Patent GB-717340-A (GB)
Title: Liquid or gaseous fuel burner apparatus
IPC: F23D17/00
Filed: 1951-12-31
Abstract: 717,340. Liquid or gaseous fuel burners. ORR & SEMBOWER, Inc. Dec. 31, 1951, [June 29, 1951.] No. 30435/51. Class 75 (1). A liquid or gaseous fuel burner having an air guide for controlling the air supply to a furnace combustion zone comprises an air chamber 10 into which air is delivered tangentially and then divided into primary and secondary air streams which are directed through concentric orifices of such a size that an exit velocity of 140-200 feet per second is imparted to the air at the maximum burner load. The air is supplied under pressure tangentially to the chamber 10 from a duct 16 through a throttle valve opening 24 at a velocity of approximately 65 feet per second. The air supplied to the chamber 10 is divided into two streams, one stream, approximately 40-55 per cent of the total weight of the air supplied, passes between guide vanes 82 of a stationary air compressor 81 and through holes 80 in a tube 64 to be discharged at 140-200 feet per second as primary air through a ring 76, whilst the balance forms the secondary air and passes at 140-200 feet per second through an annular orifice formed between a ring 77 and an orifice 18 in the chamber 10. The aggregate cross-sectional area of the holes 80 is 50-75 per cent greater than the opening through the ring 76. The inner surface 34 of the valve member 30 is streamline to prevent turbulence in the passing air stream and the shaft 40, on which the valve member 30 is mounted, is operated by a suitable linkage (not shown) which also controls the quantity of fuel delivered to the burner. An adjustable stop 48 limits the member 30 movement in one direction and a shoulder 46 in the other. When the burner is used with gas the liquid fuel injector assembly 96 is removed or the fuel supply cut off, and gas is passed from a duct 52 to the combustion zone 12 through a nozzle 70 secured within the tube 64. The internal surface 72 of the nozzle 70 converges towards the zone 12 and its internal crosssectional area is preferably 55 to 80 per cent of the cross-sectional orifice area of the ring 74 and is proportioned so that the exit velocity of the gas passing therethrough is between 29-60 feet per second at maximum burner load. The external surface 94 of the nozzle 70 is smooth and converges towards the zone 12. The nozzle 70 extends beyond the holes 80 and is of such a size externally that the primary air velocity towards the ring 76 is approximately 105 feet per second. The effective annular primary air metering area defined between the surface 94 and the tube 64 is preferably 33 to 50 per cent greater than the orifice area of the ring 76. The internal cross-sectional area of the tube 64 is preferably 50 to 75 per cent greater than the orifice area of the ring 76. When the burner is used with liquid fuel the gas duct 50 is removed or the gas supply cut off, and the fuel is passed to an atomizing nozzle 102 through a duct 114 and 100 and atomizing fluid through a duct 116 and an annular passage formed between the duct 100 and a duct 98. The fuel passes through a number of passages 135 into a number of slots 134 where it is atomized by the fluid passing therethrough. The mixture of oil and fluid is directed tangentially in a number of streams into a chamber 142 and then to the combustion zone 12 through an orifice 141 at an exit velocity of from 325 to 400 feet per second. The head 127 of the nozzle cone 120 is cut back to form a conical surface 136 and the slots 134 decrease in cross-sectional area from their entrance to the point of intersection with the passages 135, so that the velocity of the fluid at the point of intermix is within the range of from 650 to 800 feet per second. The fuel to fluid weight ratio is 1 : 0.2 at maximum burner rating the minimum practical ratio being 1 : 0.18. The ratio of the area of the slots 134 at the point of intermix to the orifice 141 is between the ratios of 1 : 1.65 to 1 : 2.3. To prevent coking of the liquid fuel in the slots 134 and passages 135 the duct 98 is formed of high thermal conductivity material brass or aluminium, the body member 122 of high thermal conductivity material beryllium copper, and the core 120 and cap 121 of low thermal conductivity material stainless steel. A stop 150 is soldered in the end of the duct 100 to prevent fuel leaking into the nozzle core 120 and the passages 135 after the burner has ceased to operate. The stop 150, which consists of two segments 152, 154 joined by a cylindrical portion 156 is soldered into the duct 100 with the chordal surfaces 158, 160 horizontal.