高壓空氣
高壓中間空氣
低壓空氣
圖9-1 內部空氣流的簡圖
Fig. 9-1 General internal airflow pattern.
6．圖9-2示出了氣冷式高壓導向葉片和渦輪葉片的布置，圖中示出了冷卻空氣流向。渦輪導向葉片和渦輪葉片的壽命不僅取決于它們的結構形式，而且還與冷卻方法有關，因此內部流道的氣流設計很重要。在整個燃氣渦輪發展歷程中，曾經對渦輪導向葉片和渦輪葉片使用過許多的冷卻方法。在一般的情況下，單通道內部(對流)冷卻具有很大的實用效果。但是，在研究發展中又實現了多通道的內部冷卻渦輪葉片，帶外部氣膜冷卻沖擊式冷卻導向葉片，這種外部氣膜冷卻在導向葉片和轉子葉片均用，如圖9-3和圖9-4所示。
Internal air system
圖9-2 導向葉片和渦輪葉片的冷卻布置圖
7．“預旋噴嘴”(圖9-2)降低了供往輪盤用于葉片冷卻的空氣的壓力和溫度。這些噴嘴還使空氣得到很大的周向速度，以幫助空氣有效地進入旋轉的冷卻通道。
8．冷卻渦輪盤的冷卻空氣進入輪盤之間的空腔。并往外流過輪盤的表面。氣流由級間封嚴件控制，在完成冷卻功能之后，排入主燃氣流(圖9-5)，參見第23段熱燃氣吸入部分。
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.
圖9-3 高壓渦輪葉片冷卻的發展
附件冷卻
10．發動機的一些附件會產生大量的熱，其中發電機即是一例。這些附件常常需要有它們自己的冷卻通路。當用空氣進行冷卻時，氣源可以是壓氣機，或者是從發動機整流罩中進氣道的引氣口處引入的外界空氣。
Internal air system
11．當一個附件裝置在飛行中由外界空氣冷卻的時候，通常需要配備一條誘導通路，以便在地面靜態運轉沒有外部空氣流的時候使用。這是將壓氣機輸出的空氣流經位于附件冷卻空氣出口導管處的幾個噴口而實現的。流經這些噴口的空氣速度造成一個低壓區，這個低壓區形成了一個引射器，由此來引射一股大氣空氣流流經進氣道中的引氣口。為了保證該引射器系統僅僅在地面工作，來自壓氣機的空氣流由一個活門控制。帶引射器的發電機冷卻系統示于圖9-6。
封嚴
12．封嚴件用于防止滑油從發動機軸承腔漏出，控制冷卻空氣流和防止主氣流的燃氣進入渦輪盤空腔。
沖擊冷卻管
圖9-4 高壓渦輪導向葉片的結構和冷卻
Fig. 9-4 High pressure nozzle guide vane construction and cooling.
13．在燃氣渦輪發動機上使用了多種封嚴方法。選擇何種方法取決于周圍的溫度和壓力、可磨蝕性、發熱量、重量、可用的空間，易于制造及易于安裝和拆卸。下列各段敘述了某些封嚴方法。圖9-5所示為一臺假想的渦輪，用來表明這些封嚴的使用方法。
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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