GB687421A - Improvements in or relating to operation of jet engines - Google Patents

Abstract

687,421. Electric control systems. STANDARD OIL DEVELOPMENT CO. March 22, 1950 [June 16, 1949], No. 7187/50. Class 40 (i). The invention relates to means for anticipating and preventing flame-blow-out in jet engines, and is based on the fact that at flame-blow-out the ratio P/F of the absolute pressure P in the combustor to the air inflow weight F is linearly related to the temperature difference At between the air intake and that of the combustion gases as shown in Fig. 6 for two fuels A, B when used in a particular engine. The engine operator has a flame-blow-out indicator, Fig. 9, comprising two pointers 69, 74 of instruments which measure respectively P/F and #t. The two pointers move about centre O, 0', respectively, over a dial having curves such as 81, 82 graduated thereon corresponding to flame-blow-out conditions and determined empirically for the fuels A, B in question. Since the region of sustained flame lies to the right of the fuel curves, the engine operator has merely to ensure that the intersecting point of the two pointers 69, 74 always lies to the right of the appropriate fuel curve. Preferably the air weight inflow is measured by a thermal meter 80, Fig. 7, in which an electric heater H is supplied by a wattmeter 66 and is adjusted automatically to maintain a predetermined temperature difference between resistors T3, T4 located in the air inffow on opposite sides of the heater. The absolute pressure P is preferably measured by a bellows-type gauge 90. The pointers 64, 65, of the pressure and air flow weight meters control through variable resistors 63, 62 the current flow in the coils 67, 68 of a ratio meter the pointer 69 of which indicates the ratio P/F. A sensitivity adjustment, Fig. 8 (not shown), may be provided for the ratio meters. The temperature difference #t is preferably measured e.g. by thermocouples T<SP>1</SP>, T<SP>2</SP> arranged in series in a meter circuit 72, which if necessary through an amplifier, actuates the pointer 74. Automatic means may be provided for sustaining the flame e.g. with a fixed weight airflow and combustor pressure, the fuel supply may be controlled to raise #t so as to keep away from incipient blow-out regions of operation.