Oil boiler

An oil boiler comprising:

• an outer container having openings at opposite ends thereof and an empty space therein;
• a combustion chamber configured to cover an opening at an upper end of the outer container, the combustion chamber being located in the empty space of the outer container and having an interior space in which a combustion reaction occurs;
• a lower cover spaced apart downward from the combustion chamber and configured to cover an opening at a lower end of the outer container;
• a plurality of flue tubes provided in the empty space of the outer container to heat heating water flowing in the empty space of the outer container by guiding combustion gas generated by the combustion reaction from the interior space of the combustion chamber to the outside of the lower cover;
• a burner including a fuel nozzle configured to spray fuel of an oil type into the interior space of the combustion chamber, an air nozzle configured to inject air into the interior space, and a spark plug configured to ignite a mixture of the fuel sprayed and the air injected;
• and
• a flame tube part configured to define a tube space by surrounding, in the interior space, a partial space in which the mixture of the sprayed fuel and the injected air is ignited, the flame tube part including a flame tube having an open lower end and a recirculation hole formed through the flame tube such that the combustion gas in the interior space is introduced into the flame tube from the outside of the flame tube;
• wherein the air nozzle is formed to surround the fuel nozzle and injects the air through an air injection opening formed between an inner side surface of the air nozzle and an outer side surface of the fuel nozzle.