Development of a Passive Exhaust Gas Cooler for Diesel Vehicles Using CFD

This paper reports on the development of a passive exhaust cooler for General Motors diesel vehicles to lower engine exhaust gas temperatures at the tail pipe exit. Such a cooler is needed to lower tail pipe gas temperatures that can exceed 600°C during regeneration of the particulate filter. The use of a particulate filter is driven by emissions regulations for diesel trucks since the 2007 model year in the U.S. The cooler should also find application in vehicles outside the U.S. as emissions requirements necessitate the use of particulate filters globally.

Key features of this device include: no moving parts, high reliability, low skin temperature, low pass by noise, low manufacturing cost and ease of packaging. While lowering tail pipe gas temperatures to acceptable levels, the benefits of this cooler also extend to reduced fuel consumption and improved engine oil life by avoiding starting and stopping regenerations during city driving. There are no federal safety requirements regarding skin temperatures or exhaust gas temperatures for these exhaust systems but reference materials such as the Australian government Code of Practice for Underbody Exhaust System Surface Temperatures were used. [1].

CFD analysis and vehicle test data for different designs helped to identify and understand the key parameters controlling the performance and penalties of the cooler. Variants of the cooler were optimized to meet the desired decrease in the tail pipe exit gas temperatures for different vehicles.