Instantaneous EGR Mass Flow Estimation Using Crank Angle Sampling
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Solution Overview
Problem
Conventional EGR mass flow rate estimation techniques are inaccurate under transient engine operating conditions due to the pulsating nature of EGR flow, leading to inaccuracies in estimating instantaneous mass flow rates, which are crucial for diagnostic and engine control purposes.
Innovation Solution
A method and system that monitor engine position and sample EGR cooler outlet temperature, pressure differential across a flow restriction, and intake manifold pressure at high frequency to estimate instantaneous EGR mass flow rates using specific models, with constants stored in a memory unit for accurate calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional EGR mass flow rate estimation using average delta pressure is used, then the system is simple to operate, but measurement precision deteriorates under transient conditions
Solution Approach 1:
The patent transitions from static average-based estimation to dynamic instantaneous estimation by sampling parameters at multiple crank angle positions throughout the engine cycle. This allows the system to capture the pulsating nature of EGR flow during transient conditions while maintaining operational simplicity through automated processing of the sampled data.
Solution Approach 2:
The patent performs preliminary sampling of pressure differential, temperature, and density parameters at predetermined crank angle positions before computing the instantaneous mass flow rate. This preliminary data collection enables accurate capture of flow characteristics during transient conditions, resolving the contradiction between operational simplicity and measurement precision.
2Measurement precision
If high frequency sampling is performed to capture instantaneous flow rates, then measurement precision improves, but device complexity increases
Solution Approach 1:
The patent segments the engine cycle into multiple crank angle positions for sampling, allowing high-frequency capture of instantaneous flow characteristics without requiring continuous high-speed sampling throughout the entire cycle. This segmentation approach achieves measurement precision while limiting computational burden to specific critical points in the engine operation.
Solution Approach 2:
The patent performs sampling at specific crank angle positions rather than continuously throughout the entire engine cycle. This partial action approach captures the essential pulsating flow characteristics needed for accurate transient measurement while avoiding the excessive computational complexity of continuous high-frequency sampling.
3Device complexity
If average delta pressure is used for EGR flow estimation, then the system requires minimal sensors, but reliability deteriorates under transient operating conditions
Solution Approach 1:
The patent enhances reliability under transient conditions by implementing dynamic instantaneous mass flow rate estimation based on sampled parameters at multiple crank angle positions. This dynamic approach accurately captures pulsating EGR flow characteristics, resolving the reliability issue while maintaining relatively simple sensor requirements through efficient use of existing EGR system components.
Data Source
AI summary
A system and method are provided for estimating an instantaneous EGR mass flow rate corresponding to a flow rate of exhaust gas through an exhaust gas recirculation (EGR) conduit fluidly coupled between an exhaust manifold and an intake manifold of an internal combustion engine with an EGR cooler positioned in-line with the EGR conduit. An operating position of the engine is monitored, and the instantaneous EGR mass flow rate is estimated at each of a plurality of fixed increments of the engine position based on EGR cooler outlet temperature, intake manifold pressure and a pressure differential across a flow restriction disposed in-line with the exhaust gas conduit between the EGR cooler and the intake manifold.