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Journal Article

xD+1D Catalyst Simulation-A Numerical Study on the Impact of Pore Diffusion

This paper presents a numerical study on the impact of washcoat diffusion on the overall conversion performance of catalytic converters. A comprehensive transient 1D pore diffusion reaction model is embedded in state-of-the-art 1D and 3D catalytic converter models. The pore diffusion model is discussed with its model equations and the applied diffusive transport approaches are summarized. The diffusion reaction model is validated with the help of two available analytical solutions. The impact of basic washcoat characteristics such as pore diameters or thickness on overall conversion performance is investigated by selected 1D+1D calculations. This model is also used to highlight the impact of boundary layer transfer, pore diffusion and reaction on the overall converter conversion performance. The interaction of pore diffusion and flow non-uniformities is demonstrated by 3D+1D CFD simulations.
Technical Paper

Optimization of Hybrid Power Trains-Physical Based Modeling for Concept Design

This paper presents a comparison of a hybrid and a conventional powertrain using physical based simulation models on the system engineering level. The system engineering model comprises mechanistic sub-models of the internal combustion engine including exhaust aftertreatment devices, electric components, mechanical drivetrain, thermoregulation system and the corresponding controllers. Essential sub-models are discussed in detail and their interaction on the system level is pointed out. Special attention is paid to compile a real-time capable model by combining mean value air path and drivetrain models with a crank-angle resolved cylinder description and quasi-steady state considerations applied in electrical and cooling networks. A turbocharged gasoline direct injection engine is modeled and calibrated based on steady-state measurements. The conversion performance of a three way catalyst is compared to light-off measurements.
Technical Paper

High Power Discharge Combustion Effects on Fuel Consumption, Emissions, and Catalyst Heating

A key element to achieving vehicle emission certification for most light-duty vehicles using spark-ignition engine technology is prompt catalyst warming. Emission mitigation largely does not occur while the catalyst is below its “light-off temperature”, which takes a certain time to achieve when the engine starts from a cold condition. If the catalyst takes too long to light-off, the vehicle could fail its emission certification; it is necessary to minimize the catalyst warm up period to mitigate emissions as quickly as possible. One technique used to minimize catalyst warm up is to calibrate the engine in such a way that it delivers high temperature exhaust. At idle or low speed/low-load conditions, this can be done by retarding spark timing with a corresponding increase in fuel flow rate and / or leaning the mixture. Both approaches, however, encounter limits as combustion stability degrades and / or nitrogen oxide emissions rise excessively.
Journal Article

Evaluation of Valve Train Variability in Diesel Engines

The continuously decreasing emission limits lead to a growing importance of exhaust aftertreatment in Diesel engines. Hence, methods for achieving a rapid catalyst light-off after engine cold start and for maintaining the catalyst temperature during low load operation will become more and more necessary. The present work evaluates several valve timing strategies concerning their ability for doing so. For this purpose, simulations as well as experimental investigations were conducted. A special focus of simulation was on pointing out the relevance of exhaust temperature, mass flow and enthalpy for these thermomanagement tasks. An increase of exhaust temperature is beneficial for both catalyst heat-up and maintaining catalyst temperature. In case of the exhaust mass flow, high values are advantageous only in case of a catalyst heat-up process, while maintaining catalyst temperature is supported by a low mass flow.
Journal Article

Solutions for Emission Robustness of BS VI Phase II Respecting the Market Specific Requirements

Most stringent emission legislations have been implemented in all major markets to improve air quality across the past years. This effects the product cost of the vehicles which is considered being critical and needs to be minimized. India suffers from bad air quality and countermeasures have been defined. One being the implementation of similar emission standards than EU VI. By doing so, India takes a large step going from the currently effective BS IV directly to BS VI. Emission reduction is currently mainly handled by the usage of EGR, thus no engine aftertreatment system has been applied. BS VI will require an aftertreatment (EAS) concept with several catalysts and corresponding control system. India is a very cost sensitive market and a carry over of solutions from the EU needs to be evaluated carefully and new approaches need to be found.