Patent GB-682469-A (GB)
Title: Improvements relating to gas turbine plants
IPC: F02C7/18
Filed: 1950-05-17
Abstract: 682,469. Gas turbine plant. BEDUE, A., and LAURE, M. May 17, 1950, No. 12339/50. Class 110(iii) A gas turbine comprising at least one stage in which a hot gaseous medium axially traverses a part of the rotor blade ring and cooling gas traverses another part of the blade ring has a centrifugal impeller in the turbine casing which supplies cooling gas to a connecting passage leading to the rotor blade ring and one or more diverting passages to receive cooling gas at the port or ports of the rotor blade ring where the working medium is admitted. Figs 1 and 2 are sections through a gas turbine rotor taken in planes through the part of the periphery traversed by the working medium and cooling gas respectively. In this particular arrangement, the working medium is supplied by passages 6 leading to arcuate, chambers at the top and bottom of the casing. A pre-compressed cooling gas is supplied to a centrifugal impeller 12 where it is compressed in passages 13 which are subdivided at the periphery by blades 14. The cooling gas is, at the parts of the periphery occupied by the passages 6, diverted through channels 17, Fig. 1, into a chamber bounded by the casing 1 and impeller shroud 16 and then used to cool parts of the turbine exposed to the high temperature working fluid. At the parts of the periphery not occupied by the passages 6, the cooling gas is prevented from passing through the channels 17 by a closure plate 18, Fig. 2; but is admitted to the rotor blades 8 through connecting passages 19. Guide members 21, are provided in the passages 19. To prevent shock losses due to unsteady flow, the change over from the connecting passages 19 to the diverting channels 17 and vice versa is made gradual by allowing these two channels to overlap. In a modification; the blades 14 are provided with axial extensions which are inclined in the direction opposite to that of the rotation so that the absolute exhaust velocity of the cooling air may approximate more nearly to the axial direction. In another modification, fixed guide vanes are provided in the casing to convert the velocity of the air leaving the channels 17 into pressure. In a further modification, the cooling gas impeller is driven through gearing from the turbine shaft. In the arrangement shown in Fig. 11, the cooling gas after passing through the impeller blades 45 is divided by blades 45a into the chambers 50, 50a where it cools the parts 34, 35 of the turbine casing. Part of the cooling gas also passes through passages 67 in the turbine stator blades 39. In the parts of the periphery of the turbine not occupied by the inlet pasages 48 the cooling gas is diverted through the rotor blades 40 by deflectors attached to the turbine casing. The cooling gas may flow in a closed circuit and be cooled in an external cooler 65 or a liquid cooling medium may be passed through a jacket 66 surrounding the outlet pipe 53. A gas turbine plant, Fig. 18 has a turbine 106 of the type described driving a compressor 101 which supplies air through a heat exchanger 103 to a combustion chamber 104 supplying one section of the turbine blades and from which compressor cooling air is bled and then heated in a heat exchanger 108 and passed through a centrifugal impeller 110 to another section of the turbine blades. After leaving the turbine 106, the combustion products and air are mixed and passed through a useful power turbine 113, the exhaust of which is used to heat the heatexchangers 103, 108: An'adjustable covering member controlling ports for the supply of cooling gas to the impeller may be provided.