شبیه سازی گردابه های بزرگ جریان خنک کاری لایه ای تک مجرا و مجموعه سوراخ خنک کاری

نوع مقاله : مقاله پژوهشی

نویسندگان

1 دانشکده مهندسی مکانیک، دانشگاه سمنان.

2 دانشگاه صنعتی مالک اشتر

چکیده

در این مطالعه جریان خنک­کاری لایه­ای بر روی یک صفحه تخت به منظور بررسی اثرات به‌کارگیری مجموعه سوراخ بر اثربخشی خنک­کاری لایه­ای با استفاده از رهیافت RANS و LES شبیه­سازی شده است. هندسه­های مورد مطالعه شامل تک سوراخ استوانه­ای با قطر mm 1/11 و یک مجموعه سوراخ با 14 سوراخ استوانه­ای 97/2 میلی‌متری می­باشند، به طوری که سطح مقطع خروجی لوله خنک­کاری در هر دو حالت یکسان است. این مجموعه سوراخ به شکل ذوزنقه­ای چیدمان شده است. شبیه­سازی عددی در نسبت چگالی 6/1، نسبت طول به قطر 4، زاویه 35 درجه و نسبت دمش 25/1 صورت گرفته است. نتایج به دست آمده نشان می­دهند که جایگزینی یک تک سوراخ با مجموعه سوراخ شکل داده شده، منجر به افزایش قابل توجهی در اثربخشی خنک­کاری لایه­ای در هر دو جهت طولی و عرضی می­گردد، به طوری که افزایش در حدود 94 درصدی در میانگین سطحی اثربخشی خنک­کاری لایه­ای را در پی دارد. این افزایش در پی تغییر در ساختار گردابه­ها حاصل می­گردد. در مجموعه سوراخ خنک­کاری، مقیاس گردابه­های سنجاقی شکل کوچکتر از گردابه­های تک سوراخ است و شکل­گیری آنها در مکانی دورتر از سوراخ خنک­کاری صورت می­گیرد. در ساختار مجموعه سوراخ جفت گردابه­های anti-jet تشکیل می­شوند که جهت چرخش این گردابه­ها بر خلاف جهت CRVP است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Large eddy simulation of single and multi-holes of film cooling

نویسندگان [English]

  • Yaser Taheri 1
  • Mehran Rajabi Zargarabadi 1
  • Mehdi Jahromi 2
1 Faculty of Mechanical Engineering, Semnan University, Semnan, Iran
2 Malek Ashtar University of Technology, Tehran, Iran
چکیده [English]

  In this research, numerical studies have been performed by Reynolds averaged Navier Stokes (RANS) and large eddy simulations (LES) to investigate the effect of a novel film cooling design multi-holes on the film cooling effectiveness over a flat surface. A single cylindrical hole with 11.1 mm diameter and multi-holes (14 holes with a diameter of 2.97 mm) with fan configuration are considered for simulations. Numerical simulations are performed at a fixed density ratio of 1.6, length-to-diameter of 4, an inclined angle of 35o and blowing ratio 1.25. The results of the present study show that replacing a single hole with multi-holes results in a considerable increase in film cooling effectiveness in both axial and lateral directions, so that leads to an increase of about 94 percent in the area-averaged film cooling effectiveness. In the fan-shaped configuration, the scale of hairpin vortices is smaller than the single cylindrical hole, and forming of the vortices occurs in farther regions downstream of the hole. A pair of anti-jet vortices is formed in the structure of the multi-holes and the rotation direction of these vortices is opposite to the CRVP direction.
 

کلیدواژه‌ها [English]

  • film cooling
  • multi-holes
  • large eddy simulation
  • coherent structures
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