Fuel Cell Flow Rate Sensor Abnormality Detection
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Solution Overview
Problem
Existing fuel cell systems face errors in determining the abnormality of a flow rate sensor, particularly in the low rotation range of the compressor, due to large errors in pressure measurement values.
Innovation Solution
A fuel cell system design that calculates the flow rate of oxygen-containing gas without using a pressure measurement value, utilizing a bypass channel and adjustable valves to determine the normal functioning of the flow rate measurement unit by comparing calculated and measured values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a pressure measurement value is used to determine flow rate sensor abnormality, then the determination method is simple, but large errors occur in low rotation range of the compressor
Solution Approach 1:
The patent introduces a bypass channel with a bypass valve as an intermediary element to create an alternative flow path. By controlling the bypass valve opening degree, the system can regulate the flow rate through the fuel cell stack independently of the compressor's pressure ratio characteristics, enabling accurate flow rate measurement and abnormality determination even in low rotation ranges where traditional pressure-based methods fail
Solution Approach 2:
The patent changes the control parameter from pressure ratio (which has low sensitivity in low rotation range) to bypass valve opening degree. The bypass valve opening degree serves as a new control parameter that has a more direct and predictable relationship with flow rate, allowing for more precise flow rate determination and sensor abnormality detection across the entire compressor rotation range
2Device complexity
If pressure sensor is used to measure flow rate, then the measurement system is simple, but reliability is reduced in low rotation range
Solution Approach 1:
The bypass channel with adjustable bypass valve acts as an intermediary system that provides a reliable alternative method for flow rate determination. This intermediary path allows the system to bypass the unreliable pressure-based measurement in low rotation ranges and use valve opening degree-based calculation instead, significantly improving measurement reliability without adding complex sensor systems
Solution Approach 2:
The patent replaces the mechanical pressure-based measurement system with a control-based measurement approach using the bypass valve opening degree. Instead of relying on mechanical pressure sensors that fail in low rotation ranges, the system uses the electronically controllable bypass valve opening degree as the primary measurement parameter, substituting a more reliable mechanical control element for the unreliable sensing element
Data Source
AI summary
The fuel cell system includes a control unit that calculates the flow rate of the oxygen-containing gas flowing through the supply passage based on the opening degree of the bypass valve, the opening degree of the stop valve, and the state of the oxygen-containing gas supply in the oxygen-containing gas supply unit, and determines that the measurement value of the flow rate measurement unit is not normal when the difference between the calculation value and the measurement value by the flow rate measurement unit is equal to or larger than a predetermined amount.