GB719996A - Improvements in and relating to dual liquid fuel systems - Google Patents

Abstract

719,996. Gas turbine plant. GENERAL ELECTRIC CO. Nov. 19, 1952 [Nov. 24, 1951], No. 29232/52. Class 110(3) [Also in Groups XI and XXXIV] A dual liquid fuel supply system for a power plant comprises a primary system and an auxiliary system for supplying respectively a heavy fuel such as " Bunker C " and a lighter fuel such as diesel oil to a transfer valve arranged to connect one or other of the systems to the combustion equipment of the power plant and an accumulator arranged to be supplied from the auxiliary system and to automatically feed the combustion equipment when the pres sure of the system at the time connected to the combustion chamber falls below a preselected value. The fuel supply to a gas turbine 1 is controlled by a regulator 4 which varies the rate of delivery of the engine driven fuel pump 3. Successful operation of the pump 3 requires that fuel is supplied to the inlet 3b of the pump at substantially constant pressure and that it is adequately lubricated through the oil system 3c, 3d. The dual fuel system comprises a primary system 5 for supplying heavy oil such as " Bunker C ", an auxiliary system 6 for supplying a lighter oil such as diesel oil, a transfer valve 7 for interconnecting the two systems and an accumulator 8 for preventing excessive fuel pressure variations. The primary system 5 comprises a main fuel oil storage tank 9, two first stage fuel pumps 10a, 10b, a centrifuge 11, a second fuel tank 12, two second stage pumps 13a, 13b, and a heater 14. An electric or steam heating coil 9a is inserted in tank 9. Pump 10b runs at all times. When the level in the tank 12 falls to a preselected minimum the switch 10e operates to start the pump 10a. The pump 13b runs during normal operation but the pump 13a only runs when the pressure in the discharge conduit 16 falls below a predetermined value. The conduit 16 leads through a check valve 16a to the transfer valve 7. A pressure regulating valve 17 mounted in a byepass 18 maintains the pressure in the discharge conduit constant. The auxiliary system 6 comprises a supply tank 19, two supply pumps 20a, 20b discharging through check valves 20c, 20d and 22 to the transfer valve 7. The pressure in this system is maintained constant by a pressure regulating valve 23 in a by-pass conduit 24 at a value higher than that in the primary system so that heavy oil does not leak into the auxiliarv system. The pump 20b is always in service, the pump 20a starts up when the pressure in conduit 21 falls below a preselected value. The transfer valve 7 is connected to the inlet of the fuel pump 3 through a conduit 26 containing a shut-off valve 27. Light oil from the auxiliary circuit passes through a check valve 28 to the pump lubricating circuit 3c, 3d. A conduit 29 connecting the conduits 26, 3c, contains a regulating valve 30 and the accumulator 8. The arrangement is such that at starting, the transfer valve 7 is in the position shown and the lighter fuel is supplied by the pump 20b to the conduit 26 up to the stop valve 27 which is closed, to the accumulator 8 and the lubricating system 3c. 3d. The turbine is now started by the starter motor, the valve 27 opened, and the combustion chambers ignited. In the meantime, the fuel tank 9 is heated and the pumps 10b, 13b started. The heavy fuel is then passed through the heater 14 to the transfer valve 7 through a passage 7c in the valve and conduit 19, 18 back to the tank 12. The heavy oil is thus kept circulating through the heater 14 until the parts reach normal working temperature when the valve 7 may be moved by handle 7g to the position in which the conduits 16 and 26 are in communication. This operation shuts off the connection between the lighter fuel supply conduit 21 and the conduit 26. If, during starting, the pump 20b fails, the pump 20a would be started up by the pressure switch 25. This may result in a temporary fall in pressure in the conduit 26 which will cause the valve 28 to close and the accumulator 8 to supply the conduit 26 and lubricating oil circuit 3c, 3d. When the pressure rises to its normal value, valve 28 opens and the accumulator is re-charged. If, during operation of the primary system, the pressure falls excessively, the valve 30 opens and fuel is supplied from the accumulator 8 to the engine. On complete failure of the primary system, the valve 7 may be moved manually or automatically to the position in which the auxiliary system is in operation. Specification 697,564, [Group XXVIII], is referred to.