Impact of Electrically Assisted Turbocharger on the Intake Oxygen Concentration and Its Disturbance Rejection Control for a Heavy-duty Diesel Engine

Chao Wu, Kang Song, Shaohua Li and Hui Xie
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Chao Wu: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Kang Song: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Shaohua Li: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
Hui Xie: State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China

Energies, 2019, vol. 12, issue 15, 1-22

Abstract: The electrically assisted turbocharger (EAT) shows promise in simultaneously improving the boost response and reducing the fuel consumption of engines with assist. In this paper, experimental results show that 7.8% fuel economy (FE) benefit and 52.1% improvement in transient boost response can be achieved with EAT assist. EAT also drives the need for a new feedback variable for the air system control, instead of the exhaust recirculation gas (EGR) rate that is widely used in conventional turbocharged engines (nominal system). Steady-state results show that EAT assist allows wider turbine vane open and reduces pre-turbine pressure, which in turn elevates the engine volumetric efficiency hence the engine air flow rate at fixed boost pressure. Increased engine air flow rate, together with the reduced fuel amount necessary to meet the torque demand with assist, leads to the increase of the oxygen concentration in the exhaust gas (EGR gas dilution). Additionally, transient results demonstrate that the enhanced air supply from the compressor and the diluted EGR gas result in a spike in the oxygen concentration in the intake manifold ( X oim ) during tip-in, even though there is no spike in the EGR rate response profile. Consequently, there is Nitrogen Oxides (NOx) emission spike, although the response of boost pressure and EGR rate is smooth (no spike is seen). Therefore, in contrast to EGR rate, X oim is found to be a better choice for the feedback variable. Additionally, a disturbance observer-based X oim controller is developed to attenuate the disturbances from the turbine vane position variation. Simulation results on a high-fidelity GT-SUTIE model show over 43% improvement in disturbance rejection capability in terms of recovery time, relative to the conventional proportional-integral-differential (PID) controller. This X oim -based disturbance rejection control solution is beneficial in the practical application of the EAT system.

Keywords: electrically assisted turbocharger; variable geometry turbocharger-exhaust gas recirculation; oxygen concentration; active disturbance rejection control (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (3)

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