NOx Sensor-Based PM Estimation for Exhaust Gas Accuracy
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Solution Overview
Problem
Existing internal combustion engines face challenges in accurately estimating PM content in exhaust gas at the upstream side of a collection device due to high deposition rates and frequent PM sensor failures, leading to inaccurate diagnosis of collection device breakage and inefficient regeneration control.
Innovation Solution
An internal combustion engine utilizing a NOx sensor on the upstream side of the collection device, which detects NOx content and emission amounts, estimates PM content with high accuracy by referencing a trade-off relation between NOx and PM emission amounts, avoiding the need for additional PM sensors and reducing deposition-related errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a PM sensor is arranged on the upstream side of the collection device to detect PM content, then the PM content can be detected, but the sensor experiences high deposition rates and frequent failures
Solution Approach 1:
The patent uses NOx as an intermediary substance to indirectly estimate PM content. Instead of directly measuring PM with a sensor that fails due to deposition, the system measures NOx concentration and uses the established trade-off relationship between NOx and PM emission amounts to calculate PM content. This mediator approach allows accurate PM estimation without exposing a sensor to high PM deposition environments.
Solution Approach 2:
The patent replaces the direct mechanical/physical PM sensing mechanism with a chemical measurement approach. By measuring NOx concentration (a gaseous component) and using computational estimation based on emission trade-off relationships, the system substitutes the fragile direct PM detection mechanism with a more reliable indirect measurement system that avoids sensor deposition issues.
2Reliability
If a PM sensor is arranged on the downstream side of the collection device, then the sensor reliability is improved, but the PM content estimation accuracy deteriorates due to variations in inflow amount
Solution Approach 1:
The patent introduces NOx measurement as an intermediary that allows estimation of upstream PM content without being affected by collection device performance variations. The NOx measurement serves as a reference that, when combined with the trade-off relationship, enables accurate PM estimation while using the downstream PM sensor only for reliability purposes.
Solution Approach 2:
The system uses feedback from NOx sensor measurements and the known trade-off relationship between NOx and PM emissions to continuously estimate and correct PM content values. This feedback mechanism allows the system to maintain accurate PM estimation despite variations in inflow amount or collection device performance, as the NOx-based estimation provides a reference that compensates for these variations.
3Measurement precision
If additional PM sensors are added to improve PM content estimation accuracy, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent makes the NOx sensor serve multiple functions: it detects NOx concentration for emission monitoring and simultaneously serves as a reference for estimating PM content through the trade-off relationship. This multi-functionality allows the system to achieve accurate PM estimation without adding dedicated PM sensors, thereby avoiding increased device complexity while maintaining measurement precision.
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 allows for stable and accurate estimation of PM content upstream of the collection device, enabling precise diagnosis of collection device breakage and timely regeneration control, thereby improving engine efficiency and reducing the risk of PM release into the atmosphere.
Implementation Method 1
a NOx sensor 31 which detects a NOx content in the exhaust gas
Implementation Method 2
PM (particulate matter) contained in an exhaust gas is collected by a collection device arranged in an exhaust pipe
Implementation Method 3
a PM sensor is arranged in the exhaust pipe on the downstream side of the collection device
Implementation Method 4
a regeneration control is performed which combustion-removes the PM deposited in the collection device by raising a temperature of the exhaust gas passing through the collection device
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
An engine (10) is provided with an estimating device (40) which estimates a PM content (qUP_PM) in an exhaust gas at an upstream side of a collection device (26) from a detection value (NOx content: qUP_NOx) of an NOx sensor (31) based on a trade-off relation between an NOx emission amount (qOUT_NOx) and a PM emission amount (qOUT_PM) from a cylinder (13), and thus the PM content (qUP_PM) in the exhaust gas at the upstream side of the collection device (26) arranged in an exhaust pipe (23) can be estimated in a high accuracy manner with a simple configuration.