GB1090494A - Improvements in viscosity flow control means - Google Patents

Abstract

1,090,494. Gas turbine engines. GENERAL ELECTRIC CO. March 17, 1966, No. 11710/66. Heading F1G. [Also in Division F2] To ensure the supply to a gas turbine engine of a sufficient amount of atomized fuel, particularly at starting, the reduction of the percentage of fuel which atomizes properly, normally occurring as the fuel viscosity increases, is compensated for by increasing the rate of fuel delivery to the engine as the viscosity increases. A viscosity-sensitive control 82, Fig. 4, for this purpose is connected in parallel with the main fuel metering valve and comprises a passageway through which laminar flow of fuel occurs. The pressure drop along the passageway, which is proportional to the product of the fuel viscosity and the rate of flow through the duct, is used to control the supply of fuel. The passageway may be straight but preferably comprises a helical tube 122, the pressure drop across the helical tube being applied to the opposite sides of a bellows 110 carrying a needle valve 116 co-operating with a thin plate orifice 118. The initial position of the needle valve 116 relative to the orifice 118 is adjustable by a nut 130. Fuel delivered by a pump to an inlet 96 flows through the orifice 118 and thence through the helical tube 122 to an outlet 98 leading to the burner nozzles. Any increase in fuel viscosity produces a proportionate increase in the pressure drop through the helical tube 122, causing the bellows 110 to move the needle valve 116 to the right to reduce the pressure drop through the orifice 118, thereby increasing the fuel flow. The viscosity-sensitive control 82 may be used to provide the entire supply of fuel at starting or may supplement the minimum flow provided by the main fuel metering valve of the engine. Preferably, a constant pressure drop is maintained either across the orifice 118 or across the entire control 82 by means of a pressure drop regulator of known type. In an alternative arrangement, the laminar-flow passageway (148), Fig. 5 (not shown) is connected in series with a sharp-edged orifice (152) of fixed area, the combination being connected in parallel with a sharpedged orifice (142) which is adjustable by a needle valve (144) carried by a bellows (146) subjected to the pressure drop through the passageway (148).