Large Eddy Simulation of Combustion for High-Speed Airbreathing Engines

Abstract

Large Eddy Simulation (LES) has rapidly developed into a powerful computational methodology for fluid dynamic studies, between Reynolds-Averaged Navier–Stokes (RANS) and Direct Numerical Simulation (DNS) in both accuracy and cost. High-speed combustion applications, such as ramjets, scramjets, dual-mode ramjets, and rotating detonation engines, are promising propulsion systems, but also challenging to analyze and develop. In this paper, the building blocks needed to perform LES of high-speed combustion are reviewed. Modelling of the unresolved, subgrid terms in the filtered LES equations is highlighted. The main families of combustion models are presented, focusing on finite-rate chemistry models. The density-based finite volume method and the reaction mechanisms commonly employed in LES of high-speed H2-air combustion are briefly reviewed. Three high-speed combustor applications are presented: an experiment of supersonic flame stabilization behind a bluff body, a direct connect facility experiment as a transition case from ramjet to scramjet operation mode, and the STRATOFLY MR3 Small-Scale Flight Experiment. Several combinations of turbulence and combustion models are compared. Comparisons with experiments are also provided when available. Overall, the results show good agreement with experimental data (e.g., shock train, mixing, wall heat flux, transition from ramjet to scramjet operation mode).

Development and Validation of a Compressible Reacting Gas-Dynamic Flow Solver for Supersonic Combustion

“…Gas flow passing the corners of the wedge are subjected to expansion by forming two expansion waves. The jet vortex structure arises from the Kelvin-Helmholtz instability of the jet-shear layer [14]. It is noteworthy that the simulation with the 𝑘−𝜀 turbulent model did not generate shear-layer instabilities as reported by Oevermann [58].…”

“…A LES formulation is used to solve the equations for turbulent fluid flow. After Favre filtering, these equations can be written as [14,48] 𝜕 (𝜌̅ ) + 𝛁 • (𝜌̅ 𝒖 )=0, ( 1 )…”

“…During the past decade, LES, which is a compromise between the DNS [9] and the RANS [10] methods, has been extensively used to study high-speed combustion applications [11][12][13]. In LES, turbulence scales larger than the grid spacing are resolved, while subgrid scales and their effects on the large scales are modeled [14]. LES has been shown [15][16][17][18][19] to be computationally practical for modeling unsteady phenomena, including transient combustion events.…”

“…Among the open-source codes, the OpenFOAM library is a well-established open platform in the scientific community [29]. It is noteworthy that there are several in-house codes reported in the literature for high-speed compressible reacting flows [13,14,[30][31][32][33][34][35][36][37]. These codes have been used to solve many problems involving turbulence-combustion interactions.…”

Development and Validation of a Compressible Reacting Gas-Dynamic Flow Solver for Supersonic Combustion

“…During the past decade, LES, which is a compromise between the DNS [9] and the RANS [10] methods, has been extensively used to study high-speed combustion applications [11][12][13]. In LES, turbulence scales larger than the grid spacing are resolved, while subgrid scales and their effects on the large scales are modeled [14]. LES has been shown [15][16][17][18][19] to be computationally practical for modeling unsteady phenomena, including transient combustion events.…”