Fuel Cell System Air Density Control via Liquid Fuel Evaporator
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Solution Overview
Problem
Fuel cell systems using liquid fuels face challenges in maintaining stable air supply and power generation efficiency due to limitations in air flow rate adjustment, which affects the density of reforming gas and reaction efficiency in the reformer and stack.
Innovation Solution
The fuel cell system incorporates a configuration with fuel evaporators that utilize the phase change of liquid fuels to increase air density supplied to the burner and stack, including expansion valves to adjust fuel flow according to operation modes, enhancing heat exchange and gasification efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a blower is used to adjust the flow rate of air supplied to the stack, then the air flow rate can be controlled, but the air flow rate adjustment is limited and stable air supply becomes difficult when power generation amount operation condition is excessive
Solution Approach 1:
The invention changes the temperature parameter of the air supplied to the stack by cooling it with cold liquid fuel. This temperature reduction increases air density, allowing more air to be supplied to the stack without increasing volumetric flow rate, thereby enabling higher power generation while maintaining stable air supply.
Solution Approach 2:
The invention introduces cold liquid fuel as an intermediary substance to transfer heat from the air stream. The liquid fuel absorbs heat from the air, cooling it and increasing its density, thus mediating between the air supply system and the stack to achieve higher power generation with stable supply.
2Productivity
If the flow rate of air supplied to the stack is increased to improve power generation efficiency, then more oxygen is available for electrochemical reaction, but the density of reforming gas and reaction efficiency in the reformer deteriorate
Solution Approach 1:
The invention changes the temperature parameter of both air and reforming gas by cooling them with cold liquid fuel. This simultaneous cooling increases the density of reforming gas while providing sufficient oxygen for electrochemical reaction, resolving the contradiction between power generation efficiency and reforming gas density.
3Productivity
If liquid fuel is directly supplied to a fuel treatment apparatus for reforming, then the reforming process can proceed, but heat supply generated by phase change of liquid fuel is not utilized
Solution Approach 1:
The invention converts the cold temperature of liquid fuel (which would normally be a disadvantage requiring preheating) into a beneficial cooling effect. The cold liquid fuel is used to cool air and reforming gas, increasing their densities and improving reaction efficiencies, thereby transforming the energy that would be lost during phase change into useful cooling.
Solution Approach 2:
The liquid fuel serves dual functions: it undergoes phase change for vaporization while simultaneously providing cooling to the air and reforming gas. The fuel system essentially cools itself and the surrounding streams using its own thermal energy during vaporization, eliminating the need for separate cooling 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 configuration improves the efficiency of reforming reactions and power generation by increasing air and reforming gas density, leading to enhanced combustion and electrochemical reaction efficiency.
Implementation Method 1
a fuel evaporator that makes liquid fuel discharged from the first storage tank exchange heat with air flowing through the first supply pipe or air flowing through the second supply pipe
Implementation Method 2
a fuel evaporator that makes liquid fuel discharged from the first storage tank exchange heat with air flowing through the first supply pipe or air flowing through the second supply pipe
Data Source
AI summary
A fuel cell system may include: a reformer performing a reforming process of producing hydrogen gas from a gasified fuel; a burner supplying heat to the reformer; a stack generating electrical energy by generating an electrochemical reaction using reforming gas and air discharged from the reformer; a first supply pipe supplying external air to the burner; a second supply pipe supplying external air to the stack; a first storage tank storing a liquid fuel; a second storage tank supplying a gasified fuel to the reformer; and a fuel evaporator making a liquid fuel discharged from the first storage tank exchange heat with air flowing through the first supply pipe or air flowing through the second supply pipe, and sending a gasified gaseous fuel to the second storage tank.