Research on exhaust energy distribution regulation for fuel economy improvement of turbocompound diesel engine

The stringent requirements for reducing CO2 emissions from internal combustion engines promote the development of waste heat recovery (WHR) technologies. Turbocompounding is a promising WHR technology offering fuel-saving potential along with low volume and weight requirements. Meanwhile, the exhaust energy distribution regulation plays a significant role in improving the engine fuel economy. In this study, the coupling influence and mechanism of the variable geometry turbocharger (VGT) turbine and power turbine (PT) regulation on the recovery power and engine performance were studied from novel perspective of exhaust energy distribution. And the cooperative control strategies of VGT rack position and PT speed under whole operating conditions were first proposed. It is concluded that the increase in the VGT rack position and the PT speed leads to a decrease in the proportion of exhaust energy distributed to the VGT turbine, which affects the intake and exhaust conditions, resulting in changes in PT power and net engine output power. In addition, as the engine speed increases under full load, the optimal VGT rack position and PT speed increase. Compared to the base engine, the equivalent brake specific fuel consumption can be reduced by 3.8% at the engine speed of 2200 r/min with the optimized control of the exhaust energy distribution for the turbocompounding. The control strategy of exhaust energy distribution is of great significance to explore the maximum potential of energy efficiency improvement of turbocompound diesel engines.

Automated summary

The stringent requirements for reducing CO2 emissions from internal combustion engines promote the development of waste heat recovery (WHR) technologies. Turbocompounding is a promising WHR technology offering fuel-saving potential along with low volume and weight requirements. This study investigates the coupling influence and mechanism of variable geometry turbocharger (VGT) turbine and power turbine (PT) regulation on recovery power and engine performance from the perspective of exhaust energy distribution. The study proposes cooperative control strategies of VGT rack position and PT speed under all operating conditions. The results show that increasing the VGT rack position and PT speed leads to a decrease in the proportion of exhaust energy distributed to the VGT turbine, which affects intake and exhaust conditions, resulting in changes in PT power and net engine output power.