Читать книгу Turbo: Real World High-Performance Turbocharger Systems - Jay K Miller - Страница 17

The turbine shaft is supported by a bearing system that links the turbine to the compressor. The bearing system is housed inside of a bearing housing that contains many design features critical to proper turbo operation. The bearing system has a tough job. It must support the turbine and compressor wheels as they rotate to speeds in excess of 100,000 rpm while surviving various gyrations induced by engine pulses that vary with engine speed and power output. In addition, the bearing system must also absorb not just radial loads but thrust, or axial loads as well. When turbine pressure exceeds compressor pressure or vise-versa, there is thrust on the bearing system. Pressure differentials that become too severe will fail a good turbocharger.

The turbocharger bearing system is contained within the bearing housing. The bearing housing supports the turbine housing and compressor cover, while the turbine shaft and bearings support the rotational dynamics of the turbine and compressor wheels. Most turbocharger bearing systems are bronze type journal bearings that have oil passages to feed the hydrodynamic lubrication system, while many late-model high-performance turbos utilize specially designed ball-bearing cartridges.

While there are many types of bearing systems they all must do this job while providing a minimum of drag or frictional loss of energy extracted from the turbine to power the compressor. The bearing housing is also home to many more design features that include oil control, gas seals, heat dams, and, in some designs, water jackets to keep extremely high exhaust temperatures away from the lubricating oil.