Transient Modelling of Vehicle Exhaust Surface Temperature 2016-01-0280

In this paper, the development of a transient thermal analysis model for the exhaust system is presented. Given the exhaust gas temperature out of the engine, a software tool has been developed to predict changes in exhaust gas temperature and exhaust surface temperature under various operating conditions. The software is a thermal solver that will predict exhaust gas and wall surface temperatures by modeling all heat transfer paths in the exhaust system which includes multi-dimensional conduction, internal forced/natural convection, external forced/natural convection, and radiation. The analysis approach involves the breaking down of the thermal system into multiple components, which include the exhaust system (manifold, takedown pipe, tailpipe, etc.), catalytic converter, DPF (diesel particulate filter), if they exist, thermal shields, etc. All components are modeled as 1D porous and 1D non-porous flow streams with 3D wall layers (solid and air gaps). The aggregate of all these components is referred to as the thermal network. All relevant modes of heat transfer between the parts, i.e., forced convection, conduction and radiation are considered. Analysis of the thermal network is conducted by coupling all the components in the form of a computational grid, which for the most part will be conducted via implicit numerical procedure. This will make the solution robust, particularly for conduction dominant conditions. Results from the transient analysis are compared to actual vehicle tests under various test conditions