EGR Valve Progressiveness Matching for Air Flow Stability
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Solution Overview
Problem
Existing methods for controlling the flow of recirculated exhaust gases in combustion engines with EGR loops are inadequate, leading to variations in air flow and mixture richness, which result in inconsistent engine torque and increased pollutant emissions, particularly nitrogen oxides and particles, due to oscillations in the EGR valve shutter caused by pressure differences.
Innovation Solution
A process that desensitizes the air flow into the cylinders by determining the maximum allowable variations in EGR flow and effective section variations of the EGR valve, comparing the valve's progressiveness with its characteristics, and modifying the valve or operating points to ensure compatibility, thereby stabilizing the air flow and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the EGR valve shutter position is controlled to regulate exhaust gas flow, then the EGR loop can be adjusted to meet emission standards, but the shutter oscillates due to pressure differences causing variations in air flow and mixture richness
Solution Approach 1:
The patent determines the progressiveness of the EGR valve during the design phase and compares it with required characteristics before finalizing the valve design. This preliminary analysis prevents shutter oscillation issues by ensuring the valve geometry is appropriate for the intended operating conditions, rather than attempting to correct oscillation problems through control adjustments after deployment.
Solution Approach 2:
The patent modifies the geometric parameters of the EGR valve, specifically the progression of the effective section along the shutter travel, to optimize flow characteristics. By changing the valve geometry parameters rather than adjusting control parameters, the system achieves stable air flow control without shutter oscillation.
2Measurement precision
If additional sensors are added to measure physical characteristics of the EGR loop, then control precision can be improved, but device complexity and cost increase
Solution Approach 1:
The patent utilizes existing measurements (shutter position and basic pressure data) to calculate derived parameters such as effective section and progressiveness through mathematical relationships. This self-service approach extracts maximum information from minimal sensors, avoiding the need for additional expensive flow meters or pressure sensors while maintaining control precision.
3Speed
If the EGR valve is designed with high progressiveness to improve flow control, then response speed increases, but shutter oscillation amplitude increases leading to greater variations in engine torque and emissions
Solution Approach 1:
The patent optimizes the progressiveness parameter of the EGR valve to find the optimal balance between response speed and oscillation amplitude. By carefully selecting the progressiveness value and the geometric parameters that define it, the system achieves sufficiently fast response while keeping shutter oscillation and resulting emission variations within acceptable limits.
Data Source
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AI summary
The invention relates to a method for desensitizing the air flow Qair entering the cylinders of a heat engine provided with an EGR loop, that is desensitizing in relation to variations DeltaQegr of the gas flow Qegr passing through the EGR valve. According to said method, maximum admissible variations DeltaQegr are determined for points of stabilised operation of the engine; admissible effective section variations DeltaSeff are determined according to the variations DeltaQegr; the required progressivity of the EGR valve is determined according to the admissible effective section variations and the performance of the control system; and said required progressivity is compared with the characteristics of the EGR valve. The points of stabilised operation or the EGR valve itself are modified in such a way as to obtain a correlation between the required progressivity and the characteristics of the EGR valve.