Split Exhaust Engine EGR Valve Control for Reverse Flow Prevention
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Solution Overview
Problem
Engine knock occurs due to increased combustion temperatures under boosted conditions, and the addition of an electric compressor can lead to reverse flow through the EGR passage, reducing engine efficiency and increasing emissions.
Innovation Solution
A method is implemented where the position of a valve in the EGR passage is adjusted based on the pressure in the first exhaust manifold, ensuring that the electric compressor does not create excess vacuum, thereby reducing reverse flow and optimizing engine efficiency and emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If an electric compressor is added upstream of the turbocharger compressor to increase boost and reduce turbo lag, then engine power density and response are improved, but intake air may flow in reverse through the EGR passage into the exhaust passage, reducing engine efficiency and increasing emissions
Solution Approach 1:
A controller monitors the operating conditions of the engine and adjusts the position of the EGR valve based on feedback signals. When the electric compressor is activated and intake pressure exceeds exhaust pressure in the first exhaust manifold, the controller modulates the EGR valve to close partially or fully, preventing reverse flow of intake air through the EGR passage into the exhaust passage, thus maintaining engine efficiency and reducing emissions while allowing the electric compressor to provide necessary boost
2Adaptability or versatility
If the EGR valve remains open during electric compressor operation, then exhaust gas recirculation continues, but intake air flows in reverse through the EGR passage, increasing emissions and reducing catalyst efficiency
Solution Approach 1:
The EGR valve is designed with dynamic positioning capability, allowing it to adjust its opening degree continuously based on operating conditions. During electric compressor operation, when reverse flow is detected or anticipated, the valve dynamically transitions to a closed or partially closed position, preventing intake air from entering the exhaust passage. This dynamic adjustment ensures that the system adapts to changing pressure conditions, maintaining low emissions while preserving the ability to utilize EGR when appropriate
3Stress or pressure
If the electric compressor creates excess vacuum in the intake passage, then boost pressure increases, but reverse flow through the EGR passage occurs, degrading compressor performance and increasing emissions
Solution Approach 1:
The EGR valve serves as an intermediary component between the intake passage and the exhaust passage. During electric compressor operation, when the compressor creates excess vacuum or high intake pressure that could cause reverse flow, the EGR valve acts as a mediator by closing or partially closing to block the EGR passage. This prevents the harmful interaction between the high-pressure intake air and the exhaust passage, eliminating reverse flow while allowing the electric compressor to maintain necessary boost pressure levels
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 adjustment reduces engine knock, increases efficiency, and minimizes emissions by preventing reverse flow through the EGR passage, enhancing engine performance under boosted conditions.
Implementation Method 1
an electric compressor positioned upstream of a turbocharger compressor in an intake passage
Implementation Method 2
adjusting a position of a valve in an exhaust gas recirculation (EGR) passage coupled between the intake passage and a first exhaust manifold of a first set of exhaust valves, based on a pressure in the first exhaust manifold
Implementation Method 3
the electric compressor may be driven by a turbocharger turbine disposed in an exhaust passage coupled to a second exhaust manifold of a second set of exhaust valves
Data Source
AI summary
Methods and systems are provided for operating a split exhaust engine system that provides blowthrough air and exhaust gas recirculation to an intake passage via a first exhaust manifold and exhaust gas to an exhaust passage via a second exhaust manifold. In one example, in response to an electric motor driving an electric compressor positioned upstream of a turbocharger compressor disposed in the intake passage, a position of a valve in an exhaust gas recirculation (EGR) passage coupled between the intake passage and the first exhaust manifold may be adjusted based on a pressure in the first exhaust manifold.