Numerical and experimental investigation of methane-oxygen detonation in a 9 m long tube

Numerical investigation of methane-oxygen detonation parameters was conducted with an OpenFoam code. Custom solver ddtFoam made especially for detonation problems was made use of. It uses the HLLC scheme to resolve the discontinuities and the subgridscale model to improve results on coarse meshes. Combustion model is based on progress variable equation, which contains two source terms. The first is the deflagrative source term and is modelled using the Weller correlation. The second is the detonative source term and it accounts for autoignition effects. Range of analysed gaseous mixture compositions was 20, 33 and 40% of methane in oxygen. The 2D calculation geometry was a 9 m long pipe with diameter 0.17 m. The mesh consisted of 382 500 hexahedral cells with the dimensions of 2x2 mm. Experimental results such as pressure profiles and detonation velocities are presented. Simulations were performed using LES turbulence model (k-equation-eddy-viscosity model) and compared with experimental data. Various dynamic parameters, like for example reaction lengths for methane-oxygen detonations, are estimated from the steady ZND analyses conducted in Cantera and SDToolbox libraries and based on GRI 3.0 kinetic mechanism of methane combustion. These lengths were then used in empirical formulas to obtain the characteristic cell sizes and assessed against experimental data.