Dual EGR Flowpath Controller for Exhaust Temperature Management
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Solution Overview
Problem
Internal combustion engines face challenges in efficiently managing exhaust gas temperatures for optimal operation of exhaust aftertreatment devices, particularly in maintaining the devices within desired temperature regions for efficient purification and minimizing fuel consumption.
Innovation Solution
The system employs a controller to monitor exhaust gas temperatures and adjust the split between first and second EGR flow paths based on temperature, engine speed, and load parameters, operating in aftertreatment warm-up or EGR split modes to optimize the thermal energy usage and maintain the exhaust purifying device within a desired temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a single EGR flowpath is used to recirculate exhaust gas, then the system structure is simple, but the ability to control exhaust gas temperature and optimize aftertreatment device operation is limited
Solution Approach 1:
The single EGR flowpath is segmented into two separate flowpaths: a first EGR flowpath that extracts exhaust gas from the exhaust manifold upstream of the aftertreatment device, and a second EGR flowpath that extracts exhaust gas from downstream of the aftertreatment device. This segmentation enables independent control of hot EGR (for temperature management) and cold EGR (for NOx reduction), resolving the contradiction between temperature control capability and system simplicity.
Solution Approach 2:
The system employs dynamic control of two EGR valves with different characteristics (a first EGR valve and a second EGR valve) to adjust the split between hot and cold EGR flowpaths based on operating conditions. The controller dynamically adjusts valve positions to optimize exhaust gas temperature and aftertreatment device operation, transforming a static single-flowpath system into a dynamic multi-flowpath system.
2Temperature
If fuel-injection strategies are used to increase exhaust gas temperature for aftertreatment warm-up, then the aftertreatment device reaches operating temperature faster, but fuel consumption increases
Solution Approach 1:
The system converts the typically wasted thermal energy in exhaust gas into a beneficial resource for warming up the aftertreatment device. By routing exhaust gas through the first EGR flowpath during cold operation and controlling the first EGR valve to regulate hot EGR flow, the system uses the exhaust gas's thermal energy to heat the aftertreatment device, eliminating the need for additional fuel injection and converting what would be waste heat into a useful warming function.
Solution Approach 2:
The system changes the temperature parameter of the recirculated exhaust gas by selecting different flowpaths: using the first EGR flowpath (hot EGR from upstream) to increase exhaust gas temperature for aftertreatment warm-up, and using the second EGR flowpath (cold EGR from downstream) when the aftertreatment device is at operating temperature. This parameter change enables temperature control without fuel consumption increases.
3Productivity
If exhaust gas recirculation is increased to reduce NOx emissions, then aftertreatment purification efficiency improves, but in-cylinder combustion temperature control becomes more difficult
Solution Approach 1:
The EGR system is segmented into two temperature-regulated flowpaths that can be independently controlled. The first EGR flowpath provides hot recirculated gas that can be used to maintain combustion temperature when high EGR rates are needed for purification, while the second EGR flowpath provides cold recirculated gas for when temperature reduction is desired. This segmentation allows the system to achieve high purification efficiency while maintaining appropriate combustion temperatures through selective flowpath usage.
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 enhances the efficiency of exhaust gas purification by optimizing the recirculation of exhaust gases, reducing the need for fuel-injection strategies that increase fuel consumption, and maintaining the exhaust purifying device within a temperature range that ensures high conversion efficiency and combustion efficiency.
Implementation Method 1
A first EGR valve is disposed to control flow of exhaust gas between the exhaust manifold and the air intake system, wherein a first flow path is defined between the exhaust manifold, the first EGR valve and the air intake system
Implementation Method 2
A second EGR valve is disposed to control flow of exhaust gas between an inlet that is disposed downstream of the exhaust purifying device and the air intake system, wherein a second flow path is defined between the inlet disposed downstream of the exhaust purifying device, the second EGR valve and the air intake system
Implementation Method 3
A temperature sensor is disposed in the exhaust gas feedstream upstream of the exhaust purifying device
Implementation Method 4
control the first valve to control flow of exhaust gas to the air intake system via the first flow path and control the second valve to control flow of exhaust gas to the air intake system via the second flow path based upon the temperature of the exhaust gas feedstream upstream of the exhaust purifying device
Data Source
AI summary
An internal combustion engine system includes a first EGR valve to control flow in a first flow path, and a second EGR valve to control flow in a second flow path. A temperature sensor is disposed in the exhaust gas feedstream upstream of the exhaust purifying device, and a controller is in communication with the internal combustion engine and the temperature sensor and is operatively connected to the first and second EGR valves. The controller executes a routine to monitor the temperature of the exhaust gas feedstream upstream of the exhaust purifying device and control the first valve to control flow of exhaust gas to the air intake system via the first flow path and control the second valve to control flow of exhaust gas to the air intake system via the second flow path based upon the temperature of the exhaust gas feedstream upstream of the exhaust purifying device.