SERBEST DİSPLEYSIRLI BİR STİRLİNG MOTORUNUN NODAL TERMODİNAMİK VE DİNAMİK ANALİZİ

Öz

Bu çalışmada, serbest displeysırlı Stirling motorlarının dinamik ve termodinamik özellikleri bir simülasyon programı hazırlanarak incelenmiştir. Simülasyon programının dinamik kısmı, güç pistonu, krank mili ve displeysırın hareket denklemlerini içermektedir. Termodinamik kısmında da 24 nodal hacme dayanan bir nodal analiz yapılmıştır. Çalışmada, bu motorları ilk harekete geçirmek için, displeysırın doğal frekansı olarak bir başlangıç hızı gerektiği görülmektedir. Motor çalışırken displeysır vuru olarak adlandırılan bazı ikincil titreşimler sergilemekte, bu durum iş ve güç üretiminde düzensizliklere sebep olmaktadır. Bu durum, displeysır kütlesi, çalışma maddesi kütlesi, harici yük ve yay sabiti gibi bazı çalışma parametreleri değiştirilerek en aza indirilebilir. Çalışma maddesi şarj basıncının her bir değeri için farklı bir yaya ihtiyaç duyulmaktadır. Aynı yay sabiti değeri için, displeysır kütlesi sınırlı bir aralıkta değiştirilebilmektedir. Displeysır kütlesi azalırken motorun termal performansı artmaktadır. 1000 K sıcak uç sıcaklığı ve 356 K soğuk uç sıcaklığı arasında ve 18 bar şarj basıncında çalışan bir motor için efektif termik verim %21-26 arasındadır. 3,5 litre toplam iç hacme sahip bir motor, 3,9 kW efektif güç ve 4,7 kW indike güç üretebilmektedir. Motor performansı ile faz açısı arasında güçlü bir ilişki olduğu görülmektedir.

Anahtar Kelimeler

• Serbest displeysır
• Stirling motoru
• Dinamik ve termodinamik simülasyon
• Performans tahmini
• Displeysır kütlesinin optimizasyonu
• Yay sabitinin optimizasyonu

NODAL THERMODYNAMIC AND DYNAMIC ANALYSIS OF A FREE DISPLACER STIRLING ENGINE

Öz

In this study, the dynamic and thermodynamic features of free displacer Stirling engines were investigated by preparing a simulation program. The dynamic component of the simulation program involves the movement equations of power piston, crankshaft and displacer. The thermodynamic component is a nodal analysis based on 24 nodal volumes. The study indicates that starting these engines requires an initial speed is required as the displacer system natural frequency. While the engine is running, the displacer exhibits some secondary vibrations (named as beatings) and causes irregularities in its work and power generation however, it can be minimized by changing some working parameters such as displacer mass, working fluid mass, external loading, spring constant etc. For each value of the working fluid charging pressure, a different spring is needed. While the spring constant is the same, the displacer mass can vary in a limited range. The thermal performance of the engine increases as the displacer mass is decreasing. For an engine working between 1000 K heater temperature, 356 K cooler temperature and 18 bar charging pressure, the effective thermal efficiency ranges between 21 and 26 %. An engine with a 3.5 liter total inner volume is capable of generating about 3.9 kW effective power and 4.7 kW indicated power. A strong relation is observed between engine performance and phase angle.

Anahtar Kelimeler

• Dynamic and thermodynamic simulation
• Free displacer Stirling engine
• Performance prediction
• Optimization of displacer mass
• Optimization of spring constant

Kaynakça

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