Patent GB-1026910-A (GB)
Title: Gas turbine engines having rotary regenerative heat exchangers
IPC: F02C7/105
Filed: 1965-03-25
Abstract: 1,026,910. Gas turbine plant. GENERAL MOTORS CORPORATION. March 25, 1965 [April 21, 1964], No. 12646/65. Headings FIG and FIT. In a gas turbine engine having a housing, as of aluminium, divided into high and low pressure chambers by a bulkhead 39, air drawn in by a compressor 14 is discharged into the high pressure chamber and through part of a rotary regenerative heat exchanger 48 to a combustion chamber 11. The combustion products pass through a nozzle box and a first nozzle ring to a turbine wheel 12 driving the compressor 14 through a shaft 15, and then through a second nozzle ring to an output turbine wheel 17 exhausting through the low pressure chamber, the other part of the heat exchanger, and an outlet. The top and bottom surfaces of the heat exchanger, and rectangular openings in the bulkhead receiving the heat exchanger are provided with seals. In the high pressure chamber the top of the housing, the bulkhead 39 and a cover for the shaft 15 are protected from the combustion chamber by insulated shields comprising an insulating material, such as ceramic fibre, placed between two metal plates. The shields are spaced from the parts they protect to provide passages for air bypassed from the compressor for cooling purposes. In the low pressure chamber, the top of the housing, the bulkhead and a cover for the shaft of turbine wheel 17 are provided with insulating shields for protection from the exhaust gases. The by-passed air passing around the cover for shaft 15 passes through four metering holes 372, Fig. 5 (not shown), and a gap 373 to cool the rim of the turbine wheel 12. Additionally, an annular passage 382 adjacent the nozzle box permits some of the air passed through the heat exchanger to by-pass the combustion chamber and flow directly to an outlet upstream of the first nozzle ring to provide a layer of cooling air over the bases of the blades of turbine wheel 12. Since, on starting, the temperature of this air gradually increases it minimizes thermal shock at the blade bases. The outer shroud of the first nozzle ring is split into seven segments by narrow slots to permit expansion. The shaft carrying the turbine wheel 17 has a pinion meshing with a gear-wheel 20 splined to an output shaft, e.g. the input shaft of a gearbox or automatic transmission. The gear-wheel 20 is geared to a gear-wheel 101 connected to a shaft 89<SP>1</SP> through a multi-plate clutch 99. The shaft 89<SP>1</SP>, driving an oil pump 125, is connected to the shaft 15 through a shaft 89 and the geartrain shown. The gear-wheel 85 includes a speed sensor and drives a torquemeter 86. Engagement of the clutch 99 permits transfer of power from the turbine wheel 12 to the output shaft, or use of the compressor as a brake for the output shaft. A fuel pump and control assembly 91 is driven by the shaft 89. A starter motor 92 is connected to the shaft 89 by gearwheels 93, 94. The shaft 89<SP>1</SP> drives, via gearwheels 95, 97 and shaft 98, a roller 53 driving the heat exchanger by frictional engagement with the upper and lower rings 49 thereon. A second roller 54, Fig. 3 (not shown), forming an idler roller, is provided at the other side of the low pressure chamber. The heat exchanger is kept in contact with these rollers by the pressure drop between the two chambers. The bearings at the ends of the rollers are lubricated by oil supplied by the pump 125 through openings 124, Fig. 3 (not shown), in caps 116 and the hollow interior of each roller. Additionally, the shaft 98 is hollow to permit lubrication of a bearing at the lower end thereof. The interior of each roller is lined with heat insulating material. A set of two rollers 142, Fig. 4 (not shown), forming part of the bulkhead to heat exchanger sealing means, and spring loaded against the heat exchanger, is arranged diametrically opposite each of the rollers 53, 54. One of these sets is associated with means 171 for supplementing the spring loading during starting when the pressure drop between the two chambers is low. This supplementary loading is automatically cancelled when the pressure in the high pressure chamber reaches a suitable value. A wheel 136 supports the heat exchanger in the axial direction.