Experimental Study on Hydrodynamic Instability Characteristics of N2-Diluted n-C4H10/Air Flat Flames

• Published in: Flow, turbulence and combustion Vol. 108; no. 4; pp. 1115 - 1137
• Main Authors: Jiang, Liqiao, Zhou, Guangzhao, Huo, Jiepeng, Gu, Chen, Chen, Xiaoli
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2022; Springer Nature B.V
• Subjects: Automotive Engineering; Cellular structure; Chemiluminescence; Diffusion effects; Dilution; Engineering; Engineering Fluid Dynamics; Engineering Thermodynamics; Equivalence ratio; Flame speed; Flow velocity; Fluid- and Aerodynamics; Heat and Mass Transfer; Heat loss; High temperature; Local flow; Mixtures; Morphology; Oxidizing agents; Planar laser induced fluorescence; Stability; Stability analysis; Stoichiometry; Flat flame burner; dilution; PLIF; n-Butane; N; Hydrodynamic instability
• ISSN: 1386-6184; 1573-1987
• DOI: 10.1007/s10494-021-00303-9

The hydrodynamic instability characteristics of non-adiabatic N 2 -diluted n-butane/air flames generated on McKenna burner were investigated experimentally under atmosphere pressure. In order to capture the quantitative structure of cellular flames, planar laser induced fluorescence technology (OH-PLIF and CH 2 O-PLIF) was employed, as well as the chemiluminescence imaging was used to record flame morphology directly. The results show that the hydrodynamic instability of stoichiometric ( Φ  = 1.0) n-butane/air flames can be significantly enhanced by N 2 dilution. In addition, the increased mixture flow velocity and the reduced equivalence ratio of lean mixtures will enhance hydrodynamic instability. Moreover, the observed flame morphologies are connected wrinkles instead of independent-cells with lean and stoichiometric mixtures. It is probable that the wrinkled flames mainly caused by hydrodynamic instability cannot induce the extinction of high-temperature oxidant reaction in concave regions solely due to the weakened effect of preferential diffusion. The instability mechanism analysis shows that, the remarkably reduced local flame speed and the much deformed local flow field ahead of n-butane/air/N 2 dilution flames by increasing N 2 dilution ratio play an important role in enhancing hydrodynamic instability. It also indicates that the heat loss reduced more in concave regions than in convex regions toward unburnt mixtures is helpful to enhance the suppression effect of hydrodynamic instability.