Dual Ejector Fuel Cell System with Dynamic Pressure Control
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Solution Overview
Problem
In fuel cell systems, replacing gas supply using an ejector with high circulation characteristics with one having low circulation characteristics is challenging due to excessive gas supply and deterioration of drainage properties, particularly when the high-circulation ejector is blocked or in an abnormal state.
Innovation Solution
A fuel cell system configuration that includes two ejectors with different circulation characteristics, a control device to manage the gas supply from each ejector, and a gas-liquid separator to maintain optimal pressure and drainage, allowing for seamless switching between ejectors to prevent excessive gas supply and ensure efficient drainage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gas supply is executed using a low-circulation ejector to replace a blocked high-circulation ejector, then gas supply continuity is maintained, but excessive gas supply occurs and drainage properties deteriorate
Solution Approach 1:
The control device dynamically adjusts the supply time of the low-circulation ejector based on real-time pressure feedback from the pressure sensor. When the high-circulation ejector is blocked, the system switches to the low-circulation ejector and modifies its operating parameters (supply time) to match the circulation characteristics of the high-circulation ejector, thereby maintaining appropriate gas supply quantity while ensuring continuity.
Solution Approach 2:
The system employs a pressure sensor to continuously monitor the pressure in the anode system and provides feedback to the control device. This feedback mechanism enables the control device to adjust the supply time of the low-circulation ejector to maintain pressure within an appropriate range, preventing both excessive gas supply and pressure fluctuations that would impair drainage.
2Quantity of substance
If supply time from the low-circulation ejector is shortened to reduce fuel gas supply amount, then excessive gas supply is suppressed, but pressure fluctuation range is reduced making it difficult to discharge anode liquid water
Solution Approach 1:
The control device executes supply from the low-circulation ejector at periodic intervals (supply cycles) rather than continuously. By optimizing the supply cycle and supply time parameters, the system creates periodic pressure fluctuations that are sufficient to discharge anode liquid water through the gas-liquid separator, while keeping the average gas supply amount within appropriate limits.
Solution Approach 2:
The system changes the operating parameters (supply time and supply cycle) of the low-circulation ejector to match the circulation characteristics of the high-circulation ejector. This parameter optimization ensures that pressure fluctuations remain within an appropriate range that enables effective drainage while controlling the total fuel gas supply amount.
3Ease of operation
If supply time and supply cycle are increased to maintain pressure fluctuations for drainage, then drainage property is improved, but excessive gas supply occurs
Solution Approach 1:
The control device implements periodic supply cycles with optimized supply time durations. This periodic action creates the necessary pressure fluctuations for drainage while limiting the total supply time within each cycle, thereby preventing excessive cumulative gas supply. The key is optimizing both the supply time duration and the cycle frequency.
Solution Approach 2:
The pressure sensor provides continuous feedback on the pressure state, enabling the control device to adjust supply parameters in real-time. This feedback ensures that pressure fluctuations remain within the appropriate range needed for drainage while preventing excessive gas accumulation, thus balancing drainage effectiveness with gas supply control.
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 system effectively replaces high-circulation ejector gas supply with low-circulation ejector supply while maintaining optimal pressure and drainage properties, preventing excessive gas supply and ensuring efficient operation even when the high-circulation ejector is abnormal.
Implementation Method 1
a first ejector configured to suck the off gas from the gas-liquid separator using the fuel gas from the first supply device as a driving fluid and to discharge the off gas toward the fuel cell together with the fuel gas such that the off gas circulates to the fuel cell; a second ejector configured to suck the off gas from the gas-liquid separator using the fuel gas from the second supply device as a driving fluid
Implementation Method 2
a gas-liquid separator configured to separate liquid water from off gas discharged from the fuel cell and to store the liquid water
Data Source
AI summary
A fuel cell system includes a fuel cell, first and second supply devices, a gas-liquid separator, a discharge valve, first and second ejectors for discharging fuel gas and off gas to the fuel cell, a measuring device for gas pressure, and a control device. The first ejector has a discharge amount smaller than the second ejector. The first ejector has a circulation amount larger than the second ejector. The control device executes the supply during a first time from the first supply device at each first cycle such that the pressure becomes a first target value, and when the first ejector is in an abnormal state, stops the first supply device, executes the supply during a shorter second time from the second supply device at each shorter second cycle such that the pressure becomes a higher second target value, and opens and closes the discharge valve at each first cycle.