A Study of Dynamic Combustion Control for High Efficiency Diesel Engine 2020-01-0297
In recent years the emission produced in the transportation sector is getting more and more into the focus, leading to significantly strengthened emission regulation with regard to NOx and CO2, especially in Real Driving Emission (RDE). Therefore, diesel combustion improvement is key challenge. In the past research, Combustion Rate Shaping concept (CRS) was investigated to improve engine thermal efficiency with using more precise heat release profile control.
In this study, combustion control concept called “Closed-Loop Combustion Control (CLCC)” was investigated in order to achieve NOx and CO2 reduction with limited calibration effort.
Combustion profile parameters, start of ramp (SOR) and gradient of In-cylinder pressure increment (Alpha), were applied and controlled to represent target in-cylinder pressure trace directly. Then, SOR and Alpha parameters introduce ideal heat release of combustion by inversed combustion model and feedback by actual cylinder pressure trace. Finally, heat release of combustion was distributed to increased number of injection patterns by injection model in consideration with ignition delay. To achieve precise injection flexibility with short injection interval, next generation fuel delivery system with the G4.5S solenoid injector is also applied. The injector enables close-couple injection with faster needle opening and steep injection rate shape. CLCC approach with precise, multiple injection flexibility makes combustion heat release more gradual, and decrease in-cylinder temperature, so that advanced combustion timing close to TDC is achieved without emission deterioration and/or combustion noise increment. As a result, CLCC approach achieves high efficiency combustion with significantly reduced calibration effort to trace target in-cylinder pressure.
Multi-cylinder Engine experiment confirmed lower in-cylinder temperature in the condition of forwarded combustion timing, and proved remarkable improvement of NOx-CO2 trade-off in transient driving cycle; Worldwide Harmonized Light vehicles Test Cycle (WLTC).
Tokuji Kuronita, Takuya Sakai, Dirk Queck, Ron Puts, Sebastian Visser, Olaf Herrmann, Yoshiaki Nishijima
Aichi Institute of Technology, DENSO CORPORATION