Patent GB-647406-A (GB)
Title: Improvements in gas turbines
IPC: F02C6/16
Filed: 1947-12-29
Abstract: 647,406. Gas turbine plant. TERCE, P. J. J. Dec. 29, 1947, No. 34381. Convention date, Feb. 23. 1945. [Class 110(iii)] [Also in Group XXIX] A gas turbine plant is arranged for providing the same useful power at four different operating speeds. The bladed rotor drives the air-compressors and one fuel pump for the combustion chamber. The oppositely-rotating stator provides the useful power and drives a second fuel pump. Power is transferred from the bladed rotor system to the useful power system by means of a motor driven by the excess air delivered by the compressors. Change from one speed to another and to an idling speed is effected by simultaneous regulation of the air inlets to the compressors and the fuel supply from the pump driven from the useful power shaft. The fuel supply from the other pump is regulated to maintain constant the pressure of the compressed-air supply. There are two compressors in parallel. The inlet to one of them has only two settings : a full opening for all the four operating speeds and a fully throttled opening for idling speed. The inlet to the other is fully throttled for both the top speed and the idling speed and has a progressively increasing opening for the other speeds, with the largest opening for the lowest. The gas turbine comprises a bladed rotor 4 mounted on a shaft 5 and an oppositely-rotating casing 1, carrying nozzles 2 and exhaust passages, mounted on a useful power shaft 3. The casing is coupled directly to a combustion chamber 6 with a labyrinth packing 26. Fuel is supplied to the combustion chamber through nozzles 10, 11 by pumps 12, 13. The pump 12 is driven from the shaft 3 and the pump 13 from the shaft 5. Combustion air is compressed in pumps 15, which may be in two stages with intercooling, driven from the shaft 5. There are two pumps 15, operating in parallel but with different regulation. The air is delivered to a reservoir 14, and passes to the combustion chamber and to an air motor 18 which is drivingly connected with the shaft 3. The air from the pumps 15 passes through an exhaust gas heat-exchanger (not shown) which is located within the reservoir 14. The delivery of fuel to nozzles 11 is regulated by means of an escape pipe 33 which is opened by a pressure-responsive device 22 when the pressure in the reservoir 14 rises. The delivery of fuel to nozzles 10 is regulated by means of an escape pipe 51 the opening to which is controlled by a speed-responsive device 23 driven from the shaft 3. The device includes a five-stepped obturator valve 53, Fig. 7, co-operating with an orifice 52. Each of four of the steps corresponds to one of the four operating speeds. At the idling speed the largest part is at the orifice. One of the air pumps 15 has its inlet regulated by a two-stepped obturator valve controlled by a speed-responsive device 24 driven by the shaft 3. The inlet is fully open for the four operating speeds and is throttled at the idling speed. The inlet to the other air pump is regulated by a four-stepped valve, controlled by the device 24, which substantially closes the inlet for both top speed and idling speed, opens it fully for the lowest speed and closes it in steps for the higher speeds. The turbine nozzles are divided into two groups; one group for use at the four operating speeds and the other for idling. Each nozzle is supplied from a separate chamber in the rotating casing. The entry to each of the chambers supplying the normal turbine nozzles is governed by a ball valve 71, Fig. 11, in a chamber 67 having an outlet, 56 and an inlet 69 in a wall having a number of slots 70, Fig. 12. At idling speed, the flow of gas through slots 70 carries the ball 71 to the outlet 56 which it closes. At operating speeds, the ball is carried by centrifugal force to the position shown. The entry to each of the chambers supplying the idling speed nozzles is governed by a ball 66, Fig. 10, in a radially positioned chamber 62 in the casing. At idling speed, the ball is on the seat 65 and the passage to the chamber from 60 by pipes 63 is open. At operating speeds the ball moves under centrifugal force to the radially outer seat 64 and closes the passage. At the same time the auxiliary nozzles are connected to atmosphere past the seating 64 in less than that of seating 65 so as to provide a greater seating area on which the gas pressure acts.