EGR Flow Correction via Thermal Modeling
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Solution Overview
Problem
Traditional engine control systems face challenges in accurately estimating exhaust gas recirculation (EGR) mass flow rates due to reliance on expensive and unreliable flow sensors, particularly under transient conditions, which can lead to errors and increased warranty costs.
Innovation Solution
The proposed solution involves using three temperature sensors to measure air, EGR, and mixed gas temperatures, coupled with an engine air system model to compute EGR flow corrections, allowing for estimation of mass flows and intake manifold temperatures, thereby reducing the need for expensive flow sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional flow sensors (Venturi or other flow sensors) are used to estimate EGR mass flow rate, then measurement capability is provided, but cost increases and reliability decreases
Solution Approach 1:
The patent replaces mechanical flow sensors (Venturi tubes, flow meters) with a thermal-based measurement system using temperature sensors and heat transfer modeling. The EGR mass flow rate is estimated by measuring temperature changes of the EGR coolant and applying thermal convection equations, eliminating the need for mechanical flow sensing components.
Solution Approach 2:
The patent introduces EGR coolant temperature as an intermediary measurement parameter. Instead of directly measuring EGR gas flow, the system measures the temperature of the coolant circulating through the EGR cooler and uses this thermal signature to infer the EGR mass flow rate through heat transfer relationships.
2Ease of operation
If open loop tables and PID controllers are used for EGR control, then control strategy is provided, but accuracy under transient conditions deteriorates
Solution Approach 1:
The patent transitions from using fixed lookup tables calibrated for steady-state conditions to a dynamic thermal model that continuously adapts to changing operating conditions. The heat transfer model incorporates real-time temperature measurements and calculates EGR flow based on current thermal states, enabling accurate estimation during transient operations.
Solution Approach 2:
The system implements feedback by continuously measuring EGR coolant temperature and using this information to update the thermal model and correct EGR flow estimates. This closed-loop approach allows the system to compensate for deviations from steady-state conditions and maintain accuracy during transients.
3Measurement precision
If physics-based feed forward calculation is used instead of open loop tables and PID controls, then response under transient conditions improves, but system complexity increases
Solution Approach 1:
The patent replaces complex mechanical flow sensing hardware with a computational thermal model. The complexity is shifted from physical components to software-based heat transfer calculations, which can be implemented in standard engine control units using readily available temperature sensor data.
Solution Approach 2:
The thermal model uses existing EGR coolant temperature measurements already present in the engine management system. By leveraging existing sensor data and standard heat transfer principles, the system achieves improved EGR estimation without requiring additional specialized sensors or complex hardware modifications.
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 accurate and reliable EGR flow corrections, improving engine control under transient conditions and reducing costs by eliminating the need for expensive flow sensors, while enhancing the precision of EGR mass flow rate estimation.
Implementation Method 1
measuring an air temperature of air passing through the air input using a first temperature sensor
Implementation Method 2
measuring an EGR temperature of EGR gases passing through the EGR input using a second temperature sensor
Implementation Method 3
measuring a mixed gas temperature of mixed gases after passing through the mixer using a third temperature sensor
Implementation Method 4
modeling a convection heat transfer rate of the intake manifold
Implementation Method 5
modeling a conduction heat transfer rate of the intake manifold
Data Source
AI summary
An exhaust gas recirculation (EGR) flow correction system and method are disclosed for an engine air system with air and EGR inputs to a mixer. The system includes three temperature sensors to measure temperatures of the air input, EGR input, and mixer output; and an air system model computing EGR flow corrections using the three temperatures. Air system can include intake manifold, charge air cooler (CAC), air throttle, EGR cooler and EGR valve, with first sensor between CAC and air throttle, second sensor between EGR cooler and EGR valve, third sensor in intake manifold. Air system model can estimate mass flows through air and EGR inputs, estimate intake manifold temperature at third sensor, estimate intake manifold temperature error, and compute EGR corrections based on temperature error. Air system model can estimate CAC and EGR cooler outlet temperatures, and mixer input temperature.