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Afterlearning about how the engine works, we remember there are two things that aremixed together for combustion, fuel and air. Let’s learn somethings about thefuel system.
在学习了引擎工作原理之后，我们知道燃油和空气两种物质混合后可以燃烧。现在我们来讨论燃油系统。
Thefuel system is designed to bring fuel from fuel tanks to the engine. In generalaviation airplanes, fuel systems can be broken down to the two subsystems:Gravity-fed systems and fuel pump systems. High wing airplanes such as theCessna 172 are normally designed to be gravity-fed systems. Because the fueltank is inside the wing which is located above the engine, gravity can naturallypull the fuel from the tank to the engine. Although in normal operation, a fuelpump is not required, many high wing aeroplanes are still equipped with somesorts of fuel pump, either an engine driven, electronically powered or both, asa backup for emergency operations.
Low wing aeroplanes such as the Piper Arrow,a fuel pump is required to send the fuel from the tanks to the engine. Sincethe fuel is located below the engine, it is simply impossible for gravity tosend the fuel upwards. For this reason, low wing aeroplanes are designed withfuel pump systems. Normally there are two fuel pumps. One of the fuel pump isengine driven, and the backup is electrically driven.
Some aeroplanes areequipped with fuel primer. The fuel primer allows fuel to be injectedstraightly into the cylinder prior to engine start. Fuel priming is especiallyuseful during cold operations. While some aeroplanes are equipped with fuelprimer, others like Cessna 172 are not. However, we still like to enjoy thebenefits of priming the engine, herefore it is possible to prime the engine ofthe Cessna 172 using the electrical fuel pump.
燃油系统的作用是将燃料从油箱输运至引擎。通航飞机的燃油系统可分为两种类型：重力输运系统和燃油泵浦系统。上单翼飞机，如Cessna（塞斯纳） 172 使用重力输运系统。因为位于机翼内的油箱高于引擎，燃油可在重力作用下由油箱流向引擎。尽管在正常运行状态下不需要燃油泵浦系统，许多上单翼飞机仍然装备有某种形式的燃油泵，包括引擎驱动式、电驱动式或混合式，以备应急情况下使用。下单翼飞机，如Piper Arrow（派珀），需要配备燃油泵以将燃油从油箱送至引擎。由于燃油低于引擎，无法简单依靠重力向上输送燃油。因此下单翼飞机需要配备燃油泵浦系统。一般配备有两套燃油泵浦系统，一套为引擎驱动，另一套电动燃油泵作为备份。一些飞机还配备启动注油泵。启动注油泵在引擎启动前将燃油直接注入引擎汽缸中。启动注油在寒冷条件下运行时特别有效。有些飞机配备启动注油泵，另一些飞机如Cessna 172则不配备该系统。然而，飞行员可以使用电动燃油泵达到启动注油的效果。
Fuelis stored in fuel tanks, which is usually located inside the wings. These tanksare filled from the top. There is a cap out of the top that is easily twistedoff.
And gas is pumped into that tank until it is visually full. This cap isusually vented to allow outside air pressure to enter the fuel tank and get ridof vacuum from being created inside of the fuel tank. If the fuel tank did nothave a vent, fuel will initially flow from the tank, but as it empties, therewill be nothing to replace that space which will create vacuum and eventuallystop fuel flow to the engine.
Therefore, manufacturers vent the tanks to allowair to replace the fuel that is leaving the tank to the engine. Some aeroplanesnot only have vented fuel caps, but they also have fuel vents that protrudefrom the wings.
As the aeroplanes fly through the air, air enters this vent andis pushed into the fuel tank.
存储燃油的油箱通常位于机翼中，一般由顶部加注。油箱盖位于油箱顶部，可以通过旋拧打开。燃油加注时通过目视观察至加满。油箱盖通常设计有通气孔以平衡油箱内外气压，防止油箱内产生真空。在初始阶段，燃油可从不配备通气孔的油箱中流出，随着油箱排空，燃油流出形成的空间无法被填充从而形成真空，最终会导致燃油无法从油箱中流向引擎。因此，制造商在油箱上设置通气孔使空气填充燃油流向引擎后在油箱中排空形成的空间。一些飞机除了在油箱盖上有通气孔外，还配备从机翼上伸出的通气孔。当飞机在空气中飞行时，空气通过通气孔被推送入油箱。
Alsoinside the fuel tanks are fuel sensors. These fuel sensors send information tothe fuel gauge which shows the pilots the amount of fuel in the tank. Thesesensors work in many different ways depending on the manufacturers of theaeroplane. It is absolutely critical to visually verify the amount of fuel inthe tank.
Never entirely trust the fuel gauges. After visually verify thequantity of the fuel in the tanks, it is also equally important to confirmthere is no containments in the fuel, such as water. The fuel tanks areequipped with fuel sumps or drains.
The pilot uses the special fuel sump cup toallow the fuel flow out of the tank and into the cup. At that point, the pilotvisually verifies there is no impurities in the fuel. Most general aviationaeroplanes utilize 100-low-lead fuel which is blue in color. Therefore, notonly should the pilot check for impurities, the color of the fuel should alsobe inspected to ensure that the proper fuel was pumped into the tank.
燃油传感器也位于油箱中。燃油传感器向油量计发送信息以向飞行员显示油箱中的油量。燃油传感器根据飞机制造商有不同的工作方式。使用目视方式确认油箱中的油量是至关重要的。永远不要完全依赖油量计的示数。通过目视确认油箱中油量的同时，检视油箱中燃油没有被水等杂质污染也同等重要。油箱通常配备有集油槽或放油口。飞行员使用特制的集油杯从油箱中取出燃油，观察并确认燃油中不含杂质。大多数通航飞机使用呈蓝色的100#低铅燃油。因此，飞行员除了检视燃油杂质外，还需确认油箱中已加注正确的燃油。
Anothercomponent found in the fuel system is the fuel selector. The fuel selectorusually has 4 different positions. The some of the manufactures may have fewerpositions. The 4 positions are left, right, both and off. If the fuel selectoris in the left position, the fuel is only drawn from the left tank.
Similarly,if the fuel selector is in the right position, the fuel is only drawn from theright tank. In normal operation, the fuel selector is in the both position,which allows the fuel from the both left and right tanks to be sent into theengine. In the off position, fuel cannot pass into the engine which stops thefuel flow to the engine.
Ordinarily the fuel selector is only placed in the offposition in emergency situations such as an engine fire. The Cessna 172 onlyhas 3 positions on its fuel selector, left, right and both. A fuel shut offvalve is instead of use to shut off the fuel supply. This valve is located justabove the fuel selector and can be activated by pulling out the knob.
燃油系统中另一个部件为燃油选择器。燃油选择器通常有4个档位，一些厂商的档位则可能更少。4个档位分别是：左侧、右侧、双侧和关闭。当选择器档位位于左侧时，仅由左侧油箱供油；同理，档位位于右侧时，仅从右侧油箱供油。在正常运行中，燃油选择器置于双侧档位，由双侧油箱同时向引擎供油。一般仅在紧急情况，如引擎起火时将供油选择器档位置于关闭档位。Cessna 172的供油选择器有3个档位，左侧、右侧和双侧，并使用一个燃油关闭阀门以切断供油。此阀门位于燃油选择器上方，可以通过拉出旋钮触发。
听译支持:
中国民航大学 张喆
东航工技武汉公司 刘谦
编辑：小G
微信号faachina
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