Tuesday, March 13, 2012


11. The burner system consists of several circular concentric fuel manifolds supported by struts inside the jet pipe. Fuel is supplied to the manifolds by feed pipes in the support struts and sprayed into the flame area, between the flame stabilizers, from holes in the downstream  edge  of  the  manifolds.  The  flame stabilizers are blunt nosed V-section annular rings  located  downstream  of  the  fuel  burners.  Analternative system includes an additional segmented fuel manifold mounted within the flame stabilizers. The typical burner and flame stabilizer shown in fig. 16-4 is based on the latter system.

Jet pipe
Fig. 16-4 Typical afterburning jet pipe equipment.
12. The afterburning jet pipe is made from a heat- resistant nickel alloy and requires more insulation than the normal jet pipe to prevent the heat of combustion being transferred to the aircraft structure. The jet pipe may be of a double skin construction with the outer skin carrying the flight loads and the inner skin the thermal stresses; a flow of cooling air is often induced between the inner and outer skins. Provision is also made to accommodate expansion and contraction, and to prevent gas leaks at the jet pipe joints.
13. A circular heatshield of similar material to the jet pipe is often fitted to the inner wall of the jet pipe to improve cooling at the rear of the burner section. The heatshield comprises a number of bands, linked by cooling corrugations, to form a single skin. The rear of the heatshield is a series of overlapping 'tiles' riveted to the surrounding skin (fig. 16-4). The shield also prevents combustion instability from creating excessive noise and vibration, which in turn would cause rapid physical deterioration of the afterburner equipment.
Propelling nozzle 
14. The propelling nozzle is of similar material and construction as the jet pipe, to which it is secured as a  separate  assembly.  A two-position  propelling nozzle has two movable eyelids that are operated by actuators, or pneumatic rams, to give an open or closed position (para. 4.). A variable-area propelling nozzle has a ring of interlocking flaps that are hinged to the outer casing and may be enclosed by an outer shroud. The flaps are actuated by powered rams to the closed position, and by gas loads to the interme- diate or the open positions; control of the flap position is by a control unit and a pump provides the power to the rams (para. 18).

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