مطالعه عددی تاثیر شرایط حرارتی دیواره و ساختار اکسنده بر ساختار شعله و رژیم احتراقی در کوره احتراق غیرپیش‌آمیخته

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشجوی دکتر مهندسی مکانیک دانشگاه کاشان

2 عضو هیات علمی دانشکده مهندسی مکانیک/ دانشگاه کاشان

3 دانشکده مهندسی مکانیک دانشگاه تربیت مدرس

10.22034/jfnc.2022.298945.1287

چکیده

هدف از مطالعه حاضر بررسی تاثیر شرایط حرارتی دیواره و ترکیب اکسنده روی ساختار شعله و محدوده تشکیل رژیم‌های احتراقی معمولی، دما بالا و بدون شعله است. بدین منظور کوره احتراق غیرپیش‌آمیخته دانشگاه لیسبون با استفاده از نرم افزار متن‌باز اپن‌فوم و همچنین محاسبات شیمیایی به کمک حلگر شعله نفوذی جریان متقابل بررسی شده‌اند. در مطالعه عددی از مدل‌های آشفتگی k-ε استاندارد، احتراقی مفهوم اتلاف گردابه اصلاح شده و تشعشعی DO همراه با ضرایب جذب و گسیل جسم خاکستری در شش طول باند مختلف استفاده شده است. مطابق با نتایج، تغییر ترکیب اکسنده و شرایط حرارتی دیواره، مسیرهای واکنشی را تغییر می‌دهد. جایگزینی CO2 با N2 درون اکسنده و تلفات حرارتی سبب می‌شود تا بیشینه رادیکال هیدروکسیل کاهش یافته و با افزایش فاصله محوری آغاز واکنش‌های شیمیایی، تاخیر در اشتعال افزایش یابد. عامل اصلی تغییر ساختار شعله با جایگزینی CO2 با N2 در رژیم‌های معمولی و بدون شعله همراه با اتلاف حرارتی به­ترتیب اثرات فیزیکی از طریق واکنش‌های O+HO2⇌OH+O2، O+CH4⇌OH+CH3 و 2OH⇌O+H2O و اثرات شیمیایی به وسیله واکنش‌های H+O2⇌O+OH و H+OH+M⇌H2O+M اند. در رژیم احتراق دما بالا سهم اثرات فیزیکی و شیمیایی روی ساختار شعله تقریبا برابر بوده و واکنش‌های O+H+M⇌OH+M، OH+CO⇌H+CO2 و OH+HO2⇌O2+H2O عامل کاهش هیدروکسیل اند.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical study of the effect of wall thermal conditions and oxidant structure on the flame structure and combustion regime in non-premixed combustion furnace

نویسندگان [English]

  • Mohammadamin Atarzadeh 1
  • seyed Abdolmehdi Hashemi 2
  • Esmaeil Ebrahimi Fordoei 3
1 Department of Mechanical Engineering, Kashan University, Isfehan, Iran
2 Department of Mechanical Engineering, Kashan University, Isfehan, Iran
3 دانشجوی دکترا دانشگاه تربیت مدرس
چکیده [English]

The aim of this study is to investigate the effect of wall thermal conditions and oxidant composition on the flame structure and map of combustion regimes. For this purpose, non-premixed combustion furnace of the Lisbon University has been investigated using the open source OpenFoam software as well as chemical calculations with the help of counter-flow diffusion flame solver. In numerical study, standard k-ε turbulence model, modified EDC combustion model, and discrete phase radiation model with the calculation of absorption and emission coefficients at six different wavelengths have been used. The results of simulations and kinetic calculations show that the change in oxidant composition and wall thermal conditions leads to changes in reaction pathways. Replacement of CO2 with N2 in the oxidant and presence of heat losses lead to fundamental changes in flame structure. The presence of wall heat loss, especially in conventional and flameless combustion regimes, leads to fundamental changes in the reaction pathways and alters flame structure, while the main contribution to the changes of flame structure is different physical and chemical properties of CO2 in comparison with N2 at conventional and flameless regimes, respectively. In the high temperature combustion regime, the contributions of physical and chemical effects are almost equal.
 
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کلیدواژه‌ها [English]

  • Non-premixed combustion
  • Combustion Regime
  • Oxidant Composition
  • Thermal Condition of Wall
  • Flame Structure
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