Compressor Recirculation Valve Control for Fuel Cell Transients

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Solution Overview

Problem

In vehicle fuel cell systems, the coupling of pressure and flow control in compressors leads to destabilization during transient operating conditions, particularly during downtransient events, causing potential stack dryout or flooding due to inadequate recirculation flow management.

Innovation Solution

A method for controlling the compressor recirculation valve that calculates a predicted recirculation valve flow setpoint using operational data and feedforward control, incorporating a compressor map and PID controller to adjust valve positions, ensuring precise flow management and minimizing humidity imbalances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a recirculation valve is added to control cathode flow, then flow control precision is improved, but device complexity increases

Engineering Contradiction:

Improveflow control precisionVSAvoiddevice complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements a feedback control system where the controller continuously monitors cathode flow conditions and adjusts the recirculation valve position accordingly. The controller receives feedback signals about the actual flow conditions and compares them with the desired flow setpoint, then generates control commands to minimize the error. This closed-loop feedback mechanism enables precise flow control while systematically managing the complexity through automated control algorithms.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The recirculation valve acts as an intermediary component that mediates between the compressor output and the cathode inlet. By introducing this intermediate control element, the system can precisely regulate the flow reaching the cathode without directly modifying the compressor operation. The valve serves as a buffer that decouples the compressor's inherent pressure-flow coupling from the cathode's flow requirements, enabling independent flow control.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Use of energy by moving object

If compressor speed is reduced during downtransient, then energy consumption is reduced, but response time to meet flow setpoint deteriorates

Engineering Contradiction:

Improvecompressor energy consumptionVSAvoidcompressor response speed

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The control system performs preliminary actions by anticipating the need for flow adjustment during downtransient conditions. When a decrease in power demand is detected, the controller proactively adjusts the recirculation valve position before the compressor speed can naturally respond. This preliminary valve adjustment compensates for the compressor's inertial lag, ensuring that the cathode flow setpoint is met without waiting for the compressor to slow down, thereby maintaining both energy efficiency and response performance.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent replaces direct mechanical control of compressor speed with a valving-based flow control mechanism. Instead of relying solely on mechanical inertia and speed changes to regulate flow, the system uses the recirculation valve to mechanically divert or redirect flow. This substitution allows for quicker, more precise flow adjustments independent of compressor speed changes, decoupling the energy consumption (speed) from the flow control function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If recirculation flow is increased to prevent dryout, then stack humidity stability is improved, but risk of flooding increases

Engineering Contradiction:

Improvestack humidity stabilityVSAvoidstack flooding risk

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The controller implements feedback monitoring of cathode flow conditions to dynamically adjust recirculation valve position. By continuously sensing actual flow conditions and comparing them with the desired setpoint, the system can increase recirculation flow to prevent dryout when needed while simultaneously detecting conditions that would lead to flooding. The feedback loop automatically reduces recirculation when approaching flooding conditions, maintaining humidity stability without excessive flooding risk.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically changes the recirculation valve opening parameter based on real-time operating conditions. During downtransient events, the valve opening is increased to maintain minimum flow and prevent dryout. During uptransient or steady-state conditions, the valve opening is reduced to prevent flooding. This dynamic parameter adjustment allows the system to optimize humidity stability across different operating phases while avoiding the harmful extremes of both dryout and flooding.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9029036B2Systems and methods for controlling a compressor recirculation valve

Publication Date: 2015.05.12 GM GLOBAL TECHNOLOGY OPERATIONS LLC

AI summary

Systems and methods to control compressor recirculation of a reactant in a fuel cell system. A recirculation valve flow setpoint value for a gas flow to the recirculation valve is calculated based on a received cathode flow setpoint. A value corresponding to a predicted recirculation valve position is generated, and can be used as a control command for changing the position of the recirculation valve to reduce the valve response time during operational transients of the fuel cell system.