Fuel Cell Jet Pump Pulsed Recirculation Control
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Solution Overview
Problem
Existing fuel cell systems face challenges in efficiently recirculating fuel at low loads without venting excess fuel, as conventional pumps and jet pumps are costly, complex, and inefficient, particularly in removing water droplets from the anode side during idle conditions.
Innovation Solution
A fuel cell system with a control unit that manages a pulsed fuel supply via a jet pump, using a valve to regulate the anode-cathode pressure differential, ensuring adequate fuel recirculation and water removal by adjusting the fuel supply based on operational parameters, with a bypass line to a pressure regulator for higher loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pump or blower is used to recirculate fuel, then fuel recirculation can be achieved, but the parasitic load on the fuel cell increases and the system becomes more complex and expensive
Solution Approach 1:
The patent replaces conventional mechanical pumps or blowers with a vacuum ejector (jet pump) that uses fluid dynamics principles. The ejector uses a high-pressure motive fluid (fuel) to create a vacuum that draws recirculated fuel through the anode, eliminating the need for mechanical moving parts and reducing system complexity while maintaining recirculation functionality
Solution Approach 2:
The invention employs pneumatic principles by using a vacuum ejector that operates on the principle of fluid injection. The ejector uses a high-pressure fuel stream to create a low-pressure zone that entrains and recirculates fuel through the anode flow fields, utilizing gas dynamics rather than mechanical pumping
2Productivity
If a vacuum ejector is sized for maximum-load flow rates, then adequate fuel supply is ensured at high loads, but the nozzle is too large to recirculate fuel effectively at low loads
Solution Approach 1:
The patent divides the ejector system into multiple nozzles with different flow capacities. Specifically, it uses a large-diameter nozzle for high-flow conditions and a small-diameter nozzle for low-flow conditions, allowing the system to adapt to different load requirements by selecting the appropriate nozzle configuration
Solution Approach 2:
The invention makes the ejector system dynamically adaptable by providing multiple nozzle configurations that can be selected based on operating conditions. The system transitions between different nozzle setups depending on whether high or low fuel flow rates are required, enabling effective operation across the full load range
3Object-generated harmful factors
If excess fuel is vented to expel water droplets from the anode channels, then water removal is achieved, but fuel waste occurs
Solution Approach 1:
The patent implements a self-service mechanism where recirculated fuel serves dual purposes: it maintains cathode humidity through water carryover and simultaneously flushes water droplets from the anode flow fields. The system uses the recirculated fuel itself to clean the anode channels, eliminating the need for separate water removal mechanisms and preventing fuel waste
Solution Approach 2:
The invention recovers and reuses fuel that would otherwise be wasted. By circulating fuel through the anode and then back to the cathode, the system recovers the fuel's moisture-carrying capability to maintain cathode humidity while using the same fuel stream to remove water droplets from the anode, transforming a potential waste stream into a valuable resource
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 enhances fuel recirculation efficiency at low loads, effectively removes water droplets from the anode side, and reduces the complexity and cost of the system by optimizing fuel supply and pressure management.
Implementation Method 1
Vacuum ejectors (jet pumps) have also been employed to effect recirculation
Implementation Method 2
a low-flow nozzle and a low-flow diffuser, and a high-flow nozzle and a high-flow diffuser. The low-flow nozzle and diffuser are configured to entrain the recirculated flow at low loads
Implementation Method 3
They do not generate any pollutants and therefore have gained popularity as an attractive alternative to the internal combustion engine. One type of fuel cell that has been used for automotive and other industrial applications because of its low operating temperature is the solid polymer fuel cell. Solid polymer fuel cells employ a membrane electrode assembly ('MEA') that includes an ion exchange membrane disposed between two electrodes
Implementation Method 4
During normal operation of a solid polymer fuel cell, fuel is electrochemically oxidized at the anode catalyst, typically resulting in the generation of protons, electrons, and possibly other species depending on the fuel employed
Implementation Method 5
During normal fuel cell operation water is created on the cathode as a result of fuel oxidation. Some of the water produced at the cathode may pass to the anode side where it can condense, creating water droplets that may block the fuel flow field channels
Data Source
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AI summary
A fuel cell system comprising a fuel cell stack, a fuel recirculation line provided with a jet pump and a valve controlled by a control unit based on the anode-cathode pressure differential such that the valve is closed to reduce or stop fuel supply when the anode-cathode pressure differential reaches a predetermined value, and opened again to circulate more fuel through the jet pump when the pressure differential is below a predetermined value, to create a pulsed fuel supply that improves the fuel recirculation at low loads and ensures adequate water removal from the anode flow field channels.