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•        Sealing密封

•        Cavity腔体

•        Commensurate相称的

•        Vent 通风口

•        Detrimental有害的

•        Integrity完整

•        Arrangement安排

•        Numerous众多

•        Convection对流

•        Multi-pass多通道

•        Impingementcooling 冲击式冷却

•        Filmcooling 气膜冷却

•        Pre-swirlnozzles 预旋喷嘴

•        Substantial大量的

•        Lubrication  润滑

•        Doubleskinned 双层壁面

•        Bearinghousing 轴承座

•        Electricalgenerator 发电机

•        Circuit电路

•        Louvre百叶窗

•        Cowling整流罩

•        Wearability耐磨性

•        Manufacture制造

•        Installation安装

•        Removal拆卸

•        Labyrinthseal 篦齿封严

•        Retain保留

•        Fin 翅片

•        Bore 孔

•        Abradable耐磨的

•        Positive肯定的、积极的、优点

•        Simultaneously同时

•        Ringseal 环形封严

•        Groove沟槽

•        Degradation退化

•        Seizure发作、扣押、卡住

•        Hydraulicseal 液压封严

•        Traverse横穿

•        Immerse沉浸

•        Carbonseal 石墨封严

•        Collar套环、圈

•        Spring弹簧

•        Brushseal 刷式封严

•        Bristle刷毛

•        Ceramiccoating 陶瓷涂层

•        Rim 轮缘

•        Inward向内

•        Quantity数量

•        Oppose反对

•        Tension拉伸

•        Locationbearing 定位轴承

•        Cabin 客舱

•        Airframe机身

读Sentence

•        2. Anincreasing amount of work is done on the air, as it progresses through thecompressor, to raise its pressure and temperature. Therefore, to reduce engineperformance losses, the air is taken as early as possible from the compressorcommensurate with the requirement of each particular function. The cooling airis expelled overboard via a vent system or into the engine main gas stream, atthe highest possible pressure, where a small performance recovery is achieved.

•        4.Cooling air is used to control the temperature of the compressor shafts anddiscs by either cooling or heating them. This ensures an even temperaturedistribution and therefore improves engine efficiency by controlling thermalgrowth and thus maintaining minimum blade tip and seal clearances. Typicalcooling and sealing airflows are shown in fig. 9-1.

•        6. Anair cooled high pressure nozzle guide vane and turbine blade arrangementillustrating the cooling airflow is shown in fig. 9-2. Turbine vane and turbineblade 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 havebeen numerous methods of turbine vane and turbine blade cooling which have beenused throughout the history of gas turbines. Generally, single pass internal(convection) cooling was of great practical benefit but development has lead tomulti-pass internal cooling of blades, impingement cooling of vanes withexternal air film cooling of both vanes and blades, these are shown in fig.9-3. and fig. 9-4.

•        13.Various sealing methods are used on gas turbine engines. The choice of whichmethod is dependent upon the surrounding temperature and pressure, wearability,heat generation, weight, space available, ease of manufacture and ease ofinstallation and removal. Some of the sealing methods are described in thefollowing paragraphs. A hypothetical turbine showing the usage of these sealsis shown in fig. 9-5.

•        16.Seals between two rotating shafts are more likely to be subject to rubs betweenthe fins and abradable material due to the two shafts deflectingsimultaneously. This will create excessive heat which may result in shaftfailure. To prevent this, a non-heat producing seal is used where the abradablelining is replaced by a rotating annulus of oil. When the shafts deflect, thefins enter the oil and maintain the seal without generating heat (fig. 9-7).

•        23. Itis important to prevent the ingestion of hot mainstream gas into the turbinedisc cavities as this would cause overheating and result in unwanted thermalexpansion and fatigue. The pressure in the turbine annulus forces the hot gas,between the rotating discs and the adjacent static parts, into the turbine discrim spaces. In addition, air near the face of the rotating discs is acceleratedby friction causing it to be pumped outwards. This induces a complementaryinward flow of hot gas.

•        25.Engine shafts experience varying axial gas loads (Part 20) which act in aforward direction on the compressor and in a rearward direction on the turbine.The shaft between them is therefore always under tension and the differencebetween the loads is carried by the location bearing which is fixed in a staticcasing (fig. 9-8). The internal air pressure acts upon a fixed diameterpressure balance seal to ensure the location bearing is adequately loadedthroughout the engine thrust range.

•        26. Toprovide cabin pressurization, airframe anti- icing and cabin heat, substantialquantities of air are bled from the compressor. It is desirable to bleed theair as early as possible from the compressor to minimize the effect on engineperformance. However, during some phases of the flight cycle it may benecessary to switch the bleed source to a later compressor stage to maintainadequate pressure and temperature.

读全文并回答以下问题：

•       Whatis the function of the internal air system?

•       Whatare the advantages of pre-swirl nozzle?

•       Whatare the functions of the seals?

•       How toachieve the seals between two rotating shafts?

•       How toprevent the hot gas ingestion?

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