Document oDmenBqwZ0mGebO7YgLEEgw5E

326. CHAPTER 17 1946 .Guide operate with luminous or non-luminous flame. Operation may be inter- mittent, continuous with high-low flame, or continuous with graduated flame. CLASSIFICATION OFBURNERS Domestic oil burners may be classified by type of design or operation into the following groups: pressure atomizing or gun, rotary, and vapor izing or pot. These are further classified as mechanical draft, and natural draft. Pressure Atomizing (Gun Type) Gun type burners may be divided into two classes, low-pressure, and high-pressure atomization. In the first group, a mixture of oil and primary air is pumped as a spray through the nozzle at a pressure of 2 to 7 lb per square inch. Secondary air is supplied by a fan. Ignition is obtained by means of a high-voltage electric spark used alone, or as primary ignition for a gas pilot. Various features of a low pressure atomizing burner are shown in Fig. 12. Automatic Fuel Burning Equipment 327 Rotary Type This class of burners may be divided into two groups: vertical, and horizontal. Most of the smaller rotary burners are of the vertical type, and use the lighter distillate oils, No. 1 or 2 grade. The most distinguishing feature of vertical rotary burners is, the principle of .flame application. ` These burners are of two general types: the center flame and wall flame. In the former type (Fig. 14), the oil is atomized by being thrown from the rim of a revolving disc or cup and the flame burns in suspension with a characteristic yellow color. Combustion is supported by means of a bowl-shaped chamber or hearth. The wall flame burner (Fig. 15) differs in that combustion takes place in a ring of stainless steel or refractory material, which is placed around the hearth. Dependent upon combustion adjustment, these burners may operate with either a semi-luminous or non-luminous flame. ' Both types of vertical rotary burners are further characterized by their installation within the ash pit of the boiler or furnace. Various types of Fig. 13. High-Pressure Atomizing Oil Burner The high-pressure atomizing type, illustrated in Fig. 13, is characterized by an air tube, usually horizontal, with oil supply pipe centrally located in the tube and arranged so that a spray of atomized oil is introduced, ' at about 100 lb per square inch, and mixed in the combustion chamber with the air stream emerging from the air tube. A variety of patented shapes is employed at the end of the air tube to influence the direction and speed of the air and thus the effectiveness of the mixing process. This type of burner utilizes a fan to supply the air for combustion, and ignition, is established by a high-voltage electric spark that may be operative continuously while the burner is running, or just at the beginning of the running period. Gun type burners operate on the intermittent on-off principle, and with a luminous flame. The combustion process is completed in a chamber constructed .of refraictoiy material, or stainless steel, this being a part of the installation. Pressure-atomizing burners generally use the distillate oils,' No. 1) 2 or 3 grade. '(See Chapter 16.) - ' ' Fig. 14. Center Flame Vertical Rotary Burner Fig. 15. Wall Flame Vertical Rotary Burner ignition are utilized, gas and electric, either spark or hot wire. The air for combustion is supplied partially by natural draft, and partially by fan effect of the central spinner element. Horizontal rotary burners are used principally to burn the heavier oils, Nos. 5-and 6 grades, principally ip larger commercial and industrial installations, although domestic sizes are available. Such burners are of the mechanical atomizing type, using rotating cups which throw the oil from, the edge of the cup at high velocity into the surrounding stream, of air delivered by the blower (Fig. 16). Horizontal rotary burners commonly use a combination electric-gas ignition system, or are lighted manually. Primary air for combustion is supplied by a blower, and secondary air, often introduced through a checkerwork in the combustion chamber, is controlled by chimney draft. These burners operate with a luminous flame,, usually on high-low or continuous setting. . In larger installations, burners may be installed in multiple in a common combustion chamber. Because of the high viscosity oils used in these