تحلیل عددی جریان هوای مرطوب در نازل همگرا-واگرا با مدل‌های ترمودینامیک تعادلی و غیر تعادلی

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه مهندسی مکانیک، واحد سنندج، دانشگاه آزاد اسلامی، سنندج، ایران

2 استاد، دانشکده مهندسی مکانیک، دانشگاه صنعتی امیرکبیر، تهران، ایران

چکیده

در این مقاله، حل عددی جریان تراکم‌پذیر، حدود صوت، گذرا، غیر لزج و دو فاز هوای مرطوب در نازل‌های همگرا-واگرا مورد مطالعه قرار گرفته است. برای انجام این کار، هر دو مدل ترمودینامیک تعادلی و غیر تعادلی با روش عددی ‏رو‏ در نظر گرفته شده و نتایج با هم مقایسه شده است. در مدل ترمودینامیک تعادلی حل عددی دارای دقت مرتبة سوم مکانی و دقت مرتبة دوم زمانی است اما در مدل ترمودینامیک غیر تعادلی، دقت مرتبه اول مکانی و دقت مرتبة دوم زمانی بکار گرفته شده است. برای جریان هوای مرطوب در ناحیه خشک، خواص اصلی فشار، دما و سرعت برون‌یابی شده، اما برای ‏ناحیه مرطوب (دو فاز)، کیفیت به جای فشار در مرز گره برون‌یابی شده است. در این تحقیق تأثیر هندسة نازل و شرایط سکون بر روی رطوبت خروجی از نازل و نرخ جوانه‌زایی مورد بررسی قرار گرفته است. نتایج نشان می‌دهد که با افزایش نرخ انبساط سطح نازل تقطیر زودتر رخ داده و همچنین نرخ جوانه‌زایی و رطوبت خروجی از نازل نیز افزایش می‌یابد. با وصف اینکه در مدل ترمودینامیک غیر تعادلی دقت مکانی مرتبه اول بکار گرفته شده است اما نتایج حاصل از این مدل تطابق بهتری با نتایج تجربی دارد.
 

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Numerical analysis of moist-air flow in converging-diverging nozzle with equilibrium and non-equilibrium thermodynamic models

نویسندگان [English]

  • Sabah Hamidi 1
  • Mohammad J. Kermani 2
1 Department of Mechanical Engineering, Sanandaj Branch, Islamic Azad University, Sanandaj, Iran
2 Department of Mechanical Engineering, Amir kabir University of Technology (AUT), Tehran Polytechnic.
چکیده [English]

In this paper, the numerical solution of compressible, transonic, unsteady, inviscid, and two-phase of moist-air flow in converging-diverging nozzles is studied. To do so, both equilibrium and non-equilibrium thermodynamic models with Roe's scheme are considered and the results are compared. In the equilibrium thermodynamic model, the solver is spatially third-order and temporally second-order accurate, but in non-equilibrium thermodynamic model, the solver is spatially first-order and temporally second-order accurate. For the moist air in dry regions the pressure, temperature, and velocity are extrapolated while in wet regions the steam quality has been used instead of pressure. In this study, the influence of the geometry expansion rate and inlet total temperature and pressure on nucleation rate and the wetness fraction at the nozzle exit are investigated. The results show that by increasing the expansion rate of the nozzle the condensation onset occurs earlier; also, the nucleation rate and wetness fraction at the nozzle exit is increased. Comparing the results of equilibrium and non-equilibrium thermodynamic models shows that the non-equilibrium thermodynamic model has better agreement with the experimental data.

کلیدواژه‌ها [English]

  • Roe's scheme
  • moist air
  • wetness fraction
  • equilibrium thermodynamic
  • non-equilibrium thermodynamic
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