Methane pyrolysis: Literature survey and comparisons of available data for use in numerical simulations

• Review on methane pyrolysis experiments and modelling.
• Comparison between ten different kinetic models.
• Consideration of combustion mechanisms to test their potential.
• Following specific criteria (size, accuracy, coke prediction), one model emerges.

Methane pyrolysis has been investigated in the open literature for a number of applications (improvement of fuel cracking, production of hydrogen, aeronautics and space use for cooling). This implies a large panel of experimental conditions and the development of numerous kinetic schemes, all validated for different test ranges. During the past decade, a renewal of interest has emerged related to the possibility of using methane as a jet fuel for hypersonic applications. Within this context, the ability of the existing kinetic schemes to reproduce the chemical behaviour of the fuel during its pyrolysis (T > 1500 K and P > 1 MPa) needs to be determined in order to for these mechanisms to be used in Computational Fluid Dynamics simulations. Thus, a balance must be found between the accuracy of the predictions and the computation time (linked to the mechanism size). This work proposes to review a large panel of the experimental and numerical works and then compare the existing schemes with available data to estimate their potential (considering, if possible, the maximal stressing conditions). After a first selection, ten mechanisms are quantitatively compared with regard to three important species: methane, which reflects the pyrolysis rate; hydrogen, linked to propulsion efficiency, and acetylene which is involved in the formation of coke (unwanted effect). The computation time has also been determined and it serves as an additional selection criterion. One model seems to emerge in view of its accuracy and its size. This results in predictions with disagreement under 40% compared to the reference data and a calculation time of less than 1 s for a simulated time of 10 s in the 0-D configuration.