Fuel Cell Flooding Research Articles

A novel sensor preference method for proton exchange membrane fuel cell flooding fault diagnosis based on multi-algorithm

ABSTRACT During periods of high-power operation, proton exchange membrane fuel cell (PEMFC) produce water, which gradually accumulates at the cathode. It causes flooding faults and significantly impacts on PEMFC safety. The data collected by the sensors is a fundamental prerequisite for the flooding faults diagnosis in PEMFC. Consequently, it is critical to select sensors. However, the conventional methods for selecting sensors consider sensitivity and noise immunity, the number of sensors selected and the flood diagnostic performance are not optimized. To solve the above problems, this paper proposes a sensor preference method that combines the Mantel test and Spearman coefficient (MS method). This method first uses the Mantel test to analyze the correlation between two flooding evaluation indicators and the sensors, it identifies suitable sensors for diagnosing flooding faults. Subsequently, the Spearman coefficient eliminates redundant sensors. Additionally, a one-dimensional convolutional neural network is employed to construct a flooding diagnosis model. The MS method is contrasted with two traditional sensor selection methods. The results show that the MS method selected sensors yield superior model training and enhanced accuracy in diagnosing flooding, thereby ensuring PEMFC safety.

Experimental investigation of the two-phase flow distribution and pressure drop characteristic within the cathode bending type channel of fuel cell

The accurate prediction of the two-phase flow distribution within the channel is of great significance for enhancing fuel cell water management and improving output efficiency. The current study constructs a novel transparent fuel cell visualization test system and experimentally investigates the characteristics of two-phase flow pattern distribution, pressure drop, and output voltage within the bending type channel. Furthermore, a focused analysis of slug flow which may induce fuel cell flooding is conducted. The results show that the two-phase flow pattern maps of both the bent and straight channels are highly consistent. The force balance analysis is performed to explain the internal mechanism that the bending structure has less influence on the two-phase flow pattern. Additionally, the bending structure has a significant impact on the channel pressure drop magnitude and time-domain characteristics. The two-phase pressure drop can be used as an empirical tool to judge the flow pattern and occurrence position. The fuel cell output voltage jump phenomenon occurs under slug flow pattern, and there is a strong positive correlation between the voltage jump amplitude and current density, with a Pearson correlation coefficient of 0.924. The research results provide theoretical guidance for two-phase flow prediction within the channel and flood prevention of the fuel cell.

Experimental investigation on PEM fuel cell flooding mitigation under heavy loading condition

Water flooding is a crucial factor affecting the lifetime of a proton exchange membrane (PEM) fuel cell. In this paper, A laboratory-scale (25 cm2) single PEM fuel cell was tested to investigate the characteristics of fuel cell under a load shedding process with various air flow rates. The performance was assessed using output power and electrochemical impedance spectroscopy, while the cathode flooding was identified using voltage and cathode pressure drop. The results show that reducing the load within a specific range can lower the impedance and lessen floods. The results also demonstrate that there is an optimal inlet flow rate interval considering its effect on system efficiency, durability, and water flooding. In addition, a stepped load shedding pattern was proposed to solve the flooding problem of a fuel cell while taking the power demand into account. The effect of load shedding cycle and air inlet flow rate on flooding was evaluated by comparing the flooding severity coefficient and output power. The results prove that a longer current reduction cycle is more favorable in alleviating flooding problems. The optimal mode for the fuel cell in this paper was determined according to the flooding situation and power variation. Finally, the approach to obtaining the optimal load shedding pattern for other PEM fuel cells system was summarized. The flooding mitigation approach proposed in this paper can be utilized as a guide for developing strategies to extend the life of PEM fuel cells.

Data-based flooding fault diagnosis of proton exchange membrane fuel cell systems using LSTM networks

Flooding fault diagnosis is critical to the stable and efficient operation of fuel cells, while the on-board embedded controller has limited computing power and sensors, making it difficult to incorporate the complex gas-liquid two-phase flow models. Then in fuel cell system for cars, the neural network modeling is usually regarded as an appropriate tool for the on-line diagnosis of water status. Traditional neural network classifiers are not good at processing time series data, so in this paper, Long Short-Term Memory (LSTM) network model is developed and applied to the flooding fault diagnosis based on the embedded platform. Moreover, the fuel cell auxiliary system statuses are adopted as the inputs of the diagnosis network, which avoids installing a large number of sensors in the fuel cell system, and contributes to reduce the total system cost. The bench test on the 92 kW vehicle fuel cell system proved that this model can effectively diagnose/pre-diagnose the fuel cell flooding, and thus help optimize the water management under vehicle conditions.

Effects of Applying Brand-New Designs on the Performance of PEM Fuel Cell and Water Flooding Phenomena

Numerous researchers use numerical simulations to precisely recognize the processes before mass-production to provide a basic model for optimizing the fuel cell. In this study, we presented brand-new designs for cylindrical PEMFCs in the Three-Dimensional form. We used the Finite Volume Method to simulate the fuel cell processes and established a genuine correspondence between our simulation results and valid outcomes. We introduced innovative designs to increase the performance of cylindrical polymer fuel cells. Then, we examined the effects of progressive developments in cross-section design, the fuel cell structure, the output current densities, and, eventually, the flooding phenomenon. The results revealed the optimum capacity of the cylindrical fuel cell compared with an elliptical cross-section. Due to more extensive transport zones and pressure drop effects, we need to find the optimum cell capacity to pass the reactive regions.

Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave

Removal of Flooding in a PEM Fuel Cell at Cathode by Flexural Wave

Investigation of PEMFC fault diagnosis with consideration of sensor reliability

Despite the wide range of applications for the polymer electrolyte membrane fuel cell (PEMFC), its reliability and durability are still major barriers for further commercialization. As a possible solution, PEMFC fault diagnosis has received much more attention in the last few decades. Due to the difficulty of developing an accurate PEMFC model incorporating various failure mode effects, data-driven approaches are widely used for diagnosis purposes. These methods depend largely on the quality of sensor measurements from the PEMFC. Therefore, it is necessary to investigate sensor reliability when performing PEMFC fault diagnosis.In this study, sensor reliability is investigated by proposing an identification technique to detect abnormal sensors during PEMFC operation. The identified abnormal sensors will be removed from the analysis in order to guarantee reliable diagnostic performance. Moreover, the effectiveness of the proposed technique is investigated using test data from a PEMFC system, where fuel cell flooding is observed. During the test, due to accumulation of liquid water inside the PEMFC, the humidity sensors will give misleading readings, and flooding cannot be identified correctly with inclusion of these humidity sensors in the analysis. With the proposed technique, the abnormal humidity measurements can be detected at an early stage. Results demonstrate that by removing the abnormal sensors, flooding can be identified with the remaining sensors, thus reliable health monitoring can be guaranteed during the PEMFC operation.

Proton Exchange Membrane Fuel Cell Flooding Caused by Residual Functional Groups after Platinum Atomic Layer Deposition

Proton exchange membrane fuel cell (PEMFC) catalysts manufactured using atomic layer deposition (ALD) on unmodified and functionalized carbon were compared to a commercial catalyst in half- and whole-cell tests. Half-cell tests showed the ALD catalyst performed better or comparable to a commercial catalyst. Conversely, whole-cell tests revealed flooding in the ALD catalyst produced on functionalized carbon. Residual functional groups had reduced the hydrophobicity, and rendered this catalyst impractical for use in whole-cell PEMFC applications. However, the ALD catalyst produced on unmodified carbon performed better than the commercial catalyst, which illustrates the power of ALD on appropriate catalyst supports.

Fuel cell flooding diagnosis based on time-constant spectrum analysis

Proton Exchange Membrane (PEM) Fuel Cell is a key component for the exploitation of hydrogen energy. Its diagnosis relies on several in-situ diagnosis tools. Electrochemical impedance spectroscopy is a major one. But this technic has some drawbacks, among which the complexity of the required equipment and the measurement time. An alternative method for diagnosis is developed in this work. A time-constant spectrum (or relaxation-time distribution) is extracted from the fuel cell voltage response to small current steps. This spectrum can be read as a distribution of series RC cell representing, such as an impedance spectrum, the whole dynamic of the voltage response to a given current excitation. In order to demonstrate the ability of the method to diagnose flooding, different simulations of voltage responses are first performed using appropriated parameters’ variations in a fuel cell model. The resulting time-constant spectrums are analyzed to underline the sensitivity to the flooding effect. Then, experiments are achieved to confirm the potentiality of this technic to diagnose flooding.

Model-based estimation of liquid saturation in cathode gas diffusion layer and current density difference under proton exchange membrane fuel cell flooding

Poor water management usually leads to various degrees of flooding and exacerbates oxygen starvation, both of which affect the performance and durability of a proton exchange membrane fuel cell (PEMFC). This paper proposes a model-based approach to estimating the liquid saturation and current density difference simultaneously. The current density difference is a parameter that indicates the oxygen starvation level. For estimation purposes, a fuel cell cathode model with separate inlet and outlet subsystems is developed to incorporate the effect of harmful phenomena such as flooding and oxygen starvation on the system dynamics and cell voltage. The cathode gas diffusion layer (GDL) flooding and oxygen starvation diagnoses are formulated as state estimation problems. The proposed approach is validated through an offline simulation using experimental data. The offline prediction suggests the effect of the anode purge and air steam conditions on the internal states of the PEMFC, which is helpful for system optimization and control design. The estimation problems are further decoupled, and a simplified algorithm is designed for onboard applications. Finally, the modified fuel cell model and optimized estimation algorithm are applied to an online test system as a demonstration.

The impact of operating parameters and system architecture on the water management of a multifunctional PEMFC system

The focus of this paper is on multifunctional PEMFC application considering the products electric power and oxygen depleted air (ODA) to be used in aviation. Presented are operation and architecture analyses of a PEMFC system (HyPM XR 12) based on process simulations as well as experimental investigations. The effects of the stack temperature (20–90 °C), the operating pressure (0.2–2.0 bar) and the cathode stoichiometric ratio (1.0–5.0) on the resulting average relative humidity of the cathode exhaust gas and consequently on the efficiency and stability are evaluated for a single and a highly innovative twin system (serial cathode including an interim condensation process).The results achieved are used to identify operation and architecture improvements for an appropriate water management, a key aspect to optimize efficiency and stability of PEMFC systems [1]. Based on the process simulation and experimental investigations can be summarized: In single and twin system operation the stack temperature and the cathode stoichiometric ratio have to be decreased at reduced operating pressure to avoid membrane dehydration. An additional feed gas humidification could be appropriate, especially at low pressure operation. The twin system architecture is relevant to minimize fuel cell flooding at high operating pressure and low stoichiometric ratios required to achieve ODA specifications.

Investigation of an Indicator for On-line Diagnosis of Polymer Electrolyte Membrane (PEM) Fuel Cell Flooding using Model Based Techniques

The durability and reliability of producing high quality power for long periods of time have the potential to be the leading marketing factors for future hydrogen and fuel cell power sources. In the past few decades, several researchers have been devoted to investigating diagnostic techniques for fuel cell systems. However, in commercial fuel cell applications, on-line diagnosis is urgently required so that fuel cell degradation can be detected at its early stage, and mitigation strategies can be performed to recover fuel cell performance. In this paper, on-line diagnosis of fuel cell flooding is investigated. For this purpose, a generalised fuel cell stack model is developed, and water mass balance equations are used to study water balance inside the fuel cell stack. Moreover, with these equations, the flooding indicator is proposed and its relationship with liquid water inside the stack is evaluated. Results demonstrate that the proposed indicator is sensitive to the liquid water in the stack, thus can be used for flooding diagnosis. Furthermore, the expectation of the proposed indication in the cell flooding case is also presented. The advantage of this method is that parameters in the flooding indicator can be determined with measurements from tests, thus quick diagnosis can be made during the practical fuel cell operation.

An analysis of fluidic voltage statistical correlation for a diagnosis of PEM fuel cell flooding

The fault diagnosis is one of the most important topics on Proton Exchange Membrane Fuel Cell (PEMFC) stacks. Statistical methodologies for diagnosis are considered as one of the most relevant. This paper is dedicated to the diagnosis of flooding, using statistical methodology.In the literature, previous researches establish that in PEM (Proton Exchange Membrane) fuel cell stacks, single cell voltage variance increases when flooding conditions appear at the cathode side of the fuel cell stack. In this paper, these flooding conditions were completed by increasing the hygrometry of the inlet air flow at constant temperature of the fuel cell stack, or by decreasing the temperature of the fuel cell stack at constant hygrometry of inlet air flow. The obtained experimental results are here correlated with a fluidic model of flooding conditions. This new diagnosis approach directly provides the percentage of flooded channels in the fuel cell stack as a measure of the flooding of the fuel cell stack.

Impact of Microchannel Boundary Conditions and Porosity Variation on Diffusion Layer Saturation and Transport in Fuel Cells

Polymer electrolyte membrane (PEM) fuel cell flooding can be detrimental to energy generation performance due to its role in reducing gas diffusion layer (GDL) oxygen transport. Previous transport models have made use of a zero-saturation boundary condition at the GDL/oxygen gas channel (GC) interface. However, the physical accuracy of this boundary condition is still unclear and further investigation is needed to lead to a more robust model of the GDL saturation distribution. This work provides a half-cell two-phase transport model for saturation as well as liquid water and gaseous oxygen pressure distributions. This work focuses on the impact of nonzero saturation boundary conditions at the GDL/GC interface, and its impact on GDL two-phase transport. Saturation boundary conditions at this location are determined based on GDL interfacial liquid coverage of water droplets that form as a result of product water that diffuses through the porous medium and blocks oxygen transport paths. The results indicate that nonzero saturation boundary conditions, which are a consequence of GDL/GC liquid droplet coverage, increase cathode saturation by as much as 4% and 12% for low and high current density conditions respectively. It is also shown that cathode saturation dependence on the interfacial liquid coverage fraction α is reduced with an increase in porosity ɛ. As ɛ increases from 0.3 to 0.5, the cathode saturation difference is reduced by 22%. This investigation also evaluated the inclusion and optimization of a microporous layer (MPL) within the half-cell system. It was found that cathode saturation reductions were more significant for increasing MPL porosity than for GDL porosity. The results suggest that its inclusion was able to reduce cathode saturation by up to 90% at the GDL/MPL interface for near zero α values.

Modeling and Fault Diagnosis of a Polymer Electrolyte Fuel Cell Using Electrical Equivalent Analysis

Fuel cell systems are complex systems and a high degree of competence is needed in different areas of knowledge such as thermodynamics, fluid dynamics, electrochemistry, and others, for their comprehension. This paper is a contribution to global modeling and fault diagnosis of these systems. More precisely, the goal of this paper is twofold. First, an electrical equivalent model, which could be used as a unifying approach to fuel cell systems will be resented. Second, a methodology to use the electrical model for fuel cell system diagnosis will be introduced, making special emphasis on fuel cell flooding detection. In order to illustrate the relevance of the proposed approach, experimental validations of the model, and the diagnosis methodology are proposed.

Nonlinear frequency response analysis of PEM fuel cells for diagnosis of dehydration, flooding and CO-poisoning

Membrane dehydration, fuel cell flooding and anode catalyst poisoning by carbon monoxide are diagnosed in a single polymer electrolyte fuel cell (PEMFC) using nonlinear frequency response analysis (NFRA). A sinusoidal perturbation of high amplitude is applied to the fuel cell current and the resulting voltage is analysed using the concept of higher order frequency response functions. It is shown that the linear part of the system response corresponds to classical Electrochemical Impedance Spectra (EIS), which are not sufficient to clearly distinguish between different fuel cell failures. Therefore, the nonlinear behaviour is additionally taken into account in the form of the second order frequency response function. With this, it is possible to distinguish unambiguously between the three analysed PEM fuel cell failures.

Detection of Membrane Drying, Fuel Cell Flooding, and Anode Catalyst Poisoning on PEMFC Stacks by Electrochemical Impedance Spectroscopy

Membrane drying, fuel cell flooding, and anode catalyst poisoning by carbon monoxide are investigated on Hydrogenics production-type proton exchange membrane fuel cell (PEMFC) stacks similar to the stacks used in Hydrogenics HyPM fuel cell power modules. Changes in fuel cell voltage and impedance with time are presented for each type of fault, the fuel cell stacks being controlled in galvanostatic mode. This study shows that these PEMFC stack faults can be differentiated by their impedance responses while fuel cell voltage monitoring alone is insufficient to distinguish between failure types. Membrane drying leads to an increase in the fuel cell impedance magnitude and phase angle at all frequencies studied. Fuel cell flooding leads to an increase in the impedance magnitude at low frequencies and to a decrease in the impedance phase angle at frequencies less than . Anode catalyst poisoning by CO is characterized by an increase in the fuel cell impedance magnitude at frequencies less than a few hundred Hz. For this fault, the impedance phase angle decreases within a large frequency range and is characterized by a minimum value appearing at at moderate current density.

A two dimensional partial flooding model for PEMFC

Proton exchange membrane fuel cells (PEMFCs) have attracted much attention in these years. In PEMFCs, liquid/gas two-phase flow is a common phenomenon, which has great influence on fuel cell performance. However, the liquid water transport process has not been satisfactorily modeled yet. In this work, a two dimensional partial flooding model was developed, in which the pore size distribution of the gas diffusion layer (GDL) is taken into consideration in the explanation of fuel cell flooding for the first time. Liquid water produced is considered to flood a fraction of the GDL hydrophobic pores with diameter greater than the capillary condensation threshold diameter, and the unflooded pores will serve as passageway for gas transportation and the corresponding catalyst area is available for electrochemical reaction. Use this model, it is simple to explain membrane dehydration and electrode flooding. Different operation conditions have been studied with the model and the model polarization curves show reasonable accordance with the experimental results.

Relationship between pressure drop and cell resistance as a diagnostic tool for PEM fuel cells

An increase in pressure drop, particularly on the cathode side of PEM fuel cell, is a reliable indicator of PEM fuel cell flooding, while an increase in cell resistance is a reliable indicator of fuel cell drying. By monitoring both pressure drop and cell resistance in an operational fuel cell stack it was possible to diagnose either flooding or drying conditions inside the stack. These parameters may be used for making decisions on corrective actions.