exothermia suite Advanced Features
Advanced features from exothermia suite
Advanced features from exothermia suite
A comprehensive library of generic reaction schemes is available for all catalyst technologies of interest. In addition, the user is able to type own reactions and reaction rate expressions via an intuitive graphical interface.
The kinetic rate parameters included in the rate expressions can be calibrated for any given washcoat/catalyst formulation using simple tests under well-controlled lab conditions.
The operation of many modern catalytic systems is strongly affected by the periodic storage/release of various exhaust species on the surface.
Submodels for transient reaction phenomena, include:
Temperature dependent storage mechanism
Flexibility and accuracy in calibration can be highly improved, by using the temperature dependent storage mechanism. The total storage capacity of each storage site can be defined also as a function of temperature.
Gas phase (homogeneous) reactions
Homogeneous gaseous reactions, eg HC oxidation, Isocyanic acid (HCNO) and hydrolysis towards NH3.
Liquid evaporation and phase transitions
Modeling the transition between the liquid and the gas phase of injected droplet liquid species (water, hydrocarbons, fuel) enables modeling of fuel injectors in the exhaust pipe.
In addition, phase transitions of urea-water solutions, including H2O evaporation, solid urea thermolysis to ammonia and isocyanic acid is also very important for SCR system modeling.
Phase transition models are also available for predicting the formation of liquid wall films on the pipe and/or static mixer as well as liquid to solid deposit formation.
Although single-channel catalyst modeling is frequently used as a time-efficient approach, many of the commercial catalyst applications have to be treated by more dimensions. This is due to unavoidable flow and temperature profiles developed at the entrance of catalyst substrates. This is especially evident in many modern applications where packaging constraints do not allow an optimum inlet/outlet cone geometry.
Apart from CPU-intensive CFD coupling, exothermia suite offers time-efficient solutions for predicting the inlet flow profile as function of operating conditions.
exothermia suite offers unique ‘intralayer’ modeling solutions solving the complex reaction-diffusion equations within the washcoat and substrate wall. This is particularly important for the case of high washcoat amounts, multi-layer coatings and extruded catalyst technologies.
Thanks to highly efficient solvers, both uniform as well as non uniform washcoat shapes can be modeled within the ‘faster-than-real-time’ conditions.
For the case of the 3-way catalyst in gasoline engines, it is important to obtain a correct prediction of the light-off after cold start. This is possible by accurate heat transfer prediction and successful calibration of the reaction kinetics.
In addition, it is important to consider the effects during highly transient exhaust gas composition changes during hot operation. In this case, it is important to account for the effects of the oxygen storage components (OSC) present in the washcoat formulation, such as Ce oxides are responsible for the periodic storage of oxygen during lean mode and its release during rich mode.
The Diesel Oxidation Catalyst (DOC) is a well-established technology for CO and HC reduction. For DPF equipped vehicles the DOC has an additional role to oxidize efficiently the hydrocarbons in the exhaust gas during the post-injection assisted regeneration mode and thus increase the exhaust temperature to the desired level for soot oxidation.
In addition, the DOC, which is usually closely coupled to the exhaust turbine, converts NO to NO2, the latter being important for the operation of downstream after-treatment components. In the case of a downstream DPF, NO2 is a very active soot oxidizer at low temperatures. In the case of a downstream SCR system, its performance is strongly affected by the NO/NO2 ratio and is typically optimized at a ratio close to 1. Finally, in the case of a downstream lean NOx trap system, the storage mechanisms of NO2 are significantly different to those of NO. The above examples highlight the importance of DOC modeling especially in a context of complete exhaust line simulation where the synergies between different aftertreatment components is critical.
SCR systems performance is strongly related to sensitive design and operating parameters, such as catalyst type and amount, temperature control, NO/NO2 ratio and NH3 storage dynamics. Many of the above parameters are linked to engine and Urea dosing management, therefore a closed-loop simulation becomes necessary.
exothermia suite offers an integrated platform for integrating the most sophisticated reactor models with suitable real-time capable injector and static mixer models as well as dosing controller models enabling advanced optimization studies.
LNT is probably the most challenging and complex reaction model involving – beyond standard “3-way” reactions – all mechanisms involved in the storage of NO and NO2 during lean mode and their release and reduction during the short duration of rich mode.
Advanced exothermia suite models have been applied to predict the effect of Sulfur on NOx conversion enabling the prediction of gradual catalyst reversible deterioration over lifetime. De-sulfation models have been further used to optimize the deSOx engine management with minimum fuel consumption.
The prediction of the NOx breakthrough during the rich-mode operation is even more challenging and affected by many competitive physico-chemical mechanisms.
Many of the actual DPF regeneration problems are 3-dimensional in nature, due to non-cylindrical geometries, asymmetric flow conditions at the entrance and filter segmentation.
exothermia suite is specially designed to allow 3-d simulations extremely fast and with minimum user effort. Using exothermia suite modeler and automatic meshing capabilities, a 3-dimensional simulation of a complex transient regeneration case can be accomplished by non-CFD experts in a couple of hours.
Due to the additional model dimension through the wall, exothermia suite simulations are referred to as 3d+.
There are numerous applications where 3d+ simulations are valuable, such as:
exothermia suite uses a built-in 3d mesh generator with easy definition of any geometry, including racetrack and user-defined periphery contours. For the case of segmented filters, the user only has to specify the segment size and positioning.
The 3D mesh discretization automatically refines the mesh close to the periphery and the cement layers for proper modeling of semi-permeable channels. It further supports user-defined refinement in areas of interest, eg for accurate stress analysis calculations.
The filtration efficiency of wall-flow filters and the resulting soot distribution in the wall is a major modeling challenge especially when both mass- and number-based filtration calculations are important.
Using theory models of the governing diffusion and interception phenomena, the filtration efficiency is calculated as function of the exhaust gas and wall micro-structure properties. Additional semi-empirical methods are available to calculate the filtration efficiency of the soot-laden wall and the transition to “cake filtration” mode.
Advanced pressure drop models are available to account for all flow resistances met in wall-flow filters, namely:
Thanks to intra-wall discretization and filtration modeling, the code is able to calculate the soot distribution within the wall at every location of the filter.
This enables the prediction of the so-called “pressure-drop hysteresis” effect, which is frequently met after partial DPF regenerations. This effect should be carefully considered to correlate pressure drop with DPF soot loading, which is critical for DPF regeneration management.
Modeling of soot oxidation mechanisms based on O2 and NO2 is important for the calculation of the filter regeneration rate, the resulting pressure drop evolution and the temperature/stress field.
The calculation is based on well-established reaction schemes and respective kinetic parameters that have been extensively validated in real-world cases.
The reaction scheme is able to handle all types of commercial wall-flow filters, including:
Apart from the pre-defined kinetic data, the user is able to modify the reaction rates. Customized reaction schemes for soot oxidation can be implemented upon request.
exothermia enables stress analysis calculation through the axistress module and plots the results using the 3D graphs feature.
The 3-dimensional temperature fields produced by exothermia can be also used as input to other common FEM solvers for stress analysis.
Stress analysis is commonly used to evaluate the material stability of the DPF under critical operating modes.
Furthermore, the effect of peripheral components can also be evaluated, including:
For engineers working at system level simulation, e.g. complete vehicle with controls, it is crucial to remove any barriers when it comes to integration of models already developed by different software tools. exothermia offers hosting and connectivity of 3rd party models developed using the FMI standards as well as Matlab/Simulink(R) blocks.
Control engineers will plug the configured exothermia suite models and play in their preferred process modeling environment for SiL and HiL applications: Matlab/Simulink(R), ETAS/Intecrio, dSpace/Scalexio, and others.
Further to Matlab/Simulink(R), exothermia suite models are FMI 1.0 and 2.0 compatible, offering connectivity with practically all industrial level simulation tools.
In addition to the built-in 3d modeling features, it is possible to couple exothermia suite component models with 3rd party commercial CFD tools.
This is particularly handy for CFD engineers who continue working in their preferred tool and simply plug the appropriate exothermia suite model combining the power of 3d flow solvers with advanced EAT reaction models.