16.在起動循環開始時，燃氣渦輪起動機由它自帶的起動機馬達帶轉，直到它達到自持的轉速為止，同時起動和點火系統自動關閉。然后繼續加速到大約60，000轉/分的控制轉速。同時，當燃氣渦輪起動發動機加速時，排出的燃氣經過導向器葉片導入自由動力渦輪，使其帶動主發動機。一旦主發動機到達自持轉速之后，切斷開關工作，將燃氣渦輪起動機停機。當起動機停機時，離合器自動脫開輸出軸，發動機依靠它自身的功率加速到慢車轉速。
液壓起動
17．液壓起動用于起動某些小型噴氣發動機。在多數情況下，使用發動機上安裝的一臺液壓泵，稱之為液壓泵／起動機，雖然，在其它一些情況下可能使用單獨的液壓馬達。向發動機傳遞扭矩的方法可以是多種多樣的，但是典型的系統是采用一套減速齒輪和離臺器組件。帶轉液壓泵／起動機的功率由地面液壓設備的液壓提供，通過減速齒輪和離合器傳遞給發動機。起動系統由電路控制。電路也操縱液壓活門。當起動循環完成時，使液壓泵／起動機起正常的液壓泵的作用。
發動機空氣起動機
排出空氣
外部齒輪箱
空氣控制活門
高壓空氣
點火
18．高能點火被用來起動所有的噴氣發動機，而且總是裝備雙套系統。每一個系統都有一個點火裝置與它自己的點火火花塞相連。兩個火花塞在燃燒室中處于不同的位置。
19.每一個高能點火裝置都接受來自飛機供電系統的低壓電，它由起動系統的電路控制。電能被儲存在點火裝置中，直到達到預定的值，該能量便以高電壓、高電流放電形式通過點火火花塞釋放出來。
地面起動氣源
機體掛架
從已開車的發動機供氣
輔助動力裝置
（A.P.U.）
Starting and ignition
圖11-7 空氣起動系統
Fig. 11-7 An air starting system.
operates and shuts down the gas turbine starter. As the starter runs down, the clutch automatically disengages from the output shaft and the main engine accelerates up to idling r.p.m. under its own power.
Hydraulic
17. Hydraulic starting is used for starling some small jet engines. In most applications, one of the engine-mounted hydraulic pumps is utilized and is known as a pump/starter, although other applications may use a separate hydraulic motor. Methods of transmitting the torque to the engine may vary, but a typical system would include a reduction gear and clutch assembly. Power to rotate the pump/starter is provided by hydraulic pressure from a ground supply unit and is transmitted to the engine through the reduction gear and clutch. The starting system is controlled by an electrical circuit that also operates hydraulic valves so that on completion of the starting cycle the pump /starter functions as a normal hydraulic pump.
IGNITION
18.
High-energy (H.E.) ignition is used for starting all jet engines and a dual system is always fitted. Each system has an ignition unit connected to its own igniter plug, the two plugs being situated in different positions in the combustion system.
19.
Each H.E. ignition unit receives a low voltage supply, controlled by the starting system electrical circuit, from the aircraft electrical system. The electrical energy is stored in the unit until, at a pre-determined value, the energy is dissipated as a high voltage, high amperage discharge across the igniter plug.
20.
Ignition units are rated in 'joules' (one joule equals one watt per second). They are designed to
20.點火裝置的能量以焦耳計（一焦耳等于每秒一瓦特）。設計中它們的輸出是可以根據要求改變的。為了保證發動機在高空能順利地再點火，高值輸出（例如12焦耳）是必要的。有時為了保證起動也需要
高值輸出。無論如何，在某些飛行條件下，如在結冰、或在暴雨或大雪中起飛，會要求點火系統連續工作，以便一旦發生熄火時進行自動再點火。對于這種情況最好選用低值輸出（例如3到6焦耳），因為它
會使點火火花塞及點火裝置壽命更長。所以，為適應所有發動機工作狀態的要求，最好使用能提供高值和低值輸出的組合式系統。這種系統應當有一個裝置向一個火花塞提供高輸出，另一個裝置向第二個火花塞提供低輸出。然而，有些點火裝置能夠既提供高輸出值，又能提供低輸出值，其輸出值是按要求事先選定的。
Starting and ignition
渦輪
供氣管
單向活門(開)
排氣噴嘴
give outputs which may vary according to require-ments. A high value output (e.g. twelve joule) is necessary to ensure that the engine will obtain a sat-isfactory relight at high altitudes and is sometimes necessary for starting. However, under certain flight conditions, such as icing or take-off in heavy rain or snow, it may be necessary to have the ignition system continuously operating to give an automatic relight should flame extinction occur. For this condition, a low value output (e.g. three to six joule) is preferred because it results in a longer life of the igniter plug and ignition unit. Consequently, to suit all engine operating conditions, a combined system giving a high and low value output is favoured. Such a system would consist of one unit emitting a high output to one igniter plug, and a second unit giving a low output to a second igniter plug. However, some ignition units are capable o! supplying both high and low outputs, the value being pre-selected as required.
圖11-9 一種燃氣渦輪起動機
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22.圖11-10所示的點火裝置為典型的直流斷續器控制的裝置。一個感應線圈由斷續器機構控制，通過高壓整流器給儲存電容器充電。當電容器中的電壓等于封嚴放電間隙的擊穿值時，能量通過點火火花塞的端面釋放。點火裝置中有一個扼流圈，用來延長放電時間。還裝有一個放電電阻器，用于保證系統被關閉之后一分鐘之內，使電容器中殘存的任何能量被釋放掉。點火裝置中的安全電阻器是用來使該裝置能夠安全工作，即使在高壓線脫線和絕緣的情況下也能安全工作。
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