16593

16593

شبيه‌سازي عددي جريان در كمپرسور جريان محوري مادون صوت با كاربرد جداره‌هاي بهبوددهنده‌ي پره‌هاي به عقب كشيده شده

كارشناسي ارشد

تبديل انرژي

فروردين 1395

دكتر محمد اخلاقي

مكانيك

ناپايداري‌هاي آيروديناميكي جريان در كمپرسورها به‌خصوص كمپرسورهاي صنايع هوايي يكي از مشكلات اساسي طراحان كمپرسورمي‌باشد. ازهمين رو يكي از ملاحظات اساسي در طراحي در نظر گرفتن حاشيه امن واماندگي كافي براي حالتي است كه شرايط مرزي نامساعد به كمپرسور اعمال ميگردد. اغلب ناپايداري هاي جريان در كمپرسورهاي جرييان محوري به شكل واماندگي دوراني رخ ميدهند كه از يك و يا چند سلول وامانده جريان تشكيل شده اند و قادر خواهند بود با توجه به‌سرعت دوراني پره‌ها، كمپرسور را با شيبي ملايم و يا تند به سمت از كار افتادگي كامل(كه اصطلاحا خفقان ناميده ميشود) ببرند. لحظه شكل گيري اين ناپايداري هاي چرخشي آغاز واماندگي است كه ميتوان با استفاده از روش هاي كنترل فعال و كنترل غير فعال آنرا به تأخير انداخت. يكي از روش هاي كارآمد استفاده از جداره هاي بهبود دهنده در كمپرسورهاي جريان محوري مي‌باشد كه در اين پايان نامه مورد بررسي قرار گرفته اند

1395/11/23

5/5/2019 12:00:00 AM

One of the main challenges in designing compressors, particularly aviation industry’s compressors, is the aerodynamic flow instability. Thus, one of the most crucial design considerations is to consider the sufficient stall safe margin in circumstances where unfavorable boundary conditions are exerted to the compressor. In this research, a method called precursor-suppressed stall using the casing treatment is employed. In such a method, the safe margin achieved with the casing treatment can be eva​luated by creating a number of precursor-suppressed stalls. Firstly, an appropriate numerical method is presented in order to determine the stall inception. Then, effects of the casing treatment on the compressor performance are assessed. The performance of the casing treatment in different percentages of the exposure of the rotor’s axial chord (33.3, 43.4 an​d 53.5%) is investigated through experimental tests. Two types of casing treatment are eva​luated for aforementioned three exposure percentages. The best results in terms of the compressor performance were achieved for the 53.5% exposure of rotor’s axial length. The recessed vane casing treatment leads to significant stall margin improvement, without sacrificing the efficiency. Stall formation an​d subsequently the compressor performance strongly depend on the type of casing an​d the exposure percentage of the axial chord of rotor’s blade. Most flow instabilities in compressors occur as rotating stalls. In fact, a rotating stall is composed of one o​r more stall cells which are able to cause a rapid o​r slow compressor failure, depending on the rotational speed of blades. Thus, the stable region for the compressor performance is determined in order to eva​luate the meshing quality of the computational domain. Then, the steady-state numerical simulation of flow is conducted for the first stage with inlet guide vanes. The comparison can reveal an acceptable agreement between experimental an​d simulation results.