The Adaptive Cycle Engine on Standard Duty Cycles 2019-01-0232
Continuing research introduced at the 2018 WCX conference, this paper shows the result of simulations where a midsize sedan (1700 kg) fitted with an adaptive cycle engine and a CVT is operated over three standard duty cycles: US06, FTP75, and HWFET, and compared with the results obtained from other engine cycles installed on the same vehicle. Four different engine cycles are compared: conventional 4-stroke, 6-stroke cycle with no air storage, 6-stroke cycle with air storage, and fully adaptive cycle with air storage and a number of strokes determined by instantaneous demand and state of charge of the storage tank. Results show that the fully adaptive engine achieves a better mileage in all scenarios, closely followed by the partially adaptive 6-stroke cycle with storage. Gains over a conventional 4-stroke powerplant range from 3.4 mpg on the HWFET cycle, to 7.6 mpg on the FTP75 cycle. Furthermore, air storage allows the adaptive cycle engine to be substantially downsized while still being able to supply sufficient power even on the demanding US06 cycle, resulting in mileage figures over 70 mpg on the FTP75 and HWFET cycles. The paper concludes with a discussion of control strategies that lead to high fuel economy while maintaining sufficient peak power, especially tailored to the fully and partially adaptive cycle engines.