نوع مقاله : علمی پژوهشی

نویسندگان

1 استادیار،پژوهشگاه هوافضا ، وزارت علوم تحقیقات و فناوری، تهران، ایران

2 دانشجوی دکتری، پژوهشگاه هوافضا ، وزارت علوم تحقیقات و فناوری، تهران، ایران.

چکیده

در این مقاله، به بررسی انتقال حرارت و فناشوندگی عایق­های حرارتی مورد استفاده در موتور و نازل پرداخته شده است. معادلات انتقال حرارت و جرم در دو بعد در یک نازل همگرا-واگرا در نظر گرفته شده است. برای حل این معادلات از روش حجم محدود و از روش ضمنی برای وابستگی زمانی استفاده شده است. معادلة تجزیه که به فرم آرنیوس نوشته شده با استفاده از روش رانگ-کوتا حل شده و چگالی و شار جرمی گاز تولیدی در هر گام زمانی بدست آمده است. همچنین، مدلی برای لحاظ نرخ پسروی ارائه شده است. اعتبار­سنجی مدل با نتایج تجربی رایز در عایق سیلیکافنولیک مقایسه شده و نشان از انطباق خوب نتایج حاصل از شبیه‌سازی با مشاهدات تجربی می­باشد. پس از صحه­گذاری نتایج بدست آمده به بررسی تأثیر ضریب تصحیح دمش پرداخته شده و نتایج نشان‌دهندة حائز اهمیت بودن این ضریب برای طراحی دقیق عایق‌های فناشونده است. ضریب تصحیح دمش باعث کاهش ضریب انتقال حرارت جابه­جایی، کاهش پسروی سطح و در نتیجه کاهش دمای پشت عایق می­شود. بنابراین، در مواردی که ضخامت عایق قابل توجه یا گرمای فناشوندگی عایق پایین باشد، این پارامتر می­تواند حائز اهمیت بوده و نتایج نهایی و در نتیجه طراحی نهایی را تحت تأثیر قرار دهد.

کلیدواژه‌ها

موضوعات

عنوان مقاله [English]

Effects of Blowing Correction Factor on Convection Heat Transfer Coefficient in Thermal Insulators Modeling

نویسندگان [English]

  • Zaheer Sabohi 1
  • Mohammad Razmjooei 2

1 Assistant Professor. Aerospace Research Institute, Ministry of Science, Research and Technology, Tehran, Iran.

2 Ph.D. Student. Aerospace Research Institute, Ministry of Science, Research and Technology, Tehran, Iran.

چکیده [English]

This paper investigates the heat transfers and ablation of thermal insulators used in motors and nozzles. The heat and mass transfer equations are considered in two dimensions in a convergent-divergent nozzle. The finite volume method and the implicit method for time dependence have been used to solve these equations. We used the equations finite volume method with implicit formulation for time dependency to solve equations. The reaction equation, which is written in the form of Arrhenius, is solved using the Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Also, we represent a model for the rate of recession. The validation of the model is compared with the experimental results in silica-phenolic ablation insulators and shows a good agreement of the simulation results with the experimental observations. After validation of the obtained results. The effect of the blowing correction coefficient has been investigated, the results show that this coefficient is very important for the accurate design of ablation insulators. The blowing correction factor reduces the convection heat transfer coefficient, reduces the surface recession, and thus, reduces the back temperature of the insulation. Therefore, in cases where the thickness of the insulation is significant or the heat of ablation is low. This parameter can be important and affect the final results and thus the final design.

کلیدواژه‌ها [English]

  • Ablation
  • Insulator
  • Reaction Equation
  • Blowing Correction Factor
  • Convection Heat Transfer Coefficient
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