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As a recently developed flow field for the bipolar plate of a proton exchange membrane fuel cell, the wave flow channel has demonstrated several advantages in enhancing the gas supply within the channel. However, its unique shape poses challenges in effective drainage, as liquid water is prone to impinge on the side wall. In this study, to analyze water transmission performance of the wave channel, based on a coupled level set and volume of fluid method, a 3D two-phase water transport model of the wave channel was established, and the flow characteristics data of liquid water in the wave channel under different working conditions were calculated. The dynamic behavior of liquid water in the wave channel with initial forms of the liquid drop, liquid film, and liquid column were investigated, respectively. The results indicated that different initial forms of liquid water move through a wave channel all in the form of a membrane flow. When the initial form of liquid water resembles a liquid column, it exhibits the highest velocity of movement within a wave channel compared with the initial forms of liquid droplets and liquid film, assuming an equivalent volume. Further, the speed of liquid water movement increased with the volume of liquid water and the inlet gas velocity. Additionally, the contact angle of a gas diffusion layer surface exerts a substantial influence on water volume and slightly influences the move speed of liquid water. [ABSTRACT FROM AUTHOR]

Unreasonable cooling channel arrangement and cooling water flow distribution in proton exchange membrane fuel cell will cause large heat loss and low efficiency. Therefore, to improve performance of fuel cell, parallel serpentine channel (Type-C channel) and composite channel (Type-D channel) are proposed in this article, and compared with traditional parallel channel (Type-A channel) and traditional serpentine channel (Type-B channel), temperature standard deviation is proposed, advantages of designed channel are evaluated by comprehensively comparing the water content distribution, temperature gradient and distribution characteristics of cooling channels and proton exchange membrane. Results show when cooling water flow rate increases from 0.2 to 0.8m/s, pressure drop of proposed Type-C and D channels are much smaller than that of Type-B channels. In addition, temperature distribution of Type-C is more uniform than that of Type-A and Type-D channels. Considering above factors, Type-C channel provides a good reference for the subsequent channel design and development direction. [ABSTRACT FROM AUTHOR]

Water management plays a crucial role in the performance of proton exchange membrane fuel cells (PEMFC). In this paper, to speed up the removal of water in the flow channel, the microprotrusions are fabricated on the flow channel surface by using laser remelting, and the surface is then sprayed with nanohydrophobic materials. The contact angle of the surface after spraying the hydrophobic material and laser processing increases from 115° to 132° when only the hydrophobic material is sprayed. Through visualization experiments, the movements of droplets in the smooth and microstructured flow channel are compared at different gas inlet pressures and different water inlet mass flows. The results show that the contact form of droplets with smooth surface is a solid-liquid contact, whereas there is also a liquid-gas contact with a microstructured surface. The main movement form of droplets in the smooth flow channel is sliding, whereas in the microstructured flow channel it is rolling. Under different experimental conditions, the movement speed of droplets in the microstructured flow channel is faster than that of the smooth flow channel, which indicates that the flow channel with microprotrusions has a better drag reduction performance. As the gas inlet pressure increases, the initial diameter of the droplet gradually decreased, and the velocity of the droplet increases. The water inlet mass flow has little effect on the oscillation amplitude of the droplets in the smooth flow channel, whereas in the microstructured flow channel, the droplet oscillation amplitude increases with the increase of the water inlet velocity. This work provides a new choice for the design of a flow channel. [ABSTRACT FROM AUTHOR]

Efficient water management in the gas diffusion layer (GDL) facilitates the efficient and stable operation of proton exchange membrane fuel cells (PEMFCs). GDL perforation is an effective method for fuel cell water management. The stochastic reconstruction of multiperforated GDL structure with different perforation diameters, perforation spacings, and array modes was established to simulate the transport process of water in multiperforated GDLs. The multiple relaxation time lattice Boltzmann method (MRT LBM) was used to simulate the water transport process in perforated GDLs. The result showed that the diameter of the perforation greatly influenced the water transport process; as the perforation diameter increased, the height of the water breakthrough rose, and water saturation significantly increased. When the perforation spacing was extremely small, the impact area of perforation spacing overlapped, and the area of the water breakthrough–prone region decreased, thus reducing water transportation efficiency. The array method had little effect on water saturation and water breakthrough height. These findings show that array parameters can influence the behavior of the water transport process in perforated GDLs and have significant implications for the application of perforation methods in GDL water management. [ABSTRACT FROM AUTHOR]

Alkaline fuel cells can permit the adoption of platinum group metal‐free (PGM‐free) catalysts and cheap bipolar plates, thus further lowering the cost. With the exploration of PGM‐free hydrogen oxidation reaction (HOR) catalysts, nickel‐based compounds have been considered as the most promising HOR catalysts in alkali. Here we report an interfacial engineering through the formation of nickel‐vanadium oxide (Ni/V2O3) heterostructures to activate Ni for efficient HOR catalysis in alkali. The strong electron transfer from Ni to V2O3 could modulate the electronic structure of Ni sites. The optimal Ni/V2O3 catalyst exhibits a high intrinsic activity of 0.038 mA cm−2 and outstanding stability. Experimental and theoretical studies reveal that Ni/V2O3 interface as the active sites can enable to optimize the hydrogen and hydroxyl bindings, as well as protect metallic Ni from extensive oxidation, thus achieving the notable activity and durability. [ABSTRACT FROM AUTHOR]

Summary: A 3D model of a proton exchange membrane fuel cell (PEMFC) with a laser‐perforated gas diffusion layer (GDL) is numerically established. The primary aim of the study is to determine whether the laser‐perforated GDL can enhance the mass transport efficiency and performance of PEMFC. Laser‐perforated GDL of the PEMFC flow channel can promote cathode reactant water accumulation in the perforation and accelerate the discharge of reactant water. Additionally, the influence of laser‐perforated parameters on the mass transport efficiency and performance of PEMFC is compared. The results showed that, as compared to a typical GDL, the diameter of the laser‐perforated GDL mainly affects the water mass percentage and oxygen mass percentage at the cathode outlet. As the diameter grows from 50 to 150 μm, the water mass percentage decreases, while the mass percentage of oxygen increases and improves the performance. As depth grows, the water mass percentage in the laser‐perforated GDL shows a decreasing trend. However, when the low voltage is in the range of 0.4 to 0.6 V, the oxygen mass percentage shows an increasing trend. Different spacing of laser‐perforated GDL primarily affects the water mass percentage and oxygen mass percentage of the zx plane and GDL surface, but the effect on performance is not considerable. The water mass percentage rises in proportion to the spacing. Laser perforated GDL with different shape parameters can improve cell performance to different degrees. When the laser‐perforated GDL diameter is 150 μm, depth is 350 μm, and spacing is 150 μm, the water mass percentage is the most minor (average of water mass percentage less than 0.21), and the fuel cell provides optimal performance. [ABSTRACT FROM AUTHOR]

• A pore scale model for cold start of catalyst layer is established. • It integrates pore-scale species transport, heat transfer, multiphase flow model. • The model is validated by theoretical analysis results. • Influence of released gaseous water particle and structure are studied. To explore multiphase reactive flow and heat transfer process during direct cold start in catalyst layer of proton exchange membrane fuel cell, a pore scale model was established. Effects of released gaseous water particle number, platinum volume fraction, ionomer thickness, and carbon support diameter were studied. The results reveal that due to obstruction of ice at bottom, oxygen cannot fully enter the bottom. After motion of solid ice is completely melted, the obstruction of the bottom on oxygen transport weakens, and oxygen gradually enters the bottom of the catalyst layer. As the number of gaseous water particles increases, the frost layer becomes thicker, and the resistance of the frost layer to oxygen diffusion becomes more significant. The increase in platinum particles elevates temperature within the catalyst layer, accelerating melting of solid ice within the catalyst layer. The carbon support diameter only has an effect on the intermediate concentration region. When the carbon support diameter is 26 nm, more oxygen enters the ionomer due to the weakened obstruction of the frost layer. Increasing the carbon support diameter lowers the temperature within the catalyst layer. [ABSTRACT FROM AUTHOR]

At temperatures below 0 °C, reactive multiphase flow in the gas diffusion layer (GDL) of a fuel cell can interfere with the cell's cold-start performance. A good model is still lacking for addressing this problem. In this study, a novel multi-physics pore-scale model for multiphase reactive flow and heat transfer is proposed. Effects of micro-porous layer crack width, crack spacing, porosity, and an initial ice droplet are studied. The results show that as the electrochemical reaction progresses, the bottom temperature gradually increases and heat is conducted into the GDL. Increasing the pore width results in an increase in the volume of liquid water in the GDL. At a spacing of 75 μm, carbon fibers have only a small effect on the movement of liquid water. With an increase in porosity, the electrochemical performance improves. When ice droplets are present in the flow channels of liquid water, the liquid water will merge with the melted ice droplets due to surface tension, thereby accelerating the flow. When an ice droplet is located on the sides of the flow channel and near fewer carbon fibers, the liquid water changes its direction of movement after merging with the melted ice droplet. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional model was established using the lattice Boltzmann method (LBM) to study the internal ice melting process of the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC). The single-point second-order curved boundary condition was adopted. The effects of GDL carbon fiber number, growth slope of the number of carbon fibers and carbon fiber diameter on ice melting were studied. The results were revealed that the temperature in the middle and lower part of the gradient distribution GDL is significantly higher than that of the no-gradient GDL. With the increase of the growth slope of the number of carbon fiber, the temperature and melting rate gradually increase, and the position of the solid-liquid interface gradually decreases. The decrease in the number of carbon fibers has a similar effect as the increase in the growth slope of the number of carbon fibers. In addition, as the diameter of the carbon fiber increases, the position of the solid-liquid interface gradually decreases first and then increases. • The gradient GDL ice melting model was developed. • The LBM model was used to investigate the ice-melting process in GDL. • Effects of growth slopes of carbon fibers on the melting of the GDL ice. • Effect of different numbers of carbon fibers on the melting of the GDL ice. • Effect of different carbon fiber diameters on the melting of the GDL ice. [ABSTRACT FROM AUTHOR]

Summary: To predict water behavior accurately and explore water droplet impact on a proton exchange membrane fuel cell channel surface, a novel dynamic contact angle model was introduced. A two‐dimensional model of water droplet impact was established via the lattice Boltzmann method, and it was validated. Influences of equilibrium contact angle, sliding angle, lateral velocity, and longitudinal velocity were all explored. The results reveal that when droplet impact the channel surface, it appears in three states: spreading, rebounding, and moving. The model can capture the water‐air interface accurately. When the droplet impacts a hydrophobic wall, the droplet jumps up after rebounding, and eventually returns to its original shape. When the equilibrium contact angle increases, the spread factor gradually decreases, and the droplet keeps moving on the wall. With the increase of sliding angle, the spread factor gradually decreases, and the height of the droplet rebound also increases. The lateral velocity can cause the front end of the droplet to be elongated. As longitudinal velocity increases, spread factor increases, and relative distance gradually decreases. Novelty Statement: A novel dynamic contact angle model is introduced.A two‐dimensional model of water droplet impact is established.Influences of equilibrium contact angle, sliding angle, and velocity are explored.The model can capture the water‐air interface accurately. [ABSTRACT FROM AUTHOR]

• The ultrafine L 1 1 -PtCu intermetallic compound nanoparticles were synthesized. • They showed high resistance to phosphate poisoning. • It exhibits a superior peak power density of 800.5 mW cm−2 in 160℃ H 2 -O 2 HT-PEMFC. In high-temperature proton exchange membrane fuel cells (HT-PEMFC), phosphate anions act as a poisonous 'spectator species', binding strongly to the Pt surface through Pt O bonds similarly to O 2. This blocks the Pt active sites, resulting in slow ORR kinetics. Herein, we synthesized ultrafine L 1 1 -PtCu intermetallic compound nanoparticles (O-PtCu/S-C) loaded on an S-doped carbon support with an average size of about 3 nm through wet impregnation followed by hydrogen annealing, which showed high resistance to phosphate poisoning. The introduction of S notably improved the metal-support interaction and prevented particle growth during annealing, which is beneficial for the uniform distribution of nanoparticles and prevents detachment and agglomeration during ADT. The pronounced Cu-Pt electronic interaction in O-PtCu/S-C induced electron transfer from Cu to Pt, which effectively modified the electronic structure of Pt and weakened the adsorption energy of phosphate anions on the catalyst surface. In addition, the phosphate poisoning test results from both room temperature RDE and high-temperature RDE demonstrate that O-PtCu/S-C possesses excellent phosphate tolerance, superior ORR activity, and remarkable stability. It exhibits a superior peak power density of 800.5 mW cm−2 in 160°C H 2 -O 2 HT-PEMFC with Pt loading of 0.5 mg cm−2. This research offers a novel approach to designing phosphate-resistant electrocatalysts for HT-PEMFC. [ABSTRACT FROM AUTHOR]

Summary: To investigate and optimize the water‐gas transport performance of microporous gas diffusion layer (GDL) flow channel, the simulation of computational fluid dynamics (CFD) is implemented with the volume of fluid method (VOF). The impact of microporous GDL flow channel with different depths, radiuses, and spacings on water transport and water removal is discussed. With the increase of microporous depth, the droplet movement velocity gradually accelerates. When the droplet returns to GDL, the peak of drag reduction rate increases first and then decreases and the peak of pressure drop tends to rise. The micropore radius has a few effects on droplet movement velocity, but it has obvious effects on the velocity field, pressure drop, and drag reduction rate. The influence of the spacing on the water droplet movement velocity and pressure drop is inconspicuous, but it has certain influence on drag reduction rate of the droplet returning to GDL and the microporous GDL velocity field. When the depth is 50 μm, radius is 50 μm, and spacing is 200 μm, the flow channel has a better drag reduction performance. The work in this paper provides a guide for the design of the microporous GDL for drag reduction and water removal. Highlights: The impact of microporous GDL flow channel with different depths, radiuses, and spacings on water transport and water removal is discussed.The resistance can be reduced, and water removal can be accelerated greatly in the perforated GDL.When the micropore depth is 50 μm, radius is 50 μm, and spacing is 200 μm, the flow channel has a better drag reduction performance. [ABSTRACT FROM AUTHOR]

In this study, the effects of vane channel parameters on the flow field and separator performance are investigated based on a vane type gas-water separator for a PEMFC (proton exchange membrane fuel cell) system. The Eulerian-Eulerian model combines with the Multi-Fluid VOF (volume of fluid) modeling approach is used to comprehensively investigate the gas-liquid two-phase flow field and performance indexes in the separator, and the sensitivity analysis of the structural parameters is carried out. The results show that the pressure drop of the separator gradually increases with the increase of the vane contraction ratio, while the separation efficiency has a tendency to increase and then decrease with the increase of the vane incidence angle. For the separation efficiency, the most beneficial structural variant results in an increase of 11.63%, while for the pressure drop, almost all structural variants result in a reduction of the pressure drop from the standard structure with a maximum reduction of 36.58%. By analyzing the phase distribution, pressure field and velocity distribution of different structures, it can be obtained that the main factors affecting the performance of the separator are the extreme values of tangential velocity inside the separator and the symmetry of velocity distribution in the internal flow field. The results presented in this study can provide a reference for the PEMFC gas-water separator. [Display omitted] • A numerical simulation coupling Eulerian method with Multi-Fluid VOF model is applied. • A new gas-water separator structure for PEMFC system is investigated in detail. • Vane incidence angle and vane contraction ratio have a large effect on separator performance. • Sensitivity analysis of vane structural parameters to find out their priorities. [ABSTRACT FROM AUTHOR]

The purging process has implications for the commercial application of proton exchange membrane fuel cells. Transport phenomena are essential to understand purging process and provide solutions to the purging problem. In this review, experimental researches are reviewed. Analytical and numerical models and their results are also discussed. Transport phenomena associated with the purging process include phase transitions and transport. This paper focuses are also on strategies used to optimize the purge process. These strategies include component design and purge strategy control. The results show that all effective strategies for dealing with the purging problem require an understanding of the transport mechanism. It is also suggested that future designs should focus on the directional flow of liquid water. Future models of this problem should also emphasize water evaporation-condensation phase transitions and transport. More advanced experimental methods are needed to validate numerical models. • Gas purge of PEMFCs was discussed. • Experimental and Numerical approaches were presented. • Mass transfer characteristics of gas purge were analyzed. • Design and optimization of components and control strategy were summarized. • Future research directions on gas purge of PEMFCs were presented. [ABSTRACT FROM AUTHOR]

To explore ice-melting process in a perforated gas diffusion layer and an effective and efficient GDL structure to enhance ice melting performance, a three-dimensional ice-melting model was established via lattice Boltzmann method based on enthalpy. The modified curved boundary condition was used in the model to consider complex carbon fiber surface. The influence of the hole shape parameters on ice melting was investigated. The main finding of the work is that the ice in a perforated gas diffusion layer can be melted faster than that in a conventional gas diffusion layer, which means that perforated gas diffusion layer has better ice melting ability. The width mainly influences the enhancement area of heat transfer. When the Fourier number is 0.1, as the width increases, the melting rate increases from 0.55 to 0.62. If the hole depth is larger than 0.5 times the thickness of the gas diffusion layer, the hole can act to enhance the ice melting. The maximum ice melting rate at a Fourier number of 0.1 is only 0.59. The increasing number of holes makes the temperature more evenly distributed. When the Fourier number is 0.1, as the number increases, the ice melting rate increases from 0.55 to 0.62. [ABSTRACT FROM AUTHOR]

• A three-dimensional numerical simulation is carried out via electrochemical model. • The existence of the elliptical groove allows more water to be removed from GDL. • As the depth increases, water content decreases, while oxygen content increases. • The radius has an influence on low mass fraction area and the water mass fraction. • The width mainly affects the low water mass fraction area near the oxygen inlet. • As the spacing increases, the water mass fraction in the xy plane decreases. A new elliptical groove gas diffusion layer (GDL) using a three-dimensional model is proposed to improve the transport properties of the GDL of a proton exchange membrane fuel cell (PEMFC). The effects of different shape parameters on water diffusion and transport behavior are investigated. The results revealed that compared with the traditional GDL, the presence of an elliptical groove greatly accelerates the flow rate of the reactants and products. Also, when the depth increases from 100 to 300 μm, the water mass fraction of the GDL decreases, whereas the oxygen mass fraction increases. As the radius increases, the low mass fraction area in GDL gradually increases, and the water mass fraction of the flow channel increases. As the spacing increases, the water mass fraction of the GDL in the xy-plane decreases, and the oxygen mass fraction increases. When the depth increases, the transport properties of the fuel cell are improved. All shape parameters contribute to the mean water mass fraction. The water mass fraction is the lowest when depth is 350 μm, radius is 350 μm, width is 200 μm, and spacing is 50 μm. [ABSTRACT FROM AUTHOR]

Hydrogen production by methanol steam reforming is one of the best choices for portable proton exchange membrane fuel cells (PEMFC). The channel is a dominant role in hydrogen production performance as the main reaction site. In this study, a fractal network channel architecture was designed and a three-dimensional (3D) numerical simulation was conducted in accordance with the Uniform Latin Hypercube design simulation scheme to explore the influence mechanism of branch grade (m), branch angle (θ), branch length ratio (α) and branch width ratio (β) on hydrogen production performance. Furthermore, four factors (m , θ , α , β) for the hydrogen production performance of fractal network channel were optimized by combining response surface method and non dominated sorting genetic algorithm II. The results showed that the hydrogen production performance is most sensitive to changes in β with the growth of the fractal network, followed by m , α , and θ. And the optimum parameter combination in terms of yield hydrogen is m of 3, θ of 134°, α of 0.88, and β of 0.85. The mechanism of the influence of fractal network structure parameters on the methanol reforming reaction as revealed in this study may provide a workable guideline for effective heat and mass transfer in new fractal reaction channel. [Display omitted] • A fractal network was developed with constant reaction area and initial width. • The influence mechanism is a trade-off between fluid velocity and channel length. • Combining RSM and NSGA-Ⅱ algorithms to optimize the structural parameters. • Hydrogen production performance is most sensitive to variations in β [ABSTRACT FROM AUTHOR]

To improve the drag reduction performances of the proton exchange membrane fuel cell (PEMFC), a three dimensional numerical investigation about the water removal in a lotus-like PEMFC flow channel is carried out. The effects of the microstructure shape parameters (height, radius and spacing) are investigated. The investigation revealed that the liquid water can be effectively removed by the lotus-like flow channel from the channel wall surface. The appropriate height of lotus-like channel can effectively reduce the water coverage ratio on the top wall of the lotus-like flow channel. As height increases, the average drag reduction ratio increases firstly and decreases finally. When the radiuses are 25 μm and 50 μm, the average drag reduction ratios of these cases are higher than those of the other cases obviously. The spacing of the lotus-like channel has a few effects on the water removal and water coverage ratio. The lotus-like flow channel with the height of 50 μm, the radius of 50 μm and the spacing of 150 μm has a high drag reduction and anti-corrosion performance. The work in this study provides a new choice for the flow channel and has certain guiding significance for the design of the flow channel for anti-corrosion and drag reduction. • A three-dimensional numerical simulation of water behavior was carried out. • The lotus-like flow channel can accelerate the water removal. • As the height increases, the average drag reduction ratio increases. • The radius of the microstructure has influence on the droplet flow velocity. • The spacing has an inapparent effect on droplet movement. [ABSTRACT FROM AUTHOR]

A well-designed flow channel is crucial for effective water management in proton exchange membrane fuel cell. This study presents novel simulation investigation of the dynamic behavior of liquid water in three-dimensional multi-channels with various shape designs, including straight channel (SC), blocked channel (BC), wave channel (WC), and tapered channel (TC). The first, second, and third single channels are arranged in order from gas inlet in multi-channel. The results indicate that drainage rate of first channel in multi-channel is slower than that of second and third channel. Among the four designs, BC and TC reduced water ejection time by 7 ms and 6.5 ms respectively compared to SC, and reduced the time by 39 ms and 38.5 ms respectively compared to WC. In base case, drag reduction rate of TC compared to BC and WC increased by 4.12% and 20.98% respectively. However, WC has the smallest water coverage and average drag reduction ratio, while SC has a lower average gas flow resistance coefficient. This research offers innovative perspectives and theoretical foundations for current flow field design. • Dynamic behavior of liquid water in multi-channels with varying shapes is studied. • The average inlet velocity gradually increases from the first to the third channel. • The blocked channel and tapered channel exhibit better drainage performance. • Wave multi-channel demonstrates lowest water coverage and drag reduction ratio. • Straight multi-channel presents the lowest average flow resistance coefficient. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bibliometric analysis of heat and mass transfer and its management in PEMFC was carried out. • The number of annual publications has experienced a process of increasing, decreasing and increasing. • J Power Sources, J Electrochem Soc and Appl Energy are the authoritative journal in this field. • Water and heat management needs to be further optimized. Heat and mass transfer and its management is an important part of proton exchange membrane fuel cells (PEMFCs), which has a decisive impact on the performance and durability of PEMFCs. In order to comprehend the research progress and hotspots in heat and mass transfer and its management of PEMFC, 3977 literatures related to this field (up to 26th July 2022) were obtained from the Web of Science Core Collection database. Based on the mapping knowledge domain (MKD) and the VOSviewer visualization software, the number of publications, citation frequency, keyword co-occurrence, and clustering were counted and analyzed. The research progress, hotspots, and trends in the field of heat and mass transfer and its management of PEMFC were then summarized. The results show that since 2000, the annual quantity of publications in this field has experienced a period of increasing, decreasing, and then increasing, while in recent years, it is in a period of rapid growth. This field has received extensive attention in China, the United States and Canada, with many researchers, among which the quality of publications from Canada is relatively high. Related studies have been published in energy and electrochemistry journals such as the International Journal of Hydrogen Energy and the Journal of the Electrochemical Society. The Journal of Power Sources is the authoritative journal in this field with the largest total number of publications and total citation frequency. According to the keyword co-occurrence network map, there are four clusters in this field, and each cluster has a different research focus. Among them, cluster 4 has only one keyword, humidification. This field can be roughly divided into three research stages, namely, the exploration of gas–liquid two-phase flow characteristics in PEMFC, the development of PEMFC heat and mass transfer and its management, and the water and heat management and performance optimization of PEMFC. In order to achieve the development goals of high-power density, high reliability and long-life of PEMFC, the research of the third stage should be further deepened in future work. This paper will provide reference for scholars engaged in the field of PEMFC heat and mass transfer and its management. [ABSTRACT FROM AUTHOR]

The ejector enables hydrogen recycling, offering advantages of non-parasitic power and low noise. However, traditional ejector falls short in operating the proton exchange membrane fuel cell(PEMFC) system across various operating points efficiently. To overcome this limitation, a novel dual-nozzle ejector is proposed for optimal hydrogen recirculation at different power. The computational fluid dynamics(CFD) method is utilized to simulate and verified by experimental results. Firstly, nozzle structure is optimized to address unstable flow phenomena such as vortex generated at nozzle outlet. Subsequently, analysis of flow field is conducted by different structure under idle and full-load conditions. Results show that initial optimization resulted in an 18.8% increase of recirculation ratio under idle condition. Overall performance of constant-section mixing chamber diameter (D m) of 6.5 is optimal within the output current range from 31.1A to 559.8A. Under idle condition, highest recirculation ratio is achieved when constant-section mixing chamber length is 4D m , nozzle exit position is at 1.1D m , diffuser chamber angle is 3°. While under full-load condition, the energy loss caused by wall flow resistance is more significant. By exploring the mechanism of different structure changes under two conditions, particularly under idle condition, this study provides a reference for optimization of ejectors in the future. • A novel dual-nozzle ejector is designed, processed, simulated and optimized. • The optimized nozzle can solve the unsteady flow problems such as vortex at outlet. • Ejector with mixing chamber diameter of 6.5 mm is a standard for follow-up research. • Flow mechanism of different structures under two operating conditions is analyzed. • Dual-nozzle structure provides insights for design and optimization of ejectors. [ABSTRACT FROM AUTHOR]