GB883548A - Air motor-compressor assemblies - Google Patents

Abstract

883,548. Centrifugal compressors; turbines; stuffing-box substitutes. GARRETT CORPORATION. June 13, 1958 [June 13, 1957], No. 19039/58. Classes 110 (1), 110 (3) and 122 (5). An air motor-compressor assembly comprises a compressor impeller mounted on a shaft which extends into a compartment isolated from the working spaces of the impeller by a shaft seal subjected on one side to the pressure of the fluid flowing through the impeller and on the other side to the pressure in the compartment, an air motor driving the shaft, a passage connecting the compartment to the pressurized air inlet to the motor, and pressure adjusting means for adjusting the pressure in the compartment to a valve close to that on the first side of the shaft seal. A centrifugal compressor 10, Fig. 1, is driven by an air turbine 11. Air is bled from the inlet scroll of the turbine through a pipe 70 and supplied by way of a duct 55 and an annular chamber 54 to a number of cooling passages 51 to cool the bearings. The air then passes by way of an annular chamber 60 and a duct 61 to a space 62 which is vented to atmosphere through a restricted orifice 64 which maintains the pressure in space 62 at a high value. A baffle 91 ensures that the air flows over the back of the turbine rotor to cool it. If necessary, a heat-exchanger is provided in the pipe 70 to cool the bled air before use. Some of the air in space 62 leaks past a labyrinth seal 43 into a compartment 90 to make the pressure in the latter substantially equal to that in space 62. When the compressor is stationary, leakage is prevented by means of a seal 24 similar to that described in Specificatin 875,319, but when the compressor is in operation, the seal 24 is opened by means of an annular piston 25 actuated by air supplied from the duct 55. Leakage is then opposed by a rotary seal 35, Figs. 1 and 3, subjected on its outside to the pressure at the compressor inlet 20 through a passage (not shown) and subjected on its inside to the pressure in the compartment 90. The latter pressure is maintained slightly below the compressor inlet pressure by means of a regulating valve 71 in the pipe 70, to ensure that any leakage through the seal 35 is of refrigerant out of the compressor instead of air into the compressor. The seal 35 comprises a stationary ring 38, of carbon or other selflubricating material, housed in a retainer 39 and pressed against a rotor 22 by means of a corrugated spring 46. Retainer 39 is sealed to its housing by an 0-ring 40. A sealing ring 41 co-operates with a flange 42 on the turbine rotor. Specification 875,318 also is referred to.