A Numerical Study Of Plasma-assisted Combustion By CFD Modeling Coupled With Fluid Dynamics And Kinetic Mechanism

Plasma-assisted combustion has drawn considerable attention due to its greatpotential in enhancing both thermally and kinetically the ignition and flame stabilization ofLHV renewable fuels and therefore requires a fundamental understanding of the underlyingenhancement mechanisms. Firstly, a turbulent partially premixed methane-air jet flame isnumerically simulated by using two different kinetic mechanisms (a five-step globalmechanism and a detailed mechanism GRI-Mesh2.11). Numerical results of axial profilesof temperature and species mass fraction are compared with experimental data. Based onthe CFD models of traditional piloted methane-air combustion, a comparative study ofplasma-assisted combustion is carried out by replacing pilot ignition with plasma dischargeto ignite the partially-premixed methane/air combustion on the same burner configuration.The thermal effect of plasma assistance is numerically isolated and analyzed by using theglobal mechanism, which doesn’t take into account the plasma-produced radicals.Meanwhile, when the thermal and kinetic effects of plasma assistance are taken intoaccount by detailed chemistry modeling, plasma-assisted methane/air combustiondemonstrates a further improved combustion performance. The respective behaviors of themost important plasma-produced radicals (OH, O and H radical) have been investigated. Itis proven that the kinetic enhancement of plasma by means of in-situ and real-timegeneration of reactive species has a significant effect on fuel ignition characteristics andoxidation process.On the other hand, a numerical study is also performed on modeling thermochemicalpreparation of solid biomass fuels for combustion by an industrial plasma-fuel system,which is normally applied for fuel ignition and flame stability of pulverized coalcombustion in power plants. A2D CFD model of the plasma-fuel system is constructedwith the coupling of heterogeneous chemical mechanism of solid-phase fuel combustion.The simulation results proves that plasma-fuel system is efficient to convert LHV solid fuels into a high-concentration of combustible gases, which will self-ignite once mixedwith secondary air in the furnace. The highly-reactive fuel products at PFS exit willenhance ignition and combustion of the main biomass fuels in a furnace, thus allowingoil-free start-up of boiler and stabilizing the combustion flame when burning low-qualitysolid fuels. So, the feasibility and potential of plasma thermochemical preparation ofbiomass fuels for combustion is demonstrated by CFD simulation.