轮机长
考试试题
[问答题]After the shut-off valve of the starting air receiver has been opened, the air flows at full pressure
through the filter to the main start valve “A” (with complicated construction), thereby applying pressure to
pipe between the main start valve “A” and the starting air control valve. Providing that maneuvering hand
wheel is in the "Stop" position, all other pipes are without pressure.
If the wheel is turned towards the “Start” position, a pawl above the starting air control valve is
actuated and the valve is opened, allowing air to flow to the main start valve “A”. It opens to allow a direct
through-flow of air. All cylinder starting valves are thus exposed to air pressure and, furthermore, air
flows to the starting air distributor, which is controlled by the camshaft. The distributor has a series of slide
valves arranged radially around the camshaft-one slide valve for each cylinder. These supply pilot air to the
cylinder starting valves with pistons in the “Start” position. The rotation of the engine crankshaft
commences, after which the cylinder starting valves are opened in the correct sequence. The crankshaft is
thus brought to speed of rotation necessary for compression and ignition.
When the maneuvering hand wheel is turned, the governor is actuated through a flexible cable setting
the fuel pumps. However, a fuel index limiting arrangement is inserted, which keeps the regulating shaft
and thus the fuel pumps at zero index during the starting process, ensuring that fuel is not injected into a
cylinder during the supply of starting air.
When the engine crankshaft has reached the necessary speed, the hand wheel is turned further past the
“Start” position with the result that the arm above the starting air control valve is released and the valve is
closed and vented. At the same time, the control piston in the main start valve “A” is also vented , thus
blocking the supply of air to the cylinder starting vales, the starting air distributor and the fuel index limiter.
Gradually, as the handle is turned further towards the maximum position. The governor increases the fuel
pump index and the crankshaft rotates more quickly. The governor ensures that the maximum permissible
speed is not exceeded.
(The following questions are based on the passage above)
[问答题]With many small package boilers, the automatic control sequence usually ensures that the boiler fire is
initially ignited from a diesel oil supply, and changed over to the usual source when ignition is completed.
With good management, to facilitate subsequent starting from cold, the fuel system of large boilers will
have been flushed through with diesel oil when the boiler was on light duty immediately prior to being
secured. When burning such diesel fuel it is essential for safety that only the correct (small) burner tip
should be used. It should be kept in mind that if fire does not light, immediately shut off fuel and vent furnace.
Complete ignition of fuel in the furnace is essential. The burner flame, the smoke indicator and the
funnel should be frequently observed. With satisfactory combustion, the flame should appear in candescent
（白热的）with an orange shade at the flame tip, and a faint brownish haze should show at the funnel. If on
first ignition the flame is uncertain, badly shaped and separates from the primary swirler, momentary
opening or closing of air register may correct.
