Different Exhaust Temperature Management Technologies for Heavy-Duty Diesel Engines with Regard to Thermal Efficiency

Abstract Driven by increasingly strict environmental protection regulations, advanced clean combustion and after-treatment technologies have been applied to diesel engines so as to achieve zero impact emissions. After-treatment systems can realize highly efficient conversion within a certain temperature range. Thermal management technology is important in rapidly improving the temperature in after-treatment systems. However, the traditional thermal management technology is characterized by the trade-off between thermal efficiency and exhaust gas temperature. On the basis of numerical simulations and experimental tests method on a heavy-duty diesel engine, this study investigated the potential of improving exhaust gas temperature from the aspects of fuel system and air system. Focus was directed toward the influence of intake throttle, exhaust throttle, intercooler cooling control, and variable geometry turbocharger (VGT)-coupled retarded intake valve closing timing technology (RIVCT) on exhaust gas temperature and thermal efficiency. Results showed that the VGT–RIVCT can improve thermal efficiency and exhaust gas temperature and effectively solve the trade-off problem of the traditional thermal management technology. In this study, we adopted thermal insulation, post-injection, and VGT–RIVCT, to achieve the temperature of selective catalytic reduction (SCR) system in the cold WHTC cycle reaching 190 °C in the 450th second, and significantly reduce NOx emissions.