单项选择题

Cylinder linings constructed as an integral part of the block, are characterized by which of the following disadvantages?（）

A.They conduct heat poorly
B.They are expensive
C.They cannot be replaced
D.They require special tools for removal

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单项选择题

When running a large, low-speed, main propulsion diesel engine on heavy fuel, which of the following precautions should be observed when switching back over to diesel oil?（）

A.The diesel oil must never be allowed to mix with the heavy fuel
B.The temperature of the fuel from the pre–heater should be gradually reduced after switching over the three–way valve
C.The heating steam to the pre-heater should be secured as soon as the diesel fuel passes through the three-way valve
D.The heating steam must be secured before the diesel oil passes through the three-way valve

单项选择题

Before shutting off the fuel supply to stop a medium or high–speed diesel engine, why is it necessary to allow the engine to idle for a few minutes?（）

A.To prevent internal damage form local overheating
B.To ensure the fuel nozzles are flushed clean
C.To clear the smoke stack
D.To let the waste heat boiler reduce its rate of steam generation