İki Serbestlik Dereceli Rotor-Hidrodinamik Yatak Sisteminin Kararlılığının Termal Etki Altında İncelenmesi

Year 2024, Volume: 16 Issue: 1, 304 - 319, 31.01.2024

Abdurrahim Dal

https://doi.org/10.29137/umagd.1404559

Abstract

Hidrodinamik yataklar dönel mekanik sistemlerin önemli bir elemanı olup, birçok makinada tercih edilmektedir. Ancak rotorun yüksek hızlarda ve ağır yükler altında çalıştırıldığı durumlarda, yatak-rotor sistemi, yağın ısınması sebebiyle önemli rotordinamiği problemleri ile karşı karşıya kalmaktadır. Bu çalışmada hidrodinamik yatak ile desteklenmiş rotorun statik ve dinamik karakteristikleri ve sistemin kararlılığı, yağlayıcı viskozitesinin sıcaklığa bağlı değişimi dikkate alınarak sayısal olarak incelenmiş ve farklı radyal boşluk değerleri için termal durumun sistem karakteristikleri üzerindeki etkileri araştırılmştır. Yağlayıcının yatak ve rotor yüzeyleri arasındaki akışı Dowson denklemi ile değişken viskozite için modellenmiş ve pertürbasyon denklemleri 2 serbestlik dereceli bir sistem için türetilmiştir. Yağın sıcaklık dağılımı 3 boyutlu enerji denklemi ile modellenmiş, ve yatak ile yağ arasındaki ısı transferi modele dahil edilmiştir. Geliştirilen algoritma ile pertürbasyon denklemleri ve sıcaklık modelleri eş zamanlı olarak sonlu farklar şeması ile çözülmüş, farklı çalışma koşulları ve farklı paramterler için benzetimler gerçekleştirilmiş ve sistemin kararlılığı analiz edilerek kritik hız oranları ve kritik rotor ağırlıkları incelenmiştir. Termal etkinin sistemin statik ve dinamik performans üzerinde daha küçük radyal boşluk miktarına sahip hidrodinamik yataklar için daha baskın olduğu tespit edilmiş, sistemin kararlı bölgelerinin termal etki ile birlikte azaldığı görüşmüştür.

Keywords

hidrodinamik yatak, dinamik karakteristik, kararlılık analizi, pertürbasyon yöntemi

Investigation of the Stability of a 2-DOF Rotor-Hydrodynamic Bearing System Considering Thermal Effects

Abstract

Hydrıdynamic journal bearings that is an important machine element of mechanical systems are generally preferred in a lot of machines. However, when the rotor operates with heavy loads and high speeds, the bearing-rotor system is subject to crucial rotor dynamics problems due to heat generation into the lubricant. In this study, the stability of a hydrodynamic journal bearing-rotor system was investigated taking into consideration of thermal influences on the viscosity of the lubricant, as well as static and dynamic characteristics of the bearing. The lubricant flow was modelled with Dowson’s equation for variable viscosity, and the perturbation equations were derived for 2 degrees-of-freedom system. The temperature distribution of the lubricant was modelled with a 3D energy equation, and the heat transfer between the journal and lubricant was also included in this model. These mathematical models were numerically simultaneously solved with an algorithm based on a finite difference scheme, a serial simulation was performed for different parameters under operational conditions, and critical whirl ratios and critical mass were investigated by analyzing of the stability. It was determined that the thermal effects on the static and dynamic performance characteristics are more dominant when the radial clearance becomes smaller.

Keywords

hydrodynamic bearing, dynamics characteristic, stability analysis, perturbation method

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