Exhaust Outlet Pressure Determination via Flow Model
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Solution Overview
Problem
Existing methods for determining pressure in the outlet of an exhaust system of an internal combustion engine, particularly in flow loss-optimized systems with low-pressure exhaust gas recirculation, face challenges in accuracy and robustness due to sensitivity to pressure changes and the need for precise sensors with high accuracy, which is difficult to achieve in the harsh environment of the exhaust system.
Innovation Solution
A method that records the mass flow through the internal combustion engine system and ambient pressure, using a flow model to determine the throttling and position of the low-pressure exhaust gas recirculation valve, allowing for the calculation of the pressure at the outlet of the exhaust system without the need for a pressure sensor, by utilizing existing components like hot-film air mass meters and valve settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pressure sensor is used to measure pressure at the exhaust system outlet, then measurement accuracy can be improved, but the device complexity and cost increase, and the sensor reliability decreases due to the harsh exhaust environment
Solution Approach 1:
The patent extracts the pressure measurement function from the exhaust system environment by using a pressure sensor in the fresh air supply line instead of directly in the exhaust outlet. This removes the sensor from the harsh exhaust environment while still enabling accurate pressure determination through the flow model calculation.
Solution Approach 2:
The patent introduces a flow model as an intermediary between the measurable parameters (mass flow, ambient pressure) and the desired pressure information. This mathematical model acts as a mediator that calculates exhaust outlet pressure without requiring direct sensing in that location, thus avoiding the technical contradictions.
2Measurement precision
If a pressure sensor with high accuracy (less than 1 hPa) is used, then measurement precision is improved, but the device complexity and difficulty of detection increase due to the harsh exhaust system environment
Solution Approach 1:
The measurement function is extracted from the difficult-to-access exhaust outlet environment and relocated to the fresh air supply line where sensing is easier. The pressure sensor is installed in a accessible location while the flow model bridges the gap to provide exhaust outlet pressure information.
Solution Approach 2:
The patent replaces the direct mechanical pressure sensing approach in the exhaust system with a computational approach using a flow model. Instead of mechanically placing a sensor in the harsh exhaust environment, the system uses mathematical calculations based on easily measurable parameters to determine the desired pressure information.
3Loss of energy
If flow loss-optimized low-pressure exhaust gas recirculation is implemented, then system efficiency is improved, but the system becomes more sensitive to pressure changes, reducing reliability
Solution Approach 1:
The patent implements feedback by continuously determining the exhaust outlet pressure using the flow model and using this information to adapt the low-pressure EGR system. This closed-loop approach allows the system to compensate for pressure changes and maintain reliable operation even in flow loss-optimized configurations that are inherently more sensitive to pressure variations.
Solution Approach 2:
The patent dynamically adjusts system parameters based on the determined exhaust outlet pressure. By changing operational parameters according to actual pressure conditions, the system maintains optimal performance and reliability across varying operating conditions, preventing the sensitivity issues that arise in flow loss-optimized systems.
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 enables accurate determination of the pressure in the exhaust system outlet, reducing errors and improving system robustness, allowing for precise adaptation of exhaust gas pressure and control of the internal combustion engine system.
Implementation Method 1
with an air supply amount detecting device (14) for detecting a mass flow through the fresh air supply (8)
Data Source
Figure 1
AI summary
The method involves detecting a mass flow through a combustion engine system (1), and sensing an ambient pressure at a fresh air supply (8) of the combustion engine system. The pressure at the outlet of the exhaust system (6) is determined corresponding to the mass flow, the ambient pressure and a throttling of the mass flow through the combustion engine system. An independent claim is also included for a combustion engine system for a vehicle, which comprises a detection unit for detecting a mass flow through the combustion engine system.