Effects of pressure and inlet temperature on coaxial gaseous methane/liquid oxygen turbulent jet flame under transcritical conditions

• Published in: The Journal of supercritical fluids 2013-09, Vol.81, p.164-174
• Main Authors: Kim, Taehoon, Kim, Yongmo, Kim, Seong-Ku
• Format: Article
• Language: English
• Subjects: Effects of chamber pressure; Effects of oxidizer temperature; Flame structure; Fluid flow; Inlet temperature; Liquid oxygen; Mathematical models; Methane; Real-fluid flamelet model; Transcritical flames; Turbulence⿿chemistry interaction; Turbulent flames; Turbulent flow
• ISSN: 0896-8446; 1872-8162
• DOI: 10.1016/j.supflu.2013.05.011

[Display omitted] ⿢The predicted contours of the OH radical are reasonably well agreed with experimental image.⿢The high level of CO is generated in the GCH4/LOx flame zone due to strong chemical dissociation.⿢The GCH4/LOx coaxial flames are greatly influenced by varying oxidizer inlet temperature and chamber pressure.⿢The characteristics of GCH4/LOx flame at supercritical pressures are realistically simulated. This study has investigated numerically turbulent flames of cryogenic oxygen and methane under supercritical pressures relevant to liquid propellant rocket engines. A real-fluid version of the flamelet equations is employed to accommodate simultaneously non-equilibrium chemistry of hydrocarbon fuel and non-ideal thermodynamics in local flame structures while the effect of turbulent fluctuations is accounted for via a presumed probability density functions. The present model reproduced qualitatively well the experimentally observed unique feature of a transcritical flame of coaxial gaseous methane/liquid oxygen injector, which is characterized by sudden flame expansion, abruptly terminated flame tip, and expansion induced flow recirculation. Numerical results reveal that pseudo-boiling phenomena occurred in the transcritical mixing layer between the cryogenic oxygen core and the surrounding hot gas play a crucial role in mixing and combustion processes. It is also found that the transcritical flame structure is drastically affected by elevating the chamber pressure or increasing the oxygen inlet temperature in terms of flame length, sudden expansion angle, and reverse flow strength. Detailed discussions are made for effects of the real-fluid behaviors on the turbulent flame field as well as on the local flame structure in mixture fraction space.