GB800602A - Improvements in or relating to jet propulsion gas turbine engines - Google Patents

Abstract

800,602. Gas turbine plant. BRISTOL AERO-ENGINES, Ltd. March 12, 1956 [March 16, 1955], No. 7683/55. Class 110 (3). In a jet propulsion gas turbine engine comprising low and high pressure compressors driven respectively by low and high pressure turbines, the turbine structure comprises a row of fluid-cooled guide blades adapted to impart a swirl to the working fluid leaving the heating means such that its mean direction is between 60 and 70 degrees to the axial direction, a high pressure turbine rotor carrying a single row of fluid-cooled blades adapted to receive the working fluid directly from the guide blades and to discharge it, at design speed, with an oppositelydirected swirl having its mean direction between 35 and 55 degrees to the axial direction, and a low-pressure turbine rotor carrying a single row of blades adapted to receive the working fluid directly from the high pressure turbine blades and to discharge it, at design speed, substantially axially. Fig. 2 shows a cross-section of the turbine system of the engine. Combustion products impinge in an axial direction on stationary guide vanes 8 which imparts a swirl to them so that on leaving the blades their mean direction is inclined by 60 to 70 degrees to the axial direction. The blades 9 of the high pressure turbine deflect the fluid through a large angle to discharge it with an oppositely directed swirl into the blades 12 of the low pressure turbine. The two contra-rotating turbine rotors drive the respective compressors through the shafts 11, 14 to which the compressor rotors are attached. Relatively cool air from the discharge end of the high pressure compressor flows round the outside of the flame-tube system and passes radially inwards through the guide blades, thereby cooling the blades. The air passing through the blades is collected in an annular chamber 20 and conveyed through an adjacent chamber 21 to openings in an air guide disc 23 attached to the high-pressure turbine rotor. The air then travels outwardly and into gaps 24 between adjacent roots of the turbine blades and passes from there into two cooling passage systems 25, 26 formed in each blade and also over the blade root platforms of the low pressure turbine. A similar cooling system is provided for the low pressure turbine blades. Preferably subsonic blading is used for the compressors, and the engine is controlled to maintain the ratio of the low pressure compressor speed to the square root of the absolute temperature of the entering air constant. This may be done by providing a variable area jet nozzle (Fig. 1, not shown) controlled by a servo system. Specification 791,751 is referred to.