Aysu ÖZDEN, Özgür BARAN, Mehmet AKSEL, Mehmet AK

SU2 GERÇEK GAZ MODELLERİNİN SOĞUK GAZ İTİCİSİ PERFORMANS TAHMİNLERİ

Soğuk gaz itki sistemleri 1960’lı yıllardan bu yana özellikle uyduların yörünge kontrolünde tercih edilen sistemler olmuşlardır.Yakıt tankındaki yüksek basıncın görev süresince azalması nedeniyle, tank içindeki yakıtta oldukça düşük sıcaklıklar gözlenmektedir. Ayrıca itici lülesinin çıkışında da, vakuma yakın basınçlara genleşen yakıtın sıcaklığı oldukça düşmektedir. Bu koşullar altında, itki sisteminin performansının tasarım sürecinde gerçekçi olarak tahmin edilebilmesi için, açık kaynaklı, sıkıştırılabilir akışkanlar için uygun bir hesaplamalı akışkanlar dinamiği aracı olan SU2’nun kullanılması kararlaştırılmıştır. Bu çalışmada, itki sisteminin doğası gereği karşılaşılan düşük sıcaklık ve basınç etkilerinin doğru modellenebilmesi adına, SU2’nun ideal gaz, van-der Waals ve Peng-Robinson gaz modelleri kullanılarak elde edilen performans tahminleri ile itici vakum odası performans test sonuçları karşılaştırılmıştır. İtici performans testleri için bu amaçla kurulan termal vakum odası test alt yapısı kullanılmıştır. İtici simulasyonları ve performans testleri, yakıt tankının nominal ve düşük sıcaklıkta koşulladırıldığı durumlar için yürütülmüştür. Elde edilen veriler, SU2 van der Waals gaz modelinin, her iki sıcaklık koşulunda da vakum odası performans testlerine en yakın sonuçları verdiğini göstermektedir.

Anahtar Kelimeler:

Soğuk gaz iticisi, Gerçek gaz modelleri, Vakum odası testi, SU2

SU2 REAL GAS MODELS’ PERFORMANCE PREDICTIONS ON A COLD GAS THRUSTER

Cold gas propulsion systems are preferred, especially for the altitude and trajectory control for satellites, since the 1960s. Both depressurizing the propellant in the propellant tank throughout the mission and the expansion occurring in the divergent part of the thruster nozzle are the reasons for observing very low temperatures and pressure at the outlet section. We have decided to use an open-source compressible CFD tool, SU2, in order to predict the performance of the propulsion system in the early design phase. The scope of this study is the comparison of the results of the vacuum chamber performance tests and the outcomes of unsteady simulations with SU2 using different gas models, including ideal gas, van-der Waals, and Peng-Robinson models. Then, the accuracy and performance of these models are evaluated for the extremely low temperature and pressure conditions. Thruster performance tests have been conducted in the thermal vacuum chamber test campaign at the specially built testing facilities. In order to simulate nominal and low-temperature operation conditions, a propellant tank is thermally conditioned to the predetermined values, and performance test parameters are used as the input for the CFD simulations. The obtained results showed that the van der Waals gas model is the most appropriate gas model for both cases and provides the most realistic results in terms of performance parameters.

Keywords:

Cold gas thruster, Real gas models, Vacuum chamber test, SU2,

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