高压空气
高压中间空气
低压空气
图9-1 内部空气流的简图
Fig. 9-1 General internal airflow pattern.
6．图9-2示出了气冷式高压导向叶片和涡轮叶片的布置，图中示出了冷却空气流向。涡轮导向叶片和涡轮叶片的寿命不仅取决于它们的结构形式，而且还与冷却方法有关，因此内部流道的气流设计很重要。在整个燃气涡轮发展历程中，曾经对涡轮导向叶片和涡轮叶片使用过许多的冷却方法。在一般的情况下，单通道内部(对流)冷却具有很大的实用效果。但是，在研究发展中又实现了多通道的内部冷却涡轮叶片，带外部气膜冷却冲击式冷却导向叶片，这种外部气膜冷却在导向叶片和转子叶片均用，如图9-3和图9-4所示。
Internal air system
图9-2 导向叶片和涡轮叶片的冷却布置图
7．“预旋喷嘴”(图9-2)降低了供往轮盘用于叶片冷却的空气的压力和温度。这些喷嘴还使空气得到很大的周向速度，以帮助空气有效地进入旋转的冷却通道。
8．冷却涡轮盘的冷却空气进入轮盘之间的空腔。并往外流过轮盘的表面。气流由级间封严件控制，在完成冷却功能之后，排入主燃气流(图9-5)，参见第23段热燃气吸入部分。
6.
An air cooled high pressure nozzle guide vane and turbine blade arrangement illustrating the cooling airflow is shown in fig. 9-2. Turbine vane and turbine blade life depends not only on their form but also on the method of cooling, therefore the flow design of the internal passages is important. There have been numerous methods of turbine vane and turbine blade cooling which have been used throughout the history of gas turbines. Generally, single pass internal (convection) cooling was of great practical benefit but development has lead to multi-pass internal cooling of blades, impingement cooling of vanes with external air film cooling of both vanes and blades, these are shown in fig. 9-3. and fig. 9-4.
7.
The 'pre-swirl nozzles' (fig. 9-2) reduce the temperature and pressure of the cooling air fed to the disc for blade cooling. The nozzles also impart a
Internal air system
substantial whirl velocity to assist efficient entry of the air into the rotating cooling passages.
8. Cooling air for the turbine discs enters the annular spaces between the discs and flows outwards over the disc faces. Flow is controlled by interstage seals and, on completion of the cooling function, the air is expelled into the main gas stream (fig. 9-5); see para. 23., Hot gas ingestion.
Bearing chamber cooling
9. Air cooling of the engine bearing chambers is not normally necessary since the lubrication system (Part 8) is adequate for cooling purposes. Additionally, bearing chambers are located, where possible, in the cooler regions of the engine. In instances where additional cooling is required, it is good practice to have a double skinned bearing housing with cooling air fed into the intermediate space.
图9-3 高压涡轮叶片冷却的发展
附件冷却
10．发动机的一些附件会产生大量的热，其中发电机即是一例。这些附件常常需要有它们自己的冷却通路。当用空气进行冷却时，气源可以是压气机，或者是从发动机整流罩中进气道的引气口处引入的外界空气。
Internal air system
11．当一个附件装置在飞行中由外界空气冷却的时候，通常需要配备一条诱导通路，以便在地面静态运转没有外部空气流的时候使用。这是将压气机输出的空气流经位于附件冷却空气出口导管处的几个喷口而实现的。流经这些喷口的空气速度造成一个低压区，这个低压区形成了一个引射器，由此来引射一股大气空气流流经进气道中的引气口。为了保证该引射器系统仅仅在地面工作，来自压气机的空气流由一个活门控制。带引射器的发电机冷却系统示于图9-6。
封严
12．封严件用于防止滑油从发动机轴承腔漏出，控制冷却空气流和防止主气流的燃气进入涡轮盘空腔。
冲击冷却管
图9-4 高压涡轮导向叶片的结构和冷却
Fig. 9-4 High pressure nozzle guide vane construction and cooling.
13．在燃气涡轮发动机上使用了多种封严方法。选择何种方法取决于周围的温度和压力、可磨蚀性、发热量、重量、可用的空间，易于制造及易于安装和拆卸。下列各段叙述了某些封严方法。图9-5所示为一台假想的涡轮，用来表明这些封严的使用方法。
Accessory cooling
10.
A considerable amount of heat is produced by some of the engine accessories, of which the electrical generator is an example, and these may often require their own cooling circuit. When air is used for cooling, the source may be the compressor or atmospheric air ducted from intake louvres in the engine cowlings.
11.
When an accessory unit is cooled during flight by atmospheric air it is usually necessary to provide an induced circuit for use during static ground running when there would be no external airflow. This is achieved by allowing compressor delivery air to pass through nozzles situated in the cooling air outlet duct of the accessory. The air velocity through the nozzles create a low pressure area which forms an ejector, so inducing a flow of atmospheric air through the intake louvres. To ensure that the ejector system only operates during ground running, the flow of air from the compressor is controlled by a valve. A generator cooling system with an ejector is shown in fig. 9-6.
SEALING
12. Seals are used to prevent oil leakage from the engine bearing chambers, to control cooling airflows and to prevent ingress of the mainstream gas into the turbine disc cavities.
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