Fuel Cell Air Supply Ejector Recirculation for Surge Avoidance
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Solution Overview
Problem
Fuel cell systems using turbo type compressors face instability due to a surge phenomenon at high pressure and low flow conditions, which affects the overall efficiency and performance of the air supply apparatus.
Innovation Solution
The air supply apparatus recirculates high-pressure air from the outlet back to the inlet of the compressor, using an ejector to mix it with external air and increase pressure, thereby avoiding surge conditions and optimizing air supply to the fuel cell stack.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If a turbo type compressor is used to supply high-pressure air to the fuel cell stack, then the air supply pressure is improved, but the compressor enters surge region at high pressure and low flow conditions causing system instability
Solution Approach 1:
An ejector is introduced as an intermediary device between the compressor outlet and the fuel cell stack. The ejector uses high-pressure air from the compressor to create a vacuum that draws in additional atmospheric air, mixing it with the compressed air. This intermediary mechanism allows the compressor to operate at higher pressures without directly supplying low-flow air to the stack, preventing surge conditions while maintaining high pressure supply capability.
Solution Approach 2:
The system changes the flow parameters by introducing atmospheric air through the ejector to increase the total air flow rate. This parameter change allows the compressor to operate at higher pressure ratios without entering the surge region, as the combined flow from the ejector and compressor maintains operation outside the unstable surge boundary.
2Stress or pressure
If the compressor operates at high pressure and low flow to meet fuel cell requirements, then the air supply pressure is improved, but excessive power consumption occurs
Solution Approach 1:
The ejector serves as a power-saving intermediary by utilizing the kinetic energy already present in the high-pressure air from the compressor. Instead of requiring the compressor to work harder to deliver the same mass flow, the ejector freezes atmospheric air using the vacuum effect created by the high-velocity compressed air, thereby reducing the total power consumption while maintaining high pressure supply.
Solution Approach 2:
The system replaces part of the mechanical compression work with a vacuum-induced air intake mechanism. The ejector converts the kinetic energy of compressed air into a vacuum field that passively draws in atmospheric air, substituting for additional mechanical compression that would otherwise be required to achieve the same mass flow rate.
3Reliability
If a bypass valve is used to discharge excessive air to avoid surge, then the surge phenomenon is prevented, but system efficiency decreases due to air loss
Solution Approach 1:
Instead of treating the high-pressure air from the compressor as waste that needs to be discharged through a bypass valve, the system converts this high-pressure air into a useful resource. The ejector uses the high-pressure air to create a vacuum that draws in and compresses atmospheric air, transforming what would have been wasted energy into additional compressed air supply for the fuel cell stack.
Solution Approach 2:
The system recovers the energy in the high-pressure air that would otherwise be discarded through the bypass valve. By routing this air through the ejector, the system recovers its pressure energy to drive the vacuum effect, thereby recovering what would have been wasted energy and converting it into useful compressed air flow.
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 maintains high air pressure and low flow rates required by the fuel cell system, reducing compressor power consumption and improving system efficiency while preventing surge phenomena.
Implementation Method 1
an ejector that mixes bypass air and external air to increase a pressure of air and then supplying mixed air to the inlet of the compressor
Data Source
AI summary
An air supply apparatus and method for a fuel cell, which supplies high-pressure air while avoiding a surge phenomenon of a turbo type compressor in a fuel cell system to which the turbo type compressor is applied is provided. In particular, a portion of air from an outlet of a compressor to an inlet of the compressor is recirculated to the supply of air supplied from the compressor to a stack. This recirculated air and external air introduced from the outside are mixed and supplied to the inlet of the compressor at a sufficiently high air pressure, allowing the compressor to avoid a surge region and enabling the supply of air with a high pressure and a low flow rate.