Within the context of supersonic combustion modeling in air-breathing propulsion, the turbulent Prandtl and turbulent Schmidt numbers have a profound effect on the resulting predictions. This work considers a Scalar Fluctuation Model (SFM) introducing two extra transport equations in order to specify variable values for turbulent Prandtl and turbulent Schmidt numbers within a Reynolds-Averaged Navier-Stokes (RANS) framework relying on a gradient diffusion hypothesis for both the turbulent heat and mass flux. The SFM is applied in conjunction with a two-equation linear eddy viscosity model. In order to study the effect of the different modeling choices, the supersonic reacting wall jet experiment of Burrows and Kurkov [24] is considered. A strong effect of Turbulence Chemistry Interaction (TCI) through an assumed PDF approach on the SFM is observed and needs to be enabled in order for predictions to be within experimental observation bounds in terms of ignition delay. Overall, the presented SFM methodology could be a viable candidate for supersonic combustion studies.

ABSTRACT The eddy dissipation model (EDM) is analysed with respect to the ability to address the turbulence–combustion interaction process inside hydrogen-fuelled scramjet engines designed to operate at high Mach numbers (≈7–12). The aim is to identify the most appropriate strategy for the use of the model and the calibration of the modelling constants for future design purposes. To this end, three hydrogen-fuelled experimental scramjet configurations with different fuel injection approaches are studied numerically. The first case consists of parallel fuel injection and it is shown that relying on estimates of ignition delay from a 1D kinetics program can greatly improve the effectiveness of the EDM. This was achieved through a proposed zonal approach. The second case considers fuel injection behind a strut. Here the EDM predicts two reacting layers along the domain which is in agreement with experimental temperature profiles close to the point of injection but not the case any more at the downstream end of the test section. The first two scramjet test cases demonstrated that the kinetic limit, which can be applied to the EDM, does not improve the predictions in comparison to experimental data. The last case considered a transverse injection of hydrogen and the EDM approach provided overall good agreement with experimental pressure traces except in the vicinity of the injection location. The EDM appears to be a suitable tool for scramjet combustor analysis incorporating different fuel injection mechanisms with hydrogen. More specifically, the considered test cases demonstrate that the model provides reasonable predictions of pressure, velocity, temperature and composition.

This paper considers the Eddy Dissipation Model to address the combustion process inside scramjet engines designed to operate at high flight Mach numbers. The aim is to demonstrate the most appropriate use of the model for design purposes. To this end, two hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. In the case of parallel fuel injection, it is demonstrated that relying on estimates of ignition delay from a one-dimensional kinetics program can greatly improve the use of the EDM. In the second case, the transverse injection of hydrogen resulted in an overall good agreement of the model with experimental pressure traces except in the vicinity of the injection location. Overall, the EDM appears to be a suitable tool for scramjet combustor design incorporating a parallel or transverse fuel injection mechanism.

The Eddy Dissipation Model is critically analyzed with respect to the ability to address the turbulence-combustion interaction process inside scramjet engines designed to operate at high Mach numbers. The aim is to identify the most appropriate strategy for the use of the model for design purposes. To this end, three hydrogen-fueled experimental scramjet configurations with different fuel injection approaches are studied numerically. The first case consists of parallel fuel injection and it is shown that relying on estimates of ignition delay from a onedimensional kinetics program can greatly improve the effectiveness of the EDM. The second case considers fuel injection behind a strut. Here the EDM predicts two reacting layers along the domain which are not experimentally captured from a certain distance downstream the point of injection. The last case considered a transverse injection of hydrogen and the EDM approach provided an overall good agreement with experimental pressure traces except in the vicinity of the injection location. The EDM approach appears to be a suitable tool for combustor design incorporating different fuel injection mechanisms.

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Two open-source solvers, Eilmer and hyFoam, are here considered for their performance in simulating high-speed flows in different flow conditions and geometric configurations typical of propulsive systems at supersonic speeds. The goal is to identify the open-source platform providing the best compromise between accuracy, flexibility and computational cost to eventually simulate the flow fields inside ramjet and scramjet engines. The differences in terms of discretization and solution methods of the selected solvers are discussed in terms of their impact on solution accuracy and computational efficiency and in view of the aerothermodynamic analysis and design of future trans-atmospheric propulsive systems. In this work steady state problems are considered. Numerical results of two scramjet type engines demonstrated a similar predictive capability of both codes in non-reacting conditions. These results highlight their potential to be considered for further characterization of overall engine performance.