EGR Cooler Derate Strategy for Thermal Fatigue
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Solution Overview
Problem
EGR coolers in combustion engines face thermal fatigue and potential damage due to undesirable coolant temperature fluctuations, leading to increased costs and space requirements when oversized or high coolant flow rates are used to mitigate these issues, especially as emission standards become more stringent.
Innovation Solution
A method and system for actively controlling coolant temperature in EGR coolers by determining coolant pressure and temperature, calculating the boiling temperature, and adjusting engine operation through a derate strategy that reduces fuel delivery when the coolant temperature approaches boiling point, thereby regulating engine power to prevent damage and maintain optimal operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EGR cooler is oversized to prevent thermal fatigue and damage, then the reliability of the EGR cooler is improved, but the device complexity and space requirements increase
Solution Approach 1:
The patent applies dynamics by transitioning from a static, fixed EGR cooler design to a dynamic control system that continuously monitors coolant temperature and pressure, then actively adjusts engine operation parameters (fuel injection timing, EGR valve position, coolant flow rate) to maintain optimal thermal conditions. This dynamic approach allows a smaller, more compact cooler to operate reliably by adapting to changing thermal loads in real-time.
Solution Approach 2:
The patent utilizes parameter changes by continuously varying operational parameters (coolant temperature, pressure, flow rate, fuel injection timing, EGR rate) based on real-time sensor feedback. The control system adjusts these parameters to maintain the coolant temperature within safe operating margins below the boiling point, thereby preventing thermal fatigue without requiring an oversized cooler design.
2Reliability
If the coolant flow rate is increased to prevent thermal fatigue, then the reliability of the EGR cooler is improved, but the erosion in tubes and components increases
Solution Approach 1:
The control system dynamically adjusts coolant flow rate based on real-time thermal conditions rather than maintaining a constantly high flow rate. By monitoring coolant temperature and pressure, the system increases flow only when thermal loads require it, and reduces flow when conditions are favorable, thereby maintaining reliability while minimizing erosion-causing high-velocity flow conditions.
Solution Approach 2:
The patent implements feedback control by continuously measuring coolant temperature and pressure, comparing these measurements against target values, and adjusting the coolant pump speed and EGR valve position accordingly. This closed-loop feedback ensures that the coolant flow rate is optimized for thermal protection without excessive flow that would cause erosion, as adjustments are made only when and where needed.
3Ease of manufacture
If the coolant temperature is allowed to fluctuate above and below boiling temperatures, then the manufacturing costs are reduced, but thermal fatigue damages the EGR cooler
Solution Approach 1:
The patent employs feedback control through temperature and pressure sensors that continuously monitor coolant conditions. The control system uses this feedback to predict approaching boiling conditions and takes preventive action by adjusting engine operation and coolant flow before boiling occurs, thereby preventing thermal fatigue without requiring expensive oversized components or excessive flow rates.
Solution Approach 2:
The control system performs preliminary action by detecting early signs of approaching boiling conditions through temperature and pressure monitoring, then proactively adjusts operational parameters (reducing EGR rate, adjusting fuel injection timing, increasing coolant flow) before the coolant actually reaches boiling point. This preventive approach avoids thermal fatigue damage without requiring expensive design margins.
4Reliability
If the coolant flow rate is increased to prevent thermal fatigue, then the reliability of the EGR cooler is improved, but the energy consumption increases
Solution Approach 1:
The patent applies dynamics by using variable-speed coolant pumps and actively controlled EGR valves that adjust coolant flow rate and EGR timing based on real-time thermal demands. This dynamic control allows the system to maintain reliability by increasing flow only when necessary, rather than continuously operating at high flow rates, thereby significantly reducing energy consumption compared to traditional high-flow designs.
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 manages coolant temperature, preventing damage to EGR cooler components, optimizing engine performance, and reducing the need for oversized components or excessive coolant flow, while meeting stringent emission requirements.
Implementation Method 1
the coolant and/or the heated exhaust gases flow through tubes, a jacket, or other forms of conduits in the EGR cooler... causing heat from the exhaust gas to be transferred to the coolant
Implementation Method 2
heated exhaust gases flow through tubes, a jacket, or other forms of conduits in the EGR cooler... causing heat from the exhaust gas to be transferred to the coolant
Data Source
AI summary
Methods and systems for controlling the conditions of a coolant for the cooler of an exhaust gas recirculation system are disclosed. The system determines coolant pressure at predetermined location of the cooler. The system also senses the actual temperature of the coolant at a predetermined location of the cooler. The system also determines a coolant boiling temperature at the determined coolant pressure. Using the determined coolant pressure, the system may control engine operation so as to prevent coolant from reaching boiling in the cooler. An engine derate power factor may be determined to control the amount of fuel delivered to the engine, such as reducing the amount of fuel delivered through the fuel injectors. The amount of delivered fuel may be derated until an adjusted coolant temperature falls a predetermined amount below the coolant boiling temperature.