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在10000米的高空上，飞机内部的空气是从何而来？这些空气又是经过什么部件才能到达旅客所在的客舱？而且又是什么样的系统来确保飞机的供气可以满足旅客所需的温度和环境压力？而且在飞机上这些“空气”还会起到什么作用？这篇文章简单的为大家介绍一下飞机的引气系统。（以737-800为例）
首先，飞机的引气来源有发动机，APU（辅助动力装置），还有地面气源，而飞机在空中时 引气主要来自发动机 The pneumatic system suppliescompressed air to the airplane usersystems. These are the sources ofpneumatic power: *Engine1 bleed air system *Engine2 bleed air system *Auxiliarypower unit (APU) bleed air system *Pneumaticgtion. 在空中时，空气会经过风扇进入发动机的低压压气机，经过压缩后，进入高压压气机，再次压缩后进入燃烧室，燃烧产生能量从而转动发动机，而发动机的引气就是来自高压压气机的5级和9级也称为低压级引气和高压级引气（高压压气机一共有9级） The primary air flow goesinto the core of the engine. The booster increases thepressure of this air and sends it to the HPC. The HPC is a nine-stagecompressor. It increases the pressure of the air from the LPC and sendsit to the combustor. The HPC also supplies bleed air forthe aircraft pneumatic system and the engine air system. 那飞机究竟是使用5级引气还是9级引气呢？ 当发动机在低转速时，气源系统使用9级引气，因为此时5级引气不能满足气源系统的需求，而当发动机达到高转速时，9级活门关闭5级活门打开，由5级活门供气，这样可以节省燃油。这个功能是由高压调节器控制的。 Engine Bleed Air Bleed air comes from the 9thand 5th stages of the engine high stage compressors. At lowengine speed, the pneumatic system uses 9th stage bleed air. 5thstage air is not sufficient for pneumatic system demands atlow engine speeds. At low engine speed the highstage regulators and high stage valves control the pressureof the engine bleed air. At low engine speed the 5thstage check valves prevent reverseflow.At high engine speed the high stage valves close and the 5th stage check valves opento supply bleed air to the pressureregulatingshutoff valves. 经过5级，9级活门的引气来到压力调节和关断活门（PRSOV） 由压力调节器（BAR）和PRSOV来控制发动机到气源总管的空气流量。 The bleed air regulators andpressure regulator and shutoff Valves（PRSOV） control the flow of engine bleed airto the pneumatic Manifold. 那PRSOV和BAR究竟起到什么作用呢？ 首先PRSOV的功能有 1.关断发动机引气 2.发动机引气压力调节 3.发动机引气温度限制。 The bleed air regulator (BAR)operates the pressure regulator and shutoff valve (PRSOV).ThePRSOV controls the flow of bleed air from the engine. These are the PRSOV controlfunctions: *Shutoffof engine bleed air *Pressureregulation of engine bleed air (42 psi nominal) *Temperaturelimitation of engine bleed air (450F/232C). 在正常操作的时候，当驾驶舱的引气电门设置到ON位时，就有一个信号到达BAR来控制PRSOV打开，而当引气电门设置到OFF位时，信号到达BAR控制PRSOV关闭。（受驾驶舱电门控制） During normal operations,when the engine BLEED switch is settoON, a signal goes through the ACAU to command the BAR solenoid valve to open. When the engine BLEED switch is setto OFF, a signal goes to commandthe BAR solenoid valve to Close. 当火警手柄被抬起时，也会有一个信号到达BAR来直接控制PRSOV关闭，（当发动机着火时可以关闭引气） When the fire switch is up, asignal goes directly to the BAR solenoid valve to close thevalve BAR还在以下情况时关闭PRSOV 1.发动机启动活门未关闭（防止反流） 2.当温度引气温度达到490华氏度（254摄氏度）或压力达到220PSI时（过热和超压保护） Relays in the ACAU controlthe BAR solenoid valve to close for these conditions: *Enginestart valve not closed (reverse flow protection) *Enginebleed trip off conditions (490F/254C overheat or 220 psi overpressure protection). 而在引气温度达到490华氏度之前，还有一个防止超温的措施，当引气温度达到450华氏度时，PRSOV就开始减小活门开度，来使温度降低。（受450F电门控制） The 450F (232C) thermostatbleeds off pressure that operates the pressure regulator andshutoff valve (PRSOV). This occurs when engine bleed airtemperature is more than 450F (232C). 以上就是BAR和PRSOV的功能，总体来说就是BAR控制PRSOV，而它们的功能就是调节引气系统的温度和压力，防止超温超压。 而此时从PRSOV出来的引气，经过高压压气机压气机压缩，温度较高，所以从PRSOV出来的引气还需要经过预冷器来降低引气温度，预冷器活门控制预冷器冷却空气的流量，冷却空气来自风扇外涵道。 When the pressure regulatingand shutoff valve (PRSOV) is open, bleed air goes throughthe precooler and to the pneumatic manifold. While thebleed air goes through the precooler, fan air removesthe heat and discharges as fan exhaust air. The fan exhaustair flows over the engine core 而预冷器活门受2个部件控制，一个是390F温度传感器，另一个就是大翼防冰电磁活门。 A precooler control valvecontrols the amount of fan air that flows through the precooler.These two devices control the precooler control valve: *Theprecooler control valve sensor *Wingthermal anti-ice (WTAI) solenoid valve. 其中390F传感器起到控制引气温度的作用，它感受引气温度，当温度达到390F（199C）时，预冷器活门开始打开，随着温度的升高活门开度也逐渐变大，冷却空气的流量也随之增加，当温度达到440F(227C)时活门便完全打开。 The sensor ball valve starts to open at 390F (199C) and isfull open at 440F (227C) (nominalvalues). 而大翼防冰电磁活门的作用：因为大翼防冰系统是为了防止大翼前缘结冰，而使用引气来给大翼加热，在空中时，会有足够的气流流过大翼，但是在地面时就没有足够的气流，这就会使大翼温度过高导致大翼前缘装置损伤。为了避免这种情况的发生，当大翼防冰电磁活门在地面接通时，预冷器活门会自动开到最大，降低引气温度来防止大翼前缘装置过热损伤。 The wing thermal anti-icingsystem prevents ice formation on the wing leading edge duringground operations and in flight. During flight there is alarge airflow over the wing. This airflow has a cooling effect on the leadingedges. The wing thermal anti-icing system heat outputis enough to overcome this cooling effect. When the wing thermalanti-icing system is used on the ground, there is very little cooling airflow over the wing. In these conditions, the wing thermalanti-icing system heat output can overheatthe wing leading edges. This can do damage to the temper of the leading edges devices. The precooler system gives maximum cooling to theengine bleed air during ground operationsto prevent overheat damage. 最后引气从预冷器出来后，就可以给飞机的各个系统提供满足压力和温度要求的引气。 以上就是气源系统的基本部件了 而这些引气到底有什么作用呢？ 首先 引气最大的作用就是 给飞机增压和调节温度，当然这是需要经过一套空调系统后才会供给客舱。 The air conditioning systemcontrols the interior environment of the airplane for flight crew,passengers, and equipment. 其二 可以用于启动发动机，启动发动机前先用引气带动发动机转子，为喷油点火前做一个准备。 The engine starting systemuses pneumatic power to turn the engine’s N2 rotorduring a start or motor procedure 第三，可以为大翼和发动机进气整流罩用引气加热，防止结冰。 The WTAI system uses hot airfrom the pneumatic system to heat the three inboardleading edge slats of the wing The inlet cowl thermalanti-ice (TAI) valve controls the flow of air to the engine inlet cowl 第四 可以为液压油箱增压，（液压系统就像人类的肌肉，可以控制飞机的各个舵面，而液压油箱就是储存液压油的地方） 为液压油箱增压的目的就在于 使油更顺畅的进入 液压泵，并且减少气泡的产生损坏液压泵。 The hydraulic reservoir pressurizationsystem supplies pressurizedfiltered bleed air from the airplane’s pneumatic system (left/right enginebleed air, APU bleed air, or external ground air) to the mainhydraulic systems A and B reservoirs. The system provides apositive supply of hydraulic fluid to the pumps, maintains normalreturn pressure in the hydraulic system,and also helps to prevent foaming in the reservoirs. A constant pressure ofapproximately 45-50 psi is normallysuppliedto the reservoirs by the pneumatic system. 第五，也就是最后一点，是为飞机的水系统增压，也是为水箱增压。 The air supply systempressurizes the water tank. 好的 以上就是飞机的引气系统简述。希望大家对飞机的引气系统有了一个初步的认识！ Thank you for reading！ | 
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发表于 2015-3-24 15:46:50
