  This article aims to numerically investigate the combustion phenomenon of
coaxial gaseous CH4 LOx at supercritical pressures. The choice of turbulence
model, real gas model, and chemical kinetics model are the critical parameters
in numerical simulations of cryogenic combustion at high pressure. At this
supercritical operating pressure, the ideal gas law does not remain valid for
such cases. Therefore, we have systematically carried out a comparative study
to analyze the importance of real gas models, turbulence parameters, and
chemical kinetics at such conditions. The comparison of real gas models with
the NIST database reveals better conformity of SRK (Soave Redlich Kwong
Equation of State (EoS)) model predictions with the database. Further, the
computed results indicate that the Standard k-e turbulence model with modified
constant captures the better flame shape and temperature peak position compared
to other RANS based turbulence models while invoking the non-premixed steady
b-PDF flamelet model for simulating the combustion process. Furthermore, a
comparative study comparing two different chemical kinetics models indicates
that the reduced Jones Lindstedt mechanism can accurately predict the flame
characteristics with the least computational cost. Finally, we have studied the
effect of chamber pressure and LOx inlet temperature on the flame
characteristics. The flame characteristics exhibit a strong sensitivity towards
the chamber pressure due to the weakening of the pseudo-boiling effect with an
increase in pressure. As a consequence of lower turbulent rates of energy and
mass transfer through the transcritical mixing layer, the flame spreading
becomes narrower at elevated pressure and temperature, thereby yielding an
increased flame length at transcritical conditions.
