İndüksiyon Eşlenikli Argon Plazmasında Akış Debisi ve Bobin Lokasyonunun Sistem Çalışma Parametrelerine Etkisi İle İlgili Simülasyonlar

Plazmatronların üretebildikleri yüksek sıcaklıktaki plazma sayesinde kullanım alanları gün geçtikçe artmaktadır. Yüksek sıcaklıktaki ve hızdaki plazma akışları kömür ve biyokütle atıklarının yakılması, gazlaştırılması, hava araçlarının atmosfere yeniden giriş koşullarının simüle edilmesi, ısı koruma malzemeleri üretimi, plazma metalürjisi, aşınma-kaplama uygulamaları ve bilimsel araştırmalar gibi pek çok yüksek sıcaklık teknolojisinde kullanılmaktadır. Teknik gereksinimleri karşılayacak plazmanın tanımlanabilmesi ve tanımlanan plazma isterlerinin, üretimden önce simülasyonları yapılarak incelenmesi, zaman, maliyet ve teknik risklerin asgariye indirilmesi açısından çok önemlidir. Bu çalışmada düşük basınçta indüksiyon eşlenikli Argon plazması (Inductive Coupled Plasma-ICP) ile ilgili simülasyonlar gerçekleştirilmiştir. Simülasyonda kullanılan RF frekansı 13.56 MHz, vakum değeri 1 Torr seçilmiştir. Bu vakum değeri atmosferik yeniden giriş deneysel uygulamalarına uygun olarak seçilmiştir. Çalışmada; gaz akışı simülasyonu, ısı transfer simülasyonu ve plazma simülasyonu eşlenikli olarak gerçekleştirilmiştir. Gaz akış miktarı (Q), düşük ve yüksek debi etkilerinin net gözlenebilmesi için iki farklı değer olarak, Q1=3 mg/s ve Q2= 90mg/s seçilmiştir. Simülasyonlarda toplamda 7 farklı kimyasal reaksiyon hesaba katılmıştır. Sistemde oluşan manyetik alan ve bunlara karşılık gelen elektrik alan çizgileri, manyetik alan büyüklüğü dağılımı, sıcaklık dağılımı, konvektif ısı akış dağılımı, gaz akış hız dağılımı, gaz basıncı değişimi değerleri ve elektron yoğunluğu dağılımı, iki farklı gaz debisi için simülasyonlarda hesaplanmış ve bu iki durum için söz bu değerler birbirleriyle karşılaştırılmıştır. Son olarak sistemi dalgalı-AC akım ile enerjilendiren indüksiyon bobinlerinin yeri simetri ekseni-z boyunca yukarıya, gaz çıkışına doğru kaydırılmış, bobinlerin yeri sistem geometrisine göre ortada ve sonda iken simülasyonlar yapılmıştır. Bu hesaplarda her iki durum için bobin elektriksel gücü ve akış kütle debisi sabit tutulmuştur. Ardından bobinlerin lokasyonundaki değişimin elektron yoğunluğu ve plazma gaz sıcaklığına olan etkisi 1-boyutlu ve 2-boyutlu dağılımlarla incelenmiştir.

Argon ICP Plasma Simulations Related to the Effect of the Gas Flow Rate and the Location of the Coils to the System Working Parameters

The usage areas of the plasmatron has been increasing due to the very high level of temperature which they can reach. They are used widely in the plasma-wind tunnels to create the atmospheric test conditions of high velocity aircrafts and spacecrafts while entering atmosphere. Additionally, most efficient coal and bio-mass burning also, syngas production from burning of the coal and biomass can be achieved with the high temperature plasmatrons. They are also used in the tests of high temperature resistance materials, plasma metallurgy and related scientific researches. The usage of simulation is very important to determination and verification for technical requirements of a plasma and plasmatron system before it's production, the time, cost and technical risks can be minimized before investing money to the production and development by simulating the related plasma system. In this work, a system that is consisted of inductive coupled plasma (ICP) is investigated by making related computer simulations. Investigated simulations are gas flow simulation, heat transfer simulation and plasma simulation and, these simulations are performed as coupled. In these simulations, the RF frequency is chosen as 13.56 MHz and vacuum pressure is chosen as 1 Torr. This vacuum level is selected appropriately for atmospheric re-entry experimental conditions. The mass flow rate is adjusted as a low and a high level, Q1=3 mg/s and Q2= 90 mg/s respectively. With these setting the changes of flow, heat and plasma parameters are investigated. Totally, 7 different chemical reaction is added to the realized simulations. The magnetic field distribution, the electric field induced from this magnetic field, the magnetic field magnitude, flow temperature distribution, convective heat transfer distribution, plasma gas velocity field, plasma gas pressure distribution and plasma electron density distribution is calculated in these simulations and, these results are compared for the different gas mass flow rate. Finally, the location of the coils which gives the RF electrical energy to the ICP plasma are slid to where the plasma gas is leaving from the geometry which respect to symmetry axis-z. The simulations are performed when the coils are in the middle and in the gas exit of the geometry. In these two different configurations, the power which this system is taken and mass flow rates are kept the same. These values are 3500 Watt and 90 mg/s respectively. Afterward with the change of the coils location, the plasma electron temperature and plasma gas temperature are investigated for 1-D and 2-D distribution and they are compared for discussion.

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Kaynak Göster