GB686747A - Improvements in or relating to spark type ignition systems for combustion engines - Google Patents

Abstract

686,747. Ignition systems. ROLLS-ROYCE, Ltd. Jan. 4, 1950 [Jan. 4, 1949; March 11, 1949] Nos. 238/49 and 6797/49. Class 7 (iv). A spark type ignition system for initiating combustion in a gas turbine engine comprises a sparking circuit including the electrodes of a spark plug and, continuously in series therewith, an accumulator condenser of large capacitance capable of being charged to a potential sufficient to cause break down of the sparking gap, and a charging circuit through which the condenser is charged step-by-step to said potential by a succession of high potential impulses, including a rectifier device to prevent discharge of the condenser through the charging circuit. In an ignition system suitable for operation by a 24 volt battery of an aircraft, the battery 11, Fig. 1 energizes an induction coil 10 to produce unidirectional pulses in its secondary winding 10b for charging a small capacity condenser 13 through a diode rectifier valve 14. The condenser discharges in the intervals between said pulses through a resistance 15 to charge an accumulator condenser 16 until the latter attains a potential sufficient to energize the spark ignition gap 17 through a discharging circuit comprising a choke 19. The small capacity condenser 13 and the resistance 15 may be omitted. the diode valve or a metal rectifier being connected to supply the successive charging pulses to the condenser 16. The choke 19 may be replaced by a sealed control spark gap, or the spark gap 17 may be connected directly across the condenser 16. Specifications 644,347, 663,527 and 663,528 are referred to.