Fuel Cell Anode Purging Control via Pressure Change Analysis
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fuel cell systems face challenges in accurately estimating the amount of off-gas discharged from the anode system, leading to unanticipated voltage drops due to hydrogen leakage and pressure changes, which affect hydrogen concentration and system performance.
Innovation Solution
A fuel cell system with a pressure detecting unit and a supply valve control unit that estimates the purging amount based on pressure changes inside the anode system during specific valve states, excluding the influence of hydrogen leakage, to maintain optimal hydrogen concentration and prevent voltage drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gas amount discharged from the anode system is computed based on pressure change inside the anode system, then the purging amount can be estimated, but the computation includes hydrogen leakage which causes unanticipated voltage drops
Solution Approach 1:
The patent segments the gas discharge process into two distinct components: (1) gas discharged through the purge valve (purge gas) and (2) hydrogen leaking through the electrolytic membrane. By separating these components, the system can accurately estimate the purging amount without the confounding influence of hydrogen leakage, thereby resolving the contradiction between measurement precision and voltage stability.
Solution Approach 2:
The patent extracts the hydrogen leakage component from the total gas discharge computation. By calculating the hydrogen transmission amount separately (based on current density and membrane properties) and subtracting it from the total pressure-based gas discharge amount, the system isolates the true purging amount, eliminating the source of unanticipated voltage drops.
2Reliability
If the purge valve is opened to discharge off-gas and increase hydrogen concentration, then voltage drop is prevented, but the purging amount becomes difficult to control accurately due to unaccounted hydrogen leakage
Solution Approach 1:
The patent implements a feedback control mechanism where the purging amount is continuously adjusted based on the difference between the target hydrogen concentration and the actual hydrogen concentration in the anode system. By using the accurately calculated purging amount (that excludes hydrogen leakage) as feedback input, the system can precisely control the purge valve operation to maintain stable hydrogen concentration and prevent voltage drops.
Solution Approach 2:
The patent replaces the traditional mechanical pressure-based purging control with a computational control system that uses electrical measurements (current density) and membrane properties to calculate hydrogen leakage. This substitution enables more precise control of the purging amount by eliminating the uncertainty introduced by mechanical pressure changes alone.
3Measurement precision
If the hydrogen supply valve is closed to stop hydrogen supply, then pressure change measurement is simplified, but hydrogen concentration decreases due to continued hydrogen transmission to cathode
Solution Approach 1:
The patent applies preliminary action by calculating the expected hydrogen transmission amount during the measurement period before actually performing the purging operation. By pre-computing the hydrogen leakage based on current density and membrane characteristics, the system can compensate for the hydrogen concentration decrease that occurs during the closed-valve measurement period, thereby maintaining accurate purging amount estimation without sacrificing hydrogen concentration.
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 solution allows for precise control of the purging process, ensuring stable hydrogen concentration and preventing voltage drops by accurately estimating the purging amount and managing pressure changes, thereby enhancing the system's operational efficiency and reliability.
Implementation Method 1
hydrogen transmitting from the anode of the fuel cell to the cathode through the electrolytic membrane
Implementation Method 2
a pressure detecting unit configured to estimate or measures a pressure inside the anode system
Data Source
AI summary
In order to improve estimation accuracy of a purging amount, a fuel cell system comprises a supply valve that controls a supply of an anode gas into an anode system, a purge valve that discharges an off-gas from the anode system, a pressure detecting unit configured to estimate or measures a pressure inside the anode system, and a purging amount estimating unit configured to estimate a purging amount of the off-gas discharged from the anode system through the purge valve based on a pressure change inside the anode system during a purge valve close duration in a supply valve open state and a pressure change inside the anode system during a purge valve close duration in a supply valve close state.