Search

The throttling process, as an important part of the heat pump system, plays a crucial role in the efficient and reliable operation of the whole system. This paper, taking the quasi two-stage compression high-temperature heat pump with green refrigerant HP-1 as the research subject, established the mathematical models of the circulatory system and electronic expansion valve by using MATLAB and considering the influence of the opening of electronic expansion valve and thermodynamic properties of the new green refrigerant. It simulated the matching characteristics of electronic expansion valve opening and flow rate under variable operating conditions, and fitted the HP-1 dimensionless flow coefficient correlation by power-law distribution using experimental data. The research results show that the electronic expansion valve with an elliptical conical body structure adapts to the throttling characteristics of the HP-1 high-temperature heat pump system under variable operating conditions. When the evaporating temperature varies from 50 ℃ to 90 ℃ and the condensing temperature varies from 60 ℃ to 120 ℃, the opening adjustment range of this type of valve body is from 49.8% to 69.8% for the main throttle valve, and from 41.5% to 56.0% for the injection throttle valve. The relative deviation of the fitted correlation results and the actual test data is between -7.8% and +7.5%, and the flow coefficient correlation can accurately predict the flow characteristics of the electronic expansion valve with a similar body structure. The selection of favorable electronic expansion valve matching refrigerant properties and the optimization of the electronic expansion valve control system are essential for the actual operating performance. This study provides a good research foundation for the selection of electronic expansion valves and the optimization of the control system for the HP-1 high temperature heat pump.

Shale oil is stored in nanoscale shale reservoirs. To explore enhanced recovery, it is essential to characterize the flow of hydrocarbons in nanopores. Molecular dynamics simulation is required for high-precision and high-cost experiments related to nanoscale pores. This technology is crucial for studying the kinetic characteristics of substances at the micro- and nanoscale and has become an important research method in the field of micro-mechanism research of shale oil extraction. This paper presents the principles and methods of molecular dynamics simulation technology, summarizes common molecular models and applicable force fields for simulating shale oil flow and enhanced recovery studies, and analyzes relevant physical parameters characterizing the distribution and kinetic properties of shale oil in nanopores. The physical parameters analyzed include interaction energy, density distribution, radial distribution function, mean-square displacement, and diffusion coefficient. This text describes how molecular dynamics simulation explains the mechanism of oil driving in CO2 injection technology and the factors that influence it. It also summarizes the advantages and disadvantages of molecular dynamics simulation in CO2 injection for enhanced recovery of shale oil. Furthermore, it presents the development trend of molecular dynamics simulation in shale reservoirs. The aim is to provide theoretical support for the development of unconventional oil and gas.

The purpose of this paper is to investigate the flow and pressure pulsation characteristics of hydrogen circulation pump under varying pressure differences. A dynamic mesh technology was employed to conduct an unsteady numerical simulation of the interior of the hydrogen pump. The pressure pulsation within the pump cavity area was analyzed using fast Fourier transform, and the unevenness of pressure and flow inside the pump under varying pressure differential conditions was specifically studied. The results reveal that interference between dynamic and static in the pump cavity, caused by meshing clearance between rotors and radial clearance between the rotor and pump cavity, leads to pressure pulsation peaks occurring at twice the rotational frequency at all monitoring points. Additionally, as the pressure difference increases, the exhaust flow rate at the outlet of the pump cavity decreases from 49.237 m3/h to 12.392 m3/h, while volumetric efficiency decreases from 85.95% to 32.3%. The article utilizes Fluent dynamic mesh technology to conduct transient simulations on four distinct pressure differential conditions of hydrogen circulation pumps, thereby obtaining the variation principle of the internal flow field under varying pressure differences and elucidating the influence of pressure differences on both the non-uniformity of pressure and flow rate. [Display omitted] • Analyzed the reasons for two pressure pulsations occurring in the pump chamber. • Studied the pressure field to perform a total of 4 suction and exhaust in one cycle. • The pressure unevenness coefficient descents with the rise of pressure difference. [ABSTRACT FROM AUTHOR]

A method for molecule‐sensitive, non‐contact and marker‐free 3D mapping of vertical falling liquid films using Raman spectroscopy is presented. Technical liquid films are common in many applications in the chemical industry such as columns, evaporators, dryers and absorbers/desorbers. Measurements of an aqueous sodium sulfate film on a plain surface with a small pyramid attached to it, as well as a pillow plate are presented using a 3D surface plot. Suppressing surface gloss as well as other optical reflections from the metallic backplates is realized by using only inelastic light scattering and mathematical background correction. The results show that liquid mapping with Raman spectroscopy is possible and 3D maps can be created from different structured surfaces. [ABSTRACT FROM AUTHOR]

Increasing demands on efficient airslides conveying in the fields of construction, agriculture, pharmacy and power require deep understanding of the flow characteristics of materials being conveyed. This study designs a full-scaled airslide test rig, in conjunction with an experimental method, to investigate the flow behaviour of two different materials, namely sand and flyash under vent and non-vent conditions. The flow modes of the sand and flyash are predicted based on the measured material properties and fluidisation. Furthermore, tests are conducted using the designed airslide, from which the flow is characterised by analysing the variations of the key parameters, including the mass flow rate, the superficial air velocity, the pressure inside the airslide and the flowing material bed height. The work shows the developed test rig and method are capable of characterising fluidised flow for airslide systems. [Display omitted]. • Predict the flow modes of sand and flyash using different theoretical models. • Develop a full-scaled airslide test rig and experimental method. • Conduct airslide experiments under variable operation conditions. • Characterise the flow of sand and flyash during airslide conveying. [ABSTRACT FROM AUTHOR]

To explore the influence of the flow straightener (FS) on the internal flow field of the three-phase jet fire monitor (TPJFM), this study conducted an analysis of the flow characteristics within the TPJFM. Through numerical simulations based on ANSYS/FLUENT, the velocity, turbulent kinetic energy, pressure, velocity uniformity, and outlet performance of the internal flow field of the TPJFM were evaluated for different FS installation positions, installation angles, and structures. Results show that, the structural form of the FS significantly influences the internal flow field. The advanced rectification capability of the FS can immediately return the fluid in the grid to a laminar flow state. However, the exchange of kinetic energy between the regions increases turbulent kinetic energy and reduces outlet velocity. The FS blade and symmetry plane of the powder pipe overlap can effectively reduce the turbulence kinetic energy generated by the powder pipe. Reasonable FS parameters can enhance the flow characteristics of the flow field and improve jet performance. These findings could serve as an important reference for designing an optimized TPJFM structure. [ABSTRACT FROM AUTHOR]

A design for a turbine pre-swirl system with impeller cavity is proposed to improve the quality of cooling air supplied to the turbine blades of an aeroengine. Impeller cavity is analyzed in order to increase the system pressure ratio with a low system power consumption at the system outlet. Theoretical and numerical investigation are used to investigate the flow characteristics in an impeller cavity pre-swirl system. The conclusions in this study indicate that the impeller structure can increases the pressure ratio by changing the power consumption and distribution of the absolute velocity in the impeller cavity and system outlet. To obtain high pressure ratio and low power consumption, the impeller should have a structure with a high outlet installation radius and low outlet angle. The highest increase in the pressure ratio compared with the empty cavity pre-swirl system is 6.4% and the corresponding increase in the power consumption is 2620 W. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flow characteristics of the primary side of the helical coil once-through steam generator (OTSG) have a significant impact on the safe operation of the reactor. Different from the land-based stationary working conditions, the flow of the primary side of the OTSG is influenced by sea waves and winds under ocean conditions. The rigid body motion model is used to calculate the flow of the primary side under different ocean conditions, including heeling, trimming, rolling, pitching, heaving, and combined conditions. The results show that under heeling and trimming conditions, the static pressure of the primary side is different from that under vertical conditions due to the influence of gravity, but its impact on the flow field is relatively small. Under rolling and pitching conditions, the mean flow velocity and pressure drop change periodically with the movement of the OTSG, and the smaller the sway angle, the smaller the variation amplitude of the mean flow velocity and pressure drop. Under the heaving condition, the variation amplitude of the mean flow velocity is greater than that under rolling and pitching conditions, and reverse flow occurs. Under the combined heaving and rolling condition, the mean flow velocity and pressure drop are influenced by the period and amplitude of both the two motions. [ABSTRACT FROM AUTHOR]

With a large number of railroad and highway tunnels opening for operation, the diseases caused by hidden lining defects are increasing. The study of flow characteristics of freshly mixed concrete during tunnel lining casting is the key to revealing the formation mechanism of hidden defects. This paper revealed the location of blank lining formation by investigating the circumferential and longitudinal flow characteristics of concrete in the vault during tunnel pouring to provide suggestions for improving the quality of tunnel lining pouring for the various projects. This paper adopted the method of indoor testing, selected the suitable working conditions and flow parameters, validated the accuracy of the test with a numerical simulation, and simulated the secondary lining pouring process of the tunnel arch from the circumferential direction and longitudinal direction. This revealed the flow characteristics of the freshly mixed concrete in the process of pouring the arch lining. The flow of concrete in the arch lining was basically characterized by two major features which were similar to the flow in the pumping pipe and the layered flow. It also revealed the relationship between the concrete flow rate, flow distance, and the location of the formation of the blank lining risk zone with the slump of the concrete, the pumping pressure, and the radius of the tunnel. [ABSTRACT FROM AUTHOR]

Copyright of Special Oil & Gas Reservoirs is the property of Special Oil & Gas Reservoirs Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Deepsea mining has been proposed since the 1960s to alleviate the lack of resources on land. Vertical hydraulic transport of collected ores from the seabed to the sea surface is considered the most promising method for industrial applications. In the present study, an indoor model test of the vertical hydraulic transport of particles was conducted. A noncontact optical method has been proposed to measure the local characteristics of the particles inside a vertical pipe, including the local concentration and particle velocity. The hydraulic gradient of ore transport was evaluated with various particle size distributions, particle densities, feeding concentrations and mixture flow velocities. During transport, the local concentration is larger than the feeding concentration, whereas the particle velocity is less than the mixture velocity. The qualitative effects of the local concentration and local fluid velocity on the particle velocity and slip velocity were investigated. The local fluid velocity contributes significantly to particle velocity and slip velocity, whereas the effect of the local concentration is marginal. A higher feeding concentration and mixture flow velocity result in an increased hydraulic gradient. The effect of the particle size gradation is slight, whereas the particle density plays a crucial role in the transport. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The jet impact‐negative pressure deamination reactor (JI‐NPDR) is a new type of continuous and efficient deamination equipment. The study of the random flow pattern of porous jet impingement in the reactor under negative pressure conditions is an important issue. In this work, the signal processing method based on wavelet transform is used to analyze the characteristics of random flow signals in the reactor. Meanwhile, an analog similar signal is built and three sets of Gaussian white noise with various signal‐to‐noise ratios are employed via the MATLAB platform. Based on the adjustment of threshold function, threshold, decomposition level and other parameters of wavelet transform, the noise ratio (SNR) and mean squared error (MSE) are used to evaluate the wavelet denoising effect. And then, the optimal denoising scheme for the obtained signal will be applied in processing the vacuum flow signal collected inside the deamination reactor. Subsequently, the 8‐layer wavelet decomposition is investigated by using sym7 as the wavelet basis, soft threshold function, and heursure threshold for signal denoising. Then, the analog signal is fed back through the results of the actual signal denoising, and the number of wavelet decomposition layers is adjusted from 8 to 9 layers to optimize the original wavelet denoising combination. By analyzing the low‐frequency and high‐frequency parts of the signal spectrum before and after denoising, it was found that wavelet transform can effectively denoise the fluid signal in the reactor. [ABSTRACT FROM AUTHOR]

Mortise and tenon are very important parts of gas turbine dealing operation safety. Additionally, the temperature distribution of the turbine blade and disk is affected by the heat transfer characteristics in its gap. Then, the S-shaped mortise and tenon gap were numerically studied under rotating conditions, and the flow and heat transfer characteristics were analyzed. First, the heat transfer coefficient (HTC) of the mortise and tenon surfaces was measured with thermochromic liquid crystal. Then, the numerical method was verified using the test results, and the grid independence analysis was conducted. Finally, the flow and heat transfer characteristics of the gap under static and rotating conditions were numerically studied, five different Reynolds numbers (Re = 15,000, 20,000, 25,000, 30,000, 35,000) and five gap widths (d = 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm) were conducted and analyzed in detail. The results show that, under the rotating condition, the pressure distribution in the gap is different from that of the static condition; the pressure increases along the radial direction due to the action of centrifugal force and reaches its maximum value at the corner of the "S" shaped structure. With the increase in Re, the heat transfer intensity of the gap increases gradually. Additionally, the heat transfer intensity of the gap increases with an increase in its width. [ABSTRACT FROM AUTHOR]

In this paper, a novel air bleeding aerodynamic diffuser is proposed based on the study of the traditional dump diffuser. The performance and flow characteristics of these two diffusers are compared and analyzed using the numerical simulation method, which is validated by experiments. The effects of length and hole diameter on the diffuser's performance are also studied. The results reveal that, at inlet Mach numbers of 0.15, 0.20 and 0.30, compared with the dump diffuser, the total pressure loss coefficient of the new diffuser decreases by 18.52 %, 15.05 % and 40.23 %. The performance of the air bleeding aerodynamic diffuser with varing lengths has little change, which means its aerodynamic capabilities are still capable of meeting the requirements of advanced combustion chambers. As the diameter of the air bleed hole increases, the total pressure loss coefficient of the diffuser decreases and becomes gentler. [ABSTRACT FROM AUTHOR]

Ice slurry is broadly used as the medium for refrigerating medium, which can effectively reduce energy consumption. However, the change of ice particle size makes the flow properties of ice slurry more complicated, which limits its application in cooling system. A coupled model combining CFD and PBM techniques is developed in this article to effectively depict the variations in ice particle size and the flow of ice slurry. Based on this model, the flow properties of ice slurry isothermally in horizontally placed straight and U-shaped pipes are studied. It is found that velocity determines the degree of agglomeration and fragmentation of particles. The particle fragmentation effect is enhanced and the particle size is reduced as the flow velocity increases, which promotes the homogeneous particle distribution. With increasing the ice content, the size of particles and particle agglomeration increases. And the ice particle size presents a symmetrical distribution. The larger the initial average particle size, the weaker the agglomeration effect, and conversely the weaker the fragmentation effect. In the bending section of the U-shaped tube, the agglomeration effect between particles becomes stronger as the flow velocity decreases and the ice volume and curvature ratio increase. • A CFD-PBM coupled model is developed suitable for describing ice slurry flow. • The agglomeration efficiency is introduced in agglomeration kernel model. • The impact of ice particle size evolution on ice slurry flow behavior is analyzed. • The ice particle size evolution in U-shaped tubes is studied. [ABSTRACT FROM AUTHOR]

The plunger valve has an important role in a large compressor system as its operating characteristics directly affect the aerodynamic boundary condition of the compressor equipment. In this study, dynamic modeling and analysis method of the plunger valve are proposed for an accurate control of the system. By considering the interaction between the dynamic flow in the valve and actuator action, a lumped parameter model for the fluid-structure interaction force and multibody dynamic model of the actuator are developed based on intrinsic correlation parameters. A combination analysis to simultaneously predict valve flow and actuator dynamic characteristics is proposed. The predicted results are in a good agreement with experimental data, which validates the proposed model and analysis method. The analysis results show that the coupling effect between the valve flow and actuator is significant and has an important role in valve control, particularly when the valve opening is smaller. Compared to the experimental data and computational fluid dynamics results, the presented methods are accurate for valve control and effective for prediction of flow rate. [ABSTRACT FROM AUTHOR]

We have investigated the use of a novel dual-stage firefighting strategy, where an inert gas is deployed as a carrier agent to discharge foamed water, obtained by mixing environmentally friendly surface-active agents. Here we also report specifically on some in-house built practical strategies. With a view to gauging the relative fire suppression efficacies of the selected agents, each one was discharged as a fine spray onto fires involving hexane, and also optionally where a typical Li-ion battery electrolyte acted as the fuel. In summary, it can be inferred that the air- or nitrogen-detergent formulations showed enhanced fire suppression attributes, in small-scale experiments, as compared with the aqueous medium alone. Furthermore, in almost all cases, the fire extinction property can be attributed mainly to the physical phenomena, produced by the flow of the inert gas, or air and enhanced wettability of the medium. Given that the fire tests were done at a relatively small scale, no definite conclusions can be drawn than those provided above; however, this study warrants further investigation, especially, at a larger scale. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In response to growing environmental and ecological awareness, eco-friendly in-stream structures such as vanes have been implemented in different parts of the world to enhance stream conditions. FLUENT (ANSYS) was used to perform three-dimensional large eddy simulation to investigate the effect of the vanes permeability rate on flow characteristics. To evaluate the numerical model accuracy, numerical and experimental free surface profiles compared. It is observed that simulated free surface profiles agree reasonably well with measured values. The effect of different permeability rates is obvious in the flow characteristics such as depth-averaged velocity distribution, tip velocity variations, formation of the secondary flows in the flow field, turbulent kinetic energy, and mean kinetic energy contours. On average, maximum velocity values in the flow field is 1,54 times the approach velocity. Tip velocity decreases up to 30,6 % for the 70,0 % permeable vane. Maximum turbulent kinetic energy and mean kinetic energy for the 70,0 % permeable vane decrease up to 58,0 % and 43,3 %, respectively. Generally significant velocity and flow pattern variations around the impermeable vane can be attributed to the local effect of the vane structure and channel cross sectional constriction in comparison to the permeable vanes. [ABSTRACT FROM AUTHOR]

The stable transportation of pulverized coal in the vertical pipe is significant for the operation of the gasifier. There are few studies on the flow characteristics and flow pattern transition of particles in vertical pipes with small diameters. This paper has modeled and analyzed the flow characteristic of powder in dense-phase pneumatic conveying through 25 mm vertical pipe using CFD. Firstly, the grid independence is verified to determine the optimal mesh size. Then, the influences of different solid loading ratios (SLRs) and conveying velocities on particle flow characteristics, flow stability, and flow pattern transition are investigated. The results show that the flow pattern in the vertical pipe changes from annular flow to uniform flow at high SLR and low conveying velocity. Moreover, the evolution regulation of resistance characteristics under different conveying velocities is further revealed. Considering the conveying stability and economic benefit, the most suitable conveying velocity is 6 m/s.

In recent years, jacket foundations have been increasingly employed in offshore wind farms. Their complex design comprising piles and trusses poses challenges for conducting comprehensive flow field measurements using physical experiments. Consequently, the influence of the flow field on local scour around these foundations remains unclear. Therefore, numerical simulation methods are essential to depict the surrounding flow characteristics. This study utilizes large eddy simulation (LES) turbulence models within OpenFOAM to simulate the flow field around jacket foundations on flat-bed and equilibrium scour bathymetry. A flume experiment was conducted for numerical model establishment and validation. The close agreement between experimental and numerical results indicates that the LES model accurately reflects the flow patterns around the jacket foundation. Time-averaged and instantaneous flow characteristics, average kinetic energy (AKE), turbulence structure, and bed shear stress were analyzed. The results indicate that flow intensity is reduced due to the shielding effect and energy dissipation by the truss structure of the jacket foundation. Furthermore, the AKE of the flow upstream of the rear piles decreases by 18.9% in the flat-bed state and 28.0% in the equilibrium state, indicating more energy dissipation and less scour at the rear piles in the equilibrium state. The research findings offer valuable insights into the design and scour protection strategies for jacket foundations.

Kaplan turbine units can adjust their blades to achieve wider outputs without a significant loss of efficiency. The combination of guide vane angle (GVA) and blade angle (BA) is selected based on efficiency curves obtained from cam tests. However, the vibration characteristics are not considered in the test. The vibration and flow characteristics are complex with different combinations of guide vane and blade angles. Different cam relation selection principles lead to varying machine vibration and flow characteristics. In this research, the flow and vibration characteristics were obtained by means of field test and numerical simulation. Vibration, pressure pulsation, and other stability indicators have been extracted and investigated under off-cam conditions. The flow and variation rules of different indicators have been thoroughly researched. The findings suggest that the magnitude of vibration in the X direction surpassed that in the Y direction for the head cover, upper frame, and lower frame under 22 experimental conditions. The disparity between the head cover and upper frame in both directions was not significant, whereas a substantial contrast existed between the lower frame in the X and Y directions. The calculation results indicate that when the guide vane angle was small, vortices appeared near the high-pressure edge of the runner in the vaneless region and caused disorganized flow lines in the runner, and this complex vortex behavior led to multiple frequency components in the pressure pulsation frequency domain. The conclusions provide references for the designers of Kaplan turbine units and improves the operating safety of Kaplan turbine power stations.

In order to determine the recommended flow velocity for the safe and energy-saving transport of ice-slurry-type light particle slurries, it is necessary to study the flow characteristics of light particle slurries, especially the critical flow velocity. Therefore, in this paper, a numerical simulation method based on the mixed turbulence model with the RANS (Reynolds averaged Navier Stokes) equation is used, and a new concentration distribution method is proposed for the first time to derive the critical flow velocity, as follows: the flow velocity of the light particle slurry when the ratio of the solid volume fraction vf at the position of 0.08D above the bottom of the pipeline to that at the center of the pipeline, vf/vf(y) = 0.75, is taken as the critical flow velocity. The flow changes in the slurry (polyethylene particles with a density of 922 kg/m3 and water) under 0.1–1.0 m/s (at intervals of 0.1 m/s) were investigated experimentally, and the pressure drop data obtained from the experiments were used to determine the recommended flow rate for safe and energy-saving transportation of the light particle slurry. The pipe diameter used for the experiments and simulations was 28 mm, and the solid-phase particle sizes were 0.3 mm, 0.4 mm, and 0.5 mm, with solid-phase contents of 5 vol%, 10 vol%, 15 vol%, and 20 vol%. In addition, the experimental and numerical simulation results show that an increase in solid-phase content and particle size leads to an increase in critical flow velocity.

This research investigates the cavitation wear phenomena in a direct-acting pressure relief valve (PRV), where the poppet of the PRV is subjected to unseat at over-pressure conditions of the hydraulic system. The poppet unseat results in to sudden fall in system pressure and hence, the expansion and burst of pre-existing tiny air bubbles and thus the cavitation. To reduce the occurrence of cavitation, three different poppet shapes i.e. chamfered conical, blunt, and spherical heads is proposed for replacement over the existing conical head. To investigate the effect of different poppet shapes, the CFD simulation of the simplified 2-D fluid flow geometry is considered and the same is validated through experiments. Further, the validated model is used to investigate the cavitation parameters during the PRV operation at different opening conditions. The results showed that the blunt head PRV poppet offers comparatively lesser cavitation intensity for hydraulic systems subjected to frequent over-pressure conditions. [ABSTRACT FROM AUTHOR]

To reveal how aircraft affects the internal flow of the ejector nozzle, we have constructed three model types in this article. These include the model of SR-71 aircraft, the model that only contains ejector nozzle with third auxiliary valve, and the model that integrates the previous two. The results showed that in the transonic regime (Ma = 1.2), the third auxiliary flow mainly stems from the boundary layer of the aircraft body. Indeed, a large-scale flow separation phenomenon near the third auxiliary door may require a more nuanced description. The mainstream flow is always in an overexpansion state and results in a Mach plate structure at the exit of the nozzle. However, after integration, the rates of the third auxiliary and the secondary flow are reduced by 18.15% and 5.26%, respectively. Meanwhile, the mainstream flow demonstrates higher overexpansion levels, the position of the Mach plate further downstream changes, and the thrust coefficient decreases by 1.75%. It is worthwhile noting that a strong pressure gradient occurs in the circumferential direction near the connecting structure, which induces lateral flow. This lateral flow breaks away from the wall under the reverse pressure gradient of the nozzle, thus forming three vortex pairs. [ABSTRACT FROM AUTHOR]

The objective of this work was to study fresh concrete flow in the L-box test, predict the final deposit shape after flow stoppage and estimate the yield stress. This is very useful for controlling concrete casting in real structures, detecting problems and developing solutions on time. Concrete rheometers used for measuring the rheological parameters of concrete are expensive, not always available and can lead to measurement disparity. To overcome these issues, an effective method is to analyse concrete flow phenomena physically and solve the problem analytically based on L-box measurements. In the first part of this work, fresh concrete was considered as a homogeneous yield stress fluid moving under the effect of its self-weight. By developing momentum equations for an incompressible fluid, a theoretical approach was used to study three probable final shapes depending on the concrete rheology. Expressions were established for predicting the final shape and the yield stress. In the second part, the results obtained were compared with those of previous models and good agreement was found, thus validating the proposed approach. This study provides a consolidation of rheometer results, allowing evaluation and perhaps a calibration to reinforce their validity. [ABSTRACT FROM AUTHOR]

Helically coiled pipes are widely used in many industrial and engineering applications because of their compactness, larger heat transfer area per unit volume and higher efficiency in heat and mass transfer compared to other pipe geometries. They are commonly encountered in heat exchangers, steam generators in power plants and chemical reactors. The most notable feature of flow in helical pipes is the secondary flow (i.e., the cross-sectional circulatory motion) caused by centrifugal forces due to the curvature. Other important features are the stabilization effects of turbulent flow and the higher Reynolds number at which the transition from a laminar to a turbulent state occurs compared to straight pipes. A survey of the open literature on helical pipe flows shows that a good deal of experimental and theoretical work has been conducted to derive appropriate correlations to predict frictional pressure losses under laminar and turbulent conditions as well as to study the dependence of the flow characteristics and heat transfer capabilities on the Reynolds number, the Nusselt number and the geometrical parameters of the helical pipe. Despite the progress made so far in understanding the flow and heat transfer characteristics of helical pipe flow, there is still much work to be completed to address the more complex problem of multiphase flows and the impact of pipe deformation and corrugation on single- and multiphase flow. The aim of this paper is to provide a review on the state-of-the-art experimental and theoretical research concerning the flow in helically coiled pipes. [ABSTRACT FROM AUTHOR]

The rotor of a high-power water-filled submersible motor rotates at high speed in liquid during operation. while working motor internal air gap fluid flow in complicated cases, fluid flow characteristics is not only directly affect the water of the rotor friction loss, also affect the submersible motor cooling effect. In this paper, the fluid field in the inner cavity of submersible motor is deeply studied. The air-gap fluid grid model was established according to computational fluid dynamics, and the influence of air-gap on fluid velocity of submersible motor was studied based on ANSYS and FLUENT software. The results show that the pressure decreases linearly after the cooling water enters the motor air gap, the maximum pressure is located at the air gap inlet and the minimum at the air gap outlet; the outlet and inlet pressure of the air gap fluid grows with the increase of the air gap inlet fluid flow rate, and the growth rate tends to decrease in different degrees. The research results provide a basis for the design of submersible motor and the determination of the reasonable flow of fluid in the motor. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Most oilfields in our country adopt heating gathering and transportation, which causes huge energy consumption. Crude oil gathering and transportation without heating is one of the research hotspots in the field of oil field energy saving. This research group proposed the concept of hydraulic suspension transportation of crude oil, in which the gelled crude oil is formed into dispersed particles by technical means, and is fluidized by means of hydrodynamic force. It is transported in a suspension state without heating. The hydraulic suspension transport simulation device for gelled crude oil was developed according to the actual production of crude oil. The device not only serves the development of graduate students' practical abilities in the field of multiphase flow and the implementation of open experiments in undergraduate fluid mechanics but also enables the experimental research on the shaping effect of gelled crude oil, the flow characteristics of water-gelled crude oil under different conditions, and contributes to the progress of relevant scientific research and technological levels. [ABSTRACT FROM AUTHOR]

The flow characteristics in reciprocating pump-pipe system are inevitably subject to the interaction effects between pump and pipeline. In this paper, a parametric interaction model of flow characteristics in reciprocating pump-pipe system is presented by considering the coupling effect and leakage characteristics. The analytical solutions of the proposed interaction equations are deduced with the aid of the harmonic balance method. A testing platform of a simplex plunger reciprocating pump-pipe system is employed for validating the proposed model. The experimental tests under different operating conditions are used to compare the pressure pulsations and discharge flow rates from analytical solutions. It is observed that the analytical solutions are in good agreement with the test data and numerical results, and the prediction error is within 13%, thus validating the presented interaction model and analytical solutions. The interaction effects as well as the flow characteristics in reciprocating pump-pipe system are analyzed and discussed using the proposed model. It is found that the opening of flow control valve has remarkable influence on the relationship between flow rate and operating speed of reciprocating pump. The pressure pulsation within a pipe is closely related to and significantly affected by the plunger-to-cylinder clearance and the plunger stroke. [ABSTRACT FROM AUTHOR]

Microchannels are small-scale channels with unique properties that make them useful in various fields, such as electronics, biomedical engineering, and chemical engineering. This research paper investigates the effect of microchannel geometry on fluid flow behavior at different values of the Reynolds number. A rectangular microchannel with a pattern of obstructions and water as the working fluid was used in this study. Computational fluid dynamics (CFD) simulations were used to investigate the impact of different channel geometrical configurations and different values of the Reynolds number on fluid flow behavior. The results showed that the channel geometrical configuration and the Reynolds number significantly affect fluid flow behavior. A geometry with increasing obstruction heights led to higher values of pressure drop than the geometry with decreasing obstruction heights. This study provides valuable insights into microchannel flow behavior and can be used for the development of optimized microchannel designs for diverse applications. [ABSTRACT FROM AUTHOR]

To developed clean, efficient and economical filing materials for filing Ming requirements, LCPB was prepared by mixing loess, lily ash and a certain amount of gangue. The rheological properties, flow characteristics, UCS and damage evolution law of LCPB were investigated through a series of laboratory tests and numerical simulation. The results showed that the LCPB slurry with different ratios conformed to H-B rhea logical model, yield stress increased with the increase of loess dosages (92. 41-155. 42 Pa),loess dosages is greater than 15 wt.% to meet the gangue settlement requirements, slump increased with the increase of loess dosages and then decreased(LF-1- LF-4-LF-6 : 219-276-258 mm),and 28 d compressive strength decreased with the increase of loess dosages(4. 09 -2. 14 MPa). The 28 d compressive strength decreased with the increase of loess dosages(4. 09-2. 14 MPa), and the slump and compressive strength satisfied the ailing requirements of nine. The damage mode of the filing shifted from the dominant tenia damage to the dominant shear-tendon damage with the increase of loess dosages, and the damage stage showed the characteristic of the drastic energy accumulating nan front of the peak and then transforming into the dissipative energy icing rapidly. [ABSTRACT FROM AUTHOR]

A lot of work has documented the significance of fluid-flow uniformity on the thermal-hydraulic performance of the micro-channel heat sink. The purpose of this work is to optimize the shape of inlet/outlet headers of a micro-channel heat sink to improve the flow distribution characteristics using the back propagation neural networks combined with the genetic algorithm as the surrogate model. The slanted edge of the inlet header is defined as the quadratic parabola instead of straight line. Meanwhile, the shape of the parabola is optimally designed for different flow rates. The 40 training sample points and six testing sample points on different geometry structures of inlet header are designed by the Latin hypercube sampling method. The 3-D CFD calculation is performed for all models. The objective function is defined as the non-uniformity of the fluid-flow. It is found that the prediction of the genetic algorithm back propagation for the fluid-flow distribution is capable of obtaining objective function values within the designed space. Through the optimizations, the non-uniformity of the optimal inlet header structure can be reduced by 52.43% to 33.17% for the inlet velocity of 0.05 m/s to 0.1 m/s, respectively, compared to that of the original design. The results demonstrate that the parabolic treatment for the slanted edge of the inlet header as well as structural optimization can greatly improve the flow uniformity of the micro-channel heat sink. [ABSTRACT FROM AUTHOR]

Copyright of Oil Drilling & Production Technology / Shiyou Zuancai Gongyi is the property of Shiyou Zuancai Gongyi Bianjibu and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The flow characteristics of multistage centrifugal pumps in transporting gas–liquid mixed media are highly complex; particularly, the unstable flow of the passage at high gas contents exacerbates energy losses, leading to a decrease in pump efficiency and stability. The excess energy loss in the pump is not conducive to the concept of sustainable development. In this study, a numerical simulation of multistage centrifugal pumps was conducted based on the Euler–Euler heterogeneous two-fluid model. This research revealed that gas primarily accumulates on the suction side of each impeller stage, and the gas distribution decreases progressively with each stage. As the interstage gas volume fraction (IGVF) increases, the gas accumulation within the pump becomes more pronounced. The gas volume fraction of each component is negatively correlated with the flow rate, and the change is more obvious in the impeller. The turbulent kinetic energy distribution inside the impeller is positively correlated with the gas distribution. There is a large fluctuation at 0.6Q and 0.8Q, and the distribution of the impeller vortex is asymmetric. However, the impeller has a lower turbulent kinetic energy near 1.2Q, which indicates that the emergence of gas in the medium increases the high-efficiency area of the multistage pump to a certain extent. This paper reveals how the gas phase is distributed, how energy is lost in the multistage pump, and the gas–liquid two-phase flow characteristics in the pump, which have certain guiding significance for the design and working-condition adjustments of the gas–liquid mixed pump. [ABSTRACT FROM AUTHOR]

Copyright of China Sciencepaper is the property of China Sciencepaper and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to promote the development of new power systems and the consumption of clean energy, pumped storage hydropower stations tend to become increasingly larger in capacity and higher in head height. In this paper, a three-dimensional model of the full channel of a high-head pump turbine is established, and the influence of the gap thickness between the runner crown and the headcover on the internal flow field characteristics, pressure fluctuation characteristics and axial water thrust are studied by means of computational fluid dynamics (CFD). The results indicate that the area where the pressure and velocity vary greatly in the flow field of the crown clearance is at the seal of the labyrinth ring. In addition, the pressure balance pipe has a greater impact on the pressure and flow rate of the water passing through the clearance, and the crown clearance near the pressure balance pipe generates a vortex, resulting in energy loss. Decreasing the thickness of the clearance has no obvious effect on the pressure on the flow-passing components, and increasing the thickness of the clearance has a great change in the pressure values at the upper crown inlet, in front of the labyrinth ring of the crown and in front of the labyrinth ring of the band. The upper part of the vaneless area, the crown inlet and the lower ring inlet are close to the runner; hence, the interference from the rotating parts is the strongest. The effect of increasing the thickness of the crown clearance on the axial water thrust is greater than that of decreasing the thickness of the crown clearance. The pulsation frequency of the axial thrust on the crown, band and blade and the resultant force of the axial thrust increase with the increase in the crown clearance thickness. [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)