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NORA Oilheat Technicians Manual

Chapter 5 Nozzles and Chambers Figure 5-8 Proper Spray Angle Matched to Air Flow Figure 5-9 Fuel Spray Angle too Wide Fuel Spray Angle too Narrow 5-10 Nozzles and Combustion Chambers Nozzle Nozzle Inches Inches Inches Inches Inches Inches Nozzle and excessive heat are the main causes of nozzle failure. Contamination can be limited by installing a good oil filter in the supply line. If there are excessive tank bottom sediments in the tank, you may need to clean the tank and adopt a fuel additive program. For severe cases, replace the tank. Nozzles should not be very hot when operating because of the amount of air and fuel traveling past them. Nozzles overheat from poor or no over-fire draft. Over-fire draft should be at least -.01" to keep nozzles cool. There are some exceptions to this rule. As usual, manufacturer’s instructions take precedence. Be sure the end of the burner air tube does not extend into the chamber. The face of the end tube should be flush with the face of the chamber, or recessed about one quarter inch. Air-oil mixing and flame patterns What constitutes a perfect oilburner flame? Theoretically, each droplet of oil that leaves the nozzle orifice should be completely surrounded by air. It should be vaporized and then burst into flame— totally burning all the hydrogen and carbon atoms in the fuel. This air volume, generated by the burner fan, and, in most applications, aided by the draft-over-thefire, should be adjusted to deliver the exact amount of air required by the fuel being fed through the nozzle, see Figure 5-8. It is impossible to reach this perfect state in the field, but it is a good target to shoot for. The closer you come to this perfect air-oil match, the cleaner, quieter, more efficient and odor free the flame will be. There are six elements for the perfect air-oil match. They are: air volume, oil volume, oil pressure, oil spray pattern, oil spray angle, and the air pattern of the burner. The air pattern of the burner is the


NORA Oilheat Technicians Manual
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