A novel simulation method is proposed for predicting temperature field and ring-liner contact pressure for a given top piston ring design and given engine operating conditions. The method employs AVL Excite to predict the blow-by gas flow rate and pressure difference over the top piston ring. Further, Ansys CFX is used for predicting the 3-dimensional gas flow field past the top ring and the 3-dimensional temperature field in the top piston ring in a set of steady-state simulations at different engine crank angles. The time-averaged, 3-dimensional temperature field in the top piston ring is then predicted through a weighted average over the various crank angles. Finally the circumferential ring-liner contact pressure is predicted through the Ansys Simulation package, taking into account the computed time-averaged, 3-dimensional temperature field in the top piston ring. There are different design concepts for piston rings aiming to reduce thermal load and contact pressure variation. The above model was applied to compare a traditional straight-cut piston ring design against MAN Diesels' Controlled Pressure Release (CPR) design for the K90MC large bore, low- speed marine diesel engine. The results show that the ring with the straight-cut opening is heated on the inside near the opening due to the blow-by gas flow. This generates a strong thermal gradient which in turn reduces the ring-liner contact pressure near the ring opening and creates hard contact at the opening. This effect is significantly reduced for the CPR design since the blowby gas flow is then restricted to grooves resulting in a more even temperature field and a more even ringliner contact pressure. The predicted 3-dimensional temperature field was validated against piston-ring mounted thermo-plug measurements made by MAN Diesel for the CPR design. The simulation results were found to compare reasonably well with measured values. A set of hypothetical temperature fields were applied in Ansys Simulation in order to improve the understanding of factors affecting the ring-liner contact pressure. The results show that the most important factor is the temperature difference between the inside and the outside of the ring. The average temperature of the piston ring was found to be of minor importance to the ring-liner contact pressure.


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    Titel :

    Contact pressure and temperature prediction in a marine piston ring


    Beteiligte:


    Erscheinungsdatum :

    2010


    Format / Umfang :

    8 Seiten, 14 Bilder, 1 Tabelle, 1 Quelle


    Medientyp :

    Aufsatz (Konferenz)


    Format :

    Datenträger


    Sprache :

    Englisch




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