One-Dimensional Catalyst Model for Cold Start Emissions
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Solution Overview
Problem
Existing methods for controlling exhaust gas emissions in gasoline engines, particularly during cold starts, face challenges due to the complexity of partial differential equation models and the inaccuracies of zero-dimensional models, which require significant processing power and neglect essential parameters, leading to inefficient emissions control.
Innovation Solution
A simplified one-dimensional model is developed that groups exhaust gas species into oxidant and reductant groups, using effective mass transfer concepts to account for diffusion within the catalyst washcoat, allowing for reduced computational requirements and accurate prediction of emissions, while maintaining the catalyst's fractional oxidation state at a desired level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a physics-based model with partial differential equations in one or more dimensions is used to determine stored oxygen level, then measurement precision is improved, but device complexity increases and processing power requirements exceed available engine controller capacity
Solution Approach 1:
The patent segments the complex partial differential equation model into a zero-dimensional axially averaged model that retains the essential physics while reducing spatial dimensions. This segmentation allows the model to be implemented in engine controllers by eliminating the need to solve complex PDEs while preserving the core functionality of tracking stored oxygen levels through grouped exhaust species concentrations.
Solution Approach 2:
The patent extracts the essential physical principles from the complex PDE model by grouping exhaust gas species into oxidant and reductant categories. This extraction creates a simplified zero-dimensional model that captures the dominant oxygen storage dynamics without requiring the full computational apparatus of multi-dimensional PDE solutions, making it suitable for real-time engine control applications.
2Device complexity
If a zero dimensional axially averaged model is used to determine stored oxygen level, then device complexity is reduced, but measurement precision deteriorates due to neglected parameters and inaccurate cold start predictions
Solution Approach 1:
The patent applies parameter changes by introducing temperature-dependent parameters and transient terms into the zero-dimensional model. These modifications allow the simplified model to accurately capture cold start dynamics and transient behavior while maintaining computational simplicity. The model adjusts key parameters based on operating conditions to preserve accuracy across different engine states.
Solution Approach 2:
The patent incorporates preliminary action by pre-calculating and storing lookup tables for temperature-dependent parameters and mass transfer coefficients. This allows the zero-dimensional model to quickly access accurate parameter values during cold start and transient conditions without requiring complex real-time calculations, thereby maintaining both simplicity and precision.
3Measurement precision
If exhaust gas species are not grouped into oxidant and reductant groups, then measurement precision is improved by tracking individual species, but processing resources increase significantly
Solution Approach 1:
The patent merges individual exhaust gas species into two functional groups: oxidants (species that donate oxygen, such as O2 and NOx) and reductants (species that consume oxygen, such as CO, HC, and H2). This grouping reduces the number of differential equations that must be solved while preserving the essential oxygen storage and release dynamics, thereby improving computational efficiency without significantly compromising the accuracy of stored oxygen level determination.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces processing resources, improves emissions control, and provides accurate real-time predictions during cold starts, offering a non-intrusive monitoring system less dependent on sensor location, effectively maintaining optimal engine air-fuel ratios and indicating catalyst degradation.
Implementation Method 1
Ceria is commonly added to a catalyst to act as a buffer for oxygen storage
Implementation Method 2
the fractional oxidation state of a catalyst, the fractional oxidation state based on reaction rates of exhaust gas species
Implementation Method 3
reaction rates of exhaust gas species in a one-dimensional model averaged over space and time mass balance and energy balance equations
Implementation Method 4
The gradients in the transverse direction are accounted for in the internal and external mass transfer coefficients
Implementation Method 5
effective mass transfer concept. In this way, a simplified one-dimensional model may be used to predict both a total oxygen storage capacity and fractional oxidation state
Data Source
AI summary
A method comprising adjusting a fuel injection amount based on a fractional oxidation state of a catalyst, the fractional oxidation state based on reaction rates of grouped oxidant and reductant exhaust gas species throughout a catalyst and a low-dimensional physics-based model derived from a detailed two-dimensional model to obtain a one-dimensional model averaged over time and space that accounts for diffusion limitations in the washcoat and accurately predicts emissions during cold start.