Xiaori Liu

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All articles published by MDPI are made immediately available worldwide under an open access license. No special permission is required to reuse all or part of the article published by MDPI, including figures and tables. For articles published under an open access Creative Common CC BY license, any part of the article may be reused without permission provided that the original article is clearly cited. For more information, please refer to https://www.mdpi.com/openaccess.

1. Introduction The cylinder liner and piston ring form the most crucial friction pair in the engine, contributing 35–40% of its overall friction losses [1]. Therefore, in order to save energy, reduce emissions, and improve engine efficiency, it is important to reduce friction between the piston ring and the cylinder liner. The movement of the piston rings in the cylinder liners significantly affects the decrease in friction, lubricant consumption, and wear [2,3,4].