Fuel efficiency and exhaust characteristics of turbocharged diesel engine equipped with an electric supercharger

Highlights: • The IMEP increased using an electric supercharger under low-speed engine conditions. • It is possible to increase the efficiency and IMEP with proper control of the engine. • The fuel efficiency is improved by up to 8.8% under low-speed engine conditions. • BSCO and BSTHC decreased with the operation of the electric supercharger. • BSPM and BSNOx are partially reduced compared to the base condition. The electric supercharger, which is an important device of the 48 V hybrid system, is known to increase the low-speed efficiency and torque of the internal combustion engine. However, there is a lack of research on exhaust emissions, which are becoming more stringent owing to the use of the electric supercharger. Therefore, this study conducted basic experiments and analysis on the power, fuel efficiency, and exhaust emissions according to the change of engine control parameters during operation of the electric supercharger. The maximum indicated mean effective pressure (IMEP) increase was 52.9% at 1250 rpm. However, friction mean effective pressure (FMEP) and pumping mean effective pressure (PMEP), associated with a loss of engine efficiency, increased under various operating conditions. Brake specific fuel consumption (BSFC) improved by up to 8.8%, and brake specific carbon dioxide (BSCO₂) decreased accordingly. Brake specific particulate matter (BSPM) and brake specific oxides of nitrogen (BSNOx) fluctuated significantly with the adjustment of the parameters for engine control. These were partially reduced compared to the conventional engines according to the experimental conditions. Therefore, even if an electric supercharger is applied to a diesel vehicle equipped with exhaust reduction devices, emission regulations can be satisfied.