Effects of Different Turbocharging Systems on Performance in a HD Diesel Engine with Different Emission Control Technical Routes 2016-01-2185

In this work, both the ‘SCR-only’ and ‘EGR+SCR’ technical routes are compared and evaluated after the optimizations of both injection strategy and turbocharging system over the World Harmonized Stationary Cycle (WHSC) in a heavy duty diesel engine. The exhaust emissions and fuel economy performance of different turbocharging systems, including wastegate turbocharger (WGT), variable geometry turbocharger (VGT), two-stage fixed geometry turbocharger (WGT+FGT) and two-stage variable geometry turbocharger (VGT+FGT), are investigated over a wide EGR range. The NOx reduction methods and EGR introduction strategies for different turbocharger systems are proposed to improve the fuel economy. The requirement on turbocharging system and their potential to meet future stringent NOx and soot emission regulations are also discussed in this paper. The experimental results show that retarding CA50 shows more advantages in improving soot emission and fuel economy than further closing the intake throttle valve, because the excess air ratio is critical to the combustion efficiency and soot oxidation when the NOx is kept at low level. As to ‘SCR-only’ technical route, reducing the injection pressure appropriately and advancing CA50 as early as possible are beneficial to fuel economy. The requirement on turbocharging system is varying at different NOx emission levels. The WGT, WGT+FGT, VGT and VGT+FGT are recommended to be adopted in ‘SCR+EGR’ technical route when the weighted NOx are controlled at 8.0 g/kWh, 5.0 g/kWh, 3.5 g/kWh and 2.8 g/kWh, respectively. Furthermore, according to the weighted results, the ‘SCR+EGR’ technical route shows more potential to meet the future more stringent NOx emission regulations compared to the ‘SCR-only’ technical route because of the superior fuel economy.