Fuel Cell Impeller Pressure Control
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Solution Overview
Problem
In fuel cell systems, the pressure inside the housing can become higher than the impeller back face pressure, leading to oil leakage from the housing into the oxidant gas supply passage, which can contaminate the fuel cell.
Innovation Solution
A controller is used to execute specific processes that either increase the speed of the impeller after decreasing the pressure-regulating valve opening degree or increase the valve opening degree after decreasing the impeller speed, thereby maintaining a positive impeller back face pressure and preventing oil leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bypass pressure-regulating valve is opened more to discharge more oxidant gas, then the gas flow rate increases, but the pressure inside the housing becomes higher than the impeller back face pressure causing oil leakage
Solution Approach 1:
The controller executes a first process that increases the impeller speed before opening the bypass pressure-regulating valve. This preliminary speed increase ensures that the impeller back face pressure is already elevated, creating a pressure buffer that prevents oil leakage when the valve is subsequently opened to increase gas discharge rate.
Solution Approach 2:
The control system establishes a cushioning pressure difference by increasing impeller speed in advance. This creates a pressure margin between the impeller back face and the housing interior, cushioning against the potential negative pressure effect that would occur when the bypass valve is opened, thereby preventing oil leakage while allowing increased gas flow.
2Reliability
If the speed of the impeller is increased to prevent negative impeller back face pressure, then oil leakage is suppressed, but the control process becomes more complex
Solution Approach 1:
The controller dynamically adjusts the impeller speed based on the operating state of the bypass pressure-regulating valve. When the valve opening degree changes, the controller automatically modifies the impeller speed to maintain positive impeller back face pressure. This dynamic control adapts to varying operating conditions while preventing oil leakage.
Solution Approach 2:
The control system implements a feedback mechanism where the controller continuously monitors the opening degree of the bypass pressure-regulating valve and adjusts the impeller speed accordingly. When the valve opening changes, the controller receives this information and automatically modifies the impeller speed to maintain the required pressure differential, creating a closed-loop control system.
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 effectively suppresses oil leakage into the oxidant gas supply passage, ensuring the fuel cell system operates efficiently by maintaining a positive impeller back face pressure and reducing the complexity of control processes.
Implementation Method 1
an impeller disposed in the oxidant gas supply and discharge passage to deliver the oxidant gas
Implementation Method 2
a pressure-regulating valve disposed on a downstream side of the air compressor in the oxidant gas supply and discharge passage
Data Source
AI summary
A fuel cell system includes: an air compressor that sends out oxidant gas to a fuel cell stack, including a motor, a housing, and an impeller; an oxidant gas supply and discharge passage; a pressure-regulating valve; and a controller. The controller executes at least one of a first process and a second process, the first process being executed for increasing a speed of the impeller after decreasing an opening degree of the pressure-regulating valve in a first operation where both decreasing the opening degree of the pressure-regulating valve and increasing the speed of the impeller are performed, the second process being executed for increasing the opening degree of the pressure-regulating valve after decreasing the speed in a second operation where both increasing the opening degree of the pressure-regulating valve and decreasing the speed are performed.