EGR Cooler Recirculation Valve Thermal Gradient Control
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Solution Overview
Problem
The large thermal gradient across exhaust gas recirculation (EGR) coolers in internal combustion engines leads to thermo-mechanical issues and performance degradation due to the high exhaust gas temperature and low coolant temperature, causing stress on the EGR cooler.
Innovation Solution
The system recirculates cooled exhaust gas from the EGR cooler outlet back to its inlet, reducing the thermal gradient and controlling the EGR cooler recirculation valve based on inlet temperature to manage the flow, thereby lowering the temperature of the gas entering the EGR cooler.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the EGR cooler uses high-temperature exhaust gas and low-temperature coolant to achieve adequate cooling, then the cooling effectiveness is improved, but the thermal gradient across the EGR cooler increases leading to thermo-mechanical issues
Solution Approach 1:
The system pre-cools the exhaust gas by mixing it with cooled EGR from the recirculation passage before the exhaust gas enters the EGR cooler. This preliminary cooling action reduces the inlet temperature to the EGR cooler, thereby reducing the thermal gradient and thermal stress while maintaining adequate cooling effectiveness through the coolant system.
Solution Approach 2:
The recirculation passage acts as an intermediary system that introduces cooled EGR as a mediator substance to mix with the hot exhaust gas before it enters the EGR cooler. This intermediary cooled EGR reduces the thermal shock and thermal gradient on the EGR cooler walls while still allowing effective heat transfer to the coolant.
2Strength
If the EGR cooler recirculation valve is controlled based on inlet temperature, then the thermal load on the EGR cooler is reduced, but the system complexity increases
Solution Approach 1:
The EGR cooler recirculation valve is controlled by a controller that receives feedback from a temperature sensor monitoring the inlet temperature of the EGR cooler. The controller adjusts the valve position based on the measured temperature to maintain optimal thermal conditions, reducing thermal load and improving durability through closed-loop control.
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 reduces the thermal load on the EGR cooler, prolonging its lifespan and maintaining engine performance by minimizing thermal stresses and optimizing cooling efficiency.
Implementation Method 1
the thermal gradient across the EGR cooler may be relatively large due to the high exhaust gas temperature and the relatively low-temperature coolant at the inlet of the EGR cooler. This temperature gradient may lead to EGR cooler thermo-mechanical issues
Implementation Method 2
The EGR cooler may be a liquid-to-air heat exchanger that cools the EGR via coolant from an engine coolant system
Data Source
AI summary
Various systems and methods are provided for exhaust gas recirculation. In one example, an exhaust gas recirculation (EGR) system includes an EGR passage coupling an engine exhaust system to an engine intake system, an EGR cooler positioned in the EGR passage, a recirculation passage coupling an outlet of the EGR cooler to an inlet of the EGR cooler, an EGR cooler recirculation valve positioned in the recirculation passage and controllable to change a flow of exhaust gas though the recirculation passage, and a controller configured to adjust a position of the EGR cooler recirculation valve based on a temperature at the inlet of the EGR cooler.