Engine Lambda Control for Simultaneous CO and NOx Emission Targets
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Solution Overview
Problem
Current engine lambda control strategies for three-way catalytic converters face challenges in quickly reaching target lambda values, particularly under narrow constraints, making it difficult to simultaneously meet CO and NOx emissions targets across various engine operating conditions.
Innovation Solution
An engine controller adjusts the air-to-fuel ratio (lambda) using dynamic lambda control strategies that include asymmetric lambda lag times, such as shorter rich lag and longer lean lag, or vice versa, to modify the reference lambda by a percent kick, allowing for a wider range of engine operating conditions to meet both CO and NOx emissions targets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional lambda control strategy with fixed lag times is used, then the control system is simple to implement, but it cannot quickly reach target lambda values under narrow constraints
Solution Approach 1:
The patent applies dynamics by making the lambda control strategy adaptive rather than fixed. The controller dynamically selects between different control modes (first lambda control strategy for CO reduction, second lambda control strategy for NOx reduction) based on real-time emissions predictions. This dynamic adaptation allows the system to quickly reach target lambda values by choosing the appropriate control mode, while maintaining manageable complexity through rule-based selection criteria.
Solution Approach 2:
The patent changes control parameters (lag times, reference lambda values) based on operating conditions. The first lambda control strategy uses a first rich lambda lag time and first lean lambda lag time, while the second strategy uses different lag times. This parameter variation allows the system to optimize performance for different emissions targets without requiring a completely different control architecture.
2Adaptability or versatility
If the engine operates at a fixed reference lambda, then the control system is simple, but it cannot simultaneously meet both CO and NOx emissions targets across various operating conditions
Solution Approach 1:
The patent segments the lambda control into two distinct strategies: the first lambda control strategy optimized for CO emissions reduction, and the second lambda control strategy optimized for NOx emissions reduction. Each strategy has its own reference lambda modifications and lag time parameters. This segmentation allows the system to meet both CO and NOx targets by selecting the appropriate strategy, while keeping each individual strategy relatively simple.
Solution Approach 2:
The patent uses feedback from emissions predictions to select between control strategies. The controller predicts whether upcoming emissions will fail to meet CO or NOx targets and accordingly selects the first or second lambda control strategy. This feedback mechanism enables the system to adapt to varying operating conditions and meet emissions targets without requiring complex real-time optimization algorithms.
3Object-generated harmful factors
If asymmetric lambda lag times are used (shorter rich lag, longer lean lag), then CO emissions are reduced, but the control strategy becomes more complex
Solution Approach 1:
The patent applies asymmetry by using different lag times for rich and lean lambda transitions in the first lambda control strategy. Specifically, it uses a shorter first rich lambda lag time and a longer first lean lambda lag time. This asymmetric approach optimizes CO emissions reduction by allowing faster response to rich conditions while maintaining control stability. The asymmetry is managed within a rule-based framework that prevents excessive complexity.
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 enables the engine to simultaneously meet CO and NOx emissions targets over a broader range of engine operating conditions, improving the conversion efficiency of the catalytic converter and maintaining oxygen storage capacity.
Implementation Method 1
a catalytic converter configured to receive exhaust gas from an engine... One type of catalytic converter is known as a three-way conversion (TWC) catalyst, which facilitates the oxidation of unburned HC and CO, and the reduction of NOx in the exhaust gas
Implementation Method 2
internal combustion engines that typically produce undesirable exhaust emissions... byproducts of the combustion process can include unburnt hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx)
Data Source
AI summary
An emissions control system for a vehicle having an exhaust system with an exhaust gas conduit and a catalytic converter configured to receive exhaust gas from an engine is provided. In one example implementation, the system includes an engine controller configured to control the engine to adjust an air to fuel ratio (lambda) thereof. The engine controller is configured to operate the engine with at least one of the following lambda control strategies (i) a first control strategy comprising operating at a first reference lambda modified by a first percent kick, and a first rich lambda lag time shorter than a first lean lambda lag time, and (ii) a second control strategy comprising operating at a second reference lambda modified by a second percent kick, and a second rich lag time longer than a second lean lambda lag time, to thereby simultaneously meet predetermined NOx and CO emissions targets.