Johann C. Wurzenberger

Multi-Scale SCR Modeling, 1D Kinetic Analysis and 3D System Simulation

Future emission limits of diesel engines require additional effort for developing adequate and advanced exhaust gas aftertreatment devices. Urea-SCR systems are a promising approach to reduce nitric oxide emissions. Computer models as a complementary tool to experimental investigations help to make design decisions and to shorten the development process. Therefore, this work presents a comprehensive SCR simulation approach. All relevant conversion reactions are studied in a 1d model. The obtained parameters are transferred to 3d simulations and combined with a detailed description of the urea injection. Validation simulations are performed for the individual SCR reactions and show good agreement with experimental data. 1d studies of different SCR assemblies and sizes are presented. Full 3d simulations of an HSO system considering injection, homogeneous gas phase and catalytic reaction show the interaction of all relevant effects and their impact on the overall deNOx performance.

Assessment of engine thermal management through advanced system engineering modeling

Abstract A physically based approach to model vehicle dynamics, transient engine performance and engine thermal management system is presented. This approach enables modeling dynamic processes in the individual components and is the dynamic interaction of all relevant domains. The modeling framework is based on a common innovative solver, where all processes are solved using tailored numerical techniques suited to account for characteristic time scales of individual domains. This approach enables achieving very short computational times of the overall model. The paper focuses on the integration of cooling and lubrication models into the framework of a vehicle dynamics simulation including transient engine performance demonstrated on a modern passenger car featuring split cooling functionality. A validated model with a mechanically driven coolant pump provides the base for analyzing the impact of introducing an electrically driven coolant pump. Analyses are performed for two drive cycles featuring significantly different velocity profiles to reveal their influences on the operational principles of the powertrain components and their interaction. The results show for both drive cycles fuel saving due to the application of the electric water pump is relatively small and amounts between 0.75% and 1.1%. However, it is important to address that application of the electric coolant pump results in higher turbine outlet temperatures and thus in faster catalyst heat-up. Detailed analyses of the interaction between vehicle dynamics, transient engine performance and engine thermal management system provide insight into the underlying mechanisms. This is made possible by the application of physically based system level model.

Tailored Cylinder Models for System Level Engine Modelling

Abstract The model of the cylinder block represents the most challenging part of the engine model when establishing appropriate balance between the level of detail of the model and its computational speed. Furthermore its coupling to the gas path model significantly influences the performance of the overall engine model. The paper addresses various couplings of the 0D gas path models and the surrogate and the crank angle resolved cylinder block models. In addition two innovative coupling approaches are presented and discussed: 1. coupling of the mean value gas path model and the crank angle resolved cylinder model and 2. time domain decoupled interaction between the filling and emptying gas path model and the crank angle resolved cylinder model. In the paper physical background of the models is presented along with their characteristics and computational performances in terms of RT factors.

Catalytic Converters in a 1d Cycle Simulation Code Considering 3d Behavior

The objective of this study to introduce the newly developed Discrete Channel Method (DCM) as a fast and efficient method for the prediction of the 3d and transient behavior of honeycomb-type catalytic converters in automotive applications. The approach is based on the assumption that the regions between the channels are treated as a reactor with a homogeneously distributed heat source due to chemical conversion. Therefore, each radial direction can be described by a center, a boundary and only a few intermediate channels between them. The discrete channels are described by transient, 1d conservation equations that characterize the behavior of channels at different radial positions. The heat entering and leaving each discrete channel is evaluated by the gradients of the temperature field in conjunction with the heat conductivity of the substrate. The approach is validated by experimental data and serves as a module in the thermodynamic and engine analysis design tool BOOST.

Der Verbrennungsmotor als Teil des gesamten Antriebstrangs

Die verbrennungsmotorischen Antriebe stehen im Augenblick vor der grosten Herausforderung ihrer mehr als hundertjahrigen Geschichte. Die Entwicklung alternativer Antriebe, insbesondere von batterieelektrischen Antrieben, wird teilweise so euphorisch eingeschatzt, dass sogar uber ein generelles Verbot von Verbrennungsmotoren ab 2030 offen diskutiert wird. Doch selbst bei einer realistischen Einschatzung der technischen, wirtschaftlichen und marktpolitischen Realitaten ergeben sich fur den Verbrennungsmotor signifikante Herausforderungen (Fraidl et al. 2017):

Mechanistic Modeling in System Engineering: Real-Time Capable Simulation of a TGDI Engine Powered Vehicle

A mechanistic overall vehicle model is presented. Besides the mechanical driveline domain it comprises a mean value based air path, a crank-angle resolved cylinder description, exhaust gas aftertreatment, cooling and lubrication models and a software ECU to run transient operating conditions. An innovative coupling of different domains and sub-domains that allows for a very good ratio between modeling depth and computational expenses is presented. The capability of the overall model to adequately capture the interaction of different domains is demonstrated by a certification cycle simulation for cold start engine conditions. Enhancements on the engine performance are investigated by electrifying the propulsion of the water pump. The study highlights that even small changes in the powertrain topology and their assessment already call for a comprehensive multi domain system engineering model capable to mechanistically describe all essential effects.

1D/3D simulation workflow@@@1D/3D-Simulations-Workflow: Optimization of exhaust gas aftertreatment devices@@@Optimierung von Komponenten der Abgasnachbehandlung

Computer modeling as a complementary tool to experimental investigations is indispensable to design catalytic converters or diesel particulate filters. Therefore the present integrated 1D/3D workflow decisively accelerates the often very time consuming simulation process by combining the advantages of fast 1D and highly resolved 3D simulations. Characteristic parameters of design studies performed in Boost 1D aftertreatment are directly transferred to the 3D CFD code Fire and used for fine tuning.

Design and Optimization of Catalytic Converters Taking Into Account 3D and Transient Phenomena as an Integral Part in Engine Cycle Simulations

The Discrete Channel Method (DCM) is presented as a new approach to model the transient multidimensional behavior of honeycomb-type catalytic converters. DCM combines a detailed modeling of effects taking place inside individual channels with the description of thermal effects occurring in the entire converter. The model is compared to experimental data measured under adiabatic conditions and to solutions generated by the finite difference method. DCM is applied to simulate the light-off behavior for different exhaust gas compositions under adiabatic and non-adiabatic conditions. The results show the influence of changing gas compositions and of radial heat losses on the performance of catalytic converters and aftertreatment systems. Hence, DCM is an effective and computationally fast method tailored for the integration in the engine analysis tool BOOST but also for stand-alone catalyst simulation.Copyright