Internal Pressure Changes Research Articles

Multi-physics coupling numerical simulation of variable porosity in reactive melt infiltration process

Abstract The hypersonic craft necessitates significant advancements in thermal shielding to safeguard against the extreme aero-thermal environments encountered during flight at hypersonic speeds in near space or upon reentry from space. Carbon fiber-reinforced ceramic matrix composites (FRCMCs) have attracted increasingly interesting attention as advanced structural materials for application in thermal protection. The reactive melt infiltration (RMI) process is preferred for the preparation of FRCMCs because of its low cost and short processing time. However, the RMI process includes the complex interplay of melt flow, reaction dynamics, and thermal fields, with existing models failing to accurately predict these processes due to their uncoupled nature and neglect of pore structure changes. This study introduces a coupled model that integrates mass transfer flow, chemical reaction, and heat transfer, incorporating variable pore structures to more accurately evaluate the RMI process. This approach allows for a comprehensive assessment of internal pressure, temperature, and porosity changes during silicon infiltration into porous media, marking an improvement over the previous model. The model has been validated for use in predicting the exotherm of RMI processes. In conclusion, this coupled model presents a promising avenue for enhancing the fabrication of FRCMCs, either considering the melt infiltration from multiple locations in the RMI process or adjusting the pore structure at the infiltration location to larger pores.

Experimental Study on Coal Oxidation and Temperature Rise Under Reciprocating Air Leakage

ABSTRACT Reciprocating air leakage often occurs in the goaf of coal mines because of changes in internal or external pressure. However, its impact on the spontaneous combustion of coal in the goaf is uncertain. Therefore, a comparative study of constant air leakage and reciprocating air leakage was carried out using a self-built system. The results indicate that reciprocating air leakage promotes coal oxidation and produces higher CO levels compared to constant air leakage. Further investigation was carried out to examine the effect of air leakage rate and reciprocating half-cycle (referred to as half-cycle hereafter) on coal oxidation and temperature rise. The results show that there is a linear relationship between resistance and air leakage rate in the coal oxidation heating space; however, the half-cycle length has little effect on resistance. The influence of a fixed air leakage rate on temperature and CO concentration does not always increase, with the maximum value achieved at 1.2 m3/h. Shorter half-cycles result in higher temperatures and CO concentrations. Gradually increasing air leakage rates and shortening half-cycles can promote coal oxidation and temperature rise and lead to higher CO production compared to previous scenarios. Additionally, the effect of using four different air leakage rates or half-cycle lengths is greater than that of using two. These research findings offer a theoretical foundation for preventing and controlling coal spontaneous combustion in goafs under complex air leakage conditions.

Study on CL-20 Initiated by Flyer Driven by Copper Azide

Abstract A simulation model of copper azide microcharge driving flyer initiation microscale CL-20 explosive was established, and the action process of copper azide detonation driven flyer initiation microscale CL-20 explosive was numerically simulated by ANSYS/LS-DYNA fluid-structure interaction algorithm. The internal pressure and velocity changes of the flyer during the detonation of copper azide and the internal pressure change of the CL-20 explosive during the detonation were studied. The results show that the error between the experimental and numerical simulation results of the average speed of the flyer is within 10%. This provides a feasible solution for the study of the micro-explosion detonation mechanism by simultaneously analyzing the explosion process of the multi-physical field change law. The numerical simulation results are consistent with the experimental results, indicating that the established simulation model can be used to simulate the detonation process of CL-20 initiated by a flyer driven by copper azide. The copper azide charge, with a diameter of 1 mm and a charge thickness of 0.6 mm, successfully initiates the detonation of the CL-20 explosive.

Integrating 1D and 3D geomechanical modeling to ensure safe hydrogen storage in bedded salt caverns: A comprehensive case study in canning salt, Western Australia

The viability of hydrogen storage in bedded salt caverns hinges on understanding the geomechanical challenges posed by the anisotropic stress states and complex geology of such environments. This study presents a comprehensive geomechanical analysis focusing on a proposed cavern within the Carribuddy Formation in Western Australia, characterized by its interbedded salt layers. This paper introduces a new geomechanical workflow, encompassing 1D and 3D modeling techniques to provide detailed changes of mechanical properties and stress state in interbedded salt formation allowing to identify the initial optimal operational pressures for underground hydrogen storage. Initial 1D models evaluated mechanical properties and in-situ stresses, while subsequent 3D simulations, enriched by data from neighboring wells, detailed the stress, strain, and displacement responses of the cavern walls to internal pressure changes. The analysis pinpointed an initial safe gas pressure range between 3000 and 4000 psi, attributing this margin to the robust characterization of the mechanical and in-situ stress of the formation. Our findings underscore the significance of high-resolution geomechanical modeling in identifying initial optimal operational pressures for hydrogen storage in salt caverns, ensuring both safety and structural integrity.

Enzyme-powered soft robots: Harnessing biochemical reaction for locomotion

Enzymes have been known as “renewable resources” in cellular processes (in vivo) for more than a century, and are applied in a wide range of fields, including pharmaceuticals and food, particularly through in vitro approaches. This study explored using an enzymatic reaction as the power source for soft robots (here, robots fashioned from silicone). Soft robots powered by pneumatic pressure deform flexible materials in response to internal pressure changes, thereby inducing robot motion. Traditionally, the primary operational principle involved controlling internal pressure using a compressor, creating challenges related to device enlargement, weight, and electric power consumption. Here, as an alternative, we operated a pneumatically driven soft robot by applying the O2 gas generated from decomposition of H2O2 catalyzed by the ubiquitous enzyme catalase. The generation of O2 gas was influenced by the catalase concentration, H2O2 concentration, and the supply-rate of H2O2. Operational tests on a silicone-rubber soft arm suggested controllability of its velocity and number of operational cycles by modifying the enzymatic reaction conditions. Our findings demonstrate the utility of the catalase-catalyzed reaction as a power source for soft robots, thereby showcasing novel prospects for enzyme applications.

Magma intrusion process during pre-magmatic period (2010−2013) of Sinabung volcano as revealed by seismicity of volcano-tectonic and hybrid earthquakes

Sinabung volcano in Indonesia reactivated, with a series of phreatic eruptions, in August and September 2010. These eruptions were followed by various types of magmatic eruption at the summit, including lava dome growth, pyroclastic density currents, lava flow, and vulcanian eruptions, starting in December 2013. Prior to the magmatic eruptions, Sinabung exhibited two sequences of phreatic eruption and an increase in the seismicity of volcanic earthquakes. This study clarifies the progress of magma intrusion during the pre-magmatic period based on the hypocenter distribution, waveform similarity, seismic moment, rupture length, and stress drop for volcano-tectonic (VT) and hybrid earthquakes. It was found that the hypocenters of VT earthquakes are distributed north and northwest of the summit at a depth range of 1–10 km below sea level. Deep seismicity (4–10 km) alternated with shallow seismicity (2–4 km). The last shallow seismicity, from July to mid-December 2013, was different from previous seismicity in terms of higher intensity, as determined from the seismic moment, a temporary increase in the rupture length, and the migration of hypocenters towards the summit. The seismicity of VT earthquakes was altered by a swarm of hybrid earthquakes in mid-December. The hybrid earthquakes were smaller, in terms of seismic moment (mostly <3 × 1010 Nm), than the VT earthquakes. Their hypocenters were concentrated in the shallowest depth range (−0.5 to 1.5 km below sea level) directly below the summit, their source process was repeatable (they could be grouped into six earthquake families), their dominant peak was in a low-frequency range (2.5–4.5 Hz), and they had a relatively low stress drop (<0.15 MPa). This suggests that the swarm of hybrid earthquakes was induced by a frequent repeated fracture of fluid-filled cracks due to the intrusion of magma up to directly below the summit. The transition of the earthquake family and the change in its source parameters, namely an increase in the stress drop prior to the appearance of a lava dome and then a slight decrease, may reflect a gradual change in internal pressure in the hypocentral zone through the magma intrusion process.

Development of Heart Simulator and Analysis of Valve Dysfunction in Tricuspid Regurgitation

Tricuspid regurgitation (TR) resulting from valve abnormalities necessitates precise diagnostic tools and interventions. We employed a simulated heart movement device to examine the performance of heart valve functions and analyzed internal pressure changes to provide a quantitative guide for TR treatment. We developed a simulator capable of replicating the flow profile, mimicking natural heart movements, with sensors installed for measuring internal pressure changes. We conducted an ex vivo experiment on a porcine heart to assess tricuspid valve functionality. An endoscope was installed, with a sensor and endoscopic images to detect abnormalities. TR became evident when the heart rate spectrum exceeded an average of 85.2 bpm (standard deviation, 1.3 bpm) and showed an amplitude higher than an average of 12.3 mmHg (standard deviation, 3.2 mmHg). This critical threshold consistently indicated TR onset. The application of the Pivot-TR attenuated this specific spectral area. We confirmed TR disappearance by reducing the intensity of the Tricuspid Regurgitation Generator or employing the Pivot-TR. The Pivot-TR’s ability to attenuate specific spectral areas associated with TR onset and its effectiveness in restoring normal heart functionality has implications for managing and treating TR, particularly that resulting from age-related structural changes in the heart.

Mathematical modeling of non-stationary deformation of cylindrical structures

The paper investigates the dynamic behavior of a hollow elastic cylinder of finite length, placed in a rigid cylindrical shell, under a sharp change in internal pressure. A numerical solution of a two-dimensional dynamic problem is obtained using the method of spatial characteristics. The stress-strain state of an elastic cylinder is described by a system of hyperbolic equations with two circular conical surfaces as characteristic surfaces. The outer cones correspond to longitudinal waves; the inner ones correspond to transverse waves. The calculations were carried out under various conditions at the ends and the outer (contact) surface of the cylinder and shell. An analysis of the results for a cylinder with load-free ends shows that the absence of gluing the outer surface of the cylinder with the shell leads to a significant increase in the velocities of the points of the cylinder. Under the action of internal pressure, the ends move apart, resulting in a significant increase in the radial velocities of the internal channel. Qualitative patterns of behavior of the structures under consideration, which are widely used in mechanical engineering, on impact-type impacts, can be used to improve and optimize them at the design stage.

Effect of the size of the central atom on the stability of crystalline phases in solid solutions (NH4)3TixSn1-xF7

The effect of a change in internal pressure as a result of partial substitution of the central atom on the realization and stability of the initial and distorted crystalline phases in (NH4)3TixSn1-xF7 solid solutions has been studied. It was found that at a Ti concentration in the range of x = 0.15–0.40, the reconstructive transition Pm-3m ↔ Pa-3 is transformed into a sequence of phase transitions Pm-3m ↔ P4/mbm ↔ P4/mnc ↔ Pa-3. In the (NH4)3Ti0.15Sn0.85F7 solid solution, the first-order phase transition between two cubic phases at T0 = 352 K is characterized by a significant volume jump δ(ΔV/V0) ≈ 1 %, comparable with that in (NH4)3SnF7. An increase of the Ti concentration leads to a strong decrease in the stability of the Pm-3m cubic phase: the first tetragonal P4/mbm phase appears in (NH4)3Ti0.4Sn0.6F7 at T0 = 400 K, which proves the existence of the predicted high-temperature cubic phase in (NH4)3TiF7. In solid solutions, a decrease in birefringence and entropy of phase transitions was observed in comparison with the initial compounds with Sn and Ti as central atoms. The role of critical parameters (unit cell volume, temperature, external pressure) in the formation of cubic and distorted phases is discussed.

Study on the Dynamic Evolution of Bubbles in Oil/Pressboard Insulation

Power transformer may generate bubbles in the transformer oil due to various factors such as internal insulation winding vibration and pressure change. Bubbles distort the spatial electric field, which makes the discharge breakdown along the gas channel, accelerate the discharge breakdown of insulating medium. Therefore, in order to prevent the arc discharge induced by micro bubbles inside the transformer from increasing the risk of transformer combustion damage, it is necessary to conduct in-depth research on the dynamic law of suspended bubbles before insulation breakdown from the source by combining experiments and simulations. In this paper, the bubble dynamic model of needle plate electrode under the multi coupling physical field of transformer is established in terms of the migration and deformation of suspended bubbles in liquid phase. By comparing the migration trajectories of single suspended bubbles obtained from experiments and simulations, the reliability of the model is verified. The variation of velocity component of voltage amplitude and the change of shape stretching of single suspended bubble in power frequency period are simulated, and the fluctuation law of pressure formed by electrostriction force inside and outside the bubble during migration is analyzed. The capacity absorption process of multi bubbles in the strong field region near the needle electrode was simulated. The changes of the surrounding liquid pressure and the spatial electric field distribution during the formation of the gas channel were analyzed, and the internal relationship between the gas channel and the formation of the discharge breakdown was revealed.

Monitoring Internal Oxygen Partial Pressure in YSZ Electrolyte Under Electrolysis Cell Mode Using 4-Electrode System

When solid oxide cells are operated in electrolysis mode, high oxygen pressures can be developed in electrolyte near the oxygen electrode/ electrolyte interface, leading to oxygen electrode delamination. Monitoring oxygen partial pressure in the electrolyte is necessary for the prevention of catastrophic failure in solid oxide electrolysis cells (SOECs). In this study, we applied four-electrode system to fuel electrode-supported SOECs. Four–electrode consists of air electrode, fuel electrode, Pt probe embedded in electrolyte and Pt reference electrode on the electrolyte edge. We measured internal electric potential near the oxygen electrode with respect to the reference electrode using embedded Pt probe. Based on this experimental setup, internal partial pressure of oxygen at the Pt probe location was determined. As tracing changes in internal oxygen partial pressure with varying overvoltage or current density, we investigated the relationship between operating conditions and the tendency of chemo-mechanical failure in solid oxide electrolysis cells.

Reaction mechanism study and modeling of thermal runaway inside a high nickel-based lithium-ion battery through component combination analysis

To diagnose and elucidate thermal runaway accompanying gas evolution of a lithium-ion battery, it is essential to understand the thermal side reactions that lead to thermal runaway inside a lithium-ion battery. It is very useful to make a reliable model that represents these reactions to analyze thermal runaway processes in order to secure battery safety and overcome high costs of large-scale experiments. This study proposes the reaction mechanism and the reaction model through the design of experiments with the combination of battery components such as a cathode, an anode, an electrolyte, and a separator. To develop the reaction mechanism, the peak temperature and calorific value of each reaction are obtained by using a differential scanning calorimeter. The change of mass and produced gas from each reaction are identified by using an online thermogravimetry-mass spectrometer. Based on these measurements, the reaction model is developed by estimating kinetic parameters obtained from the Kissinger analysis. The reaction model exhibits root-mean-square-error of 1.91 mW, 21.79 mW, and 4.53 mW in the electrolyte, the cathode and the anode, respectively, as compared to differential scanning calorimeter results, confirming its high fidelity. The proposed model illustrates the variation of volume fractions of each phase inside a lithium-ion battery to simulate electrochemical performance degradation during thermal runaway stage. The change in internal pressure is also evaluated by using the change in mass and volume of each phase. Based on the mechanism and model derived from this study, it is possible to pinpoint the electrochemical performance degradation and heat generation characteristics during thermal runaway.

Influence of curvature and geometrical parameters on internal pressure in cylindrical Insulating Glass Units

The application of curved glass provides exceptional freedom in the design of modern wavy shapes of building enclosures. The stiffness resulting from curvature has been identified as a remarkable advantage over flat glass, decreasing support requirements, and improving esthetics or increasing spans. However, many constraints arise regarding its design, manufacture, and performance during operation. Due to improved stiffness, curved Insulating Glass Units (IGUs) have a limited ability to equalize internal and atmospheric pressure changes by pillowing, compared to flat IGUs. High internal pressure values may lead to visible visual distortions or failure of the secondary seal. This paper presents the results of experiments, Finite Element (FE) and analytical simulations of flat and cylindrically curved insulating glass units. The study involved seven IGU specimens with 4 mm component panes and a 16 mm cavity. All specimens had a constant width (500 mm) but differed in length (500, 1000 and 1500 mm), and arc radius (two radii of curvature were used, 1500 and 2500 mm). In this study, the main focus was on the influence of geometric parameters on internal pressure in the cavity. The study uses a rarely used technique to simulate varying pressures in the IGU cavity by injecting or withdrawing of a defined volume of gas into/from the cavity.

Variation of peripheral pulse transit time with internal vascular pressure changes induced by arm movement.

Pulse transit time (PTT) and blood pressure (BP) are widely used to quantify arterial characteristics. Arm position influences arterial BP and peripheral PTT. This study aims to quantify the relationship between PTT changes with internal vascular pressure variations induced by the arm moving. With left arm at horizontal position as reference and the right arm moving from 90 to 45, 0, -45, and -90° respectively, PTT difference was calculated by the difference of the pulse foot between right arm and left arm within the same heartbeat. The change in the BP was calculated from the gravitational effect with the measured arm length. Our results showed that the change in PTT with arm elevating is more obvious than that with arm lowering, indicating the different relationship between PTT changes due to the internal BP changes. This can help in understanding the inherent physiological/pathological mechanism of cardiovascular system.

Numerical Simulation on Air-Liquid Transient Flow and Regression Model on Air-Liquid Ratio of Air Induction Nozzle

Air induction nozzle (AIN) has a special Venturi structure that has been widely used in the field of reducing the probability of drift of pesticide droplets and realizing precise application. The present research mainly adopts the method of comparative test and analyzes the difference between AIN and standard fan nozzle. However, the research on internal flow characteristics and air–liquid ratio (ALR) of AIN is very limited. In order to detect the air-liquid transient flow distribution and the influence of the geometric parameter structure of Venturi on the air–liquid ratio in the air induction nozzle, numerical simulation and air-liquid ratio prediction model of AIN combined with TD (Turbo Drop series) type Venturi tubes and ST110 (standard nozzle series) type fan nozzles are used. Based on the VOF (volume of fluid) model and Realizable k-ε turbulence control method, the TD-ST combined AIN is simulated numerically using open input and exit boundary conditions. The results show that the transient flow characteristic of the combined AIN is determined by the geometric structure of the Venturi tube, and the internal velocity and pressure change significantly at the Venturi angle. Under the same ST110 fan nozzle, the size of the larger TD Venturi tube will decrease the air phase content in the air–liquid flow. TD03-ST06 combined AIN has a maximum volume flow of 0.0092 (L/min) under 0.6 MPa. The air–liquid ratio regression model is established by designing the intake volume measurement system. According to this model, the influence law of tube size and spray parameters on the air–liquid ratio can be clarified. After variance analysis, it is proved that this model is suitable for air–liquid ratio prediction of TD-ST combined AIN. This study clarifies the air–liquid coupling law inside AIN and provides some reference for the quantitative analysis of the relationship between the geometric parameters, spray parameters, and the air–liquid ratio.

Posture Estimation by Clustering Pressure Information and Control Implementation for Pneumatically Driven Gait-Assistive Robot

Pneumatic artificial muscles (PAMs) are light and soft, and are expected to be applied to gait assistance robots with multiple actuators on the human body. The PAMs can be used as not only actuators, but also sensors to detect the gait phase by using their deformable bodies whose internal pressure changes in response to the wearer’s gait. However, conventional methods to detect the gait phase by PAMs have targeted single point detection in a gait phase and used for only ON/OFF control of the PAM actuators. In this study, we proposed an algorithm to estimate the postural state of the wearer, especially the state of both hip joints, from the internal pressure information of the PAMs with a small amount of calculation by using clustering method, and succeeded in controlling the PAMs’ pressure continuously based on this algorithm. The effectiveness of the proposed control method was verified through gait-assistive experiments using a treadmill. We measured the electromyogram of the adductor longus muscle under 3 subjects and a one-sided significant difference test was performed. As a result, we confirmed significant differences at the 1% significance level for 2 subjects and at the 10% significance level for the remaining subject, allowing us to evaluate the effectiveness of the proposed PAM control strategy.

Experimental Compaction of a High-Silica Sand in Quasi-Static Conditions

In the compaction process, an uneven densification of the powder through the entire height of the die is a major problem which determines the strength properties of the final product, which vary throughout the entire volume. The aim of this investigation was to determine the distribution of the forming pressure inside the die and to visualise the differences in compaction. To determine the pressure inside the die during the compaction process, the deformation on the die surface was measured by means of strain gauges. However, in order to visualise the densification of high-silica sand during the compaction process, an X-ray tomograph was used, which permits one to visualise the interior of the die. The authors developed an analytical model of how the change in internal pressure influences the change in stresses arising on the outer surface of the die, and, as a result, the friction force. It has been observed that the highest values of pressure as well as the highest concentrations of the loose medium are found closest to the punch and decrease with distance from the punch. Moreover, based on the measurements of deformation, a dependence of the pressure distribution on the value of friction forces was observed, which prompted further analysis of this phenomenon. As a result, tests to determine the coefficient of friction between the die and the loose medium were carried out. This made it possible to describe the pressure distribution inside the die, based on the pressure applied and the height of the die.

Stability of ovalbumin in a blended solvent environment at different pHs: Physicochemical and Laplace transform studies

The protein–sucralose (SL) interaction is gaining significant attention in food and medicinal formulations, because of the unique features of SL in comparison to regular sugars. The main goal of this study is to determine the fluctuation in ovalbumin (OA) conformation in various pH and the presence of the cosolvent SL. Density, ultrasonic velocity, and viscosity, results were used to calculate physicochemical parameters like change in Gibbs free energy, free volume, and internal pressure. The inclusion of SL with OA records a large magnitude of denaturation at acidic pH compared to alkaline pH reflects in the variation of refractive index and change in Gibbs free energy. These results reveal that the inclusion of SL with OA favours the dipole–dipole interactions among the component molecules. Results obtained from Laplace transform studies show that the reduction of diffusion in OA towards SL confirms the denaturation of OA in the presence of SL. Both physicochemical and theoretical analysis suggests that SL makes a larger magnitude of conformational changes in OA at acidic pH compared to alkaline pH.

Design and Analysis of Pneumatic Downforce Regulating Device for No-Till Corn Planter

To avoid the issues of undesired soil compaction and seeding depth variation caused by the downforce fluctuation of the corn no-till planter, the influence of the structural parameters of the air spring on the downforce was researched in this paper, by establishing the gas–solid coupling simulation model of the air spring. The downforce test bench was built to verify the simulation model; the test showed that the vertical output force error of the simulation model was 4.79%, the pitch diameter error was 0.76%, and the pressure error was 5.07%. The cord angle, piston angle and piston diameter were used as influencing factors to carry out single-factor experiments. The influences of structural parameters on downforce were analyzed from four aspects: the vertical output force, the vertical stiffness, the pressure difference and the deformation rate. The results showed that the cord angle reduced the effective area and its change rate during deformation by limiting the radial deformation of the bellow. When the cord angles were 30°, 45° and 60°, the deformation rates were 65.6%, 20.3% and 4.8%, respectively. The cord angle had a positive effect on the vertical output force when the cord angle was in the range of 30~56°, and it had a negative impact in the range of 56~60°. As the cord angle increased, the vertical stiffness decreased. As the piston angle increased, the effective area of the air spring decreased, and the change in internal pressure decreased, reducing its vertical output force and stiffness. The piston diameter had little effect on the internal pressure and deformation rate. It increased the vertical output force and stiffness by increasing the effective area. The structural parameters of the air spring had a significant impact on the stability of the downforce; the structure of the air spring should be optimized according to the downforce demand of the corn no-till planter.

The effect of internal pressure change on the temperature rise and the amount of filling hydrogen of high pressure storage tank

Hydrogen has been considered as a feasible energy carry for fuel cell vehicles, which offers a clean and efficient alternative for transportation. In the currently developed hydrogen compression cycle system, hydrogen is compressed through a compressor and stored in the tank as high pressure. The hydrogen is filled from high pressure station into hydrogen storage system in fuel cell vehicles. In the study, theoretical and simulation are performed by presenting a mathematical model for the temperature rise during filling process in the hydrogen storage tank at the pressure of 50 MPa compressed hydrogen system. For a high-pressure tank (HPT) that can store hydrogen at a hydrogen filling station, the temperature rise of hydrogen with the pressure change during the filling process, the amount of hydrogen filling in the tank, and the convective heat transfer coefficient in the tank were calculated. The calculated temperature was compared with numerical and theoretical methods. Appropriate theoretical formulas were presented through mathematical modeling for changes that occur when high-pressure storage tanks were filled, and hydrogen properties were analyzed using the REFPROP program. 3D modeling was performed for the high-pressure storage tank, and the analysis was conducted under adiabatic conditions. When the pressure was increased to 50 MPa in the initial vacuum state, and when the residual pressure was 18 MPa, it was 25, 50, 75,and 100 MPa, and hydrogen inside the storage tank of the temperature rise and the amount of hydrogen filling were investigated. The results of this study will be useful for the design and construction of compressed hydrogen tank for hydrogen charging system.