Search Results

This paper describes the characterisation of heat transfer in a series of 11 test sections designed to represent a range of configurations seen in production exhaust systems, which is part of a larger activity aimed at the accurate modeling of heat transfer and subsequent catalyst light off in production exhaust systems comprised of similar geometries. These sections include variations in wall thickness, diameter, bend angle and radius. For each section a range of transient and steady state tests were performed on a dynamic test cell using a port injected gasoline engine. In each case a correlation between observed Reynolds number (Re) and Nusselt number (Nu) was developed. A model of the system was implemented in Matlab/Simulink in which each pipe element was split into 25 sub-elements by dividing the pipe into five both axially and radially. The modeling approach was validated using the experimental data.

The measurement of vehicle modal emissions is technically challenging due to the major issue of determining exhaust gas mass flow rate and ensuring that it is synchronous with the emission measurement of that corresponding ‘slug’ of exhaust gas. This is very evident when attempting to measure small passive NOx catalyst conversion efficiencies. This paper highlights alignment issues with regard to the variation of time delays associated with engine and vehicle events and the CO2 tracer method for determining exhaust gas flows.