Investigation on effect of mixing distance on mixing process and combustion characteristics of double-cone burner

Investigations of mixing process, combustion and emission characteristics have been performed in a double-cone premixed burner under various mixing distances. The complex flow field and flame structure are accurately captured by the simulation model. The modified unmixedness coefficient, flame index, NO, CO emissions have been calculated and analyzed in detail. Numerical results show that the dimensionless mixing distance has a significant impact on the fuel mixing effect and then affects the high temperature zone position and emissions. With the increase of dimensionless mixing distance, the mixing process is mainly affected by the inner recirculation zone instead of the outer recirculation zone. The high temperature zone changes from the corner to the center. When the dimensionless mixing distance is 0.15, the peak concentration of CH2O and OH is below 1500 K, and the concentrations are relatively lower above 1500 K. The concentration scatter is relatively concentrated, which indicates that the mixing quality is the best and the reaction is the most uniform. The combustion mode is dominated by premixed combustion. When the dimensionless mixing distance is 0.1 and 0.2, regions with higher concentration of CH2O and OH still exist after 2000 K. The proportion of non-premixed combustion mode increases and the combustion temperature is high. NO and CO emissions first decrease and then increase with the increase of mixing distance from 0.1 to 0.2. According to the present analysis, the emission is the lowest when the dimensionless mixing distance is 0.15.