Turbocharger Lubrication - Lubricant Behavior and Factors That Cause Turbocharger Failure

This paper is a review of the turbocharger lubrication system and at the same time an attempt to point out and analyze the factors responsible for turbocharger wear, damage and failures.
 In particular, the conditions under which the lubricant works are presented, from its entrance up to its exit from the turbocharger bearing housing. Additionally, the consequences of failure to comply with the instructions for appropriate turbocharger operation, are provided by the various manufacturers.
 Water cooled turbochargers (for which engine coolant is used), contribute significantly to the reduction of lubricant temperature, in the critical zones of its operation. This is achieved by reducing, the danger of oil “coking” effect (charred oil residues) or its decomposition, because of high temperature occurring in these zones. 
Turbochargers shaft support development using semi-floating bush bearings, has a significant impact on turbocharger manufacturing cost, as well as on their operational features. Further benefit may be had, when ball bearings are used (usually angular contact bearings are used) for turbocharger shaft support as they provide: a) a reduction of the kinetic friction coefficient, b) reduction of turbocharger lag during turbocharger shaft acceleration from low to high speeds, and c) reduced sealing problems.
 Regarding the failures that occur in turbochargers, their majority - up to 50% - is caused by problematic lubrication. The rest of the failures are divided between causes related to human factors (such as misuse and inadequate maintenance of a turbocharged vehicle) and external factors such as foreign objects entering either the compressor or turbine housings.

Ozet: Bu calisma turbosarj yaglamasinin bir degerlendirmesi ve ayni zamanda turbosarj gomlek, hasar ve bozukluklari icin olasi afaktorleri analiz etmek ve ortaya cikarmak icin bir girisimdir. Ozelde yagin calisma kosulu altindaki yagin girisinden turbosarjin yuvasindan cikisina kadar olan durumlar sunulmustur. Ek olarak turbosarj operasyonunun uygunlugu icin olan talimatlar ile bagdasmasi icin bozuklugun sonuclari cesitli ureticiler tarafindan saglanir.
Su sogutmali turbosarjlar (motor sogutmasi kullanilan) operasyonun kritik bolgesinde yaglama sicakliginin azaltilmasina katkida bulunur. Bu bolgelerde gorulen yuksek sicakliktan dolayi bu azaltilarak, yag ‘kok’lama etkisinin tehlikesi (yakilmis yag atigi) ya da onun dagilmasi tarafindan basarilir. Turbosarjlarin milleri onlarin operasyonel cehresinde oldugu kadar turbasarjer imalat maliyetinde de hatri sayilir bir etkiye sahiptir. Onlarin sagladigi gibi mil destegi icin top rulmanlari (genellikle acisal temasli rulmanlar kullanilir) kullanildigi zaman daha oteki yararlarina sahip olunabilir: a) kinetic surtunme katsayisinin bir azalmasi, b) turbosarjer mili dusukten yuksege ivmelenirken turbosarj gecikmesinin azalmasi ve c) azalan kapatma problemleri. Turbosarjlarda ortaya cikan bozukluklar, %50 ya kadar onlarin etkinligi problemik yaglamaya sebep olur. Bozuklugun geri kalani insanla r(bir turbosajli aracinin istismar edilmis ve yetersiz ozellikleri gibi) ve dissal faktorler (kompresore ya da turbine giren yabanci nesneler) arasinda donusturulur.