Uniform Pressure Distribution Research Articles

Custom-made ocular prosthesis: enhancing the iris position of post-evisceration patient

Individuals who have impaired vision as a result of illness or injury may have their appearance improved with the use of a prosthesis eye. To construct realism, symmetry, and a glance that appears natural, it is necessary to duplicate the size and arrangement of the iris with accurate pinpoint accuracy. This is crucial for developing a realistic-looking gaze. Eye loss has a profoundly debilitating impact on the mental state of the person who has suffered it. The ultimate goal of every ocular prosthesis procedure is to facilitate the patient's reintegration into society while preserving their healthy visage and self-esteem. This article provides a clinical report on the rehabilitation of a patient whose left eye had suffered intraocular foreign body damage following evisceration. A closer fit between the prosthesis and the ocular base tissue can be achieved with custom-made acrylic resin ocular prosthesis that are sized and shaped to fit the ocular socket of the patient. This close fit results in a more uniform distribution of pressure compared to factory stock eye prosthesis and is more cost-effective than stock eye prosthesis

Human-Centered Design and Manufacturing of a Pressure-Profile-Based Pad for Better Car Seat Comfort

A car seat’s function is to support, protect, and make passengers and drivers feel comfortable during a trip. A more uniform pressure distribution and a larger contact area usually provide less discomfort. Consequently, the seat pan’s material and geometry play an essential role in the design process. A shaped pad was opportunely designed and realized, starting from the pressure distributions between the buttocks and the seat pan; pressure data were acquired during an initial experiment involving 41 people, representing a wide range of percentiles. The shaped pad was compared with a standard one by building a special seat with an interchangeable internal pad and testing the standard and the new seat; the second experiment involved 52 people that tested both seats. The tests were conducted to assess comfort (33 subjects were asked to be seated for 1 min each) and discomfort (19 subjects were asked to be seated for 15 min each); during the tests, pressure distribution and contact area data were gathered. The results showed that, for both tests, about 80% of the participants, among which 100% of the female sample, preferred the shaped seat pan pad. Even if the material was exactly the same, the shaped pad seemed to be softer, more comfortable, and more suited to the body’s shape than the standard one. The design methodology was demonstrated to be very useful for granting a more uniform pressure distribution and a wider contact area, i.e., higher comfort and less discomfort.

Analysis and Reflection on the Green, Low-Carbon, and Energy-Saving Design of the Super High-Rise Building

Shanghai Tower has become a new landmark of Shanghai. In the current trend advocating green building and energy efficiency, considerations of wind loads and thermal characteristics of the perimeter structure of Shanghai Tower are crucial. This paper conducts comparative simulation studies on the wind environment of Shanghai Tower using Ecotect software, and stress analyses and thermal simulations of the perimeter structure using ANSYS software. The study compared three buildings’ surface wind pressure distributions using models with equal-volume and circular cross-sections. We found that the unique exterior design of the Shanghai Tower results in a more regular and uniform distribution of wind pressure on its surface compared to both circular and square planar models, with a lower average wind pressure value. In addition, the stress analysis results indicate significant differences in deformation and stress distribution between the windward and leeward sides. Enhancing the bending moment detection of the peripheral structure and optimizing the layout of detection points are recommended. Thermal simulation results show excessive heat conduction flux in winter conditions, suggesting optimization using passive energy-saving methods such as light-sensitive thermal insulation materials during winter. This research is a reference for designing other super-tall buildings prioritizing low-carbon energy efficiency and structural safety.

Enabling Uniform and Accurate Control of Cycling Pressure for All‐Solid‐State Batteries

AbstractAll‐solid‐state batteries are emerging as potential successors in energy storage technologies due to their increased safety, stemming from replacing organic liquid electrolytes in conventional Li‐ion batteries with less flammable solid‐state electrolytes. However, all‐solid‐state batteries require precise control over cycling pressure to maintain effective interfacial contacts between materials. Traditional uniaxial cell holders, often used in battery research, face challenges in accommodating electrode volume changes, providing uniform pressure distribution, and maintaining consistent pressure over time. This study introduces isostatic pouch cell holders utilizing air as pressurizing media to achieve uniform and accurately regulated cycling pressure. LiNi0.8Co0.1Mn0.1O2 | Li6PS5Cl | Si pouch cells are fabricated and tested under 1 to 5 MPa pressures, revealing improved electrochemical performance with higher cycling pressures, with 2 MPa as the minimum for optimal operation. A bilayer pouch cell with a theoretical capacity of 100 mAh, cycled with an isostatic pouch cell holder, demonstrated a first‐cycle Coulombic efficiency of 76.9% and a discharge capacity of 173.6 mAh g−1 (88.1 mAh), maintaining 83.6% capacity after 100 cycles. These findings underscore the effectiveness of isostatic pouch cell holders in enhancing the performance and practical application of all‐solid‐state batteries.

High-Throughput Multi-Principal Element Alloy Exploration Using a Novel Composition Gradient Sintering Technique

This work demonstrates the capabilities and advantages of a novel sintering technique to fabricate bulk composition gradient materials. Pressure distribution calculations were used to compare several tooling geometries for use with current-activated, pressure-assisted densification or spark plasma sintering to densify a gradient along the long dimension of the specimen. The selected rectangular tooling design retains a low aspect ratio to ensure a uniform pressure distribution during consolidation by using a side loading configuration to form the gradient along the longest dimension. Composition gradients of NixCu1−x, MoxNb1−x, and MoNbTaWHfx (x from 0 to 1) were fabricated with the tooling. The microstructure, composition, and crystal structure were characterized along the gradient in the as-sintered condition and after annealing to partially homogenize the layers. The successful fabrication of a composition gradient in a difficult-to-process material like the refractory multi-principal element alloy system MoNbTaWHfx shows the utility of this approach for high-throughput screening of large material composition spaces.

Numerical investigation on the hydrodynamic and conversion performance of a dual cylindrical OWC integrated into a caisson-type breakwater

The hydrodynamic performance of an integrated oscillating water column (OWC) combined with a cylindrical caisson type breakwater was investigated. A three-dimensional numerical wave tank was established to simulate the overall energy conversion performance and hydrodynamics of the integrated system with the software Star-CCM+. The developed Computational Fluid Dynamics (CFD) model was initially verified with the published physical results and numerical results derived from an analytical solution. The effects of the structural geometry and the pneumatic damping of the PTO system on the wave absorption and power conversion efficiency of the proposed device were investigated using this developed model. Based on this proposed numerical model, the velocity of the air flow, the corresponding air pressure characteristics in the air turbine nozzle and chamber zone were discussed. The results indicate that this proposed half-open land based OWC is adapted to absorb shorter nearshore waves, characterized by dimensionless wave number kd approaching 1.49. Furthermore, a larger opening inlet zone for this proposed OWC would shift the resonant corresponding kd to higher wave frequencies, while lowering the opening inlet could help to increase the power extraction efficiency for long waves. The peak hydrodynamic efficiency is observed at a ratio of OWC inlet width to diameter B/D of 0.97, which is approximately six times larger than that at B/D = 0.5. The inclusion of an impulse turbine yields a more uniform pressure distribution within the central chamber and effectively mitigates wave reflection for smaller incident waves, with maximum efficiency achieved using 37 blades. The property of the efficiency mitigation with insufficient certain intake depth of the wave chamber should be avoided for system design.

Improving the cleaning uniformity of rectangular flat pleated filter with pulse-jet airflow by the new type of intensive injection nozzle

The rectangular flat pleated filter is widely used in the industrial field due to its compactness and high efficiency in dust removal. However, due to the large number of folds and the extremely small gaps between folds, achieving complete cleaning is a key technical challenge. A new type of injection nozzle has been proposed, the effects of different injection nozzles on the static pressure acting on the inner wall of the rectangular flat pleated filter were investigated through multi-condition cleaning experiments and industrial powder coating verification experiments. The performance of the uniform pressure distribution can be enhanced by 17.67% compared to the traditional circular nozzle, especially 88 × Ф2.4 mm injection pipe, which has the optimum cleaning performance at 0.2 MPa and 20 mm. The relationship between the comprehensive pressure and number of the injection nozzles is put forward: Pζ=0.2n2−21.59n+1322.02, which is also applicable to traditional circular nozzle. The filtration velocity has more apparent impact on the cleaning efficiency of the filter, while the influence of gas-solid concentration is not significant. According to the requirements of different industrial scenes, the filtration velocity and the gas-solid concentration can be appropriately reduced within a certain range to make the filter more efficient.

Bio-inspired sinusoidally-waved flow fields with exchange channels to enhance PEMFC performance

Wave-shaped structures inspired by cuttlefish fins have been applied to the design of flow fields for proton exchange membrane fuel cells (PEMFCs). However, the wave structures often cause high parasitic power. Herein, we intend to address this issue by introducing exchange channels (ECs) between neighboring wave channels. First, the performances of bio-inspired sinusoidally-waved flow fields (BSWFFs) of different sinusoidal parameters are compared to identify the optimal sinusoidal structure. Subsequently, ECs are introduced into BSWFFs with the optimal sinusoidal structure to obtain EC-BSWFFs, and EC-BSWFFs with different numbers of ECs are compared. The introduction of ECs improves the distribution of reactant gases, pressure distribution, water management and reduces parasitic power density. Specifically, the maximum net power density of the single-cell PEMFC with EC-12 is enhanced by 10.26% compared to that of the conventional parallel flow field. Moreover, as the number of ECs in EC-BSWFFs increases, the uniformity of pressure distribution gradually increases and the pressure drop becomes smaller, suggesting a balance between performance and durability. Therefore, this work affords valuable insights to solve the difficulties of excessive pressure drop and inhomogeneous reactant distribution for waved flow fields.

Numerical model for simulating the hydraulic parameters of the aeration system ensuring equal oxygenation of the compost heap

The aim of the work was to develop a mathematical model using equations of fluid mechanics that describe the dynamics of air flow in a part of the compost aerating system integrated with a stationary reactor. The results of the simulation show that adjusting the flow resistance along the entire length of the compost aerating duct, depending on the distance from the connection of the duct with the fan's pressure conduit pipe through gradually increasing the air outflow area by increasing the number of repeatable gaps, yields a uniform pressure distribution above the grate. The process parameters used for computation were relevant to composting a subscreen fraction separated from mixed municipal waste using 80 mm mesh screen (Fr<80 mm) under real conditions. Microsoft EXCEL 2010 software and STATISTICA version 13.3 by StatSoft were used for numerical and statistical analysis of the test results. The research results are presented in four tables and five figures and discussed in the text of the article. During tests performed in real conditions, various variants were tested for reactor filling level and air outflow active surfaces in subsequent grate parts (Fc (i)). It was found that the target waste layer thickness i.e. 3.0 m and Fc (i) changes, in accordance with the values of the developed model, result in a stable pressure distribution pd, amounting to 1506 Pa and 1495 Pa at the grate front and end part.

On the sound field of a resilient elliptical disk in an infinite baffle.

A resilient elliptical disk has zero mass and stiffness and is driven by a uniform pressure distribution rather than uniform velocity as would be the case for a rigid disk. It can represent the diffraction of a plane wave through an elliptical aperture in an infinite rigid screen of zero thickness as well as provide an idealized model of a loudspeaker of the electrostatic or planar magnetic type. Using the Fourier (Hankel) Green's function in cylindrical coordinates, together with the monopole Kirchhoff-Helmholtz boundary integral, rigorous analytical formulas are derived for calculating the surface velocity distribution, radiation admittance, on-axis pressure, and directivity pattern of an elliptical resilient disk in an infinite baffle and these are plotted over a range of normalized frequencies. The directivity is compared with that of a resilient circular disk and asymptotic low-frequency approximations are derived for the radiation resistance, reactance, and on-axis pressure.

An Innovative Clinical Evaluation Protocol after Total Ankle Arthroplasty: A Pilot Study Using Inertial Sensors and Baropodometric Platforms

Background: Total ankle arthroplasty (TAA) has grown in popularity and indications, with encouraging results over time. Today, preoperative and postoperative evaluations are mainly performed using clinical test and diagnostic imaging, but there is a deficiency in objectively evaluating the biomechanics of the foot and ankle, which serve as the functional markers for monitoring the effectiveness and outcomes of surgery. Inertial measurement units associated with plantar pressure measurements may provide an accurate and reliable method of evaluating function through the analysis of gait and ankle joint mobility. The aim of this study was to introduce an innovative technology, to assess its accuracy and feasibility compared to standard clinical assessment methods and to objectify kinematic outcomes in patients with end-stage ankle OA before and after TAA surgery. Methods: A consecutive series of eight patients with symptomatic end-stage osteoarthritis and treated with TAA was prospectively evaluated using clinical scores (AOFAS, MOxFQ, VAS, SF-36, 17-IFFI), physical tests (FPI, ALT), plantar pressure measurements with FLEX EPS/R2 Letsense® baropodometric platform, gait analysis and wearable sensors-based ankle motion and kinematic outcomes using Wiva Science inertial sensors by Letsense®. Data were collected preoperatively and 4 months after surgery. Results: All PROMs exhibited statistical significance in improvement from pre- to postoperative periods, except for one. Physical examinations showed no significant changes of the foot shape and alignment. Plantar pressure analyses revealed no significant changes in static and dynamic evaluations, but a more uniform distribution of plantar pressure was observed between the two periods. Inertial sensor parameters demonstrated no significant differences, except for a significant reduction in stride length and step length for the operated foot after surgery. Conclusions: Gait analysis using inertial sensors and plantar pressure measurements offer ease of handling, cost effectiveness, portability and swift data reading, making them highly appealing for widespread clinical use. Integrating these tools into the routine assessments of patients with TAA holds promise for advancing precision of treating this condition and our depth of its understanding, contributing to more comprehensive and insightful patient care.

Exploring the Mpemba effect: a universal ice pressing enables porous ceramics.

Piezoceramics with global porosity and local compaction are highly desired to exploit the combination of mechanical and electrical properties. However, achieving such a functional combination is challenging because of the lack of techniques for applying uniform pressure inside porous ceramic green parts. Nature provides many examples of generating strong forces inside the macro and micro channels via the state transformation of water. Inspired by these phenomena, we present a technique of "ice and fire", that is, water freezing (ice pressing) and high-temperature sintering (fire), to produce ideal porous piezoceramics. We introduce a new compaction method called the "ice pressing method", which manipulates liquid phase transition for compaction. This method has several advantages, including uniform pressure distribution, a wide pressure range, high effectiveness, and selective freezing. It can generate an ultrahigh pressure of up to 180 MPa on the piezoceramic green skeletons in minutes while retaining their functional pore structures. By exploiting the Mpemba phenomenon, we further accelerate the compaction procedure by 11%. The first ice-pressed and second fire-consolidated lead zirconate titanate (PZT) ceramics are highly densified and exhibit an outstanding piezoelectric response (d33 = 531 pC N-1), comparable to conventional pressed bulk counterparts and 10-20 times higher than those of unpressed materials. The novel ice pressing method breaks the limitation of lacking a compaction technique for porous ceramics. The versatile and effective ice pressing method is a green and low-cost route promoting applications in sensors, acoustics, water filtration, catalyst substrates, and energy harvesting.

Functionalized Electrode Additive for Simultaneously Reinforcing Chemo‐Mechanical Properties of Millimeter‐Thick Dry‐Electrode for High‐Energy All‐Solid‐State Batteries

AbstractVoids are widely disseminated in a powder when mixed, and hence the typical dry‐electrode preparation method yields a sparse dry‐electrode because the external pressure applied to the surface of the mixed powder is not evenly distributed. Consequently, particle cracking and void remnants appear in the electrode after calendaring. This study introduces a practically applicable bi‐functionalized electrode additive to simultaneously reinforce the chemo‐mechanical properties of millimeter‐thick dry electrodes. The agyrodite Li6PS5Cl solid electrolyte and lithium difluorophosphate (LiPO2F2) additive have different sizes, as demonstrated by their densification from their elaborate bimodal structure, which is densely packed. Because the additive is filled into the interparticle voids in the electrode sheet during electrode fabrication, a decrease in electrode cracking after calendaring is possible because of the uniform distribution of external pressure. Hence, a thin, highly ionic/electronic‐conductive electrode can be constructed by the addition of LiPO2F2 additive. Furthermore, during the formation, the active material surface‐contacted LiPO2F2 promptly produces a surface layer comprising LiF and LixPFy. Thus, the addition of LiPO2F2 further reduces the degradation of Li6PS5Cl solid electrolytes. As a result, the LiPO2F2 additive simultaneously improves the electrochemical and physicochemical properties of millimeter‐thick dry‐electrodes for high‐energy all‐solid‐state battery systems.

Long-term bolt preload relaxation and contact pressure distribution in clamping anchorages for CFRP plates

Clamping anchorages are commonly used to anchor carbon fiber reinforced polymer (CFRP) plates, and the anchoring performance is significantly impacted by bolt preload. This research presents experimental and numerical investigations of long-term bolt preload relaxation in clamping anchorages for CFRP plates. First, a compression test was conducted to obtain the elastic modulus in the thickness direction of CFRP plates. Subsequently, four types of relaxation tests (single bolt, planar and curved anchorage, external load effect, and thickened anchorage) were conducted, considering the effects of the number of CFRP plates, anchorage type, external load, and initial preload. The elastic interaction during the tightening process was also investigated. The contact pressure distribution was simulated through the finite element method, which is in good agreement with the experimental results obtained from pressure papers. To fit relaxation test results and predict million-hour relaxation, different theoretical models were employed. The results indicate that the number of CFRP plates is crucial to preload relaxation, and the presence of CFRP plates introduces strong elastic interactions between bolts in the anchorage. Preload relaxation also increases under external loads and with the increase in initial preload. Curved anchorage has less bolt preload relaxation in the long term under external loads. Additionally, thickened anchorages have a more uniform contact pressure distribution due to the improved pressure diffusion mechanism.

A new mathematical model to evaluate the effect of load inclination on aircraft shelter’s foundations

Aircraft shelter is a structure or a reinforced hanger that has many uses in military aspects. It is used to protect military aircraft from different dangers such as enemy chemical attacks. Also, it provides housing, permitting aircraft maintenance and it can be storage for different weapons. therefore, optimum design of aircraft shelter is of a great importance. It may take several shapes to be suitable for its usage. It can be made from concrete, steel or composite materials. The foundations of an airplane shelter must be designed as best as possible. Design objectives are greatly impacted by the contact pressure between the earth and the foundation surface. Classical method in design assumes maximum uniform linear distribution of pressure under contact surface of footing. So, considering real contact pressure has a great interest for many authors. In this article, a new analytical method is proposed to study the effect of moments and load inclination on the design of rectangular isolated footing. The model proposed takes into consideration the real soil pressure. A parametric study was conducted and data obtained from classical model were larger than those from proposed model. Seven Rectangular isolated footings were designed using traditional method and proposed method. The proposed method is more economic since it provides less concrete dimensions. Results obtained from the new model were compared with FEM and achieved reasonable agreement.

A new experimental setup to investigate the cyclic response of soft soils under induced earthquakes

Energy technologies, which work by extracting or injecting fluids in the ground, such as geothermal energy systems or underground liquefied gas storage, may induce seismic events, see e.g., [1]. In the Netherlands, induced earthquakes are continuously recorded from the Groningen gas field, with the largest magnitude ever recorded of ML 3.6 at Huizinge. Even though the magnitude of these events is not high, compared to natural earthquakes, damage to the built environment is still caused because of the shallow depth of the events and site amplification, especially where soft soils are encountered [2]. Proper quantification of the induced seismic risk requires better understanding of the response of soft soils to these repeated short events, covering a range of frequencies from 1 to about 20 Hz. This motivated the development of a new advanced dynamic equipment to experimentally investigate the coupled response of soft organic clays and peats from the typical deltaic areas of the Netherlands.
 Direct simple shear (DSS) apparatuses are preferred usually to investigate the soil behaviour under cyclic and dynamic loading. Among them, a number of multi-directional DSS setups have been developed to investigate the soil behaviour under multidirectional loading [3, 4, 5, 6, 7, 8]. Applying multi-directional loading to soil specimens in the laboratory is a keystone for elucidating the cyclic and dynamic soil response, as several studies have shown that the cyclic and post-cyclic response of soils is affected by multiple loading directions [6, 9, 10, 11, 12]. However, traditional DSS devices have a number of shortcomings, which are inherited by multi-directional DSS devices. The main deficiency of the DSS device is that the shear stress acting on the lateral side of the specimen cannot be controlled, and hence, a homogeneous stress state cannot be achieved, in spite of the common assumptions. Lateral stresses cannot be measured either in traditional setups, which leaves a knowledge gap on the stress state and the stress path of the sample.
 In addition, the majority of laboratory element tests are performed by imposing “slow” undrained cyclic loads, to try to guarantee uniform water pressure distribution within the sample, for the sake of interpretation and modelling. However, seismic events encompass much higher loading frequencies than typically available, with loading rate effects playing a key role in the response of soft soils such as organic clays and peats. In order to fully understand the cyclic behaviour of soft soils, “fast” cyclic tests are crucial.
 The innovative multidirectional shear device, developed in the section of Geoengineering at TU Delft (Cyclic-Dynamic shear simulator for Organic Soft Soils, CYC-DOSS), was designed to overcome some limitations of previous equipment. The underlying idea is to abandon the homogenous stress-strain state assumption and monitor the response with local sensors, which allows conditioning a numerical back-analysis of the test data. The new device shown in Figure 1 is characterised by (1) servo-hydraulic control; (2) multi-directional loading in 3 axes; (3) bender elements to measure both P-wave and S-wave velocity; (4) fully controlled cell pressure and back-pressure; and (5) possibility to reproduce the full acceleration time history of seismic events. The device is capable to apply loading frequencies up to 25Hz and a wide variety of multidirectional cyclic loading patterns. The apparatus is equipped with advanced sensors, also developed at TU Delft, including local pressure, displacements, and accelerations devices. The sensors are installed to reduce a priori assumptions on the soil response, better interpret the experimental results as a small-scale physical model and further investigate in depth the soil response under a variety of cyclic loading histories. The experimental information from the setup will be used to develop and calibrate an advanced bounding surface constitutive model for soft organic soils.

Life cycle integrated flow simulation for hydraulic fracturing horizontal wells in shale gas reservoirs

The distribution of matrix pressure and water saturation during the fracturing and shut-in period significantly impacts shale gas production. However, traditional numerical simulations primarily focus on the production period, often overlooking the impact of fracturing and shut-in on the seepage field and production rates. This study uses the dual-porosity/dual-permeability-embedded discrete fracture model (DPDK-EDFM) to characterize matrix mixed wettability and the natural/hydraulic fracture geometry. A multiscale numerical simulation model is constructed to encompass the whole life cycle of shale fracturing, shut-in, and production. The model provides a comprehensive understanding for considering the changes in rock properties and the diverse migration mechanisms. Subsequently, the life cycle model is used for sensitivity analysis on capillary pressure, shut-in time, and fracturing fluid volume. The findings demonstrate that (1) capillary pressure strongly impacts flowback rate. As surface tension increases from 0 to 72 mN/m, the flowback rate decreases from 113.00% to 68.25%. (2) The shut-in time strongly affects the uniformity of pressure distribution. (3) The fracturing fluid volume is directly proportional to the rise in formation pressure. This innovative model provides a robust framework for simulating and analyzing the seepage field behavior of shale gas reservoirs throughout the life cycle. Furthermore, through a comprehensive investigation of the main controlling factors, this study provides valuable insights into the efficient development of shale gas reservoirs, carrying both theoretical and practical significance.

A Proton exchange membrane water electrolysis cell model for analyzing the effects of liquid water supply characteristics on cell performance

Proton exchange membrane water electrolyzers (PEMWE) have significant potential for green, high-purity hydrogen production. This study proposes a pseudo-two-dimensional cell-level model that considers all the physical characteristics involved in water electrolysis (WE), such as electron transport in the electrodes, proton transport in the membrane electrode assembly (MEA), water transport between the anode and cathode, gas diffusion in the porous electrodes, two-phase transport in the porous electrodes, and flow channel (FC), including the channel pressure drop and heat conduction across the cell. Liquid water dispersion at the electrode/channel interface is proposed based on a geometrical analysis of the bubble patterns inside the anode channel. The model was validated against the experimental data. The simulation results showed the effects of the liquid water supply characteristics on the cell operation, demonstrating that uniform water, temperature, and pressure distributions on the cell are required for higher performance. Furthermore, efficiency maps with operating constraints under different conditions provide basic guidelines for determining the optimum point of PEMWE operation. The proposed model is appropriate for extensive analysis of physical phenomena inside the PEMWE and rapid simulation for cell optimization.

Study of Contact Pressure Distribution in Bolted Encapsulated Proton Exchange Membrane Fuel Cell Membrane Electrode Assembly

The distribution of contact pressure on the Membrane Electrode Assembly (MEA) significantly affects the performance of a Proton Exchange Membrane Fuel Cell (PEMFC). This paper establishes a PEM fuel cell model to investigate the impact of bolt load and its distribution, sealing gasket hardness, and size on the magnitude and distribution of contact pressure on the MEA during assembly. Thermal–mechanical coupling is employed to simulate the thermal effects resulting from chemical reactions under operational conditions. The findings reveal that there is an extremum of pressure uniformity in the range of 5000 to 6250 N for bolt loads. When the average bolt load is lower than this extremum, altering the distribution of the load can effectively enhance the uniform distribution of contact pressure. Stiffer gaskets reduce the contact pressure on the MEA while increasing the pressure on the gasket itself, resulting in reduced deformation. A rational matching relationship among gaskets, Gas Diffusion Layers (GDLs), and seal grooves is proposed. During operational conditions, thermal effects decrease the sealing performance and also impact the magnitude and distribution of contact pressure on the MEA. These outcomes provide significant guidance for the assembly and performance evaluation of PEMFCs.

Combustion characteristics of a dual-mode ramjet engine with a supersonic aerodynamic ramp injector

The combustion characteristics of a liquid-hydrocarbon-fueled dual-mode ramjet combustor with a new injector, including a cavity-type flame holder, were investigated under inflow conditions of M 1.8, total pressure of 590 kPa, and total temperature of 930 K. The newly proposed injector uses various injection methods, such as an aerodynamic ramp, pre-mixing chamber, barbotage gas, and supersonic nozzle. The aerodynamic ramp injection method consists of four injectors with inclination angles of 40° and 80° and toe-in angles of 30° and 60°. This was adopted to increase the penetration height of the fuel while minimizing the total pressure loss. A pre-mixing chamber with a barbotage gas injection device was employed to enhance atomization and fuel–air mixing. In addition, a contoured Mach 3 supersonic nozzle was used to obtain a higher momentum through acceleration. For performance comparison, a combustor with a pre-mixing chamber and barbotage gas was used in the same manner, but injected by a cylindrical nozzle with a 15-degree of transverse angle. The ignition was initiated by a torch ignitor installed on the cavity floor with hydrogen pilot fuel. Once combustion stabilized, only the main liquid fuel was supplied. The Mach number was calculated using quasi-one-dimensional analysis based on the measured wall pressures and inlet conditions. The results showed that the model combustor with two types of injectors operated in the ramjet mode, which was subsonic near the flame holder and supersonic at the exit of the combustor. At the combustor outlet, the total pressure according to the equivalence ratio of 0.25 to 0.56, the newly proposed injector case showed a higher pressure level, steep increase, and more uniform pressure distribution than the baseline injector from the measurement result of the pitot pressure rake at the combustor exit.