Comparison of High- and Low-Pressure Electric Supercharging of a HDD Engine: Steady State and Dynamic Air-Path Considerations

Abstract

This paper numerically investigates the performance implications of the use of an electric supercharger in a heavy-duty DD13 diesel engine. Two electric supercharger configurations are examined. The first is a high-pressure (HP) configuration where the supercharger is placed after the turbocharger compressor, while the second is a low-pressure (LP) one, where the supercharger is placed before the turbocharger compressor. At steady state, high engine speed operation, the airflows of the HP and LP implementations can vary by as much as 20%. For transient operation under the Federal Test Procedure (FTP) heavy duty diesel (HDD) engine transient drive cycle, supercharging is required only at very low engine speeds to improve airflow and torque. Under the low speed transient conditions, both the LP and HP configurations show similar increases in torque response so that there are 44 fewer engine cycles at the smoke-limit relative to the baseline turbocharged engine. When the requested engine torque rise rate is increased from the FTP ramps to steps, the benefit of supercharging is extended to also include mid-range engine speeds, with over ∼ 70% fewer cycles at the smoke-limit line. In addition, the results show an improvement in the overall fuel economy of the supercharged engine during low engine speed transients compared to the baseline turbocharged engine. The study highlights the importance of supercharger bypass valve control, where the transient response of the valve should be twice as fast as the electric supercharger drive motor for accurate and minimal supercharger power consumption during transient maneuvers. Finally, an engine re-calibration with increased exhaust gas recirculation at low engine speeds/loads, resulted 4.6% fuel economy improvements at that low speed/load region while the supercharger enabled fast air-flow increase during aggressive tip-ins.

An Integrated Framework on Characterization, Control, and Testing of an Electrical Turbocharger Assist

“…Compared with other electrically assisted boosting systems, the ETA can achieve higher fuel efficiency than the electric supercharger [5]- [7] and electric turbocompounding [8]- [10]. The electric supercharger and the turbocharger work as a twostage system, with the EM and compressor connected in series.…”

Progress and recent trends in 48 V hybridisation and e-boosting technology on passenger vehicles – a review

“…Due to the lower material stress, sealing stress and packaging issues, however, most research institution and automobile manufacturers currently employ LP configurations. 20,21 The e-boosting device, according to its performance, can be categorised into the following two clusters: 1) transient machines; 2) transient and steady-state machines.…”

“…Due to the lower material stress, sealing stress and packaging issues, however, most research institution and automobile manufacturers currently employ LP configurations. 20,21…”

“…An engine fitted with an e-boosting system will not have to trade the part-load BSFC for the transient response, however, and this will result in some fuel efficiency improvement, which to the authors’ knowledge refers to the control strategy refinement in Figure 21. For engines with exhaust gas recirculation (EGR) systems, an increased EGR rate could also be used at part load, which according to the literature 20 has a 4.6% fuel economy improvement.…”

Performance Optimization of a Diesel Engine with a Two-Stage Turbocharging System and Dual-Loop EGR Using Multi-Objective Pareto Optimization Based on Diesel Cycle Simulation

“…They found that applying an electric turbo charging system improved transient responses and fuel efficiency. Salehi et al [18] investigated the effects of high and low pressure eSs on a heavy duty diesel engine, for both steady state and transient operations, and found that LP eS was more efficient with respect to transient responses, although the high engine speed response was improved with an HP eS.…”