Abstract

A numerical simulation model was developed to investigate the cold flow and combustion using Ansys FLUENT 2021R1. The governing equations were solved using the pressure-based method, and pressure–velocity coupling was performed using the SIMPLE method. To model the turbulent process, the RSM model was used. Non-premixed model is chosen to solve the chemical kinetics between fuel and oxigen. Radiation heat transfer was calculated using the DO model, suitable for complex geometries and high optical thickness of radiation mediums while maintaining computational efficiency. The turbulent kinetic energy equation and turbulent dissipation rate equation used a first-order upwind scheme, while the other governing equations employed a second-order upwind scheme. 1.2. Governing equations The flow investigated in this paper obeys three fundamental physical laws: mass conservation, momentum conservation and energy conservation [1]. 1.2.1 Turbulence and Combustion models Since the RSM model accounts for the effects of streamline curvature, swirl, rotation, and rapid changes in strain rate, it has greater potential to give accurate predictions for complex flows. The non-premixed combustion model application scenario is a turbulent diffusion flame, where the oxide and fuel pass through multiple flow paths into the computational region. The transport equation for non-premixed combustion is shown in eq. (1): ∂/∂t (ρf ̅ )+∇.(ρ(vf) ̅ )=∇(μ_t/σ_t ∇f ̅ )+S_m+S_user (1) where ρ denotes the fluid density, v is the average velocity, μ_t denotes the turbulent viscosity, σ_t denotes the equivalent of Pr number, S_m denotes the mass of liquid fuel spray or reaction particles into the gas phase, S_user shows the source items. 1.2.2 Radiation model DO model is adopted as the radiation model for numerical simulation in this paper. DO model equation is shown in eq. (2) [2]. (dI(r ⃗,s ⃗))/ds+(a+σ_s )I(r ⃗,s ⃗ )=an^2 (σT^4)/π+σ_s/4π ∫_0^4π▒〖I(r ⃗,s ⃗ )Φ s ⃗,(s^' ) ⃗)dΩ^' 〗 (2) where r ⃗, s ⃗,s,a,n,σ_s I and T denote the position vector, the scattering direction, the length along the journey, the absorption coefficient, the refraction coefficient, the scattering coefficient, the Stefan Boltzmann's constant (5.67*10–8 W/ (m2⋅K4)), scattering intensity and temperature, respectively. Φ and Ω illustrate the phase function and spatial stereo angle.

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Authors (6)