9.空氣起動應用于大多數民用和若干軍用噴氣發動機中。與其它起動系統相比，它有重量較輕，簡單而且使用經濟等許多優點。
10.空氣起動機馬達將功率通過減速齒輪和離合器傳遞給起動機輸出軸，該軸與發動機相連。典型的空氣起動馬達示于圖11-6。
11.
The starter turbine is rotated by air taken from an external ground supply, an auxiliary power unit (A.P.U.) or as a cross-feed from a running engine. The air supply to the starter is controlled by an elec-trically operated control and pressure reducing valve that is opened when an engine start is selected and is automatically closed at a predetermined starter speed. The clutch also automatically disengages as the engine accelerates up to idling r.p.m. and the
11.起動機渦輪由來自外部地面氣源的空氣帶轉，也可以用輔助動力裝置（APU）帶轉，或者用正在運轉的發動機進行交叉供氣驅動。向起動機供氣的外部氣源由電控制器和減壓活門加以控制。該活門在起動機起動時打開，當達到預定的起動機轉速時自動關閉。當發動機加速到慢車轉速時，離合器自動打開，同時起動停止轉動。一種典型的空氣起動系統示于圖11-7。
高壓開關
排氣管
轉速控制開關
電嘴
點火開關
起動機馬達
點火器
燃油旁路
燃油和空氣回油泵
控制盒
旁路空氣
燃油箱
起動機按鈕
飛機電源
Starting and ignition
圖11-5 一種異丙基硝酸酯起動系統
Fig. 11-5 An iso-propyl-nitrate starting system.
12.有時在已裝有空氣起動機的發動機上還有燃燒室起動機，當沒有外部空氣源的情況下用于向起動機供氣。這種起動機有一個小型的燃燒室，它使用飛機丄佩帶的氣瓶的高壓空氣，及發動機燃油系統的燃油控制活門調節氣源的供氣，氣源對燃油蓄壓器加壓，以提供足夠的燃油壓力進行霧化，而且還激發連續點火系統。燃油、空氣混合氣在燃燒室中點燃，產生的燃氣被引入空氣起動機的渦輪。當起動循環完成之后，有一個電路將氣源斷開，并進而終止燃油和點火系統的工作。
渦輪轉子
減速齒輪
空氣進口
離合器
13.有些渦輪噴氣發動機上不裝起動機馬達，但利用空氣沖擊渦輪葉片作為帶轉發動機的一種方法。空氣可以取自外部氣源、或正在運轉的發動機，并經單向活門和導向器導入渦輪葉片。一種空氣沖擊起動的典型方法示于圖11-8。
發動機驅動軸
空氣出口
Starting and ignition
燃氣渦輪起動
14.燃氣渦輪起動機用于某些噴氣發動機中，這種起動方式是完全自立的。它具有自己的燃油和點火系統、起動系統（通常是電的或液壓的），以及自備滑油系統。這種起動機使用經濟，而且以比較輕的重量提供高的功率輸出。
15.這種起動機含有一臺小而緊湊的燃氣渦輪發動機，其一般特點是采用渦輪驅動的離心壓氣機，回油式燃燒系統和一個機械上獨立的自由動力渦輪。它由動力渦輪經由兩級游星式減速齒輪、自動離合器和輸出軸與主發動機相連。一種典型的燃氣渦輪起動機示于圖11-9。
圖11-6 一種空氣起動機馬達
Fig. 11-6 An air starter motor.
rotation of the starter ceases. A typical air starting system is shown in fig. 11-7.
12.
A combustor starter is sometimes fitted to an engine incorporating an air starter and is used to supply power to the starter when an external supply of air is not available. The starter unit has a small combustion chamber into which high pressure air, from an aircraft-mounted storage bottle, and fuel, from the engine fuel system, are introduced. Control valves regulate the air supply which pressurizes a fuel accumulator to give sufficient fuel pressure for atomization and also activates the continuous ignition system. The fuel/air mixture is ignited in the combustion chamber and the resultant gas is directed onto the turbine of the air starter. An electrical circuit is provided to shut off the air supply which in turn terminates the fuel and ignition systems on completion of the starting cycle.
13.
Some turbo-jet engines are not fitted with starter motors, but use air impingement onto the turbine blades as a means of rotating the engine. The air is obtained from an external source, or from an engine that is running, and is directed through non-return valves and nozzles onto the turbine blades. A typical method of air impingement starting is shown in fig. 11-8.
Gas turbine
14.
A gas turbine starter is used for some jet engines and is completely self-contained. It has its own fuel and ignition system, starting system (usually electric or hydraulic) and self-contained oil system. This type of starter is economical to operate and provides a high power output for a comparatively low weight.
15.
The starter consists of a small, compact gas turbine engine, usually featuring a turbine-driven centrifugal compressor, a reverse flow combustion system and a mechanically independent |free-power turbine. The free-power turbine is connected to the main engine via a two-stage epicyclic reduction gear, automatic clutch and output shaft. A typical gas turbine starter is shown in fig. 11-9.
16.
On initiation of the starting cycle, the gas turbine starter is rotated by its own starter motor until it reaches self-sustaining speed, when the starting and ignition systems are automatically switched off. Acceleration then continues up to a controlled speed of approximately 60,000 r.p.m. At the same time as the gas turbine starter engine is accelerating, the exhaust gas is being directed, via nozzle guide vanes, onto the free-power turbine to provide the drive to the main engine. Once the main engine reaches self-sustaining speed, a cut-out switch
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