通風／冷卻空氣
15.另一種連續元件傳感器具有電容的性質，它有一根管子，管內裝有絕緣材料，并有一導體穿中心而過。電壓差施加在管子和中心導體之間。當溫度增加時，絕緣材料的性能變化，電容值也產生相應的變化，這種電容值得變化就作為火警顯示出來。
區域3空氣出氣口
后防火壁
區域1空氣出氣口
前防火壁
渦輪機匣冷卻總管
減壓門
徑向傳動整流罩
14.無論是熱敏電阻還是熱電偶探測器均具有十分適合這種應用的特性。熱電偶含有兩種不同的金屬，它們連接在一起形成兩個接點。當兩個接點間的溫差增大時，線路中產生一電動勢，這一電動勢觸發發火警顯示器。熱敏電阻含有一種半導體材料，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生相應的變化。正是這種電流的變化啟動報警指示器。熱敏電阻可用作一種單點探測器或一種連續元件傳感器。
區域1
空氣進口
區域3進氣槽
區域3進氣槽
掛架分流囂整流罩
圖14-2 渦輪風扇發動機的冷卻與通風
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
火災包容
19.發動機起火必須要包容在動力裝置內，不能讓火蔓延至飛機的其它部分。環繞發動機的整流罩通常是由鋁合金制成的，所以當飛機處于靜態時，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.在高馬赫數下，急劇升高的溫度可能會使熱敏電阻或熱電偶火災探測系統工作不良。因此探測器升高或者溫升率探測器被證明是最適用的。
18.上述各類探測器的替代物是監視探測器。它們對起火的光輻射產生感應。它們能被制造成敏感度非常之高，以致于僅對煤油起火輻射出的紫外線和紅外線產生感應。
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 一種連續元件火災探測系統
22.用于撲滅發動機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內且放置在著火危險區之外。當人工操作有關電氣線路時，滅火劑從滅火瓶經過系列多孔噴射管或噴嘴噴射到火上(圖14-4)。噴射必須足以供應預定濃度的滅火劑，持續時間0.5秒至2秒。通常這種系統是一個可單獨噴灑兩次的滅火系統。
Fire protection
發動機過熱探測
23.渦輪過熱不會構成嚴重的起火危險。但是，探測出過熱情況是很重要的，這樣可使駕駛員在出現機械或材料損害之前將發動機停車。
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