MODELING OF ENTRAINED-FLOW COAL GASIFICATION BY AN EQUILIBRIUM EULERIAN-EULERIAN TWO-PHASE FLOW FORMULATION

Kömür tozu gazlaştırılmasının sayısal simülasyonu için, iki-fazlı akışın Euler-Euler formülasyonuna dayanan bir matematiksel model önerilmiştir. Halihazırda incelenen yaklaşım, gaz fazını Euler ve parçacık fazını Lagrange referans sistemi ile işlemekte ve genellikle kullanılmakta olan Euler-Lagrange yöntemlerinden farklı olarak, iki faz için de Euler tanımını kullanmaktadır. Bizim uygulamamızda, fazlar arasında mekanik ve termik denge kabulü ile model sadeleştirilmiştir. Bu sadeleştirme, parçacık fazının karışımın bir bileşeni olarak göründügü, ve sadece tek bir takım momentum ve enerji denklemlerinin çözümünü gerektiren bir formülasyonu mümkün kılmaktadır. Model, validasyon için, deneysel verilerin ve başka yazarların Euler-Lagrange neticelerinin mevcut olduğu bir probleme uygulanmıştır. Deneylerle ve diğer yazarların Euler-Lagrange hesaplarıyla yapılan karşılaştırmalar mevcut Euler-Euler yaklaşımının Euler-Lagrange modeli ile mukayese edilebilir bir hassasiyet sağladığını ve değişen çalışma koşulları altındaki trendleri benzer şekilde öngörebildigini göstermektedir. Önerilen Euler-Euler formülasyonu, buna ek olarak, konvansiyonel Euler-Lagrange formülasyonuna kıyasla, sayısal olarak daha sağlam olduğu ve daha iyi yakınsama özellikleri gösterdiği için, kömür tozu gazlaştırıcılarının sayısal simülasyonunda ilgi çekici bir seçenek olarak kabul edilebilir

KÖMÜR TOZU GAZLAŞTIRILMASININ BİR DENGE EULER-EULERİKİ-FAZLI AKIŞFORMÜLASYONUİLE MODELLENMESİ

A mathematical model is proposed for the numerical simulation of entrained flow coal gasification, based on an Eulerian-Eulerian description of the two-phase flow. In contrast to the commonly employed EulerianLagrangian procedures, which treat the gas phase by a Eulerian and the particulate phase by a Lagrangian frame of reference, the presently investigated approach applies a Eulerian description to both phases. In our implementation, the model is simplified assuming a mechanical and thermal equilibrium between the phases. This leads to a formulation, where the particulate phase appears, merely, as a species of a mixture, for which a single set of momentum and energy equations needs to be solved. For validation, the model is applied to a case, where experimental data and Eulerian-Lagrangian results of other authors exist. Comparisons with the experiments and the Eulerian-Lagrangian prediction of other authors show that the present Eulerian-Eulerian approach provides a comparable accuracy to the Eulerian-Lagrangian modelling and can similarly predict the trends under varying operating conditions. Since the proposed Eulerian-Eulerian formulation is additionally numerically more robust and exhibit better convergence properties compared to the conventional Eulerian-Lagrangian formulation, it can be considered as an interesting alternative in the numerical simulation of entrained flow coal gasifiers

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