Patent GB-926192-A (GB)
IPC: F02B71/06
Filed: 1960-09-28
Abstract: 926,192. Gas turbine plant. SOC. D'ETUDES ET DE PARTICIPATIONS EAU, GAZ, ELECTRICITE, ENERGIE S.A. Sept. 28, 1960 [Nov. 5, 1959], No. 33356/60. Class 110 (3). [Also in Groups XXIX and XXXIII] A power plant comprising at least one free piston gas generator feeding a turbine has main control means, including a control member operable by an attendant of the plant, for adjusting the output of gas from the gas generator and further control means operating, in dependence upon the speed of the turbine, upon the main control means so that when the turbine speed exceeds a predetermined value the output of gas is reduced independently of the setting control member or when the turbine speed falls below a predetermined limit the output of gas is increased independently of the setting of the control member or both. One or preferably a plurality of free-piston gas generators A supply power gas to a gas turbine T driving a variable pitch propeller H through reduction gearing R. The output of gas from the generator A is controlled by regulating the injection fuel pump 6 and a valve 9 which controls the recycling of hot compressed air back to the intake of the compressor. The pump 6 is controlled by a piston 11 and the valve 9 by a piston 15 both of which are responsive to the pressure in a conduit 20. The output of the plant is controlled by a hand wheel 21 which rotates a cam 29 which positions a piston 27. Fluid under pressure from a source 22 passes through an orifice 23 into a cylinder 24. The pressure in the cylinder 24 is determined by the loading of the spring 28 acting on the piston 25 which is itself determined by the position of the piston 27 relative to an orifice 26 in the piston 25. To prevent racing of the turbine T when the propeller H leaves the water, a pressurereducing device controlled by a speed governor driven by the turbine is provided in the conduit 20. This pressure reducing device comprises a slide valve 33 with a throat 34 which, in the position shown, connects the upstream and downstream sections of the conduit 20. When the turbine speed exceeds a predetermined maximum, the governor 53 moves the plunger 52 to increase the pressure in the conduit 45. This causes the piston 38 to move to the right and interrupts communication between the upstream and downstream sections of the conduit 20 and connects the downstream section to the discharge pipe 35. The resulting fall in pressure causes the pistons 11 and 15 to reduce the output of the gas generator. The pressure difference between the two sections of the conduit 20 act on the piston 40 to cause it to move to the left to re-establish communication between the upstream and downstream sections of the conduit 20 whilst maintaining a pressure drop between them as long as the turbine T overspeeds. For each turbine speed, there is a corresponding pressure drop. The speed at which the pressure-reducing device operates may be pre-set by a hand wheel 55a. The speed of the turbine T may be prevented from falling below a predetermined minimum by increasing the compression of the spring 28. When the speed falls to the predetermined value, the governor 56 acts on the plunger 52a to increase the pressure in the conduit 57. This pressure acts on the piston 58 forming a support for the spring 28. A single governor may be used to operate the plungers 52, 52a. A cam 60 actuated by the hand wheel 21 may be used to set the pitch of the propeller blades 68. The cam 60 may be adjusted axially by a hand wheel 78. The cam 60 keeps the pitch of the blades 68 at their maximum value when the gas generator is idling or running at very low power. Specification 787,430 is referred to.