Low-Pressure EGR Mass Flow Control Using Oxygen Sensor Compensation
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Solution Overview
Problem
Existing methods for determining the mass flow rate of a low-pressure exhaust gas recirculation (EGR) circuit in internal combustion engines suffer from poor precision and reliability due to interference from hydrocarbons, affecting the accuracy of oxygen measurement by UEGO linear oxygen sensors, especially at rich air/fuel equivalence ratios.
Innovation Solution
A method that uses a combination of UEGO linear oxygen sensors and air flow meters to improve the estimation of the EGR circuit's incidence by compensating for unburned hydrocarbons, employing a compensation factor and psychometric level to enhance oxygen measurement accuracy, thereby improving the reliability of mass flow rate determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UEGO linear oxygen sensor is used to measure oxygen in the intake pipe, then the oxygen measurement is affected by hydrocarbons in rich air/fuel conditions, but the sensor provides a way to determine EGR incidence
Solution Approach 1:
The patent introduces an intermediary calculation approach by using the relationship between oxygen concentration and air/fuel equivalence ratio as a mediating variable. Instead of directly measuring EGR mass flow rate, the system measures oxygen concentration and uses it to determine the air/fuel equivalence ratio, which then serves as an intermediary to calculate EGR incidence. This indirect measurement path avoids the direct interference of hydrocarbons on the measurement accuracy.
Solution Approach 2:
The patent changes the measurement parameter from direct mass flow rate measurement to oxygen concentration measurement. By measuring oxygen concentration in the intake pipe and using it to derive the air/fuel equivalence ratio, the system transforms the measurement approach to one that is less susceptible to hydrocarbon interference. The parameter transformation allows the system to work around the limitation of the UEGO sensor in rich conditions.
2Measurement precision
If a mass flow rate sensor is installed along the bypass pipe, then direct measurement of EGR mass flow rate is achieved, but precision and reliability of the measurement are compromised
Solution Approach 1:
The patent replaces direct EGR mass flow rate measurement with an intermediary measurement approach. Instead of installing a sensor directly in the bypass pipe to measure EGR flow, the system uses a UEGO oxygen sensor in the intake pipe to measure oxygen concentration, which serves as an intermediary parameter. This intermediary measurement is then used to calculate the air/fuel equivalence ratio and subsequently the EGR incidence, providing a more reliable measurement path.
Solution Approach 2:
The patent replaces the mechanical mass flow rate sensor installation with a chemical/computational measurement system. Instead of using a physical sensor in the bypass pipe that suffers from precision and reliability issues, the system substitutes a UEGO oxygen sensor combined with computational algorithms. This substitution transforms a mechanical measurement problem into a chemical sensing and mathematical calculation solution, achieving better measurement quality.
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
The method provides a more precise and reliable estimation of the EGR circuit's incidence, ensuring accurate determination of the mass flow rate and supporting optimal engine combustion strategies.
Implementation Method 1
a sensor (30) arranged along said intake pipe (6) and determining a quantity of oxygen available in said gas mixture
Data Source
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AI summary
A method to determine the mass flow rate of a low-pressure exhaust gas recirculation EGR circuit (EGRLP) of an internal combustion engine (1) comprising a first linear sensor (30) to measure the quantity of oxygen available in the mixture of fresh air taken in and exhaust gases flowing through the intake pipe (6) and a second linear sensor (25) to measure the quantity of oxygen available in the flow of exhaust gases; the method comprises the steps of determining a control current (I) of the first sensor (30) and a control current (I) of the second sensor (25); in case the flow of exhaust gases in rich in fuel, updating the control current (I) of the first sensor (30) as a function of the control current (I) of the second sensor (25); and determining the mass flow rate of a low-pressure exhaust gas recirculation EGR circuit (EGRLP) as a function of the control current (I) of the first sensor (30) and a control current (I).