Dual Valve EGR System for NOx Reduction
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Solution Overview
Problem
Current EGR systems in diesel engines do not meet stringent NOx emission standards and are hindered by the need for selective catalytic reduction (SCR) systems, which are space-intensive, heavy, and require storage of urea or ammonia solutions, posing packaging and weight issues.
Innovation Solution
An EGR system with dual adjustable valves, a cold EGR valve and a hot EGR valve, in combination with a variable geometry turbocharger, allows for greater than 40% recirculation of exhaust gases, optimizing engine performance and bypassing the need for SCR systems by independently controlling airflow and EGR flow rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If SCR systems are used to meet NOx emission standards, then emission control effectiveness is improved, but system weight and occupied space increase significantly
Solution Approach 1:
The patent extracts and eliminates the SCR system from the emission control architecture, replacing it with an enhanced EGR system that achieves NOx reduction without requiring urea injection, catalysts, or associated heavy components. This removes the source of the weight problem while maintaining emission control functionality.
Solution Approach 2:
The patent changes the operating parameters of the EGR system by implementing dual-stage EGR with separate control of hot and cold EGR flows, enabling the system to achieve emission compliance through exhaust gas recirculation alone, thereby eliminating the need for SCR system components and reducing overall system weight.
2Object-affected harmful factors
If SCR systems are used to meet NOx emission standards, then emission control effectiveness is improved, but system complexity and packaging difficulty increase
Solution Approach 1:
The patent removes the SCR subsystem including urea storage tanks, injection systems, catalysts, and control electronics, retaining only the EGR functionality with enhanced dual-valve control. This extraction dramatically simplifies the overall emission control system architecture and reduces packaging complexity.
Solution Approach 2:
The enhanced EGR system performs multiple functions: it controls NOx formation through recirculation, manages combustion temperature, and eliminates the need for separate SCR components. This multi-functionality consolidates emission control into a single system, reducing overall complexity.
3Object-affected harmful factors
If large volume EGR is implemented with dual valves, then emission standards are met without SCR, but EGR system complexity increases
Solution Approach 1:
The patent segments the EGR control into two independent stages: hot EGR valve controlling exhaust gas extraction from the exhaust manifold, and cold EGR valve controlling recirculated gas injection into the intake manifold. This segmentation enables precise control of large EGR volumes while maintaining manageable system complexity through modular valve control.
Solution Approach 2:
The patent implements dynamic control of the dual EGR valves with independent actuation, allowing the system to adapt EGR rates in real-time based on operating conditions. This dynamic capability enables the system to achieve emission compliance across various load and speed conditions without requiring overly complex static control mechanisms.
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 configuration enables diesel engines to meet Tier4 emission standards without the use of SCR systems, reducing weight, space, and costs while maintaining efficient NOx reduction, thereby providing a more compact and effective emission control solution.
Implementation Method 1
The exhaust gases, which are recirculated to the engine cylinders, reduce the concentration of oxygen in the cylinders, which lowers the maximum combustion temperature in the cylinders and slows the chemical reaction of the combustion process
Implementation Method 2
A VGT turbine typically has a set of movable vanes to control pressure of the exhaust flowing through the VGT turbine. At low engine speeds when exhaust flow is low, the vanes are partially closed to accelerate the VGT turbine
Implementation Method 3
The compressor receives the air to be compressed and supplies the compressed air to the combustion chambers. The compressor may also be used to compress a fuel/air mixture as well as air
Data Source
AI summary
An EGR system is disclosed for reducing NOx emissions and that may eliminate the need for a SCR system. The disclosed EGR system includes dual valves, including a hot EGR valve disposed in the exhaust manifold and a cold EGR valve disposed upstream of the intake manifold. A VGT turbine with adjustable vanes may also be employed with a low pressure turbine. Intake air may proceed through both a high pressure compressor as well as a low pressure compressor and the high pressure compressor may be substantially bypassed by way of a bypass valve disposed between the low pressure compressor and the air intake. The EGR system may be controlled by adjusting the positions of the valves and VGT turbine vanes.