15.
A labyrinth seal comprises a finned rotating member with a static bore which is lined with a soft abradable material, or a high temperature honeycomb structure. On initial running of the engine the fins lightly rub against the lining, cutting into it to give a minimum clearance. The clearance varies throughout the flight cycle, dependent upon the thermal growth of the parts and the natural flexing of the rotating members. Across each seal fin there is a pressure drop which results in a restricted flow of
篦齿式封严件
14．这种封严件广泛用来挡住轴承腔中的滑油，它还用作控制内部空气流的限流装置。几种篦齿式封严设计示于图9-7。
Internal air system
15．篦齿式封严件包括一个带篦齿的旋转件和一个静止的座孔，座孔嵌衬有一层软的可磨材料衬带，或装上一个耐高温的蜂窝结构。在发动机开始运转时，封严齿轻轻地摩擦并切入这个衬带，使它们之间的间隙成为最小。由于零件的热膨胀(伸长)和旋转件的自然挠曲，在整个飞行循环中间隙是在变化的。每个封严篦齿的前后存在一定的压力降，使得封严空气从封严篦齿的一侧流到另一侧受到限制。当这种封严件用于轴承腔封严时，它只允许空气从轴承腔的外侧流入内侧，从而防止了滑油泄漏。这个气流还可诱发正压力，它有助于滑油回油系统。
低压空气
高压空气
16．两根旋转轴之间的封严件，由于两根轴同时发生弯曲，所以更易导致篦齿与摩擦材料之间的摩擦。这会产生过量的热，使轴损坏。为了防止这一点，使用了一种不产生热的封严件，这种封严件中的可磨蚀衬带由旋转中的滑油环带来取代。当轴弯曲时，篦齿浸入滑油并保持封严件不产生热(图9-7中左侧第1图)。
级间蜂窝封严件
涡轮轴
涡轮盘
浮动环
封严件
涡轮盘
低压冷却空气
涡轮盘
极间篦齿式封严件
液压封严件
高压冷却空气
涡轮叶片
导向器时片
高压冷却空气进入燃气流
刷式
封严件
预旋喷嘴
低压空气
排出机外
图9-5 一种假设的涡轮冷却和封严的安排
Fig. 9-5 A hypothetical turbine cooling and sealing arrangement.
环形(又称浮动环)封严件
17．环形封严件(图9-7中右侧第2图)有一个金属环，它安置在静止机匣紧密结合的槽中。该环和旋转轴之间的正常运转间隙比篦齿式封严件所能达到的间隙为小。这是因为无论何时，当轴接触这个环的时候，环可以在其所在的机匣内移动。
18．环形封严件用于轴承腔的封严，但是高温区除外，由于高温会使滑油结焦，导致环形件卡在机匣中。
液压封严件
19．这种封严方法常常应用于两个旋转件之间来封严轴承腔。与篦齿式或环形封严件不同之处在于它不允许受控的空气流穿过封严件。
20．液压封严件(图9-7中左侧第3图)由一个封严齿浸在一个滑油环带中形成，这个滑油环带是由离心力造成的。轴承腔内外的任何空气压差由齿两
侧的滑油油面差补偿。
Internal air system
发电机
图9-6 一种发电机冷却系统
Fig. 9-6 A generator cooling system.
sealing air from one side of the seal to the other. When this seal is used for bearing chamber sealing, it prevents oil leakage by allowing the air to flow from the outside to the inside of the chamber. This flow also induces a positive pressure which assists the oil return system.
16. Seals between two rotating shafts are more likely to be subject to rubs between the fins and abradable material due to the two shafts deflecting simultaneously. This will create excessive heat which may result in shaft failure. To prevent this, a non-heat producing seal is used where the abradable lining is replaced by a rotating annulus of oil. When the shafts deflect, the fins enter the oil and maintain the seal without generating heat (fig. 9-7).
Ring seals
17. A ring seal (fig. 9-7) comprises a metal ring which is housed in a close fitting groove in the static housing. The normal running clearance between the ring and rotating shaft is smaller than that which can be obtained with the labyrinth seal. This is because the ring is allowed to move in its housing whenever the shaft comes into contact with it. 石墨封严件
21．石墨封严件(图9-7中右侧第3图)含有一个静止的石墨环构件，它不断地与旋转轴的套环相摩擦。使用了几个弹簧，使石墨与套环保持接触。这种类型的封严件全依靠接触的良好程度，它不允许任何滑油或空气漏过。因摩擦造成的热由滑油系统
带走。
18. Ring seals are used for bearing chamber sealing, except in the hot areas where oil degradation due to heat would lead to ring seizure within its housing.
出口导管
引射器
来自进气道放气口
从压气机
放出的空气
压力控制活门
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：劳斯莱斯喷气引擎－中英(43)
