To understand a turbocharger you must first take into consideration the workings of an internal combustion engine. An internal combustion engine is basically an air pump that turns thermal energy into kinetic energy. The more fuel the engine is able to burn, the more power it will make.
A turbocharger works by taking wasted exhaust gases, and using them to pump more air into the combustion chamber, which allows for more fuel to be burned.
The basic anatomy of a turbo is a turbine wheel and compressor wheel connected by a shaft. The turbine wheel is placed in the path of exhaust gases which are used to spin the assembly. As the turbine spins, the compressor draws in air from the atmosphere and compresses it. That compressed air is then forced into the engine’s combustion chambers.
The shaft is supported by specific bearings designed to deal with the extreme speed (70,000 to 250,000 rotations per minute) and heat of the turbocharger assembly (650 to 1050 degrees C). Most common is a journal bearing which encases itself in a layer of oil during operation to drastically reduce friction, and carrying heat away from the assembly. The other kind of bearing used in turbochargers is the ball bearing. This kind of ball bearing is precisely manufactured to work in such extreme conditions, and further reduce friction within the turbocharger. The axial load of the shaft assembly is supported by a thrust bearing and thrust collar which feature additional oil passages to further increase the durability of the system. On either side of the assembly (turbine and compressor) there is a set of piston rings which help to keep oil where it is most needed, and to keep hot exhaust gases and compressed air from entering.
The amount of air pressure the engine can be regulated by a device called wastegate. When the desired boost pressure is reached, the wastegate will open and vent exhaust gases to prevent further build up of boost. On internally wastegated turbos the actuator can be previous calibrated to change when, and how much the wastegate will open relative to boost pressure.
Careful consideration should be taken into the servicing and maintenance of a turbocharger. The assembly is very sensitive to things such as contaminated oil, and improper operation that can greatly shorten the life of a turbocharger, or even cause outright failure. Proper care should be taken towards general maintenance of the engine such as regular oil, oil filter, and air filter changes which will insure a long service life.