Constant Pressure Research Articles

Study on reliability of control system in deepwater CBHP MPD system

Deepwater managed pressure drilling technology, with unique advantages in dealing with narrow density window, has been widely used in deepwater drilling operations. As the key equipment to realize managed pressure drilling, the control system in constant bottomhole pressure managed pressure drilling system plays an important role in drilling operations. In this study, a new reliability evaluation method based on fault tree analysis and dynamic Bayesian network model has been proposed to analyze the reliability of the control system. First, the structure of the control system in the deepwater managed pressure drilling system was analyzed to set up a fault tree model of the control system. Second, considering the influence of time on the reliability, a dynamic Bayesian network model of the control system was established. Third, the proposed model was partly verified using the verification method based on three axioms. Fourth, in consideration of the repair factor, the reliability and availability of the control system were calculated by using the exponential distribution model of failure time. Finally, the sensitivity of the control system was analyzed, and the mutual information, variance and entropy were calculated to find out weak links in key components of the control system.

Impulse generated from detonation waves in non-premixed and partially premixed reactants

Rotating detonation engines (RDEs) are the subject of research in the combustion community due to the prospects of enhanced thermal efficiency and power density when compared to current deflagrative-based aerospace combustors. Many current simulations presume premixed reactants and therefore miss the important characteristics of transient mixing, wave-induced mixing, and injector design/spacing that are known to play a pivotal role in the system performance. Very ambitious large eddy simulations are being conducted, but necessarily on a limited number of realistic and complex cases, thus limiting their utility in deriving fundamental understanding. For these reasons, a two dimensional parametric study was conducted to assess propagation of a detonation across an idealized array of mixing/injection sites, parametrically characterized by the width and axial mixing profile.Under such non-premixed conditions, discrete energy release and interdependence are observed. The discrete energy release sites frequently create pressures that exceed idealized Chapman-Jouguet (CJ) predictions based on perfect and uniform mixtures. The local higher pressure is shown to be caused by delayed heat release behind the shock, near constant pressure combustion, and additional compression due to the non-uniformities present. The resulting compression and the near constant pressure combustion are accompanied by time scale separation of exothermic and endothermic reactions due to the mixing efficiencies in the non/poorly-premixed cases. In contrast, the better mixed cases show that the detonation wave is sustained but unburnt fuel and oxidizer exist behind the main combustion wave and impulse performance suffers. Results show that for the conditions modeled there exists an optimal injector spacing to maximize the impulse produced and that discrete injection impulses can exceed that of the premixed systems. These somewhat counter-intuitive results imply that the detailed mixing evolution, provoked by the passage of the wave can lead to an extended heat release zone that elevates the pressure over a longer distance along the wavefront. These revelations provide potential for optimizing injector configurations for real non-premixed systems in order to exploit these physics.

A Method to Simulate an Outwardly Propagating Turbulent Premixed Flame at Constant Pressure

An outwardly propagating premixed flame in homogeneous isotropic turbulence at constant pressure is considered one of canonical configurations to study turbulent premixed flames. In this paper, a surface forcing method to prevent the undesirable influence of the boundary-condition-induced backflow on the flame evolution, while maintaining the constant pressure, in the simulation of the outwardly propagating flame is presented. The method is validated for laminar and turbulent flames. The results show that the present method well preserves the characteristics of turbulence and of an outwardly propagating flame, without the undesirable influence of the boundary condition, by feeding the homogeneous turbulence relative to the velocity field induced by the volume expansion due to heat release to the domain in which the flame develops.

Three-dimensional deformation measurement techniques in space multi-physical fields based on digital image correlation

Aiming at the three-dimensional deformation measurement requirement of the high-stability structure of spacecraft in space multi-physical fields, a comprehensive instrument protection device in a vacuum high-low temperature environment is developed using ultra-low temperature anti-condensation and vacuum heat insulation technology. This ensures that the digital image correlation (DIC) measurement camera always remains in a constant temperature and pressure environment and can stably exert its original efficiency in space multi-physical field environments. Subsequently, a path-dependent DIC method based on a graphics processing unit computing parallel acceleration is proposed by combining a pre-interpolation strategy and integrated image technology, which realizes high-precision matching of digital images before and after deformation in a spatial multi-physical field environment and improves the computing efficiency. To address the problem that a common reference point may deform significantly in a space environment with a large temperature change, which leads to inaccurate system accuracy, combined with a random sampling consistency algorithm and singular value decomposition method, the optimal registration of the coordinate system and the solution of deformation were realized by setting the threshold of the reference point margin screening. Finally, a three-dimensional deformation measurement system in high- and low-temperature vacuum environments was built, and the three-dimensional deformation measurement of the satellite antenna in high- and low-temperature vacuum environments was verified, which proves the effectiveness and accuracy of the above method.

Investigation of heat and mass transfer of oldroyd – 8 constant fluid in wire coating process employing response surface methodology

Wire coating is widely used for electrical insulation, shock protection, preventing leakage, and facilitating smooth current flow. This study aims to evaluate the applicability of Oldroyd-8 constant fluid for wire applications in a magnetic field using a pressure-type die. Based on the Buongiorno model with a constant pressure gradient and temperature-dependent thermophysical properties, governing equations are developed. These equations are transformed into dimensionless form and solved numerically. The study thoroughly investigates key features, including momentum, thermal distribution, nanoparticle volume fraction, and shear stress rate. Also, this study employs Response Surface Methodology to optimize heat transfer and shear stress rates in coated wire. Quadratic models, developed through a central-composite design, determine optimal levels for the Oldroyd-8 constant fluid parameter and nanofluid parameters, ensuring optimal heat transfer and shear stress rates for the melt. Nanofluid parameters contribute to an improvement in the thermal distribution profile. Optimal heat transfer and shear stress rate occur when the nanofluid parameters are minimized, and non – Newtonian fluid parameter is maximized.

Reservoir Characteristics and Formation Model of the Bauxite Gas Reservoir: The Benxi Formation in the LX Block, Northeast of Ordos Basin, China.

Recently, horizontal well L47-1CH in the Longdong area of the southwestern Ordos Basin made a significant breakthrough in bauxite natural gas exploration, changing the traditional geological understanding that bauxite could not form effective reservoirs. To further explore the exploration and development potential of bauxite natural gas reservoirs in the northeast of the Ordos Basin, it is urgent to carry out basic geological studies. This paper discusses the sedimentary environment, reservoir characteristics, and formation patterns of the bauxite gas reservoirs in the LX Block using trace elements, thin sections, X-ray diffraction, scanning electron microscopy, conventional physical properties, constant pressure mercury, etc. Then, the distribution pattern of bauxite was studied according to the restoration of the karst paleogeomorphology, and the formation model of bauxite was ultimately established. The results show that bauxite developed a clear triple-segment structure vertically, characterized by rich iron at the bottom, high aluminum at the middle, and low iron at the top. The mineral composition of the bauxite section mainly includes diaspore, iron minerals, titanium minerals, and birnessite. The types of pores mainly include intra- and intergranular dissolved pores, matrix-dissolved pores, intercrystalline pores, and microfractures. The porosity ranges from 1.51 to 9.90%, with a relatively good sorting and connectivity of the pore and throat. The bauxite was formed in a hot and humid climate, deposited in a shallow-water tidal flat and lagoon sedimentary environment with oxygen depleted, and experienced oscillatory regression during the deposition process. The thickness of bauxite is significantly controlled by karst paleogeomorphology, and it is mainly distributed at the negative terrain positions of karat pits and karst terraces. The above results can provide a geological basis for the exploration and development of bauxite in the Ordos Basin and similar basins worldwide.

UPPER WEATHERED ZONE TRANSMISSIVITY ESTIMATION OF HARD-ROCK HORIZONTALLY LAYERED MASSIF

The results of flowmeter tests of wells in the upper part of the layered rock massif indicate a model of the permeability medium in the form of separate horizontal thin fracture zones, separated by layers with a thickness of several meters. A study of pumping was done on a model in cylindrical coordinates for two thin aquifers. The upper one works with a constant pressure in pumping well, determined by the position of the zone, and a decreasing rate, and the lower — with an increasing rate, is additional to the pump rate. The filter intervals of the central and the only observation well are the same. The processing of pumping results using the commonly used Jacob method showed the main features — strong differences in transmissivity in different variants of well locations, unrealistically large values of the storage coefficient, ultra-small calculated radius of the pumping well.

Enhancing pressure control of low-friction pneumatic actuator with eddy current damper via valve dead-zone compensation

This article addresses the high-performance pressure control of a pneumatic actuator that incorporates an air-bearing piston and an eddy current damper (ECD). After optimizing the pneumatic actuator, achieving precise pressure control relies on maintaining an accurate and stable airflow through the control valve. A terminal sliding mode adaptive control method (TSMAC) is proposed, proficiently integrating considerations for dead zone nonlinearities in the proportional valve and the effects of unmodeled disturbances in the pneumatic actuator. Using the opening area of the proportional valve as the input to the pneumatic system greatly simplifies the control process and reduces the workload required for valve parameter calibration. The Lyapunov-based stability analysis demonstrates that excellent asymptotic output tracking can be achieved with low steady-state error simply by knowing the boundaries of the valve opening area. The control effect of the proposed control strategy is compared with an adaptive backstepping sliding mode control method based on a linearly fitted proportional valve model on an established constant pressure control test bench. Experimental results under various loads and operating conditions illustrate the effectiveness of the proposed approach.

Sea and brackish water desalination through a novel PVDF-PTFE composite hydrophobic membrane by vacuum membrane distillation

The present study aims to evaluate the performance of porous hydrophobic Polyvinylidene fluoride − Polytetrafluoroethylene (PVDF-PTFE) composite membranes for desalination by vacuum membrane distillation (VMD) technique. The effect of operating parameters such as feed NaCl concentration (10,000 to 40,000 mg/L), feed temperature (50 °C to 80 °C), and downstream pressure (80 to 120 mmHg) on water permeation rate was studied. The increase in feed temperature enhanced the water permeation rate due to a rise in driving force across the membrane. For a constant downstream pressure of 80 mmHg, feed temperature of 80 °C and feed flow rate of 80 L/h, the membrane exhibited a maximum water flux of 3 kg/m2h with 99.86% salt rejection when aqueous NaCl concentration of 10,000 mg/L was charged as feed. Membrane characterization was performed using various analytical tools to determine physico-chemical properties such as pore size, structural elucidation, thermal stability, crystallinity, and hydrophobicity of the membrane material. Further, a temperature and concentration polarization coefficient-based analysis was performed by solving the mass and heat transport model equations using MATLAB software. The proposed research study promotes the application of VMD for recovering potable water from highly saline sea/brackish water and alleviates brine disposal issues.

Study on the evolution of permeability properties of limestone under different stress paths

Abstract Stress path change has a great relationship with the effect of deformation and strength of rock. However, the underground rock body is in the engineering environment where the stress field, seepage field, and other fields are coupled to change, the law of fluid flow in the rock body is complex and variable. The change in the stress field has an important effect on the seepage characteristics of rock body; therefore, it is necessary to study the pattern of rock permeability evolution pattern by different stress paths. This study is based on the study of limestone, conducting triaxial unloading seepage mechanics experiments, the evolution of permeability properties of limestone specimens was analyzed based on the test results. The results show that in the conventional triaxial loading seepage test, the permeability of the limestone decreases before the rock stress reaches the peak intensity and increases after that. Increasing axial pressure unloading surrounding pressure compression section, permeability loss rate and effective stress are in line with the changing law of Gaussian distribution function. Under the action of constant axial pressure unloading surrounding pressure, with the increase in unloading amount, the permeability rate of change appears to increase slowly, and in the late stage of unloading section, the permeability rate of change appears to surge. Unloading section permeability change rate and cumulative unloading amount are in line with the law of change of the exponential function. Creep unloading pressure seepage test found that unloading pressure stage strain-time and permeability-time evolution characteristics are in line with the exponential rule of change. The experimental results of this study can provide an important experimental and theoretical basis for the permeability analysis of low-permeability rock body under complex stress conditions in underground engineering.

Fabrication and simulation of a microvalve for molecular communication control on a chip

In recent years, microvalves have become increasingly significant in microfluidic structures. In microfluidic devices, these microvalves are crucial to controlling fluid flow. Due to their ability to precisely manipulate and adjust the fluid, these structures are more efficient in applications, particularly in medicine, drug delivery, protein analysis, microscale communication, and chemical processes. Utilizing a numerical model for the design and fabrication of a microvalve results in the development of a more optimized and efficient structure. Microvalves can be generally divided into active and passive categories. This research focuses on the design and fabrication of a pneumatic microvalve, which falls under the category of active microvalves. This structure has two distinct chambers that allow for microscale communication. The microvalve is constructed using two layers, where the upper layer controls the lower layer, which contains fluid flow through pneumatic pressure. The performance of the system was evaluated through experimental analysis. The microchannel passage remained obstructed when the flow rates were set to 0.2 ml/h and when maintaining a constant pump pressure of 15 psi. However, the fluid flow is connected even when the pressure is cut off. We believe this structure will impact diverse applications, including molecular communication.

A Constant Pressure Cylinder Coupled With a “Zero-Stiffness” Eddy Current Damper

A Constant Pressure Cylinder Coupled With a “Zero-Stiffness” Eddy Current Damper

Increase of the Efficiency of Heat Supply Units of the CHP Plants Due to the Choice of Rational Heat Release Modes

The possibilities of increasing the efficiency of heat supply turbines of CHPPs due to the choice of rational modes of operation of network water heaters are analyzed. With the help of a software and computing complex developed at the Institute of Mechanical Engineering Problems of the National Academy of Sciences of Ukraine and adapted by the authors to the operating conditions of CHPP generating equipment with one or two network heaters, a set of calculation studies of various ways of connecting them depending on the outdoor air temperature is conducted in the paper. Areas of positive effect associated with increase in the electric power of the power plant have been established. The calculation study was carried out at typical power plant water consumption from 1000 t/h to 4500 t/h, in the range of changes in the outdoor air temperature from -11 ºС to 10 ºС (heating season) and more than 10 ºС (hot water supply). The load change of the power unit was carried out due to the consumption of fresh steam at a constant pressure and temperature at the turbine inlet. As shown by the results of the operation of the T-100/120-130 heat supply turbine in operating conditions with one or two heat supply steam selections, in the area of positive outdoor air temperatures above 2 ºС, it is advisable to use one lower selection (with the upper one turned off) for all network water consumption. At the same time, additional electric power in the area of outdoor air temperatures above 6ºС can be from 0.25 MW to 2.15 MW. However, when the outdoor air temperature is less than 2 ºС, work with one lower heating selection becomes irrational. From the point of view of choosing rational modes of operation of turbine plants, the most important are the results of determining the optimal distribution of heat load between network heaters. The gain in electrical power of the turbine can be up to 2.46 MW in the nominal mode of operation with two heaters, and up to 7.84 MW in comparison with the use of single-stage heating. The nature of the influence of the distribution of the heat load indicates that during deprivation from the instructional uniform distribution of the heat load between network heaters, it is possible to obtain additional electricity.

Effects of obstructive sleep apnea syndrome on clinical and instrumental indicators in obese patients

Due to the high prevalence of obstructive sleep apnea syndrome (OSAS), its diagnosis and treatment remains one of the urgent problems of medicine. Hypodiagnosis of OSAS is observed in everyday clinical practice. The early OSAS diagnosis and treatment, including the use of non‑invasive assisted ventilation of the lungs with constant positive pressure during sleep, could prevent the development and progression of cardiovascular diseases, and significantly improve the quality of life of a person.
 Objective — to assess OSAS impact on the clinical and instrumental indicators in obese patients, to establish correlation between the characteristics of cardiorespiratory sleep monitoring and indicators of carbohydrate and lipid metabolism in obese patients.
 Materials and methods. Observations involved 78 patients with I ‑ II degree obesity. According to the results of cardiorespiratory monitoring (CRM) of sleep, three groups of obese patients were formed. The first group included 26 patients with an apnea‑hypopnea index <30 episodes per hour (mild OSAS degree). The second group was consisted of 26 patients with apnea/hypopnea index (AHI) over 30 episodes per hour (severe OSAS degree). The groups matched by percentage of men and women, the mean age and body mass index.
 Results. An increase in body weight and body mass index (BMI) in obese patients was associated with an increase in the number and total duration of episodes of apnea/hypopnea, AHI, as well as a decrease in blood oxygen saturation (SpO2). Parameters of waist circumference (WC), hip circumference (HC), WC/HC positively correlated with the number and duration of episodes of apnea/hypopnea, AHI, and negatively correlated with SpO2. Positive values of the Spearman r coefficient ranged from 0.23 to 0.57, negative values — from –0.26 to –0.48 (р <0.05).
 Conclusions. In obese patients with OSAS, the parameters of cardiorespiratory sleep monitoring — apnea‑hypopnea index, total duration of apnea episodes, directly correlated with body mass index, waist circumference, blood pressure level, total cholesterol, blood triglycerides. An inverse correlation was found between oxygen saturation and fasting glycemia and the level of glycated hemoglobin.

B4C ceramics with increased dislocation density fabricated by reactive spark plasma sintering via carbon nanotubes–boron mixture

Boron carbide with high relative density was prepared in situ using spark plasma sintering. Research on the in-situ reaction of boron and carbon nanotubes reveals that the reaction exhibits high reactivity at 1200 °C. Beyond this temperature, increasing the external pressure was beneficial for particle rearrangement, gas release, and dislocation formation. The result of mechanical properties shows that, the flexural strength and fracture toughness of the boron carbides are 656 ± 9 MPa and 5.0 ± 0.3 MPa m1/2, respectively, when sintered at 1750 °C under continuous pressure ramping conditions–an increase of 64.1% and 46.6% compared to that prepared under constant pressure conditions. Increasing the magnitude of the external stress during the in-situ reaction process can also enhance the particle rearrangement efficiency, inducing the formation of twinning and stacking faults in boron carbide ceramics. High–density twinning and stacking faults dominated the toughening mechanisms of ceramic materials.

Creative principles for managing innovation projects in BANI environment

In the dynamic landscape of innovation, where environments are increasingly characterized as Brittle, Accelerating, Nonlinear, and Incomprehensible (BANI), traditional project management approaches fall short of addressing the complexities and uncertainties that arise. This abstract explores a set of creative principles tailored for the effective management of innovation projects within BANI environments. Drawing inspiration from agile frameworks, design thinking, and open innovation, these principles aim to navigate the brittleness, acceleration, nonlinearity, and incomprehensibility inherent in such contexts. Adaptive leadership, rapid prototyping, and scenario planning emerge as key components, fostering a culture of continuous learning and cross-functional collaboration. Emphasizing innovation metrics beyond traditional KPIs, the abstract advocates for an ecosystem thinking approach to holistically comprehend the intricate interplay of factors within BANI environments. By integrating these creative principles, organizations can position themselves to not only adapt to the challenges presented by BANI but to thrive amid uncertainty, turning it into a catalyst for innovative growth. The world of innovation is facing unprecedented challenges. The acronym BANI – Brittle, Anxious, Nonlinear, and Incomprehensible – aptly captures the current environment characterized by fragile systems and interconnectedness. A single event can trigger cascading disruptions across industries and continents. Heightened uncertainty and anxiety. Rapid change and unforeseen events create constant pressure and require agility in decisionmaking. Non-linear trajectories and emergent phenomena. Traditional planning becomes obsolete in a world where cause and effect are blurry and unexpected outcomes arise. An incomprehensible information landscape. The sheer volume and complexity of data make it difficult to discern truth and make informed decisions. By embracing these creative principles, we can transform innovation projects from rigid endeavours into dynamic journeys of exploration and discovery. In the face of the BANI environment, embracing creativity, learning from failures, and pivoting quickly are the keys to unlocking ground breaking ideas and shaping a better future.

Scale up validation tests for Buckingham Pi theorem applied to leaf test experiments for iron ore slurry

Bench tests were conducted on ore slurry filtration using the leaf test method, varying scales, pressures, and water/solids ratios. These results were compared with analytical outcomes derived from applying the dimensionless Buckingham pi method to the general equation of slurry filtration with incompressible cakes under constant pressure. The aim was to validate the tests by corroborating experimental findings with calculated parameters for scale-up purposes. Vacuum pressure was employed to facilitate slurry dewatering, forming a cake comprising solids from the slurry. This cake’s thickness evolved over time, introducing specific resistivity that impeded filtering efficiency. Parameters such as cake resistance and filter media resistance were computed. Filtrate volume was measured over time to determine the filtration rate. These values were then adjusted using factors obtained through dimensional analysis. These factors facilitated comparisons to validate the feasibility of employing the Buckingham pi method for predicting slurry filtration results at larger scales. The results indicated lower errors when analyzing the filtrate rate over time with a solids/water ratio of 20/80%. When evaluating cake resistance, the method yielded lower errors at a ratio of 70/30%, while results for medium resistance were inconclusive. It’s important to consider the ratio and associated errors when predicting the behavior of an industrial filter based on bench test results, aiming to achieve theoretical scaled filtration rates and cake resistances. However, it’s not advisable to rely on the Buckingham pi method for scale-up purposes when evaluating medium resistance.

Towards the Industrial Implementation of Mn-based Catalyst for the Hydrogenation of Ketones and Carboxylic Esters.

There is a constant pressure in industry to move away from platinum group metals (PGM) and achieve more environmentally friendly and sustainable production processes in the future. Recently developed Mn-based catalysts offer an interesting opportunity to complement established catalysts based on Ru. In this article, recent achievements in the field are highlighted and recent achievements in the collaboration of Solvias AG with the group of Prof. M. Clarke towards the implementation of these catalysts on industrial scale are outlined.

Modeling of the motorized spindle temperature field considering the thermos-mechanical coupling on constant pressure preloaded bearings

Modeling of the motorized spindle temperature field considering the thermos-mechanical coupling on constant pressure preloaded bearings

Improved saturation-pressure relationship and multiphase pseudo-pressure calculations for retrograde gas reservoir production under boundary-dominated flow

For reservoirs containing fluids with complex flow characteristics, the calculation of multiphase pseudo-pressure plays a significant role in production data analysis (PDA) practices. In the case of retrograde gas reservoirs/gas condensate reservoirs under multiphase flow conditions, the lack of a reliable and complete saturation-pressure (So-p) relationship presents a significant challenge in obtaining the appropriate value of multiphase pseudo-pressure. Gas condensate reservoirs are one of the viable and lower-emission hydrocarbon sources for meeting the ever-increasing global energy demand. The economic value of producing gas condensates has inspired numerous research into employing innovative production techniques in developing gas condensate fields. Hence, this study proposes an improved saturation-pressure relationship alongside a Fractional Phase Mobility (FPM) criterion to mitigate potential errors in the multiphase pseudo-pressure calculation for gas condensate reservoirs under boundary-dominated flow. This work introduces an improved So-p relationship derived using a Rescaled Constant Volume Depletion (CVD) method for estimating multiphase pseudo-pressures. To demonstrate the effectiveness of the proposed approach, we provide direct comparisons with the Classical CVD method and numerical simulation results for multiple gas condensate cases subjected to constant and variable bottomhole pressure (BHP) schedules. In contrast to the classical approach, the Rescaled CVD method consistently delivers superior performance for multiphase pseudo-pressure estimations across all cases, thus supporting its potential as a robust and accurate approach for gas condensate reservoir modeling.