Fuel Cell Ejector Sizing to Cut Recirculation Parasitic Load
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Solution Overview
Problem
Fuel cell systems face high parasitic loads and costs due to the use of recirculation pumps or blowers, which are necessary to compensate for pressure losses in fuel cell stacks, leading to inefficiencies and increased energy consumption.
Innovation Solution
The implementation of a venturi or ejector system that operates at a critical current density, optimizing fuel delivery without the need for a blower, by sizing the ejector to achieve a required entrainment ratio and maintaining effective efficiency across varying operating conditions, including pressure and temperature adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If recirculation pumps or blowers are used to compensate for pressure losses in fuel cell stacks, then the excess fuel level can be maintained above the minimum target, but the parasitic load on the fuel cell system increases
Solution Approach 1:
The patent extracts the recirculation pump or blower from the system by replacing it with a passive ejector device. The ejector uses the kinetic energy of the primary fuel stream to entrain and recirculate the secondary fuel stream without requiring external mechanical power, thereby eliminating the parasitic load associated with active recirculation devices while maintaining the required excess fuel level.
Solution Approach 2:
The patent replaces the mechanical recirculation system (pump or blower) with a fluid dynamic system based on the ejector effect. The ejector converts the kinetic energy of the primary fuel stream into a low-pressure region that passively draws and mixes secondary fuel, substituting mechanical work with fluid dynamic principles to achieve the same recirculation function without additional energy consumption.
2Quantity of substance
If high fuel flow rates are maintained at the anode to achieve higher excess fuel levels, then the excess fuel target is met, but pressure loss in the fuel cell increases
Solution Approach 1:
The ejector acts as an intermediary device that introduces secondary fuel into the primary fuel stream through entrainment. This allows the system to achieve the required excess fuel level by mixing recirculated fuel with fresh fuel, rather than simply increasing the total fuel flow rate, thereby avoiding the pressure losses associated with high flow rates while still meeting the excess fuel target.
3Stress or pressure
If recirculation pumps or blowers are used to overcome pressure loss, then the required pressure can be maintained, but additional power consumption increases
Solution Approach 1:
The ejector is a self-service device that uses the kinetic energy of the primary fuel stream to create the low-pressure region necessary for entraining secondary fuel. The system serves itself by converting the available kinetic energy into the pressure differential needed for recirculation, eliminating the need for external power sources while maintaining the required operating pressure.
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 reduces parasitic loads and costs by eliminating the need for recirculation pumps or blowers at certain current densities, enhancing fuel cell system efficiency and performance while maintaining optimal operating pressures and humidity levels.
Implementation Method 1
The ejector has a first fuel entering a first inlet at a first pressure (PO) and a second fuel entering a second inlet at a second pressure (PS). The first fuel and the second fuel exit an ejector exit at an ejector exit pressure.
Implementation Method 2
The ejector is sized to fully deliver the second fuel for a required entrainment ratio (ER) at a critical current density.
Data Source
AI summary
The present disclosure generally relates to systems and methods for optimizing the use of a venturi or an ejector and reducing costs and parasitic loads associated with using the venturi or an ejector with a recirculation pump or blower in a fuel cell, fuel cell stack, and/or fuel cell system.