Dual-Path EGR Control for Combustion Stability
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Solution Overview
Problem
Conventional EGR control apparatuses for internal combustion engines fail to accurately control the amount and ratio of inert gas supplied to cylinders, leading to unstable combustion and increased exhaust emissions, particularly during transient operating conditions due to differences in response time and path length of low-pressure and high-pressure EGR devices.
Innovation Solution
An EGR control apparatus that calculates and controls separate EGR inputs for first and second EGR devices, with the second device having a shorter path and higher response, to accurately supply inert gas, using estimated inert gas parameters and feedback control algorithms to compensate for delays and ensure stable combustion and reduced emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the low-pressure EGR device uses a longer recirculation path to cool exhaust gases, then the EGR gas temperature is reduced improving combustion stability, but the response time increases and dead time increases making inert gas control inaccurate
Solution Approach 1:
The EGR system is divided into two separate devices: a low-pressure EGR device for temperature control and a high-pressure EGR device for rapid response. Each device handles different aspects of the EGR function, allowing the system to simultaneously achieve cooled EGR gas and fast response without compromise.
Solution Approach 2:
The high-pressure EGR device acts as an intermediary that compensates for the delay in the low-pressure EGR device. By controlling both devices coordinate dly, the system uses the high-pressure device to bridge the time gap caused by the longer path in the low-pressure device.
2Device complexity
If the EGR control apparatus uses a single EGR device, then the device complexity is low, but the ability to accurately control inert gas amount and ratio during transient conditions is insufficient
Solution Approach 1:
The control function is segmented between two EGR devices with different characteristics. The low-pressure device provides stable temperature control while the high-pressure device provides rapid response capability, together achieving precise inert gas control that neither device could achieve alone.
Solution Approach 2:
The system changes operating parameters by switching between and combining two different EGR paths. By adjusting the contribution of each device based on operating conditions, the system adapts to maintain accurate inert gas control across different engine states.
3Quantity of substance
If the low-pressure EGR device supplements insufficient high-pressure EGR gas, then the total EGR amount is maintained, but the inert gas amount becomes short or excessive due to response delay
Solution Approach 1:
The control apparatus uses feedback control to monitor and adjust the inert gas amount by coordinating both EGR devices. The control unit calculates appropriate control inputs for each device based on actual engine conditions and the desired inert gas target, compensating for the delayed response of the low-pressure device.
Solution Approach 2:
The high-pressure EGR device provides preliminary action by rapidly delivering EGR gas before the low-pressure device completes its slower recirculation process. This preliminary delivery ensures that inert gas requirements are met without waiting for the delayed low-pressure device.
Data Source
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AI summary
An EGR control apparatus for an internal combustion engine, which is capable of accurately controlling an inert gas amount and an inert gas ratio of two types of EGR gas supplied to cylinders of the engine via two paths different from each other, thereby making it possible to ensure a stable combustion state and reduced exhaust emissions. The EGR control apparatus includes a low-pressure EGR device, a high-pressure EGR device, and an ECU. The ECU calculates a target low-pressure opening, calculates an estimated value of an in-cylinder low-pressure inert gas flow rate, which is the estimated value of an inert gas amount included in low-pressure EGR gas supplied to the cylinders via an intake passage, calculates a target high-pressure opening using the estimated value, and controls low-pressure and high-pressure EGR control valves, using the target low-pressure opening and the target high-pressure opening.