Critical Pressure Research Articles

Topological properties of black holes in five-dimensional gauged supergravity

In this paper, we study the topological properties of five-dimensional rotating charged black holes in different ensembles.The topological numbers for the black holes are gotten in the grand canonical and canonical ensembles, which are 1. When the charge and cosmological constant disappear, their topological numbers are 0. When the pressure is lower than the critical pressure, the phase transition exists in the canonical ensemble. However, the phase transition also exists in the grand canonical ensemble when the pressure is higher than the critical pressure and two independent rotational parameters are a=1 and b=−1. This may be due to the fact that the values of the rotational parameters change the supersymmetry of the black hole and lead to the phase transition.

Phase Behavior and Rational Development Mode of a Fractured Gas Condensate Reservoir with High Pressure and Temperature: A Case Study of the Bozi 3 Block

The Bozi 3 reservoir is an ultra-deep condensate reservoir (−7800 m) with a high temperature (138.24 °C) and high pressure (104.78 MPa), leading to complex phase behaviors. Few PVT studies could be referred in the literature to meet such high temperature and pressure conditions. Furthermore, it is questionable regarding the applicability of existing condensate production techniques to such a high temperature and pressure reservoir. This study first characterized the phase behavior via PVT experiments and EOS tuning. The operating conditions were then optimized through reservoir numerical simulation. Results showed that: (1) the critical condensate temperature and pressure of Bozi 3 condensate gas were 326.24 °C and 43.83 MPa, respectively; (2) four gases (methane, recycled dry gas, carbon dioxide, and nitrogen) were analyzed, and methane was identified as the optimal injection gas; (3) gas injection started when the production began to fall and achieved higher recovery than gas injection started when the pressure fell below the dew-point pressure; (4) simultaneous injection of methane at both the upper and lower parts of the reservoir can effectively produce condensate oil over the entire block. This scheme achieved 8690.43 m3 more oil production and 2.75% higher recovery factor in comparison with depletion production.

Investigation of the enhanced cavitation model considering turbulence effects of fuel flow in the injector nozzle holes

The cavitation model is essential in simulating cavitation flow characteristics of injector nozzles, with its accuracy directly impacting simulation precision. This paper developed a quantitative relationship between critical cavitation pressure, turbulent kinetic energy, and shear stress, and introduced a modified cavitation model that considers turbulence effects. A simulation study was conducted on the fuel flow characteristics inside the nozzle of a high-pressure common rail diesel injector with seven nozzle holes. The results indicate that compared to the original model, the cavitation development calculated by the modified model is enhanced at different injection pressures. In terms of axial distribution, cavitation inside the nozzle hole increases, but the impact on cavitation of different intensities varies, with the development of moderate to low-intensity cavitation being promoted, while strong cavitation is inhibited. In terms of radial distribution, the intensity of cavitation on the upper wall inside the nozzle hole increases, which is caused by the higher mass transfer rate near the upper wall at the nozzle hole inlet. As the injection pressure increases from 120 to 240 MPa, the change rate of cavitation volume ratio inside the nozzle holes calculated by the original and modified models increases from 5.1% to 9.7%. It is necessary to use the modified model for the calculations of gas/liquid two-phase flow within the nozzle hole, especially at high injection pressure.

Towards a high-rate operation of contact stabilization process: Challenges of flocculation and floc stability

The high-rate contact stabilization (HiCS) process, a variant of high-rate activated sludge, has gained attention for its superior energy recovery and enhanced biosorption capabilities. The need for efficient energy recovery in HiCS necessitates a high settling efficiency to minimize resource loss due to endogenous sludge consumption. However, the low sludge retention time (SRT) required for HiCS can significantly affect sludge floc stability and flocculation performance, warranting a deeper analysis of the factors influencing these characteristics. This study investigates the impact of SRT reduction on sludge performance, focusing on energy potential, viscoelasticity, and critical pressure. The analysis was conducted using rheological tests, contact angle measurements, zeta potential analysis, Fourier transform infrared spectroscopy, XDLVO theory, and the PARAFAC model. Results indicate that due to the contribution of hydrophobicity, the HiCS system maintained the large flocs morphology of the sludge even when the SRT was maintained for 2d. However, a combination of aerobic microbial activity, high concentrations of loosely bound extracellular polymeric substances, and the presence of the filamentous bacterium Thiothrix contributed to reduced flocculation performance.

Knox-Saleem kinetic performance limits in liquid chromatography—A contemporary tutorial

The kinetic performance limits evaluated by Knox and Saleem in 1969 are reevaluated herein. Published 55 years ago, the original study did not address several key features of contemporary chromatography. The following features of chromatographic analyses were assumed in the source:•The static operations (isothermal isobaric GC, isocratic isothermal isobaric LC).•The columns packed with discrete particles.•The columns were optimized to deliver the smallest plate height.Additionally, currently obsolete parameters and notations were used complicating comprehension of the original study.In this tutorial focusing mostly on LC, the original Knox-Saleem study is extended to gradient elution LC, to the columns with arbitrary structure (open, packed, pillar array, monolithic, etc.) and to suboptimal operations – all expressed in contemporary notations. The study is based on previously published basic structure-independent equations of column kinetic performance.Some conclusions of this tutorial are different from previous ones. It has been concluded herein that at any pressure (no matter how low) any separation performance (no matter how high) can be achieved as long as the analysis time is acceptable. This seems to contradict with Knox-Saleem statement suggesting that there is “the critical pressure below which a separation number S cannot be achieved however much time is available.” Similar statement was also previously known from Giddings (1962): “critical pressure, pc, the inlet pressure below which a [required, LB] separation can never be obtained”.

Effects of internal intervention in tubes on shock wave attenuation, formation and propagation of flame during high-pressure hydrogen release

Experiments on the impacts of the combination of fin structure and expansion chamber on shock wave attenuation, hydrogen ignition, and flame characteristics during high-pressure hydrogen release were carried out. The fin is a four-edged platform hollowed out on all sides. The inflated upper and lower tube walls are located 85, 95, and 105 mm away from the nickel burst disk. With the incident shock wave traveling through the fin, the reflected shock and the superposition of multiple reflected shock waves appear, and the reflected shock wave intensity can equal that of the release pressure. The decrease of the incident shock wave intensity behind the fin leads to the decrease of the non-uniformity of the mixed layer temperature, further causing the decrease of the flame propagation velocity. The presence of fins increases the probability of ignition in the fin region and the critical release pressure for ignition is significantly lower than that in the barrier free tube, mainly because the fin inside intensifies the hydrogen/air mixture, resulting in a lower minimum ignition energy required for self-ignition. Furthermore, the decrease of flame propagation velocity leads to the increase of hydrogen consumption inside the tube and the decrease of shock overpressure outside.

Experimental Investigation of Post-Dryout Heat Transfer with R-134a at High Pressures

An experimental study of post-dryout (PDO) heat transfer in the coolant R-134a was performed in a vertical round tube with upward flow. Experiments were conducted at high pressures from 28.4 bars up to 39.8 bars, corresponding to a reduced pressure of 0.7 to 0.98, respectively. Mass flux was varied in the interval of 300 to 1500 kg/m2∙s, and overall equilibrium vapor quality was between −1.88 and 4.89. Depending on the settings of the experimental parameters, the heat flux was varied from around 11 to 100 kW/m2. The uniformly heated tube had an inside diameter of 10 mm and a heated length of 3000 mm. In total, more than 10 000 PDO data points were obtained. In the PDO region, the wall temperature distributions had similar behavior across the pressure range. At the occurrence of dryout, the wall temperature suddenly increased until it reached a peak. For higher mass flux, the wall temperature decreased after reaching the peak, followed by a second temperature increase with a lower slope. For lower mass flux, the wall temperature kept increasing after the dryout point. The temperature peak after the dryout point was smaller at higher pressure, while this effect was even stronger near the critical pressure. Likewise, the vapor quality corresponding to the first peak shifted to even lower values with increasing pressure. Furthermore, it was found that at increasing pressure and at increasing mass flux, the dryout location and the total temperature distribution shifted toward lower vapor qualities. In addition, several PDO correlations were assessed, and a new correlation for high-pressure conditions was developed and compared with the results of the existing ones.

Serial manual bolus irrigation leads to critical intrarenal pressures during flexible ureterorenoscopy - time to abandon this manoeuvre.

To characterise the effect of solitary and serial manual bolus irrigations on intrarenal pressures (IRPs) and observe the clinical consequences. A pressure guidewire was used for IRP measurement during routine flexible ureterorenoscopy for management of renal stone disease, including manual bolus irrigation when required to maintain vision. The fluid bolus was either as a solitary manual bolus or a series of manual boluses in quick succession. The pre-bolus, maximal and difference between IRPs were calculated. A total of 50 procedures in 46 patients were analysed. In all, 68 solitary manual boluses and 38 serial manual boluses were observed to have been undertaken during these procedures. After a solitary manual bolus, the median (standard deviation [SD], range) increase in IRP was 22.4 (34.0, 0.1-160.8) mmHg, and the mean (SD, range) maximum IRP was 46.1 (41.7, 15.8-190.0) mmHg, with elevated IRPs persisting for a median (range) duration of 19 (4-66) s. After serial manual boluses, the median (SD, range) rise in IRP was 58.4 (64.7, 10.2-242.84) mmHg and the mean (SD, range) maximum IRP reached was 100.8 (69.7, 34.3-303.5) mmHg. The elevated IRPs endured for a median (range) of 42 (9-121 s; P < 0.01 in all comparisons), suggesting a much greater elevation of IRP with instances where serial bolus irrigation was undertaken. Manual bolus irrigation, both solitary but particularly serial boluses, produces significant rises in IRP and could logically result in pyelovenous backflow and sepsis. We suggest that this manoeuvre should be avoided to reduce complications during ureterorenoscopy.

Ultrafast spectroscopy of coherent phonons across the pressure driven insulator to metal phase transition in V2O3

Nowadays, materials science is moving towards the understanding and control of materials in nonequilibrium states by making use of perturbative techniques to investigate their dynamical responses. From this perspective, the use of ultrashort light pulses seems to be a relevant approach as it can selectively address different degrees of freedom in solid-state systems and more particularly electrons. Such a method can help to decipher the physical phenomena arising from electronic correlations and complements a more conventional methodology where the phase diagrams of materials are investigated at thermodynamical equilibrium. Here, we combine femtosecond optical spectroscopy and a high-pressure setup to monitor the ultrafast out-of-equilibrium photo response of a V2O3 thin film across the pressure driven insulator-to-metal transition. The experimental results demonstrate the possibility to use the spectroscopy of coherent phonons as a thermodynamical phase marker in V2O3 thin films. In addition, the frequency behavior of the ultrafast coherent phonon mode (A1g character) seems to reflect the manifestation of a strong coupling between the lattice and electronic degrees of freedom near first-order transition lines with a pronounced drop in frequency around the critical pressure. Published by the American Physical Society 2024

Experiment and Numerical Prediction on Shock Sensitivity of HMX–Based Booster Explosive with Small Scale Gap Test at Low and Elevated Temperatures

In order to analyze the effect of temperature changes on the shock initiation performance of HMX–based booster explosive, which consists of 95% HMX and 5% FPM2602 by weight, a temperature calibration test of acceptor was designed. The temperature changes in the booster at low and elevated temperatures under the constraint of steel sleeve were obtained. Based on the temperature calibration results, polymethyl methacrylate (PMMA) was selected as gap material to conduct a small scale gap test (SSGT) of HMX–based booster under different temperature conditions. The corresponding critical gap thickness was tested. Based on SSGT results at different temperatures, the shock initiation processes were simulated by adjusting parameters of ignition and growth reactive rate model. The critical gap thickness and critical initiation pressure of HMX–based booster at different temperatures were numerically predicted. By combining SSGT experimental data and simulation results, the attenuation law and fitting prediction formula of the critical initiation pressure of HMX–based booster were proposed. The mechanism of temperature effect on the shock sensitivity of HMX–based booster explosive was analyzed. The research results indicate that the critical gap thickness of HMX–based booster gradually increases with the rise in temperature, and the critical initiation pressure gradually decreases during the shock initiation process under the heating temperature conditions. In addition, the simulation results show that the heated HMX–based booster under steel constraints becomes more sensitive at high temperatures (&gt;120 °C), while the cooled booster is more insensitive, but its critical initial pressure does not change significantly between 88 °C and 120 °C. The experimental and numerical prediction results are important for the shock initiation safety and design of an insensitive booster explosive.

The effect of porous non-metallic balls on detonation propagation in hydrogen–oxygen mixtures

In this study, the influence of porous non-metallic balls on the dynamics of detonation propagation in hydrogen–oxygen mixtures is studied in stainless steel tubes with square cross-sections. The effect of the length and thickness of the balls is considered in detail. Four pressure transducers are used to record the detonation time-of-arrival, and the average velocity of detonation propagation is calculate. The smoked foil technique is performed to register the detonation cellular structures. The results indicate that increasing the filling length and thickness of the balls leads to a significant increase in velocity loss, critical pressure, and re-initiation distance during detonation propagation. Two propagation modes are observed near the critical pressure. In sub-critical mode, the detonation wave is attenuated and failed eventually, propagating to the end of the tube in the form of a low-speed deflagration wave. In super-critical mode, the detonation propagation can be promoted by inducing a vertical transverse wave generated by the detonation wave passing through a group of small balls. It is worth noting that the increase in filling thickness of the small balls leads to a greater velocity loss compared to the increase in filling length. However, an increase in the filling length will cause the detonation wave to undergo a longer and more sustained weakening process as it passes through the small balls, thereby resulting in a longer re-initiation distance and a lower average velocity over a short distance after re-initiation. By increasing the filling length of the small balls to 312 mm, the transition of the detonation wave from multi-head detonation to double-head detonation can be observed, and then successfully turns into stable detonation. However, when filling double-layer small balls, even in super-critical conditions, the attenuated detonation wave cannot achieve re-initiation over a short distance.

Evaluation and Application of Wellbore Stability of Deep Oil Wells in the Southern Margin of Junggar Basin

The stability of the oil well wellbore is a prerequisite for selecting the optimal completion method. In this paper, based on experimental testing and theoretical models of rock mechanics parameters in deep oil reservoirs, the in situ stress parameters of deep oil wells are accurately predicted. On this basis, a full life cycle assessment model for wellbore and perforation casing stability was established, and the effects of pressure depletion and changes in the production pressure differential on wellbore stability and casing stability were analyzed. The research results indicate that as the formation pressure decreases, the critical collapse pressure difference around the wellbore significantly decreases. The greater the production pressure difference, the more likely the wellbore is to become unstable. Under the original formation pressure coefficient, if there is no casing, the critical failure pressure difference of the wellbore wall is 55 MPa. After cementing and perforation, when the casing is uniformly stressed and the formation pressure drops to a coefficient of 0.83, the casing will not be damaged even when the wellbore is completely emptied. At this time, there is still a certain safety production pressure difference in the perforated formation. This study can effectively guide the optimization of well completion and safe development in deep oil reservoirs.

H2 diffusion in cement nanopores and its implication for underground hydrogen storage

Understanding the transport and adsorption characteristics of hydrogen (H2) in calcium silicate hydrate (C-S-H) nanopores is critical to minimize the leakage risks from cement in the wellbore region during underground H2 storage (UHS). However, the critical physiochemical properties of H2 in C-S-H nanopores remain inadequately understood. In this work, we perform molecular dynamics simulations to comprehensively investigate the H2 distribution and diffusion properties in the C-S-H nanopores, considering the crucial parameters of temperature, pressure, and pore size. We evaluate how the density distribution, mean squared displacement (MSD) and diffusion coefficient of H2 evolve with variations in these crucial parameters by comparing H2 properties in C-S-H nanopores with those of bulk H2. We show that H2 molecules are prone to adsorb on C-S-H walls and form a high-density adsorption layer due to strong interactions between C-S-H walls and H2. We find that the confinement of C-S-H nanopores significantly limits the diffusion of H2, leading to smaller diffusion coefficients. Moreover, the diffusion of H2 demonstrates pronounced anisotropic characteristics, with H2 diffusing significantly faster in the direction parallel to C-S-H walls than in the direction perpendicular to the C-S-H walls. We demonstrate that there is a critical pressure, beyond which the diffusion coefficient of H2 parallel to C-S-H walls is close to that in the bulk phase and remains stable. We also show that the impact of nano-confinement gradually diminishes with increasing pore size. Under a given temperature/pressure condition, once the pore size exceeds a threshold, the H2 diffusion coefficient in the C-S-H nanopore is close to that of bulk H2. Our results provide valuable insights into H2 diffusion and adsorption in the C-S-H nanopores at the molecular level, which is critical to assessing and minimizing H2 leakage risks from cement in the wellbore.

Aerosol deposition on face masks in an open environment during inhalation

The aerodynamics of aerosols and their deposition on face masks play a critical role in determining the effectiveness of respiratory protection. While existing studies have focused on the risks associated with aerosol dispersion during exhalation, little attention has been paid to aerosol aerodynamics in an open environment, where aerosols can circumvent masks, during inhalation. This is because mask performance has primarily been evaluated by the particle filtration efficiency in closed pipe setups, which do not account for the aerodynamics of aerosols around the wearer's face. In this study, we conduct experiments in an open environment to investigate the aerosol flow around a face mask and the aerosol deposition under varying inhalation pressures. Our results indicate that an aerosol flow near a mask surface behaves like a viscous flow, stagnating within the range of human inhalation. Within this range, we find that the amount of aerosol deposited can be predicted by modifying existing aerodynamics theory. Using a theoretical model, a critical inhalation pressure is identified at which water aerosols begin to penetrate through a mask. Finally, we propose the aerosol circumvention efficiency as a new metric to assess mask performance in open environments by taking into account the effects of aerosol circumvention.

Research on the initiation and wavefront evolution of diverging cylindrical detonations of acetylene and oxygen mixtures

The present study focuses on fundamental research about the transition from a planar detonation to a cylindrical detonation and the propagation of the diverging cylindrical detonation. We aim to figure out the mechanism of the transition and propagation of the diverging cylindrical detonation by analyzing the cellular pattern and critical initial pressure. The findings highlight that the successful detonation in a cylindrical chamber via transition through a straight channel is predominantly influenced by diffraction at the corners and the successive continuous reflections between the front and rear walls. Depending on the initial pressure, the initiation modes exhibit characteristics of subcritical, critical, and supercritical three-stage processes. Sustained propagation of cylindrical detonations necessitates increasing the number of cells to match the growth rate in the front region. Experimental investigations reveal two distinct modes of cell number increase: mild and violent. In the case of the former, cell number increase predominantly occurs on a scale of two to three times the characteristic cell size of the Chapman-Jouguet detonation. In contrast, a decaying Mach stem undergoes twisting and evolves into local kinks, leading to the development of new triple-wave points. The latter mode typically occurs near the limit, where cell increase primarily arises from randomly occurring local explosions, and operates on a scale of ten times the characteristic cell size or the chamber diameter. In addition, a numerical study of two-dimensional fundamental problems abstracted from the experiment is conducted to help interpret experimental results and reveal more about the physics of the problem.

Analysis of rapid decompression failure in polymer liner of Type IV hydrogen storage vessels using a novel fluid–solid coupling model

Type IV vessels have been developed for hydrogen storage systems, but the rapid decompression failure during the decompression process can lead to the collapse of the liner, significantly reducing the lifespan of the vessels. This study aims to investigate nonlinear buckling behaviors and collapse mechanisms of polymer liner in Type IV hydrogen storage vessels. Considering the intrinsic coupling between hydrogen gas depletion and mechanical behavior of vessels, a fluid–solid coupling model was proposed using the fluid cavity techniques and HyperMesh. Results indicated that the pressure difference generated on the liner is the primary cause leading to the polymer liner collapse. The critical pressure difference significantly increases with the thickness of the liner, while it decreases nonlinearly with the increase in void defect size. Parametric sensitivity analysis highlighted the depth of initial void defect and the liner thickness as two significant influencing factors in the critical decompression rate.

Prediction of the non-equilibrium condensation characteristic of CO2 based on a Laval nozzle to improve carbon capture efficiency

The supersonic separator is considered as a more efficient and environmentally friendly technology within the field of decarbonization. The flow state of the vapor and the operating environmental conditions are significant factors which affects the separation efficiency. The effect of the inlet pressure (subcritical, near-critical, supercritical), temperature (supercritical), and the outlet back pressure on the CO2 non-equilibrium condensation flow characteristics is numerically calculated. The results show that when the pressure is higher or the temperature is lower, the non-equilibrium condensation process is promoted and the formation of droplets is more stable. The nucleation interval increases with the pressure increases. The peak nucleation rate increases with the temperature decreases. The condensation shock wave is weakened and the condensable area is reduced with the back pressure increases, resulting in the liquid mass fraction significantly decreases. The critical condensation back pressure reflects the ability of the vapor to resist back pressure shocks during the condensation process. The effect of inlet pressure, temperature, and expansion angle on the critical condensation back pressure is analysed. The condensation shock wave is enhanced by increasing the pressure, expansion angle, and decreasing the temperature, the vapor has a stronger ability to resist the influence of back pressure.

Sand Production Prediction and Management Using a One-Dimensional Geomechanical Model: A Case Study in NahrUmr Formation, Subba Oil Field

Sand production in sandstone reservoirs is a complex problem for oil and gas companies. This problem can damage downhole equipment and surface production facilities. This paper presents a sand production case and quantifies sand risks for the NahrUmr formation located in Subbaoilfied.The risk of sanding or rock failure is commonly observed during production phases as well as drilling operations. A (1D) mechanical earth model was created using wireline log data and core data for estimating the formations mechanical properties.The extrapolation method is utilized for vertical stress prediction, whereas pore pressure and static Young’s modulus were calculated using Slowness Eaton method and John Fuller correlation respectively. The poro-elastic model was used to determine horizontal principal stresses and hydrocarbon intervals susceptible to sand production issues.The purpose of this study was achieved using Tech-Log software. Sand onset intervals are firstly predicted as an open hole using ten methods: Loading factor (LF), Critical drawdown pressure (CDDP), B-index, schlumberger (Sc), Elastic combination index (Ec-index), Interval Transit-Time (DTc), Total porosity method (PHIT), unconfined compressive strength (UCS), Shear modulus to bulk compressibility ratio (G/Cb), and shear failure method. Approximately ten methods refer to the same intervals that can produce sand. Secondly, sand depths were predicted by representing the well according to what actually existed as a cased hole by calculating the critical drawdown pressure (CDDP), which is calculated at various depletion rates (0%, 15%, 25%, and 35%) in order to measure the effect of reservoir pressure depletion on sand production. The results show that as the rock strength is increased, the amount of sand-free drawdown and depletion becomes larger. Also, a single-depth analysis was conducted for problem intervals, indicatg a sandwillproducefromdepth of 2527.7 m under certain conditions. Therefore, it is necessary to install sand control equipment in this well.

Numerical modeling of the impact of a large scale waterfall on a solid plate

Recent hydroelectric power plant safety developments have necessitated detailed studies on dam spillway operations, especially during emergency water discharge scenarios such as overtopping. This paper presents a numerical investigation of a 10-meter high waterfall impinging on a solid plate using two-phase flow models. Our approach integrates a coupled Eulerian–Lagrangian Spray Atomization (ELSA) model with an Interface Capturing Method (ICM) to simulate the complex multiphase flow and atomization processes. Our model proficiently mapped the velocity and turbulence within the pre-impact region. To refine the accuracy of the impact pressures, we isolated this zone and implemented the Injection–Reinjection strategy, a novel numerical procedure for this type of configuration. The study reveals significant insights into the dynamic interactions of water packets with the dam structure, highlighting critical impact pressures that can influence dam stability and integrity. Our results, compared against experimental data, demonstrate the effectiveness of the modeling strategies in predicting the fluid behaviors and the subsequent pressures exerted on structural components.

Effect of temperature on the symmetrization of AlOOH hydrogen bonds

Hydrogen bonding symmetrization of water-bearing minerals plays a key role in the water cycle of the deep Earth. The lower mantle is a high-temperature and high-pressure environment, and in this study a classical molecular dynamics simulation of the δ-AlOOH hydrogen bond symmetrization process is carried out using a deep learning potential model. Calculation the length of the HO bond reveals that AlOOH undergoes hydrogen bond symmetrization when the pressure reaches 9 GPa. The volume thermal expansion profile of AlOOH shows an anomalous phenomenon of negative correlation between phase transition pressure and temperature. The radial distribution functions gOH(r) and gHH(r) show the asymmetry of hydrogen bonding at 8 GPa and indicate the critical conditions for hydrogen bonding symmetry at 10 GPa. Calculations of the O1O2 bond lengths show that the critical pressure required for hydrogen bond symmetry increases with temperature. Our simulation results provide some insight into the hydrogen bonding symmetry of water-bearing minerals in the deep Earth’s.