Lean-Rich Engine Heating Strategy for Emission Control
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Solution Overview
Problem
Internal combustion engines with externally supplied ignition face challenges in reducing pollutant emissions, particularly hydrocarbons and nitrogen oxides, during the start/catalytic converter heating phase due to inefficient heating strategies that often increase nitrogen oxide levels as exhaust gas temperature rises.
Innovation Solution
The method involves operating the engine with a lean air-fuel mixture during the initial phase and switching to a rich mixture once the catalytic converter is heated, adjusting the lambda value between 1.05 and 1.25 to minimize emissions, and using a model that considers engine behavior, fuel quality, and aging to optimize the heating strategy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the internal combustion engine is operated at reduced efficiency to heat the catalytic converter, then the catalytic converter heating speed is improved, but the nitrogen oxide emission increases
Solution Approach 1:
The patent divides the catalytic converter heating process into two distinct phases: a first phase operating with a lean air-fuel mixture (lambda 1.05-1.25) to minimize nitrogen oxide emissions, and a second phase operating with a rich air-fuel mixture (lambda 0.95-0.995) to rapidly heat the catalytic converter. This segmentation allows the system to optimize for emission reduction during the initial phase, then switch to rapid heating when the catalytic converter temperature and lambda value reach appropriate thresholds.
Solution Approach 2:
The patent applies preliminary action by first operating the engine with a lean mixture to establish low nitrogen oxide emissions before the catalytic converter reaches operating temperature, and only after the catalytic converter is sufficiently heated does it switch to the rich mixture mode for rapid temperature increase. This preliminary lean operation prevents high nitrogen oxide emissions from occurring during the heating phase.
2Temperature
If the engine operates with a rich air-fuel mixture to heat the catalytic converter, then the heating speed is improved, but the hydrocarbon emission increases
Solution Approach 1:
The patent segments the heating process into two phases: the first phase uses a lean mixture to minimize hydrocarbon and nitrogen oxide emissions while the catalytic converter heats up, and the second phase uses a rich mixture only after the catalytic converter reaches sufficient temperature to effectively process the hydrocarbons. This segmentation ensures that rich mixture operation occurs only when the catalytic converter can handle the increased hydrocarbon load.
Solution Approach 2:
The patent applies preliminary action by first heating the catalytic converter using a lean mixture during the first phase, establishing a foundation of low emissions. Only after this preliminary heating phase does the system transition to rich mixture operation, ensuring the catalytic converter is already warm enough to process the hydrocarbons generated by the rich mixture.
3Object-generated harmful factors
If the engine operates with a lean air-fuel mixture, then the nitrogen oxide emission is reduced, but the catalytic converter heating speed decreases
Solution Approach 1:
The patent segments the heating process into two distinct phases with different operational characteristics: the first phase uses a lean mixture prioritizing emission reduction, while the second phase uses a rich mixture prioritizing heating speed. This segmentation allows the system to accept slower initial heating in exchange for low emissions, then accelerate heating once emissions are managed.
Solution Approach 2:
The patent applies preliminary action by first operating in a lean mode to establish low nitrogen oxide emissions before transitioning to rich mode for rapid heating. This preliminary lean operation creates a temporal sequence where emission control takes precedence initially, followed by speed optimization once emissions are managed.
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 significantly reduces hydrocarbon and nitrogen oxide emissions by rapidly heating the catalytic converter, ensuring reliable ignition and combustion while adhering to stringent emission limits, thereby achieving a minimal total emission.
Implementation Method 1
Hydrocarbons in the exhaust gas are then combusted with the oxygen of the secondary air upstream from or inside the catalytic converter and heat it up
Implementation Method 2
The lambda probes ascertain the oxygen content of the exhaust gas, which is used for regulating the air-fuel mixture supplied to the internal combustion engine
Data Source
AI summary
A method for reducing the pollutant emissions in the exhaust gas in a start/catalytic converter heating phase of an internal combustion engine featuring externally supplied ignition and having at least one catalytic converter in an exhaust gas tract of the internal combustion engine, and for adapting a catalytic converter heating strategy to suitable state variables of the internal combustion engine and the catalytic converter as well as to the fuel quantity, the aging state and ambient conditions. The internal combustion engine is operated in a first phase of the start/catalytic converter heating phase using a lean air-fuel mixture in a range between a lambda value of 1.05 and at a lean misfire limit of the internal combustion engine that lies at a higher lambda value, and/or in a second phase of the start/catalytic converter heating phase, initially using a rich air-fuel mixture.