通風(fēng)／冷卻空氣
15.另一種連續(xù)元件傳感器具有電容的性質(zhì)，它有一根管子，管內(nèi)裝有絕緣材料，并有一導(dǎo)體穿中心而過。電壓差施加在管子和中心導(dǎo)體之間。當(dāng)溫度增加時(shí)，絕緣材料的性能變化，電容值也產(chǎn)生相應(yīng)的變化，這種電容值得變化就作為火警顯示出來。
區(qū)域3空氣出氣口
后防火壁
區(qū)域1空氣出氣口
前防火壁
渦輪機(jī)匣冷卻總管
減壓門
徑向傳動(dòng)整流罩
14.無論是熱敏電阻還是熱電偶探測(cè)器均具有十分適合這種應(yīng)用的特性。熱電偶含有兩種不同的金屬，它們連接在一起形成兩個(gè)接點(diǎn)。當(dāng)兩個(gè)接點(diǎn)間的溫差增大時(shí)，線路中產(chǎn)生一電動(dòng)勢(shì)，這一電動(dòng)勢(shì)觸發(fā)發(fā)火警顯示器。熱敏電阻含有一種半導(dǎo)體材料，這種材料的電阻隨溫度的增加而變化，且使線路中的電流產(chǎn)生相應(yīng)的變化。正是這種電流的變化啟動(dòng)報(bào)警指示器。熱敏電阻可用作一種單點(diǎn)探測(cè)器或一種連續(xù)元件傳感器。
區(qū)域1
空氣進(jìn)口
區(qū)域3進(jìn)氣槽
區(qū)域3進(jìn)氣槽
掛架分流囂整流罩
圖14-2 渦輪風(fēng)扇發(fā)動(dòng)機(jī)的冷卻與通風(fēng)
Fig. 14-2 Cooling and ventilation - turbo-fan engine.
warning displays. The thermistor consists of a semi-temperature increases, with a corresponding change conductor material whose resistance changes as in the current flowing in the circuit. It is this change in
火災(zāi)包容
19.發(fā)動(dòng)機(jī)起火必須要包容在動(dòng)力裝置內(nèi)，不能讓火蔓延至飛機(jī)的其它部分。環(huán)繞發(fā)動(dòng)機(jī)的整流罩通常是由鋁合金制成的，所以當(dāng)飛機(jī)處于靜態(tài)時(shí)，它包不住火。但是在飛行中，整流罩周圍的氣流提供了充分的冷卻空氣，使得它們能防火。不受冷卻氣流影響的防火隔板和整流罩，以及可能起火燒著的某些出口周圍的整流罩段，通常是用鋼或鈦材料制成的。
17.在高馬赫數(shù)下，急劇升高的溫度可能會(huì)使熱敏電阻或熱電偶火災(zāi)探測(cè)系統(tǒng)工作不良。因此探測(cè)器升高或者溫升率探測(cè)器被證明是最適用的。
18.上述各類探測(cè)器的替代物是監(jiān)視探測(cè)器。它們對(duì)起火的光輻射產(chǎn)生感應(yīng)。它們能被制造成敏感度非常之高，以致于僅對(duì)煤油起火輻射出的紫外線和紅外線產(chǎn)生感應(yīng)。
the current that operates the warning indicators. A thermistor may be used as a single point detector or as a continuous element sensor.
15.
Another form of continuous element sensor takes the form of a capacitor consisting of a tube containing a dielectric material with a conductor running through the centre. A voltage difference is applied between the tube and the centre conductor. As the temperature increases then the properties of the dielectric change with a corresponding change in the value of capacitance. This change of capacitance is displayed as a fire warning.
16.
The gas filled detector consists of stainless steel tubing filled with gas absorbent material and in the event of a fire or overheat condition the temperature rise will cause the core of the sensing loop to expel the absorbed active gas into the sealed tube causing a rapid increase in pressure. This build up of pressure is sensed by the detector alarm switch. Should the sensing loop become damaged causing a loss of the pressurized gas, an integrity switch will indicate a detection loop fault on the appropriate engine. Fire indication is given by a warning light and bell.
Fire protection
17.
At high Mach numbers, the considerably higher temperature levels may be such as to render the thermistor or thermocouple fire detection system unsatisfactory. Thermal detectors that sense either a temperature rise, or a rate of temperature rise, may therefore prove most suitable.
18.
Alternatives to the above types are surveillance detectors that respond to light radiation from a fire. These may be made so sensitive that they respond only to the ultra-violet and infra-red rays emitted from a kerosine fire.
FIRE CONTAINMENT
19. An engine fire must be contained within the power plant and not be allowed to spread to other parts of the aircraft. The cowlings that surround the engine are usually made of aluminium alloys, which would be unable to contain a fire when the aircraft is static. During flight, however, the airflow around the cowlings provides sufficient cooling to render them fireproof. Fireproof bulkheads and any cowlings that are not affected by a cooling airflow, and sections of cowlings around certain outlets that may act as 'flame-holders', are usually manufactured from steel or titanium.
圖14-3 一種連續(xù)元件火災(zāi)探測(cè)系統(tǒng)
22.用于撲滅發(fā)動(dòng)機(jī)著火的滅火劑一般是一種氟氯烷(氟利昂)化合物。滅火劑裝在增壓滅火瓶?jī)?nèi)且放置在著火危險(xiǎn)區(qū)之外。當(dāng)人工操作有關(guān)電氣線路時(shí)，滅火劑從滅火瓶經(jīng)過系列多孔噴射管或噴嘴噴射到火上(圖14-4)。噴射必須足以供應(yīng)預(yù)定濃度的滅火劑，持續(xù)時(shí)間0.5秒至2秒。通常這種系統(tǒng)是一個(gè)可單獨(dú)噴灑兩次的滅火系統(tǒng)。
Fire protection
發(fā)動(dòng)機(jī)過熱探測(cè)
23.渦輪過熱不會(huì)構(gòu)成嚴(yán)重的起火危險(xiǎn)。但是，探測(cè)出過熱情況是很重要的，這樣可使駕駛員在出現(xiàn)機(jī)械或材料損害之前將發(fā)動(dòng)機(jī)停車。
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