Cathode Flow Research Articles

Analysis of the effects of the gas diffusion layer properties on the effectiveness of baffled flow channels in improving proton exchange membrane fuel cells performance

Blocking cathode flow channels is employed to improve the performance of a proton exchange membrane fuel cell (PEMFC). Since diffusion resistance toward the catalyst layer plays a key role in this scenario, this work studies the impacts of the gas diffusion layer (GDL) characteristics, including thickness, porosity, permeability, and tortuosity, on the efficacy of baffled channels in enhancing the performance of PEMFCs. A Finite Volume-based code was developed to achieve this objective. Mirroring Immersed Boundary method is utilized to introduce baffles of various shapes and heights into the flow channels. The results indicate increasing the GDL thickness and tortuosity while decreasing its porosity and permeability improves the performance of the baffled channels. For instance, the effectiveness of a baffled channel with a GDL thickness of 0.0004 (m) is 0.304% versus 0.198% in the case of 0.0002 (m). In brief, when diffusion resistance is high, baffled channels are more effective.

Three-dimensional simulation of large-scale proton exchange membrane fuel cell considering the liquid water removal characteristics on the cathode side

A 3D (three-dimensional) numerical simulation model is proposed to investigate the output performance and liquid water distribution of large-scale FF (flow field) considering DMGDZ (“dot matrix” gas distribution zone). The PEMFC (proton exchange membrane fuel cell) is affected by gravity, and the simulation results demonstrate that the PEMFC has the best output performance and water removal effect when the length and width of DM (“dot matrix”) are 1.5 mm and 0.8 mm, respectively. The effect of gravity direction on liquid volume fraction in cathode large-scale FF is not obvious, but liquid volume fraction increases with the increase of the contact angle of GDL (gas diffusion layer) and working current density. The variation of water vapor condensation rate and the MPL (micro-porous layer) contact angle in porous electrodes significantly affects the amount of liquid water in the CFF (cathode flow field), and the PEMFC performance is degraded. Due to the enhancement of convection effect, the waveform channel can effectively remove the liquid water from the cathode channel and slightly strengthen the overall PEMFC performance. According to the results of waveform channel analysis, the comparison of waveform and straight FFs with DMGDZ shows that the waveform FF is more conducive to facilitate the liquid water removal on the cathode side. Simultaneously, the reactant gas distribution is uniform and the output performance is higher.

A Review on the Numerical Studies on the Performance of Proton Exchange Membrane Fuel Cell (PEMFC) Flow Channel Designs for Automotive Applications

Climate change and the major threat it poses to the environment and human lives is the major challenge the world faces today. To overcome this challenge, it is recommended that future automobiles have zero carbon exhaust emissions. Even though battery electric vehicles reduce carbon emissions relative to combustion engines, a carbon footprint still remains in the overall ecosystem unless the battery is powered by renewable energy sources. The proton exchange membrane fuel cell (PEMFC) is an alternate source for automotive mobility which, similar to battery electric vehicles, has zero carbon emissions from its exhaust pipe. Moreover, the typical system level efficiency of a PEMFC is higher than an equivalent internal combustion powertrain. This review article covers the background history, working principles, challenges and applications of PEMFCs for automotive transportation and power generation in industries. Since the performance of a PEMFC is greatly influenced by the design of the anode and cathode flow channels, an in-depth review has been carried out on different types of flow channel designs. This review reveals the importance of flow channel design with respect to uniform gas (reactant) distribution, membrane proton conductivity, water flooding and thermal management. An exhaustive study has been carried out on different types of flow channels, such as parallel, serpentine, interdigitated and bio-inspired, with respect to their performance and applications.

Numerical investigation of the water transport and performance of proton exchange membrane fuel cell with an imitating river flow field

The cathode flow field design of proton exchange membrane fuel cell (PEMFC) could improve water management, avoiding local material failure, increasing oxygen transport and power output. In this study, a novel cathode flow field that imitates river diversion drainage is proposed for settling the issue of channel drainage, under-rib porous layers drainage and balanced water management. A numerical model of the 3D multiphase flow is built for comparative study to reveal the water transport and performance of PEMFC. In the novel flow field, the opened-trap diverts the liquid water of cathode channel to auxiliary channel and increases the gas velocity in cathode channel to drain more water, thereby, 50% liquid water in cathode channel is removed compared to conventional flow field. Micro flume design in auxiliary channel is used to provide the drainage path for under-rib porous layers, meanwhile collected liquid water for convenience to auxiliary channel drainage. The balance water management of novel flow field promotes the downstream drainage and upstream water retention. Effective water management can enhance mass transfer and PEMFC performance. Compares with the conventional flow field, the novel flow field does not increase pressure drop, improves the PEMFC net power and CCL/PEM oxygen concentration by 13.3% and 1.23 times, respectively.

Integrated Effect of Flow Field Misalignment and Gas Diffusion Layer Compression/Intrusion on High Temperature – Polymer Electrolyte Membrane Fuel Cell Performance

Misalignment in the flow field plates of High-Temperature Polymer Electrolyte Membrane Fuel Cell (HT-PEMFC) due to manufacturing tolerances, assembly process, or unavoidable vibration during the cell operation is contemplated its performance and durability. This study investigates the effect of flow field plate misalignment and its concomitant impact with varying the clamping pressures on HT-PEMFC operation. The study considers six degrees of cathode flow field misalignment, varying from 0% to 100% with respect to the anode flow field. Clamping pressures ranging from 1 to 2 MPa are applied to the various cases of misalignment to study their effect on GDL deformation and intrusion into the channels. The structural analysis shows that as the misalignment increases from 0 to 100%, the GDL compression increases from 26.72% to 37.75% for 1 MPa, 40.07% to 56.63% for 1.5 MPa, and 53.43% to 75.51% for 2 MPa, owing to the increase in compression approximately by 41% from their base cases and it is also crucial to note that GDL compression exaggerates at higher clamping pressures. The misalignment results in the sagging of Membrane Electrode Assembly (MEA), and the amplitude of wave nature is proportional to the degree of misalignment and clamping pressure, indicating the misalignment is the sole factor for structural changes. As a result, considerable variance in current distribution and average value is observed, i.e., at operating voltage 0.5 V, the current density drops from 4472.7 to 4264.4, 4420.7 to 4211.8, and 4374.1 to 4161.3 A m−2 from cases 1 to 6 for clamping pressures 1, 1.5, and 2 MPa, respectively, resulting in a 4.7% loss in performance. According to the observations, a misalignment of 60% is tolerable, with minimal performance loss and negligible non-uniformity in cell distributions.

Studies on anode mass composition and cathode flow field design for small-scale to large-scale direct methanol fuel cell stack systems

In this research, the performance studies of a single cell Direct Methanol Fuel Cell with three different mass compositions (20%, 40%, and 60%) of platinum at anode infused in NiTiO3/C and multiple cathode flow fields, such as serpentine, parallel, and sinuous, with 25 cm2 active area. 40% platinum mass composition has been reported with a maximum power density of 24.42 mW/cm2, which is 26.8% and 10.4% higher than the performance observed in 20% and 60% platinum mass composition, respectively, on serpentine flow field. Among the various cathode flow fields, sinuous flow field provided the maximum power density of 28.69 mW/cm2, which is 17.48% and 53.83% higher in performance than that of serpentine and parallel flow fields, respectively. The best-performing catalyst mass composition and flow field, viz., 40% mass composition and sinuous flow field are scaled up to a 100 cm2 active area, and the results showed 16% lower performance compared to a 25 cm2 active area. A three-cell stack is fabricated with the best performing combination with the 100 cm2 active area that delivered a peak power output of 5.8 W, which resulted in 19.4% lower performance than 100 cm2. The stack was tested for stability for 48 h at constant voltage mode and was found that 0.002 W deviation for the entire period.

Optimal design and flow-field pattern selection of proton exchange membrane electrolyzers using artificial intelligence

The design of a proton exchange membrane (PEM) electrolyzer and various hardware options remain key research areas for green hydrogen production technology. We have proposed an approach to select optimum design factors, including a flow-path design for the PEM electrolyzer using a machine learning (ML) technique for the first time. Efficient multiple ML models employing k-nearest neighbors and decision tree regression approaches predict the optimal hydrogen-generating system design for the PEM electrolyzer cell. The proposed ML model was trained and validated using 1062 design data points. The model predicts 17 parameters of the electrolyzer assembly for five input parameters: the hydrogen production rate, electrode area, anode flow area, cathode flow area, and type of cell design (e.g., single or stack). The model shows an absolute mean square error of 0.31 when compared to the experimental results (e.g., potential), which indicates that the model has excellent reliability. Finally, this study presents that the ML model can predict the optimal design of a PEM electrolyzer for commercial-scale hydrogen production rates at 50–3000 mL/min. This research will contribute to reducing the cost and time required to develop future water electrolyzers for hydrogen production.

Enhanced mass transfer and water discharge in a proton exchange membrane fuel cell with a raccoon channel flow field

The cathode flow channel plays an important role in the water management of proton exchange membrane (PEM) fuel cells. In order to improve mass transfer and water management in traditional channels, this paper presents a new wavy flow field to increase the fuel cell performance and overall efficiency. A raccoon channel with various waviness parameters is numerically studied by a three-dimensional two-phase PEM fuel cell model. The electrochemical current-voltage performance results confirm that the PEM fuel cell's performance with the raccoon design is higher than a conventional straight channel at high current densities. The effects of uniform gas distribution, removal of the accumulated water, and sufficient water content in the membrane are crucial factors for improving cell performance. A parametric analysis is also performed by considering the amplitude and wavelength of the raccoon pattern on the fuel cell performance. The results show that the output power improves in the raccoon channel by increasing the amplitude or increasing the wavelength. The raccoon channel's output power with amplitude of 0.5 mm and a wavelength of 2 mm is enhanced by about 20%. The increase of performance in the raccoon channel is significantly higher than in the past reported studies.

A kW-level integrated propulsion system for UAV powered by PEMFC with inclined cathode flow structure design

Open-cathode air-cooling polymer electrolyte membrane fuel cells (PEMFCs) with the lightweight and simple structure are widely used in state-of-the-art UAVs. In this work, a 1 kW-level PEMFC powered propulsion system with an inclined cathode flow structure is developed. The inclined cathode flow structure uses the airflow behind the blade root of the propeller to meet the reaction and cooling requirements of the PEMFC cathode. Such design discards the cathode axial fan in the current commercial PEMFC system and reduces the parasitic power, weight and volume caused by the axial fan. Compared with the current commercial PEMFC powered propulsion system, the specific power of the 1 kW PEMFC system, power-to-weight ratio and thrust-to-weight ratio of the 1 kW integrated propulsion system are increased by 33.0 %, 23.8 %, and 18.3 %, respectively. Besides, the space in the fuselage for the fuel cells and the weight of distribution wiring, as well as the wire loss, is also significantly saved by replacing the axial fan with proposed inclined cathode flow structure.

A study into Proton Exchange Membrane Fuel Cell power and voltage prediction using Artificial Neural Network

Polymer Electrolyte Membrane fuel cell (PEMFC) uses hydrogen as fuel to generate electricity and by-product water at relatively low operating temperatures, which is environmentally friendly. Since PEMFC performance characteristics are inherently nonlinear and related, predicting the best performance for the different operating conditions is essential to improve the system’s efficiency. Thus, modeling using artificial neural networks (ANN) to predict its performance can significantly improve the capabilities of handling multi-variable nonlinear performance of the PEMFC. This paper predicts the electrical performance of a PEMFC stack under various operating conditions. The four input terms for the 5 W PEMFC include anode and cathode pressures and flow rates. The model performances are based on ANN using two different learning algorithms to estimate the stack voltage and power. The models have shown consistently to be comparable to the experimental data. All models with at least five hidden neurons have coefficients of determination of 0.95 or higher. Meanwhile, the PEMFC voltage and power models have mean squared errors of less than 1 × 10−3 V and 1 × 10−3 W, respectively. Therefore, the model results demonstrate the potential use of ANN into the implementation of such models to predict the steady state behavior of the PEMFC system (not limited to polarization curves) for different operating conditions and help in the optimization process for achieving the best performance of the system.

Comparison of Serpentine and Interdigitated Monopolar Plates on the Performance of an Anion Exchange Membrane Fuel Cell By CFD

The continuous energy demand and the growing population have focussed the scientific research on developing alternative energy sources or green fuels.The anion exchange membrane fuel cell (AEMFC) arises as an excellent alternative because of its low-cost electrocatalyst used at the cathode, energy production, and no pollutants emissions to the environment. Nowadays, several studies have been conducted to improve the performance of the AEMFC modifying membrane materials, types of gas diffusion layers (GDL), and catalysts, among other cell components.However, the design of the flow channels by changing plate topologies and materials is still under development. About flow channels topologies, conventional geometries array (pin, straight, parallel, and serpentine) flow fields lead the flow in the direction parallel to the electrode surface, and the reactive gas flow towards the catalyst layer (CL) mainly by molecular diffusion. On the other hand, interdigitated flow fields provide convection velocity normal to the CL and forced convection flow in GDL for better mass transfer. The interdigitated flow fields could prevent water flooding and improve high current density operations performance.These flow fields have been tested in proton exchange membrane fuel cells (PEMFC) with excellent results at low current densities. Nonetheless, there is an essential balance and management of water in an AEMFC. It presents simultaneous production and consumption of water in anode and cathode, respectively, where the production is twice the consumption.Poor water management could provoke anode flooding or membrane drying. These scenarios are undesirable due to mass transport limitations, membrane polymer degradation, and cathodic channels flow can be flooded. Therefore, an appropriate design of flow field that allows the correct water balance on AEMFC is needed for optimal performance. This research deals with the computational fluid dynamic (CFD) comparison of serpentine and interdigitated flow fields on the performance of an AEMFC. For the development of this model, the Navier-Stokes and Brinkmann equations were implemented for momentum transfer. In addition, the average mixture model represents the transport of chemical species, and the Butler-Volmer equation denotes the electrochemical reaction at the CL; water balance is analyzed at low and high current densities to evaluate the scenarios above mention.Preliminary results indicate that a serpentine design is functional at the anode due to the water management is favored. An interdigitated flow field is implemented at the cathode to improve the distribution of the reactants from channels until the CL.

Effects of MPL Pore Size Distribution on Components of Oxygen Transport Resistance Increased Due to Water Accumulation in a PEFC

To increase the power output of PEFC, management of generated water is extremely important. A gas diffusion layer (GDL) with a microporous layer (MPL) on the cathode side is thought to play important roles in drainage of product water and optimizing oxygen transport, but the details of the mechanism have not been elucidated. In this study, to reveal the water and oxygen transport phenomena, the components of oxygen transport resistance were evaluated using the limiting current analysis (1) for two types of MPL with different pore size distributions. Further, the water distributions in the cathode side MPL and catalyst layer (CL) were observed by a freezing method and a cryo-SEM (2). The active area of the cell used in this study was 1.8 cm2 (0.9 cm × 2.0 cm). The anode and cathode flow fields were parallel straight type with 1.0 mm wide ribs and channels. The anode side was supplied with hydrogen, and the cathode side was supplied with a mixed gas of oxygen and nitrogen. The gas flow rates were 500 sccm for the anode and 4000 sccm for the cathode. The relative humidity of the supplied gases was 90%. Experiments were conducted under two different cell temperature, 30°C (low temperature condition) and 80°C (high temperature condition). The catalyst coated membrane was produced by Japan Gore (PRIMEA). We used two types of MPL with different pore size distributions for the cathode GDL: MPLs with one peak (conventional type) and with two peaks. The MPLs are called MPL-1 and MPL-2, respectively. For the anode side, a GDL with an MPL (SGL, 28 BC) was used. This study used the limiting current analysis developed by the authors (1). The developed method extended the conventional method to the separation under flooded conditions, considering vapor transport and water distribution. Inside the CL, it was assumed that the water production rate dominates the water accumulation, which is proportional to current density. Outside the CL, it was assumed that the product of total pressure and current density determines the water accumulation (1). The experiments were conducted with different back pressures (110 kPa, 140 kPa, 180 kPa) and different oxygen concentrations (1%, 2%, 4%, 6%, 8%, 12%, 15%, 18%, 21%) for the cathode side. Figure 1 shows the total oxygen transport resistances at 110 kPa. There is a significant difference in the tendencies of the total oxygen transport resistance between the MPL-1 and the MPL-2 under the low temperature condition, while the tendencies are similar under the high temperature condition. This suggests that the effects of water accumulated in the cell are larger at lower temperature. Figure 2 shows the results separating the total oxygen transport resistance into two resistances. The I Lim is the limiting current density. The R P and R NP are the pressure-dependent and -independent oxygen transport resistances. These correspond to the oxygen transport resistances outside and inside the CL. Under the low temperature condition, the pressure-dependent oxygen transport resistances (corresponding to those outside the CL) are different between the MPL-1 and the MPL-2. The pressure-independent resistances (corresponding to those inside the CL) are similar. These mean that the smaller total oxygen transport resistances with the MPL-2 in Figure 1 are caused mainly by the smaller resistance outside the CL. Before the separation, we predicted that the increase in the total oxygen transport resistance is suppressed by the MPL-2 due to enhanced drainage of product water from the CL. However, Figures 2(a) and (c) revealed that the R P of the MPL-2 becomes smaller than that of the MPL-1 rather than the R NP. This may be considered because the larger pores in the MPL-2 form drainage pathway for product water at the low temperature condition, which significantly contributes to increasing the oxygen transport pathway through the smaller pores. As expected from Figure 1, there is no significant difference in the R P and the R NP between two types of the MPL under the high temperature condition (Figures 2(b) and (d)). The water distribution in the vicinity of MPL-2 was observed after discontinuing operation at 2.0 A/cm2 just before the limiting current condition. The experiment was conducted with 30°C, 180 kPa back pressure, and 21% oxygen concentration. Cryo-SEM images showed that there was ice at the MPL/CL interfaces. Additionally, ice crystals were observed at the larger pores in the MPL-2, supporting the above consideration, the drainage pathway for product water through the larger pores.Reference (1) Y. Iizuka, et al., ECS Transactions, 104(8), 83-92 (2021). (2) Y. Aoyama, et al., Electrochem. Commun., 41, 72-75 (2014). Figure 1

Experimental investigation and decoupling of voltage losses distribution in proton exchange membrane fuel cells with a large active area

Understanding the local operating state and voltage loss distributions are of great importance to guide the performance improvement of proton exchange membrane fuel cells (PEMFCs). Especially when the active area is large, the uneven electrochemical reaction becomes more severe. However, the current research does not enable the simultaneous monitoring of the multiple operating states and decoupling of the voltage losses in the fuel cell. In this study, a method is established that can obtain the distribution of activation polarization, ohmic loss, and concentration polarization by analyzing the measured data of temperature, humidity, current density, and high-frequency resistance (HFR), which are obtained inside a 320 cm2 and 3 kW level fuel cell stack by using the multilayer printed circuit board (PCB) technology with designed isolation segments. The effects of humidity, operating temperature, and current density on the distributions of output voltage and voltage losses are discussed. Results show that the potential distribution on the surface of membrane exchange assembly (MEA) isn’t uniform in the large active area. The activation polarization gradually increases in the direction of coolant flow and the direction of the cathode flow and the ohmic loss and concentration polarization have opposite distribution characteristics. In addition, when the humidity rises to full humidity, the inhomogeneity of ohmic loss distribution becomes higher with three local increased areas of 20 mV and one decreased area of −20 mV. Higher temperatures can significantly reduce the flooding near the outlet of the active area. When the current density increases, the inhomogeneity of the ohmic loss distribution increases, and the concentration polarization near the cathode outlet of the active area become more severe.

Multiple effects of non-uniform channel width along the cathode flow direction based on a single PEM fuel cell: An experimental investigation

Proton exchange membrane (PEM) fuel cell is considered to be one of the promising alternatives to conventional engines in the future as on-board vehicle energy conversion device. In this paper, three single PEM fuel cells with different cathode flow field plates (FFPs), which vary from each other on the channel width along the cathode flow direction, are assembled. Polarization and power density curves, electrochemical impedance spectroscopy (EIS) fitting results are utilized to evaluate the output performance. Moreover, the economic characteristic of three single cells is calculated based on the assumption of parasitic pumping power generated by air compressor. Finally, the durability of three single cells is assessed based on comparison of electrochemical surface area (ECSA) obtained from analysis of cyclic voltammetry (CV) method. The comprehensive experimental results reveal that cell 0.8-1.0-1.2 exhibits better performance under high RH conditions and cell 1.0-1.0-1.0 is more favorable under a low RH condition. The mechanism behind the phenomenon of performance variation is analyzed and attributed to the switching of dominating factor from two-phase flow velocity to spatial availability degree under various conditions of RH.

Optimal design of a cathode flow field with a new arrangement of baffle plates for a high clean power generation of a polymer electrolyte membrane fuel cell

Polymer electrolyte membrane fuel cell is a clean and promising energy device in the near future; the present work proposes newly designed baffle plates that feature unequal height and space distance arrangements in the cathode flow field of fuel cells. Using a three dimensions multiphase fuel cell model, the effects of various newly designed baffle plates with different numbers, unequal height and space distance arrangements on the oxygen diffusion, water transport behavior and performance of a fuel cell are comprehensively evaluated. The results show that the baffle plates significantly promote oxygen diffusion and water elimination in fuel cells compared to the regular straight flow field, especially in the regions around the baffle plates due to the convection effect. A gradually increasing height and a decreasing space distance between the baffle plates can further relieve water flooding and oxygen starvation in the porous electrodes downstream of the channel under high current densities; hence, they significantly improve the maximum power density by 9.67% compared to the regular flow field without baffle plates. In addition, the optimal newly designed baffle plate flow field pattern exhibits uniform physical quantities with a relatively low-pressure loss along the flow channel, which reduces the pumping power to supply reactants and favors the energy efficiency of fuel cells.

Three-dimensional multi-phase simulation of different flow fields with cooling channel in proton exchange membrane fuel cell

The overall performance of PEMFC (proton exchange membrane fuel cell) is affected by the flow field structure, especially the cathode flow field design can effectively solve the uneven distribution of gas concentration in the traditional flow channel and the cathode flooding phenomenon. In order to solve the above problems, a PEMFC single cell model with waveform staggered flow field of cooling flow field and small cathode channel was established in this study. Three-dimensional (3D) multi-phase CFD (computational fluid dynamics) simulation method is used to compare with gas concentration, liquid water distribution, pressure drop, and net power density of three different cases, and the influence of different cooling velocity on the temperature of cooling flow field is considered. The results show that the overall performance of the proposed flow field is the best, in which the maximum current density is 1.391 A⋅cm−2 and increases by 14.9%. The cathode and anode waveform staggered flow field makes the proton exchange membrane (PEM) water distribution more uniform, at the same time, the small size of the cathode flow channel facilitates the discharge of heat, and the convective heat transfer effect is enhanced. The electrochemical reaction rate is fast, which accelerates the temperature reduction in the fuel cell under the action of the cooling flow field, and the temperature uniformity of the cooling flow field is better. In addition, net power density is improved by 39.7%, and the output performance is significantly improved.

Design and experimental verification of model-free adaptive sliding controller for air supply system of PEMFCs

The control performance of cathode flow rate and pressure directly determines the efficiency and service life of proton exchange membrane fuel cell vehicles. The mechanism modeling methods are difficult to accurately describe the parameter perturbations and model uncertainties, which leads to the deterioration of the control performance. For this reason, it is of great practical significance to study control methods independent of the mathematical model of the cathode flow rate. The paper investigates a model-free adaptive discrete sliding control strategy for cathode flow rate. First, the nonparametric dynamic linearization technology is used to obtain a cathode flow rate dynamic linearization model, which can realize the adaptability and robustness to internal parameter perturbations and external disturbances of the controlled system; Second, an adaptive second-order discrete sliding mode controller based on the novel data-driven sliding surface is designed to improve the transient quality with smaller steady state errors, and the stability and robustness are theoretically guaranteed. Third, given that the cathode pressure mechanism is described clearly and simply, the backstepping method is applied to control the cathode pressure , and the robustness is proved in the framework of input-to-state stability theory. Finally, the simulation results are given to verify the effectiveness and robustness of the proposed method compared to the benchmark controllers, and the experimental results show that the proposed method can achieve accurate tracking control of cathode flow rate and pressure with excellent response speed.

Modeling of a novel cathode flow field design with optimized sub-channels to improve drainage for proton exchange membrane fuel cells

Water management is the primary factor affecting the output performance of proton exchange membrane fuel cells. Aiming to effectively deal with the flooding problem during the cell operation in a cathode flow field, this paper proposes a novel sub-channel design based on a wave-like flow field. The effects of sub-channel wall properties and channel geometry on the water removal capacity of the sub-channel are numerically evaluated by using the volume of fluid (VOF) method. Verification experiments are carried out to observe the water dynamics from droplets accumulation to detachment. The results reveal that the sub-channel achieves drainage performance by enhancing the gas pressure difference to overcome the wall adhesion. A wall contact angle of not less than 110° and an included angle to the main channel of not more than 60° are the prerequisites for the effective water removal of the sub-channel. The optimal design of the sub-channel is obtained to achieve better drainage performance. In addition, it is found that the effects of the sub-channel on water droplets will be weakened when the main channel period is densified to 1.5 mm or less, which is usually adopted to improve the mass transfer capacity under the ribs.

Improvement of the three-dimensional fine-mesh flow field of proton exchange membrane fuel cell (PEMFC) using CFD modeling, artificial neural network and genetic algorithm

This study proposes a systematic methodology for improving PEMFC's performance combining computational fluid dynamic (CFD), artificial neural network (ANN), and intelligent optimization algorithms. Firstly, a three-dimensional (3-D) multiphase PEMFC CFD model with 3-D fine-mesh flow field is developed. Then the key structural features of the fine-mesh flow field are extracted as optimization decision variables, and the sampling points are selected by using the Latin hypercube sampling (LHS) experimental method. The power density and oxygen uniformity index of sampling points are calculated by CFD modeling to form the database, which is used to train the artificial neural network (ANN) surrogate model. Finally, the single-objective optimization (SOO) and multi-objective optimization (MOO) are implemented by using genetic algorithm (GA) and non-dominated sorting genetic algorithm (NSGA-II), respectively. It was found that using trained ANN surrogate models can get a high prediction precision. The maximum power density of SOO is increased by 7.546% than that of base case and is 0.562% larger than that of MOO case. However, the overall pressure drop in cathode flow field of SOO case is greater than that of MOO case and the base case. Furthermore, the oxygen concentration, the oxygen uniformity index and the water removal capacity of MOO case are better than that of SOO case. It is recommended that the improved flow field structure optimized by MOO is more beneficial to improve the overall performance of PEMFC.

Effect of cathode operation parameters on the performance of proton exchange membrane fuel cell with curved wing vortex generator by response surface method

AbstractWith the increasing popularity of fuel cells, improving their power density and the fuel cell system efficiency has become very topical. This study used the curved wing vortex generator to generate a secondary flow in the cathode flow channel to improve the performance of the proton exchange membrane fuel cell (PEMFC). The curved wing's structure and arrangement effects on the performance of fuel cells were numerically simulated. Next, to summarize the combined effects of cathode operating conditions on the performance of PEMFC, this study used the response surface method to assess the influence of operating conditions variables on the performance target of PEMFC with curved wings. The combined effects of cathode operating conditions, namely temperature, pressure, reactant stoichiometry, and relative humidity, on the system efficiency and power density of the fuel cell system were investigated. The predictive correlations between these variables were also fitted. The installation of curved wings promoted the diffusion of reactants, as well as improved the uniformity of temperature distribution and the discharge of liquid water in the fuel cell, enhancing its overall performance. Among the four operating parameters under study, the most significant effect on the fuel cell power density was provided by the temperature, followed by pressure, humidity, and reactant stoichiometry. The fuel cell efficiency was the most significantly improved by increasing the relative humidity, while temperature increase had the second‐best impact, followed by pressure, and reactant stoichiometry.