Combustion tests including gas temperature and emission measurements are conducted to obtain a knowledge of NOx reduction with a small paraffin oil burner for water heater. Two kinds of combustion liner with a different swirler height are provided to investigate the effect of Swirl number on NOx reduction. The NOx emission characteristic and gas temperature distribution characteristic inside of the liner are clarified for the changes of combustion load and Swirl number. It is shown that the NOx emission can be effectively reduced by the decrease of Swirl number to be lower gas temperature in the primary zone.
