شبیه‌سازی عددی احتراق غیرپیش‌آمیخته و تأثیر تغییرات نسبت دبی جرمی هوای همسو به سوخت بر پایداری شعله، راندمان احتراق و شاخص‌های آلاینده

حلمی, حامد; بخشان, یونس; ادیبی, پویان

doi:10.48311/mme.2026.119655.82988

شبیه‌سازی عددی احتراق غیرپیش‌آمیخته و تأثیر تغییرات نسبت دبی جرمی هوای همسو به سوخت بر پایداری شعله، راندمان احتراق و شاخص‌های آلاینده

نوع مقاله : مقاله پژوهشی

نویسندگان

حامد حلمی

یونس بخشان

پویان ادیبی

گروه مهندسی مکانیک، دانشگاه هرمزگان، بندرعباس، ایران

10.48311/mme.2026.119655.82988

چکیده

بهینه‌سازی عملکرد مشعل‌های غیرپیش‌آمیخته برای دستیابی همزمان به راندمان حرارتی بالا، انتشار پایین آلاینده‌ها و حفظ پایداری عملیاتی قوی، نیازمند ابزارهای پیش‌بینی دینامیک سیالات محاسباتی است که تعاملات آشفتگی-شیمی (TCI) در ریز مقیاس را با دقت مدل‌سازی کنند. مدل‌های متداول میانگین‌گیری رینولدز ناویر-استوکس اغلب در ثبت اثرات ریزمقیاس، برای پیش‌بینی تشکیل NOx حرارتی و پدیده‌های نزدیک به خاموشی دچار ضعف هستند. این مطالعه با به‌کارگیری یک رویکرد دوگانه عددی، یک حل‌کننده RANS تطبیق‌یافته را با چارچوب شبیه‌سازی بزرگ گردابه‌ها (LES) مجهز به مدل منیفولد تولید شده توسط شعله (FGM) و مکانیسم سینتیک GRI-Mech 3.0 جفت کرده و هر دو را در برابر داده‌های تجربی اعتبارسنجی می‌کند. این روش ترکیبی برای پیش‌بینی عملکرد یک مشعل هم‌جریان سوخت-هوا تحت تغییرات سیستماتیک نسبت جریان جرمی هوا به سوخت (MFR) استفاده شده است. تجزیه و تحلیل زمان-فرکانس نوسانات سیالاتی و ترمودینامیکی، یک ناپایداری هیدرودینامیکی غالب با فرکانس پایین (۱۰–۵۰ هرتز) را شناسایی کرد که به ریزش گردابه‌ها در ناحیه جدایش جریان مربوط می‌شود. نتایج کمی نشان داد که در حالی که جریان هوای همسو، راندمان تبدیل کربن را تا MFR=5 بالای 80٪ حفظ می‌کند و انتشار NOx را از طریق رقیق‌سازی حرارتی به شدت کاهش می‌دهد، افزایش نسبت رقیق‌سازی منجر به کاهش پایداری حرارتی و افزایش خطر نوسانات هیدرودینامیکی پایدار می‌شود. این رویکرد مدل‌سازی مقایسه‌ای، یک چارچوب پیش‌بینی قوی برای طراحی مشعل‌های صنعتی ایمن‌تر و کارآمدتر ارائه می‌دهد. مدل LES-FGM دقت برتری در ثبت TCI، مرزهای پایداری شعله و حساسیت NOx حرارتی نسبت به RANS، به ویژه در نواحی با کرنش بالا، نشان داد.

کلیدواژه‌ها

شبیه‌سازی گردابه‌های بزرگ (LES)

مدل‌سازی احتراق RANS

پایداری شعله غیرپیش‌آمیخته

مشعل جریان همسو

راندمان احتراق

شاخص انتشار آلاینده

اعتبارسنجی عددی

موضوعات

احتراق

عنوان مقاله English

Numerical simulation of non-premixed combustion and the effect of variations in the mass flow rate ratio of air to fuel on flame stability, combustion efficiency and pollutant indices

نویسندگان English

Hamed Helmi

Younes Bakhshan

Pouyan Adibi,

Mechanical Engineering Department, Hormozgan University, Bandar abbas, Iran

چکیده English

Optimizing the performance of non-premixed burners to simultaneously achieve high thermal efficiency, low pollutant emissions, and maintain robust operational stability requires computational fluid dynamics (CFD) predictive tools that accurately model turbulence-chemistry interactions (TCI) at the microscale. Conventional Reynolds-Averaging Navier-Stokes (RANS) models often suffer from poor capture of microscale effects for predicting thermal NOx formation and near-quenching phenomena. This study, employing a dual numerical approach, couples an adapted RANS solver with a large eddy simulation (LES) framework equipped with a flame-generated manifold model (FGM) and the GRI-Mech 3.0 kinetic mechanism, and validates both against experimental data. This combined approach is used to predict the performance of a fuel-air coflow burner under systematic variations in the air-to-fuel mass flow ratio (MFR). Time-frequency analysis of fluid and thermodynamic oscillations identified a dominant low-frequency (10–50 Hz) hydrodynamic instability related to the collapse of vortices in the flow separation zone. Quantitative results showed that while co-current airflow-maintained carbon conversion efficiency (CCE) above 80% up to MFR=5 and strongly reduced NOx emissions through thermal dilution, increasing the dilution ratio resulted in reduced thermal stability and increased risk of sustained hydrodynamic oscillations. This comparative modeling approach provides a robust predictive framework for the design of safer and more efficient industrial burners. The LES-FGM model demonstrated superior accuracy in capturing TCI, flame stability boundaries, and thermal NOx sensitivity compared to RANS, especially in high-strain regions.

کلیدواژه‌ها English

Large eddy simulation (LES)

RANS combustion modeling

non-premixed flame stability

co-flow burner

combustion efficiency

pollutant emission index

numerical validation

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