GB805352A - Improvements in or relating to axial-flow fluid machines having electrically heated blades - Google Patents

Abstract

805,352. Mounting inductor-alternators. ROLLS-ROYCE Ltd. April 11, 1956 [March 8, 1955], No. 6856/55. Class 35. [Also in Group XI] In heating for anti-icing purposes stator blades of an axial-flow fluid machine, e.g. an axial-flow compressor of a gas turbine engine, an alternator is disposed coaxially with the rotor 10 of the machine, the alternator having a rotor 24 which is magnetized or magnetizable axially and comprises axially spaced complementary solid polepieces 24b, 25b extending spokewise from a hub 24a mounted on a shaft 13 of the rotor 10 of the machine, and a stator comprising armature coils 32 arranged in annular assembly round the hub and extending between the polepieces, each coil 32 being electrically connected to insulated end parts of a pair of stator blades 19 whereof the other ends are electrically bonded so that the blades are heated by passage of current therethrough. The alternator is coaxially within the row of stator blades 19 to be heated, and each armature coil 32 is connected to inner ends of the associated pair of stator blades, the outer ends of which are bonded by a thick copper strip 38 accommodated in a recess 16 in the compressor casing 15. A stationary field coil 40 for excitation of the alternator rotor 24 is disposed coaxially about the hub 24a radially within the assembly of armature coils 32. The coils 32 are formed as stacks of U-form copper wires or strips, and each end of a coil is bonded to an end of a stator blade. The alternator stator may have an annular armature core 31 comprising a spirally wound strip of magnetic material embraced by the armature coils 32 and having parts with a small clearance from the polepieces. Radial bolts 33 may attach the casing 41 of the field coil 40 and the core 31 to inwardly radial projections 23 of the inlet guide vanes 19 and may also pass through the coils 32. The core may be slotted in its axially-spaced ends to receive the limbs of the coils 32. In Fig. 8 the annular core 131 is accommodated between the limbs of the U-coils 32 and has axially-extending laminated bridgepieces 132 placed circumferentially between adjacent coils 32. The bridge-pieces 132 extend out to substantially the width of the rotor 24 and have a small radial clearance from the polepieces 124b, 125b. When the armature coils 32 are stacks of U-form copper strips in planes at right-angles to the rotor axis, the core may be omitted. The N-poles of the alternator rotor are offset angularly to be midway between the S-poles. The excitation current to the field coil may be fed by leads between vane projections 23. The total number of poles on the rotor is equal to the number of coils to provide single-phase current but is less for polyphase current. The alternator may be disposed adjacent the outer end of the machine, and the coils may be connected by leads outside the easing to the stator blades, the inner ends of which are bonded together. The alternator may also supply current to other parts of the engine or aircraft which require protection against ice. The easing of the machine may be divided in the plane of the alternator so that the forward part 14 is removable to admit assembly of the stator of the alternator as a unit with the rows of stator blades to which the coils are connected. Specification 625,299, [Group XI], is referred to.