Patent GB-170683-A (GB)
Title: Improvements in the regulation of combustion conditions in furnaces
IPC: F23N1/02
Filed: 1920-07-29
Abstract: 170,683. Hopwood, J. M. July 29, 1920. Liquid and gaseous fuel furnaces.-The feed of fluid fuel to a steam - generator furnace is controlled by changes in the rate of flow of steam from the generator, or by the steam pressure, or by both combined; whilst the supply of air for combustion is regulated in accordance with the feed of fuel. In the gasfired furnace shown in Fig. 1, a control mechanism preferably of the kind described in Specification 141,137 is employed for the gas supply. This embodies a diaphragm indicated at 5 subjected on its upper side to the total pressure in the steam-pipe C, the chamber above the diaphragm being connected by a pipe 3 to a Pitot tube or its equivalent arranged in the pipe C. A chamber intermediate the diaphragm 5 and a second diaphragm 6 is connected to the conduit C or to the generator. so that the static steam pressure is maintained in it. The underside of the diaphragm 6 is subjected to a pressure substantially equal to that to be maintained in the generator. The diaphragms 5, 6 are connected as described in the above-mentioned prior Specification to a pilot valve controlling the flow of pressure fluid to a cylinder 28, the movement of the piston of which controls the gas supply valve 2. The arrangement is such that an increase in static pressure, and a decrease in the rate of flow of the steam will effect a closing movement of. the valve 2 and vice versa. The valve 11 controlling the air supply is controlled by a mechanism comprising cups 13, 14 at opposite ends of a lever 15 and immersed in liquid. A nozzle 16 connected to the gas-supply pipe 1 keeps the interior of the cup 13 at a pressure equal to that of the gas in the pipe 1. The resulting movement of the lever controls the valve of a fluid-pressure cylinder 18, the piston of which operates the valve 11. A similar mechanism operates the damper 21 controlling the discharge of gases in accordance with the pressure in the furnace, a nozzle 16<a> under a suspended bell being connected by a pipe 22 to the interior of the furnace. Fig. 3 shows the pressure cylinder 28 for operating the gas valve together with means for controlling it in accordance with the static steam-pressure. A diaphragm 29<a> is subjected above to the static pressure in the steam-pipe C. and below to a fluid-pressure equal to the normal steam-pressure desired. The latter pressure is maintained by air trapped in a cup 35 inverted in liquid contained in a chamber 30 communicating with the underside of the diaphragm, and is originally established by opening a valve in a passage connecting the chambers above and below the diaphragm when the boiler pressure is normal, the valve being then closed. The movements of the diaphragm 29<a> are transmitted by a lever 38 to a pivotally-mounted beam 39. A bell-crank lever 40 pivotally mounted on this beam has one arm connected to the valve 41 of the pressurecylinder 28, whilst the other arm is connected by a link 42 to a pivotally-mounted standard 43. On movement of the beam 39 by the diaphragm the bell-crank lever 40 operates the valve 41, thereby causing movement of the piston and the frame 29 attached thereto. This frame carries an inclined bar 46 which slides along a shoe pivotally mounted at the upper end of the standard 43, which is thus rocked and through the link 42 operates the bell-crank lever 40 to close the valve 41. In this way a definite change in pressure is made to correspond to a definite movement of the frame 29 and of the gas-valve to which it is connected. When liquid fuel is employed, the airsupply control mechanism shown in Fig. 1 may be replaced by one similar to that shown in Fig. 3, the pressure in the oil-supply pipe entering above the diaphragm 29a whilst the normal pressure m the pipe is established beneath it.