16.在起动循环开始时，燃气涡轮起动机由它自带的起动机马达带转，直到它达到自持的转速为止，同时起动和点火系统自动关闭。然后继续加速到大约60，000转/分的控制转速。同时，当燃气涡轮起动发动机加速时，排出的燃气经过导向器叶片导入自由动力涡轮，使其带动主发动机。一旦主发动机到达自持转速之后，切断开关工作，将燃气涡轮起动机停机。当起动机停机时，离合器自动脱开输出轴，发动机依靠它自身的功率加速到慢车转速。
液压起动
17．液压起动用于起动某些小型喷气发动机。在多数情况下，使用发动机上安装的一台液压泵，称之为液压泵／起动机，虽然，在其它一些情况下可能使用单独的液压马达。向发动机传递扭矩的方法可以是多种多样的，但是典型的系统是采用一套减速齿轮和离台器组件。带转液压泵／起动机的功率由地面液压设备的液压提供，通过减速齿轮和离合器传递给发动机。起动系统由电路控制。电路也操纵液压活门。当起动循环完成时，使液压泵／起动机起正常的液压泵的作用。
发动机空气起动机
排出空气
外部齿轮箱
空气控制活门
高压空气
点火
18．高能点火被用来起动所有的喷气发动机，而且总是装备双套系统。每一个系统都有一个点火装置与它自己的点火火花塞相连。两个火花塞在燃烧室中处于不同的位置。
19.每一个高能点火装置都接受来自飞机供电系统的低压电，它由起动系统的电路控制。电能被储存在点火装置中，直到达到预定的值，该能量便以高电压、高电流放电形式通过点火火花塞释放出来。
地面起动气源
机体挂架
从已开车的发动机供气
辅助动力装置
（A.P.U.）
Starting and ignition
图11-7 空气起动系统
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.点火装置的能量以焦耳计（一焦耳等于每秒一瓦特）。设计中它们的输出是可以根据要求改变的。为了保证发动机在高空能顺利地再点火，高值输出（例如12焦耳）是必要的。有时为了保证起动也需要
高值输出。无论如何，在某些飞行条件下，如在结冰、或在暴雨或大雪中起飞，会要求点火系统连续工作，以便一旦发生熄火时进行自动再点火。对于这种情况最好选用低值输出（例如3到6焦耳），因为它
会使点火火花塞及点火装置寿命更长。所以，为适应所有发动机工作状态的要求，最好使用能提供高值和低值输出的组合式系统。这种系统应当有一个装置向一个火花塞提供高输出，另一个装置向第二个火花塞提供低输出。然而，有些点火装置能够既提供高输出值，又能提供低输出值，其输出值是按要求事先选定的。
Starting and ignition
涡轮
供气管
单向活门(开)
排气喷嘴
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.
图11-9 一种燃气涡轮起动机
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22.图11-10所示的点火装置为典型的直流断续器控制的装置。一个感应线圈由断续器机构控制，通过高压整流器给储存电容器充电。当电容器中的电压等于封严放电间隙的击穿值时，能量通过点火火花塞的端面释放。点火装置中有一个扼流圈，用来延长放电时间。还装有一个放电电阻器，用于保证系统被关闭之后一分钟之内，使电容器中残存的任何能量被释放掉。点火装置中的安全电阻器是用来使该装置能够安全工作，即使在高压线脱线和绝缘的情况下也能安全工作。
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