Open inspection was performed after fine runout was observed at a part of metal tip as the accumulation of the load was about 72 hours. Cracks were found at the tip around bearing horizontal face and the inspection to prove generation of white metal damage by oil film pressure was performed. Please refer to Fig.23 for enlargement of bearing surface and result of liquid penetrating test.
This technology has been applied to designing and developing of main bearing not only for new engines but for the engines of existing ships. And these engines have shown great operational record so far, which verifies validity and reliability of this evaluation technology.
Demand for more powerful engines is expected to last, and higher technologies have to cope with the demand . For designing and development of advanced main bearings, the evaluation technology described in this paper should be utilized to maintain high reliability.
Fig. 23 Result of Bearing Surface Inspection
4. CONCLUSIONS
The following is the summary of establishment of technologies for measuring oil film pressure distribution and for evaluating innuence from bearing configuration, such as oil groove, by testing in scale model of diesel engine bearing under fluctuating load.
(1) Measuring technology for high oil film pressure is established by elemental test with newly developed highly re-sponsive sensor to detect axial force strain. With this sensor, high oil film pressure in clearance of under 10mm can be measured.
(2) Loading of fluctuating load by simulation of actual unit is made possible by development of three dimensional bearing load test equipment which controls load and position.
(3) The maximum oil film pressure of approximately 100〜150MPa is measured in specimen bearing with bearing inner diameter of 300mm to prove high oil film pressure generation and fatigue failure by endurance test. In addition, oil film pressure reduction is achieved (reduced to 61MPa) by improvement of bearing, to verify oil film pressure distribution in bearing agrees with EHD analysis.
5. REFERENCES
[1] K. Furuno, "Improvement of Reliabillty for UEC Marine Diesel Engines" Mitsubishi Juko Giho Vol.34 No.4 1997 p.25 6-259
[2] S. Yoshihara and M. Okabe, 'The Main Bearing Behaviour of UEC Type Large Bore Diesels" CIMAC, 1995, D25
[3] T. Someya, "Entwicklung eines neuen Duennschicht Sensors zur Messung des Schmierfllmdruckes im Motorgleitlager." Motortech Z.Vol.58, No.2 p.110-116, 1997
[4] Conway-Jones. J. M. ,"Crankshaft Bearings : Advances in Predictive Techniques and Measurements in Engines." Pap Am Soc Mech Eng, p.12, 1984
