Patent GB-1227052-A (GB)
IPC: F01D3/00
Filed: 1969-02-28
Abstract: 1,227,052. Gas turbine engines - cooling. GENERAL ELECTRIC CO. Feb.28, 1969, No. 10753/69. Headings F1G and F1T. The invention relates to a gas turbine engine having means for supplying cooling air to the turbine blades, there being valve means for regulating the flow of cooling air to the blades and means for preventing undesired axial thrust on the turbine rotor assembly when flow of cooling air to the blades is shut off. The engine shown comprises compressor 14, combustion equipment 16 and a turbine 20, the turbine and compressor rotor being inter-connected by shaft members 40, 42, 44. The turbine rotor comprises a pair of discs 30 which are inter-connected by members 31, 32 which define a chamber to which cooling air flows and from which it flows to cooling passages in the blades 28. The inner air casing wall 18 is formed with an opening 49 through which a portion of air from the compressor passes into a chamber 50. A series of aerofoil struts 46 entend across the annular air flow passage and one of the struts is formed with a hollow rectangular base portion 25 which defines a cooling air regulating valve. Cooling air flows from the chamber 50 through openings 56 in the strut 46. A pair of ducts 57, 58, 59 and 68 extend from the valve assembly, the first duct 57, 58, 59 leading to a cooling air chamber 60 defined by walls 62, 64 which are sealed to the rotor assembly at 63, 65, and the second duct 68 leading to a thrust balancing chamber 70 defined by walls 62, 71 which are. sealed to the rotor assembly at 63, 72. A third chamber 73 is defined by the wall 71 and is subject to turbine inlet pressure. When cooling air is to be supplied to the turbine, the valve assembly permits air to flow to the chamber 60 from which it passes through openings 61 in the rotor shaft 42 and thence to the chamber defined by the members 31, 32 and so to the blade passages. When cooling air flow is shut off air flows through the duct 68 to the balance chamber 70 so that axial thrust on the rotor assembly is substantially constant. The valve assembly comprises a valve plate 79 formed with an elliptical opening 80 having a bevelled edge defining a valve seat. A valve member 81 co-operates with the valve seat being shown in the closed position. The valve member is movable by means of a piston 91 to which hydraulic fluid may be supplied through inlets 96, 97, the piston being connected to the valve member by a rod 89 and universal joint 90, the rod extending through the hollow strut 46. A member 83 is secured to a plate 84 which is secured to the strut assembly, the member 83 carrying a pair of tubular members 82 which extend through the valve member 81 and serve as guides therefor. The tubular members inter-connect with a passage 87 which in turn connects with passage 88 and duct 68. A plunger member 93 is carried by the valve member 81 such that when the valve member 81 is in the closed position shown so shutting off flow of cooling air to duct 57, 58, 59 and chamber 60, the plunger 93 is in the open position whereby pressurized air may flow through ducts 82, 87, 88, 68 to the end thrust balance chamber 70. On the other hand when the valve member 81 is moved downwardly to the open position so permitting flow of cooling air to the chamber 60 and to turbine blades 28, the plunger 93 is moved downwardly to shut off the ducts 82, 87 so shutting off flow of pressurized air to the balance chamber 70. Pressurized air from the chamber 50 also flows through openings 56 into the struts 46 and thence through duct 55 to an external point of use.