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

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.

Calculation of Intake Oxygen Concentration through Intake CO2 Measurement and Evaluation of Its Effect on Nitrogen Oxide Prediction Accuracy in a Heavy-Duty Diesel Engine

“…This model is based on the evaluation of the deviations of NOx emissions with respect to the nominal engine-calibration map values as a function of the deviations of the intake oxygen concentration and MFB50. This approach assumes that NOx formation is closely correlated with combustion phasing, which affects the temperatures of the burned gases, and with intake O 2 concentration [11,30].…”

Numerical Simulation of Two-Stage Variable Geometry Turbine

“…Some of them include the mixed-flow turbine of a turbocharger under unsteady flow conditions [10]. Moreover, the electrically assisted variable turbochargers are taken into account for experimental tests [11].…”

Experimental Fitting of Redesign Electrified Turbocompressor of a Novel Mild Hybrid Power Train for a City Car

“…Furthermore, its flexibility guarantees the increase in the boost pressure and the improvement of the transient behavior, without increasing the back pressure of the exhaust gases and without impact on the charge replacement in the cylinder. It is no coincidence that the studies conducted [5] have highlighted the ability of the system to be "bidirectional" (from an energy point of view), but limiting the studies conducted to a heavy-duty diesel engine and never exceeding the speed of 2000 rpm of the ICE engine. Other authors have investigated the possibility of equipping an ICE diesel with a regenerative turbocharger [6] by simulating its behavior on the FTP-75 drive cycle and evaluating the performance of the system.…”