Numerical investigation on a dual loop EGR optimization of a light duty diesel engine based on water condensation analysis

Exhaust gas recirculation (EGR) is widely used in most current automotive diesel engines as a simple, economical, and highly effective NO_X reduction technology. The low pressure (LP) loop EGR has higher deNO_X efficiency, but also has problem of water condensation, which causes wear of the turbocharger compressor wheel, and corrosion or freeze rupture of intake components. Using a one-dimensional engine simulation, we built a real-time water condensation model based on heat transfer analysis around the intercooler, and optimized the dual loop EGR control strategy to minimize water condensation while maintaining NO_X reduction performance. As a result, water condensation decreased by up to 20.54% at 100 km/h constant-speed driving, depending on ambient temperature and humidity. At 23 °C temperature / 80% humidity, which is the standard condition of worldwide harmonized light-duty test procedure (WLTP), the amount of condensed water decreased by up to 33.39%, for various engine speeds and loads. During worldwide harmonized light-duty test cycle (WLTC) driving, condensed water decreased by up to 30.56%, while fuel consumption increased by maximum of 1.13%. Since the water condensation prediction model presented in this study was constructed through the general energy analysis, it could be applied to various types of engines and operating conditions.