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

Abstract

Exhaust gas recirculation (EGR) is widely used in most current automotive diesel engines as a simple, economical, and highly effective NOX reduction technology. The low pressure (LP) loop EGR has higher deNOX 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 NOX 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.