بررسی عددی تأثیر زائده سرمشعل بر اختلاط و واکنش سوخت و هوا

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه حرارت و سیالات، دانشکده مهندسی مکانیک، دانشگاه کیلان، رشت، ایران

2 گیلان*دانشکده فنی و مهندسی

چکیده

یکی از روش‌های بهبود اختلاط سوخت و هوا در یک شعله نفوذی گازی، تولید گردابه‌های هدفمند و ایجاد چرخش در جریان به کمک مانع سرمشعل است. در مطالعه حاضر، به بررسی عددی تأثیر شعاع، ضخامت و محل مانع جریان دیسکی‌‌شکل بر عملکرد یک مشعل نفوذی گازی با سوخت متان پرداخته می‌شود. این بررسی هم در شرایط اختلاط سرد و هم در شرایط اختلاط گرم (با فعالسازی واکنش احتراقی) انجام می‌پذیرد. صحت شبیه‌سازی حاضر از طریق مقایسه با اطلاعات تجربی ارزیابی می‌شود. نتایج حاکی از تأثیر محسوس پارامترهای مذکور بر بزرگی و قدرت گردابه‌های پایین‌دست مانع بوده و وابستگی مستقیمی میان وسعت گردابه‌های درونی و بیرونی و نرخ اختلاط سوخت و هوا مشاهده می‌شود. همچنین نتایج نشان می‌دهد حساسیت الگوی جریان و نرخ اختلاط سوخت و هوا به تغییر شعاع مانع در مقایسه با تغییر ضخامت آن بیشتر می‌باشد. بر اساس نتایج شبیه‌سازی‌های اختلاط گرم و با توجه به وابستگی نرخ واکنش شیمیایی به نرخ اختلاط آشفتگی، اختلاط‌های سریعتر سوخت و هوا با کاهش طول شعله همراه می‌باشد. از میان هندسه‌های مورد بررسی، مانع دیسکی‌شکل با شعاع 6 میلی‌متر، ضخامت 5 میلی‌متر و در فاصله 5 میلی‌متری از دهانه کانال هوا، بهترین نرخ اختلاط را موجب می‌شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical Investigation of the Influence of Burner’s Bluff Body on Air-Fuel Mixing and Reaction

نویسندگان [English]

  • Amin Asefi 1
  • Javad Mahmoudimehr 2
1 Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran
2 Faculty of Mechanical Engineering, University of Guilan, Rasht, Iran
چکیده [English]

One way to improve air-fuel mixing in a gas diffusion flame is to produce targeted vortices and circulate the flow using a bluff body. In this study, the influences of radius, thickness, and location of a disk-shaped bluff body on the performance of a methane gas diffusion flame are numerically studied. This investigation is carried out under both cold mixing and hot mixing (with combustion reaction) conditions. The present simulation is verified against experimental data. The results show the substantial influence of the mentioned parameters on the size and intensity of downstream vortices, and a direct dependence is observed between the sizes of inner and outer recirculation zones and air-fuel mixing. It is also observed that the flow pattern and level of air-fuel mixing are more dependent on the bluff body’s radius than its thickness. Based on the hot mixing simulation results and regarding the dependence between the rates of the chemical reaction and turbulence mixing, the higher rate of air-fuel mixing is associated with the decreased flame length. Among the cases investigated, the bluff body with a radius of 6mm, the thickness of 5mm, and axial location of 5mm away from the air channel exit results in the best air-fuel mixing.

کلیدواژه‌ها [English]

  • Gas diffusion flame
  • Bluff body
  • Air-fuel mixing
  • numerical simulation
[1] C.K. Law, Multicomponent Droplet Combustion, Combustion Physics, New York: Cambridge University Press (2006).
[2] J. Warnatz, U. Maas, R.W. Dibble, Combustion, Heidelberg: Springer (2006).
[3]J. Conti, et al. International energy Outlook 2016 with projections to 2040, Washington DC, USA (2016).[S1] 
[4] K. M. Kundu , D. Banerjee, D. Bhaduri, On flame stabilization by bluff- bodies, Journal of Engineering for Power, 102 (1980) 209-214.
[5] H. K. Ma, J. S. Harn, The jet mixing effect on reaction flow in a bluff-body burner,  International journal of   heat and mass transfer, 37(18) (1994) 2957-2967.‏
[6] R.W. Schefer, M. Namazian, J. Kelly, M. Perrin, Effect of confinement on bluff-body burner recirculation zone characteristics and flame stability, Combustion science and technology, 120(1-6) (1996) 185-211.‏
[7] I. Esquiva-Dano, H. T. Nguyen, D. Escudie, Influence of a bluff-body’s shape on the stabilization regime of non-premixed flames, Combustion and Flame, 127(4) (2001) 2167-2180.‏
[8] L.K. Sze, C. S. Cheung, C.W. Leung, Temperature distribution and heat transfer characteristics of an inverse diffusion flame with circumferentially arranged fuel ports, International Journal of heat and mass transfer, 47(14-16) (2004) 3119-3129.‏
[9] A. Sobiesiak, J.C. Wenzell, Characteristics and Structure of Inverse Flames of Natural Gas, Proceedings of the Combustion Institute, 30(1) (2005) 743-749.‏
[10] P. Hariharan, C. Periasamy, S.R. Gollahalli, Effect of Elliptic Burner Geometry and Air Equivalence Ratio on the nitric Oxide Emissions from Turbulent Hydrogen Flames, International Journal of Hydrogen Energy, 32 (8) (2007) 1095-1102.‏
[11] P. Kumar, D. Mishra, Effects of bluff-body shape on LPG–H 2 jet diffusion flame, International Journal of Hydrogen Energy, 33(10)  (2008) 2578-2585.
[12] H. S. Zhen, C. W. Leung, C. S. Cheung,  Thermal and Emission Characteristics of A Turbulent Swirling Inverse Diffusion Flame, International Journal of Heat and Mass Transfer, 53(5-6) (2010) 902-909.‏
[13] D. Ashoke, S. Acharya, Parametric study of upstream flame propagation in hydrogen-enriched premixed combustion: Effects of swirl, geometry and premixedness, International journal of hydrogen energy, 37(19) (2012) 14649-14668.‏
[14] S.A. Hashemi, N. Hajialigol, K. Mazaheri, and A. Fattahi, Investigation of the effect of the flame holder geometry on the flame structure in non-premixed hydrogen-hydrocarbon composite fuel combustion, Combustion, Explosion, and Shock Waves, 50(1) (2014) 32-41.
[15] M.M. Noor, A. P. Wandel, T. Yusaf., Analysis of recirculation zone and ignition position of non-premixed bluff-body for biogas MILD combustion, International Journal of Automotive and Mechanical Engineering, 8(1) (2013) 1176-1186.
[16] Z. Wang, et al., LES investigation of swirl intensity effect on unconfined turbulent swirling premixed flame, Chinese science bulletin 59 (33) (2014) 4550-4558.‏
[17] T. Yiheng, et al., Experimental Investigation on the Influences of Bluff-Body’s Position on Diffusion Flame Structures, ASME Power Conference (2017) POWER-ICOPE2017-3090.
[18] T. Yiheng, et al., Effects of the position of a bluff-body on the diffusion flames: A combined experimental and numerical study, Applied Thermal Engineering 131 (2018) 507-521.‏[S2] 
[19] S. F. Mousavi Kolousforoushi , J. Mahmoudimehr, Influence of Burner Head Design on Its Thermal and Environmental Characteristics,  AUT J. Mech. Eng., 2(1) (2018) 27-38.
[20] N. Peters, Turbulent Combustion, Cambridge University Press, Cambridge (2000).
[21] T. Poinsot, D. Veynante, Theoretical and Numerical Combustion, Edwards Press (2005).
[22] A.Bahari, K. Atashkari, J.  Mahmoudimehr, Multi-objective optimization of a municipal solid waste gasifier, Biomass Conversion and Biorefinery, (2020) 1-16.
[23] ANSYSFluent User's Guide, ANSYS, Inc. (2016). 
[24] A. Karl, J. Chi Hung Fung, An improved SST k− ω model for pollutant dispersion simulations within an isothermal boundary layer, Journal of Wind Engineering and Industrial Aerodynamics, 179 (2018) 369-384.
 [25] H. Sheikhani, H. Ajam, M. Ghazikhani, A review of flame radiation research from the perspective of factors affecting the flame radiation, measurement and modeling, The European Physical Journal Plus, 135(4) (2020) 343.‏
[26] F. Kulacki, Handbook of Thermal Science and Engineering, Springer, (2018).
[27] D. Poitou, M. El-Hafi, B. Cuenot, Analysis of Radiation Modeling for Turbulent Combustion: Development of a Methodology to Couple Turbulent Combustion and Radiative Heat Transfer in LES, Journal of Heat Transfer, American Society of Mechanical Engineers, 133(6) (2011) 062701.‏
[28] M. Rasouli, J. Mahmoudimehr,  Minimization of the Emission of Pollutants along with Maximization of Radiation from An Air-Staged Natural Gas Flame, Modares Mechanical Engineering 16 (7) (2016) 207-218 (in Persian).