تاثیر دمای پیشگرم و میزان رقیق‌سازی بر میدان احتراقی و ترکیب محصولات در ‏احتراق ترکیبی ‏oxy-MILD‏ در یک محفظه‎ ‎آزمایشگاهی

نوع مقاله: مقاله پژوهشی

نویسندگان

1 گروه هوافضا، دانشکده علوم و فنون نوین، دانشگاه تهران

2 عضو هیات علمی/ دانشکده علوم و فنون نوین/ دانشگاه تهران

3 عضو هیئت علمی/دانشکده مهندسی هوافضا، دانشگاه صنعتی امیرکبیر

4 عضو هیئت علمی/ دانشکده مهندسی هوافضا، دانشگاه صنعتی شریف

چکیده

در این تحقیق، ترکیبی از دو تکنولوژی احتراق اکسیژنی و احتراق MILD در یک کوره آزمایشگاهی همراه با جت ­های موازی به ­صورت عددی مورد مطالعه قرار گرفته است. در این سیستم نوین، به­ کمک رژیم MILD، علاوه­ بر رفع برخی مشکلات احتراق اکسیژنی، NOx از ترکیب گازهای خروجی حذف شده و محصولات احتراق عمدتاً متشکل ­از H2O و CO2 هستند. در این پژوهش، میدان احتراقی به­ کمک دو ابزار محاسبات عددی و تحلیل WSR بررسی شده است. در تحلیل عددی سه­ بعدی، از روش RANS و مدل ε k- RNG و مدل EDC در شبیه­ سازی تقابل آشفتگی جریان و شیمی احتراق استفاده شده است. تاثیر پیش­گرم ­سازی و رقیق­ سازی به ­کمک CO2 بر میدان احتراق و ترکیب گازهای خروجی بررسی شد. با افزایش دمای پیش­گرم، تکانه جت افزایش یافته و در نتیجه­ آن بهبود یکنواختیِ توزیع دما در کنار افزایش انتشار CO مشاهده شد. همچنین، افزایش رقیق­ سازی، به­ کمک CO2 در شرایط ثابت ورودی، دمای بیشینه را کاهش  می­دهد. بررسی تاثیر شیمیایی حضور CO2 نشان­دهنده تقویت مسیر تشکیل CO از طریق رادیکال CH3O نسبت­به مسیر اصلی از طریق فرمالدهید است. با افزایش حضور CO2 در مخلوط، مسیر تولید CO از سمت اتان ضعیف­ تر و نقش رادیکال متیلن CH2(s) قوی­تر می­شود.

کلیدواژه‌ها


عنوان مقاله [English]

The effect of pre-heating and dilution level on the combustion field and ‎flue gas composition of an oxy-MILD combustion system in a ‎laboratory‏-‏scale furnace

نویسندگان [English]

  • Mohamad Hassan Moghadasi 1
  • Rouzbeh Riazi 2
  • صادق تابع جماعت 3
  • Amir Mardani 4
1 Department of Aerospace Engineering, Faculty of New Sciences and Technologies, University of Tehran
2 Department of Aerospace Engineering, Faculty of New Sciences and Technologies, University of Tehran
3 Board member/ Faculty of Aerospace Engineering, Amirkabir University of Technology
4 Board Member/ Faculty of Aerospace Engineering, Sharif University of Technology
چکیده [English]

In this study, oxy-combustion is numerically investigated under MILD conditions. This novel combination is ‎simulated in a laboratory-scale furnace with parallel fuel and oxidant jets and a recirculating flow. With nitrogen ‎removal from the oxidant stream, zero NOx emission for gaseous fuel systems is expected. Combustion field is ‎modelled using a well-stirred reactor and computational fluid dynamics. In the CFD modelling, RANS equations ‎are solved using RNG k-ε and EDC model is employed to model the turbulence-chemistry interaction. The effect ‎of oxidizer preheating and CO2 dilution on the combustion field as well as flue gas composition is investigated. ‎The results indicate that the flame maximum temperature does not experience a significant increase when the ‎preheat temperature rises, positively affecting the temperature distribution at the cost of CO emission which is a ‎direct consequence of higher recirculation and mixing rate. Also, a kinetic study on the chemical effect of CO2 ‎presence reveals that CO production path through CH3O radical is more strengthened compared to the main path ‎through formaldehyde when increasing the dilution level. When diluting the oxidant, methylene’s role become ‎more influential in CO formation than when pure oxygen is used, contributing to higher CO emission. CO2 defeats ‎CH4 and O2 to absorb the free H radicals, causing higher levels of CO production.‎

کلیدواژه‌ها [English]

  • Oxy-combustion
  • MILD combustion
  • CO2 dilution
  • Numerical analysis
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