In Burners 104, I introduced the concept of the modern nozzle-mix burner. (To start at Burner History 101 or any previous part of this five-part series, use the links at the bottom of the page.) Continuous development from the 1920s through the 1950s resulted in numerous designs with excellent flame stability over a wide range of firing rates and ratios. The versatility of these burners made them suitable for a variety of applications.
Having overcome the firing rate and fuel/air ratio issues, designers moved on to the challenge of molding the flame into shapes suitable for specific applications. By controlling the velocity and direction of the air and gas flowing into burners, they were able to create a variety of flame configurations from flat, disc-shaped to long and pencil-slim (figure 1).