Exhaust Gas Temperature Control via Combustion Mode Alternation
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Solution Overview
Problem
Existing methods for controlling the temperature of exhaust gases in heat engines during regeneration phases are inefficient, leading to potential catalyst damage and difficulty in maintaining stable pollutant treatment due to slow and sensitive state feedback control systems.
Innovation Solution
A method that alternates between rich and lean combustion modes to adjust thermal power, ensuring that excess energy in one mode is compensated by lack of energy in the other, maintaining the temperature of exhaust gases near a setpoint temperature, thereby optimizing pollutant treatment without relying on internal system state observations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If state feedback control is used to maintain catalyst temperature, then temperature control is attempted, but the response is slow and delayed making it impossible to avoid temperature overruns
Solution Approach 1:
The control system performs preliminary action by using a model to predict future catalyst temperature and thermal power requirements before they actually occur. The model anticipates temperature trends based on current operating conditions (exhaust gas flow, temperature, composition) and pre-calculates the necessary fuel injection adjustments, allowing the system to act proactively rather than reactively to temperature changes.
Solution Approach 2:
The system implements feedback by continuously comparing the predicted catalyst temperature with the target temperature and using this information to adjust fuel injection timing and quantity. The model updates its predictions based on actual temperature measurements from sensors, creating a closed-loop control system that refines its control actions over time to maintain optimal temperature.
2Measurement precision
If temperature sensor is placed inside the catalyst, then direct temperature measurement is achieved, but the implantation is difficult and risks catalyst integrity
Solution Approach 1:
The system uses an intermediary approach by placing temperature sensors downstream of the catalyst rather than inside it. A thermal model acts as an intermediary, translating the downstream temperature measurements into accurate predictions of the internal catalyst temperature. This indirect measurement method avoids the mechanical complexity and damage risks of internal sensor implantation while still providing precise temperature information.
Solution Approach 2:
The system creates a virtual copy of the catalyst's thermal behavior through mathematical modeling. Instead of physically inserting sensors into the catalyst monolith, the model replicates the internal temperature conditions based on measurable external parameters (exhaust gas properties, flow rates), providing the same information as internal sensors would without the physical intrusion.
3Reliability
If regeneration time is extended to ensure complete pollutant treatment, then treatment completeness is improved, but catalyst temperature may exceed maximum allowable temperature
Solution Approach 1:
The system applies dynamic control by continuously adjusting fuel injection timing and quantity based on real-time predictions of catalyst temperature and pollutant loading conditions. Rather than using fixed regeneration durations, the control strategy dynamically modifies injection parameters to maintain temperature within the optimal window, extending or shortening regeneration time as needed while preventing temperature excursions that would damage the catalyst.
Solution Approach 2:
The system changes operational parameters (fuel injection timing, injection quantity, air-fuel ratio) to maintain temperature within safe limits while ensuring complete pollutant treatment. By dynamically adjusting these parameters based on model predictions, the system can extend regeneration duration for complete treatment when conditions permit, or reduce duration and adjust other parameters to maintain temperature control when approaching thermal limits.
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 allows for precise control of catalyst temperature, preventing damage and ensuring optimal pollutant treatment, including nitrogen oxide reduction and soot combustion, while minimizing energy deviations and maintaining stable operation across varying engine conditions.
Implementation Method 1
a thermal engine, in particular during the regeneration phases of the post-treatment system
Implementation Method 2
a catalyst comprising a means of accumulation of nitrogen oxides called 'NOx-Trap' which is integrated in the exhaust line and in which the nitrogen oxides emitted during normal engine operation are trapped
Implementation Method 3
making it possible to eliminate the carbon monoxide and the hydrocarbons to be burned
Implementation Method 4
a particulate filter, for example a catalytic one, the inner wall of which is covered with a layer of a material impregnated with precious metals, called 'Wash Coat', providing an oxidation function intended to reduce the combustion temperature of soot particles
Data Source
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AI summary
The invention relates to a method for controlling the temperature of a gas post-treatment system (21, 22) in the exhaust circuit (2) of a thermal engine (10) having a more or less rich combustion mode, in which at least post-treatment member (21) is periodically submitted to regeneration phase at a set-point temperature (Ts). According to the invention, the duration of each regeneration phase is divided into a series of fractioned periods (t1 t2) (t2 t3)... for tuning the engine alternatively according to two combustion modes each having a different richness, respectively a mode (R) hotter than necessary for reaching the set-point temperature (Ts) and a mode that is not so hot (P), the duration of each period being controlled so that the excess energy (S) introduced during a hotter mode (R) period (t1 t2) is compensated by the lack of energy (D) in the following period (t2 t3) with the less hot mode (P), and conversely, in order to maintain at the output of the post-treatment member a mean temperature corresponding to the set-point temperature (Ts).