Compact Post-Aftertreatment Temperature Control Device for Exhaust Gas Cooling

This paper presents a compact temperature control device to cool down hot exhaust gas coming out of an aftertreatment emission control system. Active DPF (Diesel Particulate Filter) regeneration is required for aftertreatment emission controls to meet the 2007 EPA (Environmental Protection Agency) PM(Particulate Matter) standard. However, regeneration of the DPF temporarily elevates temperatures in the filter to eliminate accumulated soot. This can increase the temperature of the exhaust gas. The temperature control device in this paper draws ambient air into the hot exhaust stream and mixes them together in such a fashion to maximize temperature drop and minimize back pressure for a limited space without any moving parts or supply of extra power. The simple and compact design of the device makes it a cost-effective candidate to retrofit to an existing aftertreatment system. CFD (Computational Fluid Dynamics) was extensively used as a development tool and the performance prediction by CFD was validated by experiment with good correlation. The concept of ‘Thermal Mixing Index’ is introduced to evaluate the effectiveness of cooling when two fluids with a large temperature differential are met in a moving stream.