Macroscopic characteristics and prediction model of horizontal extension length for syngas jet flame under inclined conditions

As an important industrial raw material, syngas can be used for hydrogen production, and its main components include hydrogen and carbon monoxide. Experiments were conducted on syngas (ratio of CO and H₂ is 1:1) to study the effects of the nozzle inclined angle and diameter as well as the heat release rate on the characteristics of syngas jet flame. Three nozzles with different diameters, 5 mm, 10 mm, and 15 mm, were used in this study. Four different inclined angles of the nozzle corresponding to 0°, 30°, 60°, and 90° were employed. It was found that the normalized horizontal extension length of jet flame (L/D) varies with nozzle diameter and fuel flow rate, and increases exponentially as the dimensionless heat release rate (Q^∗) increases for the nozzle with inclined angles of 0°–60°. By modifying the dimensionless heat release rate and fitting the experimental data, a unified empirical model, which is the first of its kind to date, is established. The model can be used to estimate the horizontal extension length of the syngas jet flame for nozzles with different diameters and inclined angles. For jet flame at an inclined angle of 90°, the normalized jet flame width was exponentially proportional to the modified Froud number with a power of 0.39.