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
篦齒式封嚴件
14．這種封嚴件廣泛用來擋住軸承腔中的滑油，它還用作控制內部空氣流的限流裝置。幾種篦齒式封嚴設計示于圖9-7。
Internal air system
15．篦齒式封嚴件包括一個帶篦齒的旋轉件和一個靜止的座孔，座孔嵌襯有一層軟的可磨材料襯帶，或裝上一個耐高溫的蜂窩結構。在發動機開始運轉時，封嚴齒輕輕地摩擦并切入這個襯帶，使它們之間的間隙成為最小。由于零件的熱膨脹(伸長)和旋轉件的自然撓曲，在整個飛行循環中間隙是在變化的。每個封嚴篦齒的前后存在一定的壓力降，使得封嚴空氣從封嚴篦齒的一側流到另一側受到限制。當這種封嚴件用于軸承腔封嚴時，它只允許空氣從軸承腔的外側流入內側，從而防止了滑油泄漏。這個氣流還可誘發正壓力，它有助于滑油回油系統。
低壓空氣
高壓空氣
16．兩根旋轉軸之間的封嚴件，由于兩根軸同時發生彎曲，所以更易導致篦齒與摩擦材料之間的摩擦。這會產生過量的熱，使軸損壞。為了防止這一點，使用了一種不產生熱的封嚴件，這種封嚴件中的可磨蝕襯帶由旋轉中的滑油環帶來取代。當軸彎曲時，篦齒浸入滑油并保持封嚴件不產生熱(圖9-7中左側第1圖)。
級間蜂窩封嚴件
渦輪軸
渦輪盤
浮動環
封嚴件
渦輪盤
低壓冷卻空氣
渦輪盤
極間篦齒式封嚴件
液壓封嚴件
高壓冷卻空氣
渦輪葉片
導向器時片
高壓冷卻空氣進入燃氣流
刷式
封嚴件
預旋噴嘴
低壓空氣
排出機外
圖9-5 一種假設的渦輪冷卻和封嚴的安排
Fig. 9-5 A hypothetical turbine cooling and sealing arrangement.
環形(又稱浮動環)封嚴件
17．環形封嚴件(圖9-7中右側第2圖)有一個金屬環，它安置在靜止機匣緊密結合的槽中。該環和旋轉軸之間的正常運轉間隙比篦齒式封嚴件所能達到的間隙為小。這是因為無論何時，當軸接觸這個環的時候，環可以在其所在的機匣內移動。
18．環形封嚴件用于軸承腔的封嚴，但是高溫區除外，由于高溫會使滑油結焦，導致環形件卡在機匣中。
液壓封嚴件
19．這種封嚴方法常常應用于兩個旋轉件之間來封嚴軸承腔。與篦齒式或環形封嚴件不同之處在于它不允許受控的空氣流穿過封嚴件。
20．液壓封嚴件(圖9-7中左側第3圖)由一個封嚴齒浸在一個滑油環帶中形成，這個滑油環帶是由離心力造成的。軸承腔內外的任何空氣壓差由齒兩
側的滑油油面差補償。
Internal air system
發電機
圖9-6 一種發電機冷卻系統
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. 石墨封嚴件
21．石墨封嚴件(圖9-7中右側第3圖)含有一個靜止的石墨環構件，它不斷地與旋轉軸的套環相摩擦。使用了幾個彈簧，使石墨與套環保持接觸。這種類型的封嚴件全依靠接觸的良好程度，它不允許任何滑油或空氣漏過。因摩擦造成的熱由滑油系統
帶走。
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.
出口導管
引射器
來自進氣道放氣口
從壓氣機
放出的空氣
壓力控制活門
中國航空網 www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：勞斯萊斯噴氣引擎－中英(43)
