Designing a hydrogen gas ejector for 5 kW stationary PEMFC system – CFD-modeling and experimental validation

Nikiforow, Kaj; Koski, Pauli; Karimäki, Henri; Ihonen, Jari; Alopaeus, Ville

doi:10.1016/j.ijhydene.2016.06.122

Cited by 93 publications

(41 citation statements)

References 19 publications

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“…Comparison between the modeling results and the experimental results . A, Entrainment ratio and B, mass flow rate…”

Section: Resultsmentioning

confidence: 98%

“…The mechanical compressor requires parasitic power, which decreases the system output power. Additionally, working fluids will take away the lubricant, which reduces the compressor durability . The ejector works without moving parts and requires no power consumption, leading to advantages such as high reliability, convenient maintenance, and low cost.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, various two‐dimensional (2D) models have been developed. Nikiforow et al constructed the 2D model with three types of turbulence equations (eg, SST k‐ω, RNG k‐ε, and realizable k‐ε turbulence models). The model is verified by the presented ejector for a 5‐kW stationary PEMFC system.…”

Section: Introductionmentioning

confidence: 99%

“…Additionally, working fluids will take away the lubricant, which reduces the compressor durability. 5 The ejector works without moving parts and requires no power consumption, leading to advantages such as high reliability, convenient maintenance, and low cost. The ejector is reported to be used in Honda's fuel cell vehicle.…”

Section: Introductionmentioning

confidence: 99%

“…At present, most ejector studies focus on the 1D or 2D technique to save computing resources, 5,16,[18][19][20][21] which may not be accurate enough for ejector analysis. The actual working status of the ejector is in a transient state, but most ejector models are steady state, which cannot investigate the transient behavior of ejector.…”

Section: Introductionmentioning

confidence: 99%

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Numerical investigation of ejector transient characteristics for a 130‐kW PEMFC system

et al. 2020

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Summary Improvement of fuel utilization is an important issue for proton exchange membrane fuel cell (PEMFC) system. As a promising anode recirculation method, ejector has attracted great attention because it does not require additional power consumption. However, some transient processes such as the suck, diffusion, and mix of fluids are still not thoroughly revealed, which significantly influence ejector performances. In this study, a dynamic three‐dimensional (3D) multicomponent ejector model for a 130‐kW PEMFC system is developed. The model is validated against experimental data, including the entrainment ratio and mass flow rates. The effects of operating conditions (eg, pressure, water vapor, and nitrogen mass fraction) are investigated. The results show that the fuel supply can be controlled by the primary flow pressure. When the pressure difference between the primary and secondary flow is less than 10 kPa, the secondary flow cannot be sucked into the ejector. The transient response of ejector during stack power variations can be classified into two periods: the primary flow impact period and the mixed flow impact period. Under normal fuel cell system operating conditions, when the inlet relative humidity of the secondary flow is higher than 85%, the water vapor condensation is possible to happen at the ejector outlet region, leading to fuel supply instability. Besides, the hydrogen entrainment ratio decreases with the increase of nitrogen mass fraction. The effects of geometric parameters (eg, nozzle convergence angle, secondary flow tube diameter, mixing tube length, and diffuser angle) on ejector performances are also studied. It is found that the relatively short tube leads to pressure fluctuations in the vacuum region. Increasing the tube length is beneficial to creating a stable vacuum region. However, excessive tube length can increase the friction loss. Increasing the secondary flow inlet tube diameter is beneficial to the entrainment ratio. However, further enlarging the diameter contributes negligibly to the increase of entrainment ratio once the secondary flow mass rate depends on pressure.

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“…Comparison between the modeling results and the experimental results . A, Entrainment ratio and B, mass flow rate…”

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Numerical investigation of ejector transient characteristics for a 130‐kW PEMFC system

et al. 2020

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Performance Evaluation and Degradation Mechanism for Proton Exchange Membrane Fuel Cell with Dual Exhaust Gas Recirculation

Liu

Chan

2023

Adv Energy and Sustain Res

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With growing energy and environmental challenges, clean energy technology has received worldwide attention and importance. [1] Proton exchange membrane fuel cells (PEMFCs) have the advantages of high-energy conversion efficiency, nonpolluting emissions, a wide range of fuel sources, low operating temperatures, and rapid startup steps. Therefore, PEMFCs can be used in transportation, stationary power stations, and underwater navigation. [2][3][4][5] Water generated at the cathode of a PEMFC can lead to fuel cell flooding if not purged efficiently, resulting in catalyst loss and degradation. [6][7][8] Therefore, water management is a key factor in improving the performance of PEMFCs. Excess water directly affects the performance and operational durability of PEMFC in different ways, including voltage drop caused by mass transfer limitations at high current densities, [9] voltage instability at low current densities, and unreliability during cold start. [10][11][12][13] For hydrogen-oxygen PEMFCs, the dead-ended anode and cathode (DEAC) operation strategy is usually adopted with an auxiliary gas purging scheme to achieve proper water management. [14,15] However, when the PEMFC is operated in the DEAC mode for a long time, the accumulation of liquid water can lead to electrochemical degradation of the catalyst caused by gas starvation of the fuel cell. [16] In addition, pressure fluctuations during gas purging can shock and damage the membrane electrode assembly (MEA) of PEMFCs, causing physical degradation. [17] An exhaust gas recirculation operating strategy is usually adopted for either anode or cathode systems to ensure the stable operation of the PEMFC. [18] Numerous studies on anode recirculation in PEMFCs have shown that different recirculation subsystems, such as recirculation pumps and ejectors, improve gas utilization and enable sufficient self-humidification. [19][20][21][22] Ejectors are structurally simple and do not suffer from parasitic power, but they are difficult to adapt to changes in the operating strategy of the PEMFC. [23] Recirculation pumps have the advantages of a wide operating range and simple control, but the efficiency of the entire system is low. [24] Much of the research on exhaust gas recirculation in fuel cells has focused on hydrogen recirculation, and only a few studies have been conducted on PEMFC systems with dual gas recirculation.The oxygen recirculation subsystem also plays a critical role in the economy of the entire PEMFC system, internal water balance of the stack, and lifetime of the MEA. Zhang et al. [25] established a dynamic mechanism model for the cathode recirculation of

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Performance investigation of a multi‐nozzle ejector for proton exchange membrane fuel cell system

et al. 2020

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Summary Due to its merit of no consuming energy, no moving part, and less requiring space, and maintenance, the ejector is one of the most promising hydrogen recirculation devices for proton exchange membrane fuel cell (PEMFC) applications. However, the prominent problem is its poor adaptability of the conventional ejector to meet the power range requirements of the PEMFC system. Thus, a multi‐nozzle ejector was investigated to widen the applicable power range of a PEMFC system. The designed multi‐nozzle ejector consists of one central nozzle (CN) and two symmetrical nozzles (SNs). The CN mode is activated under low power conditions, while the SNs mode is switched to adapt high power conditions. A 3D computational fluid dynamics (CFD) model was established to simulate the performance of ejectors, and an experimental test bench was built to validate the accuracy of the CFD model. The results indicated that the mixing chamber diameter (Dm) and throat tilt angle of SNs (αt) have a significant effect on the entrainment performance. It was found that the multi‐nozzle ejector can broaden the hydrogen supply range from 0.27 to 1.6 g/s (22‐100 kW) with the optimal combination of a Dm of 5.0 mm and αt of 8°. Nevertheless, the hydrogen supply range is 0.48 to 1.6 g/s (37‐100 kW) when using a conventional single‐nozzle ejector with a Dm of 5.0 mm. Moreover, the temperature, pressure, and relative humidity of the secondary flow have a great influence on the hydrogen entrainment ratio with the change of stack power.

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Designing a hydrogen gas ejector for 5 kW stationary PEMFC system – CFD-modeling and experimental validation

Cited by 93 publications

References 19 publications

Numerical investigation of ejector transient characteristics for a 130‐kW PEMFC system

Numerical investigation of ejector transient characteristics for a 130‐kW PEMFC system

Performance Evaluation and Degradation Mechanism for Proton Exchange Membrane Fuel Cell with Dual Exhaust Gas Recirculation

Performance investigation of a multi‐nozzle ejector for proton exchange membrane fuel cell system

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