GB885753A - Blow-off control device for jet propulsion units - Google Patents

Abstract

885,753. Jet propulsion plants. B.M.W. TRIEBWERKBAU G.m.b.H. Feb. 26, 1959 [March 29, 1958], No. 6704/59. Class 110 (3) [Also in Group XXIX] An air intake for a ram jet engine comprising an outer shell surrounding a central cone the apex of which is arranged upstream of the leading edge of the casing, has a cylindrical slide valve which controls the area of blow-off ports in the outer shell of the intake casing actuated by the pressures in front of and behind the perpendicular shock wave so as to increase the flow area through the ports against a restoring force when the shock wave migrates upstream and allows the restoring force to reduce the area of the ports when the shock wave migrates downstream. In the ram jet air intake shown, Fig. 1, the supersonic air stream impinges upon the central cone 1 and experiences first an oblique compressional shock 2 and then a perpendicular shock 3 which, under critical operating conditions, should impinge on the leading edge 4 of the outer shell 5. After passing through the shock 3, the air enters the subsonic diffuser 6 leading to the combustion chamber having a flame ring 8. Behind the supporting stays 6 is a rotatable fuel injector 10, the struts of which carry a sleeve valve 11 provided with peripherally spaced ports 12. Rotation of the valve 11 covers and uncovers the blow-off ports 13 which are divided lengthwise by partitions 14 to improve the outflow when the ports are partially open. The injector 10 is connected to a rotary piston 15, which has vanes located between vanes 16<SP>1</SP> extending radially inwards from the casing 16. The vanes of the piston 15 are subject to the pressures at the points 17, 18 on the surface of the cone 1. Point 17 is located on the surface where the perpendicular shock strikes the surface of cone 1 under critical operating conditions and point 18 is located upstream of this point. The action of these pressures are balanced by the torque in a torsion bar 19. The arrangement is such that the ports 13 are uncovered completely if the shock wave 3 migrates in the forward direction of flight and covered completely if the shock wave 3 moves rearwardly. The slide valve 11 may move axially instead of rotating. In a modification, the pressures at the points 17, 18 control a servo-piston valve which controls the main rotary piston pneumatically. To avoid excessive loading of the vanes of the rotary piston when the shock wave migrates suddenly and unexpectedly in the forward direction a spring- loaded by-pass valve may be arranged between the ducts 17, 18.