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NORA Oilheat Technicians Manual

Figure 1-3: Flame retention burners Although the high-pressure burner has been the mainstay of the industry almost from the beginning of the modern oilburner era, it has gone through many modifications. An advantage of oil is that parts are largely interchangeable, and thus it has been possible to keep many burners operating for years. In fact, some burners made in the 1930s are still operating in the field because of interchangeable parts. Flame retention oilburners In the 1960s, the current design for oilburners was introduced, which is called the flame retention burner. As the name implies, the flame is held very close to the face of the combustion head. The flame is smaller and more compact than with older burners. This design’s primary characteristics are its head or end-cone, high motor operating speeds (typically 3450 RPM) and high combustion air static pressures. Figure 1-3 shows pictures of modern flame retention burners. 1-4 Introduction to Oil Burners The flame retention head provides a modified airflow pattern for radically improved air-oil mixing. The basic idea is to produce a strongly swirling air pattern that recirculates combustion products for more complete mixing of fuel and air. This is called recirculation. As the air rushes out of the end of the burner, it sucks air from the combustion Nozzle area back toward it. This recirculation is what pulls the fire back toward the head, creating the flame retention effect. The flame stabilizes near the burner head, hence the name flame retention. The air swirling is achieved with airflow shaping heads and turbulators and by running the burner motor and fan at high speed. The flame retention head produces more air swirl and combustion air recirculation flow, which improves fuel-air mixing. This permits operation with less excess air and with lower smoke levels. Cleaner and more stable combustion is produced and system efficiency is typically 5 to 15 percent Chapter 1 Intro to Oil Burners Air Pattern—Non-Flame Retention Burner Air Pattern—Flame Retention Burner RecirculationArea 0-25 Velocity Nozzle


NORA Oilheat Technicians Manual
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