The Rotating Liner Engine under Medium Loads and Speeds. Fuel economy benefit exceeds 10%
2022-01-0507
03/29/2022
- Event
- Content
- The Rotating Liner Engine (RLE) is a design concept where the cylinder liner of a Heavy Duty Diesel engine rotates by about 2-4 m/s surface speed in order to eliminate the piston ring and skirt boundary friction near top and bottom dead center. Based on testing results from our single cylinder RLE prototype (a converted four cylinder Cummins ISB 3.9 diesel) compared to a similar baseline, under idle conditions, the friction reduction is approximately 50 kPa in FMEP (friction mean effective pressure), which translates to about 40% for a complete engine. In this new set of experiments, we are comparing the RLE performance under load of up to about 7 bar IMEP (indicated mean effective pressure). It has been proven that the elimination of metallic contact between the compression rings and cylinder persists under up to 75 bar peak cylinder pressure and 1.5-2 m/s liner surface speed (283-383 rpm) for the 850-1150 rpm crankshaft speed. Additionally, the RLE FMEP is substantially reduced under load, which is a trend opposite to standard engines. Presumably, at idle the RLE cylinder and piston are cooler than the standard engine because the substantial heat dissipation by the metallic contact of the rings and skirts and liner does not take place. Under load however, the increased heat transfer from the combustion raises piston and rotating cylinder temperature, which reduces local lubricant viscosity and reduces mid stroke viscous losses as well as rotating liner parasitic losses. Furthermore, based on higher speed baseline engine data, it appears that there is also a reduction in the hydrodynamic piston terms. The reason is attributed to the increased lubricant film thickness at mid stroke, due to the combined effects of the liner rotation and the traditional wedge effects of the piston skirt and rings. This effect seems to more than compensate for the increase of the hydrodynamic parasitic friction of the liner rotation with engine speed (we have currently a constant 3:1 ratio of crankshaft to liner speed). The combined fuel economy benefit exceeds 10 % for medium loads and speeds.
- Citation
- Dardalis, D., ALHAJ ASAD, O., Basu, A., Hall, M. et al., "The Rotating Liner Engine under Medium Loads and Speeds. Fuel economy benefit exceeds 10%," SAE Technical Paper 2022-01-0507, 2022, .