Browse Publications Technical Papers 2019-01-0989
2019-04-02

Modeling of Engine After Treatment System Cooling for Hybrid Vehicles 2019-01-0989

The medium and heavy duty transport industry is currently showing a growing interest in hybrid powertrains. Currently, this technology is mainly used in buses but distribution trucks, both heavy and medium duty, are expected to become growing market segments. Hybrid trucks are potentially superior to conventional internal combustion engine (ICE) propelled trucks in a wide range of environmental areas like noise, CO2 and NOx emissions. However, since the hybrid vehicle is still partially powered by an ICE, an engine after treatment system (EATS) is necessary. Traditionally, the EATS is heated by the waste heat entering the tail pipe after the turbo. This is the most fuel efficient and practical way of bringing the EATS up to and maintaining operating temperatures of about 200 - 400 ̊C, where it's most efficient. However, in hybrid vehicles the ICE can be shut off to a larger extent than in conventional vehicles, and when the engine is off the EATS cools down. Eventually the EATS will drop below the desired temperature range making the EATS ineffective when the ICE is started again. In this paper, the physics of EATS cooling is analyzed using experimental data from a HD truck equipped with extra sensors for measuring cooling scenarios during engine off. The analysis shows that it's important to capture the spatial distribution of temperatures both in axial and radial directions, which also stresses the importance of substrate heat conduction and boundary surface conditions. Based on the experience a thermal EATS simulation model suitable for system and driving scenario simulation is developed and validated. This model is well suited for future studies where the complete system; ICE, electric drive, EATS, & control, can be analyzed and optimized under different driving conditions.

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