Spark-Ignited Engine EGR Control for High-Altitude Output
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Solution Overview
Problem
Exhaust gas recirculation in high load ranges leads to significant decreases in maximum output when intake air density decreases with increasing altitude, as existing control methods fail to effectively manage exhaust gas recirculation rates.
Innovation Solution
The control method adjusts the exhaust gas recirculation rate based on intake air density, reducing the recirculation rate when air density is low, and sets a density threshold that varies with outside air temperature to minimize knocking and maintain maximum output by optimizing the EGR valve position and ignition timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If exhaust gas recirculation is performed in high load range to minimize knocking and reduce exhaust gas temperature, then knocking is reduced and exhaust gas temperature is lowered, but maximum output decreases significantly when intake air density decreases at high altitude
Solution Approach 1:
The patent applies dynamics by making the exhaust gas recirculation rate adjustable based on operating conditions. The EGR rate is dynamically changed according to intake air density: at high altitude with low density, the EGR rate is reduced to maintain maximum output, while at low altitude with high density, the EGR rate is increased to minimize knocking. This dynamic adjustment resolves the contradiction between knocking reduction and power maintenance.
Solution Approach 2:
The patent changes the parameter of exhaust gas recirculation rate based on intake air density conditions. By monitoring intake air density and adjusting the EGR rate accordingly, the system optimizes performance for different altitude conditions. This parameter change approach allows the engine to maintain maximum output at high altitude while still achieving knocking reduction benefits when conditions permit.
2Object-generated harmful factors
If exhaust gas recirculation rate is increased to reduce NOx content in medium load range, then NOx emission is reduced, but engine output decreases when intake air density is low
Solution Approach 1:
The patent adjusts the exhaust gas recirculation rate parameter based on intake air density measurements. When intake air density is high (low altitude), a higher EGR rate is applied to reduce NOx emissions. When intake air density is low (high altitude), the EGR rate is reduced to maintain engine output. This conditional parameter adjustment resolves the contradiction between emission reduction and power maintenance.
Data Source
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AI summary
An internal combustion engine (1) is a spark-ignition internal combustion engine comprising a turbocharger (2) and an exhaust gas recirculation device, and operation according to a stoichiometric air-fuel ratio is performed by performing exhaust gas recirculation even in a high-load range including a maximum-output operation point. When the maximum output operation point is required (step 1), intake air information such as atmospheric pressure and outside air temperature (step 2) is used as a basis to calculate intake air density (ρ) (step 3), which is compared with a predetermined density threshold (ρ#) (step 4). When the intake density (ρ) is equal to or less than the density threshold (ρ#) at a high-altitude location or the like, an exhaust gas recirculation rate is set to 0 (step 6). As a result, the maximum output can be higher than when exhaust gas recirculation is performed.