Patent GB-851156-A (GB)
Title: Installation including a free-piston gas-generator and a prime mover driven by the power gas
IPC: F02B71/06
Filed: 1958-03-25
Abstract: 851,156. Combustion product power plant. SOC. D'ETUDES ET DE PARTICIPATIONS EAU GAZ ELECTRICITE ENERGIE S.A. March 25, 1958 [April 30, 1957], No. 9596/58. Class 7(1). [Also in Groups XXVI and XXIX] A power plant comprising one or more free piston gas generators supplying power gas to a turbine, the supply of fuel to the gas generators and the opening or closing of a gas delivery aperture between the gas generators and the turbine being controlled, in normal operation, by a control impulse from a turbine driven speed governor, has an additional control device which becomes operative for a short time upon abrupt decrease in load on the turbine to render ineffective the control impulse to one or more of the gas generators. The turbine 1 is supplied with power gas by a conduit 2 to which are connected a number of free piston gas generators. In normal operation, the fuel supply is regulated by a rack 11 controlled by a speed governor 16 driven by the turbine 1. The governor 16 produces in the conduit 17 a pressure which increases as the speed of the turbine falls. This pressure acts on a spring loaded piston 20 which moves the member 11. Control surfaces 22, 23 co-operate with an abutment 24, the position of which is determined in accordance with the operating pressure of the gas generator, to limit the minimum and maximum fuel supply. A valve 15 which controls the flow of gas through the conduit 14 to the turbine and through the conduit 25 to atmosphere is also controlled by the pressure in the conduit 17. A special safety regulator 28 is also provided. When the turbine exceeds its maximum permissible speed, the lever 35 is pivoted outwards and the slide valve 30 moves to the right so the conduit 29 is connected to the drain conduit 37. The resulting fall in pressure in the conduit 29 causes the valve 34 to open and cut off the fuel supply to the gas generator. A slide valve 38 is actuated by the pistons if they exceed their maximum permissible outward stroke, to connect the conduit 29 to a drain conduit 39. Owing to the length of the conduits 29, there is a delay between the times of operation of the slide valve 30 and the valve 34. The pressure in the conduit 29 is arranged, therefore, to operate a switch 40 close to the slide valve 30. Closure of the switch 40 energizes a relay 42, which in turn closes a switch in the circuits 43, 47. The circuit 43 energizes a relay 44 which actuates a slide valve 45 close to the gas generator and causes the valve 34 to open. The circuit 47 energizes relays 48 the number of which is equal to the number of gas generators. Each relay 48 operates a slide valve 49 which disconnects the conduits 19, 26 from the control conduit 18 and connect them to a drain outlet 50. This causes the control member 11 to be moved to the point of minimum fuel injection and the valve 15 to be moved so that the conduit 14 is closed and conduit 25 opened. Should the safety regulator 28 fail to operate, the relay 42 may be energized by a speed indicator having contacts in parallel with the switch 40 or by a hand switch 51a. If as shown, the turbine 1 drives an electric generator connected to a distribution system through a circuit-breaker 53 and the circuitbreaker is suddenly opened, the safety regulator 28 may operate and stop all the gas generators. To avoid this, the circuit-breaker 53 is arranged, when tripped, to close a switch 54 to energize a relay 55 and close a switch 56. The switch 56 causes the relay 48 to operate the slide valve 49 which in turn causes the fuel supply to be reduced to the minimum and the conduit 14 closed by a valve 15. After a few seconds e.g. ten seconds, an automatic time switch, e.g. a bi-metallic strip 57, opens and causes the switch 56 to open. This allows the valve 49 to resume its original position and the pressure impulses from the speed regulator 16 to act on the fuel control 11 and valve 15 of each gas generator. In a modification, Fig. 2 (not shown), the switch 54 is connected to the fulcrum of a lever one end of which is connected to a spring loaded piston actuated by the power gas pressure and the other end to a watt meter relay. If the loading of the turbine varies slowly the lever pivots about its fulcrum. A sudden decrease in load causes the fulcrum of the lever to be displaced to actuate the switch 54. When the power gas pressure corresponds to the new loading the switch 54 is re-opened.