Pre-turbo-DeNOx exhaust aftertreatment: simulation and testing

Abstract

Real urban driving conditions challenge exhaust gas aftertreatment systems for diesel passenger cars. One promising approach is the transfer of the selective catalytic reduction to a pre-turbocharger position, resulting in a thermal adjustment of the boundary conditions for the system. The design and functional behaviour of two new pre-turbo concepts are discussed. Challenges arise when the dosing of a urea–water solution and thermal mass are integrated upstream of the turbocharger. The design and results of these new concepts are presented using an integrated methodology. Three-dimensional computational fluid dynamics are used as a tool to fundamentally analyse the flow fields and the preparation process of urea–water-based solution to the reducing agent ammonia. The preparation process includes spray injection, spray interaction phenomena, and mixing of the reducing agent. The prototypically built-up hardware is integrated into an Engine-in-the-Loop test setup. In stationary engine operation, the basic measurement of temperatures and nitrogen oxides allows for the validation of the simulations. Using a simulated vehicle approach, the experimental test setup is capable of being operated in real driving scenarios. An additional 48 V boosting system is integrated and operated in the air pass to analyse and overcome thermal delay. Realistic dynamic load test results and boosted WLTC measurements of a virtual passenger car are presented.