第三次技术革命，开始于40年代的美国，其主要标志是（）。

Cold weather starting of a diesel engine may be made easier by .

A.decreasing the compression ratio

B.using a special fuel having a high ignition temperature

C.increasing the starting air supply

D.heating the jacket water

A.increasing the quantity of starting air

B.increasing the lube oil pressure

C.heating the engine fuel supply

D.heating the engine coolant

A.increasing the quantity of starting air

B.increasing the lube oil pressure

C.heating the engine fuel supply

D.heating the engine jacket water

An electric heater built into some smaller diesel engines is used to _____.

A.raise lube oil viscosity for easier starting in cold weather

B.increase air inlet temperature

C.increase compression ratio

D.increase jacket water temperature for easier starting in cold weather

Burning fuel with a high sulfur content in a diesel engine will ＿.

A.increase thermal efficiency

B.cause clogging of the fuel system

C.increase the ability of the engine to start in cold weather

D.produce corrosion in the cylinder and exhaust system at low loads

A.increase in starting air pressure

B.increase in lube oil viscosity

C.compression expansion device

D.jacket water heater

Fuel oil having a low cetane rating could result in________.

A.improved cold weather starting

B.excessive fuel oil consumption

C.reduced ignition lag

D.smoother engine operation

According to the passage, keeping the engine running idly______.

A．will just waste gas

B．will warm it up more quickly

C．will make it work more efficiently

D．is necessary in cold weather

According to the passage, keeping the engine run idly .

A．will just waste gas

B．will make it work more efficiently

C．will warm it up more quickly

D．is necessary in cold weather

A.rotary compressors

B.reciprocating compressors

C.centrifugal compressors

D.screw compressors