EGR Valve Control via Exhaust Manifold Temperature Estimation
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Solution Overview
Problem
Internal combustion engines with cooled exhaust gas recirculation (EGR) systems face fouling issues due to hydrocarbon condensation, particularly at low exhaust manifold gas temperatures, leading to decreased efficiency and the need for complex anti-fouling mechanisms or larger cooler designs.
Innovation Solution
A method using a temperature sensor signal from the EGR cooler exhaust gas outlet to estimate exhaust manifold gas temperature, allowing the engine control unit to command the EGR valve to close or partially close, preventing fouling by modeling or inferring low temperatures that cause hydrocarbon condensation, and monitoring application-specific conditions to manage EGR valve operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EGR cooler is designed with anti-fouling features and increased size to cope with condensation, then the cooler can handle hydrocarbon condensation, but the cooler design becomes complicated and costly
Solution Approach 1:
The control system performs preliminary action by predicting low exhaust manifold gas temperatures using a model based on EGR cooler outlet temperature and engine operating conditions. When low temperatures are predicted, the EGR valve is commanded to close in advance, preventing hydrocarbon condensation and fouling before it occurs. This eliminates the need for complex anti-fouling design features in the cooler.
Solution Approach 2:
The system uses feedback by continuously monitoring EGR cooler outlet temperature and engine operating conditions, processing these signals through a model to estimate exhaust manifold gas temperature, and using this information to control the EGR valve position. This closed-loop feedback control prevents fouling by adjusting EGR flow based on real-time temperature predictions.
2Reliability
If the EGR valve is commanded to close during extended idling to mitigate fouling, then fouling is reduced, but EGR system efficiency is decreased
Solution Approach 1:
The system changes the control parameter from simple time-based idle detection to model-based temperature prediction. By using a thermal model that considers engine operating conditions and EGR cooler outlet temperature, the system accurately predicts exhaust manifold gas temperature and commands the EGR valve based on actual temperature conditions rather than arbitrary idle time thresholds, maintaining efficiency while preventing fouling.
Solution Approach 2:
The invention replaces the mechanical/time-based idle detection mechanism with an electronic control system that uses temperature sensing and model-based calculation. This substitution allows for more precise and adaptive control of the EGR valve, closing it only when actual low temperature conditions are predicted rather than during all extended idle periods, thus maintaining EGR system efficiency.
3Measurement precision
If a temperature sensor is placed upstream of the EGR cooler to directly measure exhaust manifold gas temperature, then accurate temperature measurement is obtained, but the sensor operates at high temperature reducing reliability
Solution Approach 1:
The system uses an intermediary approach by placing the temperature sensor downstream of the EGR cooler where temperatures are lower and more reliable for sensing. A thermal model then acts as an intermediary calculation tool, using the downstream temperature measurement along with engine operating conditions to estimate the upstream exhaust manifold gas temperature. This indirect measurement approach maintains both sensor reliability and temperature measurement accuracy.
Solution Approach 2:
The system creates a computational copy of the upstream temperature condition by using a thermal model that calculates exhaust manifold gas temperature based on downstream sensor readings and engine operating parameters. This model-based copy provides accurate upstream temperature information without requiring a physical sensor in the high-temperature environment.
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 effectively reduces EGR system component fouling, maintaining higher efficiency without requiring complicated anti-fouling features or increased cooler size, by accurately predicting and mitigating hydrocarbon condensation under various engine conditions.
Implementation Method 1
EGR coolers are heat exchangers that typically use engine coolant to cool exhaust gas being recirculated into the intake system of the engine
Implementation Method 2
Various compounds may condense and deposit on interior surfaces of engine components when exhaust gas is cooled
Data Source
AI summary
An EGR control method to prevent condensation within the EGR system uses a temperature sensor signal from an EGR cooler exhaust gas outlet to model or estimate exhaust manifold gas temperature upstream of the cooler. If the estimated exhaust manifold gas temperature falls below a predetermined level, the engine control system closes or partially closes the EGR control valve to stop EGR flow through the cooler and the EGR valve.