Gas Flow Channel Research Articles

A modified design of the gas flow channel geometry for the proton exchange membrane fuel cells: A three-dimensional simulation

<h2>Abstract</h2> Nowadays, researchers are seeking to find the most clean and environmental solution as an alternative for the internal combustion engines with efficient performance. Proton exchange membrane fuel cell (PEMFC), which operates at low temperatures, uses electrochemical reactions to convert hydrogen to electricity, water, and heat without harmful pollutants and carbon dioxide. Technology advancement for this device is still active to reduce the costs, lower the degradation, and improve the water/thermal management, which result in better cold-start capabilities as well. In PEMFCs, the hydrogen flows inside the cell through the gas flow channel at the anode, while the oxygen reaches the gas diffusion layers (GDL) at the cathode. Better distribution of the gases in the gas flow channel result in improved reaching of the active cites in the catalyst layer, where the electrochemical reactions happens. In other words, the homogeneous distribution of the reactants gases improves the performance of the system and also prevents the blockage of the reactants in the GDL. This study suggests a novel design for the gas flow channel to improve the distribution of the reactant gases in the gas diffusion layer of PEMFC.

Additively manufactured cryogenic microchannel distillation device for air separation

AbstractThe efficiency of air separation is tested using three different small‐scale cryogenic distillation columns. The performance of a random packed column is compared to the performance of two microchannel distillation (MCD) columns that use thin wicking structures and gas flow channels to achieve process intensification. The MCD columns tested include a plate‐type layered column and an additively manufactured porous honeycomb (AMPH) column. For columns with 25.4 cm of active height and run under similar conditions, the packed, plate‐type layering, and AMPH columns achieved approximate height equivalent of a theoretical plate (HETP) values of 5.5, 3.7, and 3.2 cm for nitrogen, and 5.9, 4.9, and 3.3 cm for argon. The AMPH column can produce up to 0.4 SLM of more than 90% purity oxygen with 12 W of cooling lift. These results demonstrate the feasibility of using additive manufacturing to construct MCD devices and pave a way for constructing novel MCD designs.

Analysis of performance optimization of high‐temperature solid oxide electrolytic cell based on the coupling of flow, heat, and mass transfer and electrochemistry

AbstractA three‐dimensional (3D) model simulating the flow, heat, and mass transfer characteristics of a high‐temperature solid oxide electrolytic cell (SOEC) is developed based on the coupling of gas flow in channels, the electrochemical reaction in the triple‐phase boundary of electrodes and component diffusion in the porous media in electrodes. The model comprises several equations such as mass equation, momentum equation, energy equation, mass transport equation, and electrochemical reaction equation. The computational fluid dynamics method is adopted to simulate the operating performance (current density distribution, temperature distribution, and gas component distribution) of the 3D electrolytic cell model under different operating conditions (electrolytic voltage, gas temperature at the inlet, flow rate and flow pattern). The simulation results show that gas temperature at the inlet obviously influences electrolytic hydrogen production by SOEC. In the case of lower voltage, a higher temperature can be selected to effectively increase the current density. When the current density is high enough, the supply flow of water vapor needs to be increased to prevent the inhibition reaction of low‐concentration reactants, but this may lead to the reduction of water vapor conversion. In practical operation, a lower voltage and higher gas temperature should be selected, and the flow rate of water vapor appropriately increased to ensure hydrogen production and improve operating efficiency.

Особливості варіювання просторової форми лопаток при аеродинамічному вдосконаленні компресорів авіаційних газотурбінних двигунів

This work is devoted to the development of procedures for the aerodynamic improvement of gas-turbine engine axial-flow compressor blade rows. The aim of the work is to compare the efficiency of two methods for impeller blade shape variation in the aerodynamic improvement of an aircraft gas-turbine engine two-stage fan. The first method consists only in varying the blade profile angle along the blade height, while the second consists in varying the blade profile angle and geometrical parameters. The features of the approach used in the solution of this problem are as follows: formulating quality criteria as the mean integral values of the power characteristics of each impeller of the fan over the operating range of the air flow rate through the impeller and searching for advisable values of the impeller blade parameters by scanning the independent variable range at points that form a uniformly distributed sequence of small length. The basic tool is a numerical method developed at the Institute of Technical Mechanics of the National Academy of Sciences of Ukraine and the State Space Agency of Ukraine, which simulates 3D turbulent gas flows in the compressor stage blade channels using the complete averaged Navier¬–Stokes equations. The results of multiparameter calculations of 3D turbulent gas flows show that at the initial stage of the aerodynamic improvement of compressor blade rows varying the blade profile angle alone is more efficient; however, increasing the number of elements of the uniformly distributed sequence of points in the variable range increases the possibility of finding a point at which the blade profile aerodynamic characteristics significantly improve. The results obtained are expected to be used in the aerodynamic improvement of gas-turbine engine compressor blade rows.

Noninvasive Diagnosis of Gastric Cancer Based on Breath Analysis with a Tubular Surface-Enhanced Raman Scattering Sensor.

SERS-based breath analysis as an emerging technique has attracted increasing attention in cancer screening. Here, eight aldehydes and ketones in the human breath are reported as the VOC biomarkers identified by gas chromatography-mass spectrometry (GC-MS) and applied further for the noninvasive diagnosis of gastric cancer (GC) with a tubular SERS sensor. The tubular SERS sensor is prepared with a glass capillary loaded with ZIF-67-coated silver particles (Ag@ZIF-67), which offers Raman enhancement from the plasmonic nanoparticles and gas enrichment from the metal-organic framework (MOF) shells. The composite materials are modified with 4-aminothiophenol (4-ATP) to capture different aldehyde and ketone compounds. The tubular sensor is served simultaneously as a gas flow channel and a detection chamber, bringing a higher gas capture efficiency than the planar SERS sensor. As a proof-of-concept, the tubular SERS sensor is successfully employed to screen gastric cancer patients with an accuracy of 89.83%, based on the noninvasive, rapid, and easily operated breath analysis. The results demonstrate that the established breath analysis method provides an excellent alternative for the screening of GC and other diseases.

Damage Characteristics Caused by Deep-Hole Blasting near Normal Fault and Its Effects on Coal and Gas Outbursts

To understand the stability of coal and rock in areas of normal faults disturbed by the dynamic loads of blasting, the damage characteristics of coal and rock within a normal fault are investigated using similarity simulation tests. The mechanism for coal and gas outbursts within a normal fault is analyzed theoretically, and the results indicate that the maximum tensile stress in the vertical direction of the blasting hole in the normal-fault model is 1.17 times that in the no-fault model. The propagation of cracks near the blasting hole produces crushing circles, and more cracks are produced in the normal-fault model, causing severe damage to the coal seam and floor rock adjacent to the upper wall of the normal fault. Meanwhile, coal on the surface of the coal seam falls off. The cracks extend to the roof rock through the footwall of the normal fault. Cracks in the adjacent strata and coal seam interpenetrate those around the blasting hole, which is a potentially dangerous area for coal and gas outbursts. The cumulative damage caused by blasting vibrations increases the extent and scope of the damage to coal and rock, and broken coal and rock provide weak surfaces and gas flow channels that can lead to dynamic gas disasters. The research results will provide a theoretical basis for gas dynamic disasters induced by blasting disturbance in normal fault structures. Based on cases of coal and gas outbursts in the Didaoshenghe Coal Mine in Heilongjiang Province, China, an important reason for such incidents is considered to be the blasting areas of normal faults being disturbed by air-powered coal drilling.

Simulation of Mass and Heat Transfer in an Evaporatively Cooled PEM Fuel Cell

Evaporative cooling is a promising concept to improve proton exchange membrane fuel cells. While the particular concept based on gas diffusion layers (GDLs) modified with hydrophilic lines (HPILs) has recently been demonstrated, there is a lack in the understanding of the mass and heat transport processes. We have developed a 3-D, non-isothermal, macro-homogeneous numerical model focusing on one interface between a HPIL and an anode gas flow channel (AGFC). In the base case model, water evaporates within a thin film adjacent to the interfaces of the HPIL with the AGFC and with the hydrophobic anode GDL. The largest part of the generated water vapor leaves the cell via the AGFC. The transport to the cathode side is shown to be partly limited by the ab-/desorption into/from the membrane. The cooling due to the latent heat has a strong effect on the local evaporation rate. An increase of the mass transfer coefficient for evaporation leads to a transport limited regime inside the MEA while the transport via the AGFC is limited by evaporation kinetics.

Effects of Geometrical Parameters of Gas Flow Channels on Polymer Electrolyte Membrane Fuel Cell Performance

Effects of Geometrical Parameters of Gas Flow Channels on Polymer Electrolyte Membrane Fuel Cell Performance

Neutron imaging of generated water inside polymer electrolyte fuel cell using newly-developed gas diffusion layer with gas flow channels during power generation

To accelerate the spread use of polymer electrolyte fuel cells (PEFCs), it is essential to increase power density and durability, while reduce costs. We have succeeded in developing an innovative gas diffusion layer (GDL) with gas flow channels (GDLFC+) fabricated on a flat separator that enabled both cost reduction and high performance. In this study, neutron radiography was used to observe the distribution of liquid water during power generation (1–3 A cm−2) of a cell with a size (1.0 cm (W) x 9.7 cm (L)) large enough to evaluate the actual cell. With using our GDLs and interdigitated (comb-shaped) gas flow channels, the distributions of liquid water were quantitatively imaged, influenced by the current density, the relative humidity, the oxygen utilization, and the water repellency of the GDL. The increase in linear velocity of the oxidant gases effectively suppressed the retention of liquid water at the cathode. Even at high oxygen utilization (67%) under continuous power generation for 30 min, the water-repellent GDL effectively made possible the back-diffusion of water over the entire electrode area, contributing not only to a large reduction in diffusion overvoltage but also in Ohmic overvoltage, resulting in high current density and high stability of a PEFC.

Effect of cathode-side gas flow channels section geometry on the removal process of liquid slug in a proton exchange membrane fuel cell

In low operating temperatures, provided water of Proton-Exchange Membrane Fuel Cells (PEMFCs) is discharged in the state of tiny/large droplets, slugs, and semi-slugs, which strongly depends on the flow channels' characteristics. In this study, the discharge capabilities of channels with different height-to-width aspect ratios are inspected using a transient two-phase numerical simulation. The numerical model includes a segment of the gas channel on the cathode side, and the operating conditions are those related to an actual fuel cell application. Results showed that channels with minimum height could lift the initial slug to the upper part 2.16 times faster and immediately form film flow at the corners. For a fixed width, decreasing channel height from 1.5 mm to 0.5 mm, results in 38.3% faster discharge time and a 62.3% increment in the clearance rate of the gas-diffusion layer. For higher channels, the combined effect of shear stress, gravity, and the adhesive forces of hydrophilic walls cannot lift the initial slug continuously and causes it to rupture, distort, and partially spread over the Gas-diffusion layer (GDL) surface, which leads to mass transport limitation for the cell. Furthermore, when the channel width decreases from 1.5 mm to 0.5 mm for a fixed height, the initial slug leaves the computational domain 51.1% faster. Overall, it was found that the smaller dimensions for height and width show superior cell performance regarding faster water removal, clearer GDL surface, and more uniform flow distribution over the entire electrochemical active area. A channel with a cross-section dimension of 0.5 mm × 0.5 mm is suggested as the best channel design among the analyzed cases for maximum efficiency for the cathode-side flow fields of a PEMFC.

An experimental study on gas and liquid two-phase flow in orientated-type flow channels of proton exchange membrane fuel cells by using a side-view method

Proton exchange membrane fuel cells are widely utilized in the areas of aerospace, military and vehicles. Enhancing the reactant transportation and improving water, heat management can effectively increase the electrochemical reaction rate and power output. Orientated-type flow channels have been proved to be effective on improving mass transporting and enhancing performance. In this study, a flow field plate with transparent observation window, whose channel side wall is designed as transparent side-plates, is fabricated to achieve the side-view observation on liquid movement behaviors inside fuel cells. The visualization results of reactant gas and liquid water generation and flowing behaviors in channel regions are observed through the side direction for the first time. Experimental results infer that: orientated-type flow channels having baffles affect droplet generation, moving and shape in gas flow channels, and higher current densities result in more liquid water generation. The baffle downstream region having sudden expanded region slows down droplet moving, and baffle upstream sides accelerates droplet moving. Moreover, the generated heat of electrochemical reaction cannot satisfy maintaining a higher cell working temperature requirement, and an extra heating procedure is required.

Molecular diameters of rarefied gases

Molecular diameters are an important property of gases for numerous scientific and technical disciplines. Different measurement techniques for these diameters exist, each delivering a characteristic value. Their reliability in describing the flow of rarefied gases, however, has not yet been discussed, especially the case for the transitional range between continuum and ballistic flow. Here, we present a method to describe gas flows in straight channels with arbitrary cross sections for the whole Knudsen range by using a superposition model based on molecular diameters. This model allows us to determine a transition diameter from flow measurement data that paves the way for generalized calculations of gas behaviour under rarefied conditions linking continuum and free molecular regime.

Evaluation Criterion of Proton Exchange Membrane (ECPEM) fuel cells considering inserted porous media inside the gas flow channel

• Electrochemical and heat transfer analyses of proton exchange membrane fuel cell. • Introducing a new design using porous media inside the gas flow channel. • Evaluating the power density, voltage, pressure drop and Nu as the outputs. • Define a new parameter “Evaluation Criterion of Proton Exchange Membrane (ECPEM)”. • Training an ANN model to calculate the optimum value of ECPEM to be 78.88. The focus of this study is to evaluate the effects of porous media inside the gas flow channel of Proton Exchange Membrane Fuel Cells (PEMFC) on four different output parameters of voltage, power density, pressure drop, and Nusselt number (Nu) considering the impacts of its thickness, viscous resistance, and current density. Although it is proved that the new design will improve the convective heat transfer, there have not been studies to evaluate the effects of this porous layer on the electrochemical performance and heat transfer simultaneously. The results showed that viscous resistance has by far the highest impact on the power densities in high current densities while thicker inserted porous layer improves the performance. Results also demonstrate that a parameter is needed to consider all these output parameters at the same time, hence the Evaluation Criterion of Proton Exchange Membrane (ECPEM) is defined using artificial neural network (ANN) modeling. Single-objective optimization of the ECPEM is developed using the ANN models to produce 250,000 data. The optimum value of ECPEM was obtained 78.88 in the thickness of 500 μ m and the viscous resistance of 2,111,000 ( 1 m 2 ) while the current density is equal to 0.65 ( A / c m 2 ).

Porous media flow field for polymer electrolyte membrane fuel cell: Depression of gas diffusion layer intrusion, deformation, and delamination

Porous media flow fields have received a growing attention for polymer electrolyte membrane (PEM) fuel cell application due to their multiple benefits, including enhancements in thermal removal, electron conduction, and two-phase flow control. This study numerically investigates the intrusion of the gas diffusion layer (GDL) into the gas flow channel (GFC) and potential delamination at the GDL and microporous layer (MPL) interface upon land compression and evaluates their depressions by adoption of the porous media flow field. Finite element simulation is conducted to predict the GDL deformation and stresses for both porous media and traditional hollow GFCs. The model predictions are compared with other literature data of GDL intrusion/deformation for traditional hollow GFCs. The results show that GDL intrusion may significantly reduce the GFC space and GDL deformation causes a large spatial variation of porosity and permeability of traditional GFCs. Adoption of the porous media GFCs significantly depresses the GDL intrusion and deformation and hence the porosity/permeability spatial variation. In addition, the shear and tensile stresses at the GDL-MPL interface are evaluated, which are major causes for delamination. It is found that both compressive and tensile stresses may be induced by assembly pressure for traditional GFCs. The shear stress can be significantly depressed and tensile stress can be avoided by porous media GFCs, thereby mitigating the risk of GDL/MPL delamination.

Neutron Imaging of Generated Water Inside Polymer Electrolyte Fuel Cell Using Newly-Developed Gas Diffusion Layer with Gas Flow Channels During Power Generation

Neutron Imaging of Generated Water Inside Polymer Electrolyte Fuel Cell Using Newly-Developed Gas Diffusion Layer with Gas Flow Channels During Power Generation

Smart detection of fractures in formation image logs for enhanced CO2 storage

Carbon capture and storage (CCS) has attracted strong interest from industry and the scientific community alike due to the ability of storing CO2 in subsurface reservoirs. Deep saline aquifers may be well suited for the safe and long-term storage given their geological structure. The long term underground storage in saline aquifers depends on variety of interrelated trapping mechanisms in addition to the caprock sealing efficiency. Fractures are commonplace in many geological settings and represent a crucial role for hydrocarbon migrations and entrapment. Fracture impact fluid flow in variety of forms, particularly due to the complexity and varying natures of the fractures, which channel the injected CO2 throughout the reservoir formation. This is especially important for tight gas reservoirs and low permeable cap rock structures whose permeability is primarily characterized by the fault and fractures. This outlines the importance of determining accurately fracture penetration in wellbores for CO2 injection. We present a new deep learning framework for the detection of fractures in formation image logs for enhancing CO2 storage. Fractures may represent high velocity gas flow channels which may make CO2 storage a challenge. The novel deep learning framework incorporates both acoustic and electrical formation image logs for the detection of fractures in wellbores for CO2 storage enhancement and injection optimization. The framework was evaluated on the Pohokura-1 well for the detection of fractures, with the framework exhibiting strong classification accuracy. The framework could accurately classify the fractures based on acoustic and electrical image logs in 98.1% for the training and 85.6% for the testing dataset. Furthermore, estimates of the fracture size are strong, indicating the ability of the framework to accurately quantify fracture sizes in order to optimize CO2 injection and storage.

Influence of Three-Dimensional Geometric Structure and Surface Wettability on Two-Phase Flow Behavior in a Proton Exchange Membrane Fuel Cell Gas Flow Channel: Modeling and Simulation

Influence of Three-Dimensional Geometric Structure and Surface Wettability on Two-Phase Flow Behavior in a Proton Exchange Membrane Fuel Cell Gas Flow Channel: Modeling and Simulation

Influence of Three-Dimensional Geometric Structure and Surface Wettability on Two-Phase Flow Behavior in a Proton Exchange Membrane Fuel Cell Gas Flow Channel: Modeling and Simulation

Influence of Three-Dimensional Geometric Structure and Surface Wettability on Two-Phase Flow Behavior in a Proton Exchange Membrane Fuel Cell Gas Flow Channel: Modeling and Simulation

Numerical simulation of the PEM fuel cell performance enhancement by various blockage arrangement of the cathode serpentine gas flow channel outlets/inlets

In this paper, performance enhancement of polymer electrolyte membrane fuel cells by changing the outlet/inlet configuration of parallel-serpentine flow field is investigated. The geometrical changes of the channel outlets/inlets are designed to amplify the effects of transverse over-rib convection in the gas diffusion and catalyst layers. A three-dimensional and two-phase simulation of the fuel cell performance with four flow fields of parallel-serpentine, serpentine-baffled, serpentine-interdigitated and serpentine-stepped channel is conducted and the results are presented in the form of polarization curves, contours of velocity, oxygen concentration, liquid water saturation, local current density, and the dissolved water content. The results show that the liquid saturation volume coverage is reduced from 0.832 for the parallel-serpentine flow field to 0.514 for the serpentine-baffled flow field. Also, the regions with high concentration of oxygen was improved by 26.7% between these two cases. Due to the increase in oxygen delivery to the catalyst layer and better water removal on the cathode side, the serpentine-baffled, serpentine-interdigitated, and serpentine-stepped flow channel geometries showed a significant increase in performance compared to the parallel-serpentine case. The highest net power has resulted for the serpentine-baffled case so that at a current density of 1.5 A/cm2, a performance increase of 38.5% was achieved compared to the parallel-serpentine case.

Design guidelines for laser powder bed fusion in Inconel 718

Additive manufacturing (AM) has been leveraged across various industries to potentially open design spaces allowing the design of parts to reduce the weight, cost, and integrated design. Over the past decade, AM has sped up fast enough to penetrate various industry offering potential solutions for multiple materials, such as metals, alloys, plastics, polymers, etc. However, challenges lie to best utilize the opened design spaces as current generation engineers are trained to design parts for the conventional manufacturing process. With this lack of design guidelines for the AM process, users are limiting themselves to best utilize the offering made by advanced manufacturing. For aerospace parts, the design freedom of additive manufacturing is attractive mainly for two purposes: for weight reduction through lighter, integrated design concepts as well as for functional optimization of parts aiming at an increase of performance, e.g., by optimizing flow paths. For both purposes, it is vital to understand the material-specific and manufacturing process design limits. In AM, combination of each material and manufacturing process defines the design space by influencing minimum thickness, angle, roughness, etc. This paper outlines a design guideline for the laser powder bed fusion (also DMLM, direct metal laser melting) AM process with Inconel 718 material. Inconel 718 is a superalloy with superior mechanical properties and corrosion resistance at elevated temperatures up to 700 °C and is, therefore, used in several applications including aerospace engine parts. Due to its weldability, the alloy has also been extensively investigated in laser powder bed fusion and other additive manufacturing processes. A comprehensive study is provided both analytically and experimentally suggesting how parts can be designed having critical design features, manufacturing direction/orientation to meet design requirements, design accuracy, and quality. Design features presented include walls, overhangs, bore holes, and teardrop shapes, with their minimal feature sizes and effects on accuracy and roughness of the build parts. For the light-weight design of parts, different concepts such as lattices and stiffener structures are discussed. For gas or liquid carrying flow channels, the geometrical form and size are highlighted. Based on an approach by Kranz et al., design guidelines for Inconel 718 are derived from the experiments and provided in the form of a catalog for easy application.