Fuel Cell System Recirculation for Cold Start Warm-Up
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Solution Overview
Problem
Fuel cells struggle to quickly warm up in cold environments, leading to reduced power generation efficiency and potential freezing of drain valves, which obstructs the supply of unconsumed fuel gas to the cathode, necessitating additional heating methods and equipment.
Innovation Solution
A fuel cell system that recirculates and reuses exhaust gas by connecting the gas-liquid separator's circulation path to the fuel gas supply path, and uses a drain valve to direct unconsumed fuel gas to the oxygen-containing gas supply path, enabling exothermic reactions to heat the fuel cell and unfreeze the valve, without the need for external heating equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fuel cell is operated in cold environment, then power generation reaction speed decreases, but external heating equipment is not available to warm up the fuel cell quickly
Solution Approach 1:
The system uses its own fuel exhaust gas, which contains unconsumed fuel and is heated by the fuel cell's own power generation reaction, to warm up the fuel cell and unfreeze the drain valve. This self-service approach eliminates the need for external heating equipment while quickly restoring optimal power generation speed.
Solution Approach 2:
The patent converts the previously wasted heat in fuel exhaust gas into a beneficial heating source. By directing this hot exhaust gas through the drain valve and into the fuel cell, the system transforms what was considered waste heat into the key resource for rapid warm-up and valve unfreezing.
2Reliability
If drain valve is frozen, then unconsumed fuel gas cannot be supplied to cathode, but additional heating equipment increases system complexity
Solution Approach 1:
The heated fuel exhaust gas serves dual purposes: it unfreezes the drain valve and supplies unconsumed fuel gas to the cathode. This self-service mechanism restores valve operability without requiring any external heating equipment, maintaining system simplicity while ensuring reliability.
Solution Approach 2:
The patent merges the heating function and fuel supply function into a single integrated process. The same hot exhaust gas flow that unfreezes the valve also provides the fuel gas needed for the exothermic reaction in the cathode, eliminating the need for separate heating equipment.
3Loss of energy
If fuel exhaust gas is discharged without recirculation, then heating efficiency is low, but recirculation system increases device complexity
Solution Approach 1:
The patent converts the waste heat and unconsumed fuel in the exhaust gas into valuable resources. By recirculating this exhaust gas through the fuel cell and drain valve, the system transforms energy loss into the heating source needed for rapid warm-up and valve unfreezing.
Solution Approach 2:
The recirculation system provides multiple functions simultaneously: it heats the fuel cell, unfreezes the drain valve, and supplies fuel gas to the cathode. This multi-functionality justifies the added complexity by eliminating the need for separate heating equipment and maximizing energy utilization.
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 rapid warming of the fuel cell and efficient utilization of fuel gas, reducing the need for additional heating equipment and ensuring the fuel cell operates efficiently even in cold conditions by utilizing the heat from both power generation and exothermic reactions.
Implementation Method 1
an electrochemical reaction (power generation reaction) is caused by supplying the fuel gas to the anode and supplying the oxygen-containing gas to the cathode
Implementation Method 2
Due to the heat of this power generation reaction, the fuel exhaust gas discharged from the anode of the fuel cell to the fuel exhaust gas path is also heated
Implementation Method 3
a gas-liquid separator into which the fuel exhaust gas flows via the fuel exhaust gas flow path, the gas-liquid separator being configured to separate the fuel exhaust gas into a gas and a liquid
Implementation Method 4
by opening the drain valve, the discharge fluid containing the unconsumed portion and the liquid water is discharged from this liquid discharge port to the connecting flow path... this unconsumed portion can be supplied along with the oxygen-containing gas to the cathode. Due to this, the exothermic reaction in the cathode catalyst can be caused
Implementation Method 5
a circulation flow path configured to cause a gas discharge port of the gas-liquid separator and the fuel gas supply flow path to be in communication with each other
Data Source
AI summary
A fuel cell system includes a gas-liquid separator, a circulation flow path, a connecting flow path, and a distribution flow path. The gas-liquid separator separates fuel exhaust gas, which flows therein via a fuel exhaust gas flow path, into gas and liquid. The circulation flow path causes a gas discharge port of the gas-liquid separator and the fuel gas supply flow path to communicate with each other. The connecting flow path causes a liquid discharge port of the gas-liquid separator to communicate with the oxygen-containing gas supply flow path, via a drain valve. The distribution flow path causes the circulation flow path or a portion of the fuel gas supply flow path that is on a downstream side of a connecting section connecting to the circulation flow path to communicate with a downstream side of the drain valve of the connecting flow path via an opening and closing valve.