Modeling of High Speed Reacting Flows: Established Practices and Future Challenges

Abstract

Computational fluid dynamics (CFD) has proven to be an invaluable tool for the design and analysis of highspeed propulsion devices. Massively parallel computing, together with the maturation of robust CFD codes, has made it possible to perform simulations of complete engine flowpaths. Steady-state Reynolds-Averaged Navier-Stokes simulations are now routinely used in the scramjet engine development cycle to determine optimal fuel injector arrangements, investigate trends noted during testing, and extract various measures of engine efficiency. Unfortunately, the turbulence and combustion models used in these codes have not changed significantly over the past decade. Hence, the CFD practitioner must often rely heavily on existing measurements (at similar flow conditions) to calibrate model coefficients on a caseby-case basis. This paper provides an overview of the modeled equations typically employed by commercialquality CFD codes for high-speed combustion applications. Careful attention is given to the approximations employed for each of the unclosed terms in the averaged equation set. The salient features (and shortcomings) of common models used to close these terms are covered in detail, and several academic efforts aimed at addressing these shortcomings are discussed.

Computational Simulation of Scramjet Combustors - A Comparison between Quasi-One Dimensional and 2-D Numerical Simulations

“…In the above given equations 17 to 20, ρ is the density, P is the pressure, u i is the velocity, E is the total energy which is equal to the sum of total internal energy and kinetic energy, H is total enthalpy which is equal to the sum of total internal energy and pressure-volume work, τ ij is the stress tensor, q j is the heat flux vector and X m , V j and m w  are mass fraction, mass diffusion velocity, and mass production rate, respectively of species "m" [84].…”

Numerical Simulation of Hydrogen Jet Injection and Ignition in Supersonic Flow

“…When combustion dynamics are added to the problem, uncertainty exists in the turbulence-chemistry interaction, shock wavechemistry interaction, as well as the general lack of adequate knowledge of the effects of supersonic conditions on turbulence, reaction rates, and flame regimes. Review of these problems can be found in [11][12].…”

Methods for Prediction of High-Speed Reacting Flows in Aerospace Propulsion

“…The required turbulence and combustion models have not significantly advanced in the past 20 years, and modelers must rely on experimental data and intuition to validate these phenomenological models. An excellent review of the modeled equations that are typically solved and the models needed to close the equations was given by Baurle [102]. The limitations introduced by the models have resulted in the move to higher-order modeling including LES and PDF methods.…”