Fuel Cell Pre-Stop Control to Prevent Cathode Oxidation

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Solution Overview

Problem

In fuel cell systems, air permeation through the electrolyte membrane after system stop can cause oxidation of cathode component materials, despite hydrogen filling, due to partial pressure differences and external air introduction.

Innovation Solution

A fuel cell system with a controller that controls gas supply mechanisms to reduce partial pressure differences between the anode and cathode, delivering fuel gas to the cathode during the pre-stop process, and stopping it when the pressure difference reaches a preset reference value, thereby preventing air introduction and oxidation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hydrogen is filled into the cathode during system stopping process, then oxidation of cathode component material is prevented, but air may still be introduced from outside the fuel cell into the cathode due to partial pressure difference, causing oxidation over time

Engineering Contradiction:

Improveprotection of cathode component materialVSAvoidair introduction and oxidation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary action by delivering fuel gas to the cathode in a pre-stop process before the system is fully stopped. This pre-positioning of fuel gas in the cathode creates a protective atmosphere that prevents air infiltration and oxidation when the system stops, addressing the timing issue where post-stop hydrogen filling is insufficient.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of partial pressure difference by controlling the delivery of fuel gas to the cathode until the partial pressure difference between anode and cathode with respect to fuel gas is reduced to or below a preset reference value. This parameter control prevents air introduction while maintaining fuel gas protection.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If fuel gas is continuously delivered to the cathode to maintain pressure balance, then air introduction is prevented, but gas waste increases and system complexity increases

Engineering Contradiction:

Improveair infiltration preventionVSAvoidfuel gas consumption

Core Design Contradiction:

Object-affected harmful factorsVSLoss of substance

Solution Approach 1:

The patent implements feedback control by monitoring the partial pressure difference of fuel gas between anode and cathode and adjusting the fuel gas delivery accordingly. The delivery continues only until the partial pressure difference is reduced to or below a preset reference value, then stops. This feedback mechanism prevents excessive fuel gas consumption while maintaining effective protection against air infiltration.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent applies partial action by delivering fuel gas only to the extent necessary to achieve the preset reference value for partial pressure difference, rather than continuous excessive delivery. This partial delivery is sufficient to prevent air introduction while minimizing fuel gas waste.

Inventive Principle:

Principle #16Partial or excessive action

3Duration of action of moving object

If the system stops immediately without pre-stop process, then operation time is reduced, but cathode component material oxidation occurs due to air introduction

Engineering Contradiction:

Improvesystem stop timeVSAvoidcathode material stability

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by implementing a pre-stop process that delivers fuel gas to the cathode before the system is fully stopped. This preliminary fuel gas delivery prepares the cathode with a protective atmosphere, ensuring material stability during the stop period without requiring extended stop time.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses fuel gas as an intermediary substance between the cathode and external air during the pre-stop process. This intermediary fuel gas creates a pressure balance and protective atmosphere that prevents direct contact between air and cathode component materials, ensuring reliability during the transition to system stop.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 effectively inhibits oxidation of cathode component materials by maintaining a stable pressure environment, reducing the risk of air infiltration and material degradation after system stop.

Implementation Method 1

part of the introduced air may permeate through the electrolyte membrane to reach the anode

Methodology Applied

Scientific EffectPermeation: Permeation

Implementation Method 2

a partial pressure difference between the anode and the cathode with respect to at least the fuel gas of remaining gases in the anode and in the cathode

Methodology Applied

Scientific EffectPartial pressure difference: Pressure Gradient

Data Source

PatentUS8932772B2Fuel cell system and method of stopping fuel cell system

Publication Date: 2015.01.13 TOYOTA JIDOSHA KK

AI summary

In a fuel cell system, a controller is programmed to control a first gas supply mechanism to deliver a first gas containing a fuel gas to a cathode in a pre-stop process performed at a system stop of the fuel cell system. The controller is programmed to control the first gas supply mechanism to stop the delivery of the first gas in a first state where a partial pressure difference between an anode and the cathode with respect to at least the fuel gas of remaining gases in the anode and in the cathode is reduced to or below a preset reference value.