ÜÇ KATMANLI GÖZENEKLİ YAKICIDA ÖN KARIŞIMSIZ YANMANIN FLAMELET MODELİ İLE SAYISAL İNCELENMESİ

Year 2021, , 63 - 75, 30.04.2021

Tanju Ergen Tamer Şener Onur Tuncer Cihat Baytaş

https://doi.org/10.47480/isibted.979342

Abstract

Bu çalışmanın amacı üç farklı gözeneklilik yoğunluğuna sahip bir yakıcıyı sayısal olarak incelemektir. Bu kanalda ön karışımsız yanma, gözenekli katı ortam ile akışkan arasında ısıl denge olmadığı kabülü ile ısıl dengesiz enerji denklemleri kullanılarak modellenmiştir. Yanma modelinde akış ve yanma mekanizmaları flamelet tablolama modeli ile ayrılmıştır ve böylece hesaplama maliyeti düşürülmüştür. Metanın hava ile yanması GRI 3.0 mekanizması ile modellenmiştir. Üçünçü gözenekli katmanın zararlı gaz salımına etkisini gözlemlemek için, son katmanın 8-30 PPI aralığında değişen farklı gözeneklilik değerleri ile hesaplamalar yapılmıştır. Ek olarak, yakıcı gücünün ve fazla hava oranının yakıcıya etkisi de incelenmiştir. Hesaplamalar sonucunda sıcaklık dağılımı ve türlerin kütle kesirleri elde edilmiştir. Ön karışımsız yanmada tepkime tam oranlı şartlarda gerçekleşeceğinden yakıcı içerisindeki en yüksek sıcaklık her durum için benzer bulunmuştur. Yakıcının NOx ve CO salım değerleri uluslararası standartlar ile kıyaslanmıştır ve CO salımlarının her durumda standartların altında olduğu fakat NOx salımlarının sadece yüksek hava oranları ve ısıl güçler ile düşük çıktığı görülmüştür. Ek olarak üçüncü katmanın gözenek yoğunluğu (PPI değeri) düşürüldükçe zararlı gaz salım değerlerinin de çokça düştüğü görülmüştür.

Keywords

Gözenekli ortam, Yanma, Flamelet modeli, Isıl dengesiz model

NUMERICAL INVESTIGATION OF NON-PREMIXED COMBUSTION INSIDE A THREE LAYERED POROUS BURNER WITH FLAMELET MODEL

Abstract

Purpose of this study is to numerically investigate combustion within a porous channel, which has three layers with different pore densities. Non-premixed combustion inside the porous channel is modelled with thermal non-equilibrium energy equations. Flow and chemistry are decoupled with tabulated chemistry using flamelets, thereby reducing the computational cost. GRI 3.0 mechanism is used to account for methane/air combustion. Simulations are performed for different pore densities at the third layer in 8-30 PPI range. Also, the effects of thermal power and excess-air-ratio (EAR) are investigated for the porous burner. Temperatures and species mass fraction distributions are obtained. Maximum temperature in the burner found to be similar for all cases since combustion occurs in stoichiometric conditions at the flame front as a result of the non-premixed combustion model. NOx and CO emissions values of all simulations are compared against international gas emission standards. This comparison showed that while CO emissions are always below all international standards, NOx emissions are below these limits only for high values of excess air ratio and thermal power. Besides, as the pore density of the third layer is decreased, the values of emissions decrease strongly.

Keywords

Porous media, Combustion, Flamelet model, Thermal Non-equilibrium

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