مطالعه عددی حرکت گندم در داخل سیکلون جداکننده استرماند با استفاده از دینامیک سیالات محاسباتی

سیکلون‌ها از جمله جداکننده‌های گریز از مرکز هستند که به‌دلیل سادگی و هزینه‌های ساخت و نگهداری نسبتاً پایین مورد توجه قرار گرفته‌اند. بازده جمع‌آوری ذرات و افت فشار دو پارامتر کلیدی در عملکرد سیکلون‌ها می‌باشند. دینامیک سیالات محاسباتی (cfd) یک ابزار قدرتمند برای پیش‌بینی رفتار جریان در طیف گسترده‌ای از طراحی و شرایط عملیاتی است که با حل عددی معادلات ناویر استوکس درک بهتری از حل عددی آشفتگی می‌دهد. در این مطالعه از یک سیکلون استرماند بازده بالا برای مطالعه رفتار گندم در داخل سیکلون استفاده گردید. برای رسم شبکه مسئله از نرم‌افزار گمبیت و برای حل معادلات بقا از نرم‌افزار کد تجاری انسیس فلوئنت 15 بهره گرفته شد. با توجه به عدد ماخ زیر 0.3 جریان، حلگر بر پایه فشار و از مدل sstkω برای شبیه‌سازی آشفتگی جریان استفاده شد. با فرض رقیق بودن جریان گندم در داخل جریان هوا (کسر حجمی زیر 12%) فاز مجزا با ردیابی تعداد زیادی از ذرات از طریق میدان جریان محاسبه گردید. با توجه به اهمیت بالای میدان‌های فشار و سرعت و تاثیر مستقیم بر روی بازده عملکردی سیکلون، در سرعت‌های ورودی m s^-1 10، 12، 14، 16، 18 و 20 و نرخ جرمی جریان kg s-1 0.08 پارامترهای فشار استاتیک، فشار کل، سرعت محوری، سرعت مماسی، شدت آشفتگی و سایش با همدیگر مقایسه شد. همچنین بازده جمع‌آوری برای سرعت‌های فوق به‌دست آمد. نتایج نشان داد که با در نظر گرفتن تمامی شرایط سرعت ورودی m s^-1 16 بهترین عملکرد را دارا بود.

Numerical Study of Wheat Conveying in Separator Cyclone using Computational Fluid Dynamics

IntroductionCyclones are widely used to separate solid particles from the fluid phase. Due to the ease of construction, low running costs, and hardworking conditions at high temperatures, people apos;s interest in using cyclones is increasing day by day. Engineers are generally interested in two parameters to perform a complete evaluation of the design and operation of a cyclone. These parameters are the particle collecting efficiency and the pressure drop inside the cyclone. The precise prediction of the pressure drop in cyclone is very important which it is directly related to operating costs.Computational Fluid Dynamics (CFD) is a diversified tool for predicting flow behavior in a wide range of design and operational conditions. Numerical solution of NavierStokes equations is the basis of all CFD techniques, which is the result of fast computer upgrades and a better understanding of the numerical resolution of turbulence.Materials and MethodsRegarding preliminary experimental tests and understanding the fluid flow, the flow rate of 0.08 kg s1 was selected as the flow rate. Six levels of inlet velocities 10, 12, 14, 16, 18, and 20 m s1 were selected for understanding the effect of inlet velocity on the cyclone performance. The measurements were carried out using a hotair anemometer (TSI8484model with a resolution of 0.07 m s1 and an operating range of 0.125 to 50 m s1), and a pressure differential meter instrument (CPE310sKIMO model) with an accuracy of 0.1 Pa.The region is discretized as a finite volume in a set, called the region grid or mesh after discretization. For incompressible fluids, pressurebased and densitybased solvers are used, respectively. Regarding the velocity of the material entering the cyclone and low Mach number, a pressurebased solver could be used in this study.The shear stress transport model (SST) is a modified version of the kω 2equation model. This model combines the two turbulence kω and kε models. The Lagrangian discrete phase model in Ansys Fluent follows to the EulerLagrangian model.Defining the best type of boundary condition is important for solving the problem and extracting solving fields. The boundary conditions used in this study include the inlet velocity in the entrance of cyclone and output pressure in both the upper and lower output sections.Results and DiscussionIn the results section, the results are initially validated by experimental results. Then, the parameters relating to separation efficiency and pressure drop are discussed. Finally, the tangential and axial velocities are considered as important parameters in the cyclone performance.One of the important issues in the cyclones is the static pressure because it completely affects the phenomenon of separation in the cyclone. The velocities of 16 m s1 and 18 m s1 have a good potential for use as the base velocity of the inlet fluid to the cyclone. The velocity of 20 m s1 is not suitable for separation due to highpressure drop related to high static pressure.The separation efficiency in the cyclone was 92 to 99% at all levels, the highest separation efficiency of 99% occurred at the velocity of 16 m s1 and the lowest separation efficiency of 9% happened at the velocity of 20 m s1.An increasing trend in axial and radial velocities occurred and the highest tangential velocity occurring in the input section. Considering the working conditions, the inlet velocities of 10 m s1 to 16 m s1 are appropriate for the turbulence intensity viewpoint.Conclusions(1): The speeds 16 m s1 and 18 m s1 showed a good potential for use as a base velocity of the fluid to the cyclone.(2): The highest separation efficiency for the velocity of 16 m s1 (99%) and lower isolation efficiency was obtained at velocity of 20 m s1 (92%).(3): The velocities of 10 m s1 to 16 m s1 are suitable input rates from the point of view of turbulence intensity.(4): It is concluded that from the point of view of wear to the velocity of 10 to 16 m s1, practical use is possible, and the velocity of 18 m s1 and 20 m s1 require the reinforcement of the relevant sections.