بررسی اثرات نفوذ مولکولی و غنی سازی با هیدروژن بر شعله‌ی چرخشی طبقه‌ای

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشگاه تربیت مدرس

2 گروه مهندسی مکانیک، دانشگاه شیراز

3 گروه تبدیل انرژی, دانشکده مهندسی مکانیک، دانشگاه تربیت مدرس، تهران، ایران

چکیده

در این مقاله مشعل طبقه­ ای کمبریج-سندیا به‌منظور بررسی اثرات نفوذ مولکولی در احتراق طبقه ­ای و پیش ­آمیخته، با افزودن دو مقدار مختلف هیدروژن به سوخت شبیه­ سازی شده است. برای این منظور دو مدل متفاوت در نظر گرفته شده که در مدل اول از فرض عدد اشمیت برابر یک برای تمام گونه­ ها و در مدل دوم از اعداد اشمیت متفاوت برای هر گونه‌ی شیمیایی استفاده شده است. نتایج حاصل نشان می­دهند که با افزودن هیدروژن در حالت طبقه­­ ای، نفوذ ترجیحی گونه ­های سبک­تر بر کسرجرمی هیدروژن به ویژه در نزدیکی سطح جسم پهن تأثیر می­گذارد و باعث افزایش 4 برابری مقدار محاسبه شده برای کسر جرمی این گونه می­شود. بنابراین نمی ­توان اثرات نفوذ مولکولی را در معادلات حاکم نادیده گرفت. در حالت پیش ­آمیخته هرچند نفوذ مولکولی تأثیر کمی بر غلظت گونه­­ ها دارد ولی همچنان بر توزیع دما موثر است. به‌طوری که با افزودن 40 درصد هیدروژن، دمای بیشینه افزایش 2 و 5 درصدی و میانگین دما افزایش 12 و 15 درصدی را به ترتیب در حالت­ های پیش ­آمیخته و طبقه­ ای نشان می­ دهند. به‌طور‌کلی، افزایش مقدار هیدروژن، ساختار شعله را به‌طور قابل‌توجه­تری تغییر می­دهد، به‌ویژه در مورد ناحیه بازچرخشی در بالای جسم پهن، که با افزودن هیدروژن کوتاه­تر می­ شود.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Investigating the effects of molecular diffusion and hydrogen-enrichment on methane-air stratified swirl flame

نویسندگان [English]

  • Amirreza Mohammadpour 1
  • Kiumars Mazaheri 1
  • Alireza Alipoor 2
  • Sajjad Rahimi 3
1 Tarbiat Modares University
2 Department of Mechanical Engineering, Shiraz University,, Shiraz, Iran
3 Energy conversion, mechanical engineering, tarbiat modares university, tehran, iran
چکیده [English]

In this article, Cambridge-Sandia stratified burner has been simulated by adding two different amounts of hydrogen to the fuel in order to investigate the effects of molecular diffusion in stratified and premixed combustion. For this purpose, two different models have been considered. In the first model, the Schmidt number is assumed to unity for all species, and in the second model, different Schmidt numbers have been used for each chemical species. The results show that by adding hydrogen in the stratified case, preferential diffusion of lighter species, affects the mass fraction of hydrogen, especially near the surface of the bluff body, and causes a 4-fold increase in the calculated value for its mass fraction. Therefore, molecular diffusion effects cannot be ignored in the governing equations. In the premixed case, although the molecular diffusion has little effect on the species concentration, it still is effective on the temperature distribution. By adding 40% of hydrogen, the maximum temperature increases by 2% and 5% and the average temperature increases by 12% and 15% in premixed and stratified cases, respectively. In general, increasing the amount of hydrogen changes the flame structure more significantly, especially regarding the recirculation zone above the bluff body, which becomes shorter with hydrogen addition.
.

کلیدواژه‌ها [English]

  • molecular diffusion
  • Schmidt number
  • Stratified swirl burner
  • stratified burner
  • hydrogen enrichment
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