Scavenging Mode Emission Control via Oxygen Sensor Feedback
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Solution Overview
Problem
Turbocharged internal combustion engines face increased emissions during scavenging due to differences in in-cylinder air/fuel ratio and exhaust gas air/fuel ratio, which existing engine control systems fail to accurately account for, leading to performance issues and emission increases.
Innovation Solution
A control system and method that utilize an exhaust oxygen sensor and a controller to adjust the in-cylinder air/fuel ratio and exhaust system temperature based on the scavenging ratio, ensuring a target exhaust gas air/fuel ratio is achieved, incorporating features like variable valve control and thermal modeling to correct oxygen sensor readings and temperature models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine operates in scavenging mode with overlapping intake and exhaust valves, then engine performance is improved at low engine speeds, but emissions increase due to unaccounted differences in in-cylinder and exhaust gas air/fuel ratios
Solution Approach 1:
The system uses an exhaust oxygen sensor to continuously monitor exhaust gas oxygen concentration and feeds this information back to the controller. The controller adjusts fuel injection quantities based on this feedback to maintain stoichiometric air/fuel ratio in the exhaust gas, thereby controlling emissions while preserving scavenging mode performance benefits
Solution Approach 2:
The controller dynamically changes the in-cylinder air/fuel ratio parameter during scavenging mode operation by adjusting fuel injection quantities. The system modifies this parameter based on real-time exhaust oxygen measurements and thermal model predictions to maintain optimal exhaust gas composition and reduce emissions
2Device complexity
If the exhaust oxygen sensor reading is used directly for fuel control, then the control system is simple, but the air/fuel ratio control accuracy deteriorates due to scavenging effects
Solution Approach 1:
The thermal model acts as an intermediary between the exhaust oxygen sensor and the fuel control system. It processes the sensor readings by accounting for scavenging effects and predicts the actual in-cylinder air/fuel ratio, providing accurate control information without requiring complex direct measurements
Solution Approach 2:
The system replaces direct mechanical measurement of in-cylinder air/fuel ratio with an indirect approach using exhaust oxygen sensing combined with thermal modeling. This substitution maintains control accuracy while avoiding the complexity of direct in-cylinder measurement systems
3Measurement precision
If the thermal model accurately predicts exhaust system temperature, then emissions control is improved, but the model complexity increases
Solution Approach 1:
The thermal model uses the engine's own operating parameters (fuel injection quantities, air charge, exhaust oxygen concentrations) as inputs to predict exhaust system temperature. The model serves the control system by providing temperature predictions that guide fuel adjustment, using data already available from the engine control process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively regulates emissions by accurately controlling the air/fuel ratio and temperature during scavenging, enhancing engine performance and reducing emissions by ensuring stoichiometric conditions are maintained, even in turbocharged engines with higher scavenging ratios.
Implementation Method 1
an exhaust oxygen (02) sensor configured to measure an 02 concentration of exhaust gas generated by and expelled from the engine into an exhaust system
Implementation Method 2
adjusting, by the controller, an exhaust system temperature modeled by a thermal model to obtain a modified exhaust system temperature
Implementation Method 3
An internal combustion engine combusts a mixture of air and fuel within cylinders to generate drive torque at a crankshaft
Data Source
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AI summary
A control system and method utilize an exhaust oxygen (O2) sensor and a controller configured to operate a turbocharged engine in a scavenging mode, and while the operating the engine in the scavenging mode: command a target in-cylinder air/fuel ratio (FA) for achieving a target exhaust gas FA, adjust the measurement of the exhaust O2 sensor based on a scavenging ratio and the target in-cylinder FA to obtain a modified O2 concentration, adjust an exhaust system temperature modeled by a thermal model to obtain a modified exhaust system temperature, and adjust the target in-cylinder FA based on the modified O2 concentration and the modified exhaust system temperature.