Large eddy simulations of fuel-air mixing in a trapped vortex combustor-effect of cavity length to depth ratio

Document Type : Original Article

Authors

School of Mechanical Engineering, University of Tehran

Abstract

Turbulent mixing in a trapped vortex combustor (TVC) is investigated using large eddy simulation (LES) coupled with filtered mass density function (FMDF). The impact of cavity length-to-depth ratio (L/D) as a crucial geometrical parameter on fuel-air mixing quality is evaluated in non-reacting flow conditions. The vortical structure analysis along with various quantitative measures such as mean cavity and near stoichiometric equivalence ratios, global fuel distribution and mixing efficiency curves are invoked to compare different L/D ratios. The predicted results show that increasing L/D ratio from 0.60 to 0.85 improves mixing quality within the cavity due to expanding the main vortex. Further increment of L/D ratio to 0.93 temporarily impairs the mixing quality, whereas more increasing this ratio to 1.00 leads to resumption of mixing quality improvement. Nevertheless, L/D=0.85 provides the best mixing curves and fuel distribution about mean cavity and near stoichiometric equivalence ratios, and consequently the best mixing quality. These findings are commensurate with expectations based on the vortical flow structures inside the cavity.

Keywords

Main Subjects

References

  1. D. Zhao, E. Gutmark, and P. de Goey, “A review of cavity-based trapped vortex, ultra-compact, high-g, inter-turbine combustors,” Prog. Energy Combust. Sci., 66, pp. 42–82, 2018.
  2. K. Hsu, L. Gross, D. Trump, and W. Roquemore, “Performance of a trapped-vortex combustor,” in 33rd aerospace sciences meeting and exhibit, Reno, NV, AIAA 95-0810, 1995.
  3. C. Stone and S. Menon, “Simulation of fuel-air mixing and combustion in a trapped-vortex combustor,” in 38th Aerospace Sciences Meeting and Exhibit, Reno, NV, AIAA 2000-0478, 2000.
  4. D. P. Mishra and R. Sudharshan, “Numerical analysis of fuel-air mixing in a two-dimensional trapped vortex combustor,” Proc. Inst. Mech. Eng. Part G J. Aerosp. Eng., 224, no. 1, pp. 65–75, 2010.
  5. K. K. Agarwal, S. Krishna, and R. V Ravikrishna, “Mixing enhancement in a compact trapped vortex combustor,” Combust. Sci. Technol., 185, no. 3, pp. 363–378, 2013.
  6. S. Krishna and R. V Ravikrishna, “Optical diagnostics of fuel–air mixing and vortex formation in a cavity combustor,” Exp. Therm. Fluid Sci., 61, pp. 163–176, 2015.
  7. Y.-Y. Liu, R.-M. Li, H.-X. Liu, and M.-L. Yang, “Effects of Fueling Scheme on the Performance of a Trapped Vortex Combustor Rig,” in 45th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Denver, Colorado, AIAA 2009-4831, 2009.
  8. S. Chen, R. S. M. Chue, J. Schlüter, T. T. Q. Nguyen, and S. C. M. Yu, “Numerical Investigation of a Trapped Vortex Miniature Ramjet Combustor,” J. Propuls. Power, 31, no. 3, pp. 872–882, 2015.
  9. A. Afshari, F. A. Jaberi, and T. I. P. Shih, “Large-eddy simulations of turbulent flows in an axisymmetric dump combustor,” AIAA J., 46, no. 7, pp. 1576–1592, 2008.
  10. G. Erlebacher, M. Y. Hussaini, C. G. Speziale, and T. A. Zang, “Toward the large-eddy simulation of compressible turbulent flows,” J. Fluid Mech., 238, pp. 155–185, 1992.
  11. F. Nicoud and F. Ducros, “Subgrid-scale stress modelling based on the square of the velocity gradient tensor,” Flow, Turbul. Combust., 62, no. 3, pp. 183–200, 1999.
  12. M. R. Visbal and D. V Gaitonde, “On the use of higher-order finite-difference schemes on curvilinear and deforming meshes,” J. Comput. Phys., 181, no. 1, pp. 155–185, 2002.
  13. S. Gottlieb, C.-W. Shu, and E. Tadmor, “Strong stability-preserving high-order time discretization methods,” SIAM Rev., 43, no. 1, pp. 89–112, 2001.
  14. C. W. Gardiner, “Handbook of stochastic methods for physics, chemistry and the natural sciences,” Appl. Opt., 25, p. 3145, 1986.
  15. F. A. Jaberi, P. J. Colucci, S. James, P. Givi, and S. B. Pope, “Filtered mass density function for large-eddy simulation of turbulent reacting flows,” J. Fluid Mech., 401, pp. 85–121, 1999.
  16. A. Singhal and R. V Ravikrishna, “Single cavity trapped vortex combustor dynamics–Part-1: Experiments,” Int. J. spray Combust. Dyn., 3, no. 1, pp. 23–44, 2011.
  17. B. H. H. Little and R. R. R. Whipkey, “Locked vortex afterbodies,” J. Aircr., vol. 16, no. 5, pp. 296–302, 1979.
  18. M. Esmaeili, A. Afshari, and F. A. Jaberi, “Turbulent mixing in non-isothermal jet in crossflow,” Int. J. Heat Mass Transf., 89, pp. 1239–1257, 2015.
  19. S. B. Pope, “Ten questions concerning the large-eddy simulation of turbulent flows,” New J. Phys., 6, no. 1, pp. 35–36, 2004.
  20. S. B. Pope and S. B. Pope, Turbulent flows, Second Edition, Cambridge university press, 2000.
  21. J. Fröhlich, C. P. Mellen, W. Rodi, L. Temmerman, and M. A. Leschziner, “Highly resolved large-eddy simulation of separated flow in a channel with streamwise periodic constrictions,” J. Fluid Mech., 526, pp. 19–66, 2005.
  22. N. Ramesh and J. M. Mallikarjuna, “Evaluation of in-cylinder mixture homogeneity in a diesel HCCI engine–A CFD analysis,” Eng. Sci. Technol. an Int. J., 19, no. 2, pp. 917–925, 2016.
  23. J. Boss, “Evaluation of the homogeneity degree of a mixture,” Bulk solids Handl., 6, no. 6, pp. 1207–1215, 1986.
  24. B. Wegner, Y. Huai, and A. Sadiki, “Comparative study of turbulent mixing in jet in cross-flow configurations using LES,” Int. J. Heat Fluid Flow, 25, no. 5, pp. 767–775, 2004.
  25. F. Muldoon and S. Acharya, “Direct numerical simulation of pulsed jets-in-crossflow,” Comput. Fluids, 39, no. 10, pp. 1745–1773, 2010.

Files

History

  • Receive Date: 19 August 2018
  • Revise Date: 27 October 2018
  • Accept Date: 31 October 2018

Share

How to cite

Statistics