Self Lubricating Vane for a Rotary Vane Cooling System

This invention relates to a vane for use in a rotary vane reverse Brayton cycle cooling system.

The patents to Edwards, U.S. Pat. Nos. 3,686,893; 3,886,765; 3,913,351; 3,956,904; 3,977,852 and 4,088,426, describe cooling systems which operate on the reverse Brayton cycle.

In conventional rotary vane cooling systems wherein the vanes slide in slots in a rotor, vane actuation is achieved either by contact forces between the vane tips and the chamber wall or by the use of cams and cam rollers positioned at the two ends of the sliding vanes.

Vane actuation achieved by contact forces between the vane tips and the chamber wall results in increased vane tip friction and wear. Vane actuation by cams and cam rollers at the end of the vanes can result in excessive vane deflections with increased wear. High strength vane materials which reduce vane deflections have poor wear characteristics and result in excessive wear in the slots.

According to this invention vanes for use in reverse Brayton cycle cooling apparatus are constructed with high modulus of electricity fibers molded into a binding material such as an epoxy resin. The wear surfaces of the vanes include a material with self lubricating properties.

FIG. 1 is a partially schematic partially cut away view of a conventional reverse Brayton cycle rotary sliding vane cooling system with which the vanes of the invention could be used.

FIG. 2 is an enlarged side view of a vane such as used in the device of FIG. 1, according to the invention.

FIG. 3 is a schematic sectional view of the device of FIG. 2 along the line 3--3.

FIG. 4 is a schematic illustration showing fiber orientation such as could be used in the device of FIGS. 2 and 3.

FIG. 5 is a schematic illustration showing fiber orientation as could be used in the surface region in the device of FIGS. 2 and 3.

Reference is now made to FIG. 1 of the drawing which shows a rotary vane gas cycle cooling system 10 having a rotor 12 on a shaft 14 within housing 16. The rotor 12 includes a plurality of vanes 18 which slide in slots 20, as in a conventional rotary vane cooling system. The vanes 18 have bearing supports 21 which are journalled into bearings 22 which ride on vane guide cams 24.

The vanes are made of a plurality of layers of high modulus elasticity fibers such as carbon fibers, boron fibers or Kevlar fibers. The fibers are molded into an epoxy resin. While these composite blades would not have individual layers of material after curing, the separate layers and epoxy resin are shown schematically at 26, 27, 28, 29, 30, 31 and 32 in FIG. 3. The orientation of the fibers in certain layers would be different than the orientation of fibers in certain other layers. One distribution of fiber orientations which could be used are shown at 26a, 27a, 28a, 29a, 30a, 31a and 32a in FIG. 4. The layers could be individually impregnated with epoxy resin and partially cured, with cutout regions 33 provided to receive bearing supports 21, with the layers being bonded together around the inserts in a final curing operation or fibers could be made up in sheets and covered with binding material as each sheet is laid in a mold and then molded around the inserts in a single curing operation. The outer layer indicated schematically at 34 is made of a material with self lubricating properties.

The surface region 34 of the vanes could be made with polytetrafluoroethylene fibers in an epoxy resin binder with an orientation, as shown at 34a in FIG. 5, which orientation would correspond to the radial orientation of the fibers shown at 29a in FIG. 4. The surface region 34 could also be made with glass, boron or Kevlar fibers with a self lubricating material such as polytetrafluoroethylene powder or molybdenum-disulfide particles added to the epoxy resin binder. The use of carbon fibers in the surface region of the vanes would be undesirable for apparatus requiring long service life, such as in space applications, due to the corrosive properties of carbon.

Binder material other than epoxy resins could be used; for example, it may be desirable to use polyimid binders or other binders used in composite structures for some applications.

In the operation of the device a gas, such as air, from inlet 40 is compressed in compressor 42 and passes through outlet 44 to a conventional cooling heat exchanger, not shown. The gas from the cooling heat exchanger enters inlet 46 and is expanded in the expander portion 48 of the rotary vane cooling system. The expanded gas passes from outlet 56 to an environmental control heat exchanger, not shown, as in a conventional reverse Brayton cycle rotary vane cooling system. The composite structure reduces vane deflection and bearing wear. The self lubricating outer surface of the vanes reduce wear of the vanes and slots.

There is thus provided a reverse Brayton cycle cooling system with improved bearing wear properties and reduced vane and slot wear characteristics.