Supercritical operation GTD

If the area of ​​Fr will be chosen less than optimal, the throat will be an additional closing compression shock.

Usually a point of agreement for TWA external compression to choose a shallow branch near a corner point throttle characteristics when Ag is somewhat less 1. This is done to avoid the transition to supercritical mode with imprecise performing optimal control law, in particular because of the static and dynamic errors in control systems. The transition to supercritical mode for such SVZ is usually not desirable in view of the sharp increase in disturbances in the flow front of the engine.

Sometimes to reduce the stroke of the wedge panels needed to ensure the normal operation of SVZ by throttling the engine and to increase system performance, in addition to the management area of ​​the throat used control valves venting.

Supersonic OT mixed compression trigger regulation have two significantly different modes of operation:

Mode "not starting" when the shock is embossed front of the plane entrance, set by the throat and supersonic flow to subsonic flow passage upstream of the compressor takes place through the closing compression shock.

The "launch" mode, in which the supersonic flow is carried out inside the SVZ channel from the entry plane to the closing shock located behind the throat, λ> 1; in this case, a in the "start" mode is significantly higher than in the "non-start" mode.

The transition from the first mode to the second is provided by performing a certain sequence of actions - the "launch" procedure. To do this, increase Fr and open the air release flaps until the shock wave "swallows" in front of the entrance plane. In this case, Ar increases and a decreases. After "swallowing" the head wave, it is necessary to reduce the Fr section of the valves so that the closing shock wave in the channel is located at a given distance from the throat with Ar somewhat higher than 1. As the number M increases, the calculated value of Ar increases.

Under the influence of perturbations (wind gusts, maneuvers J1A) can happen almost instantaneously (in a time of the order 0,01) transition mode "not starting," accompanied by a drop in pressure in front of the engine on 30%. .50%, A significant increase in the SVZ and external resistance, as a rule, the engine surge.

To control SVZ mixed compression near the calculated values ​​of Mach numbers of flight when it is necessary to provide a specific geometry of the compression surfaces and inner channel defined.

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