GB1327618A - Shrouded propellor drives - Google Patents

Abstract

1327618 Boundary layer control MESSERSCHMITT-BOLKOW-BLOHM GmbH 8 Oct 1970 [11 Oct 1969] 47963/70 Heading F2R A shrouded propeller drive comprising a rotatable propeller, shroud means around the propeller including a shroud ring, the propeller having a streamlined hub which together with said ring defines a boundary over which a layer of air is moved by rotation of the propeller, means for varying the outlet cross-section of the shroud from the propeller downstream of the said ring, and means adjacent to the propeller for generating stabilized layer vortices to influence the air flowing over at least some of the boundary surfaces. In Fig. 1, a shrouded propeller drive mounted on an aircraft has a rotatable hub 2 which is rigidly attached to propeller blades 1 having a shroud ring 4. The shroud also includes a casing comprising split flaps 8, 8<SP>1</SP> pivotable at hinges 50 on the leading edge of a fixed inlet duct 5 coextensive with ring 4, from position 8 to position 8<SP>1</SP>. A gap 6 between the duct 5 and ring 4 causes a stabilized layer vortex 28 to form to prevent breakaway of the airstream 52 from the propeller when the flaps are in position 8<SP>1</SP>. A fixed hub body 3 includes an annular trough 10 and an annular gap at 11 through which engine exhaust gas passes to form a vortex within the trough 10 to guide air into the duct 5. Exhaust gas is also passed through the gap 12 between the hub body 3 and the rotatable hub 2. In Fig. 2 the blades 15 are not shrouded, the shroud means comprising a ring 14 having an annular tube 13 and an annular slot 13 for blowing exhaust gas to form a vortex between the ring 14 and flaps 17, 17<SP>1</SP>. Features 2<SP>1</SP>, 3<SP>1</SP>, 10<SP>1</SP>, 11<SP>1</SP> are analogous to those 2, 3, 10, 11 in Fig. 1. In another embodiment, Fig. 3 (not shown) the front fan of a front fan jet engine has a casing extending around and to the rear of the fan and formed with a ring having an annular trough and gap analogous to those in the hub body of Fig. 1. Flaps are pivoted to the outside of the trough and extend rearwardly thereof. A blown annular gap is formed on a hub body which extends rearwardly of the fan and flaps.