GB599502A - Improvements in or relating to power plants - Google Patents

Abstract

599,502. Servomotors. SULZER FRERES SOC. ANON. March 23, 1945, No. 7394. Convention date, March 30, 1944. [Class 135] [Also in Groups XXVI and XXVII] A power plant comprising a compressor and a precompressor, each separately driven, has means which in accordance with a service factor of the precompression will limit in at least one direction the range of adjustment of the output regulating means of the power unit driving the compressor. A free piston power gas producer, Fig. 3, having a combustion cylinder 13 and compression cylinders 12, supplies combustion gas to a useful output turbine 14, which may drive a generator or a ship's propeller, and a turbine 4 which drives a precompressor 1. The latter supplies air to the free piston engine. A pump 30 supplies pressure medium to a pipe 31, the pressure being under the control of a centrifugal governor 20 by means of a throttle valve 32. The pressure is communicated through pipe 28 to the face 29 of the control valve 24 of a servomotor 21 which operates the fuel regulating valve 3 through a lever 26. The return of valve 24 to the non-operative position is effected by a cam surface on the lever 26 through a spring 25. A valve 33 which is subject to the pressure in a pipe 35 communicating with pipe 28 shuts off the latter from pipe 31 when the pressure exceeds a certain value, so that further increase of pressure in pipe 31 cannot result in a corresponding increase in pressure in pipe 28. Any pressure medium leaking from pipe 31 to pipe 28 escapes through pipe 45. When the pressure in pipe 31 falls again, the leakage from pipe 28 enables the pressure in the latter to fall correspondingly, so that valve 33 rises to restore communication. If the pressure falls below a certain minimum, piston 34 makes contact with valve 24, and further fall of pressure has no effect on the latter, which is now under the control of springs 25 and 37 only. The upper and lower limits of the control range are adjusted in accordance with the pressure of the precompressed air by a pressure-sensitive capsule 43 which varies the loading on springs 36 and 37 by means of cams 40, 41. In existing plants with hydraulic transmission of the regulating impulse, the device shown in Fig. 4 may be used. As before, the pressure in pipe 31 is under the control of governor 20 and pipe 28 is, in this case, the connection to the control valve of some known type of servomotor. Pressure medium is supplied through pipe 51 and discharged through pipes 52. Under normal conditions the pressure in pipe 28 is equal to that in pipe 31. If the pressure in pipe 31 rises above the upper limit, piston 47 makes contact with valve 46 and prevents further pressure rise in pipe 28. Piston 48 performs a similar function in respect of the lower limit. As before, the limits of the control range are set by cams 40, 41 under the control of the precompression pressure. The interval between the upper and lower limits may be altered by means interposed between the cams 40 and 41.