GB595642A - Improvements in or relating to gas-turbines - Google Patents

Abstract

595,642. Gas turbines ; screw fans and compressors. GRIFFITH, A. A. April 23, 1945, No. 10182. [Classes 110 (i) and 110 (iii)] A power plant comprises two gas turbines supplied from the same source of working fluid and exhausting to the same back pressure, one turbine providing the useful output and driving a compressor or fan functioning as a pre-compressor for the working fluid ahead of the main compressor, which is driven by the other turbine. The said compressor or fan operates in an annular duct which surrounds the whole power unit, and extends lengthwise thereof to supply a propulsion jet, the air supply for the main compressor being taken from this duct on the delivery side of the fan. The exhaust from the two turbines is delivered into the propulsive jet. A multi-stage fan 37 of the type described in Specification 595,643 is driven through a hollow shaft 32 by the power turbine 31 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 main compressors 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 having guide blades 24, 25 to the compressor blades 16 which deliver it through a passage 26 to a combustion chamber 27 having a rotating 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 power turbine 31 and is discharged through exhaust ducts 41 formed in radial struts 12 into exhaust pipes 42 which extend beyond the air intakes 22. The exhaust gas preheats the air taken in through the intakes 22 to a certain extent. The pipes are of gradually increasing section to minimize losses. The ducts 41 are cooled by air which enters the struts 12 through suitable openings, not shown, and is discharged through the hollow interior of guide vanes 43. The exterior of the casing 14 is cooled by air which enters through openings in the forward end of' the casing 11 and is discharged through the annular space 44. The rotor drum and rotor blade roots of the power turbine 31 and the roots of the turbine blades 17 may be cooled by air bled from the delivery passage 26. Other parts of the power plant may be cooled by air bled from the annular duct between the casings 10 and 11. Cooling liquid such as methanol or methanol and water may be injected into the ducts 23 and into the cooling air between the casings 10 and 11. The fuel and lubricating pumps 45, 46 are driven by gearing 47 from the rearmost rotor 15. Other auxiliaries may be driven from the shaft 32 or preferably by a compressed air turbine supplied from the delivery passage 26. Provision may be made for varying the area of the propulsive jet and for burning additional fuel in the jet. The plant is started by jets of compressed air or gas from nozzles 48 at the inlet end of the contra-rotating turbine.