Oxygen Starvation Research Articles

Oxygen-sensor-based 2-DOF PI air-flow controller of fuel cell system

Oxygen starvation may occur when oxygen is not replenished quickly after a sudden increase of load in fuel-cell-powered vehicles, leading to permanent damage to the fuel cell membrane. To avoid this phenomenon, the oxygen excess ratio (OER) is usually estimated through observers as it cannot be measured directly. Since observers may suffer from model mismatches that lead to inaccurate OER estimation, a possible modification to the fuel cell system is proposed in this work by including an oxygen flow sensor at its exhaust. Yet the response of this sensor is slow, and to compensate for the slow response of the sensor, a novel two-degree-of-freedom PI controller and a state observer are designed to provide a robust, accurate, and quick estimation and control of the OER.

Extended Kalman filter for quantifying hydrogen leaks in PEM fuel cells by estimating oxygen concentration

Hydrogen transfer leaks are one of the most important life-limiting faults in polymer electrolyte membrane fuel cells (PEMFCs). Hydrogen transfer leaks result in a reduction in the amount of oxygen available in the cathode (air) channel, with large leaks resulting in oxygen starvation and hydrogen emission. This paper aims to develop an adaptive extended Kalman filter (EKF) to estimate the unknown oxygen concentration, which is then used to infer hydrogen leaks. To this end, the paper first develops the lumped model of the fuel cell from a pseudo-2D model of a fuel cell. Next, a (non-adaptive) EKF is developed to estimate the fuel cell states under both normal and oxygen-starved conditions. The adaptive EKF is then implemented by adding the unknown hydrogen leak to the list of estimated states. Finally, the paper demonstrates the efficacy of the proposed adaptive EKF by using it to accurately estimate unknown hydrogen leaks in a high-fidelity virtual fuel cell under excessively noisy conditions.

Soft sensor for viable cell counting by measuring dynamic oxygen uptake rate

Regulatory authorities in biopharmaceutical industry emphasize process design by process understanding but applicable tools that are easy to implement are still missing. Soft sensors are a promising tool for the implementation of the Quality by Design (QbD) approach and Process Analytical Technology (PAT). In particular, the correlation between viable cell counting and oxygen consumption was investigated, but problems remained: Either the process had to be modified for excluding CO2 in pH control, or complex kLa models had to be set up for specific processes. In this work, a non-invasive soft sensor for simplified on-line cell counting based on dynamic oxygen uptake rate was developed with no need of special equipment. The dynamic oxygen uptake rates were determined by automated and periodic interruptions of gas supply in DASGIP® bioreactor systems, realized by a programmed Visual Basic script in the DASware® control software. With off-line cell counting, the two parameters were correlated based on linear regression and led to a robust model with a correlation coefficient of 0.92. Avoidance of oxygen starvation was achieved by gas flow reactivation at a certain minimum dissolved oxygen concentration. The soft sensor model was established in the exponential growth phase of a Chinese Hamster Ovary fed-batch process. Control studies showed no impact on cell growth by the discontinuous gas supply. This soft sensor is the first to be presented that does not require any specialized additional equipment as the methodology relies solely on the direct measurement of oxygen consumed by the cells in the bioreactor.

Optimization on the peroxide ratio control strategy of PEMFC system based on immune algorithm

The air supply system is an essential component of a proton exchange membrane fuel cell (PEMFC), and proper control of the oxygen stoichiometry ratio(λo2) is crucial to prevent oxygen starvation in the PEMFC while maintaining efficient and stable performance output. In response to the issues of poor dynamic performance and slow response in traditional λo2 control strategies, this study was conducted to establish a dynamic oxygen flow model of the PEMFC and proposed a λo2 control strategy based on an immune algorithm-fuzzy PID (IAFPID). The performance of the IAFPID control strategy in λo2 control was analyzed under different load requirements, simulated vehicle dynamic loads, and temperature disturbances. The results demonstrate that the IAFPID control strategy has advantages such as fast convergence speed, strong robustness, and good dynamic performance. The efficiency of achieving the optimal stoichiometry ratio for high power output in PEMFC under disturbances was nearly 50% higher with IAFPID control compared to traditional PID, Fuzzy-PID, Genetic Algorithm PID, and Immune Algorithm PID strategies. Furthermore, this method ensures a lower average error in maintaining stable λo2 under dynamic disturbances compared to the IAPID and PID control strategies, with reductions of 12.93% and 37.75%, respectively.

Research on the coordinated control of oxygen excess ratio and air pressure for PEMFC's air supply system

The proton exchange membrane fuel cell (PEMFC) air supply system is a complex nonlinear system with strong coupling of air flow and pressure. To avoid oxygen starvation and unstable output performance during rapid load changes, the oxygen excess ratio (OER) and air pressure need to be controlled effectively. To cope with the nonlinearity, coupling and uncertainty of the PEMFC air system, this paper puts forward a coordinated controller regulating OER and air pressure based on the input-output linearization and sliding mode methods. Firstly, a control-oriented third-order model is proposed to describe the dynamic behavior of the air supply system. Secondly, this paper decouples the flow and pressure of the PEMFC air system by using an input-output linearization method to obtain two independent linear subsystems. Moreover, a sliding mode method, effectively coping with the uncertainty of the system model, is designed to regulate the OER and air pressure of the PEMFC, which enhances the robustness of the control system. The overall simulation outcomes show that the proposed controller regulates OER and cathode pressure with smaller root mean square error (RMSE) and mean absolute percentage error (MAPE) compared with the combined proportional integral (PI) and feedforward controller.

Performance evaluation of proton exchange membrane fuel cells adopting rectangular-baffle and tapered flow channels with an equivalent average depth

ABSTRACT Optimizing the flow channel structures can improve the efficiency of proton exchange membrane fuel cells and promote the efficient utilization of clean energy. This study investigates the impacts of rectangular-baffle and tapered flow channels on electrical performance, temperature distribution and mass transfer of proton exchange membrane fuel cells, based on a 3D, multi-physical model. The equivalent average depth is adopted as the reference benchmark to mitigate the influence of channel depth. Results indicate that adopting variable-depth channels enhances convective mass transfer on the porous layer surface under higher voltage. The convective mass transfer of oxygen is dominant in the activation polarization region, while diffusion is dominant in the concentration polarization region. Variable-depth channels enhance heat and mass transfer in comparison to the straight channel. The tapered channel can improve the mass transfer flux in oxygen starvation region, and the drainage ability of the rectangular baffle channel is inferior to the tapered channel. The rectangular baffle channel demonstrates better convective heat transfer performance and temperature uniformity. A rectangular-baffle channel can increase net power by 4.31%, while a tapered channel can achieve a maximum increase of 9.27% when the pumping power is considered. Therefore, incorporating a tapered channel is an optimal strategy to boost cell efficiency.

Oxygen starvation control of proton exchange membrane fuel cell through fusion control strategy

Oxygen excess ratio (OER) is regarded as a significant indicator of the safety and efficient operation of the open-cathode proton exchange membrane fuel cell (PEMFC) system. This is because inappropriate OER is prone to the phenomenon of oxygen starvation and oxygen saturation under load conditions change frequently. To avoid the phenomenon, this paper integrates linear active disturbance rejection control (LADRC) and proportional integral differential (PID) control to regulate OER of fuel cell air supply system, which effectively combines model-based and data-driven LADRC structure. As the controller parameters directly affect the control performance and it is difficult to obtain the optimal control parameters. Especially, when the load conditions change, the control parameters are difficult to adapt the load changes. To this end, a snake optimization (SO) algorithm with easy implementation and fast convergence is used to realtime update the controller parameters, which can further improve the control effects. Firstly, an equivalent linear model of fuel cell air supply system is established. Secondly, a hybrid LADRC method is developed by combining the merits of the LADRC and PID methods. Thirdly, the SO algorithm is used to optimize the controller parameters, which can achieve the optimal control parameters. Finally, the results revealed that the proposed method has a faster response with less noise sensitivity against the load changes and stronger robustness than the other methods.

Finite‐time sliding mode fault‐tolerant control of PEM fuel cell air supply system

AbstractProton exchange membrane (PEM) fuel cell air supply system is primarily responsible for delivering air to the fuel cell at a specific stoichiometric ratio for chemical reaction. The stoichiometric ratio will be impacted by the sudden change in load and system failure. Under the aforementioned circumstances, precise and timely air supply regulation is required to avoid irreparable PEM damage. In order to enhance the robustness and performance of the fuel cell, a cascaded finite time sliding mode fault‐tolerant control method is proposed for the air supply system of PEMFC. The control objective is to adjust the oxygen excess ratio at the cathode flow field, which can avoid the occurrence of oxygen starvation in the PEM fuel cell when the load current changes rapidly or when fault occurs. A cascaded controller structure is introduced, where, in the inner loop, an adaptive sliding mode controller is designed to reconstruct fault signal and track the optimal output trajectory and, in the outer loop, a finite‐time observer is employed to obtain the expected output trajectory. The proposed control scheme is capable of fault‐tolerant tracking of the optimal oxygen excess ratio within finite time. The effectiveness of proposed fault‐tolerant control algorithm is verified through hardware‐in‐the‐loop (HIL) studies.

Novel electrochemical and thermodynamic conditioning approaches and their evaluation for open cathode PEM-FC stacks

The Air-cooled and open cathode proton exchange fuel cell (PEMFC) offers particular advantages in terms of complexity and weight reduction. Therefore, it seems very attractive to support the aviation industry in their de‑carbonisation process. Major challenges in terms of operational stability and reliability hinders this technology to be used in commercial applications.Therefore, this study thoroughly examines the conditioning and optimization of open cathode PEMFC stacks, drawing insights from experimental findings. Key areas of focus include the enduring impact of pre-humidification, the quantification of efficiency enhancements through reconditioning via oxygen starvation, and the refinement of Electrochemical Impedance Spectroscopy (EIS) data analysis under non-stationary conditions.The pre-humidification enhances stack performance by improving cell voltages from 40.09 V to 41.37 V at 30 A, increasing membrane humidity and improving efficiency. Furthermore, the residual water in the stack also functions as evaporative cooling and can assist in limiting the operating temperature of the stack during system start up. However, it is demonstrated that excessive soaking with water leads to severe flooding phenomena at the beginning of operation.A reconditioning period of 100 s through oxygen starvation induces a notable increase in stack voltage, from 41.37 V to 47.79 V at 35 A, which decreases to 43.56 V after 10 min of operation. This corresponds to an average increase in electric energy provision of about 6.2% at constant hydrogen consumption, attributed to PtOx reduction and increased water production.Despite limitations outside the medium frequency range (approximately 10 Hz – 15 kHz) for non-stationary conditions, EIS aids in understanding of the stack behaviour and supports the interpretation of current and voltage results. A novel evaluation method enables the quantitative description of the condition using EIS data. This data reveals a considerable drop (on average about 21,5% for the 10 A point and about 27,4% for the 30 A point) in charge transfer resistances of the fuel cell from initial operation to measurements after overnight soaking and the first series of oxygen starvation recovery.

Tailored diffusion limiting membrane for microneedle glucose sensors with wide linear range

Continuous glucose monitoring is very important to daily blood glucose control in diabetic patients, but its accuracy is limited by the narrow linear range of the response of biosensor to the glucose concentration because of the oxygen starvation in tissue and the limited maximum conversion rate of glucose oxidase. In this work, a biocompatible diffusion limiting membrane based on two medical-grade polyurethanes is developed via blending modification to restrict the diffusion flux of glucose to match the oxygen concentration and the maximum conversion rate. The expansiveness of the linear range for the nanomaterials-modified electrode in the glucose biosensor can be achieved through the regulation of two polyurethanes, the solvent, and the thickness of the membrane. In addition, the mass transport of hydrogen peroxide and interfering substances is also limited of the membrane. The in vitro experiments demonstrated that the membrane-modified microneedle biosensor exhibited a rapid response to the concentration variation of glucose, a wide linear range that is sufficient to cover the blood concentration of healthy and diabetic people, the ability to resist the oxygen concentration fluctuation and interfering substances, good reproducibility and long-term stability. The custom wearable electrochemical system, possessing these characteristics, has been proven to accurately monitor the blood concentration in a living rat in real time. This demonstrates a significant potential for application in both daily and clinical blood glucose monitoring.

Design of 2DOF control system fused with artificial intelligence for power enhancement and mitigation of degradation in fuel cell systems

The commercialization of Fuel Cell Systems (FCSs) faces a key obstacle in the form of limited cell lifespan and resultant cell degradation. This paper introduces a new approach, leveraging an artificial intelligence-based 2DOF control system to regulate the Oxygen Excess Ratio (OER) with two main goals: mitigating cell degradation due to oxygen starvation and optimizing net power output. The proposed control system incorporates a data-driven feedforward controller in conjunction with a feedback controller, facilitating the tracking of desired OER values generated by a data-driven reference generator. We develop fuzzy models and neural networks as the reference generator and feedforward controller to capture the complex FCS behavior by processing the stack current w/wo the temperature of FCS (i.e. Single input or Double input models). By exploring the effects of the structural settings of the models, this study provides a comprehensive understanding of their impact on the representation performance of the FCS characteristics. Although the fitting performances of all models are quite satisfactory, their actual performance gain is evaluated on a realistic FCS model at various operation points. The findings and comparative analysis emphasize the efficacy of incorporating stack temperature in fuzzy-model-based 2DOF control systems, showcasing their potential to maximize net power output through enhanced OER control loop performance while also extending the lifespan of FCSs, as confirmed by results from a developed degradation model.

Research and Optimization of Four Serpentine-Wave Flow Fields in PEMFC

The layout of the cathode flow field largely determines the net output power of the proton exchange membrane fuel cell (PEMFC). To make the normal mass transfer effect best, the longitudinal channel was waved based on four serpentine flow channels, and the effects of sag depth and longitudinal channel width on the output efficiency of the cell were explored. The results show that the wave channel design systematically enhances the forced convection between adjacent channels, which can prevent a large zone of oxygen starvation zone at the outlet of the channel. The increase of the normal velocity in the gas transmission process will inevitably induce a significant enhancement of the mass transfer effect and obtain a higher current density in the reaction zone. For the longitudinal channel width, it is found that increasing its size in the effective range can greatly reduce the channel pressure drop without reducing the output power, thereby improving the overall efficiency. When the sag depth and longitudinal channel width gradient are 0.6 mm and 0.2 mm respectively, PEMFC can obtain the best comprehensive performance.

КОРРЕКЦИЯ КИСЛОРОДНОГО ГОЛОДАНИЯ В ЭКСПЕРИМЕНТАХ НА ЖИВОТНЫХ ПРИ МОДЕЛИРОВАНИИ ЭФФЕКТОВ, ВЫЗЫВАЕМЫХ ОСТРОЙ ДЫХАТЕЛЬНОЙ НЕДОСТАТОЧНОСТЬЮ, С ПОМОЩЬЮ МНОГОКОМПОНЕНТНОЙ ГАЗОВОЙ СМЕСИ НА ОСНОВЕ КОМБИНАЦИИ ИНЕРТНЫХ ГАЗОВ

Acute respiratory insufficiency (ARI) accompanied with hypoxemia and hypercapnia requires oxygen therapy. The helium-oxygen therapy secures from the undesirable effects of oxygen therapy. Earlier we showed that introduction of argon in a breathing mixture (BM) reduces the effect of hypoxia. Purpose of the work is to test the potentiality of BM containing a combination of inert gases to counteract oxygen starvation in acute ARI-provoking experiments with animals. Fourteen Wistar rats with a body mass of 276 ± 14.6 grams were divided into two groups. An integral noninvasive technology was used for real-time assessment of oxygen transport and consumption in each animal. Both the experiment and control animals breathed a mixture with a low O2 and high CO2 concentration. The control animals received a routine therapy by a hyperoxic mixture containing nitrogen and carbon dioxide. The experimental animals were treated with a hyperoxic mixture containing helium and argon, and carbon dioxide to induce hypercapnia. The results demonstrated reliably that the hyperoxic heluim-argon mixture reduces burden on the external respiration and favors oxygen utilization in tissues; however, this happens at the expense of a greater stress to the cardiovascular system. In contrast, the hyperoxic mixture used in the control stressed the external respiration rather than the cardiac muscle.

Thin layer chromatography of plant phospholipids of Zea mays (L.) un-der the action of the phytohormone kinetin in different aeration condi-tions

Under extreme weather conditions, crops are exposed to excess rainfall, causing the acute oxygen starvation of plants. The treatment of plants with phytohormones started in order to increase plant resistance to stresses. Using thin layer chromatography, the effect of the phytohormone kinetin on the content of plant phospholipids was studied under different aeration conditions. A kinetin solution (10 mg l-1) was injected into the etiolated maize seedlings separated from the roots by the suction method with a transpiration current and seedlings were transferred to aeration conditions, hypoxia or carbon dioxide (9 hours). Control plants were not treated with kinetin. Samples were fixed with boiling isopropanol and extracted with a hexane:isopropanol mixture (3:2). After purification from non-lipid impurities, lipids were evaporated and dissolved in chloroform. Phospholipids were isolated on silica gel W plates and further separated into classes on silica gel 60G plates. (“Merk”, Germany). It was found that the content of total phospholipids in maize seedlings decreased to 84.9% under hypoxic conditions and to 54.5% in CO2. If plants were pre-treated with kinetin, the content of total phospholipids practically did not change (96.2%), and in CO2 it increased to 88.5%. When plants were treated with kinetin under aeration conditions, the content of phosphatidylcholine (PC), phosphatidylserine (PS) and phosphatilylethanolamium (PEA) increased, and phosphatidylglycerol (PG) decreased by almost 40%. Under conditions of oxygen deficiency, changes in the composition of phospholipids were different. The content of PS and PC in seedlings increased by1.5-2.0 times, and the content of PG and PEA decreased to 27.2% and 20.0% of the control. Treatment of maize seedlings with kinetin reduced the effect of gaseous media on the content of all analysed classes of phospholipids in plants, this was especially evident in CO2. Thus, it can be considered proven that the protective effect of kinetin is realized due to the ability of this phytohormone to maintain the optimal content and ratio of phospholipid components characteristic of a given tissue in plants exposed to various unfavourable environmental factors, including oxygen deficiency and high concentrations of carbon dioxide.

Sensitivity of the thermohaline circulation during the Messinian: Toward constraining the dynamics of Mediterranean deoxygenation

During the Messinian, the sensitivity of the Mediterranean Basin to ecosystem perturbation was enhanced in response to the progressive restriction of water exchange with the Atlantic Ocean. The widespread deposition of organic-rich layers (i.e. sapropel) during the Messinian testifies the perturbation of the carbon and oxygen cycles; indeed, these sediments were deposited under conditions of oxygen starvation, presumably in response to a periodic deterioration of the thermohaline circulation strength. Disentangling the causes, the effect and magnitude of the thermohaline circulation weakening during the geological past is crucial for better constraining present and near-future deoxygenation dynamics in the Mediterranean region under the current climate warming. For this purpose, we investigate a Messinian sapropel-bearing succession cropping out at Monte dei Corvi (Ancona, central Italy) with mineralogical, petrographic, micropaleontological and stable Carbon and Oxygen isotopic analyses. We show that sapropel layers were deposited in response to an increase of the sea surface buoyancy, which hampered the thermohaline circulation and thus the oxygenation of bottom water, in turn affecting the bioturbating organisms. Within the lithological cycle, the recovery of an efficient thermohaline circulation is recorded by thin packstone layers underlying the marly limestone/marlstone, which record intense bottom currents. The marly limestone/marlstone accumulated during periods of intense primary productivity and organic carbon export to the sea bottom, which promoted bottom hypoxia but not organic matter preservation. We infer that these lithological changes resulted from variations in the Adriatic Deep Water formation system, controlled by precession-driven climatic and oceanographic changes.By integrating previously published Sea Surface Temperature (SST) with new isotopic and mineralogical data, we show that variations in Sea Surface Salinity (SSS) were the leading factor controlling sapropel deposition, minimizing the role of primary productivity. The SSTs characterizing the sapropel deposits are close to the range of those projected in the Eastern Mediterranean at the end of this century under climate warming. In this scenario, future warming will be coupled with SSS increase, which will counteract the density loss provided by temperature, making the bottom deoxygenation in the Eastern Mediterranean abysses unlikely. However, additional forcing, such as winter heat waves and eutrophication, could contribute to negatively affecting the Mediterranean oxygen balance and should be considered in model-based projections.

Operation features of aviation tankers in the conditions of the Far North

Huge territories of the Russian Federation are occupied by permafrost. Often aviation is the only mode of transport that connects remote north areas of the country with the rest of Russia. The main feature of permafrost regions is the harsh climate, which includes low negative temperatures, an abundance of snow and strong winds. Such conditions make it extremely difficult to operate ground vehicles that service and maintain flights. In recent years, more and more domestic tankers have been exhausting their life span. At present, a significant number of northern refueling complexes have switched to the operation of foreign tankers based on Volvo and Mercedes-Benz tractors. The operation of these vehicles has already revealed a series of shortcomings which extremely complicate the normal procedures. There is an acute need to refine the components and assemblies in order to reduce the failures that affect the regularity and safety of aircraft flights. One of the main problems of fuel tankers operation at low temperatures is the malfunction of the electropneumatic bottom valve, due to its freezing. The paper proposed replacing this problematic node with a mechanical bottom valve, which is not susceptible to low temperatures. In order to avoid cracking of rubber products of the underwing refueling nozzle and to increase the flexibility of the dispensing hoses, it is proposed to carry out heating of the glass of the refueling nozzle and the filling module by means of exhaust gas bypass and pumping hot coolant through the system of nozzles. The most serious problems are the difficulties of operating a diesel-powered tractor at low temperatures. Problems arise already at startup. Diesel fuel at low subzero temperatures can thicken or even solidify, the lubricant also thickens. There have been cases when the startup was complicated by low compression in the cylinders. But even if the engine was able to start, after a while it may start to stall. This is due to oxygen starvation, which occurs because the icy air entrains water, which is deposited as frost on the air filters, thereby blocking the oxygen supply to the engine. After prolonged parking at low temperatures, during the first seconds of starting the piston engine, the parts come into contact with each other without lubrication. The reason is the viscosity of the oil which decreases at extremely low temperatures, therefore, in order for the lubricant to reach the end users through narrow oil pipelines, it takes some time to warm up (about 10 minutes). As a result of such cold starts and the risk of bullying on the parts of the piston group, their durability is reduced by more than 40%. When starting cold, the engine additionally warms up itself at higher idle speeds. To prevent undesirable consequences, as well as to create more favorable conditions for starting the diesel unit, reducing fuel consumption, it is proposed to use a pre-heater with an external power source from the 220 V electrical network. In order to facilitate the start of the diesel engine, it is necessary to provide the heating of the fuel line and fuel pump filters. To eliminate oxygen starvation of the engine, due to the formation of frost on the filter elements, and to increase the stability of the engine, it is necessary to provide the heating of the air filter.

Antibacterial mechanism of kojic acid and tea polyphenols against Escherichia coli O157:H7 through transcriptomic analysis

Escherichia coli O157:H7 is one of the major foodborne pathogenic bacterial that cause infectious diseases in humans. The previous found that a combination of kojic acid and tea polyphenols exhibited better activity against E. coli O157:H7 than using either alone. This study aimed to explore responses underlying the antibacterial mechanisms of kojic acid and tea polyphenols from the gene level. The functional enrichment analysis by comparing kojic acid and tea polyphenols individually or synergistically against E. coli O157:H7 found that acid resistance systems in kojic acid were activated, and the cell membrane and genomic DNA were destructed in the cells, resulting in "oxygen starvation". The oxidative stress response triggered by tea polyphenols inhibited both sulfur uptake and the synthesis of ATP, which affected the bacteria's life metabolic process. Interestingly, we found that kojic acid combined with tea polyphenols hindered the uptake of iron that played an essential role in the synthesis of DNA, respiration, tricarboxylic acid cycle. The results suggested that the iron uptake pathways may represent a novel approach for kojic acid and tea polyphenols synergistically against E. coli O157:H7 and provided a theoretical basis for bacterial pathogen control in the food industry.

Oxygen excess ratio control of PEM fuel cell systems with prescribed regulation time

In this paper, we focus on addressing the air supply problem for fuel cells. The air supply system faces a challenge: operating at maximum load consumes a significant amount of power, while insufficient air can lead to oxygen starvation problems in fuel cells. An important metric, the oxygen excess ratio, indicates whether the fuel cell is receiving the appropriate amount of air. Unfortunately, directly measuring this ratio is generally impractical. To overcome this limitation, we propose a fixed-time observer that reconstructs the oxygen excess ratio within a short predetermined period. By utilizing this reconstructed index, we introduce a cascaded double-loop controller. Specifically, both the external and internal loops are regulated using a modified prescribed time control strategy. This approach enables the regulation of the oxygen excess ratio to the optimal value within a prescribed short time. The advantages of our proposed method are validated through hardware in-loop experiments, showcasing its superiority over conventional finite-time control techniques.

Dynamic performance improvement of proton exchange membrane fuel cell system by robust loop shaping and artificial intelligence optimized fractional order PI controllers

ABSTRACT Due to inherent nonlinear behavior, the Proton Exchange Membrane (PEM) Fuel Cell system yields in poor power quality. The sudden change in stack current causes uncertainty in PEMFC behavior resulting in degraded output. This necessitates the control of supply manifold pressure on the cathode side to prevent oxygen starvation. In this work, three techniques, namely, robust loop shaping, smith predictor, and Fractional Order Proportional Integral (FOPI) controllers, are designed after incorporating parametric uncertainty in system description. Further, the Particle Swarm Optimization (PSO) artificial intelligence technique is implemented to optimize the parameters of smith predictor and Fractional Order PI controllers. By stabilizing the system across the entire parameterized uncertainty range, the proposed control strategies, namely, loop shaping, PSO-Smith Predictor, and PSO-FOPI controller effectively compensate uncertainty effects. The simulation result shows that the PSO-tuned FOPI controller has best overshoot at operating points 3, 4, and 5 having a value of 0.505% in comparison with PSO-Smith Predictor where overshoot (ranging from 19.88% to 40.141%) is too high; and loop shaping controller having high values of overshoot (more than 40% at every operating point) Thus, PSO-FOPI controller exhibits the best performance with far superior overshoot and steady-state stability.

Cross flow and distribution characteristics in automobile polymer electrolyte membrane fuel cells: A three-dimensional full-scale modeling study

Ultrahigh power density is of primary importance to next-generation polymer electrolyte membrane fuel cell (PEMFC) for commercialization, which demands an in-depth insight into the intricate multi-physics transports, particularly for large-size PEMFCs in automobile application. In this study, a three-dimensional two-phase model is extended to study an automobile fuel cell with the active area of 366.6 cm2, including full morphologies of metallic bipolar plate, flow field, and distribution zones for hydrogen, air and coolant flow. It is found that the cross flow inside membrane electrode assembly under the rib between two adjacent channels promoted by the distribution zone can effectively mitigate local oxygen starvation and water flooding, increasing PEMFC performance at high current density, in comparison with conventional single-channel or no-dot-matrix models. Theoretical analysis indicates that the dot matrix distribution zone induces a larger pressure gradient and hence the cross flow than the commonly-used channel & rib distribution zones. Additionally, the counter-flow configuration has a higher cell performance and more uniform current density than the co-flow one due to internal humidification. When the internal humidification effect is weak, for example, in anode/cathode gas co-flow configuration, coolant flow direction becomes more important for the temperature profile and prevent severe dehydration.