GB704351A - Improvements in and relating to turbines operated by gases supplied by free-piston gas-generators - Google Patents

Abstract

704,351. Gas turbine plant. MUNTZ & CO., Ltd., A. March 14, 1952 [March 21, 1951], No. 6812/51. Class 110 (3). [Also in Group XXIX] In a gas turbine plant comprising a free piston gas generator feeding an inward radial flow turbine having adjustable inlet nozzle blades, the nozzle blades are automatically set in accordance with the pressure of the gas supplied to the turbine so that at least over the range of relatively low gas pressures, the nozzle area is increased with reduction of gas pressure. The exhaust gases from a Diesel cylinder 3, Fig. 1, of a free piston gas generator pass through a duct 21 to the volute 22 of a radial inward flow turbine. The gases pass inwards from the volute through adjustable nozzle vanes 38 to the vanes 39 of the rotor 23 from which they are exhausted through adjustable guide vanes 40 and fixed guide vanes 33 to the duct 31. The guide vanes 38 are mounted on shafts 42 on the other ends of which are arranged pinions 43 which mesh with a toothed ring 44. The toothed ring 44 is operated by a quadrant 58, Fig. 2, which engages alternatively by means of a cam follower 64 two cams, 59, 59' for forward and reverse running respectively between which it is moved manually as required by means of a hand lever 65. The gas pressure on the vanes 38 keeps the cam follower on the surface of the cams. A spring loaded piston 66 in a cylinder 67, which is connected by a pipe 68 to the engine case 12 of the gas generator, controls the position of the cams 59, 59' through linkwork 71, 76. The adjustable guide vanes 40 are actuated by a second toothed ring 46 which is connected to the first toothed ring 44 through belt connections, mechanical gearing and a lost motion connection 53. The lost motion connection is so arranged that small adjustments of the nozzle vanes 38 may take place without affecting the guide vanes 40. Movement of the blades 38 from the forward to the reverse position is sufficient to transmit motion to the vanes 40. The purpose of the vanes 40 is to reduce the amount of swirl in the exhaust gases. To prevent a sudden increase in speed of the turbine with a sudden decrease of load, a turbine driven governor 101, Fig. 12, is arranged to operate a fuel pump 118, a throttle valve 119 in the gas supply pipe 21 and the adjustable nozzle vanes 38. On an increase of turbine speed the governor collar moves to the right and operates the pilot valve 105 to allow fluid to pass into the right hand end of the cylinder 112 and push the rod 109 to the left. The rod 109 which is connected at one end to the operating rod of the fuel pump 118 and at the other end, through a dashpot 129, to the throttle valve 119 and a nozzle vane operating arm 133 thus reduces the fuel supply, closes the throttle valve 119 and opens the adjustable nozzle vanes 38. The throttle valve is spring loaded to the open position and the rate at which it returns to the open position is determined by the adjustment of a valve 139 on the dashpot 129. Stops 123, 124 are provided to limit the movement of the throttle 119. To allow movement of the fuel pump control rod 117 when the throttle actuating arm 122 is against one of these stops, non-return valves 155, 156 are also fitted to the dashpot. The arm 133 is attached to a cam 135 which operates the toothed ring 44 through a pivoted toothed sector 137 and follower 136. The cams 59 and 135 can be operated independently of each other to move the nozzle vanes to the open position. According to the Provisional Specification the nozzle area may be progressively reduced as the power is reduced or may be kept constant down to the blow-off point and then increased. It is also stated that a suitable mechanism for varying the nozzle blades is as disclosed in Specification 586,913. An arrangement in which the throttle valve and variable area nozzles are so interlinked that changes of speed vary the variable area nozzles and the rate of change of speed controls the throttle valve, is referred to. These members may be controlled by the variations of the gas pressure instead of speed. In a further arrangement described, the throttle valve is arranged to be operated only when the fuel control is moved to its minimum setting.