In some type of two-stroke engines, be...

单项选择题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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1.单项选择题In a two-stroke engine, there are always a series of openings known as （）, and in some circumstances, there are also openings known as （）, in the part of the cylinder liner.

A.scavenging air ports；exhaust ports
B.inlet ports；scavenging air ports
C.scavenging air ports；inlet ports
D.exhaust ports；inlet ports

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2.单项选择题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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3.单项选择题（）is the main reason that reduces the power advantage of a two-stroke engine over a same size four-stroke one to about（）

A.Inefficient scavenging；twice
B.Inefficient scavenging；1~8 times
C.Fewer strokes in a circle；twice
D.Fewer strokes in a circle；1~8 times

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4.单项选择题In a diesel engine, when the fuel is injected into the cylinder,（）

A.the piston is just coming upward from the bottom dead center
B.the piston has moved about one-fifth of the way up
C.the piston has moved most of the way up and almost reached the TDC
D.the piston has just past the TDC

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5.单项选择题One of the differences between a two-stroke engine and a four-stroke engine is,（）

A.a two-stroke engine can’t work without cylinders
B.a two-stroke engine can’t work without pistons
C.a two-stroke engine can’t work without crankshafts
D.a two-stroke engine can’t work without a blower

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6.单项选择题One of the differences between a two-stroke engine and a four-stroke engine is,（）

A.a two-stroke engine works without exhaust operation
B.a two-stroke engine works without compression stroke
C.a two-stroke engine works without expansion stroke
D.a two-stroke engine works without suction operation

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7.单项选择题In a diesel engine,（） works as working medium and changes the heat energy to mechanical energy, changes the reciprocating movement to rotary moment（）

A.fuel spray； the burning of the fuel
B.the burned gas mixture； connecting rod
C.medium shaft；crankshaft
D.the burned gas mixture； piston rod

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8.单项选择题In a diesel engine, offers the heat energy directly（）； works as working medium and changes the heat energy to mechanical energy（）

A.the burning of the fuel； medium shaft
B.fuel spray； fresh air
C.fuel； fuel spray
D.the burning of the fuel； the burned gas mixture

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9.单项选择题A propeller, in order to operate efficiently, must rotate at a relatively （） speed.

A.high
B.low
C.fast
D.lowly

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10.单项选择题Why a gearbox is needed in a ship driven by a medium-speed diesel engine?（）

A.To reduce the main engine speed
B.To increase the main engine speed
C.To govern the main engine speed
D.To fix the propeller shaft

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