumping losses”相关的问题

第1题

[单选题] In comparison to exhaust valves, intake valves of diesel engines may be fabricated from low alloy steels because （）.

A、the beveled edges of the intake valves provide for serf-centering during seating B、intake valves utilize stellite-coated valve seat inserts which reduce wear C、the volume of air passing through intake valves is less than the volume of air passing through exhaust valves D、intake valves are less affected to the corrosive action of exhaust gases

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第2题

[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（）

A、fuel valves；exhaust valve B、exhaust valves；inlet valve C、fuel valves；inlet valve D、exhaust valves；fuel valve

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第3题

[单选题] The period of valve overlap is when （）.

A、the inlet valve is open B、the exhaust valve is open C、both valves are close D、both valves are open

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第4题

[单选题] Valve overlap is the period during which （）.

A、the inlet valve is open B、the exhaust valve is open C、both valves are closed D、both valves are open

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第5题

[单选题] 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；upwards

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第6题

[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（）.

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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第7题

[单选题] 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 springs

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第8题

[单选题] The diesel engine valve subjected to most severe conditions of service is the （）.

A、cylinder exhaust valve B、air starting valve C、air inlet valve D、cylinder relief valve

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第9题

[] Diesel engine valve springs function to （）

A、A.hold the valves open B、B.keep the valves off their seats until the exhaust stroke is completed C、C.close the valves D、D.open inlet valves when the air injection cycle begins