Title: The mitigation of mode-switching challenges of spark-assisted compression ignition engines through powertrain electrification
Authors: Dennis Robertson; Robert Prucka
Addresses: Department of Automotive Engineering, Clemson University, 4 Research Dr, Greenville, SC 29607, USA ' Department of Automotive Engineering, Clemson University, 4 Research Dr, Greenville, SC 29607, USA
Abstract: Spark-assisted compression ignition (SACI) is a novel combustion strategy that combines the fuel efficiency benefits of high EGR dilution, high compression ratio, and lean operation. Though the efficiency benefit is significant, SACI has several control and calibration challenges. To resolve this limitation, switching combustion modes between SACI and SI-only combustion is implemented. This work demonstrates the synergistic benefit of mild hybridisation on improving torque tracking compared to a non-hybrid SACI vehicle. A tip-in performed on a one-dimensional engine model shows a significantly reduced mode-switching challenge as the electric machine can adapt torque during mode changes, offsetting transport delays and actuator constraints. Furthermore, a vehicle model demonstrates that an electric machine can reduce the number of required mode transitions over four drive cycles from 15-40%. In addition to control benefits, the SACI powertrain also demonstrated 4-5% higher fuel economy compared to an SI-only powertrain in each vehicle configuration.
Keywords: low temperature combustion; LTC; spark-assisted compression ignition; SACI; electrification; HEV; mode switching; control; calibration; torque tracking.
International Journal of Powertrains, 2021 Vol.10 No.4, pp.373 - 394
Accepted: 16 Aug 2021
Published online: 18 Feb 2022 *