High-pressure combustion devices, such as liquid rocket engines, are usually characterized by transcritical and supercritical operating conditions. Propellants injected in the combustion chamber experience extremely high den- sity gradients and real fluid effects. In the present study, real fluid effects on flame structure are investigated in the framework of unsteady laminar flamelet equations, a well established representation and diagnostic tool for non pre- mixed combustion transient phenomena. Real fluid thermodynamic properties are taken into account by means of a computationally efficient cubic equation of state written in a general and comprehensive three-parameter fashion. High-pressure conditions for unsteady flame structure calculations and analysis are chosen as a representative range of a methane/liquid-oxygen rocket engine operating conditions. Particular focus is posed on the constant pressure specific heat behavior at low temperature, which influences the time evolution of the flame structure. Moreover time accurate integration of flamelet equations represent the very first building block of a conditional moment closure for supercritical turbulent combustion
