Dual-Ejector Fuel Recirculation for Variable-Power Fuel Cells
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Solution Overview
Problem
Fuel cell systems face complexity and increased power consumption due to the need for recirculation pumps and single ejectors that fail to meet varying power levels, leading to hysteresis and inaccurate system control.
Innovation Solution
A fuel supply apparatus with parallel branches and ejectors, controlled by valves that isolate or engage recirculation based on power levels, reducing complexity and power consumption by using ejectors only when necessary, and integrating components like proportional valves and pressure sensors into a modular manifold unit for improved efficiency and ease of installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pump is used to recirculate residual fuel, then recirculation function is achieved, but system complexity and power consumption increase
Solution Approach 1:
The patent replaces the mechanical pump system with a fluid dynamics-based ejector system. The ejectors use the existing fuel flow through the fuel cell stack to create a vacuum that draws residual fuel from the stack outlet and mixes it back into the supply line, eliminating the need for a mechanical pump and reducing system complexity
Solution Approach 2:
The ejector system is self-actuating, using the kinetic energy of the main fuel flow passing through the fuel cell stack to drive the recirculation process. The fuel flow itself creates the suction needed to pull residual fuel back into the supply line, requiring no external power source
2Device complexity
If a single ejector is used for fuel recirculation, then system complexity is reduced, but the system cannot meet fuel recirculation requirements at all power levels
Solution Approach 1:
The patent divides the recirculation system into multiple parallel ejector branches (first ejector and second ejector), each capable of operating independently. This segmentation allows the system to activate only the necessary number of ejectors based on the fuel cell stack's power level and residual fuel generation rate
Solution Approach 2:
The system dynamically adjusts the number of active ejectors based on operating conditions. Control valves regulate fuel flow to each ejector, enabling the system to scale recirculation capacity from a single ejector at low power levels to multiple ejectors operating in parallel at high power levels
3Productivity
If multiple components are used to optimise flow throughout the system, then flow control is improved, but the system remains complex with hysteresis causing inaccurate control
Solution Approach 1:
The patent combines multiple control functions into integrated control valves that manage both the main fuel supply and the recirculation flow paths. The control valves are positioned to simultaneously regulate fuel distribution to multiple ejectors and maintain proper flow balance, reducing the number of separate components needed
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
The solution reduces system complexity and power consumption by using ejectors efficiently, improves recirculation performance, and enhances control accuracy through closed-loop control, resulting in a more cost-effective and compact fuel supply system.
Implementation Method 1
a first ejector for introducing recirculated fuel from the first branch of the fuel recirculation flow path to the first branch of the fuel supply flow path; a second ejector for introducing recirculated fuel from the second branch of the fuel recirculation flow path to the second branch of the fuel supply flow path
Data Source
AI summary
A fuel supply apparatus for a fuel cell system, the apparatus comprising a fuel supply flow path by which fuel is supplied to an inlet of said fuel cell system, wherein the fuel supply flow path comprises a first branch, and a second branch arranged in parallel to the first branch; a fuel recirculation flow path by which residual fuel is transferred from an outlet of said fuel cell system to the fuel supply flow path, wherein the fuel recirculation flow path comprises a first branch and a second branch; a first ejector for introducing recirculated fuel from the first branch of the fuel recirculation flow path to the first branch of the fuel supply flow path; a second ejector for introducing recirculated fuel from the second branch of the fuel recirculation flow path to the second branch of the fuel supply flow path; a first valve for controlling flow at the second branch of the fuel supply flow path, and a second valve for controlling flow at the second branch of the fuel recirculation flow path, wherein the first and second valves each have a first, closed position where flow is prevented and a second, open position where flow is permitted. When said fuel cell system is operated at a first, lower, power rate, the first and second valves are in the first, closed position, such that the introduction of recirculated fuel to the second branch of the fuel supply flow path at the second ejector is prevented; and when said fuel cell system is operated at a second, higher, power rate, the first and second valves are in the second, open position, such that recirculated fuel is introduced to the second branch of the fuel supply flow path at the second ejector.