Virtual Temperature Sensing for Fast Exhaust Heater Control
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Solution Overview
Problem
In fluid flow applications like vehicle exhaust systems, existing temperature sensors face challenges due to harsh conditions such as vibration and thermal cycling, leading to delayed stability and potential damage, and external sensors introduce delays and component failure modes, resulting in lower watt density heaters with increased size and cost.
Innovation Solution
A method and system for predicting temperatures along a fluid flow path using predefined models and inputs like mass flow rate and inlet temperature, eliminating the need for physical sensors by calculating sheath and outlet temperatures through equations that account for convective heat transfer and radiation effects, allowing for proactive control of heaters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If physical sensors are used to measure temperature in exhaust systems, then temperature measurement is achieved, but the sensors are damaged by vibration and thermal cycling, leading to delayed stability and potential failure
Solution Approach 1:
The patent creates a virtual copy of the temperature sensor functionality through mathematical modeling. Instead of using a physical sensor that measures temperature directly, the system calculates temperature by copying the thermal behavior equations and solving them with measured inputs (power, mass flow rate, inlet temperature) to obtain the same information without physical contact in the harsh environment
Solution Approach 2:
The patent replaces the mechanical/physical sensor system with a computational/mathematical system. The physical sensor that would be damaged by vibration and heat is substituted with equations and algorithms that calculate temperature based on other measurable parameters, eliminating the fragile mechanical component
2Measurement precision
If external sensors are used for temperature control, then temperature monitoring is achieved, but inherent delays from thermal resistances between sensor wires and outputs reduce response speed
Solution Approach 1:
The virtual sensor model copies the thermal dynamics equations to calculate temperature instantly from measured inputs, eliminating the physical thermal resistance delays that exist in real sensors where heat must conduct through wires and mounting structures
Solution Approach 2:
The system performs preliminary calculation of temperature based on measured parameters before control actions are needed. By continuously solving the thermal equations with real-time inputs (power, mass flow, inlet temperature), the system has temperature information ready immediately for control decisions
3Reliability
If safety margins are applied in heater design due to sensor uncertainty, then reliability is improved, but heater size and cost increase
Solution Approach 1:
The virtual sensor provides a precise mathematical copy of temperature behavior without the uncertainty and delay of physical sensors. This accurate real-time temperature information eliminates the need for conservative safety margins, allowing heaters to be sized more efficiently
Solution Approach 2:
The system changes the parameter of temperature measurement from uncertain physical sensor readings to precise calculated values based on fundamental thermal equations. This parameter transformation removes the uncertainty that necessitates safety margins in heater design
4Loss of information
If physical sensors are installed in exhaust systems, then temperature data is obtained, but component failure modes increase and mechanical mount limitations are imposed
Solution Approach 1:
The patent extracts the temperature measurement function from the physical sensor and relocates it to a computational domain. By taking out the sensing function from the harsh physical environment and implementing it through mathematical equations, the system eliminates the mechanical mounting structure and associated failure modes
Solution Approach 2:
The system creates a virtual copy of the sensor that operates in the computational domain rather than the physical domain. This copy provides temperature information without requiring physical installation in the exhaust system, eliminating mechanical failure modes
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 enables quicker response times, improved accuracy, and higher temperature operations, reducing safety margins and heater size, while removing the need for physical sensors, thus enhancing performance and reliability.
Implementation Method 1
calculating temperatures along a fluid flow path... account for convective heat transfer
Implementation Method 2
account for convective heat transfer and radiation effects
Data Source
AI summary
Methods and systems for predicting at least one temperature along a fluid flow path of a fluid flow system having a heater disposed in the fluid flow path are provided. In one example, a method includes: obtaining at least one input, wherein the at least one input includes a setpoint, a mass flow rate, an inlet temperature, or a combination thereof; calculating a temperature associated with the heater based on a predefined model and the at least one input; and setting a value of the at least one temperature along the fluid flow path to the temperature of the heater.