Improving Heavy-Duty Engine Efficiency and Durability: The Rotating Liner Engine

The Rotating Linear Engine (RLE) derives improved fuel efficiency and decreased maintenance costs via a unique lubrication design, which decreases piston assembly friction and the associated wear for heavy-duty natural gas and diesel engines. The piston ring friction exhibited on current engines accounts for 1% of total US energy consumption. The RLE is expected to reduce this friction by 50-70%, an expectation supported by hot motoring and tear-down tests on the UT single cylinder RLE prototype. Current engines have stationary liners where the oil film thins near the ends of the stroke, resulting in metal-to-metal contact. This metal-to-metal contact is the major source of both engine friction and wear, especially at high load. The RLE maintains an oil film between the piston rings and liner throughout the piston stroke due to liner rotation. This assumption has also been confirmed by recent testing of the single cylinder RLE prototype. The rotating liner-head seal is the most challenging technical obstacle. A face seal design for this application has been extensively tested and verified with a test rig and a single cylinder, light-duty based, prototype RLE. This document describes the technical background of the RLE concept, summarizes the current progress and tests that confirm the assumptions behind this design, describes the model used to estimate the RLE efficiency benefits for real world heavy-duty applications, and describes the future heavy-duty multi-cylinder RLE prototype.