Abstract




 
   

IJE TRANSACTIONS A: Basics Vol. 30, No. 10 (October 2017) 1583-1591    Article in Press

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  EFFECT OF BLADE DESIGN PARAMETERS ON AIR FLOW THROUGH AN AXIAL FAN
 
N. Rajabi, R. Rafee and S. Frazam-Alipour
 
( Received: April 18, 2017 – Accepted in Revised Form: July 07, 2017 )
 
 

Abstract    The objective of this paper is the numerical study of the flow through an axial fan and examining the effects of blade design parameters on the performance of the fan. The axial fan is extensively used for cooling of the electronic devices and servers. Simulation of the three-dimensional incompressible turbulent flow was conducted by numerical solution of the (RANS) equations for a model. The SST- k-ω and k-ε turbulence models are applied in the simulations which are done using CFX software. The comparison between available experimental data and simulation results indicates that the SST k-ω model gives more accurate results than the k-ε model. The results also show that in separation regions and vortices, the pressure will decrease. Hub area and blade root contain large vortices. The effects of changes in the blade geometry and the number of blades on the fan performance are studied in detail. For the primary fan model with the different number of blades (4, 5, and 6), the maximum mass flow rate of 800 CFM is obtained. Hence, the number of blades had negligible effects on the maximum flow rate. By 3o% decreasing in the chord of the blades, the maximum mass flow rate of the fan with the different number of blades (5, 6 and 8) will be reduced to 500 CFM. Therefore, in order to increase the maximum mass flow rate, the chord and the width of blades should be increased. On the other hand, by increasing blades from 4 to 6 in the primary model, the maximum outlet pressure has been increased by 32%. Furthermore, it was found that in high flow rates, an increment in the number of blades had no effect on the produced static pressure.

 

Keywords    Axial fan, simulation; Turbulent flow; Number of blades; Rotational speed

 

چکیده    هدف از این تحقیق تحلیل جریان عبوری از فن فروصوت محوری و بررسی پارامترهای طراحی پره آن است. فن های محوری کاربرد گسترده­ای جهت خنک سازی قطعات الکترونیکی و سرورها دارند. شبیه سازی جریان آشفته سه بعدی عبوری از فن با حل عددی معادلات متوسط زمانی ناویر استوکس برای یک فن صنعتی انجام شده است. شبیه سازی­ها در نرم­افزارCFX با مدل­های انتقال تنش برشی (SST k-ω) و مدل آشفتگی k-ε انجام شده است. از مقایسه داده­های تجربی و نتایج حل عددی مشاهده می­شود که نتایج مدل SST k-ω در این شبیه سازی دقیق­تر است. مشاهده می شود در نواحی تشکیل گردابه­ها فشار خروجی از فن کاهش پیدا می کند، نواحی هاب و پایه پره­ها بیشترین گردابه­ها را در بر دارند. همچنین تاِثیر تغییر اندازه پره­ها و تعداد آن­ها بر عملکرد فن مورد مطالعه قرارگرفته است. نتایج نشان می­دهد برای مدل اولیه با تعداد پره های 4 ، 5 و 6 حداکثر دبی جریان عبوری از فن برابر 800 فوت مکعب بر دقیقه می باشد، در نتیجه تعداد پره­ها تاثیری بر ماکزیمم دبی فن ندارد. با کوچکتر کردن وتر پره به اندازه 30 درصد مقداره اولیه در مدل ثانویه، حداکثر دبی خروجی از فن با تعداد پره های 5 ، 6 و8 به 500 فوت مکعب بر دقیقه کاهش می یابد، پس نتیجه می شود به منظور افزایش دبی جریان می بایست پره هایی بزرگتر با عرض و پهنای بیشتر طراحی کرد. از سوی دیگر افزایش تعداد پره منجر به افزایش فشار بیشینه خروجی می شود. در مدل اولیه با افزایش تعداد پره از 4 به 6 میزان فشار بیشینه خروجی به میزان 32 درصد افزایش یافته است. همچنین مشخص شد که در دبی­های بسیار زیاد افزایش تعداد پره تاثیری بر افزایش فشار خروجی ندارد.

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