Bleed stability door

DETAILED DESCRIPTION It is therefore an object of the present invention to provide a supersonic diffuser duct which is self stabilizing against loss of flow due to pressure or flow perturbations.
According to the present invention, a supersonic diffusion duct is provided with a hinged stability door in the duct wall adjacent a continuous flow bleed area or vent The stability door, disposed upstream of a throat section in the diffuser, is biased into a closed position by a spring or other urging means during normal diffuser operation.
As noted above, during a pressure or other flow variation which forces the front of the shock train upstream from its normal location in the duct throat region, the increased static fluid pressure behind the shock train front is sufficient to open the stability door diverting a greater portion of the flow from the duct, thereby decreasing duct flow downstream of the shock train while maintaining let entrance flow, thus, retaining the shock train inside the duct.
As the perturbation flow condition subsides, the shock wave front retreats back downstream again entering the throat section of the duct and the stability door closes under the influence of the biasing spring or other means, thus returning the duct to a normal, efficient configuration.
It is a particular feature of the present invention to provide a stability door with a hinge oriented transversely with respect to the gas flow and having an upstream extending portion.
During stabilizing operation wherein the door is opened by the increased fluid pressure, the additional inertial force of the flow of the gas against the forward extending door portion acts to augment the opening force on the door and, in effect, to stabilize the stabilizer.
It is still further a feature of the present invention to provide the stability door as a portion of an "educated" bleed slot, thereby achieving a wide range of variable bleed flow ratio as the duct accepts subsonic and supersonic flows.