Patent GB-720267-A (GB)
Title: An improved control and ignition system for liquid fuel combustion apparatus
Inventor: TROWBRIDGE DAVID ROY
IPC: F02C7/26
Filed: 1951-04-19
Abstract: 720,267. Gas turbine plant. PLESSEY CO., Ltd. April 18, 1952 [April 19, 1951], No. 9139/51. Class 110 (3). [Also in Group XI] In a control and ignition system for liquid fuel combustion apparatus an electrical circuit operates a time switch unit which in turn actuates an electro-mechanical fuel supply means to inject fuel into a combustion chamber, and the rise in fuel pressure due to fuel being forced through atomizers causes a flow or lowpressure switch to energize an ignition unit, and a high-pressure switch closes when the fuel pressure rises still further due to a rise in combustion chamber pressure on ignition and in association with the time switch serves as a safety device whereby in the event of failure of the ignition unit to ignite the fuel said highpressure switch does not close and the time switch de-energizes the electro-mechanical fuel supply means. The Figure illustrates a liquid fuel control and ignition system for the starter of a gas turbine. On closing a push-button switch 20 current passes from the positive line of a 24 v. supply to the negative line through contacts 4a of a time switch 21 and contacts E1 to energize the coil 22 of a slug relay 23. The driving motor of the time switch is also energized through contacts D1 and closes first the contacts 1a. Contacts 24 close on energization of the coil 22 and current flows through a control switch 25, contacts 24, 3a, 1a, and an electrically-operated fuel pump 26 and air blower 27 driven in tandem. The pump 26 circulates liquid fuel from a tank 28 through a pipe 28a and solenoid valve 29 back to the tank 28, and the blower 27 supplies air to a combustion chamber 32 through a pipe 30 containing a non-return valve 31. Contacts 2a are next closed to energize the solenoid valve 29 so that fuel is diverted through a pipe 33, constant flow valve 34, spring-loaded piston valve 35, and non-return valve 36 to the combustion chamber 32 and excess liquid is spilled back to the tank 28 through pipe 37. The valve 35 is moved by the flow of fuel to break contacts E1and close contacts Fl so that an ignition unit 38 is ener. gized through contacts 4a, F1. The slug relay 23 is de-energized when the contacts E1 break and opens contacts 24 after a delay sufficient to allow an alternative circuit to be established for the pump 26 and solenoid valve 2a by the closing of a fuel pressure responsive switch 39 when combustion occurs in the chamber 32 to increase the pressure in the pipe 33. The non-return valve 31 will also close and the air supplied by the blower exhausted to the atmosphere through a valve 40 opened by the increased fuel pressure. In the event of failure of the unit 38 to ignite the fuel the switch 39 will remain open and the opening of the contacts 24 will de-energize the fuel pump 27 and the solenoid valve 29. During the continued operation of the time switch 21 contacts 3a are opened to ensure that the circuit through the contacts 24 is broken in the event of failure of the latter to open. Contacts 4a subsequently open to de-energize the ignition unit after a period sufficient for igniting the fuel. The system is closed down by the opening of the control switch 25 when the engine has reached a pre-set speed. An alternative system is described in which two relays are energized one after the other by the closing of a push-button switch, and when the switch is re-opened one relay is de-energized and the other allows passage of current to the time switch controlling the fuel supply means and the ignition unit.