Exhaust Gas Purifier Fuel Addition Control
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Solution Overview
Problem
In internal combustion engine exhaust gas purifiers, the addition of fuel to increase temperature for particulate matter regeneration often results in high-concentration unburned hydrocarbons (HC) being discharged, leading to white smoke due to inadequate fuel atomization and burning, especially when the oxygen concentration is low and the glow plug cannot directly heat the added fuel.
Innovation Solution
An exhaust gas purifier system that includes an unburned fuel concentration detecting unit and an added fuel concentration decreasing unit, which monitors the air-fuel ratio and catalyst temperature to adjust fuel addition amounts during the regeneration process, reducing fuel concentration and preventing high-concentration HC discharge by decreasing fuel addition when conditions indicate incomplete burning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fuel is added to increase temperature for particulate matter regeneration, then the exhaust purifying filter can be regenerated, but high-concentration unburned hydrocarbons are discharged causing white smoke
Solution Approach 1:
The control unit continuously monitors the air-fuel ratio and catalyst temperature, using this feedback to dynamically adjust the fuel addition amount. When the air-fuel ratio falls outside the target range or temperature exceeds the upper limit, fuel addition is reduced or stopped, preventing excessive unburned hydrocarbons while maintaining effective regeneration.
Solution Approach 2:
The system changes the fuel addition amount as a variable parameter based on real-time conditions. By adjusting the fuel addition amount according to the air-fuel ratio and temperature measurements, the system optimizes the balance between achieving sufficient temperature for regeneration and preventing excessive unburned hydrocarbon discharge.
2Reliability
If fuel addition amount is increased to ensure sufficient burning, then complete combustion is improved, but the risk of white smoke increases when oxygen concentration is low
Solution Approach 1:
The control unit uses feedback from air-fuel ratio sensors and temperature sensors to dynamically adjust fuel addition. When oxygen concentration is low (indicated by air-fuel ratio outside target range), the system reduces fuel addition to prevent incomplete combustion and white smoke, while still providing enough fuel for effective regeneration when conditions permit.
Solution Approach 2:
The fuel addition amount is made dynamic rather than fixed, changing in real-time based on operating conditions. The system transitions between different fuel addition strategies: higher addition when oxygen is abundant for reliable burning, and reduced addition when oxygen is scarce to prevent white smoke.
3Ease of operation
If the glow plug is used to heat the combustion chamber for fuel atomization, then fuel burning is promoted, but the added fuel cannot be directly heated in the exhaust system
Solution Approach 1:
The exhaust gas itself serves as an intermediary heat transfer medium. The hot exhaust gas from the combustion chamber passes through the exhaust purifying filter and carries thermal energy that heats the added fuel in the exhaust system, enabling effective atomization and burning without requiring direct glow plug contact with the added fuel.
Solution Approach 2:
The exhaust system uses its own thermal energy to facilitate fuel atomization and burning. The heat generated by the combustion process is recycled through the exhaust gas flow to pre-heat the added fuel, creating a self-sustaining thermal field that promotes complete combustion of the added fuel.
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 system effectively prevents the discharge of high-concentration HC and white smoke by adjusting fuel addition based on real-time air-fuel ratio and temperature feedback, ensuring efficient burning and regeneration of particulate matter, even in conditions with low oxygen concentration or turbocharger interference.
Implementation Method 1
an exhaust purifying filter that can be regenerated by oxidizing particulate matter deposited through filtering of an exhaust gas, utilizing catalytic function
Implementation Method 2
The fuel supplied by the delayed injection is burned in an expansion stroke
Implementation Method 3
a glow plug is used for heating a combustion chamber to promote atomization of the fuel
Implementation Method 4
When fuel is added to the exhaust gas of such a low oxygen concentration, HC concentration resulting from the added fuel would be imbalanced
Data Source
AI summary
Whether discharge of high-concentration, unburned fuel is indicated or not is determined based on air-fuel ratio AF, calculated air-fuel ratio AFc and exhaust temperature thco (S110, S112, S114). If it is determined that high-concentration, unburned fuel would be discharged (“no” in any of S110, S112, S114), amount of fuel addition per one addition is decreased in PM regeneration control (S116). Therefore, in a state where high concentration HC is to be discharged to the downstream of an exhaust purifying filter, the amount of fuel addition at one time is immediately decreased, so that discharge of high-concentration HC to the outside can be prevented, and generation of white smoke can reliably be prevented.