Variable Nozzle Ejector for Fuel Cell Hydrogen Recirculation
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Solution Overview
Problem
Existing hydrogen supply systems for fuel cell stacks face challenges in efficiently recirculating hydrogen while maintaining airtightness and internal pressure, particularly when using blowers, which are costly and prone to corrosion, and using multiple ejectors increases system size and complexity.
Innovation Solution
An ejector with a variable nozzle structure, featuring a poppet mechanism that adjusts the orifice area based on hydrogen flow rate, including a damage prevention member, spring, and guide member, to automatically control the hydrogen flow rate and prevent leakage between high and low-pressure regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a blower is used for hydrogen recirculation, then recirculation performance is improved, but cost increases and components are prone to corrosion
Solution Approach 1:
The patent replaces the mechanical blower system with a fluid dynamics-based ejector system. The ejector uses high-pressure hydrogen flow to create a vacuum effect and recirculate hydrogen without moving mechanical parts, thereby eliminating motors, bearings, and actuators that are prone to corrosion and failure.
Solution Approach 2:
The ejector utilizes pneumatic principles where high-pressure hydrogen serves as the driving fluid to generate suction and recirculate hydrogen through the fuel cell stack. The system leverages fluid pressure and flow dynamics rather than mechanical propulsion.
2Reliability
If the pressure at the front end of the ejector is increased to secure recirculation performance, then recirculation capability is improved, but airtightness and internal pressure performance deteriorate
Solution Approach 1:
The patent employs a variable nozzle area that dynamically adjusts based on operating conditions. The nozzle area is larger in the low-output section to enhance recirculation capability when needed, and smaller in the high-output section to maintain proper pressure and airtightness, thereby adaptively resolving the pressure contradiction.
Solution Approach 2:
The system changes the geometric parameter of the nozzle area to optimize performance across different operating sections. By varying the nozzle area parameter, the ejector can achieve high recirculation capability at low output while maintaining pressure integrity at high output.
3Productivity
If two ejectors are used to secure both low-output and high-output performance, then supply performance is improved, but system size increases
Solution Approach 1:
The patent designs a single ejector that performs multiple functions across different operating ranges. The variable nozzle structure enables one ejector to effectively handle both low-output recirculation and high-output supply requirements, eliminating the need for two separate ejectors and reducing overall system size.
Solution Approach 2:
The dynamic adjustment of the nozzle area allows a single ejector to adapt its performance characteristics to match different operating demands, effectively replacing what would traditionally require two fixed-performance ejectors.
4Device complexity
If the nozzle area is fixed, then device complexity is reduced, but the ability to adapt to different flow rates deteriorates
Solution Approach 1:
The patent implements a dynamic nozzle area that can change based on operating conditions. The nozzle area is variable rather than fixed, allowing the ejector to adapt to different hydrogen flow rates and pressure conditions throughout the fuel cell operating range.
Solution Approach 2:
The geometric parameter of the nozzle area is made variable to enable the ejector to adapt to different flow rates. This parameter change allows the system to optimize performance across low-output and high-output sections without increasing overall device complexity.
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 variable nozzle ejector stabilizes poppet movement, maintains airtightness, and adjusts hydrogen flow rate according to fuel cell output needs, preventing hydrogen leakage and ensuring efficient recirculation without increasing system size or complexity.
Implementation Method 1
The poppet is configured to adjust an area of an opening of the orifice discharging the hydrogen. The hydrogen flowing into the second housing is discharged through a space between the other side, i.e., a second side, opposite to the first side of the second housing and the poppet to move to the orifice.
Implementation Method 2
A hydrogen supply system is a system configured to receive high-pressure hydrogen from a hydrogen tank, to reduce a pressure of the hydrogen to a pressure required by a fuel cell stack, and to supply hydrogen. To recirculate a non-reaction gas, the hydrogen supply system should recirculate the non-reaction gas using a recirculation component such as a blower or an ejector.
Data Source
AI summary
An ejector has a variable nozzle structure and is installed in a fuel cell recirculation line to supply new hydrogen and a recirculation gas. The ejector includes: a first housing having a first hole through which hydrogen is supplied and an orifice through which the hydrogen is discharged; a second housing disposed in the first housing and having a second hole into which the hydrogen passing through the first hole flows; and a poppet penetrating a third hole defined at one side of the second housing. The poppet is configured to adjust an area of a space opened by the orifice discharging the hydrogen. The hydrogen flowing into the second housing is discharged through a space between the other side opposite to the one side of the second housing and the poppet to move to the orifice.