Exhaust Post-Treatment Temperature Control via Periodic Rich-Lean Cycling
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Solution Overview
Problem
Existing post-treatment devices for vehicle emissions, such as particulate filters and NOx traps, face challenges in maintaining optimal regeneration temperatures, leading to inefficient pollutant combustion and potential device damage due to temperature fluctuations and the difficulty of precise thermal control.
Innovation Solution
A method that alternates between rich and lean periods of engine operation to regulate the temperature of exhaust gases entering post-treatment devices, ensuring the average energy supplied maintains the temperature within a setpoint range optimal for regeneration, using fuel injection adjustments to compensate for energy excesses and deficits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the temperature of exhaust gases is increased to enable regeneration of post-treatment devices, then pollutant combustion efficiency is improved, but the risk of temperature spikes damaging the devices increases
Solution Approach 1:
The patent applies periodic action by alternating between rich combustion periods (which generate high temperature for regeneration) and lean combustion periods (which reduce temperature). This periodic switching allows the system to achieve the necessary temperature for effective pollutant combustion while preventing sustained high temperatures that could cause damage. The control unit systematically transitions between these combustion modes to maintain temperature within safe yet effective ranges.
Solution Approach 2:
The patent utilizes parameter changes by dynamically adjusting the fuel-air ratio between rich and lean conditions. During rich periods, the fuel-air ratio is increased to generate higher temperatures for regeneration. During lean periods, the fuel-air ratio is decreased to lower temperatures and prevent damage. This continuous parameter adjustment enables the system to optimize combustion efficiency while protecting the post-treatment devices from thermal damage.
2Temperature
If fuel injection is increased to raise exhaust gas temperature for regeneration, then the temperature reaches the setpoint range, but energy consumption increases
Solution Approach 1:
The system applies periodic action by implementing alternating rich and lean combustion periods. During rich periods, increased fuel injection raises the exhaust gas temperature to the required setpoint range for regeneration. During lean periods, fuel injection is reduced to lower energy consumption. This periodic pattern allows the system to achieve necessary temperature levels for effective regeneration while minimizing overall energy consumption through the lean recovery periods.
Solution Approach 2:
The patent maintains continuity of useful action by ensuring that the regeneration process continues effectively throughout the alternating rich-lean cycles. The rich periods provide the necessary thermal energy for pollutant combustion, while the lean periods allow the system to recover energy and prepare for the next regeneration cycle. This continuous alternation ensures sustained regeneration effectiveness without excessive energy consumption.
3Productivity
If the temperature is maintained at a constant high level for regeneration, then pollutant treatment efficiency is maximized, but the device lifespan is reduced due to thermal stress
Solution Approach 1:
The patent applies periodic action by systematically alternating between high-temperature rich combustion periods (which maximize pollutant treatment efficiency through effective regeneration) and lower-temperature lean combustion periods (which reduce thermal stress on the devices). This periodic temperature variation allows the system to achieve high treatment efficiency during rich periods while extending device lifespan during lean recovery periods, preventing the cumulative thermal damage that would result from continuous high-temperature operation.
Solution Approach 2:
The system implements beforehand cushioning by incorporating lean combustion periods that act as thermal buffer zones between intense rich combustion events. These lean periods allow the post-treatment devices to cool down and recover from thermal stress before the next high-temperature regeneration cycle begins, thereby cushioning against cumulative thermal damage and extending device lifespan while maintaining overall treatment efficiency.
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 stabilizes the temperature of post-treatment devices during regeneration phases, enhancing the efficiency of pollutant combustion and extending device lifespan by preventing temperature overruns, thus optimizing the treatment of both soot and nitrogen oxides.
Implementation Method 1
fuel can be injected just after top dead center during the power stroke, which increases the exhaust gas temperature. Thus, the fuel injection rate into the combustion chambers of the cylinders can be adjusted as needed, so as to operate in a richer or leaner combustion mode and obtain a variation in the temperature of the exhaust gases
Implementation Method 2
it is known to trap these particles present in the exhaust gases by installing a particulate filter in the exhaust line downstream of the engine's combustion chambers. Such a filter is designed to retain the particles in the exhaust gases that pass through it
Implementation Method 3
a catalyst is typically installed in the exhaust system. This catalyst incorporates a nitrogen oxide accumulation device called a 'NOx trap,' in which the nitrogen oxides emitted during normal engine operation are trapped. The operation of such a nitrogen oxide accumulation catalyst... nitrogen oxides emitted during normal engine operation are trapped
Implementation Method 4
decompose nitrates by releasing NOx which is then reduced to nitrogen by reducing agents such as H2, HC, and CO contained in the exhaust gases
Implementation Method 5
these combustion, oxidation, adsorption, and reduction reactions are directly dependent on the temperature of the support material for these aftertreatment devices and the gases passing through them
Data Source
Figure 1~2
Figure 3
AI summary
Method of controlling the temperature of a device (9, 10) for the post-treatment of motor-vehicle exhaust gases, the post-treatment device (9, 10) having a normal operating phase in which it traps and accumulates polluting elements from the exhaust gases and a regeneration phase during which these accumulated polluting elements are burnt off so as to regenerate the post-treatment device (9, 10), characterized in that each regeneration phase is divided into a succession of fractional periods (t1-t2), (t2-t3),..., in which the temperature of the exhaust gases entering the post-treatment device is alternately hotter, in a rich period (R), and cooler, in a lean period (P), and in that the duration of the rich (R) and lean (P) periods are determined, respectively, according to the duration of at least one lean period (P) and at least one rich period (R), so that the surplus energy provided in a rich period (R) is compensated for by a lack of energy in a lean period (P) so that the average energy supplied to the post-treatment device (9, 10) enables the temperature at the exit of the post-treatment device (9, 10) to remain close and on average equal to an optimum setpoint temperature (Tsetpoint) for the regeneration phase.