PİSTONLU YARI-HERMETİK SOĞUTMA KOMPRESÖRÜ KRANK MİLİNİN SANKİ-STATİK YAKLAŞIMLA SONLU ELEMANLAR ANALİZİ

Yarı-hermetik soğutma kompresörleri, arıza durumunda kolay müdahale kolaylığı sağlarlar. Bu kompresörlerde kullanılan krank milleri hem hafif hem de dayanıklı olmalıdır. Bu sebeple, doğru tasarım ve doğru malzeme seçimi çok önemlidir. Bu kompresörler yüksek hızda çalıştığından, zamana bağlı dinamik analiz kaçınılmaz olmaktadır. Ancak bu yöntemle problem çözümü çok uzamaktadır ve yakınsama sağlamak zorlaşmaktadır. Özellikle yataklardaki yağ basıncı değişimi vs gibi yapıdaki tüm dinamik etkiler dikkate alındığında problem iyice karmaşıklaşmaktadır. Probleme hızlı ancak statik yaklaşımdan daha doğru bir çözüm elde etmek amacıyla bu çalışmada sanki-statik yaklaşım kullanılmıştır. Kinematik ve kinetik analiz sonucu elde edilen kuvvetler yapıya belli kabuller altında statik olarak uygulanmıştır. Ortaya çıkan maksimum gerilme krank milinin yağlama plakasına bağlanan ucundaki fatura dibinde olup, bu literatürdeki hasar örnekleriyle uyuşmaktadır. Analizler sonucunda atalet etkisi %1.7 civarında olup, ele alınan krank mili için sanki-statik yaklaşımın oldukça doğru bir yaklaşım olduğu gösterilmiştir.

Anahtar Kelimeler:

Yarı-hermetik, Kompresör, Krank Mili, Sonlu Elemanlar Yöntemi, Sanki-statik Yaklaşım, Atalet Kuvvetleri

Finite Element Analysis of Crankshaft of a Reciprocating Semi-Hermetic Compressor based on Quasi-Static Approach

Semi-hermetic compressors brings the advantage of easy repair in case of a breakdown. Crankshafts used in these compressors are required to be light-weight and durable at the same time therefore, a proper design along with a proper material selection becomes important. Due to high speed of operation, a transient dynamic analysis may become necessary for a proper evaluation of stresses and strains for the crankshaft. However, dynamic analysis is computationally demanding especially when all dynamic aspects are considered such as the influence of hydrodynamics of bearings etc. Considering only static part of the loading may be oversimplified approach for the problem. In this work, a quasi-static approach is used for the structural analysis of crankshaft by performing kinematic and kinetic analysis to determine forces with inertial effects included and then finite element analysis to determine stresses and deflections. As expected, the maximum stress occurs in the radius of shaft connecting to the bearing on oil spreader side. This is also verified in literature that fatigue cracks initiate at this site of crankshaft. The inertial effects are investigated in detail and approximately around 1.7% of the loading is due to inertial effect of piston and connecting rod. Therefore, it is anticipated that quasi-static approach provides sufficiently accurate results.

Keywords:

Semi-hermetic, compressor, crankshaft, Finite Element Method, Quasi-Static Approach, Inertial Forces,

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