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Experimental Development of Apparatus to Measure Piston Assembly Friction in an Eco-mileage Vehicle Engine

Eco-mileage vehicles compete by running a fixed number of laps around a track within a given time. Judges calculate fuel efficiency (km/L), and name a winner. Reducing engine friction is an effective means for improving fuel efficiency. The piston assembly friction (the friction between the piston, the piston rings, and the cylinder liner) makes a significant contribution to the engine friction. So it is important to reduce the piston assembly friction. To measure the piston assembly friction against crank angle, we developed the friction measurement apparatus with the floating cylinder liner, by using parts of our eco-mileage vehicle engine as much as possible. Utilizing our apparatus, we investigated the effect of each piston ring on piston assembly friction. Results indicated that, compared to the three-ring set (with the top, second and oil rings), the two-ring set without the second ring (with the top and oil rings) reduced the friction mean effective pressure (FMEP) at all engine temperature and engine revolution. In the two-ring set without oil ring (with the top and second rings), the FMEP reduced with a lower temperature and revolution. However with a higher temperature and revolution, the FMEP in the two-ring set without oil ring was almost the same as that in the three-ring set, because the two-ring set without oil ring tended to increase the friction before and after both TDC and BDC where the piston speed decreased. The one-ring set with only top ring further reduced the FMEP with a lower temperature and revolution but increased the FMEP than the two-ring set without the second ring with a higher temperature and revolution.
Tematyka artykułu: Badania, diagnostyka, trwałość i niezawodność silników
Autor: Kohei Nakashima
Współautor(zy): Yosuke Uchiyama