单项选择题

The rate of heat transfer in a water-tube auxiliary boiler can be increased by （）.

A.operating the boiler at less than normal water level
B.installing fins on the firesides of water-tubes
C.increasing the amount of excess air to the burners
D.treating the boiler water with chemical oxygen scavengers

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单项选择题

The term “proper metering”, as applied to a diesel fuel injection system, can be best defined as （）.

A.delivering the same quantity of fuel to each cylinder for each power stroke according to engine load
B.maintaining the metering adjustment for a reasonable period under all load conditions
C.timing fuel injection to obtain maximum power and good fuel economy
D.distributing the fuel to all parts of the combustion chamber for proper combustion

单项选择题

Connecting rods in a diesel engine are used to connect the （）.

A.engine to the bed
B.rocker arm to the camshaft
C.crankshaft to the gear train
D.piston to the crankshaft