Patent GB-283903-A (GB)
Title: Improvements in and relating to furnace regulation
IPC: F23N1/02
Filed: 1928-01-19
Abstract: 283,903. British Thomson-Houston Co., Ltd., (Assignees of Smith, A. R.). Jan. 19, 1927, [Convention date]. Regulating combustion. - In a plant for the generation of elastic fluid such as steam, of the kind described in Specification 264,852, in which electric currents which are measures of the fuel and air supplied are utilized to operate a balanced relay to vary the supply of fuel and air to the furnace in accordance, with the steam pressure, the operation of the balanced relay is modified so as to vary the ratio of fuel to air in accordance with the load on the furnace. The furnace 1 generates steam in the boiler 2 discharging through a conduit 23 into a main 24 common to a group of boilers. The fuel feeder 3 is driven by an electric motor 4 and the draught is produced by a suction blower 14 in the waste gas conduit 13 and) driven by an electric motor 15. In the event of a decrease in the demand for steam the pressure in the main 24 increases and operates an electric pressure gauge 67 and causes a flow of current from the supply lines 5, 6 to the coil 70 of the master relay 71 common to all the furnaces. The movable contact 73 of the relay engages with fixed contact 75 and completes the circuit between the mains 5, 6 and the field winding 80 of the motor 12. The latter is moved in a direction to vary the resistance 10 in the field 9 of the motor 4 so as to decrease the fuel supply to the furnace. A reduction in the speed of the stoker effects a, reduction of pressure in a device connected with the electric coal meter 44 which may be of the type described in Specification 214,632, [Class 106 (ii), Dynamometers &c.]. The circuit of the meter includes a coil 51 of the balanced relay 42 and upon a reduction in the fuel supply a decreased flow of current passes from the mains 5. 6 through the, coil 51 and unbalances the relay 42, causing the contact 53 to engage the contact 55 and complete the circuit from the mains 5, 6 through the field wind. ing 58 of motor 21. The latter is operated to reduce the speed of the motor 15 and the air supplied to the furnace. The reduction of the fuel and air supplies effects a reduction in steam pressure in the main 24 and the relay contact 73 is returned to its normal position. An electric flow meter 25 of the type described in Specification 241,201, [Class 106 (ii), Dynamometers &c.], is connected to the air supply conduit 31 of the furnace. With a reduction in the air supply the bell 27 of the meter operates armature 36 so as to reduce the current in the winding 38 connected to the coil 41 of the balanced relay and to the mains 5, 6. The coil 41 is wound oppositely to the coil 51 and the reduction of the current in the coil 41 restores the relay contact 53 to its normal position. In order to increase the ratio of air to fuel with increase in boiler load. the balanced relay 42 is provided with a coil 92 connected to a flow meter 87 in connection with the steam conduit 23. The coil 92 is opposed to the coil 41 so that with an increased flow of steam an increased supply of air for the same fuel supply will be necessary to balance the relay.