GB1116542A - A diffuser arrangement - Google Patents

Abstract

1,116,542. Jet propulsion engine air intakes and jet nozzles. BOEING CO. March 15,1966 No. 11308/66. Headings F1G and F1J. [Also in Division G3] The invention relates to a convergent-divergent duct in which the convergent and divergent portions of the duct each comprise a plurality of deformable segments hinged together along edges extending in the direction of fluid flow through the duct, the convergent and divergent portions being hinged together, there being means for altering the crosssectional slope of said portions. The duct may be applied either as an air intake structure or as a propulsion nozzle of a jet propulsion engine. The invention is described with reference to an air intake structure of a jet engine and comprises an outer duct 10 which is movable between a rearward or retracted position Fig. 3 in which it provides an air inlet opening of circular form, and a forward or extended position Fig. 4 in which the air inlet opening is of figure eight form and of reduced area. The structure comprises also a convergent-divergent air intake diffuser disposed within the duct 10, the diffuser in the Figure 3 position having a throat 20 of figure eight form and inlet and outlet sections of circular form while in the Fig. 4 position the throat 20 is of circular form, the inlet is of figure eight form, the outlet section 19 remaining of circular form. The jet engine is indicated at 16 adjacent the outlet section 19. The inlet structure is shown in Fig. 5 and comprises an outer duct 10 which is formed by sections 11,12 which are secured at their longitudinal edges by hinge means 13, 13<SP>1</SP> the sections forming a duct of cylindrical form in the retracted position, and a duct which changes from a circular form at its rearward end to a figure eight form at its forward end when in the extended position which is shown in Fig. 8. Disposed within the duct are tracks 21, 21<SP>1</SP>, 22, 22<SP>1</SP> which are secured to beams 23, 23<SP>1</SP>, the tracks 22, 22<SP>1</SP>, diverging in the direction of air flow and the tracks 21, 21<SP>1</SP> being parallel. Sliders 24, 24<SP>1</SP> are mounted on the tracks 21, 21<SP>1</SP>, and sliders 25, 25<SP>1</SP> are mounted on the tracks 22, 22<SP>1</SP>, the sliders being secured by brackets 26 Fig. 6 (not shown) to the duct sections 11,12. The duct sections 11,12 are movable from the retracted position shown in Fig. 5 by means of a shaft 30 which may be driven by the gas turbine engine 16 (not shown), the shaft acting through gearing 28 to drive pinions 37 which engage racks 38 secured to each of the duct sections 11,12. As the sections are moved forwardly to the extended position the sliders 25, 25<SP>1</SP> are constrained to follow the tracks 22, 22<SP>1</SP> so that the duct deforms about the hinges 13, 13<SP>1</SP> and assumes the figure eight configuration indicated at 15, Fig. 4, at its forward inlet end. The diffuser disposed within the duct 10 comprises a convergent portion 49, which also comprises two sections hingedly secured together along their longitudinal edges 50, and a divergent portion 48 which also comprises two sections hingedly secured together along their longitudinal edges 50,the convergent and divergent sections being hingedly secured together around the periphery of the throat 20 as indicated at 51, 51<SP>1</SP>. The duct 10 bears against the forward end of the convergent portion 49 of the diffuser so that as it moves forwardly to the extended position so it causes the convergent portion to assume a corresponding figure eight configuration 18, Fig. 4. At the same time the divergent portion 48 is adjusted to form a throat of circular form 20, Fig. by means of a drive from the shaft 30 acting through gearing 40 to rotate two screwed rods 45, 45<SP>1</SP> which carry nuts 46, 46<SP>1</SP> which bear against the walls of the divergent portion which are thereby caused to move radially outwardly Fig. 8. The gearing 28 is disposed within an intake fairing 29 and the gearing 40 within a pair of hollow struts 41 secured to the fairing. In an alternative arrangement Figs. 10, 11 (not shown) the duct 10 comprises a pair of members 11,12 hingedly secured together along the longitudinal edges 13, 13<SP>1</SP> as in the first embodiment but link members 54, 54<SP>1</SP> are pivotally connected between the forward ends of the members 11, 12 and the forward end of the intake fairing 52 so that as the members 11,12 are moved forwardly to the extended position the forward portions thereof are constrained to move about the pivot point 53 and the inlet opening again assumes a figure eight form of reduced area. The forward end of the convergent portion 49 is moved by the movement of the duct sections 11,12 as before. The duct and convergent-divergent diffuser may comprise more than two sections such as 11,12, for example a duct comprising three sections is described with reference to Figs. 12,13 (not shown).