单项选择题“The use of a poor quality oil can lead to rapid deterioration of its properties with the resultant formation of deposits in the piston crown which in turn results in a considerable reduction in heat transfer with subsequent overheating and thermal cracking” According to this sentence, we can know that the principle reason of the overheating and thermal cracking is()

A.the use of a poor quality oil
B.the deterioration of its properties
C.the formation of deposits
D.the reduction in heat transfer ability


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3.单项选择题In some diesel engine designs,()the injection of cylinder oil is timed to impinge when the piston and only impinge on()

A.is coming upward;cylinder ring belt
B.is going downward;piston ring belt
C.is coming upward;piston ring belt
D.is going downward;cylinder ring belt

4.单项选择题()diesel engines generally have two systems of lubrication:()a total loss system feeding and a circulating system lubricating the running gear and cooling the pistons.

A.Large crosshead type;crossheads
B.High speed;the cylinders
C.Large crosshead type;the cylinders
D.Four-stroke;pistons and cylinders

5.单项选择题The following options are all the functions of lubricating oil except()

A.removing heat and deposits
B.neutralizing acidic products
C.lubricating
D.improving combustion efficiency

6.单项选择题The air distributor is conventionally driven by() and distributes into each cylinder by() certain sequence.

A.camshaft;fresh air
B.camshaft;starting air
C.electronic motor which is controlled by a computer;fresh air
D.electronic motor which is controlled by a computer;starting air

7.单项选择题When an engine is starting and has got a sufficiently high speed, say about 20 rpm,()

A.the starting air supply is cut off and fuel is injected into the cylinders
B.the fuel feeding is cut off and the turning gear is put in
C.the starting air supply is cut off and turning gear is taken out
D.the electric blower is shut down and fuel is injected into the cylinders

8.单项选择题When starting an engine, the compressed air enters the cylinder when the corresponding piston is in position of its()

A.suction stroke
B.compression stroke
C.power stroke
D.exhaust stroke

9.单项选择题The starting air entering the cylinder begins when the piston()

A.has nearly come to the TDC
B.has just past the TDC
C.has nearly come to the BDC
D.has just past the BDC

10.单项选择题In the starting system, the automatic valve is controlled by(), and the cylinder start valves are controlled by()

A.pilot air;pilot air
B.handle;solenoid
C.handle;pilot air coming through the distributor
D.solenoid;pilot air coming through the distributor