Patent GB-777572-A (GB)
Title: Improvements in or relating to gas turbine power plants
Inventor: WILLGOOS ANDREW VAN DEAN
IPC: F02C3/06
Filed: 1954-02-02
Abstract: 777,572. Gas turbine jet-propulsion engines. UNITED AIRCRAFT CORPORATION. Feb. 2, 1954, No. 3104/54. Class 110 (3). [Also in Groups XII and XIX] Turbines driving axial flow compressors; jet-propulsion plant also operating propellers.- A gas turbine power plant for aircraft comprises an axial flow compressor, a gas turbine, a shaft connecting the rotors of the compressor and turbine, a plurality of individual combustion chambers arranged circumferentially around the shaft, and a sleeve-positioned concentric with the shaft and radially inward of the combustion chambers, the sleeve being coextensive axially with the latter and also being connected to the compressor stator by a ring assembly and to the turbine stator by an annular disc to form jointly with the compressor and turbine stators the sole supporting and aligning frame for the elements of the power plant. The plant is adapted to drive an aircraft propeller and also to provide additional thrust for jet propulsion. The weight-supporting structure comprises the outer wall 86 of the air inlet duct 88, the outer casing 124 of the compressor, the ring assembly which forms an accessory-carrying section and which consists of an annular disc 156 connecting an outer ring 148 to an inner ring 154, a sleeve 190, annular disc 204 and the outer casing 208 of the turbine. A plurality of combustion chambers 14 encircles the sleeve 190, and the driving shaft passes through the latter. The compressor rotor 114 carries at its forward end a shaft 24 coupled by means of a double-reduction sun-and-planet gearing to the propeller shaft 22, journalled in a support bearing 68 and thrust bearing 70. Said gearing is mounted or the inner wall 94 of the air duct 88, the walls of the latter being connected together by hollow struts 84 and 110. The first stage of the reduction gearing is associated with a torque meter of the piston and cylinder type. The rear end of the compressor rotor carries a hollow shaft 144 on which is mounted a sleeve 184 and a flanged ring 186 held in place by a nut 188 screwed on the free end of the shaft. Ring 186 is bolted to the end of a hollow cylindrical structure 284 projecting forwardly from the turbine rotor. A bolt 290, having a ring 288 disposed between the head thereof and an internal flange on member 284, extends both through the latter and also with clearance through the turbine rotor and through a hollow shaft 286 projecting rearwardly from the latter. The turbine rotor comprises discs 252, the foremost of which is engaged by lugs 296 projecting radially from bolt 290. The discs are clamped together by means of a nut 292 which screws on to the end of bolt 290 and engages the end of shaft 286. Sleeve 190 is formed with four radial webs 192 connected at their forward ends to the accessory section and at their rearward ends to disc 204. Each of the combustion chambers, of which there are eight in number, comprises an outer shell 210 spaced by rings 214, 216 from an inner shell 212. The outer shell is clamped at its forward end by a split ring 218 to the compressor discharge manifold 150 which is supported by the ring section. A flexible expansion section 224 is inserted in the outer shell, and the rear end of the latter is clamped by a split ring 222 to the turbine inlet manifold 220. The inner shell carries internally at its forward end a conical flame ring 172 communicating with a fuel nozzle 166 which is mounted on the outer ring 148 to the accessory section. The delivery end of the nozzle is surrounded by a sleeve 174 through which primary air enters the inner sleeve. Secondary air enters the latter through a series of perforations 232 formed in the wall of the sleeve. The combustion chambers are enclosed within a casing 236 formed with an opening 242 to which a ram air inlet 244 is attached for pressuring the space between casing 236 and sleeve 190, said air pressure being excluded from the turbine rotor by a flexible seal 346. The turbine stator comprises the outer casing 208 and an inner casing 246 separated therefrom by concentrically spaced heat shields 332, 334, 336. The middle shield 334 and inner shield 336 have forward extensions 344 which extend inwardly to surround the turbine inlet manifold 220 and inlet nozzle 260. Shields 332 and 334 end a short distance rearwardly of the last turbine stage, but shield 336 continues downstream to a point which is within the discharge duct 338 and is close to the outer wall 340 of the duct to form a constriction, whereby the flow of exhaust gas causes cooling air to be ejected from the spaces between the shields. A shell 342 secured to the inner casing 246 ends coterminously with shell 336. Cooling air also enters the hollow shaft 144 through perforations 145 in the latter, and after passing through the clearance space between bolt 290 and the turbine rotor discs, also passes between face splines 282 connecting said discs together to enter sealing rings 280 mounted between adjacent discs, the air then escaping through small openings 300 in rings 280 to flow over the faces of the turbine discs. Shaft 286 is journalled in a bearing 308 enclosed in a space defined by a seal 316 on one side and a cover-plate 318 on the other, said space being provided with cooling air supplied by ram air inlets connected to radial pipes 304 which support the bearing. The air is extracted from said space by a centrifugal fan 325 which is provided on the rearmost disc of the turbine rotor and which discharges into a conical shell 326 which surrounds the bearing and forms the inner wall of the gasdischarge duct 338, said cone being open rearwardly at 328. Casings and stators.-The compressor stator casing 124 comprises four segments which are bolted together through flanges 127. Projecting inwardly from the casing are vanes 123 which are carried by rings 128, the latter seating in grooves formed in the casing and being secured therein by screws 129. The inner ends of the vanes are interconnected by rings 132 which carry inwardly projecting sealing flanges 134. The inner casing 246 of the turbine comprises nozzle rings 260, 262, 264, the rings being connected together by bolts 266 and each ring being formed in two segments connected together by bolts 268. Vanes 248 which project inwardly from the inner casing are interconnected at their outer ends by rings 270, each of which is welded to a corresponding nozzle ring. The inner end of each vane has a lug 272 which enters a groove 274 provided in a sealing element 276, the latter having inwardly extending flanges co-operating with sealing rings 280 mounted on the rotor between adjacent discs. The inner casing 246 is connected to the outer casing 208 by radial pins 254 positioned in bosses 256 and 258 provided on the outer and inner casings respectively. Rotors.-The compressor rotor comprises discs 136, each of which is formed with a circumferential upstream flange 141 and a similar downstream flange 142. The adjacent flanges overlap and are fastened together by plug welding. Each compressor blade 125 is formed at its root with fingers 139 which enter circumferential slots 138 in the supporting disc and are attached therein by a pivot pin 140. The turbine rotor comprises discs 252 interengaged by face splines 282 and clamped together by the bolt 290. The turbine blades 250 are welded to the discs. Arrangement of auxiliary apparatus; mounting and supporting.-A gear 72 mounted on the propeller drive shaft 22 engages with gears 74 and 76 mounted on angularly-positioned shafts 78 and 80 which pass through the struts 84. Accessories, such as a gear pump 90, may be connected to the outer ends of said shafts, the accessories being mounted on brackets 92 carried by the outer wall 86 of the air inlet duct. A gear 179 mounted on the shaft 144 meshes with a plurality of pinions 180 supported by the accessory section. The outer ring 148 of the latter is provided with eight angularly spaced mounting pads 162 which are located out of. alignment with the combustion chambers. Alternate pads support suitable accessories such as the pressure and scavange oil pumps for the lubrication system, the accessories being driven from the pinions 180. The intervening pads receive engine mounts by which the power plant is supported within an aircraft. Arrangement of bearings; lubricating passages.-Bearing 112 supporting the front end of the compressor rotor is carried by a web 116 attached to the inner wall 94 of the air inlet duct 88. The shaft 24 passing through bearing 112 is surrounded on the upstream side of the latter by a seal 100 carried by a web 102 attached to said inner wall, and on the downstream side by a seal 118 carried by web 116. The seals prevent lubricant from entering the air duct, and define a sump chamber 119. Lubricating oil passes through a pipe 121 to a nozzle 122 which sprays the oil against the bearing, the oil then draining away from sump 119 through a pipe 120. The sump is vented through a pipe 122<SP>1</SP>. The bearing 308 supporting the rear end of the turbine rotor is carried by a support member 302 having hollow radial legs 304 guided within sleeves 306 carried by the outer casing 208. The bearing is enclosed within a chamber 314 by a seal 316 at one side and a cover-plate 318 on the other side. Lubricating oil for the bearing passes through a pipe 312 located in one of the legs 304, and oil collecting within the chamber is scavanged through said leg and is pumped away through a pipe 320. The bearing is cooled by air provided by ram air inlets 322 located in the legs 304, the air being exhausted by a centrifugal fan 325 provided on the rearmost turbine disc. Chamber 314 may be vented by a pipe 330 located within one of the legs 304.