The Rotating Liner Engine (RLE) preliminary testing. 2019-01-0084
The Rotating Liner Engine (RLE) concept is a design concept for internal combustion engines, where the cylinder liner rotates at a surface speed of 2-4 m/s in order to assist piston ring lubrication. Specifically, we have evidence from prior art and from our own research that the above rotation has the potential of eliminating the metal-to-metal contact / boundary friction that exists close to the piston reversal areas. This frictional source becomes a significant energy loss, especially in the compression/expansion part of the cycle, when the gas pressure that loads the piston rings and skirts is high.
In 2005, our team published results of the friction testing of our first rotating liner test rig as compared to a baseline. This test rig was a single cylinder engine conversion of a light duty engine, but was tested only under motoring conditions. With warm coolant and oil, we proved a substantial friction reduction at low engine speeds which exceeded 40 kPa of FMEP. Additionally, the expectation that the friction spikes that typically exist in conventional engines close to piston reversal was proven.
The design details of our single cylinder prototype were described in SAE Paper 20012-01-1963. This prototype is based on the Cummins 4BT. Even though the prototype is also converted to single cylinder, the design allows for all cylinders to be converted to rotating liners. The critical details of the rotating liner face seal and the modeling involved that explore the operation under high cylinder pressure were described.
In 2014, the above prototype was constructed based on a mechanical injection Cummins 4BT, and after some additional development, it was made operational. This paper describes the constructed 4BT prototype and the preliminary observations from preliminary low load testing. The critical technical challenge, namely the rotating liner face seal, appears to be operating with negligible gas leakage and within the hydrodynamic regime for the loads tested, while peak cylinder pressures of the order of 80 bar have been recorded.
At the time of the abstract writing, detail fuel flow comparison at idle between the baseline engine (also a single cylinder converted Cummins 4BT) and the RLE has not been performed. However, while using the same injection pump and injection timing, it was observed that the peak cylinder pressure of the RLE at idle was considerably lower than the baseline, while the additional blowby was negligible. Based on the preliminary calculations, it appears that friction reduction of the same order of magnitude as the 2005 tests is taking place.
The above data, however, is preliminary. In the near future, we plan to record cylinder pressure along with fuel line pressure in order to document the difference of peak cylinder pressure and fueling duration at an identical idle speeds. We plan to also back this data up with instantaneous fuel flow. Then, we will progressively increase the load and record BMEP benefit of the RLE as a function of speed and load.
The target market for the RLE is heavy duty diesels. Based on our modeling predictions presented in 2012, we expect a fuel economy improvement in the heavy duty FTP cycle of the order of 7%.
Dimitrios Dardalis, Matthew Hall, Ron Matthews, Amiyo Basu, Tayyar Ozel
Rotating Sleeve Engine Technologies Inc., University of Texas-Austin
International Powertrains, Fuels & Lubricants Meeting