EGR Quantity Estimation via Segmented Gas Flow Models
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Solution Overview
Problem
Existing EGR systems fail to accurately estimate the quantity of recirculated exhaust gas flowing into a cylinder, especially during transitional engine running conditions, resulting in estimation errors that exceed allowable limits and hinder fuel economy improvements.
Innovation Solution
An apparatus that includes multiple computational means to simulate gas behavior through various engine components, such as an intake valve model, EGR valve model, and EGR diffusion model, along with measurement correction, to accurately estimate the recirculated exhaust gas quantity by calculating total gas flow, exhaust gas flow, and intake air pressure, thereby improving estimation accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an EGR valve model and EGR diffusion model are used to compute exhaust gas quantity, then the system can operate with simple structure, but the estimation accuracy deteriorates during transitional running conditions
Solution Approach 1:
The patent segments the gas flow computation into three distinct components: total gas flow through the intake valve (first computation means), exhaust gas flow through the EGR valve (second computation means), and temporal exhaust gas flow into the cylinder (third computation means using EGR diffusion model). This segmentation allows each component to be modeled separately and combined to achieve high accuracy without requiring an overly complex unified model.
Solution Approach 2:
The patent introduces an intermediary approach by using the relationship between total gas flow, exhaust gas flow, and intake air flow as a mediating framework. By computing the quantity of intake air flowing into the cylinder as the difference between total gas flow and temporal exhaust gas flow, and then using this corrected intake air quantity to derive intake air pressure, the system achieves accurate exhaust gas quantity estimation without directly measuring it.
2Device complexity
If simple EGR valve model is used, then device complexity is reduced, but estimation error exceeds allowable range during transitional conditions
Solution Approach 1:
The patent applies dynamics by making the computation adaptive to engine operating conditions. The system dynamically selects and combines different computational models (intake valve model, EGR valve model, EGR diffusion model) based on the current engine state, allowing accurate estimation during both stable and transitional running conditions without requiring a fixed complex model structure.
Solution Approach 2:
The patent implements feedback by using the computed intake air pressure (derived from corrected intake air quantity) to refine the exhaust gas quantity estimation. The measured intake air pressure is compared with the computed intake air pressure, and this feedback loop enables continuous refinement of the estimation, ensuring reliability during transitional conditions while maintaining model simplicity.
Data Source
AI summary
An apparatus estimates a quantity of recirculated exhaust gas. The apparatus includes a first unit computing a total quantity of gas, a second unit computing a quantity of exhaust gas passing through an EGR vale by means of an EGR valve model, a third unit computing a temporal quantity of the exhaust gas by means of an EGR diffusion model which simulates a behavior of the exhaust gas, a fourth unit obtaining an intake air quantity by subtracting the temporal exhaust gas quantity from the total gas quantity, a fifth unit correcting the computed intake air quantity by means of intake air quantity measured by the airflow meter, a sixth unit computing an intake air pressure based on the corrected quantity of the intake air, and a seventh unit computing a quantity of the recirculated exhaust gas based on at least the intake air pressure.