Fuel Injector Flow Switching to Prevent Stagnation Cooling Loss
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Solution Overview
Problem
In a fuel cell system with multiple injection devices, stopping one injection device can cause stagnation in the fuel flow passage, affecting the operation of both the stopped and operating injectors, particularly in high-temperature systems like solid oxide fuel cells, where sufficient cooling is crucial.
Innovation Solution
A fuel cell system is configured with a first injection device downstream and a second injection device upstream in the fuel flow passage, where the second device operates at a lower frequency than the first, allowing for switching between flow passages to prevent stagnation and maintain cooling effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If one injection device is stopped to operate another injection device, then the fuel cell system can switch flow passages to maintain operational flexibility, but stagnation occurs in the flow passage of the stopped injection device, reducing cooling effectiveness
Solution Approach 1:
The patent maintains continuous fuel flow through the flow passage by preventing complete stagnation. When one injection device is stopped, the system ensures that fuel continues to flow through the passage at a minimal rate or is periodically flushed, preventing temperature rise and maintaining cooling effectiveness throughout the entire flow passage duration.
Solution Approach 2:
The patent implements periodic operation of injection devices where stopped devices are periodically activated or flushed. This periodic action prevents continuous stagnation in the flow passages, maintaining adequate cooling by periodically refreshing the fuel flow through all passages regardless of current operational status.
2Reliability
If an injection device operates at high frequency, then fuel supply reliability is improved, but thermal load on the injection device increases, potentially causing overheating
Solution Approach 1:
The patent divides the fuel injection function into multiple injection devices distributed throughout the system. By segmenting the injection tasks across multiple devices rather than relying on a single high-frequency device, the thermal load is distributed and reduced on each individual device while maintaining overall fuel supply reliability through redundancy.
3Temperature
If fuel flow velocity is increased to prevent stagnation, then cooling effect is improved, but fuel consumption increases and system efficiency decreases
Solution Approach 1:
The patent applies different flow conditions to different locations in the fuel system. High-velocity flow is maintained only in passages requiring cooling, while other passages operate at lower velocities when not actively cooling. This localized approach to flow velocity optimization provides adequate cooling where needed without unnecessarily increasing overall fuel 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 configuration suppresses stagnation in the fuel flow passage, ensuring stable fuel supply and cooling, reducing thermal loads on injectors, and promoting efficient warmup and operation of the fuel cell system, especially at high temperatures.
Implementation Method 1
since the sufficient cooling effect by the raw fuel as a cooling medium cannot be obtained
Data Source
AI summary
The fuel cell system includes a fuel cell, a first injection device associated with a supply of a fuel to the fuel cell, and a second injection device provided on an upstream side of the first injection device in a fuel flow passage from a fuel storage unit to the first injection device. The first and second injection devices switch a flow passage extending downstream from the fuel flow passage, between a first flow passage via the first injection device and second flow passage via the second injection device. The second injection device operates at a lower frequency than the first injection device during an operation of the fuel system.