Patent GB-737996-A (GB)
Title: Fuel control for gas turbine engines
Inventor: HALL WALDO JENNINGS
IPC: F02C9/16
Filed: 1950-10-31
Abstract: 737,996. Gas turbine plant. BENDIX AVIATION CORPORATION. Oct. 31, 1950, No. 26595/50. Class 110 (3). [Also in Group XXIX] A fuel feeding system for a gas turbine engine comprises a feed conduit with a restriction therein, means for generating in a chamber upstream of said restriction a force as a function of engine speed, means for regulating the head of fuel across the restriction, and a device having a pressure connection with said chamber to modify the action of the regulating means in response to variations in pressure in said chamber. The system maintains a linear relation between engine speed and fuel flow within upper and lower limits during acceleration and deceleration of the engine and the device which modifies the regulating means causes an increase in the rate of fuel feed at the upper ends 91-89 and 93-94, Fig. 3, of the acceleration and deceleration curves. The curve 86 indicates the fuel feed required for steady speed. In the system described, fuel is delivered from a conduit 20<SP>1</SP> and passes through a ported piston valve 18 which, with a spring-loaded diaphragm 17 and a lever connection 52 with engine-driven governor weights 50, regulates the pressure drop across a throttle valve which comprises a sleeve 31 ported at 34 and acted upon by enginedriven governor weights 47 and a manually adjustable spring 40. Metered fuel from the throttle valve is discharged through a cut-off valve 36 to a delivery conduit 37. A relief valve 23 is controlled by a diaphragm subject to the supply and metered fuel pressures to maintain a predetermined differential between these pressures. The diaphragm 17 is exposed to the pressure in a chamber 15<SP>1</SP> upstream of the throttle valve and, through passages 63, 64, 65, to the pressure downstream of the throttle valve, and since the pressure differential acting on the diaphragm must balance the force of the centrifugal governor weights 50, the valve 18 maintains the pressure difference across the throttle valve in proportion to the square of the engine speed. For a given opening of the throttle valve, the fuel flow is therefore substantially proportional to engine speed. Orifices 62 permit a leakage across the diaphragm and a needle valve 60 controls a restriction 61 in accordance with air density as detected by a bellows 69. The device for modifying the action of the regulating valve 18 comprises a spring-loaded ball 75, or a needle valve, which opens in response to increasing pressure in the chamber 15<SP>1</SP> to increase the pressure on the left-hand side of the diaphragm. The governor weights 47, 50 due to their rotation, increase the pressure applied to the valve 75 over that obtaining generally in the chamber 15<SP>1</SP>. In operation, the throttle valve 31 and the governor weights 47 serve as a speed governor, but in the event of a change in the setting of the spring 40, say to increase speed, the throttle valve is opened and the valve 18 opens to maintain the pressure differential. At a certain speed the valve 75 opens to increase the pressure difference across the throttle valve and the fuel feed follows the line 91-89 until the required speed is reached, when the governor 31, 47 again takes control. In decelerating, the fuel flow initially follows the lines 89<SP>1</SP>-93 due to the partial closure of the throttle valve, and then passes to the point 94 at which the valve 75 closes. Thereafter the fuel flow follows the line 94-92. Reference has been directed by the Comptroller to Specification 655,311.