Patent GB-874622-A (GB)
Title: Improvements relating to gas turbine engines
IPC: F02C3/10
Filed: 1959-08-25
Abstract: 874,622. Gas-turbine plant. GENERAL MOTORS CORPORATION. Aug. 25, 1959 [Sept. 10, 1958], No. 29023/59. Class 110 (3). A gas-turbine engine comprises a turbinecompressor assembly and a separate power turbine, the engine comprising a forward frame having a first shaft support in which the turbine - compressor assembly is rotatably mounted, a first turbine casing being mounted on the shaft support, two rigid rails being fixed to the forward frame and extending generally parallel to and on opposite sides of the shaft to a rear frame to which the rails are fixed, the rear frame having a second shaft support in which the power turbine shaft is rotatably mounted coaxially with the first shaft, a power turbine casing being mounted on the second shaft support, and a resilient connection being provided between the two turbine casings. The engine comprises two rotary regenerative heatexchangers 33 disposed one on either side of the engine with their axes normal to the axis of the turbines. A transverse bulkhead 34 of arcuate section is disposed across the plant normal to the main axis, the bulkhead being apertured to permit the peripheral heatexchanger matrices to pass therethrough. A combustion chamber 36 is disposed horizontally at each side of the engine between the forward portion of the heat-exchanger matrix and the bulkhead. The matrices are driven by the compressor turbine by means of gearing 77, a longitudinally extending shaft 76 and a transversely-mounted shaft 66 driven from the shaft 76 by means of a worm and worm-gear 74, 73, pinions 72 on the transverse shaft engaging with ring gears at the peripheries of the side flanges 68 of the heat-exchanger matrices. Air from the compressor 21 flows through annular outlet 28 through the forward arcuate portions of the matrices 71 where it is preheated, then into the combustion chambers 36 where fuel is injected and burned, the combustion gases discharging through flame tube outlets 37 parallel to the engine axis to act first on the compressor driving turbine 23 and then on the separate power turbine 42, the exhaust gases then flowing radially outwardly through the rearward arcuate portions of the heat-exchanger matrices 71 which are thereby heated. The gases pass into exhaust gas chambers 48 from which they finally discharge through outlets 55. A second transverse shaft 67 is provided below the first one 66 to support the matrices but this second shaft is not driven. Rollers 82, 83 at the forward parts of the peripheries also serve to support the matrices. Seals are provided at the inner and outer flanges 68 of the rotary matrices, also at the apertures where the matrices pass through the bulkhead 34. The two flame tubes 36 are interconnected by means of a pipe 57. The forward frame is shown in detail in Fig. 4 and comprises a cast or welded structure having a forward wall 26, upper and lower flanges 101, 102 and a rearward wall 103 which is formed with a shaft support 32. An opening in the rearward wall 103 through which access to the gearing 77 may be obtained is closed by means of a cover-plate 134 which supports a lubricating oil pump 131, 132. The compressorturbine shaft 22 is supported in the forward frame by means of bearings 117 and 122, the compressor impeller 21 being mounted at the forward end of the shaft and the turbine rotor 23 at the rearward end. A plate 27 having a central air intake portion 109 secured thereto is supported forwardly of the plate 26 so as to afford the compressor housing and annular diffuser 28. The gearing 77 is driven by means of a pinion 119 secured on the shaft 22. the driven shaft 129 driving the pump 131, 132 and being connected by a splined coupling to the shaft 76. The arcuately-sectioned bulkhead 34 is bolted to the flanges 101, 102 of the forward frame, the bulkhead having a central aperture in which a cylindrical member 40 is secured, the cylinder 40 together with a casing 58 forming combustion gas inlet duct to the turbine inlet nozzle 38. The casing 58 includes a portion 59 of arcuate form which is secured to the bulkhead 34. Longitudinally-extending rail members 168, 180 formed integrally with the bulkhead 34 at the upper and lower portions thereof extend rearwardly to the rear frame member 63, the rails being of openchannel section, the drive shaft 76 extending along the upper rail 168. The rails 168, 180 are secured to the rear frame 63 (see Fig. 4a), which is a rigid box-section member having a shaft support 191 integral therewith in which the power turbine shaft 44 is rotatably supported in bearings 204, 205, the reduction gearing 46, 47, shown in Fig. 1, being housed in a casing 94. The worm shaft 193 by which the heat-exchanger matrices are driven forms an extension of the shaft 76 and is rotatably supported in the rear casing 63. The space between the matrices rearwardly of the bulkhead 34 is bridged by a rear wall portion 166 of arcuate form with a flattened upper portion 301, the forward ends of the wall 166 being secured to the bulkhead by means of upper and lower brackets 161, 163. The compressor turbine casing 39 is connected to the bulkhead cylinder 40 by means of a flexible ring 288, but is primarily supported by the shaft support 32 forming part of the forward frame by means of a nozzle support 217 comprising a hub portion 219, radial arms 222 and a rim portion 221. The hub 219 is secured to the shaft support 32 and the rim 221 supports the turbine inlet nozzle segments 38, the turbine casing 39 being supported by the outer shroud portions 232 of the nozzle segments. The power turbine casing 43 is supported from the shaft support 191 by means of six tubular struts 264 secured at their outer ends to the casing 43 and at their inner ends to a support ring 266 which is in turn secured to the shaft support 191. A resilient connection is provided between the two turbine casings 39, 43 by means of a flexible ring 283 similar to the ring 288. A sheet metal diaphragm 258 is disposed between the two turbine discs 23, 42 being supported from the turbine casing 43 by means of the inter-stage nozzle assembly 256. The gases issuing from the power turbine are guided by means of a deflector 64 which is secured to the support ring 266. Heat shields 218 and 273 are disposed upstream of the compressor turbine disc 23 and downstream of the power turbine disc 42 respectively. Cooling air supplied through passages 293, 294 flows across the upstream face of the turbine disc 23; some air also flows through bores in the discmounting bolts 297 and then across the downstream face of the disc. The gases discharge from the power turbine to the spaces within the heatexchanger matrices 71 downstream of the bulkhead 34 as may be seen in Fig. 5, the gases then issuing into the exhaust chambers 48. Two separate cover-plates are provided at each side of the engine, one 49, being connected to a flange of the exhaust chamber 48 and to a side flange of the bulkhead 34, and the other, 51, being connected to the edge of the forward frame and also to the side flange of the bulkhead 34. A double-walled combustion chamber end wall 52 is secured to each cover-plate 51, each end wall supporting a fuel injector and an igniter. The heat-exchanger matrix driveshaft 66 carries two sleeves 353 at each end thereof, each sleeve being formed with a pinion 357 and a roller portion 356 which co-operate with a ring gear 352 and a roller track 351 formed on the end ring 68. Foraminous material 71 is disposed between the two end rings of each heat-exchanger. Details of the seals provided adjacent the end rings of the heatexchangers also at the openings in the bulkhead where the matrices pass therethrough are given. Specification 873,623 [Group XIII] is referred to.