Patent GB-709021-A (GB)
Abstract: 709,021. Fluid-pressure servomotor-control systems. BAILEY METERS & CONTROLS, Ltd. Aug. 3, 1951 [Aug. 5, 1950], No. 18384/51. Class 135. [Also in Group XI] In a liquid fuel burning system having one or more mechanical atomizing liquid fuel burners 10 of the kind having a whirl chamber to which fuel is supplied through tangential passages from a fuel supply conduit 11 and from which fuel not discharged through an axial orifice for combustion is returned through a passage to a fuel return conduit 12, automatically operated valve means responsive to the pressures in the supply and return conduits 11, 12 are provided to maintain between these pressures a differential which decreases as the burner output decreases. Conveniently the pressure differential is regulated by hand or in accordance with some load or demand factor such as steam pressure, steam flow or temperature. Fig. 4 shows a vapour generator the burners 10 of which are controlled by diaphragm-operated valves 35, 36 in the supply and return conduits 11, 12 respectively. Air is supplied to the furnace by a blower 30 through a passage 31 controlled by a damper 44. The blower is driven by a power unit such as the turbine 40 the motive fiuid supply to which is regulated by a diaphragm-operated valve 42. The damper 44 is operated by a control mechanism 46. The valve 36 is controlled in accordance with the pressure in the steam drum 32 and the ratio between the total air flow and the fuel actually supplied to the burners. Pressure in the steam delivery pipe 33 acts through a pipe 51 on a Bourdon tube 50 adapted to operate a pilot valve 52 as described in Specification 425,507, [Group XII]. The valve 52 controls the supply of pressure fluid to a chamber 53 of a relay 54 as described in Specification 461,389 and comprising also pressure chambers 60, 62 having a restricted connection, a loading spring 56, and lever-interconnected inlet and exhaust valves 58, 59 operated by a member 55. The control pressure produced by the relay is led through a pipe 65 to a further relay 69 and also through pipes 66, 67 to operate the blower turbine control valve 42 and the control mechanism 46 of the damper 44 in the sense of opening the valve 42 and the damper 44 on a fall of steam pressure. The relay 69 is controlled also by a relay 100 itself controlled, according to the ratio of the air supply to fuel supply to the burners. The relay 100 has a diaphragm 102 responsive to a pressure generated by a control device 112 subject to the pressure difference across a restricted orifice 109 in the air supply passage 31. The relay 100 also has a diaphragm 101 responsive a pressure generated by a control device 107 in accordance with the difference in the fuel flows in the conduits 11, 12 as measured by flow responsive devices 105, 106 as described in U.S.A. Specification 2,459,689. The diaphragms 101, 102 act through levers with an adjustable leverage on a pilot valve 104 controlling the pressure applied to a chamber 116 of the relay 69. The control pressure produced by the relay 69 is supplied through pipes 70, 71 to operate the valve 36 in the return conduit and also through a pipe 72 to the chamber 73 of a further relay 74. This relay controls the valve 35 in the supply conduit 11 and is also controlled by a relay 80 similar to the relay 100 responsive to the pressures in the conduits 11, 12. These pressures act through pipes 83, 84 on bellows 81, 82. The bellows 81, 82 act through levers 85, 86 and an adjustable roller 87 to control a pilot valve 89 controlling the admission of fluid to the chamber 93 of the relay 74. The valve 35 only is thus controlled according to fuel pressures in the conduits 11, 12. The Specification also describes similar forms in which the fuel pressures in the conduits 11, 12 act directly on the actuating diaphragms of the valves (see Group XI). Specification 696,072, [Group XI], also is referred to.