High Pressure Conditions Research Articles

Crystal structure stability and phase transition of celsian, BaAl2Si2O8, up to 1100 °C / 22 GPa

Celsian (BaAl2Si2O8) is an important component of aluminosilicate-based ceramics, which is widely used in high temperature/high pressure process. However, limited data available on its high pressure (HP)/high temperature (HT) behavior and HT studies were based on multi-component samples only. Here we present data on crystal structure stability and phase transformation processes of celsian studied under extreme conditions (up to ∼22 GPa/∼1110 °C) using in situ X-ray diffraction. Under HP conditions celsian undergoes three phase transitions: at the pressures below 10 GPa the main changes in the crystal structure of celsian associated with the changes in the coordination Ba-centered polyhedron (celsian-II and celsian-III), whereas at higher pressures AlO4 tetrahedra transforms into AlO6 octahedra (celsian-IV). Though the HP behavior of some isostructural compound has been studied before, the HP transformation of celsian is not similar to any previously studied mineral or synthetic compound. Celsian demonstrate stability and low thermal expansion coefficients (αV = 12 × 10−6 °C−1) in the studied temperature range.

Fracture propagation characteristics of water and CO2 fracturing in continental shale reservoirs

Exploring the adaptability of CO2 and water-based fracturing to shale oil reservoirs is important for efficiently developing shale oil reservoirs. This study conducted fracturing experiments and acoustic emission (AE) monitoring on the Jurassic continental shale. Based on high-precision computed tomography scanning technology, digital reconstruction analysis of fracture morphology was carried out to quantitatively evaluate the complexity of fractures and the stimulation reservoir volume (SRV). The results show that the fracturing ability of a single water-based fracturing fluid is limited. Low-viscosity fracturing fluid tends to activate thin layers and has limited fracture height. High-viscosity fracturing fluid tends to result in a wide and simple fracture. A combination injection of low-viscosity and high-viscosity water-based fracturing fluid can comprehensively utilize the advantages of low-viscosity and high-viscosity fracturing fluids, effectively improving the complexity of fractures. CO2 fracturing is adaptable to Jurassic shale. The breakdown pressure of the supercritical CO2 (SC-CO2) fracturing is low. Branch fractures form, and laminas activate during SC-CO2 fracturing due to its high diffusivity. Under high-temperature and high-pressure conditions, the aqueous solution formed by mixing CO2 with water can promote the formation of complex fractures. Compared with water-based fracturing fluid, the complexity of fractures and effective stimulation reservoir volume (ESRV) increased by 8.7% and 47.6%, respectively. There is a high correlation between SRV and ESRV, and the proportion of AE shear activity is also highly correlated with the complexity of fractures. The results are expected to provide better fracturing schemes and effectiveness for continental shale oil reservoirs.

Proper orthogonal decomposition of wall-bounded high-pressure transcritical fluids

This study explores the principal modes of high-pressure transcritical channel flow from direct numerical simulation data. The four cases investigated correspond to CO2 at high-pressure conditions (P/Pc=1.5) confined between a cold/bottom wall (T/Tc=0.8−0.95) and a hot/top wall (T/Tc=1.1−1.4); Pc and Tc correspond, respectively, to the pressure and temperature of the critical point. The bulk velocity ranges between Ub=0.5−1.0 m/s with corresponding bulk Reynolds numbers of Reb≈1000−2500. The four cases considered are first characterized into laminar and turbulent regimes, followed by an analysis of energy decay using singular value decomposition. This method allows us to identify the most energetic modes of velocity, temperature, and specific isobaric heat capacity for the laminar and turbulent cases considered. The results reveal that fewer modes are needed to represent the hydrodynamics compared to the thermodynamics of the system. The findings also highlight that the pseudo-boiling region, prevalent in high-pressure transcritical systems, disrupts the coherent structures formed (especially) in the hotter region of the flow. Finally, a correlation analysis between the most energetic modes shows an interdependence between velocity and specific isobaric heat capacity modes when conditioned to focus solely on the pseudo-boiling affected regions. This correlation underscores the complex interplay between hydrodynamic and thermodynamic variables in such high-pressure transcritical environments.

Study on corrosion behavior of impeller of oil pump with CO2 crude oil

Abstract CO2 was one of the key factors that caused serious corrosion of petroleum equipment and facilities. Aiming to address the problem of serious pitting corrosion in the impeller of an oil pump in a CO2 flooding field, immersion, and electrochemistry experiments were comprehensively analyzed in this paper. The results showed that the corrosion rate of FV520B steel increased exponentially with the increase of pipeline transport pressure and flow rate (R2>0.9), and the potential shifted negatively. With the increase of pipe pressure, the corrosion directivity of the specimen surface gradually disappeared, showing a distinct pitting area and a comprehensive corrosion area. This was due to cavitation under high pipe pressure conditions.

Effect of Hydrate Saturation on Triaxial Shear Mechanical Properties of Methane Hydrate-Bearing Sediment

Abstract As a clean energy source, natural gas hydrate resources are essential to the development of energy in the twenty-first century. However, the degree of consolidation of the hydrate reservoir is low, and complex accidents such as wellbore instability, reservoir collapse, and gas production leakage will be caused if improperly exploited. The laboratory employs a self-developed triaxial shear test equipment that operates under high pressure and low temperature conditions. This equipment is specifically designed to determine the mechanical parameters and strength characteristics of methane hydrate bearing sediment (MHBS) samples. It is used to create water-saturated hydrate deposits with varying levels of saturation. The synthesis of MHBS samples with varying saturations is achieved by precisely regulating the amount of water. The saturation of MHBS is then determined and confirmed by the utilization of the “water content method” and the “gas collection method.” Triaxial shear tests are conducted on MHBS to examine the impact of hydrate saturation on the mechanical parameters and strength behaviours of MHBS. The experimental findings demonstrate that the presence of hydrate crystals enhances the robustness of the depositing medium. The stress-strain curves of MHBS have a hyperbolic shape, indicating strain hardening features. The stress-strain curves may be categorized into three distinct stages: the initial elastic deformation, followed by a slow shift to the initial yield deformation, and ultimately leading to strain hardening. As axial strain rises, the behaviour of the MHBS transitions progressively from elastic deformation to plastic deformation. The shear strength and initial yield strength of MHBS enhance with higher hydrate saturation. The reason for this is that as the hydrate saturation rises, the influence of hydrate crystals on the enhancement of sediment strength becomes more pronounced. However, the initial yield strain of each MHBS sample is between 0.5% and 1.5%, and the difference is not significant. When the hydrate saturation rises gradually, the cohesion of MHBS enhances. Nevertheless, the hydrate saturation has a very minor impact on the internal friction angle.

Modeling drilling fluid density at high-pressure high-temperature conditions using advanced machine-learning techniques

The management of oil and gas wells under high-pressure high-temperature (HPHT) conditions is a significant challenge in the oil industry, leading to increased operational and maintenance costs. One method for calculating the density of drilling fluids involves the use of sensors placed at the bottom of the well, which measure the fluid density in real time. Despite their accuracy, these sensors are costly and perform suboptimal under HPHT conditions. In the present study, seven robust machine-learning models, namely generalized regression neural networks (GRNN), wavelet neural networks (WNN), and cascade forward neural networks (CFNN) combined with two different training algorithms containing Levenberg-Marquardt and Bayesian regression (CFNN-LM and CFNN-BR), respectively, and support vector regression (SVR) models combined with three optimization algorithms containing farmland fertility algorithm (FFA) grasshopper optimization algorithm (GOA), and particle swarm optimization (PSO) were utilized to predict mud density at HPHT conditions. Moreover, mathematical models were developed using a group method of data handling algorithm (GMDH) to predict this parameter. WNN, SVR model combined with (PSO, GOA, FFA), CFNN, and GRNN algorithms have better adaptability than other artificial intelligence models. These models can improve performance by changing the data and different situations. Also, these models can better resistance against noisy data, which means that they can show good performance compared to uneven and discontinuous data. To this aim, using 986 experimental data of drilling fluid at HPHT, including 117 water-base fluid data, 440 colloidal gas aphron fluid data, 219 oil-base fluid data, and 210 synthetic fluid data the drilling fluid density was modeled. Input parameters including temperature, pressure, initial mud density, and volume fraction of solid content were used for modeling. The results showed that the volume fraction of the solid content as an input variable improves the accuracy of intelligent models in this work. Based on average absolute percent relative error (AAPRE) the best outcomes for predicting the mud density without the input parameter of solid fraction were observed by the PSO-SVR model with an AAPRE of 0.5569%. Following, the GOA-SVR, WNN, and FFA-SVR delivered the next best results with AAPRE of 0.5860%, 0.5786%, and 0.6148%, respectively. Moreover, with the input parameter of solid fraction, the WNN model demonstrated the highest accuracy among all models, achieving an AAPRE of 0.2475%. Also, the correlation developed using the GMDH method based on input parameters of initial mud density, temperature, and pressure yielded satisfactory outcomes and can provide precise and swift estimates. Eventually, Sensitivity analysis revealed that initial mud density had the highest impact on mud density. Lastly, the leverage analysis indicates that most data points are trustworthy based on experimentation, with only a few falling outside the PSO-SVR and WNN models' scope.

Characterizing nodule motion in abyssal environments induced by double-row jets: A machine learning approach

Double-row hydraulic collectors are extensively utilized for deep-sea polymetallic nodule harvesting. Understanding the movement behavior of particles within the flow field is crucial for evaluating the efficiency collection system and guiding the design of deep-sea hydraulic collectors. This study first investigates the settling characteristics of particles in various deep-sea environments to assess the effects of high-pressure and low-temperature conditions on particle motion. Subsequently, the motion and force characteristics of particles under different double-row jet parameters were measured and analyzed in the laboratory using high-speed imaging. The results indicate that ambient pressure has a negligible effect on particle motion when the ambient temperature is considered. Particle is mainly lifted in an irregular spiral path by the turbulence of the upper fountain. The lifting height or force of a particle in the vertical direction is positively correlated with the frequency of horizontal fluctuations and inversely related to the average amplitude of these fluctuations. Finally, a neural network was constructed to predict the particle motion characteristics, demonstrating strong generalization and providing a reference for further use of artificial intelligence in extracting physical information of particles from the jet field. This study offers potential benefits for optimizing the design of the double-row jet collectors.

Experimental study on the optimization and stability of methane foam systems under high-temperature, high-pressure, and high-salinity conditions

Experimental study on the optimization and stability of methane foam systems under high-temperature, high-pressure, and high-salinity conditions

From Darcy to turbulent flow: Investigating flow characteristics and regime transitions in porous media

This research addresses the flow characteristics within a porous medium composed of a monolayer of closely packed spheres, spanning from viscous-dominated to turbulent flow regimes. In the first part of this paper, the turbulent flow characteristics at a 30 MPa pressure drop within the domain are presented. The results are averaged across different cross sections between the inlet and outlet. In the second part of the study, simulations are conducted with pressure drops, ranging from nearly 0 to 100 MPa. The analysis finds distinct flow patterns within the domain and provides estimations for the permeability and the inertial term coefficient. Moreover, the transition from Darcy to non-Darcy and turbulent flow is achieved through the use of different criteria. The specified geometry is suitable for validating and calibrating simplified discrete element method models coupled with computational fluid dynamics. The main goal of this research is to produce a reliable benchmark to figure out the challenge of limited experimental data concerning fluid flow characteristics in densely packed granules specially subjected to high pressure conditions. To do this, representative specimens are designed, accurate simulations are conducted, and precise assessments of the results are carried out.

High-pressure phase transition in clinochlore: IIa polytype stabilization

Abstract Structural variations of natural clinochlore with pressure have been studied by in situ single-crystal X-ray diffraction (XRD) in a diamond-anvil cell in the pressure range 0–20 GPa at room temperature. High-resolution XRD data allowed for the identification of a polytypic phase transition at about 9 GPa. Around 4.32(5) GPa, the unit-cell parameters exhibited a significant deviation from linear behavior, particularly the c and β values, abruptly interrupted when the phase transition occurs. XRD patterns showed a drastic reduction of diffuse scattering due to the stabilization of the high-pressure structure, suggesting that the atomic reorganization of the layers led to a disorder reduction. The phase transition showed complete reversibility during the experiment. Ab initio structural refinements identified the transition as polytypic, from the initial IIb-4 triclinic polytype (space group C1) to the IIa-1 monoclinic structure (space group C2/m), with unit-cell parameters a = 5.2058(6) Å, b = 9.0208(4) Å, c = 13.560(7) Å, β = 97.34(3)°. The latter was theoretically derived in the 1960s as the least stable chlorite polytype but has never been observed in natural chlorites. The phase transition also has a significative effect on the bulk modulus, with a reduction from K0 = 81.2(13)t to K0 = 56.0(6) GPa for the high-pressure structure. An isothermal run at 600 K from ambient pressure to 14 GPa showed the same phase transition at 7.8(5) GPa. Its occurrence at lower pressures suggests a negative P/T slope for the transition. Therefore, at high-temperature and high-pressure conditions compatible with impact phenomena, the polytypic phase transition could prevent chlorite from early destabilization and dehydration.

Ignition and Combustion Characteristics of Alternative Fuel under High-Temperature and High-Pressure Conditions

Ignition and Combustion Characteristics of Alternative Fuel under High-Temperature and High-Pressure Conditions

Preparation and Evaluation of Physical and Chemical Properties of Resin Plugging System Suitable for Formation Plugging of Malignant Lost Circulation.

Lost circulation is one of the important problems that restricts the speed and efficiency of oil and gas drilling and production. In this study, a resin plugging system was successfully developed for lost circulation formation. The resin plugging system showed excellent performance under high temperature and pressure conditions. The experimental results showed that the compressive strength of the resin plugging material can reach 9.23 MPa after curing, which is significantly higher than that of the traditional polymer gel material. The resin material can achieve effective curing in the temperature range of 60 °C to 100 °C, and the curing time decreases with the increase of temperature and only needs 3.46 h at 140 °C. The microstructure results showed that the resin material can form a chain or three-dimensional network structure after curing, which can effectively increase the toughness and strength of the cured plugging layer. Infrared and thermogravimetric analysis further confirmed the thermal stability of the chemical bonds in the material, and the initial decomposition temperature was about 241 °C, indicating that it had good thermal stability at about 300 °C. In addition, the effects of curing temperature, salinity, and drilling fluid pollution on the properties of the resin plugging agent were also investigated. The results showed that curing agent dosage and curing temperature are the key factors affecting curing time, while salinity and drilling fluid pollution affect the curing strength and overall properties of the materials. After adding 20% KCl polysulfonate drilling fluid, the compressive strength of the consolidated body decreased to 4.55 MPa. This study can provide an efficient and reliable plugging solution for malignant loss formation.

On the Polymorphism of Cu2V2O7: Synthesis and Crystal Structure of δ-Cu2V2O7, a New Polymorph

Single crystals of the new modification of copper pyrovanadate, δ-Cu2V2O7, were prepared using the chemical vapor transport reaction method. The crystal structure (monoclinic, P21/n, a = 5.0679(3), b = 11.4222(7), c = 9.4462(6) Å, β = 97.100(6)°, V = 542.61(6) Å3, Z = 4) was solved by direct methods and refined to R1 = 0.029 for 1818 independent observed reflections. The crystal structure contains two Cu sites: the Cu1 site in [4 + 2]-octahedral coordination and the Cu2 site in [4 + 1]-tetragonal pyramidal coordination. There are two V5+ sites, both tetrahedrally coordinated by O atoms. Two adjacent V1O4 and V2O4 tetrahedra share the O4 atom to form a V2O7 dimer. The crystal structure of δ-Cu2V2O7 can be described as based upon layers of V2O7 dimers of tetrahedra parallel to the (001) plane and interlined by chains of the edge-sharing Cu1O6 and Cu2O5 polyhedra running parallel to the a axis and arranged in the layers parallel to the (001) plane. The crystal chemical analysis of the three other known Cu2V2O7 polymorphs indicates that, by analogy with δ-Cu2V2O7, they are based upon layers of V2O7 groups interlinked by layers consisting of chains of CuOn coordination polyhedra (n = 5, 6). The crystal structures of the Cu2V2O7 polymorphs can be classified according to the mutual relations between the Cu-O chains, on the one hand, and the V2O7 groups, on the other hand. The analysis of the literature data and physical density values suggests that, at ambient pressure, α- and β-Cu2V2O7 are the low- and high-temperature polymorphs, respectively, with the phase transition point at 706–710 °C. The β-phase (ziesite) may form metastably under temperatures below 560 °C and, under heating, transform into the stable α-phase (blossite) at 605 °C. The δ- and γ-polymorphs have the highest densities and most probably are the high-pressure phases. The structural complexity relations among the polymorphs correspond to the sequence α = β < γ < δ; i.e., the δ phase described herein possesses the highest complexity, which supports the hypothesis about its stability under high-pressure conditions.

Dissolution kinetics and heterogeneous evolution of dolomite with different pore structures

Mesogenetic dissolution is a critical process in the evolution and preservation of pore spaces in carbonate reservoirs. While limestone dissolution has been extensively studied, there is a lack of research on the dissolution kinetics of dolomite reservoirs, particularly regarding differences in dissolution mechanisms and heterogeneity evolution across various pore structures. This study aims to investigate diagenesis processes and heterogeneity evolution patterns in dolomites with different pore structures by simulating reservoir dissolution using organic acids generated during kerogen cracking. Flow system dissolution experiments were conducted on four dolomites with varying pore structures in 0.2% acetic acid under high-temperature (T = 40–160 °C) and high-pressure (P = 10–50 MPa) conditions. The chemical composition of the fluid and pore structure images were analyzed using ICP-OES and X-ray computed microtomography, respectively. Pore size distribution and evolution were assessed through digital cores based on Micro-CT analysis, while fractal and multifractal analyses were employed to quantify the evolution of pore structure heterogeneity. The findings highlight the importance of an effective combination of early material base and subsequent organic acid dissolution in the formation and maintenance of deep, high-quality dolomite reservoirs.

Effect of CO2 Concentration on the Performance of Polymer-Enhanced Foam at the Steam Front.

This study examines the impact of CO2 concentration on the stability and plugging performance of polymer-enhanced foam (PEF) under high-temperature and high-pressure conditions representative of the steam front in heavy oil reservoirs. Bulk foam experiments were conducted to analyze the foam performance, interfacial properties, and rheological behavior of CHSB surfactant and Z364 polymer in different CO2 and N2 gas environments. Additionally, core flooding experiments were performed to investigate the plugging performance of PEF in porous media and the factors influencing it. The results indicate that a reduction in CO2 concentration in the foam, due to the lower solubility of N2 in water and the reduced permeability of the liquid film, enhances foam stability and flow resistance in porous media. The addition of polymers was found to significantly improve the stability of the liquid film and the flow viscosity of the foam, particularly under high-temperature conditions, effectively mitigating the foam strength degradation caused by CO2 dissolution. However, at 200 °C, a notable decrease in foam stability and a sharp reduction in the resistance factor were observed. Overall, the study elucidates the effects of gas type, temperature, and polymer concentration on the flow and plugging performance of PEF in porous media, providing reference for fluid mobility control at the steam front in heavy oil recovery.

The role of physical exercise in modifying cardiovascular parameters in hypertensive patients

Hypertension is among the top risk factors for cardiovascular diseases. Diversified rehabilitation programs are needed to limit the progression of the high blood pressure condition. The welfare of aquatic therapy is acknowledged, but hydrotherapeutic procedures are rarely used in cardiovascular diseases. The study aims to assess the impact of an exhaustive hydro-kinetic thermo therapeutic program compared to other methods of treatment, i.e., cardiovascular rehabilitation program, recommendation for a healthy life, and antihypertensive medication. Four groups of patients (46 years ±0,32) diagnosed with hypertension participated in four different rehabilitation programs to analyze the impact on their effort capacity. Their ability to achieve average effort without the appearance of fatigue symptoms was studied for a period of eight weeks by monitoring six parameters: systolic blood pressure (SBP), diastolic blood pressure (DBP), Borg Scale, Medical Research Council Dyspnoea Scale (MRC-DS), pulse (P) and oxygen saturation (O2). Group A, which benefited only of recommendations for a healthy life, didn’t register any significant p values between the initial and final evaluation; group B, which had medications and recommendations for a healthy life, registered significant p values for 2 parameters (SBP and P have p<0.0001); group C, which took part in a cardiovascular rehabilitation program, obtained significant p values for 5 parameters (SBP, DBP, Borg, MRC-DS and O2 have p<0.0001); Group D, the recipient of hydrotherapeutic program, registered significant p values for all statistically 6 monitored parameters (SBP, DBP, Borg, MRC-DS, P and O2 have p<0.0001). Physical activity in water performed regularly within a controlled therapeutic program with the thermal and electrotherapy components, leading to improved capacity for the effort by decreasing blood pressure values and dyspnea parameters.

Analysis of Atomization Performance of Linear Laval Nozzle under Varied Water Pressures Based on VOF and DPM Models

Particulate matter from coal and stone operations is a primary air pollution source. The traditional nozzle requires high-pressure conditions, and the atomization droplets are large and uneven. This paper aims to study a linear Laval nozzle and investigate the impact of water pressure on atomization performance. The volume of fluid (VOF) model and discrete phase model (DPM) of Fluent are used to simulate the internal and external fields of the nozzle and analyze the velocity, droplet size, and atomization angle. The results show that the optimized water pressure parameters are 0.1 MPa with an air pressure of 0.5 MPa. Droplets in the middle are smaller, while those on the sides are larger. Compared to traditional nozzles, the water pressure is reduced by over 90%, and the Sauter mean diameter (SMD) decreases by over 50%. Moreover, the theoretical spray angle increases by approximately 150%.

Designing ternary Co-Ni-Fe layered double hydroxides within a novel 3D cross-flower framework for efficient catalytic performance in oxygen evolution reaction

In this study, we synthesized novel three-dimensional (3D) cross-flowered Co-Ni metal–organic framework (Co-Ni-MOF) precursors using the chemical precipitation method. Subsequently, we obtained Co-Ni-Fe layered double hydroxides (Co-Ni-Fe-LDHs) through an ion exchange strategy, which preserved their original morphology while consisting of ultrathin layered hydroxide nanosheets. The interlayer spacing of the LDH lamellar structure was finely tuned by varying the ratios of Co to Ni. The results demonstrated that Co-Ni-Fe LDHs, characterized by a unique three-dimensional cross-shaped structure and an optimal composition ratio of Co2+:Ni2+ = 2:1, exhibited increased interlayer spacing. This structural characteristic contributed to their excellent electrochemical performance, positioning them as optimal electrode materials for catalytic oxygen evolution reactions (OER). Our observations revealed that Co-Ni-Fe-LDHs exhibited remarkable OER activity, characterized by a low Tafel slope of 41.82 mV dec−1, a low overpotential of 322 mV at a current density of 10 mA cm−2, and outstanding stability over a 48-hour period. In-situ Raman spectroscopy results indicated that the active site of the composite was γ-CoOOH. Additionally, the room temperature stirring and standing strategy employed in this study is easier to scale up and yields a higher quantity of reaction products compared to traditional high-temperature and high-pressure conditions. This investigation provides novel insights into the design and fabrication of Co-Ni-Fe-LDHs catalyst with 3D cross-flower structures, demonstrating enhanced electrocatalytic activity and commendable stability. These findings suggest promising applications in the field of electrolyzed water.

Flow and heat transfer in multi-cavity pistons with oscillating cooling

Under high temperature and pressure conditions, pistons play a crucial role in managing thermal stress within combustion chambers. To analyze of the heat transfer characteristics of piston cooling systems in low-speed engines, this study developed and validated an oscillating cooling model featuring a composite piston with multiple cooling cavities. Using numerical simulation methods combined with dynamic mesh technology, the model replicates the long-stroke behavior of actual diesel engines and is validated against preliminary experimental data. The results demonstrates that during reciprocating motion, oil flowing through the telescopic sleeve interacts with gas from breather holes, forming a gas–liquid two-phase flow that significantly alters the liquid film coverage ratio (LFC) on wall surfaces, influencing heat transfer efficiency. As the filling rate increases from 28 % to 71 %, the average liquid film coverage (ALFC) rises by 0.27, and LFC fluctuation frequency decreases, with amplitude increasing by 0.08. Notably, the average Nusselt number (Nuavg) shows significant increases for top surface of inner cavity (TSIC) and side surface of inner cavity (SSIC) between filling rates of 52 % and 64 %, while the maximum increase for top surface of outer cavity (TSOC) and side surface of outer cavity (SSOC) occurs between 37 % and 52 %. Temperature drops at points A and B in the filling rate range of 28 % to 52 % were 1.37 K (4.09 K), which is notably higher than the 0.35 K (0.86 K) drop in the 52 % to 71 % range. Analyzing these changes indicates that the optimal filling rate for enhanced heat transfer performance is approximately 52 %. Furthermore, as engine speed increases from 135.2 to 202.8 rpm, the piston head filling rate decreases from 0.60 to 0.46, reducing both the contact area and the surface heat transfer coefficient. This study provides profound insights of the multiple cooling cavities under reciprocating motion and presents new strategies for optimizing piston cooling systems designed for low-speed engines.

Experimental study of hydrogen sulfide (H2S) behavior in brine/n-decane mixtures under HPHT conditions

This research investigates the dynamic behavior of hydrogen sulfide (H2S) under oil reservoir conditions, focusing on their interplay within both aqueous and organic phases. Surprising findings emerge, notably the heightened solubility of H2S at 250°C compared to 150°C, with values of 19.9 mg to 41.5 and 12.8 mg to 16.4 mg in 100ml of solution, respectively, diverging from conventional expectations, due to organosulfur compounds generated at the water/n-decane interface under high pressure and temperature conditions. Through an examination of Henry's Law and the calculation of Henry's constants across several temperatures, insights into these observations are gained. In the organic phase, temperature is observed to catalyze the formation of organosulfur compounds from n-decane and H2S. Notable compounds identified include aromatic hydrocarbons bearing sulfur substituents. highlighting the presence of 2-Propyldibenzothiophene (2 – 392 mg/mL), which represents between 57 and 95% of the total concentration of organosulfur compounds found in the organic fraction, being more abundant at 250°C. These findings underscore the intricate interplay between temperature, pressure, and phase composition, elucidating the nuanced solubility patterns and reaction dynamics of sulfur and organosulfur compounds.