单项选择题
In modern installations, the main engine and the standby auxiliary engines（）
A.can be started at low temperature and are free from preheating
B.usually are preheated by steam before being started
C.are kept at a constant temperature and free from preheating
D.are kept at a low temperature to save energy
相关考题
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单项选择题
In order to maintain a constant outlet water temperature of 80-85℃ from the engine, a three-way valve is installed（）
A.at the jacket cooler outlet to control the flux through the engine
B.at the jacket cooler outlet to control the flux through the cooler
C.at the engine outlet to control the flux through the engine
D.at the engine inlet to control the flux through the engine -
单项选择题
About the jacket water, that of the auxiliary engines usually（） is circulated by pumps, and the main engine usually （）
A.an engine-driven；as well
B.an engine-driven；has an independent pump
C.an independent；as well
D.an independent；has an engine-driven pump -
单项选择题
The cooling system（） needs least maintenance work for in this kind of system（）
A.open；the minimum components
B.open；the high cooling efficiency
C.central；there are more coolers and a extra set of pumps
D.central；there is only one component contacts seawater
