بررسی عددی اثر دمای اولیه بر اشتعال در جریان بدون لایه برشی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی هوافضا دانشگاه صنعتی امیرکبیر

2 دانشگاه صنعتی امیرکبیر

3 دانشگاه صنعتی شریف

4 دانشگاه صنعتی امیرکبیر، دانشکده مهندسی هوافضا

چکیده

در این مقاله، به بررسی فرایند اشتعال در جریان بدون لایه برشی پرداخته می‌شود. در چیدمان بدون لایه برشی دو جریان موازی با سرعت میانگین مساوی به یکدیگر می‌رسند. این چیدمان اجازه مطالعه دقیق شعله‌های لبه‌دار را فراهم می‌کند. هدف اصلی، بررسی اثر دمای اولیه جریان بر مرحله انتشار شعله در فرایند اشتعال است. این کار با استفاده از روش شبیه‌سازی گردابه‌های بزرگ، مدل احتراقی شعله ضخیم‌شده و سینتیک شیمیایی DRM-19 انجام شده است. سرعت محوری میانگین و نوسانی به­دست آمده از دو شبکه ریز و درشت با استفاده از نتایج تجربی اعتبارسنجی شده است. بررسی کسر مخلوط نیز نشان از مناسب­بودن دقت شبیه‌سازی‌ها در پیش‌بینی اختلاط دارد. مکان لبه ‌بالادست و پایین‌دست شعله نیز با نتایج  تجربی مقایسه شده و بیان‌کننده صحت شبیه‌سازی فرایند اشتعال است. سرعت میانگین انتشار شعله لبه‌دار نشان می‌دهد که با افزایش دمای اولیه از 323 به 1000 کلوین، سرعت انتشار شعله از 1 به 2/4 متربرثانیه افزایش پیدا می‌کند. همین روند برای رشد هسته شعله نیز وجود دارد. مقایسه بین سرعت انتشار شعله لبه‌دار به­دست آمده با سرعت انتشار شعله آرام و تصحیح شده آن با مجذور چگالی‌ها نشان می‌دهد که شعله آرام تصحیح ­شده بهترین نتیجه را در پیش‌بینی سرعت انتشار شعله لبه‌دار دارد. همچنین، افزایش دما سبب تبدیل شعله لبه‌دار دوگانه به شعله لبه‌دار سه‌گانه می‌شود.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Numerically investigation of the effect of initial temperature on the ignition in a shear-less mixing layer

نویسندگان [English]

  • Masoud EidiAttarZade 1
  • صادق تابع جماعت 2
  • محمد فرشچی 3
  • Mahmoud Mani 4
1 Aerospace Engineering Department Amirkabir University of Technology
2 Amirkabir University of Technology
3 Sharif University of Technology
4 Amirkabir University of Technology
چکیده [English]

Ignition process in a shear-less mixing layer has been studied in this paper. The effect of initial temperature on the flame propagation phase of ignition process is the main goal. The investigation is done by large eddy simulation method coupled with thickened flame approach and DRM_19 chemical mechanism. Mean and RMS axial velocities from both coarse and fine grids and mean mixture fraction have been validated against experimental results. Most upstream and downstream positions of flame edge are in good agreement with experimental. By increasing the initial temperature from 323 K to 1000 K, the mean edge flame propagation velocity increase from 1 to 4.5 m/s. The same trend exists for flame kernel volume. Comparison between calculated edge flame propagation velocity and laminar flame speed and its root density correction show that corrected laminar flame propagation can better predicts the edge flame propagation velocity. Also, by increasing the initial temperature, bibrachial edge flame convert to a triple flame

کلیدواژه‌ها [English]

  • Ignition
  • shear-less flow
  • Large Eddy Simulation
  • Thickened flame approach
  • Edge flame

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سابقه مقاله

  • تاریخ دریافت: 02 دی 1396
  • تاریخ بازنگری: 22 بهمن 1396
  • تاریخ پذیرش: 20 اسفند 1396

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