问题：
[单选] The crankcases of many diesel engines are kept under a slight vacuum to （）
improve fuel economy。increase the air charge velocity。reduce the risk of explosion。all of the above。
问题：
[单选] The rate of cylinder lubricating oil metered to each cylinder of a large low-speed main propulsion diesel engine is （）
the same, whether at sea, or during maneuvering。adjusted during each hour of operation while at constant RPM。higher at sea than while maneuvering。lower at sea than while maneuvering。
问题：
[单选] On a medium-speed main propulsion diesel engine, the crank-pin or crank journal bearings receive lubricating oil from （）.
a spindle lubricator。an oil jet。internal splashing。drilled passages in the crankshaft。
问题：
[单选] Fins are installed on the generating tube surfaces in waste heat boilers to （）.
prevent soot fires in the exhaust system。prevent exhaust gas erosion of the tubes。increase the velocity of exhaust gas flow。increase the rate of heat transfer。
问题：
[单选] The crankcase of many diesel engines are kept under a slight vacuum by the （）.
scavenging action of the piston。piston type vacuum pump taking suction off a differential manometer。gland exhausting manometer。crankcase exhaust fa。
问题：
[单选] Lubricating oil systems for diesel engine journal bearings are usually lubricated by which of the following types of lubricating oil systems?（）
Splash。Gravity。Pressure。Bypa。
问题：
[单选] Which of the following conditions can cause above normal air temperature to develop in the intake manifold of a four-stroke/cycle turbo-charged diesel engine?（）
Clogged air intake falters。Piston blow-by。A defective after-cooler。Faulty exhaust valve。
问题：
[单选] If the feed pump for an auxiliary boiler fails to deliver the feed water to the boiler, the cause maybe （）.
high steam pressure in the boiler。abnormally high feed water temperature。abnormally high boiler water temperature。steam demand exceeding feed pump capacity。
问题：
[单选] When there is a flame failure in an automatically fired auxiliary boiler, the （）.
air supply is shut off。fuel supply is shut off。water supply is shut off。safety valve lift。
问题：
[单选] Excessive vibration of an automatically fired auxiliary boiler can be caused by （）
air or water in the furnace。combustion pulses。fuel oil pump failure。flame failure。
