Large eddy simulation of multi-regime turbulent combustion with modal partially stirred reactor models

Hybrid slime mould algorithm for efficient optimization of chemical kinetic mechanisms in scramjet turbulent combustion simulations

The work presents a numerical simulation of the combustion process of two liquid fuels (benzene and tride cane) with the application of KIVA-II computational program. The research is focused on evaluation of the effect of fuel mass and spray angle on the combustion process and temperature distribution in a cylindrical combustion chamber. The fuel mass is varied from 5 to 20 mg and the spray angle ranges from 2° to 15°. Temperature fields are analyzed over time to determine heat release characteristics and flame structure for both fuels. The results demonstrate that increasing the injection mass leads to a significant rise in flame height and combustion temperature, which is attributed to enhanced heat energy release. The effect of spray angle is found to be significant only at small values, while at higher values it has little influence on the tem perature fields of both fuels. Comparative analysis between benzene and tridecane shows that benzene com bustion occurs more intensively and at higher temperatures than the combustion process of tridecane fuel. These findings are essential for optimizing fuel injection parameters and improving the design of combustion systems in internal combustion engines. The results of the study can be applied to enhance combustion effi ciency and reduce harmful emissions into the environment.

Large eddy simulation of turbulent premixed combustion with a data-driven filtered density function model

Accelerating mixing controlled turbulent combustion simulations with hybrid Navier–Stokes/ANN scalar-solvers

Data-driven modeling and simulation of turbulent combustion

Detailed simulation of RP-3 kerosene turbulent combustion using reduced chemical mechanisms

In turbulent combustion simulation, the swirl flame is an important case because of its widespread applications and modelling complexity. Upon this issue, the filtered turbulent flame model (FTFM) is updated to FTFM-C to better describe extinction and reignition in the flow field. Although both FTFM and FTFM-C are modelling advantageous in the sense that entry parameters are computationally available, FTFM-C is expected to be more capable of predicting species concentrations. The performance of FTFM-C is first validated with laminar counterflow flame to exclude possible numerical interferences and the Sydney bluff-body jet flame HM1 within the framework of large eddy simulation. In studying the Sydney swirl flame SMH1 case, the obtained results from FTFM-C demonstrate that the upstream recirculation zone and the downstream vortex breakdown region can be well captured. A detailed comparison between the FTFM-C predictions and experimental measurements is presented, along with the literature results from the steady laminar flamelet model and the multi-environment filtered density function model. FTFM-C shows acceptable performance, with particular improvements in capturing the flame surface position.

The Flamelet Generated Manifold (FGM) method is widely employed in turbulent combustion simulations due to its high accuracy and computational efficiency. However, the model’s ability to capture turbulent combustion interactions is limited by the shape of the presumed probability density function (PDF) of the mixture fraction and progress variable. To construct a conditional β PDF with better performance, a systematic PDF modeling and analysis framework coupled with machine learning methods based on the sparse experimental data was proposed. A comparative analysis was conducted for five machine learning methods across two experimental datasets using this framework. The results demonstrate that the random forest algorithm represents the optimal choice when both training complexity and predictive performance are comprehensively considered. To expand the model’s applicable range, a data fusion strategy was applied in different machine learning methods. The effectiveness of data fusion is demonstrated by comparative analysis between single-dataset and fused-dataset models. The analysis of convex hull in low-dimensional space reveals the fundamental mechanism of data fusion in the FGM-PDF method, which is significantly important to construct a data-driven PDF model in sparse-data scenarios with much better performance.

ABSTRACT The Flamelet generated manifolds method (FGM) is popular in turbulent combustion simulation because of its low computation cost and ability to combine with detailed chemical reaction mechanisms. However, FGM is suffered from it’s coarse assumption of the joint PDF shape when two controlling variables are used and thus caused a limit to high fidelity. In order to build a joint presumed PDF generation method with high accuracy for FGM, a data driven method based on prior knowledge of PDF characteristics was proposed with random forest model. Firstly, the error analysis for the presumed PDF was conducted based on the data of the two representative flames (Sandia Flame D and Sydney SM1). The results show that β PDF is still a good option for mixture fraction in construction of the joint PDF and the conditional β PDF proposed in this paper can well represent the conditional distribution of progress variable. A random forest model was constructed based on the experimental data to identify the parameters in conditional β PDF. The results show that the new model obtained by small amount of data can decrease the FGM prediction error effectively and show general applicability for different turbulent flames.

The development of new polymer materials with new properties (including reduced flammability) requires refined approaches to investigating their combustion behavior. A new algorithm was tested for calculating the parameters of the turbulent diffusion flame propagation over the PMMA (polymethylmethacrylate) horizontal surface. To solve the coupled problem, an algorithm was used combining the calculation of laminar flame characteristics with the use of a modified OpenFOAM package and the simulation of turbulent gas-phase combustion using FDS (Fire Dynamics Simulator). The computational domain was divided into two zones. The first was the near-wall zone (including the solid combustible material). In the zone, a coupled problem was solved for two-dimensional transport equations describing the laminar regime of the reacting gas-phase flow and heat transfer in the solid material. For solving the problem, the following parameters were used: elliptic formulations of conservation equations for both condensed and gaseous phases, finite-rate chemical kinetics, radiative heat transfer when necessary, and coupled thermal feedback between gas-phase reactions and solid decomposition. The second zone was the outer zone, where three-dimensional equations were solved to describe the turbulent transport and turbulent combustion using the LES method. The dimensions of the coupling interface zone were refined, the coupled problem was calculated using the proposed algorithm, and a comparison was made between the flame spread rates obtained by purely laminar calculations and by the coupled approach.

The paper presents the results of solving the validation problem of turbulent combustion of a hydrogen jet in a supersonic flow of hot humid air in a symmetrical channel. Special attention is paid to the solution of the system of equations of chemical kinetics, which imposes a significant restriction on the time step, as well as the analysis of kinetic schemes used in the solution. The main computational difficulty is the detailed resolution of the wall region, due to the injection of a hydrogen jet into a turbulent boundary layer, in order to further reproduce experimentally obtained distributions of mole fractions and temperature in the outlet section of the channel, as well as the location of the ignition point.

Understanding and accurately modeling combustion processes in engines across a wide range of operating conditions is critical for advancing both subsonic and supersonic propulsion technologies. These engines, characterized by highly complex flow fields, varying degrees of compressibility, and intricate chemical reaction mechanisms, present unique challenges for computational combustion models. Among the various approaches, flamelet models have gained prominence due to their efficiency and intuitive nature. However, traditional flamelet models, which often assume fixed boundary conditions, face significant difficulties. This review article provides a comprehensive overview of the current state of incompressible flamelet modeling, with a focus on recent advancements and their implications for turbulent combustion simulations. The discussion extends to advanced topics such as the modeling of partially premixed combustion, the definition of reaction progress variables, efficient temperature computation, and the handling of mixture fraction variance. Despite the inherent challenges and limitations of flamelet modeling, particularly in 1D applications, the approach remains an attractive option due to its computational efficiency and applicability across a wide range of combustion scenarios. The review also highlights ongoing debates within the research community regarding the validity of the flamelet approach, particularly in high-speed flows, and suggests that while alternative methods may offer more detailed modeling, they often come with prohibitive computational costs. By synthesizing historical context, recent developments, and future directions, this article serves as a valuable resource for both novice and experienced combustion modelers.

Including detailed chemistry features in the modeling of emerging low-temperature reactive flows: A review on the application to diluted and MILD combustion systems

A deep learning framework for supersonic turbulent combustion

A recently proposed scalar forcing scheme that maintains the mixture fraction mean, root-mean-square and probability density function in the unburned gas can lead to a statistically quasi-stationary state in direct numerical simulations of turbulent stratified combustion when combined with velocity forcing. Scalar forcing alongside turbulence forcing leads to greater values of turbulent burning velocity and flame surface area in comparison to unforced simulations for globally fuel-lean mixtures. The sustained unburned gas mixture inhomogeneity changes the percentage shares of back- and front-supported flame elements in comparison to unforced simulations, and this effect is particularly apparent for high turbulence intensities. Scalar forcing does not significantly affect the heat release rates due to different modes of combustion and the micro-mixing rate within the flame characterised by scalar dissipation rate of the reaction progress variable. Thus, scalar forcing has a significant potential for enabling detailed parametric studies as well as providing well-converged time-averaged statistics for stratified-mixture combustion using Direct Numerical Simulations in canonical configurations.

Adaptive mesh refinement towards optimized mesh generation for large eddy simulation of turbulent combustion in a typical micro gas turbine combustor

Detached eddy simulation has become a widely used method in eddy simulations due to its balance between cost and accuracy. The recently developed subgrid dissipation concept (SDC) combustion model [Liu et al., “On the subgrid dissipation concept for large eddy simulation of turbulent combustion,” Combust. Flame 258, 113099 (2023)] is found to be more reasonable and accurate than the conventional eddy dissipation concept model in large eddy simulation (LES). In this paper, the SDC model is adapted to the ℓ2-ω adaptive detached eddy simulation framework, named DES-SDC. The required key quantities, including the fine structure mass fraction and dissipation rate, are appropriately blended across Reynolds-averaged Navier–Stokes and LES regions. The DES-SDC approach is validated using premixed bluff body stabilized flame, non-premixed swirl flame, and premixed swirl flame with complex geometry. It is much more tolerant to coarse mesh resolution than pure LES, yet it preserves the capability of resolving the key unsteady feature critical for the combustion process, as it is designed to be. The DES-SDC approach is relatively insensitive to the grid resolution. The present research provides a promising approach for accurately simulating practical unsteady turbulent combustion problems at an affordable computational cost.

Mathematical Simulation of Turbulent Combustion of Air–Propane Mixture in Swirl Flow

Abstract The flamelet model is a commonly used tool for turbulent combustion simulations in the engineering field due to its computational efficiency and compatibility with complex chemical reaction mechanisms. Despite being widely used for decades, the flamelet model still faces challenges when applied to complex flame configurations, such as partially premixed flames, inhomogeneous inlets, supersonic combustion, or multiphase combustion. The principal challenges are posed by the uncertainty of the presumed shapes for probability density functions (PDFs) of the flamelet tabulation variables and the coupled process of turbulent diffusion and chemical reaction in turbulent combustion. Recent progress is reviewed from the viewpoint of the reaction manifold, with connections made to other combustion models, as well as the determination of joint (or conditional) PDFs for flamelet manifold parameters (e.g., progress variable, scalar dissipation rates, etc.). Promising improvements have been outlined in computational efficiency and the accuracy of predicted variable fields in simulating complex combustion systems (such as turbulent inhomogeneous combustion, combustion with multi-regime modes, and two-phase combustion). Advances in computational resources, direct numerical simulation data, artificial intelligence, stochastic simulation methods, and other dimension-reduction combustion models will contribute to the development of more accurate and efficient flamelet-like models for engineering applications.