Turbulent mixing for a jet in crossflow and plans for turbulent combustion simulations

1. Turbulent mixing for a jet in crossflow and plansfor turbulent combustion simulations James Glimm

2. Stony Brook University James Glimm Xiaolin Li Xiangmin Jiao Yan Yu Ryan Kaufman Ying Xu Vinay Mahadeo Hao Zhang Hyunkyung Lim Drew University Srabasti Dutta Los Alamos National Laboratory David H. Sharp John Grove Bradley Plohr Wurigen Bo Baolian Cheng The Team/Collaborators

3. Outline of Presentation • Problem specification and dimensional analysis • Experimental configuration • HyShot II configuration • Plans for combustion simulations • Fine scale simulations for V&V purposes • HyShot II simulation plans • Preliminary simulation results for mixing

4. Main Objective • Compare to the Stanford code development effort. Chemistry to be computed without a model (beyond dynamic turbulence model). Hereby we can offer a UQ assessment of the accuracy of the Stanford code. • If the comparison is satisfactory and the two codes agree, the UQ analysis of the Stanford code (in this aspect) will be complete. • If the comparison is unsatisfactory, we will attempt to determine which of the differing results are to be believed.

5. Problem Specification andDimensional Analysis • Experimental configuration • Problem dimensions = 8.6 x 2 x 2 cm • Parameters for crossflow (air) • Crossflow Ma = 2.4; flow velocity = 1800 m/s • Crossflow pressure = 0.4 Bar • Crossflow Temperature = 1548K • L (air) = distance of nozzle downstream = 0.067 m • Viscosity (air) = 5.36e-4 m2/s • Re (air) = 2.25e5 • Kolmogorov scale (air) = L Re-3/4 = 6.5 microns • Parameters for H2 • H2 flow M = 1; H2 velocity = 1205 m/s • H2 pressure = 20.2 Bar • H2 Temperature = 300 K • Viscosity of H2 = 0.16e-4 m2/s • L (H2) = nozzle diameter = 2 mm • Re (H2) = 1.5e5 • Kolmogorov scale (H2) = LRe-3/4 = 11 microns • Flame width (OH, from experiment) = 200 microns • Momentum flux ratio J = jet/crossflow = 5

6. Problem Specification andDimensional Analysis • HyShot II Scramjet configuration * • Combustion chamber dimensions = 29.5 x 0.98 x 7.5 cm • Reduced by symmetry to 29.5 x 0.98 x 0.9375 cm • Volume is 0.79 as a fraction of the experimental combustion chamber (after symmetry reduction) • Crossflow (air) parameters • Crossflow Ma = 2.4; flow velocity = 1720 m/s • Crossflow pressure = 130 KPa • Crossflow Temperature = 1300 K • Viscosity of air = 0.000182 m/s • L (air) = 5 cm (from inflow plane to injector) • Re (air) = 4.7e5 • Kolmogorov scale (air) = LRe-3/4 = 2.8 microns • H2 parameters (at injector exit) • H2 flow M = 1; velocity = 1200 m/s • H2 pressure = 4.6 bar • H2 Temperature = 300 K • Viscosity of H2 = 2.22e-5 m2/s • L (H2) = nozzle diameter = 2 mm • Re (H2) = 1.1 e5 • Kolmogorov scale (H2) = LRe-3/4 = 35 microns • Flame width (OH, from experiment) = 200 microns • J = ratio of momentum flux jet/crossflow = 0.55 *Sebastian Karl, Klaus Hannemann, Andreas Mack, Johan Steelant, “CFD Analysis of the HyShot II Scramjet Experiments in the HEG Shock Tunnel”, 15th AIAA International Space Planes and Hypersonic Systems and Technologies Conference

7. Problem Specification andDimensional Analysis • Simulation Parameters: Experimental Configuration • Fine grid: approximately 60 micron grid • Mesh = 1500 x 350 x 350 = 183 M cells • If necessary, we can simulate only a fraction of the experimental domain • If necessary, a few levels of AMR can be used • HyShot II configuration • Resolution problem is similar • 3/4 volume after symmetry reduction compared to experiment • Full (symmetry reduced) domain needed to model unstart • Resolved chemistry might be feasible • Wall heating an important issue

8. Flow and Chemistry Regime • Turbulence scale << chemistry scale • Broken reaction zone • Autoignition flow regime • Tc << T • Makes flame stable against extinction from turbulent fluctuations within flame structure • Unusual regime for turbulent combustion • Broken reaction zone autoignition distributed flame regime • Query to Stanford team: literature on this flow regime? • Knudsen and Pitsch Comb and Flame 2009 • Modification to FlameMaster for this regime? • Opportunity to develop validated combustion models for this regime, for use in other applications • Some applications of DOE interest

9. Flow, Simulation and Chemistry Scales; Experimental Regime • Turbulence scale << grid scale << chemistry scale • Turbulence scale = 10 microns • << grid scale = 60 microns • << chemistry scale 200 microns • Resolved chemistry, but not resolved turbulence • Need for dynamic SGS models for turbulence • Transport in chemistry simulations must depend on turbulent + laminar fluid transport, not on laminar transport alone

10. Chemistry Simulation Plans • Resolved Chemistry vs. Flamelets • Flamelets • assumes diffusion flame, • Resolved chemistry • makes no assumption of flame structure • thus resolved chemistry is more suitable for an autoignition flame • FlameMaster has been or will be extended to support autoignition flame structure? • Flamelets • use FlameMaster, • Resolved chemistry • uses FlameMaster subroutine for chemical source terms • Flamelets • assumes a quasi equilibrium solution, thus suppresses certain transients. • (This can be either/both a strength or a weakness.) • speed and/or memory advantages • Flamelets feasible for coarser grids • Resolved chemistry • allows UQ assessment of flamelet model in Scramjet context. • Has value for Scramjet UQ analysis even if too slow to be feasible for most simulations • May not be feasible for HyShot II configuration

11. Simulation Plans: Experimental Regime • Mixed fluid physics • Add SGS models (replace Smagorinsky) • Accurate multifluid viscosity, diffusion parameters • Diffusion velocity • Numerical issues • Finer resolution grids • No need to track fronts • AMR needed? • Add boundary layer inflow conditions • Turbulent inflow needed (nozzle/cross flow)? • V&V for pure mixing • Add chemistry • V&V for resolved chemistry • Comparison to flamelet simulations • V&V for flamelets

12. Simulation Plans:HyShot II Regime • Work with autoignition version of FlameMaster • Add this capability if necessary • Compare to laboratory experimental regime and resolved chemistry simulations (V&V) • Simulate in representative flow regimes defined by the large scale MC reduced order model, both for failure conditions (unstart) and for successful conditions. • Provide improved combustion modeling to the MC low order model, for the next iteration of an MC full system search.

13. Preliminary Simulation Results:Mixing Only 3D simulation. 67% H2 mass concentration isosurface plot compared to experimental OH-PLIF image (courtesy of Mirko Gamba). The grid is 120 microns, 2 times coarser than the Intended fine grid mesh size.

14. Preliminary Simulation Results:Mixing Only Black dots are the flame front extracted from the experimental OH-PLIF image.

15. Preliminary Simulation Results:Mixing Only Velocity divergence plotted at the midline plane. Bow shock, boundary layer separation, barrel shock and Mach disk are visible from the plot.

16. Preliminary Simulation Results:Mixing Only H2 mass fraction contour plotted at the midline plane

17. Preliminary Simulation Results:Mixing Only Stream-wise velocity contour plotted at the midline plane

18. Preliminary Simulation Results:Mixing Only H2 mass fraction contour plotted at x/d=2.4

19. Preliminary Simulation Results:Mixing Only Stream-wise velocity contour plotted x/d=2.4

20. Preliminary Simulation Results:Mixing Only Mixture fraction plot courtesy of Catherine Gorle 0 represents Hydrogen,1 represents Air Mass fraction plot of our simulation 1 represents Hydrogen, 0 represents Air

21. Preliminary Simulation Results:Mixing Only Comparison between Smagorinsky model (left) and dynamic model (right) Mass fraction plot, using 240 micron grid

22. Preliminary Simulation Results:Mixing Only Comparison between 240 micron grid and 120 micron grid With dynamic model, mass fraction plot

23. Queries for Stanford • What is the status/need for autoignition in FlameMaster? • In the broken flame regime, with turbulence inside the flame, • what is used for the binary diffusion coefficients that drive the effective diffusivity of species k into the mixture? Laminar, from kinetic theory, or turbulent, from an SGS model? • Or are the SGS diffusion terms just a Fickean add on to the multicomponent diffusion? • In this case they should be dominant for most grids, and so the multicomponent theory of diffusion might not be needed? • References for the broken flame-autoignition regime?