Inlet End Research Articles

Microscale heat and mass transfer characteristics of CO2 flooding in nanotubes of tight oil reservoirs

AbstractThe mechanism of heat and mass transfer in tight oil reservoirs after CO2 injection is complex. In this paper, first, a CO2 transfer model within microscale adjacent nanotubes in tight oil reservoirs is established. Then, the typical heat and mass transfer characteristics of microscale CO2 in tight oil reservoirs is analyzed, and the influence of grid density on the calculation results is discussed. Finally, the influence of thermal conductivity of tight oil reservoirs on CO2 physical properties parameters is revealed. Results show that: (a) From the inlet end of the thick nanotube to the outlet of the nanotube, the pressure of CO2 drops from 3.5 to 3.3697 MPa. (b) When the mesh length is equal to 5 nm, the CO2 pressure in the thin nanotube drops from 3.5 to 3.3329 MPa, and the CO2 pressure in the thick nanotube drops from 3.5 to 3.2018 MPa. (c) Organic amines react with CO2 to form salts, which can seal high permeability layers and cracks, but there is a risk of environmental pollution.

EFFECT OF BUILD POSITION ON SURFACE ROUGHNESS OF SLM PRINTED INCONEL 718

The present work investigates the variation of the surface roughness due to the build position of specimens with respect to the inert gas flow direction and re-coater movement direction. Selective laser melting (SLM) method was used to study this effect using Inconel 718 as workpiece material. A total of 21 samples were placed equidistant from each other on the built plate to observe the effect of gas flow and re-coater movement. The effect of these parameters on the printed samples was analyzed in terms of the profile surface roughness parameter such as Ra and Rz in the build direction. The result showed that samples placed near the gas inlet and the re-coater starting position had larger roughness as compared to the samples placed further from the gas inlet and re-coater end position. The result showed that the profile average roughness parameter values varied from Ra = 5.02 µm to 14.7 µm and profile maximum height surface parameter varied from Rz = 47.61 µm to 118.3 µm for all the printed samples. Surface topography of the samples was also studied which showed common printing defects such as cracks, micropores, local solidified melt pools, and dimples. The study opens an avenue to explore and optimize the placement of the printing sample on the build plate with respect to the inlet gas flow and re-coater movement directions for better surface roughness.

Experimental investigation for the influence mechanism of air intake method and humidity level on performance of proton exchange membrane fuel cells

As pivotal component of hydrogen fuel cell vehicles (HFCVs), proton exchange membrane fuel cells (PEMFCs) play a crucial role in determining performance and energy efficiency of HFCVs. In this study, comprehensive bench tests of fuel cell stack and electrochemical impedance spectroscopy (EIS) tests of single cells were conducted, and influence mechanisms of air intake methods and humidity levels on performance of stack and single cells at different locations were analyzed in depth. The results indicate that counter-flow inlet method exhibits superior voltage output performance and stability across various relative humidity (RH) and current densities (CDs). A moderate increase in RH can mitigate performance degradation, but excessive humidity can lead to flooding. When RH is increased to 60%, the voltage difference between co-flow and counter-flow of fuel cell stack does not exceed 0.05 V at 1.6 A/cm2. Meanwhile, the performance of cells near inlet end plate is consistently worse than those farther away under different inlet conditions. In addition, the performance trend of single cells in serpentine channels aligns with that of fuel cell stack, underscoring strong adaptability of mechanisms influencing performance under different conditions. These findings provide theoretical guidance and data support for optimizing performance and preventing failures in PEMFCs.

Experimental and simulation study of flow field characteristics of a disturbing rotary centrifugal air classifier

In the present study, a new disturbing rotary centrifugal classifier was designed and a method was proposed to characterize its pressure signals. The models for evaluating the classification effects were established based on multi-zones. It was found that the flow field, processing parameters, and material properties significantly affected on the particle force and classification performance. The pressure with high amplitude and energy analyzed using Hilbert-Huang Transform (HHT) concentrated within 200–400 Hz, and the screening cage facilitated energy transfer to lower frequency bands. Correlation analysis demonstrated the correlation coefficients (A5 and A6) between adjacent measurement points increased with frequency, further enhanced by the screening cage. The flow field of simulation was characterized by a low-pressure, high-velocity gradient at the center and a high-pressure, low-velocity gradient at the sidewalls and the gas velocity and flow for experiment achieved the maximum at z = 0.50 m, while the magnitude of pressure change was significant at the inlet end and discharge end, where the velocity gradient and pressure drop had the same trend and small errors for experiments and simulation. The flow field affected the competing relationship between centrifugal and drag forces on the particles with different kinematic behavior during the classification process. The errors between the predicted values of the theoretical, simulated, and experimental cut particle size models and the true values were all within 10 %, based on which the multi-zone classification efficiency model applicable to the disturbing centrifugal classifier was established, and it was found that the models all had high prediction accuracy and suitability. The article delves into the correlation between pressure signals, flow field characteristics and particle behavior, aiming to provide an important reference for the internal flow field and classification performance of air classifiers.

Experimental study on acid etching mechanism of acid fracturing in carbonate reservoirs

Acid fracturing is one of the most effective methods to enhance oil and gas production in carbonate reservoirs. The effect of acid fracturing is mainly affected by the conductivity, which is controlled by the acid-etched morphology of the fracture face and near-wellbore zone. Currently, the acid etching mechanism of the fracture face and near-wellbore zone is not considered in traditional experiments. The flow and reaction of acid in the fracture are simulated by using the cores with processed artificial fracture and the high-temperature acid-resistant experimental setup based on traditional experiments. The results under different conditions are obtained. The fracture face and inlet end face of cores are analyzed by combining the dissolution rate, reaction rate, average etching depth, and standard deviation. The effects of the lithology, pump rate, thickening agent concentration, and acid concentration on the acid etching mechanism of acid fracturing in carbonate reservoirs are investigated.

Performance Evaluation of Micro-Irrigation Systems in Coconut Plantations

Most of the coconut farmers in Sri Lanka are reluctant to adopt micro-irrigation systems, complaining about low performance. A field study was conducted to verify the claim. The performance was evaluated in two subunits at the inlet and distal end of two micro-irrigation systems with drippers and mini sprayers. The subunit at the inlet of the system with drippers showed a fair Emission Uniformity (78%) and all other tested subunits in both systems showed poor Emission Uniformity, falling below the 70% threshold set by the American Society of Agricultural Engineers. In the drip irrigation system, the increase of Emission Uniformity in the subunit at the distal end was approximately 33%. The increase of Emission Uniformity in all subunits of both systems was 4-6% after replacing the emitters with new emitters. The system with drippers showed severe clogging risk and the system with mini sprayers showed minor clogging risk. Despite the water being in the low clogging risk category, the mini sprayer exhibited the highest percent weight reduction (2%) after washing to remove clogging substances. The coefficient of manufacturer’s variation of the new drippers was in the marginal category of the classification. The Emitter Flow Variation of all the subunits were unacceptable level (>25%) with the existing drippers and mini sprayers. Only the subunit at the inlet of the drip irrigation system showed acceptable Emitter Flow Variation with new emitters. This study revealed that the low performance in both systems was due to emitter clogging and poor hydraulic design.

Flow rate measurement in gravity irrigation systems using sluice gates

Gates are used to divert water to rice production plots in eastern Uruguay. In this study, the operating curves of rectangular gates installed at the entrance of circular section pipes are determined for submerged discharge conditions, which can be also used as gauging structures. For the tests, the gates were mounted at the inlet end of 6-m-long,sanitary-type PVC pipes, and with a nominal diameter of 250 and 315 mm. This configuration is analogous to that used in gravity irrigation systems. The derivation of the operating equations of the gates in this configuration is presented. The discharge coefficients (Cd) experimentally obtained show that discharge under the gate is dependent on the opening and on the upstream and downstreamdifference in depth, in addition to the Reynolds number under the gate. The dependence on the Reynolds number, which is usually omitted in other applications, is relevant in the case of rice irrigation, given the low velocities, and allows its use as a regulation structure and water gauging in these systems.

Research on Air Filter Monitoring System of Oxygen Generator

Zeolite is an expensive consumable material in oxygen generator which needs to be replaced regularly. The life of zeolite is mainly determined by dust, humidity and temperature. Among which, dust has a great influence on the life span of zeolite. In the process of oxygen production, the dust in the air will be adhered to the molecular sieve, and shorten the life of zeolite. PSA (Pressure Swing Adsorption) oxygen generator has a filter at the air inlet end, which is used to filter out the dust particles in the air. The filters of PSA oxygen generator are disposable regularly. The replacement cycle depends on the air environment, and the cycle is short if under much dust particles.This thesis investigates the architecture of the filter failure detection. The architecture can detect the air environment dust condition, detect the filter failure, prolong the life of the filter.

Numerical Simulation and Temperature Modeling of Magnesium Alloy Strip Rolled by Heated Roll

A prediction model for the outlet temperature of magnesium alloy strips in the process of heated-roll rolling was established by using linear fitting and nonlinear regression methods. By inputting the rolling parameters into the model, the outlet temperature of the strip can be accurately predicted, which will then optimize and regulate the properties and microstructures of the magnesium alloys in the rolled form. To verify the reliability of the model, heat transfer experiments of the magnesium alloy rolled by heated rolls were carried out. The results show that under the same conditions, the actual outlet temperature measured experimentally matches well with the outlet temperature predicted by the model, and the relative error is kept within 10%. In the modeling process, Deform V11.0 software was used to simulate the thermal–mechanical behavior of the magnesium alloy rolled by the heated roll. In the process of analyzing the simulated heat transfer, it was found that the temperature rise of the surface and the core is divided into three identical stages: the slow rise, the fast rise, and the thermal equilibrium stages. In addition, the mechanical behavior of the rolling deformation zone was also analyzed, and the strip was subjected to direct heat transfer from the heated rolls during the hot rolling process so that the softening played a major role and the stress value gradually decreased from the middle of the deformation zone to the inlet end and the outlet end. This is so that it can be known that the process of being rolled by the heated rolls not only improves the rolling efficiency, but also ensures the deformation temperature and obtains fine grains.

Analysis of flow diffusion of secondary lubricant in water-lubricated bearings

To reduce the lubrication failure of water-lubricated bearings under short-term harsh conditions, preliminary experiments have shown that temporarily supplying a small amount of lubricating oil into a bearing as a secondary lubricant can improve the load capacity of the water film therein. However, the physical flow and diffusion state of this secondary lubricant (oil) in water are unclear. Therefore, a mixed lubrication model and a volume-of-fluid model are incorporated to study the diffusion behavior of a small amount of lubricating oil in a water-lubricated bearing. The results show that there is a backflow effect in the local area inside the bearing, where the fluid velocity is in the opposite direction to the linear velocity of the shaft. This backflow effect intensifies with increasing eccentricity ratio, which enlarges the oil-free zone in the middle part of the bearing. In the convergence area at the water inlet end of the bearing, the water supply pressure and backflow effect prevent the lubricating oil from escaping. Increasing the shaft speed has a positive effect on the diffusion of the oil and the load capacity of the fluid. To enhance the assisted lubrication effect of the oil, the oil injection port should be set in the loading zone to avoid the backflow zone. This research provides some fundamental data for reducing the friction and wear of water-lubricated bearings under harsh conditions.

CANDU6 single channel CCP analysis on pressure tube deformation effects with multi-physics coupled calculation

Though pressure tube deformation rigorously and simultaneously affects channel coolability and neutronics behavior, the two effects have never been coupled with each other. In this study, the CUPID code is coupled with the SHAFE code to obtain the Critical Channel Power (CCP) of a designated channel which has high nominal power, a high void fraction, a high flow rate, and high pressure deformation. Even though appendage modeling is not included in this study, adequate cell-wise uniform artificial form loss was sought through iteration and imposed to conserve the header to header pressure drop by considering the inlet & outlet feeder and end fitting pressure drop. Nested loops are included in CCP calculation logic; they are the channel power loop, pin power distribution update loop and flow rate optimization loop from outer loop to inner loop, in sequence. Both CUPID and SHAFE are based on the Fortran computer language; the CUPID code is converted to the Dynamic Link Library (DLL) and the SHAFE code can load the CUPID library whenever it is required. Finally, we found that a CCP decrement for a channel with large pressure tube deformation is not that much, even for a complex deformation case. In addition, the sagging effect for a CCP decrement is significantly different from the expectation before an analysis is completed.

Vibration Reduction and Explosion Control Investigation for an Ultra-Shallow Buried Tunnel under Crossing Buildings Based on HHT Analysis.

With the rapid development of underground space utilization, the excavation of new tunnels with ultra-shallow under crossing buildings using the drilling and blasting method is gradually increasing. The blasting vibration will undoubtedly affect the surrounding buildings. Reducing the impact of blasting vibration on ground buildings has become an important technical challenge faced by tunnel blasting technicians. The inlet end of the Xi'an-Chengdu High-Speed Railway Xiannvyan Tunnel passes below a village through an ultra-shallow buried section; as a result, blasting vibration control is a major concern. A design scheme for a 0.6 m footage in tunnel was proposed and verified through field tests. A 0.8 m footage scheme and 1.8 m footage millisecond interference vibration reduction scheme were proposed, respectively. Based on the HHT analysis, by comparing the surface vibration velocities and instantaneous energy obtained from the millisecond delay detonation of cutting holes and the detonation of different charging schemes, we found that the free surface, mass of single dynamite charges, and tunnel burial depth had significant influences on the surface vibration.

Preparation of thermo-responsive polymer and its application for plugging in hydrate-bearing sediments

Hydrate phase equilibrium can be disrupted by the drop in pressure and increase in temperature due to the drilling fluid invasion into hydrate-bearing sediments (HBS) during drilling operations. In this study, in order to alleviate hydrate dissociation in the drilling process, thermo-responsive polymers as reversible plugging nanoparticles were employed in drilling fluids. First, by introduction of butyl acrylate monomers into N-isopropylacrylamide with different molar ratios, a series of thermo-responsive polymers with different lower critical solution temperatures (LCSTs) were prepared to adapt the formation temperature conditions, and then their plugging performance and the reversibility in hydrate-bearing sediments were studied. Results showed that the hydrate decomposition only occurred in a limited zone within 2 cm during the injection of polymer solution, and the hydrate saturation decreases only by 4.4% at 10 min at a position 2 cm from the inlet end. A dense filter cake formed by the polymers can effectively prevent external fluid from entering hydrate sediments for a long time under the condition of 3 MPa differential pressure, and thus reduce the decomposition of hydrates in porous media. Moreover, the differential pressure dramatically decreased from 3.2 MPa to 0.8 MPa when the temperature declined to below the LCST, indicating that the particles blocking the pore throat can be gradually re-dissolved and expelled from the pores. Consequently, the reservoir permeability can be recovered due to the reversibility of thermo-responsive polymer, allowing fluid flows in the exploitation process. Thermos-responsive polymers can be smart plugging agents to block and unblock the well walls in the whole drilling and production stages in hydrate-bearing sediments with intelligence.

Study on the Selection of Single-Screw Steam Compressors in Industrial Steam Supply

Both direct and indirect heating compression methods were proposed to satisfy the requirement of industrial steam compression and supply. The compression process in a single-screw compressor was analyzed with the determination of different inlet and outlet boundary conditions. Considering the misalignment of meshing pairs caused by the offset of the star wheel axis and screw origin, the differential expansion of the vertical meshing pair was further analyzed. The inner ring of the sealing end face, the wall of the inner ring of the bearing at the inlet and outlet ends, and the bottom surface of the bracket were analyzed by different coordinate systems and different constraints, thus facilitating the design and selection of the single screw. The critical point for the design of a steam-type single-screw compressor is an outlet temperature of 350 °C and an outlet volume flow rate of 130 m3/min. At a flow rate of 130 m3/min, when the temperature exceeds 350 °C, the reliability of the compressor is still limited, and the differential expansion of the meshing pair exceeds 0.3 mm. In addition, superheating of steam can be improved by applying a centrifugal compressor with cascade compression and centrifugal compression in conjunction with reflux adjustment at the compression outlet.

Spatially permeable screening distribution characteristics of banana-type vibrating screen material groups and industrial application

ABSTRACT Screening is a critical technology to achieve clean and effective use of coal. Due to their ability to achieve equal-thickness screening and excellent working efficiency characteristics, banana screens are widely utilized for material classification. The current work employs a vibration test and analysis system to investigate the laboratory-scale and industrial banana screens’ kinematic features. The screen surface’s amplitude gradients at the inlet and outlet ends of the laboratory and industrial scale banana screens were 0.5 mm and 7.5 mm, respectively, verifying the “strong-in, weak-out” transfer law of the vibration energy. The results of the 6 mm screening experiment in the laboratory indicated that the coal samples were concentrated in the middle of the screen surface with the highest screening efficiency of 95.05% and the lowest total mismatch content of 2.68%. A Birtley’s four-stage banana screen was utilized to classify the 6 mm raw coal during the on-site heavy media separation at the Tunbao coal processing plant. Besides, a better screening performance was obtained with an efficiency of 89.92% and total mismatch content of 5.31%. The differences in accuracy of the distribution rate curves were all less than 5%, indicating that the laboratory banana screen is a prominent guide for industrial applications.

ATHEROMA PROGRESSION: PHYSICAL MODELING IN EXPERIMENTAL CARDIOLOGY

Prototype models of intra-arterial circulation is one of the priority aims of experimental cardiology, as well as for the study of atherosclerosis. Purpose: To study the features of intra-arterial hemodynamics in the area of​​atheroma of the artery in physical modeling. Materials and methods: We used an original "Device for modeling intra-arterial circulation". The main parts of the model: glass rotameter tube in the form of a truncated cylinder, inlet and outlet ends of which are fixed with elastic plastic tubes connected to an electric water pump immersed in a container with glycerol solution. Inside the rotameter, using a fitting from the inlet, it is possible to install a pressure sensor that transfers data to the oscilloscope; indicators - a silk thread or dye - ink. The variable pump mode allowed us to simulate a regular heart rhythm, extrasystole (ES) and atrial fibrillation (AF). Results: In the first post-extrasystolic wave, a turbulent fluid flow formed after the plaque, standing waves and waves reflected from the walls of the rotameter were observed; the sensor registered an increase in pressure 1,6 times more compared with a regular heart rate wave. The marginal plaque zones along and against the fluid flow, especially the areas bordering the intact part of the arterial vessel, underwent the main mechanical impact. The same patterns were observed in AF with a maximum duration of a pause between pulse waves of ≥1,5 s. Conclusions: Heart arrhythmias play an important role in the intra-arterial hemodynamics changes and are the part of the pathophysiological changes in the arteries in atherosclerosis. The main danger is not the ES itself, but by the first post-extrasystolic contraction or the first pulse wave after a long pause between ventricular contractions in AF.

CFD Simulation and Optimization of the Leaf Collecting Mechanism for the Riding-Type Tea Plucking Machine

In the process of tea plucking and leaf gathering, the structure optimization design of the leaf collecting mechanism is the key element responsible for collecting fresh leaves. The unreasonable design and manufacture of leaf collecting mechanisms will cause the smooth collection of fresh leaves, the quality of the collected fresh leaves will be damaged, and the commodity value will be reduced. In order to further study the structural characteristics of the leaf collecting mechanism, an air outlet model of the leaf collecting mechanism was established for the phenomena of internal vortex rotation and impact in the leaf collecting mechanism process. The internal flow field of the leaf collecting mechanism, the movement trajectory of fresh leaves, and the non-homogeneous flow are calculated using computational fluid dynamics (CFD). Based on Box-Behnken’s central combinatorial design theory, the velocity inlet and outlet air structure factors are taken as the influencing factors to carry out response surface test research. The effect of different parameters such as engine rotation, shape of the blowing cavity and air outlet parts, and velocity on the flow is determined. The optimal parameter combination is as follows: the height of the outlet end, the length of the inlet end, and the velocity inlet are 0.01 m, 0.03 m, and 25 m/s, respectively. Furthermore, it was found that when the number of plates increases from 1 to 4, the non-homogeneity decreases all the time, and the distribution of blowing air is improved without a sharp decrease in velocity. The average velocity outlet was larger than the velocity inlet, which meets the requirements of blade gathering. Considering comprehensively, the flow field simulation of the blade collecting mechanism with four baffles was consistent with the test results of the velocity outlet. The validation results showed that the model can successfully simulate the air flow inside the leaf-collecting mechanism, and the reasonable structure design was conducive to reducing the number of collisions between tea buds and improving the quality of tea buds. This research has certain theoretical and practical implications for the accurate plucking of high-quality tea.

Flow Analysis of Intake Manifold Using Computational Fluid Dynamics

The main element of the air intake system is an intake manifold. These are the main components which control the flow value that will be used in the combustion chamber. Thisstudyaimsto analyse the velocity of flow distribution in all runners and to compare the design of intake manifold in previous study. Simulations are performed on two types of intake manifold design which are Design 1, the inlet end is located next to the regulator chamber whilst for Design 2, the inlet end is inthe middle of regulator chamber. Intake manifold parameters such as velocity distribution, unevenness and pressure losses along the runner are used to determine the better design for better performance. From the results, the velocity,and the pressure of intake manifold of these twotypes of design are determined. Compared with previous study, the velocity difference is 0.05%. This showed that the simulation result obtained in this study is in accordance with previous study. Next, the percentage difference between Design 1 and previous design is approximately 4%. Furthermore, the pressure losses between Design 1 and Design 2 are 0.3% and Design 1 achieved the range of acceptable values between 2500Pa to 3000Pa. The results of the velocity distribution, the evenness of each runner and the value of pressure losses shows that Design 1 met all the criteria and exhibited the best design improvement as compared to the previous design with 2% improvement.

Influence of Bionic Waveform Leading Edge Blade on Drag Reduction Characteristics of Mixed Pump

Because the helical axial flow gas-liquid mixing pump has the great advantage of conveying gas-liquid two-phase mixed medium, it has become the main core equipment for deep-sea oil and natural gas exploitation. The gas phase aggregation and bubble movement trajectory in the impeller channel have been widely studied, but the increase of medium flow resistance caused by flow separation has not been deeply discussed. Combined with the Euler multiphase flow model and the SST k-ω turbulence model, the numerical calculation of the helical axial flow gas-liquid mixed pump is carried out. Under design flow conditions Q = 100 m3/h, head H = 30 m, speed n = 4500 r/min, specific speed ns =213.6 r/min, and under different inlet gas content conditions, the influence of the bionic waveform leading edge blade on drag reduction characteristics of the helical axial flow gas-liquid mixed pump was investigated. By designing the blade with a leading-edge structure with different heights and pitches, the separation of the mixed medium and the suction surface is effectively suppressed, and the flow resistance of the medium in the 1/10 area of the inlet end of the blade is reduced. The results show that when the height A is 0.25%L and the pitch λ is 12.5%h, the maximum drag reduction rate in this region is 52.6%, the maximum increase in efficiency of the mixed pump is 2.2%, and the maximum increase in head is 4.8%. This study can provide technical support for flow drag reduction in gas-liquid mixed pump.

Design of beam collection system with high transmission efficiency and tunablity

A beamline is required to focus proton beams produced by laser plasma accelerator to high charge density spots for practical applications. The Compact LAser Plasma Accelerator (CLAPA) coupled with an image-relaying beamline has been built at Peking University. While the collection section of this beamline is an electromagnetic quadrupoles (EMQs) triplet with certain aperture, more than 71 % of the protons are lost in the inlet end face or vacuum tube wall of triplet due to their divergence angles. Here we show the development of a high transmission efficiency and tunable collection system in the beamline by adding two permanent magnet quadrupoles (PMQs) with magnetic field strengths of about 200 and 120 T/m respectively in front of the triplet. As a result, by monitoring the relative position of the PMQs and the currents of the EMQs, the focusing energy is able to be adjusted ranging from 2 to 10 MeV, and the transmission efficiency is 1.4 to 3 times as high as only collected by EMQs triple.