CFD Dataset of an Axisymmetric Non-Premixed Methane Coflow Flame under Fuel-Velocity Excitations

This dataset contains the results of multiple CFD simulations of an axisymmetric, time-varying, non-premixed laminar methane coflow flame subjected to time-varying fuel-inlet velocity perturbations and their relative mesh. The simulations were performed using laminarSMOKE [1] , a CFD solver for laminar reacting flows with detailed kinetic mechanisms based on the OpenFOAM and OpenSMOKE++ frameworks[2]. The solver uses the operator-splitting technique, advancing each time step through two sub-steps: a transport sub-step involving convection and diffusion, and a chemical sub-step. The configuration considered is an axisymmetric, time-varying, non-premixed laminar coflow flame that has been numerically and experimentally studied by Mohammed et al. [3] and D'Alessio et al [4]. The computational domain and mesh adopted in the present simulations are based on the configuration reported by D’Alessio et al. [4]. The fuel is a nitrogen-diluted mixture consisting of 65% CH₄ and 35% N₂ on a molar basis, while the oxidizer is air. Both streams are supplied at ambient temperature and atmospheric pressure. A reduced version of the detailed mechanism C1C3 for high temperature [5] (82 species and 1,698 species) from the CRECK Modeling group is used for all simulations. The CH₄/N₂ fuel stream enters through a circular nozzle with an internal diameter of 4 mm and a wall thickness of 0.38 mm. The coflow air stream enters through an annular region with an internal diameter of 50 mm. The two-dimensional axisymmetric computational domain has dimensions of 54 mm in the radial direction and 120 mm in the axial direction. The domain is discretised using a Cartesian mesh of approximately 21,000 cells. The transient behavior is induced by time-varying perturbations of the fuel-inlet velocity. The reference configuration defines the radial velocity profile as $v_r(r,t) = v_{\max} \left( 1-\frac{r^2}{R^2} \right) \phi(t)$ where $r$ is the radial coordinate, $R$ the internal radius of the fuel nozzle, $t$ is time, $v_{\max}$=70 cm/s is the maximum baseline velocity, $\phi(t)$ is a dimensionless time-dependent excitation function. The coflow air is injected at a constant velocity of 35 cm/s [3][4]. Different excitation functions are used in the present dataset. For sinusoidal excitations, the perturbation is defined as $\phi(t)=1+A\sin(2\pi f t),$ where $A$ is the dimensionless perturbation amplitude and $f$ is the excitation frequency. For the sine-sweep excitations, the same sinusoidal form is used with a time-dependent instantaneous frequency: $\phi(t)=1+A\sin\left(2\pi\int_0^t f(\tau) d\tau\right), $ where $f(t)$ varies continuously from 1 Hz to 80 Hz and back to 1 Hz over a total duration of 2 s. For the step excitations, the perturbation is defined as $\phi_{\mathrm{step}}(t)=\begin{cases}1, & t<t_0,\\1+A, & t\geq t_0,\end{cases}$ where $t_0=0$ is the time at which the step is applied. The dataset extends this reference configuration to a range of transient excitation signals for system identification and data-driven reduced-order modelling of reacting flows. The imposed fuel-velocity excitations include: Sine sweep: 2 s, 1–80–1 Hz, (A=0.2); Sine sweep: 2 s, 1–80–1 Hz, (A=0.4); Step: 1 s, (A=0.3); Step: 1 s, (A=0.5); Sine: 1 s, 10 Hz, (A=0.3); Sine: 1 s, 10 Hz, (A=0.5); Sine: 1 s, 40 Hz, (A=0.3); Sine: 1 s, 40 Hz, (A=0.5). Each simulation has a sampling interval of 0.5 ms. The outputs provided in each .npy file include: Pressure P; Velocity U1, U3; Density: rho; Temperature: T; Heat release rate: mix:Q; Species mass fractions: CH4, O2, H2O, CO2, OH. Please cite this dataset when using these data. Additional information can be found in the provided README.ipynb.