Patent GB-595663-A (GB)
Title: Improvements in or relating to gas-turbine power-plants
IPC: F02K3/06
Filed: 1945-07-18
Abstract: 595,663. Gas turbines ; screw fans and compressors. GRIFFITH, A. A. July 18, 1945, No. 18470. [Classes 110 (i) and 110 (iii)] A power unit comprises a gas turbine driving an air compressor, and another turbine driving a propeller or fan, all of which are arranged coaxially to rotate about a stationary central tie-bar or shaft. The latter takes the end thrusts of the air compressor and the turbine driving it and trans.- mits the net end thrust to a main structure of the unit. A multi-stage fan 37 of the type described in Specification 595,643 is driven through a hollow shaft 32 by a turbine 33 and takes in air through the annular space between an outer casing 10 and an inner casing 11, delivering part to the main compressor through intakes 22 in the forward faces of radial struts 13 and discharging the remainder rearwardly as a propulsive jet. The shaft 32 is journalled in bearings 52 and 53, carried by spiders 35 and 36 respectively. The main compressor and the turbine driving it are of the type comprising contra-rotating rotors 15, each carrying an inner ring of compressor blades 16 and an outer ring of turbine blades 17. The air entering the intakes 22 flows through ducts 23 to the compressor blades 16 which deliver it through a passage 26 to a combustion chamber 27 having a burner 28 of the type described in Specification 595,644, [Group XXII]. Part of the products of combustion flows back through the turbine blades 17 and is discharged through the annular space between an inner casing 29 and a cowl 30 ; the remainder flows forwardly through the turbine 33 and is discharged through exhaust ducts 41 formed in radial struts 12 into exhaust pipes 42 which extend beyond the air intakes 22. The rotors 15 are mounted to rotate on a stationary tie-bar 18 by means of ball bearings 50. The tie-bar is supported from a casing 14 by fixed discs 19, 20, 21, each of which have rings of fixed compressor blades and turbine blades, and is further supported by a coned member 51 secured to the disc 20 and by the spider 36. The combined end thrust of the turbine 33 and fan 37 is transmitted to the spider 36 through a piston 54 mounted on the shaft 32 and located in a cylinder 55 formed in the spider 36. Compressed air is bled from the combustion chamber 27 into a space 62 and thence through the centre of the shaft 32 into a space 56 from which it passes through a hole 57 into the cylinder 55 for the purpose of acting upon the piston 54 to balance the end thrust. Holes 63 in the drum 31 of the turbine 33 are provided to ensure that the air pressures on the ends of the drum are equalized. The forward end thrust on the spider 36 is taken by the tie-rod 18 through a collar 59 and is partly balanced by the rearward endthrust of the rotors 15. The net end thrust is transmitted through a collar 58 to the stationary disc 20, which in turn transmits it through the casing 14 to the radial struts 12 and 13. The power unit is supported in the planes of the struts so that the loadings on the latter are transmitted directly to the aircraft structure. Specification 595,642 also is referred to.