Fuel Cell Stack Coolant Control with Pressure-Drop Pump Feedback
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Solution Overview
Problem
Current fuel cell propulsion systems face challenges in efficiently controlling coolant flow rate due to sluggish temperature-gradient based feedback, which leads to delays and noise during transient vehicle states, and requires a more responsive and accurate method to maintain optimal fuel cell stack temperature and pressure.
Innovation Solution
A computer-controlled system that uses both temperature and pressure sensors to generate feedback corrections, allowing the pump to operate at a target speed based on real-time delta temperature and pressure drop calculations, incorporating high-pass and low-pass filters for signal blending and PI control structures to ensure precise coolant flow management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If temperature-gradient based feedback is used to control coolant flow rate, then the system can maintain thermal equilibrium, but the response becomes sluggish during transient states due to delays in coolant transport and temperature sensor measurements
Solution Approach 1:
The system uses pressure drop measurements across the fuel cell stack to predict and preemptively adjust coolant flow rate before temperature changes occur. By measuring pressure differential between inlet and outlet of the stack, the control system can immediately respond to changes in coolant flow conditions without waiting for temperature sensors to detect the change, thus eliminating the inherent delay in temperature-based feedback systems.
2Measurement precision
If multiple temperature sensors are used to measure temperature gradient across the fuel cell stack, then temperature control feedback can be obtained, but noise and calibration complexities increase during transient states due to phase lag associated with warm coolant having residual heat
Solution Approach 1:
The invention extracts the essential information needed for flow rate control from the complex temperature gradient measurements by using pressure drop measurements instead. This eliminates the need for multiple temperature sensors and their associated calibration complexities, while still providing accurate feedback for coolant flow rate control. The pressure drop measurement directly reflects the actual coolant flow through the stack without the confounding effects of residual heat and phase lags.
3Reliability
If a proportional-integral feedback controller is used to control coolant flow rate, then thermal sensitivity can be managed, but the system requires pressure sensors and complex signal processing including high-pass and low-pass filters
Solution Approach 1:
The system implements a feedback control mechanism that uses pressure drop measurements across the fuel cell stack to continuously monitor and adjust coolant flow rate. The pressure differential signal is processed through high-pass and low-pass filters to extract the relevant flow rate information while eliminating noise and transient effects. This filtered pressure-based feedback signal then drives the pump control to maintain optimal coolant flow, providing reliable thermal sensitivity control with a simplified sensor requirement compared to temperature-based 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 approach provides a fast and reliable response to transient states, reduces noise and calibration complexities, and ensures precise pump control, enhancing the robustness and efficiency of coolant flow management in fuel cell propulsion systems.
Implementation Method 1
at least one pressure sensor for generating a pressure signal associated with a pressure drop of the coolant across the fuel cell stack
Implementation Method 2
at least one temperature sensor for generating a temperature signal associated with a temperature of the coolant
Implementation Method 3
a pump for pumping the coolant through the coolant passage to remove the waste heat from the fuel cell stack
Implementation Method 4
the coolant collects the stack waste heat. The coolant is directed through a pipe or hose from the stack to the radiator where it is cooled
Implementation Method 5
the radiator is relatively large. The physical size of the radiator and the power of the fan have to be higher than those of an internal combustion engine having a similar power rating because of the lower operating temperature of the fuel cell system
Implementation Method 6
the coolant is directed through a pipe or hose from the stack to the radiator where it is cooled by ambient air either forced through the radiator from movement of the vehicle or by operation of the fan
Data Source
AI summary
A computer is provided for a fuel cell propulsion system of a motor vehicle. The computer includes one or more processors receiving a temperature signal from one or more temperature sensors and a pressure signal from one or more pressure sensors. The computer further includes a non-transitory computer readable storage medium including instructions, such that the processor is programmed to determine a feedback correction based on the temperature of the coolant and the pressure drop of the coolant across the fuel cell stack. The processor is further programmed to generate a pump command signal based on the feedback correction and a nominal pump command, with the pump command signal actuating a pump to pump coolant at a target pump speed.