March 6 - 8, 2017 | Berlin
LEADING ENGINEERING SIMULATION CONFERENCE
Cooled exhaust gas recirculation (EGR) is effective for the reduction of NOx raw emissions of internal combustion engines. The required cooler has to be designed to efficiently reduce the exhaust gas temperature by several hundred K. The hot exhaust gas on the one side and the coolant on the other side cause strong temperature gradients in the cooler. This effect leads to locally different thermal expansion. In combination with pressure differences between gas and coolant, high stresses are induced into the cooler material. Therefore, beside the efficiency the long term durability is a challenging task for the design of EGR coolers.
For the evaluation of long term conditions Atlanting has developed an unique approach to analyze fouling processes in EGR coolers with STAR-CCM+® conjugate heat transfer CFD simulations (presented together with Benteler AG on last global conference 2016). The presence of cooled walls in the EGR cooler causes deposits of particulates and condensation of hydrocarbons, water and sulfuric acid on the gas side. These deposits lead to reduced cooling performance and increased pressure drop. Therefore, they have an important impact on the thermal durability.
The consideration of deposit formation under real driving conditions enables to analyze, which operating conditions are critical in view of cooler efficiency and which are critical in view of durability. Both developing targets may have a trade-off regarding design optimization steps. Therefore, the analysis of thermodynamical and mechanical properties always have to go hand in hand to design an EGR cooler, which is efficient and reliable under long term conditions.
Typically in the analysis process the CFD temperature fields of the solids are exported and used in FE software from third parties to perform stress analysis. With the extending possibilities of stress analysis within STAR-CCM+ it becomes obvious to use it for CHT and fatigue analysis to increase the efficiency of the design process.
The topic of this presentation is the analysis of the potential to use STAR-CCM+ for the complete evaluation of AGR coolers. It is inspected, which advantages can be generated regarding work flow and quality control, if flow simulation and stress analysis are solved within one single software without data transfer and the risk of interpolation inaccuracies. The increase of efficiency due to higher automation capabilities and the possible speed up in model setup is evaluated as well as the quality of the results in terms of durability analysis.