Multi-Ejector Fuel Cell Recirculation for Parasitic Load Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fuel cell systems face challenges in achieving optimal operating conditions, particularly in maintaining efficient power delivery and minimizing parasitic load due to high pressure losses and excess fuel requirements, which can lead to fuel starvation, flooding, and MEA degradation.
Innovation Solution
The system employs multiple venturi or ejectors in series or parallel configurations, with a control valve and by-pass valve, to manage fuel flow and pressure, optimizing the entrainment ratio and turn down ratios to maintain efficient operation across varying current densities, reducing the need for recirculation pumps and minimizing 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 stack increases leading to higher parasitic load
Solution Approach 1:
The fuel cell system is divided into multiple segments (stacks or cells) with independent fuel flow control. Each segment can be optimized to operate at its own excess fuel ratio, allowing the system to meet overall excess fuel targets while minimizing total pressure loss by distributing flow across multiple lower-resistance paths.
Solution Approach 2:
The system dynamically adjusts fuel flow distribution across different segments based on operating conditions. By continuously optimizing the excess fuel ratio in each segment, the system maintains adequate fuel supply while minimizing parasitic load, adapting to changing demands rather than maintaining fixed high flow rates throughout.
2Adaptability or versatility
If a single ejector is used to manage fuel flow, then the system configuration is simple, but the system cannot maintain optimal entrainment ratio across wide current density ranges
Solution Approach 1:
The single ejector is segmented into multiple ejectors operating in parallel or series configurations. Each ejector is sized and tuned to handle specific portions of the operating range, allowing the system to maintain optimal entrainment ratios across wide current density variations while distributing the complexity across multiple manageable components.
Solution Approach 2:
The multi-ejector configuration creates a universal fuel management system that can adapt to various operating conditions. By designing ejectors with different characteristics (sizes, pressure ratios), the system achieves multi-functionality, handling both low and high current density operations effectively within a single integrated architecture.
3Reliability
If recirculation pumps are used to maintain fuel flow, then fuel supply is ensured, but parasitic load increases
Solution Approach 1:
The ejector system is designed to be self-service, using the pressure differential naturally present in the fuel cell operation to drive fuel flow and recirculation. The ejectors leverage the existing high-pressure fuel inlet and low-pressure exhaust to create the necessary flow without requiring external powered pumps, thereby ensuring reliable fuel supply while eliminating pump-related parasitic loads.
Solution Approach 2:
The system uses pneumatic principles through the ejector design, where high-pressure fuel gas expands through the ejector to create suction that draws in and recirculates exhaust gases. This pneumatic-driven recirculation replaces mechanical pump systems, maintaining fuel supply reliability while significantly reducing parasitic energy consumption.
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 allows for efficient fuel cell operation across a wide current density range, reducing parasitic loads and preventing MEA degradation by optimizing fuel flow and pressure management, thereby enhancing system efficiency and longevity.
Implementation Method 1
The present disclosure relates to systems and methods of operating a system comprising more than one venturi or ejector and a fuel cell or fuel cell stack
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The present disclosure generally relates to systems and methods comprising more than one venturi or ejector with a fuel cell or fuel cell stack.