Effect of mixture flow stratification on premixed flame structure and emissions under counter-rotating swirl burner configuration. (25th July 2016)

• Record Type: Journal Article
• Authors: Chong, Cheng Tung; Lam, Su Shiung; Hochgreb, Simone
• Is Part Of: Applied thermal engineering. Volume 105(2016:Jul.)
• Page Start: 905
• Page End: 912
• Publication Date: 2016-07-25
• Subjects: Counter-rotating -- Emissions -- Combustor -- Swirl flame -- OH∗ chemiluminescence; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2016.03.164
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: Flame structure of counter swirl flame depends on mixture and flow stratification. High swirl flow in the inner annulus generates elongated and enlarged flame reaction zone. Mixture and flow stratification affect local emissions. Rich stratification of inner channel results in higher NO x and CO emissions. Enrichment of outer annulus shows comparable emission levels to homogenous premixed flames. Abstract: An investigation of the flame structure and emission performance of stratified swirl methane/air flames was performed by using a double-annulus counter-rotating premixed swirl burner. Stratification of the flow and mixtures were established by varying the bulk air flow rates and mixture equivalence ratios between the inner and outer annuli. Two distinct flame fronts were stabilised at the burner outlet, separated by a shear layer due to velocity differences. Higher swirl flow in the inner annulus generates an elongated and enlarged area of flame reaction zone due to increased flame intensity, as the flame shape is strongly dependent on the velocity magnitude exiting the annulus. Mixture and flow stratification affect local emissions. A richer mixture stratification within the inner channel at 70:30 flow split results in 91% and 49% higher emission rates of NO and CO respectively compared to premixed arrangement, in spite generally aiding flame stability. Enrichment of the outer annulus at 70:30 split flow shows only slightly higher levels of NO and CO emissions by 3% and 9% respectively compared to a homogenous mixture.