12.戽斗式盾牌系統(tǒng)為液壓傳動系統(tǒng)，利用戽斗式門將熱燃氣流反向。推力反向裝置門通過常規(guī)推桿系統(tǒng)來傳動。一個液壓作動筒與一個傳動中介輪相連接，通過一對推桿來操縱門（每個門上有一根推桿）。
11. The clamshell doors are operated by pneumatic rams through levers that give the maximum load to the doors in the forward thrust position; this ensures effective sealing at the door edges, so preventing gas leakage. The door bearings and operating linkage operate without lubrication at temperatures of up to 600 deg. C.
Bucket target system
12.
The bucket target system is hydraulically actuated and uses bucket-type doors to reverse the hot gas stream. The thrust reverser doors are actuated by means of a conventional pushrod system. A single hydraulic powered actuator is connected to a drive idler, actuating the doors through a pair of pushrods (one for each door).
13.
The reverser doors are kept in synchronization through the drive idler. The hydraulic actuator incor-porates a mechanical lock in the stowed (actuator extended) position.
14.
In the forward thrust mode (stowed) the thrust reverser doors form the convergent-divergent final nozzle for the engine.
Thrust reversal
Cold stream reverser system
15.
The cold stream reverser system (fig. 15-4) can be actuated by an air motor, the output of which is converted to mechanical movement by a series of flexible drives, gearboxes and screwjacks, or by a system incorporating hydraulic rams.
16.
When the engine is operating in forward thrust, the cold stream final nozzle is 'open' because the cascade vanes are internally covered by the blocker doors (flaps) and externally by the movable (translating) cowl; the latter item also serves to reduce drag.
17.
On selection of reverse thrust, the actuation system moves the translating cowl rearwards and at the same time folds the blocker doors to blank off the cold stream final nozzle, thus diverting the airflow through the cascade vanes.
Turbo-propeller reverse pitch system
18. As mentioned in para. A, reverse thrust action is affected on turbo-propeller powered aircraft by changing the pitch of the propeller blades through a hydro-mechanical pitch control system (fig. 15-5). Movement of the throttle or power control lever 油門桿
圖15-5 一種螺旋槳槳距控制系統(tǒng)
Fig. 15-5 A propeller pitch control system.
渦輪螺槳反槳系統(tǒng)
正如第4段所述，通過液壓機械式槳葉角度控制系統(tǒng)(圖15-5)來改變螺旋槳槳葉的角度產(chǎn)生反推力對以渦輪螺槳為動力的飛機產(chǎn)生影響。油門桿即功率控制桿把滑油從控制系統(tǒng)引導致螺旋槳機構，將槳葉角度減少到零，,再到負(反)槳距。油門桿移動時，通過與槳葉角度控制裝置相連接的油門桿活門來調(diào)整向發(fā)動機的燃油供給，使發(fā)動機功率和槳葉角度相協(xié)調(diào)，以獲得所學的反推力值。反推力也可用以操縱已停下的渦輪螺槳飛機使之后退。
Thrust reversal
19.在螺旋槳控制系統(tǒng)中已考慮到若干在螺旋槳出現(xiàn)故障時有用的安全因素，這些裝置通常是液壓機械式槳距鎖定裝置或止動裝置。
圖15-6 熱氣流推力反向裝置
Fig. 15-6 Hot stream thrust reverser installations.
結構和材料
20.第9和第12段中介紹的哈殼形門和戽斗式盾牌門（圖15-6）形成噴管的一部分。反推器的機匣與飛機機構連接或直接與發(fā)動機連接。此機匣支撐著兩個反推器的門和操縱機構，在哈殼形門系統(tǒng)中，還支持裝有葉柵葉片的排氣管。燃氣流的角度和面積是通過每一排氣管中的葉片數(shù)量來控制的。
directs oil from the control system to the propeller mechanism to reduce the blade angle to zero, and then through to negative (reverse) pitch. During throttle lever movement, the fuel to the engine is trimmed by the throttle valve, which is interconnect-ed to the pitch control unit, so that engine power and blade angle are co-ordinated to obtain the desired amount of reverse thrust. Reverse thrust action may also be used to manoeuvre a turbo-propeller aircraft backwards after it has been brought to rest.
19. Several safety factors are incorporated in the propeller control system for use in the event of propeller malfunction, and these devices are usually hydro-mechanical pitch locking devices or stops.
CONSTRUCTION AND MATERIALS
20. The clamshell and bucket target doors (fig. 15-6) described in paras. 9 and 12 form part of the jet
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