NOx Prediction Method Using Intake O2 Correction
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Solution Overview
Problem
Conventional methods for predicting NOx amounts in exhaust gases are inaccurate, especially during transient engine conditions, and rely on maps or NOx sensors that operate only at specific temperatures, leading to significant errors.
Innovation Solution
A method that detects the O2 amount in intake air and corrects the predicted NOx amount based on engine driving conditions, using a correlation exponent and environmental factors to improve prediction accuracy, and an exhaust system that controls reducing agent supply or combustion atmosphere accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a map based on steady-state engine conditions is used to predict NOx amount, then the prediction can be obtained from stored data, but the prediction accuracy deteriorates significantly during transient engine conditions
Solution Approach 1:
The patent applies dynamics by transitioning from a static map-based prediction system to a dynamic prediction system that continuously adjusts NOx predictions based on real-time transient engine conditions. The system incorporates transient correction factors and real-time sensor data (O2, temperature, pressure) to dynamically update NOx amounts during transient operations, resolving the contradiction between obtaining predictions from stored data and maintaining accuracy during changing conditions.
Solution Approach 2:
The patent implements feedback by using real-time sensor measurements (O2 sensor, temperature sensors, pressure sensors) to continuously monitor actual exhaust conditions and compare them with predicted values. The system adjusts NOx predictions based on this feedback loop, incorporating correction factors derived from actual sensor readings during transient conditions, thereby maintaining prediction accuracy despite changing engine operations.
2Measurement precision
If a NOx sensor is used to detect NOx amount in real-time, then the prediction can be updated continuously, but the sensor operates normally only when exhaust gas temperature exceeds a predetermined temperature, causing detection errors during warm-up
Solution Approach 1:
The patent applies preliminary action by establishing alternative NOx prediction methods before the exhaust system reaches operating temperature. During warm-up phases when the NOx sensor is not yet functional, the system uses pre-calculated map data combined with transient correction factors and environmental parameter adjustments to predict NOx amounts. This ensures continuous NOx estimation capability from cold start through warm-up without relying solely on the temperature-dependent sensor.
Solution Approach 2:
The patent uses an intermediary approach by introducing multiple intermediate prediction models that bridge the gap between cold-start conditions and full sensor operation. The system employs environmental parameter-based corrections (temperature, pressure, humidity adjustments) and transient correction factors as intermediary calculation layers that enable accurate NOx estimation even when the primary NOx sensor is not yet operational, ensuring reliable detection continuity during warm-up.
3Reliability
If reducing agent supply is increased to improve NOx purification, then the purification efficiency improves, but fuel economy deteriorates due to additional fuel consumption
Solution Approach 1:
The patent applies partial action by precisely controlling reducing agent injection based on actual predicted NOx amounts rather than using excessive or fixed injection rates. The system calculates optimal reducing agent quantities by multiplying predicted NOx values with stoichiometric ratios and correction factors, injecting only the necessary amount to achieve effective NOx reduction. This prevents both under-dosing (reducing purification efficiency) and over-dosing (wasting fuel), optimizing the balance between NOx removal and fuel economy.
4Measurement precision
If additional sensors are installed to improve NOx prediction accuracy, then the prediction precision improves, but the device complexity and product cost increase
Solution Approach 1:
The patent applies universality by making existing sensors (O2 sensor, temperature sensors, pressure sensors) serve multiple functions: they not only monitor exhaust conditions for emission control but also provide data for NOx prediction calculations, transient correction factors, and environmental parameter adjustments. The O2 sensor, for example, is used both for lambda control and for predicting NOx amounts through correlation calculations, eliminating the need for separate NOx sensors while maintaining prediction accuracy.
Solution Approach 2:
The patent implements self-service by enabling the existing sensor network to autonomously perform NOx prediction calculations using their own measurements combined with stored map data and environmental parameters. The O2 sensor, temperature sensors, and pressure sensors automatically provide the data needed for NOx estimation without requiring additional dedicated NOx sensors, allowing the system to serve its own prediction needs using existing infrastructure.
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 method provides precise NOx prediction, enhancing purification efficiency and fuel economy by accurately determining NOx amounts and adjusting reducing agent supply, while reducing the need for additional sensors and lowering product costs.
Implementation Method 1
the nitrogen oxide contained in the exhaust gas is reduced in the DE-NOx catalyst through oxidation-reduction reaction with the reducing agents
Implementation Method 2
The LNT catalyst absorbs the nitrogen oxide contained in the exhaust gas when the engine operates in a lean atmosphere
Implementation Method 3
In the SCR catalyst, the reducing agents such as carbon monoxide and total hydrocarbon (THC) react better with nitrogen oxide than oxygen
Data Source
AI summary
A method for predicting a NOx amount may include detecting an O2 amount in an intake air, calculating a reference O2 amount in the intake air according to a driving condition of an engine, calculating a reference NOx amount contained in an exhaust gas according to the driving condition of the engine, and primarily correcting the reference NOx amount based on the detected O2 amount in the intake air and the reference O2 amount in the intake air according to the driving condition of the engine.