How is the turbocharger cooled and lubricated at high speed?

When the turbocharger on a vehicle is working, it has to withstand the impact of high-temperature and high-pressure exhaust gas from the engine. The speed of the turbine is generally over tens of thousands of revolutions, up to 200,000 revolutions per minute, and the temperature is as high as 900 to 1000 degrees Celsius. How is the turbocharger lubricated and cooled under such high operating temperatures and speeds?

The moving parts of the turbocharger, which are also the most core parts - the turbine impeller, compressor impeller and rotor shaft, have high-speed relative motion with the supercharger housing. Ordinary bearings cannot withstand this speed, so the bearing of the supercharger is a special floating bearing.

It is actually a copper ring that is sleeved on the shaft and the housing, with gaps between the ring and the shaft and between the ring and the bearing seat. When the engine is working, a double layer of oil film is formed at these locations under the action of the oil pressure, and the rotor actually floats on the oil film and rotates at high speed.

Due to the extremely high speed and temperature, this part also has extremely high requirements for lubrication and cooling.

If the supercharger is not well lubricated and cooled, it will cause abnormal wear of the bearings, greatly shortening the service life of the bearings, increase the gap between the rotor and the housing, and allow some of the oil to enter the intake or exhaust pipe from this part, leading to serious oil burning failures.

Poor heat dissipation can cause oil coking or carbon deposits

In addition, poor heat dissipation will cause the engine oil to coke or deposit, further damaging the seal and lubrication of the supercharger, aggravating wear, and eventually causing the supercharger to leak oil or make abnormal noises, and in severe cases even get stuck.

In order to cool and lubricate the turbocharger, a special oil pipe is separated from the main oil channel of the engine lubrication system, so that the oil enters from the oil inlet on the supercharger intermediate body and flows out from the oil port on the bottom of the intermediate body to lubricate and cool the supercharger rotor and bearings.

In order to ensure good lubrication and cooling effects, the flow rate of this part of the oil is very fast and the flow rate is relatively large. In order to better cool the supercharger, some current models have added a water cooling device driven by an electronic water pump, which can continue to work for a few minutes after the engine is turned off to continue to dissipate heat for the supercharger and prevent the supercharger from overheating.

Due to the special cooling and lubrication method of the supercharger, there are certain requirements for the use of the supercharger. For example, do not run the engine at high speed immediately after starting a cold engine, do not run the engine at idle speed for a long time, do not shut down the engine immediately after running the engine at high load for a long time, do not step on the accelerator before shutting down the engine, etc.

In addition, the turbocharger must use high-quality fully synthetic engine oil to prevent poor lubrication or oil coking at high temperatures. When replacing the supercharger, a certain amount of engine oil must be injected into the supercharger to prevent the supercharger from burning due to lack of lubrication at the moment of engine start-up.