Patent GB-1220107-A (GB)
Title: Control system for automatically adjusting the angularly movable guide blades of a power turbine of a gas turbine propulsion unit
Inventor: JURISCH WILHELM
IPC: F02C9/22
Filed: 1968-09-18
Abstract: 1,220,107. Gas turbine plant; turbines. DAIMLER-BENZ A.G. Sept. 18, 1968, No. 44293/68. Headings F1G and F1T. In a gas turbine engine having a gas turbine type gas generator section and a separate power turbine, the nozzle guide blades of the power turbine are angularly adjustable automatically in response to gas generator speed by control pressures produced by a hydraulic apparatus connected to the fuel supply system of the engine. In one embodiment, the fuel supply system comprises pumps 12, 13 feeding injection nozzles 27 through a fuel regulator 14, a pipe 21 branching off from a portion 11<SP>1</SP> of the fuel supply pipe to feed fuel to a control circuit ST for the guide blades 31 of the power turbine 32. A valve 15 in the control circuit maintains the fuel pressure in pipe ST<SP>1</SP> upstream of a restriction 22 constant regardless of pressure fluctuations in the main fuel supply. The pressure in pipe ST<SP>11</SP> downstream of restriction 22 acts on an evacuated capsule 42 within a chamber 43, the capsule 42 positioning the slide 37 of a servovalve 33 to control the flow of operating oil to a piston 36 connected through a link 51, unison ring 52 and adjusting levers 53 to the guide blades 31. Opposite sides of a diaphragm 18 are connected to the inlet and outlet respectively of the gas generator driven centrifugal fuel pump 12 so that the diaphragm 18 is positioned as a function of gas generator speed. The diaphragm 18 adjusts a paraboloid needle 17 controlling the return of fuel from the control circuit ST to the inlet of pump 12, and thus the control pressure in pipe ST<SP>11</SP> and the position of the guide blades 31. The control circuit ST includes a by-pass N around the restriction 22, the by-pass being closed during steady running by a slidable valve member 23 attached to a diaphragm 25. The latter is subjected on one side 24<SP>1</SP> through pipe 26 to the fuel pressure adjacent nozzles 27 and on the other side 24<SP>11</SP> to the pressure on one side of a spring- loaded piston 30<SP>111</SP> controlling a throttling slot 30<SP>11</SP> in the fuel supply line. When an increased fuel flow is selected to accelerate the engine, the differential pressure across slot 30<SP>11</SP> increases so that piston 30<SP>111</SP> moves to the right thus increasing the pressure on side 24<SP>11</SP> of diaphragm 25 and causing the diaphragm 25 and valve member 23 to move to the left to open by-pass N around restriction 22. Thus the control pressure in pipe ST<SP>11</SP> increases to such an extent that guide blades 31 are temporarily moved to their fully open position B. In the meantime the increased pressure on side 24<SP>11</SP> of diaphragm 25 is gradually reduced by the effect of a restriction 29 so that valve member 23 returns to its closed position to shutoff by-pass N. The diaphragm 18 adjusts needle 17 so that the setting of the guide blades 31 now corresponds to the increased rotational speed of the gas generator. When braking of the vehicle in which the engine may be mounted is required, lever 48 is pivoted in the direction shown to move a piston in a cylinder 47 to the left thus pivoting a follow up lever 41. The latter moves a ported sleeve 40 surrounding slide 37 of servovalve 33 to the right so that valve 33 supplies operating oil to move piston 36 to the right and blades 31 into their braking position D. In a modification. Fig. 2 (not shown), needle 17 is controlled by a centrifugal governor (49) responsive to gas generator speed instead of diaphragm 18, whilst in a further modification, Fig. 3 (not shown) the needle 17 is replaced by a tubular slide (50) having a control slot (50<SP>1</SP>).