單項選擇題The diameter of a piston is usually less at the crown than at the skirt, in order to （）.

A.facilitate the installation of piston rings
B.allow for the expansion of the piston during operation
C.prevent crankcase vapors from entering the combustion chamber
D.reduce wearing of the upper cylinder liner


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1.單項選擇題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 down

2.單項選擇題

In a diesel engine, excessive cylinder liner wear will cause （）
(1) increased blow-by
(2) wear between the piston ring and groove

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

3.單項選擇題Engine displacement is equal to the cylinder （）.

A.area times the stroke
B.area times the stroke, times the number of cylinders
C.volume times the stroke
D.volume times the stroke, times the number of cylinders

4.單項選擇題Auxiliary boilers are divided into several classifications, one of which is （）.

A.water-tube supercritical circulation
B.water-tube forced circulation
C.fire-tube controlled circulation
D.fire-tube express circulation

5.單項選擇題Load control on a diesel engine is accomplished by （）.

A.regulating the speed of the turbocharger
B.rotating the fuel injector pump plunger
C.regulating the speed of the fuel oil transfer pump
D.changing engine timing