Patent GB-893029-A (GB)
Title: Improvements in installations comprising at least one freepiston gas-generator and at least one turbine driven thereby
IPC: F02B71/06
Filed: 1959-07-01
Abstract: 893,029. Gas turbine plant. SOC. D'ETUDES ET DE PARTICIPATIONS EAU, GAZ, ELECTRICITE, ENERGIE S.A. July 1, 1959 [July 18, 1958], No. 22647/59. Class 110 (3). [Also in Group XXVII] In a gas turbine plant comprising at least one turbine driven by gas supplied by at least one free-piston gas generator, the or each gas generator has a valve capable of assuming different degrees of opening and controlling the flow of relatively cool air upstream of the power cylinder, at least at low loads, and controlled in dependence on the load on the turbine, and two stop-valves, each having only two operating positions, viz., open and closed, are provided, one stop-valve controlling the supply of hot gas to the turbine or turbines and the other stopvalve controlling the release of hot gas to a region at or near atmospheric pressure. In consequence of having only two operating positions, the stop-valves are readily designed to operate at high temperature. The receiver 18 1 , Fig. 3, of a free-piston gas generator I is connected through a valve O 1  to the inlet manifold F of a gas turbine T and through a valve P 1  to a by-pass manifold D leading to the turbine exhaust pipe, the valves being closed when the gas generator I is not in use. Two further free-piston gas generators and their associated receivers and valve gear are provided, their connections to the manifolds D, F being shown at II and III. When the gas generator is started, the cyclic variation of pressure in the cushion 8b acts through non- return valves 65, 68 to establish a pressure differential between the two sides of a piston 64 whereby a double-pole switch 59 is closed. If the gas generator I is the first to be started, switch 60 remains in the position shown, and a solenoid valve 54, 54a is operated to admit air to a cylinder 52 from a pressure source S whereby valve O 1  is opened to admit gas to the turbine T. If, however, other gas generators are already in use, the pressure in receiver 18 1  is initially less than that in manifold F, the pressure difference acting on a piston 61 to move switch 60 to its other position, whereby a solenoid valve 55, 55a is operated, admitting air to a cylinder 53 to open valve P 1 . The gas from receiver 18 1  is now by-passed to the exhaust pipe D until the pressure in receiver 18 1  has risen sufficiently to return switch 60 to its former position, whereupon valve O 1  is opened and valve P 1  is closed. Racing of the turbine T under sudden no-load conditions, for example an electric power cut-off, can be prevented by reversing the connections to the solenoids 54a, 55a by means of a relay m, whereby valve O 1  is closed and valve P 1  is opened. A time delay switch 69, closed by the power cut-off, opens again to return the valves O 1 , P 1  to their former positions after a time lapse sufficient to obviate danger of racing. When the gas generator I is stopped, the pressures on opposite sides of piston 64 are equalized through a throttled passage 67, and switch 59 opens to return valves O 1 , P 1  to their closed positions. The gas generators are provided with the fuel supply control and the valve for re-circulating compressed air to the compressor inlet at low load described in Specification 787,430. In the marine plant shown in Fig. 5, the valve O 1  of Fig. 3 is replaced by valves O av1  and O ar1  controlling the supply of gas to ahead and reverse turbines T av  and T ar  respectively. Switches 59, 60 operate as in Fig. 3, but piston 61 is in this case under the joint control of the inlet pressures of the two turbines. In this embodiment, the reversing relay m does not affect the operation of valve P 1  but instead reverses the positions of the two valves O ar1 , O avr . In the event of racing (when, for example, propeller 70 leaves the water), a speed governor energizes relay m to close one of the valves O av1 , O ar1  and open the other, whereby a braking effort is applied. Ahead and astern running is controlled by switches 73, 74 actuated by a handle 72. In the intermediate position of the handle 72, both switches 73, 74 are closed to energize both turbines whereby the propeller shaft is held stationary by the cancellation of the two opposing torques, allowing the gas generators to idle while the ship is stopped. The handle 72 also controls the fuel supply to the gas generators and the recirculation of hot air to the compressor inlets, as described in Specification 787,430, the minimum fuel supply being obtained at the intermediate position of the handle.