Fuel Cell Ejector Geometry for Wider Operating Range
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Solution Overview
Problem
Current fuel cell systems face high parasitic loads due to excessive fuel flow rates, which lead to pressure losses and increased power consumption by recirculation pumps and blowers, and existing venturi/ejector designs fail to optimize performance across varying operating conditions, including low current densities and thermodynamic limitations.
Innovation Solution
The optimization of venturi/ejector geometry by adjusting parameters such as mixer area ratio, diffuser diverging angle, and nozzle configurations to balance performance across highest and lowest current density operating points, incorporating a controller to manage blower operation and by-pass valves, and integrating multiple ejectors in series or parallel configurations to enhance efficiency and reduce parasitic loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high fuel flow rates are maintained at the anode to achieve higher excess fuel levels, then the excess fuel target is met, but pressure loss in the fuel cell increases
Solution Approach 1:
The fuel cell system is divided into multiple cells with individual flow control, allowing optimization of fuel distribution across different operating conditions without requiring uniformly high flow rates throughout the entire stack
Solution Approach 2:
The system implements dynamic fuel flow control that adjusts flow rates based on real-time operating conditions (current density, temperature, pressure), enabling the system to meet excess fuel targets while minimizing pressure losses by avoiding unnecessarily high flow rates
2Productivity
If recirculation pump capacity is increased to compensate for pressure loss, then fuel circulation is improved, but parasitic load on the fuel cell system increases
Solution Approach 1:
The system uses the fuel cell's own operating parameters (pressure differential, flow rate, current density) to automatically regulate recirculation pump operation, eliminating the need for external control systems and reducing parasitic load while maintaining adequate fuel circulation
Solution Approach 2:
The recirculation pump operates based on changing system parameters (pressure, flow rate, temperature), adjusting its capacity dynamically to match actual circulation needs rather than operating at fixed high capacity, thereby reducing parasitic load while maintaining productivity
3Power
If venturi or ejector geometric parameters are optimized for highest current density operating point, then performance at high current density is improved, but performance at low current density deteriorates
Solution Approach 1:
The venturi/ejector geometry is designed to perform multiple functions across different operating ranges by incorporating features that are effective both at high current density (where high power is needed) and at low current density (where adaptability is needed), making the single geometric design universally applicable across the entire operating range
Solution Approach 2:
Different sections of the venturi/ejector have locally optimized geometries that address specific operating conditions, with certain regions optimized for high current density flow patterns while other regions maintain characteristics that support low current density operation, achieving both performance targets through spatial differentiation
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 reduces parasitic loads, extends the operating range of venturi/ejectors, and optimizes fuel cell system performance by minimizing power consumption and maintaining efficient fuel delivery across transient states, thereby enhancing overall system efficiency and reducing costs.
Implementation Method 1
The ejector includes a primary nozzle, a mixer, a mixer entrance, a mixer inlet area, a mixer length, a mixer diameter, a mixer outlet area, a diffuser, and a diffuser outlet area. The first fuel from a fuel supply flows through the primary nozzle into the mixer. The second fuel flows through an anode recirculation loop which includes a secondary suction chamber into the mixer.
Data Source
AI summary
The present disclosure is generally directed to a design geometry of a venturi or an ejector that is optimized in systems and methods for increasing the operating range of the venturi or the ejector in a fuel cell system. The present disclosure is also generally directed to fuel cell systems and methods for sizing and/or integrating a recirculation blower with a venturi or an ejector in a fuel cell or fuel cell stack. The present disclosure is further generally directed to systems and methods of operating a fuel cell system comprising more than one venturi or ejectors during transient operations.