Numerical simulation of the combustion characteristics in GCH4-GO_2 shear coaxial injector using various combustion models and kinetic mechanisms

摘要

The injector flow is challenging to predict because of the complex physics phenomenon involving recirculation, turbulence, multiple species mixing, and chemical reactions. The purpose of this paper is to numerically simulate the flame in a GCH_4-GO_2 thrust chamber with various combustion models and chemical kinetic schemes. The unsteady numerical simulations are administrated with the assistance of a 2D-axisymmetric, pressure-based, realizable k-ε turbulence model. Generally, it may be assumed that the chemistry reaction rate is fast in the rockets. Under these conditions, the turbulent combustion of GCH_4-GO_2 was modeled at relevant engine conditions using two combustion models (Non-premixed combustion model (PDF-based steady diffusion flamelet and chemical equilibrium) and Eddy Dissipation Concept combustion model). All the implemented calculations were carried out using the CFD code Fluent. The convergence studies on the grid were performed by examining the temperature profiles along the symmetry axis. For all the approaches used, we performed a comparison with experimental data. And a good agreement is obtained between the computed results and experimental data in terms of OH Chemiluminescence emission. Combustion kinetics plays an important role in turbulent combustion modeling; the computational cost depends on the number of species, number of chemical reactions, and grid size considered in the respective domain. In this work, GCH_4-GO_2 jet flames have been simulated by implementing simple chemistry up to comprehensive multi-step chemistry, as reported in many literatures. And, we observed that the results obtained using the simple kinetic mechanisms in the non-premixed model itself provide a good coherence with experimental results. But reduced kinetic schemes were unable to predict some intermediate species emissions in the combustion engine. Additionally, the effect of various chemical kinetic models on the combustion process was analysed and compared with one another. And the molar concentration changes of some chemistry species for various kinetic models during the combustion process were studied. The primary intention of this work is to study the effect of various combustion models and chemical kinetic schemes in the GCH_4-GO_2 injector and quantify these effects.