GB813343A - Improvements in or relating to apparatus for the control of ducted fluids - Google Patents

Abstract

813,343. Axial-flow compressors and turbines; jet-propulsion plant. POWER JETS (RESEARCH & DEVELOPMENT) Ltd. Oct. 19, 1956 [Oct. 21, 1955], No. 30114/55. Classes 110 (1) and 110 (3). [Also in Groups XXIX and XXXVIII] Apparatus for the control of ducted fluid comprises a number of vanes arranged across the fluidflow path and each extending longitudinally across the path, each vane being pivotable about a longitudinal axis to vary the obstruction of the vane to fluid flow, and the pivoting of each vane being controlled independently of at least some of the other vanes in dependence on variations in the velocity of fluid approaching the region of the vane in a sense to oppose the variations by varying the obstruction. Vanes 8, Fig. 2, at the inlet of an axial-flow compressor are each pivoted about a radial axis which is arranged downstream of the centre of pressure or lift of the vane so that the fluid force on the vane tends to increase its inclination to the direction A of the fluid flow. A leaf-spring 18 bears on a crank-pin 17 to oppose the blade rotation, which is limited.by stops 21, 22. In the fullyinclined position the vanes 8 lie in a transverse plane. The vanes may be of assymetrical faired form or may be flat plates. Vibration may be damped by a damper plate 62 operating in a partitioned dashpot 64. To prevent the fluid leaving the vanes with a circumferential component of velocity, the row of vanes may be divided into groups, the vanes in each group being connected by gearing 30, Fig. 5, so that adjacent vanes in the group pivot in. opposite directions. Instead of being fixed, the spring abutments 20 may be mounted on a ring 35. Fig. 6, which can be rotated with respect to the compressor stator casing 2 so as to vary the. force exerted by each spring 18 to compensate for variations in the mean velocity or density of the fluid at the inlet to the row of vanes. For this purpose, six upstreamwardly directed pitot tubes 57 are spaced evenly around the inlet and connected to a common manifold 56, the mean kinetic pressure so obtained being applied to the interior of a bellows 54. Six static pressure tubes 59, each adjacent to one of the pitot tubes, are connected to a manifold 58, the mean static pressure so obtained being applied to a chamber 55 enclosing the bellows 54. The ring 35 is turned through a link 37 by a servomotor 39 controlled by the bellows 54. The static pressure tubes 59 may be replaced by a suitably positioned single static pressure tube 60. Instead of being pivoted by the direct action of the fluid upon it, each vane may be pivoted by a servomotor controlled by the fluid. For this purpose, the spring 18 is omitted, and the link 37 of a servomotor similar to that in Fig. 6 is connected to the crank-pin 17. As before, the interior of the bellows 54 is exposed to the mean kinetic pressure sensed by the pitot tubes 57, while the chamber 55 is exposed to the local kinetic pressure sensed by an upstreamwardly directed pitot tube at the inlet to the vane or group of vanes being controlled. The pitot tubes may be located downstream of the vanes instead of upstream. Where a group of vanes is being controlled, the vanes may be connected together by gearing as in Fig. 5. Alternatively, where the group consists of two widely-spaced vanes 8, 8a, Fig 8, the vanes may be connected by a link 72 and crank-arms 17a, 73. Since the vanes are actuated by a servomotor, the pivot point of each vane need not be downstream of the centre of pressure or lift but may, as shown, by upstream instead. The hydraulic servomotor may be replaced by a reversible electric motor controlled by a diaphragm switch which replaces the bellows 54. The motor turns the vane through worm-gearing. The invention is applicable to vanes in the exhaust duct of an axial-flow turbine or upstream of the combustion system of a ram jet unit.