Electric Supercharger Control for Lean Combustion NOx Management
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Solution Overview
Problem
Internal combustion engines operating in lean combustion mode face challenges in maintaining the target air fuel ratio when the battery is insufficiently charged, leading to increased NOx emissions due to reduced air supply, and existing technologies struggle to prevent intermediate air fuel ratios that are not preferable for NOx emission control.
Innovation Solution
A control method and device that predefine stoichiometric and lean combustion operation regions based on engine torque and speed, determine the required electric energy for the electric intake air supply device, and shift from lean to stoichiometric combustion mode when the battery state of charge is insufficient, ensuring the air fuel ratio is maintained at or close to the stoichiometric ratio to enable effective three-way catalyst operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lean combustion mode is employed to reduce fuel consumption, then fuel efficiency is improved, but air fuel ratio control becomes difficult when battery charge is insufficient, leading to increased NOx emissions
Solution Approach 1:
The system dynamically switches between lean combustion mode and stoichiometric combustion mode based on real-time battery state of charge assessment. When battery charge is sufficient, lean combustion is used for fuel efficiency; when battery charge becomes insufficient, the system transitions to stoichiometric combustion to prevent NOx emission increases, thus adapting combustion strategy to changing energy conditions
Solution Approach 2:
The control device continuously monitors battery state of charge and uses this feedback information to adjust combustion mode selection. The system assesses whether battery charge is sufficient to support lean combustion operations and switches modes accordingly, creating a closed-loop control system that prevents NOx emission problems while maintaining fuel efficiency
2Quantity of substance
If electric intake air supply device is used to achieve high air fuel ratio in lean combustion mode, then air supply capability is improved, but system reliability decreases when battery charge is insufficient, causing actual air fuel ratio to deviate from target
Solution Approach 1:
The system dynamically adjusts the operating strategy based on battery charge levels. When battery charge is sufficient, the electric intake air supply device operates to enable lean combustion with high air fuel ratios. When battery charge becomes insufficient, the system transitions to stoichiometric combustion mode, effectively disabling the electric supercharger operation, thus adapting air supply capability to matching energy availability
Solution Approach 2:
The control device continuously monitors battery state of charge and uses this feedback to determine whether to operate the electric intake air supply device. This feedback mechanism ensures that air supply operations only occur when energy conditions permit, preventing reliability issues and maintaining accurate air fuel ratio control
3Adaptability or versatility
If intermediate air fuel ratio between lean and stoichiometric is employed, then combustion flexibility is improved, but NOx emission control deteriorates due to insufficient three-way catalyst effectiveness
Solution Approach 1:
The system applies different combustion strategies to different operating conditions defined by battery charge state. In regions where battery charge is sufficient, lean combustion with high air fuel ratios is applied for fuel efficiency. In regions where battery charge is insufficient, stoichiometric combustion is applied to ensure NOx emission control. This creates distinct operational zones with optimized local characteristics
Solution Approach 2:
The control device preliminarily assesses battery state of charge before selecting combustion mode. By evaluating energy availability in advance, the system pre-determines the appropriate combustion strategy, preventing entry into intermediate air fuel ratio regions that would compromise NOx emission control while maintaining combustion flexibility
Data Source
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AI summary
In the present invention, an internal combustion engine (1) is provided with an electric supercharger (2) driven by an in-vehicle battery and can switch between a stoichiometric combustion mode, in which the vicinity of a theoretical air-fuel ratio is used as a target air-fuel ratio, and a lean combustion mode, in which a lean air-fuel ratio is used as the target air-fuel ratio. In a part (L2) of a lean combustion operation range (L) which is to be in the lean combustion mode, the electric supercharger (2) bears a part of the air intake volume. When operation is continuing in this second lean combustion operation range (L2) and the state of charge (SOC) is equal to or less than a lower-limit value (SOClim), the electric supercharger (2) is stopped and a forced switch is made to the stoichiometric combustion mode. Because of this, the air-fuel ratio changes in a stepwise manner, so worsening of NOx due to operation at an intermediate air-fuel ratio is avoided.