Multivariate Study of the Effects of Geometric Design Parameters on Furnace Performance

In low - NOx burner designs, small changes in burner geometry can significantly increase, or reduce, NOx and CO emissions. Of interest is the optimal design for a given configuration. Rather than testing all possible burner configurations, a design of experiments (DoE) can be used to optimize the testing process by systematically varying the parameters. The statistics-based analysis of variance (ANOVA) can then be used to analyze the results to identify effects of parameters on the responses or interactions between parameters. In the present case, a specially designed (for parametric flexibility) practical burner was utilized. The parameters and their ranges include: a) flame holder angle (30°, 90°); b) fuel injection hole diameter (0.1", 0.3"); c) fuel injection hole location (1.25", 4.25" from base of flame holder); and d) swirl angle (30°, 60°). Results show that CO concentrations and combustion efficiency are not affected by the hardware changes. However, NOx emissions are affected by an interaction between the fuel injection hole diameter and the swirl angle. In particular, in the present case, lower NOx emissions are achieved by either a combination of smaller fuel injection hole diameter and larger swirl angle or a combination of larger fuel injection hole diameter and smaller swirl angle.