Effects of lubricant fluid with nanoparticle additive on the load capacity of a hydrostatic journal bearing

Abstract

Hydrostatic journal bearings are recommended for supporting shafts operating at high speeds and under heavy loads in the industry. In the journal bearings, lubricant viscosity decreases with increasing temperature at high rotation speeds and hence, the fluid between the surfaces should be circulated by means of a pump in order to cool the lubricant. However, lubricant supplying between the surfaces at the high flow rate causes the whirl instability and vibrations problems in the bearing-shaft system. These instability problems give rise to significant damage on the system during operating at the high speeds and under the heavy loads. As a solution of this problem, it could be suggested to control the variation of the lubricant viscosity with respect to the temperature by adding nanoparticle. In the present work, the effects of the lubricant with nanoparticle additives on the load performance of a hydrostatic journal bearing are theoretically investigated. The fluid film flow between the bearing and rotor surfaces are modelled with Reynolds equation and viscosity term in Reynold’s equation is defined as a function which is depends on the nanoparticle properties. Then, the pressure distribution of the bearing is obtained with numerically solving the Reynolds equation and the load capacity is calculated for different nanoparticle parameters with using this pressure distribution. The results show that the usage of the lubricant with nanoparticle increase the load performance of the hydrostatic journal bearing.

Keywords

• Rotordynamics,load capacity,lubricant with nanoparticle,hydrostatic journal bearing

Nanoparçacık katkılı yağlayıcı akışkanın radyal hidrostatik yatağın yük taşıma kapasitesine etkisi

Abstract

Hidrostatik yataklar, endüstride, yüksek hızlarda ve ağır yükler altında çalışan şaftların yataklanması için önerilmektedir. Bu yataklarda, sıcaklığın artması akışkanın viskozitesini düşürmektedir ancak, akışkanın soğutulması için yüzeyler arasındaki akışkan, bir pompa ile devridaim ettirilebilir. Fakat yatak-şaft sistemlerinde, yüzeyler arasına akışkan iletilmesi, dolanım kararsızlıklarına ve titreşim problemlerine sebep olduğu bilinmektedir. Bu kararsızlık problemleri şaftın yüksek hızlarda dönüşü esnasında sisteme önemli hasarlar verebilecek kadar tehlikeli olabilir. Bu probleme çözüm önerisi olarak, yağlayıcı akışkanın viskozitesinin sıcaklığa bağlı değişiminin nanoparçacıklarla kontrol edilmes önerilebilir. Bu çalışmada da, hidrostatik yataklarda nanoparçacık ilaveli yağlayıcı akışkan kullanımının yük taşıma kapasitesine etkisi teorik olarak araştırılmıştır. Yüzeyler arasındaki akışkan hareketi Reynolds denklemi ile modellenmiş ve denklem içerisindeki viskozite terimi nanoparçacık özelliklerine bağlı olarak ifade edilmiştir. Bunun ardından, yatak içerisindeki basınç dağılımı Reynolds denkleminin sayısal çözümü ile elde edilmiş ve bu basınç dağılımı kullanılarak, yatağın yük taşıma kapasitesi, farklı nanoparçacık özellikleri için hesaplanmıştır. Yapılan bu çalışmanın sonuçları, nanoparçacık takviyeli yağlayıcı kullanımının hidrostatik yatakların yük taşıma kapasitesini arttırdığını göstermiştir.

Keywords

• Rotor dinamiği,yük kapasitesi,nanaoparçacık takviyeli yağlayıcı,radyal hidrostatik yatak

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