Improvements in or relating to axial-flow compressors

670,710. Axial-flow compressors. BRISTOL AEROPLANE CO., Ltd. May 30, 1950 [March 1, 1949; Aug. 23, 1949], Nos. 5640/49 and 21949/49. Class 110(i) [Also in Group A chamber is supplied with air by an axial-flow compressor, a thrust due to the air pressure in the chamber being applied to counterbalance the axial thrust of the compressor, means being provided to maintain the air pressure in the chamber below a selected value. The end face of a rotor 12 at the delivery of the first stage 5 of a two-stage compressor carries a disc 13 and labyrinth seal rings 14, 15 forming a closed chamber 21. Air leaking into the chamber establishes a pressure substantially ecual to the delivery pressure of stage 5, which pressure is exerted against disc 13 to counteract end thrust. Chamber 21 communicates through a hollow radial support arm 11, with a valve casing 28 containing a valve 33 which is normally closed by a spring 32 and oil pressure exerted through a duct 37. The oil pressure is derived from the lubricating system of the gas turbine or other engine of which the compressor forms a part. If the pressure in the chamber 21 exceeds a predetermined value, it opens the valve 33, permitting air to pass by way of passages 36 into a compartment 27, where it opens a valve 23 by which the chamber 21 is vented to atmosphere until the pressure is sufficiently reduced. Air trapped in the compartment 27 after the valve 33 has closed, which would otherwise prevent closure of valve 23, can escape through a restricted orifice 30.