Low NOX - LPG staged combustion double swirl flames

As a clean, abundant energy source with demonstrated methodologies for producing liquid petroleum gas (LPG) from renewable feedstocks, the growing availability of LPG motivates this study to investigate the utilization of LPG in a staged swirl burner. The burner has an outer and annular swirlers concentric with a central jet, where the flame stability, NO emissions, and flame structure were investigated. The burner allows controlling the degree of mixing by varying swirl angles (θan, θout), and the equivalence ratios of the annular/outer streams (Φan/Φout). The stability mapping showed that the LPG admitted via the annular mixture improves the flame stability more than the outer mixture, and the central fuel injection further improves the flame’s stability. Less segregation between Φan and Φout leads to low NO emissions. Three distinct zones have featured the flame; the recirculation zone (RZ), the reaction zone; and the outer flame zone. High NO concentration was limited to the RZ, so the RZ residence time, mixture strength and temperature at the RZ boundaries are the controlling parameters for NO emissions. The largest θan together with a small θout has a significant effect on reducing the flame temperature and residence time, and thus produces low NO emissions.