Engine EGR Control for High-Altitude Output Optimization
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Solution Overview
Problem
Existing control methods for internal combustion engines with exhaust gas recirculation devices fail to optimize engine output in high-speed high-load regions, particularly at high altitudes and low atmospheric pressures, leading to decreased performance due to excessive exhaust gas recirculation rates.
Innovation Solution
The system controls the exhaust gas recirculation rate by setting a target rate where the first output limit, associated with knock and exhaust temperature, equals the second output limit, influenced by atmospheric pressure or vehicle running speed, to maximize engine output while avoiding limitations such as air quantity and thermal management constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the exhaust gas recirculation rate is increased to suppress knock and reduce exhaust temperature, then the engine output can be increased, but the engine output decreases due to air quantity limitation at high altitudes
Solution Approach 1:
The patent implements dynamic control of the exhaust gas recirculation rate by continuously adjusting it based on real-time atmospheric pressure conditions. The control device modifies the target exhaust gas recirculation rate dynamically according to atmospheric pressure changes, ensuring optimal balance between knock suppression and maintaining sufficient air quantity for engine output, particularly adapting to high altitude conditions where atmospheric pressure is lower.
Solution Approach 2:
The patent changes the control parameter from a fixed exhaust gas recirculation rate to a variable rate determined by atmospheric pressure. The control device calculates a target exhaust gas recirculation rate that varies with atmospheric pressure conditions, allowing the system to adapt to different environmental conditions (sea level, high altitude) and maintain optimal engine performance by adjusting the recirculation rate parameter according to actual atmospheric conditions.
2Power
If the exhaust gas recirculation rate is increased to enable high-speed high-load operations, then the engine can operate at theoretical air fuel ratio, but the engine output decreases under thermal management constraints at low vehicle running speeds
Solution Approach 1:
The patent implements dynamic adjustment of the exhaust gas recirculation rate based on vehicle running speed conditions. The control device continuously monitors vehicle speed and adjusts the target exhaust gas recirculation rate accordingly, reducing the recirculation rate at low vehicle speeds to maintain thermal balance and prevent overheating, while allowing higher recirculation rates at higher speeds where thermal management is less constrained.
Solution Approach 2:
The patent changes the exhaust gas recirculation rate parameter dynamically based on vehicle running speed. The control device modifies the target recirculation rate according to speed conditions, creating a variable control strategy that adapts to different operating scenarios (towing, normal driving, high-speed operation), ensuring optimal balance between knock suppression and thermal management across the entire operating range.
Data Source
Figure 1
Figure 2
Figure 3(a)~3(b)
AI summary
A first output limit value (P1) is determined as an intersection point of a knock-limit output line (L1) which is set according to an exhaust gas recirculation rate and ignition timing and an exhaust-temperature-limit output line (L2) which is set according to the exhaust gas recirculation rate and ignition timing; a second output limit value (P2) is determined as an intersection point of the knock-limit output line (L1) and an air-quantity-limit output line (L3) which is set according to the exhaust gas recirculation rate, ignition timing and atmospheric pressure; and a third output limit value (P3) is determined as an intersection point of the knock-limit output line (L1) and a thermal-management-limit output line (L4) which is set according to the exhaust gas recirculation rate, ignition timing and vehicle running speed (steps 3 to 5). A value of the exhaust gas recirculation rate at which the condition "P1≥P2 or P1≥P3" is satisfied is set as a target exhaust gas recirculation rate (steps 6 and 8).