washing type capable of catching and removing the foreign particles at the same time. The lube oil filter before the turbocharger, therefore, always remains free of clogging and capable of catching the foreign particles efficiently, greatly contributing to the extension of turbocharger thrust bearing and journal beatng service lives. The usefulness of this lubricating oil system in extending the thrust bearing service life in particular can be seen from data shown in Fig.8.
Fig.8 shows the records of replacement made of thrust bearings in MET33SD turbochargers while in operation with 4-cycle dynamo engines during a period formo the late 1991 to the middle of 1995. What is obvious to see is that after the installation of the 500 mesh lube oil filter before the turbocharger, the thrust bearing service life by far increased in each instance. All this fully demonstrates that the lubricating oil system employing the 250 mesh engine lube oil filter and the 500 mesh continuous backwashing turbocharger lube oil filter in the common lubricating oil circuit is highly effective in extending the turbocharger thrust bearing service life in the high-pressure turbocharging operation.
5. CONCLUSIVE REMARKS
The trend with the diesel engines is definitely toward the higher output, which demands the turbocharger to do its part by devising necessary design improvements for high-pressure turbocharging required to support engine uprating.
Most immediately, the elevated compressor pressure ratio and turbocharger rotating speed require the rethinking about the durability of the compressor impeller and thrust bearing, among other turbocharger components. Devising cost effective ways to extend their service lives in the high-temperature and high-stress operating conditions is a pressing engineering challenge.
The authors are confident that the MET turbocharger technology consistently updated to this date will be further refined to even higher levels to turn out turbochargers that can compromising on its traditional emphasis on the product reliability.
