پیش‌بینی محدوده عدد پرانتل آشفته در احتراق متان-هوا با استفاده از مدل‌های مرتبه دوم شار اسکالر آشفته

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکترا-دانشکده مهندسی مکانیک-دانشگاه سمنان

2 استادیار دانشکده مهندسی مکانیک، دانشگاه سمنان

10.22034/jfnc.2019.92713

چکیده


هدف اصلی در تحقیق پیش­رو تخمین عدد پرانتل آشفته در احتراق غیرپیش­مخلوط متان-هواست. در این راستا، یک جریان احتراقی آشفته غیرپیش­مخلوط در شرایط استوکیومتریک، با استفاده از معادلات متوسط­گیری­شده رینولدز (RANS)، به­صورت عددی مورد تحلیل قرار گرفته ­است. برای مدل­ سازی تشعشع و آشفتگی جریان به­ترتیب مدل­ های جهات گسسته (DO) و k−ε ریلایزبل اعمال شده­اند. همچنین، برای مدل­ سازی احتراق آشفته از سه مدل اضمحلال گرداب ه­ای (EDM)، اضمحلال گرداب ه­ای مفهومی (EDC) و تابع چگالی احتمال (PDF) استفاده شده­ است. به ­همراه مدل EDM و EDC، مدل مرتبه دوم جبری GGDH و مرتبه بالای آن، یعنی HOGGDH، به­ همراه مدل پخش گرداب ه­ای ساده برای جمله شار حرارتی آشفته در معادله انرژی اعمال شده­ است. مقایسه نتایج عددی مدل SED با فرض پرانتل آشفته 85/0و مدل ­های مرتبه دوم با مقادیر تجربی موجود نشان می دهد که اعمال مدل­های مرتبه دوم شار حرارتی آشفته به­طور محسوسی منجر به اصلاح پیش­بینی توزیع دما در محفظه احتراق می­ شود. همچنین، توزیع NO    به­ دست­ آمده از مدل­ های مرتبه دوم مطابقت خوبی با مقادیر تجربی موجود دارد. براساس نتایج به ­دست آمده، در جریان احتراقی مقاله حاضر، مدل GGDH دارای دقت بالاتری نسبت به مدل HOGGDH در پیش­بینی دما و NO است. محاسبه عدد پرانتل آشفته در محفظه احتراق مورد بررسی نشان می­دهد که فرض عدد پرانتل 85/0 دور از واقعیت بوده و براساس مدل GGDH،  عدد پرانتل آشفته در نواحی مختلف از 25/0 تا 3/1 متغیر است. در نهایت عدد پرانتل آشفته 45/0 برای جریان احتراقی این پژوهش پیشنهاد شده است.

کلیدواژه‌ها


عنوان مقاله [English]

Prediction of turbulent Prandtl number in the methane-air combustion using a second-order turbulent scalar flux model

نویسندگان [English]

  • Ali Ershadi 1
  • Mehran Rajabi Zargarabadi 2
1 Semnan University
2 Department of Mechanical Engineering, Semnan University
چکیده [English]

The main objective of the present study is to estimate the turbulent Prandtl number in non-premixed combustion of methane-air. In this regard, a turbulent stream of non-premixed combustion in a stoichiometric condition, is numerically analyzed using the (Reynolds averaged Navier-Stokes) (RANS). For modeling the combustion, the Eddy Dissipation Model (EDM), Eddy Dissipation Concept (EDC) and Probability Density Function (PDF) have been applied. The k-ε Realizable model and Discreet Ordinate (DO) also was used for the turbulence modeling and radiation modeling, respectively. To the turbulent heat flux in the energy equation, second order algebraic model (GGDH and HOGGDH) with simple eddy diffusivity model has been applied. Comparing the results of the numerical model SED (with the turbulent Prandtl 0.85) and second order models with available experimental data show that applying the SO Models significantly led to the modification of predicting the temperature distribution in the combustion chamber. Moreover the NO derived from SO models distribution model has a good agreement with available experimental data. Calculation of Prandtl number turbulence in the combustion chamber shows that the assumption of Prandtl number of 0.85 is far from reality and based on GGDH model, Prt in different areas varies from 0.2 to 1.3.  Finally, the Prandtl number of 0.45 has been proposed for the non-premixed combustion of methane-air.

کلیدواژه‌ها [English]

  • Combustion modeling
  • Turbulent Prandtl Number
  • algebraic turbulent flux models
      S. R. Turns and S. J. Mantel, An Introduction to Combustion, Second Edition, New York, McGraw Hill, 2000.
2.   Y. Li, R. Li, D. Li, J. Bao and P. Zhang, “Combustion characteristics of a slotted swirl combustor: An experimental test and numerical validation,” International Communications in Heat and Mass Transfer, 66, 2015, pp. 140–147.
3.   S. Chouaieb, W. Kriaa, H, Mhiri and P. Bournot, “Presumed PDF modeling of micro jet assisted CH4-H2/air turbulent flames,” Energy Conversion and Management, 120, 2016, pp. 412-421.
4.   S. Li, Zh. Chen, X. Li, B. Jiang, Zh. Li, , R. Sun, Q. Zhu and X. Zhang,  “Effect of outer secondary-air vane angle on the flow and combustion characteristics and NOx formation of the swirl burner in a 300-MW low-volatile coal-fired boiler with deep air staging, Journal of the Energy Institute, 90, No. 2, 2017, pp. 239–256.
5.   E. Alemi and M. Rajabi-Zargarabadi, “Effects of jet characteristics on NO formation in a jet-stabilized combustor, International Journal of Thermal Sciences, 112, 2017, pp. 55-67.
6.   W. Fang and X. Xiang, “Effect of turbulence on NO formation in swirling combustor,” Chinese Journal of Aeronautics, 27, No. 4, 2014, pp. 797–804.
7.   L. X. Zhou and X. L. Chen, “Studies on the effect of swirl on NO formation in methan/air turbulent combustion,” Proceedings of the Combustion Institute, 29, 2002, pp. 2235–2242.
8.   K. Luo, J. Yang, Y. Bai and J. Fan, “Large eddy simulation of turbulent combustion by a dynamic Second-order moment closure model,” Fuel, 187, 2017, pp. 457–467.
9.   A. Scholtissek, F. Dietzsch, M. Gauding and C. Hasse, “In-situ tracking of mixture fraction gradient trajectories and unsteady flamelet analysis in turbulent non-premixed combustion,” Combustion and Flame, 175, 2017, pp. 243–258.
10. A. Irannejad, A. Banaeizadeh and F. Jaberi, “Large eddy simulation of turbulent spray combustion,” Combustion and Flame, 162, NO. 2, 2015, PP. 431-450.
11. B. J. Daly and F. H. Harlow, “Transport Equation in Turbulence,” Phys Fluids, 13, 1970, pp. 2634–2649.
12. B. E. Launder, “On the computation of convective heat transfer in complex turbulent flows,” Journal of Heat Transfer (ASME), 110, 1988, pp. 1112–1128.
13. K. Rup and P. Wais, “An Application of the K-e Model with Variable Prandtl Number to Heat Transfer Computation in Air Flows,” Heat Mass Transfer, 34, 1999, pp. 503-508.
14. Y. Y. Bae, “A new formulation of variable turbulent Prandtl number for heat transfer to supercritical fluids,” International Journal of Heat and Mass Transfer, 92, 2016, pp. 792–806.
15. J. H. Bae, J. H. Yoo and H. Choi, “Direct numerical simulation of turbulent supercritical flows with heat transfer,” Phys. Fluids, 17, 2005, pp. 105-104.
16. Y. Yamamotoa and T. Kunugi, “Modeling of MHD turbulent heat transfer in channel flows imposedwall-normal magnetic fields under the various Prandtl number fluids,” Fusion Eng. Des, 109, 2016, pp. 1130-1136.
17. R. J. Moffat and W. M. Kays, “A Review of Turbulent-Boundary-Layer Heat Transfer Research at Stanford.1958-1983,” Advances Heat Transfer, 16, 1984, pp. 241-365.
18. R. Jones, S. Acharya and A. Harvey, Improved Turbulence Modeling of Film Cooling Flow and Heat Transfer, Chapter 4: Modeling and Simulation of Turbulent Heat Transfer, edited by B. Sunden and M. Faghri, WIT Press, UK, 2005.
19. Y. Nagano and M. Shimada, “Development of a two-equation heat transfer model based on direct simulations of turbulent flows with different Prandtl numbers,” Physics of Fluids, 8, 1996, pp. 3379–3402.
20. P. M. Wikstrom, “Derivation and investigation of a new explicit algebraic model for the passive scalar flux,” Physics of Fluids, 12, 2000, pp. 688–702.
21. K. Abe and K. Suga, “Towards the development of a Reynolds-averaged algebraic turbulent scalar flux model,” International Journal of Heat and Fluid Flow, 22, 2001, pp. 19–29.
22. M. M. Rogers and N. N. Mansour, “Reynolds WC. An algebraic model for the turbulent flux of a passive scalar,” Journal of Fluid Mechanics, 203, 1989, pp. 77–101.
23. K. Suga and K. Abe, “Nonlinear eddy viscosity modeling for turbulence and heat transfer near wall and shear-free boundaries,” Int. J. Heat Fluid Flow, 21, 2000, pp. 37–48.
24. F. Bazdidi-Tehrani and M. Rajabi-Zargarabadi, “Application of second moment closure and higher order generalized gradient diffusion hypothesis to impingement heat transfer,” Transactions of The CSME, 32, 2008, pp. 91–105.
25. M. Rajabi-Zargarabadi and F. Bazdidi-Tehrani, “Implicit algebraic model for predicting turbulent heat flux in film cooling flow,” Int. J. Numer. Meth. Fluids, 64, 2010, pp. 517–531
26. L. Redjem-Saad, M. Ould-Rouissm and G. Lauriat, “direct numerical simulation of turbulent heat transfer in pipe flows: Effect of Prandtl number,” Int. J. of Heat and Fluid Flow, 28, 2007, pp. 847–861.
27. Ansys Fluent User’s Manual, Version 17, 2016.
28. J. O. Hinze, Turbulence, New York, McGraw Hill, 1975.
29. K. M. Saqr, M. A. Wahid, “Comparison of four eddy-viscosity turbulence models in the eddy dissipation modeling of turbulent diffusion flames,” Int. J. Appl. Math. Mech., 7, NO. 19, 2011, pp. 1–18.
30. X. Li, J. Ren and H. Jiang , “Application of algebraic anisotropic turbulence models to film cooling flows,” Int. J. of Heat and Mass Transfer, 91, 2015, pp. 7–17.
31. K. Suga, M. Nagaoka and N. Horinouchi, “Application of a Higher Order GGDH Heat Flux Model to Three-Dimensional Turbulent U-Bend Duct Heat Transfer,” Journal of Heat Transfer, Technical Notes, 125, 2003, pp. 200-203.
32. M. Hishida and Y. Nagano, “Structure of Turbulent Velocity and Temperature Fluctuations in Fully Developed Pipe Flow,” J. Heat Transfer (ASME), 101, 1979, pp. 15–22.
33. X. Li, “Application of algebraic anisotropic turbulence models to film cooling flows,” Int. J. of Heat and Mass Transfer, 91, 2015, pp. 7–17.