| 摘要 |
879,956. Gas-turbine jet-propulsion engines. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. Sept. 2, 1959 [Sept. 4, 1958], No. 28497/58. Class 110 (3). An air intake for aircraft designed for flight at supersonic speed, comprises opposite walls defining an intake mouth, the mouth leading rearwardly through ducting to an air consuming combustion engine, e.g. a ram jet or gasturbine, one wall having a forwardly directed lip portion and the other wall including a member arranged to extend forwardly of the lip portion so shaped that under design operating conditions shock-wave formations therefrom extend towards a focus near the lip portion of the intake, and a shroud supported externally of the intake mouth and extending at a lower incidence to the air flow than the lip portion of the intake to intercept the shock wave arising from the forwardly-directed lip of the intake mouth. An annular intake, Fig. 1, comprises an annular wall 1 having a mouth 1a and a forwardly facing lip portion 1b. A centre body 2 is supported in spaced relation to the wall 1 to form a duct 3 leading to an airconsuming engine. The forward part of the body 2 is profiled to a point 2a and the surface 2b is shaped so as to direct shock waves C arising from the surface to a focus at or near the lip portion 1b. The lip portion 1b gives rise to a shock wave S1 which is a high angle shock wave because of the high incidence of the wall 1. To reduce the losses associated with the shock wave S1 an annular shroud 4 is supported in spaced relation to the wall 1 so that its leading edge intercepts the shock wave S1 and reflects it through the annular space between the shroud 4 and wall 1. The low angle of incidence of the shroud 4 produces a weaker shock wave S2 which results in a reduction in wave drag. The shroud 4 should be made as short as possible to minimize skin friction. The mutually facing surfaces 4b, 1c are profiled to give a compressive convergent portion 5, a parallelsided portion and an expansion divergent portion 6. The faces 1c, 4b thus mutually extinguish the disturbance caused by the other; shock waves produced by the wave 1c being cancelled by the aid of face 4b. The intake is described applied to a conventional gas-turbine engine and to a by-pass engine. The engine may be applied to a rectangular intake. |
