Document 9kdR58ZDgzOaz5mdX4pv1RE6

390 CHAPTER 15 1957 Guide installations. The heat output is in the range of requirements for the average or small home. . The modulating flame allows simple manual control by regulation of a metering valve, and simplifies the control equipment. Quiet combustion and the absence of moving parts contribute to quiet operation when the heating device is located in the living quarters. The ability to operate on natural draft and gravity feed of the fuel, makes 'possible the use of these burners where electric current is not available or is unreliable. However, most furnaces are thermostatically controlled, and many are provided with mechanical draft. Oil-Fired Boiler and Furnace Units A number of types of specially designed oil-fired boiler-burner and furnace-burner units are available. Various locations of burners will be noted in such units; some having the combustion chamber and burner Automatic Fuel Burning Equipment 391 A vaporizing burner prepares the oil for combustion by transforming the liquid fuel to the gaseous state by the application of heat. In an atomizing burner, the oil is mechanically separated into very fine particles so that the surface exposure of the liquid to the radiant heat of the combustion chamber is vastly increased and vaporization thereby promoted. The result is the ability to bum more and heavier oil within a given combustion space. Because the air enters the combustion chamber with the liquid fuel particles, mixing, vaporization and burning occur all at once in the same space. This produces a luminous flame. A deficient amount of air is indicated by a dull red or dark orange flame with smoky tips. An excessive supply of air may produce a brilliant white flame or a -short ragged flame with incandescent sparks flashing through the com bustion space. While extreme cases may be detected, it is not possible Fig. 16. Vaporizing Gravity Pot-Type Burner at the top, some at the bottom, and some at the center of the appliance. Typical combination units are shown in Figs. 17 and 18. The coordinated design of boiler (or furnace) and burner elements insures the optimum m operating characteristics, and the maintenance of balanced performance. This type of equipment usually has more heating surface, and better flue proportions and gas travel than conventional boilers or furnaces. Some of the better conversion installations, however, may equal the emit type m performance. Operating Requirements for Oil Burners The U. S. Department of Commerce, in conjunction with the oil burner and heating appliance industries, has established commercial standards for con- version burners and burner-appliance units-which cover installation, con struction and performance tests.4 '; ` Combustion Process ! Efficient combustion must produce a clean flame and use a relatively small excess of air, i.e., between 25 and 50 percent. This can be don only by vaporizing the oil quickly and completely, and mixing it vigorously with air in a combustion chamber hot enough to support the combustion- to distinguish, by eye, the effect of the finer adjustment which competent installation requires. Combustion Adjustments "fh present-day oil burner with mechanical oil and air supply, properly installed and equipped with an automatic draft regulator, is capable of maintaining efficient combustion for a considerable period following the j1* adjustments of oil and air. Eventually, certain changes will occur, ,. "ay be such that the amount of excess air will decrease below allowote mints. A decrease 111 air supply while the oil delivery remains con<ant, or an increase in oil delivery while the air supply remains constant, nTMP5. the mixture of oil and air too rich for clean combustion. The surJiu eTM0lent the adjustment, the more critical it will be. The oil and air PP*y rates must remain constant. in^.e following factors may influence the oil delivery rate: (1) changes deliv _T)fcos'ty due to temperature change or variations in grade of oil Press, ^ eros'on f atomizing nozzle; (3) fluctuations in by-pass relief chan ant* (4) possible variations in methods of atomization. Amy ge due to partial stoppage of oil delivery will increase the proportion