Inlet Pipe Research Articles

An improved model for predicting hydrate formation and deposition in horizontal annular flow

The formation and deposition of hydrates in pipelines form flow barriers, which affect the safety of offshore oil and gas transportation. In this study, an improved model of hydrate formation and deposition is established by considering the non-uniform distribution of liquid film and droplets resulting from gravity, which is a non-negligible factor in the accurate prediction of hydrate deposition in horizontal annular flow. The uneven distributions of the hydrate deposit thickness along the radial and axial directions in a horizontal annular flow were calculated using the proposed model. Three different deposition characteristics of hydrates along the radial direction were found: concave W-type, convex W-type, and Ω-type. Meanwhile, the radial hydrate deposit thickness gradually increased as the gas flow rate increased. With an increase in the liquid flow rate, a greater axial distance between the pipe section and inlet results in a clearer increase in the radial hydrate deposit thickness. In addition, a peak value of the hydrate deposit thickness occurs at a certain position in the axial direction. This study provides a theoretical basis for the prediction and prevention of hydrate blockages during offshore gas transportation.

Reduction of aerodynamic resistance of inertial-vacuum ash collector

THE RELEVANCE of the research topic is due to the existence of an environmental problem associated with harmful emissions into the atmosphere. The most highly efficient are electrostatic precipitators and fabric filters (~90-99.5% capture). Against the background of these devices, inertial one’s lag behind both in terms of their catching efficiency and the catching spectrum of the ash particle size distribution. The research carried out in the article is aimed at creating such an inertial apparatus that would have both minimal resistance and high efficiency. PURPOSE. Consider the possibility of reducing aerodynamic resistance by changing the design of the device, namely, by increasing the diameter of the inlet pipe in the inertial-vacuum ash collector. Consider a number of other ways to further reduce the aerodynamic drag of the apparatus. To identify the prospects and assessment of capital costs for the reconstruction of the ash collector. METHODS. When solving the problem, the method for calculating the dynamics of a dispersed flow in an inertial-vacuum ash collector, implemented by the MFD, was used. RESULTS. The article describes the relevance of the topic, considers the results of a numerical calculation. The calculation of the influence of boundary conditions, which include the flow rate at the inlet, thermal and hydraulic parameters of the flow of exhaust gases at the inlet to the ash catcher, in relation to the desired pressure drop across the apparatus, as well as the collection efficiency, was made. This article describes the process that results in a change in the hydraulic characteristics along the flow part of the IVAC. CONCLUSION. A change in the design of the apparatus leads to a decrease in the resistance of the IVAC, while these changes are extremely sensitive to the effect on the degree of purification. Calculations have shown that this method justifies itself in terms of reducing resistance. The pressure drops ranges from 279.8-1273 mm. water. pr. The convergence of the iterative calculation, taking into account the quality of the grid, provides flexibility, is achieved by fewer iterations, but the time spent on the calculation does not decrease.

Analysis of the Amount of Filling and Emptying Time Communal Rainwater Harvesting Tank (RWH)

Utilization of stagnant water storage tanks in Banjararum Village, Kalibawang District, Kulon Progo Regency with a total of 23 units needs to be optimized by using them as communal rainwater harvesting (RWH). The amount of time for filling and emptying the tank is an important aspect to be able to optimize rainwater used for daily needs. The aims of this research was to determine the effectiveness of the use of Communal PAHs applied in the community. This is analyzed through several stages, including determining the planning location unit, analyzing hydrological characteristics and analyzing the flow rate and duration of filling and emptying the tank using the Prandtl-Colebrook formula and the Bernoulli formula. Researchers took samples in Dusun Kisik by optimizing 2 roofs that can distribute rainwater of 27.09 m3/week for roof 1 and 27.19 m3/week for roof 2. Assuming 6 people live around the tank who use water storage every day, then the communal PAH can supply 3,000 liters within 52 minutes while the emptying process for distribution to other media takes 69 minutes. This difference is due to the different dimensions of the inlet pipe and outlet pipe. So that the effectiveness of the use of Communal PAHs applied in the community can be one of the recommendations in the provision of sustainable clean water.

Microplastic transport dynamics in surcharging and overflowing manholes

The transport of microplastics within urban water systems remains poorly understood, with little prior research on their behaviour within manhole configurations. This study represents the first to measure and model the transport dynamics of microplastics within circular and square manholes under different hydraulic scenarios. The transport and fate of polyethylene (PE) was quantified and compared to solutes (Rhodamine WT dye) using energy losses, residence time distributions (RTDs), and mixing models within surcharging and overflowing manholes. The bulk mass of solute and PE concentrations followed similar flow paths across all conditions except for 17.3 ± 7.9 % of PE mass that was immobilized in a dead zone above the inlet pipe for manholes with a surcharge to pipe diameter ratio ≥2. Consequently, these microplastics only exit after a significant change in hydraulic regime occurs, causing microplastics to be at risk of being contaminated over a prolonged duration. No significant mixing differences for PE and solutes were found between manhole geometries. The deconvolution method outperformed the ADZ model with goodness of fit (Rt2) values of 0.99 (0.60) and 1.00 (0.89) for PE and solute mixing, respectively. This establishes the deconvolution method as the most accurate and appropriate model to accurately predict microplastic mixing in manholes and urban drainage systems.

Ultra-long-distance transport of supercritical natural gas (SNG) at very-high mass flow rates via pipelines through land, underground, water bodies, and ocean

A detailed study of SNG transport using a computational model that accounts for compressibility and Joule-Thomson effects is presented, for the first time. It shows that the transport distance and mass flow rate of supercritical natural gas (SNG) - above the cricondenbar and cricondentherm, and beyond the anomalous state - can exceed far beyond that achieved or proposed under high pressure, dense phase conditions, thus far. As an example, SNG (average composition of USA/Canada gas), at 800 kg/s can travel, without recompression, to 4801 km. It is revealed that the pressure-drop and pumping power per unit length decrease asymptotically as the inlet pressure increases beyond 20 MPa; orders-of-magnitude lower than that at low pressures. The increase in inlet pressure, pipe diameter, and/or heat conductance of the pipe wall increases the distance travelled by SNG whereas the increase in mass flow rate and surrounding temperature has a negative effect, including the strengthening of Joule-Thomson cooling near the exit. SNG pipelines at ocean bottom offer many advantages, including shorter distances, isothermal flows (∼4 °C), and balance between the outer and inner pressures. Also, SNG delivery at 6 MPa can allow regional distribution without immediate recompression. SNG pipelines therefore offer enormous possibilities of energy-efficient transport of natural gas to far-distant intra- and inter-continental destinations, not feasible thus far, which is urgently needed for uninterrupted supply of natural gas and worldwide energy security.

Effect of separation space on the separation performance of cylindrical hydrocyclones

Cylindrical hydrocyclones have received considerable attention for the benefits of reducing misplaced fine particles, but less attention to the effect of separation space on separation performance. This paper investigates the effect of separation space on the flow field and separation performance of cylindrical hydrocyclone by integrating the cylindrical height and vortex finder depth as variables utilizing a TFM model. The numerical results suggested that the separation space affected the tangential and axial velocities of particles slightly, while a larger separation space implies an enlarged upward distance of particles moving with the internal swirling flow, increasing the probability of forming particle circulation flow. Accordingly, the coarse particle enrichment region moves toward the wall and bottom region by increasing separation space. The separation accuracy increases and the cut size decreases by increasing separation space, however, the separation effect deteriorates when the vortex finder depth is less than the inlet pipe height.

Case study of fire and explosion accident based on damage consequence and numerical results: Explosion medium traceability

Alcohol-based fuel is widely used in the catering industry due to the excellent economy, but its explosion risk has not been paid much attention in thermal engineering. In this paper, a serious fire accident caused by the leakage of civil alcohol-based fuel vapor in Northeast China is introduced in detail. A case study is carried out by means of on-site investigation and computational fluid dynamics (CFD) technology, and the accurate evaluation and reproduction of the multi-physical field loads are realized. There were two flammable and explosive gas leakage sources, liquefied petroleum gas and alcohol-based fuel, in the building during the accident. Which kind of gas was involved in the explosion process in the early stage of the accident and caused a major fire is an important part of the primary solution of the accident investigation team. In this paper, the damage consequences of the two gases after explosion were effectively restored by CFD. By comparing the on-site damage and numerical results, the explosion medium is identified as the alcohol-based fuel vapor and air explosive mixed gas in the gas cylinder room. The explosion process is that the sparks and high-temperature spatter generated during the welding process of the bracket ignite the methanol-air vapor near the inlet of the fuel tank, and the flame enters the upper gas-phase space of the tank from the inlet pipe and cause the explosion, resulting in a large amount of fuel splashing in the tank and causing fire. The key investigation techniques and research ideas provide an important reference for accident investigation and disaster analysis, and have scientific significance for revealing the accident cause and preventing similar accidents.

Mechanisms of low frequency pressure oscillation occurred in oxygen jet condensation based on height function method

In a propulsion system of cryogenic liquid rockets, low frequency pressure oscillation is an important topic on the oxygen jet condensation. It is a challenge to capture the numerical characteristic of pressure oscillation precisely, especially the frequency and amplitude. Aiming at the mechanism and excitation process of pressure oscillation, an oxygen jet condensation simulation is conducted by a novel mass transfer model based on the height function method. The height function method is used to calculate the interfacial curvature between gas-liquid, which is the key factor to determine the frequency of pressure oscillation. The new model is validated by a steam jet condensation simulation and the corresponding result is in great agreement with the experimental data. The research shows that the low frequency pressure oscillation is caused by the periodic condensation mass transfer rate of the continuous oxygen vapor plume, along with a GOX suck-back flow phenomenon in the gas inlet of condenser pipe. The excitation frequency of pressure oscillation is 10.6 Hz, consistent with the experiment data of engine test run. It is close to the natural frequency of propulsion system. It can be inferred that oxygen jet condensation might be one of the excitation source of self-excited Pogo vibration. These conclusions provide a theoretical basis for overcoming the Pogo vibration eventually.

Numerical study of the mixing characteristics in an air swirling fluidized bed with monodisperse and multi‐sized particles

AbstractPowder mixers are used in many industries. In the present work, a new type of air swirling mixer was designed and optimized with eight horizontally arranged inlet pipes at the tangential inlet angle of 35°. The mixing of multi‐sized spherical particles (2.0, 3.0, 4.0, and 5.0 mm) was numerically investigated in the air swirling mixer by coupled computational fluid dynamics–discrete element method. The numerical results showed that multi‐sized particles achieved comparable mixing performance to monodisperse particles. The Lacey index for multi‐sized particles increased initially, and then reached a maximum value at 0.824. The upward velocity of the particles, , increased initially, and then decreased to zero along the bed height. The maximum value of occurred at a height of 40 mm. Particle radial velocity was larger near the wall than at the mixer tube centre area. The smallest particles aggregated in three layers. The collision number of the particles reached a maximum at bed height of 120 mm, which was consistent with the position of the maximum stress of the particles against the tube wall.

Influence of Oslo crystallizer structure characteristics on crystallization process

AbstractThe liquid–solid multiphase flow in Oslo crystallizer was simulated by computational fluid dynamics (CFD) and described by Euler–Euler model and k‐ε turbulence model. The velocity field and solid phase concentration field in Oslo crystallizer with different structural elements were systematically studied. The results show that, within the range of 0–82.5°, the fluid velocity and axial mixing in the evaporation chamber are significantly affected by the inlet pipe structure, and the length of the central downcomer also has distinct impact on the crystal classification ability of the crystallizer. As the angle between the axis of the inlet pipe and the tangent line at the inlet point increases, the tangential velocity in the evaporation chamber decreases, the axial velocity near the wall increases, and the volume fraction of solid particles decreases. As the length of the central downcomer increases, the position of the vortex center gradually goes up and moves towards the wall. In order to obtain high‐quality products and extend the continuous operation cycle of the device, the angle between the axis of the inlet pipe and the tangent line at the inlet point should be 60–75°, and the distance between the central downcomer and the bottom of the crystallizer should be .8 m.

Improving mixing and renewal in drinking water storage tanks: lessons learnt and practical measures

ABSTRACT This paper investigates the effect of different types of structural and operational measures on water mixing and renewal time in circular and rectangular cross-section water storage tanks, aiming at a better understanding of the flow dynamics to find practicable solutions to improve their design, rehabilitation and operation. An experimental programme, including traditional tracer and dye tracer tests, was carried out in small-scale tanks for different configurations and operating conditions. Two tanks were tested with and without interior structures, with the inlet/outlet pipes at different locations and for constant and variable water level. The main findings are that: i) the most effective measure is operating with fill-and-draw cycles, however, for tanks operated nearly full structural measures are recommendable; ii) reducing the inlet pipe diameter and installing nozzles near the tank bottom improve the mixing conditions; iii) the use of baffles is recommendable when the inlet and outlet pipes are very close.

Inlet retrofitting improves the hydraulic performance of a waste stabilization pond

Wastewater is transitioning from being viewed as a waste to being utilized as a resource in the production of reclaimed water. Reclaimed water, obtained through waste stabilization pond treatment technologies, has the potential to offset potable water needs for irrigation purposes as well as fertilizers for crop growth. In developing countries, where waste stabilization ponds are widely used, a major issue is the lack of maintenance which can lead to considerable amounts of sludge piled at the bottom of the pond. This sludge accumulation reduces the treatment capacity of the waste stabilization pond and possibly, the treatment efficiency which is vital for reuse purposes. In cases for which desludging of the pond is a challenge, retrofitting the pond inlet can offer an alternative to improve pond hydraulic performance. In this study, two inlet retrofit geometries are investigated in a waste stabilization pond with significant sludge accumulation using computational fluid dynamics. It is seen that retrofitting the pond with a three-way pipe inlet increases the mean residence time of the pond from 21.9 days to 25 days over a single pipe inlet while significantly reducing the strength of short-circuiting.

Influence of non-uniform inflow on performance of reactor coolant pump and improved design

In Chinese Advanced Passive (CAP) series reactors, the two canned Reactor Coolant Pumps (RCP) are directly connected to the bottom of the steam generator (SG) rather than a longer pipe for the full development of inflow, which leads to a decrease in head and efficiency of RCP. However, the head of the RCP determines whether the reactor coolant system can circulate normally. The efficiency determines the power of cannedmotorstator. Overload power under limited size conditions will bring failure risk to the canned motor stator. With such a large impact, we first employed numerical simulation to investigate the influence mechanism of the non-uniform inflow and improve the RCP design, and then verified by experiment. It is found that the flow separation due to the SG asymmetrical structure and the abrupt change of cross section when linking to the inlet pipe is the main cause of non-uniform inflow. Accordingly, we proposed an improved RCP design which can effectively improve the head and efficiency of RCP by more than 1% under non-uniform inflow condition. This research reveals the formation mechanism of the non-uniform inflow of RCP and proposes the improved design scheme to improve the performance of RCP under the non-uniform inflow conditions for the first time, which provides guidance for the design of the RCP.

Modification of Ballast Filtering Device on John Lie Training Ship to Prevent Marine Pollution

This study aims to present appropriate selection methods for evaluation, analysis, and comparison between different ballast water treatment technology systems in order to make good decisions in selecting the most optimal treatment system. This research designed a ballast water filter device on the John Lie training ship to prevent marine pollution due to species movement through the ballast water transfer process by referring to the D2 standard of the IMO Ballast Water Management Convention. During the ballasting process, ballast water contains thousands of species of marine animals and plants that are carried in ballast tanks, causing problems for the marine environment and human health. The modification of the filtration tool designed by the researcher used a 0,1 mm and 0,01 mm net tied to the ballast tank inlet pipe using a clamp on the ballast pipe of the John Lie training ship. This can fully be used during the process of filling ballast water from port seawater to enter the ballast tank through this filtration system. The results shown after passing the filter with a total plate count of 36 microorganisms indicate that the filtration system designed by the researcher can meet the D2 standard of the IMO BWM Convention Regulation.

Reduction of sedimentation and water turbidity at intakes of drinking water treatment plants

ABSTRACT Sedimentation at intakes of drinking water treatment plants (DWTPs) clogs intake pipe inlets causing interruption of water supply and serious pump abrasion. It occurs due to river flow velocity (FV) decline which causes flow inability to carry sediment particles. On the other hand, high velocities increase water turbidity because they induce flow turbulence that diffuses bed sediment particles over the water depth. The diffusion causes turbid water withdrawal and consequent high treatment running cost. This paper aims to adjust FVs near DWTP intakes using river training works (TWs) to control sedimentation and turbidity. Road El-Farag DWTP intake was taken as a case study. Groin construction and riverbed dredging were proposed as effective TWs. A 2-D mathematical model (SMS) was used to simulate different scenarios of the TWs. The simulations aimed to increase the FVs near the intake area provided that they neither allow sedimentation nor bed scour. The study area with FVs ranging from 0.025 to 0.40 was simulated in a physical flume to investigate the corresponding water turbidity (WT) values. A Jar test was conducted to find a relationship between WT and alum doses at different FVs. This relationship determines the optimum alum dose that can minimize turbidity. SMS and flume simulations revealed that positioning of groins on the river bank opposite to the intake area combined with dredging near the intake managed to increase FVs that can prevent sedimentation and bed scour. Finally, a mathematical relationship between alum doses and FVs was established.

Pressure Drop Prediction Model of the Gas-Liquid Stratified Flow Development Section in the Horizontal Pipeline

Abstract The gas phase accelerating beyond the liquid phase caused by gas-liquid slippage cannot be ignored in short horizontal pipelines with undulation and inflow, and there is no method to calculate it. Therefore, a pressure drop prediction model for variable liquid holdup was developed in this paper. The theoretical model calculation results were validated using computational fluid dynamics. The effectiveness of the pressure drop prediction model has been demonstrated. The various pressure drop, liquid holdup, and development length laws were then examined. The findings indicate that: the pressure drop in the developed section of stratified flow is not only the friction pressure drop but also the acceleration pressure drop; the length of the stratified flow development section and pipeline pressure drop are more easily affected by the flowrate than the liquid holdup in the pipe inlet. Using the relevant data from coalbed methane horizontal wells as an example, the L/D of the development section is approximately 40–85 when the inlet flowrate is 0.8–1 m/s, and the inlet liquid holdup is 0.3–0.5. The pressure drop characteristics in the gas-liquid stratified flow development section are obviously different from those in the stable section. The development of a pressure drop prediction model for the stratified flow development section lays the theoretical groundwork for the investigation of gas-liquid two-phase flow in horizontal pipelines with short or undulating and inflow conditions.

Numerical Simulation on the Influence of Inlet Flow Characteristics on the Performance of a Centrifugal Compressor

Although inlet bent pipes are usually adopted due to limited installation space, the influences of different bend pipes on the inlet flow characteristics and performance of centrifugal compressors are still unclear. The numerical simulation of a centrifugal compressor is established and validated by experimental results with the case of a straight inlet pipe. Then, the internal flow characteristics of the centrifugal compressor with a 90-degree bent pipe (p90) and Z-shaped bent pipe (pz) are simulated and discussed. The results show that the adoption of two inlet bent pipes reduces the performance of the centrifugal compressor to a certain extent, which reduces more greatly with pz, with a maximum reduction of 6.82% in pressure ratio and 14.83% in efficiency, respectively. The pressure ratio and efficiency reduction of the centrifugal compressor both increase with the increment of distortion degree, which maintains the increasing trend as the flow rate increases, and the maximum distortion degree of p90 and pz reaches 0.0351 and 0.0479, respectively. The reduction degree of the pressure ratio shows a power–law relationship with the distortion degree, while the reduction degree of efficiency shows an exponential relationship with it. The flow characteristics at the outlet section of the inlet pipe affect the flow field distribution at the inlet of the impeller, and the distortion area ranges of the total pressure and axial velocity at the inlet of the impeller are near 72°–144° in the circumferential direction for p90, while those of pz are close to 108°–180° and 288°–360°. When the flow with a high distortion degree enters the impeller, a large area with high turbulent kinetic energy is formed in the downstream flow channel, resulting in an increase in the flow loss.

Pipe Flow Development and Transition in CoSmaPipe Facility

AbstractThe current research focuses on understanding the transition of pipe flow by using a triggering device. In particular, a transition rod was installed within the CoSma‐Pipe at the Brandenburg University of Technology Cottbus‐Senftenberg. The effect of the transition rod, which has a variable height perpendicular to the axis at the pipe inlet, was examined in a range of 2,500 ≤ Re ≤ 31,000 where Re is the Reynolds number based on the mean velocity, the diameter, and the air's viscosity. This study used constant temperature hot‐wire anemometry to measure the flow. The observed effect of the transition rod was compared to previously published work in which a ring obstacle was used. The main objective of this research is to improve our understanding of the transition of pipe flow by using a triggering device such as the transition rod. By studying the effect of the transition rod on the flow, researchers can gain valuable insights into the dynamics of the transition from laminar to turbulent flow and its implications for various practical applications. This could ultimately lead to the development of more effective ways of controlling and mitigating turbulence in piping systems, engines, turbines, and other applications.

Analysis on flow structure in a vortex pump under all flow rates

Abstract Vortex pumps are usually designed based on its inner flow model. Currently, the flow models of vortex pump just consider flow rate at the design condition, which results in low efficiency under off-design flow rates in practical engineering. Therefore, the main objective of this article is to build a flow model that takes into account the impact of flow rates. To reveal the flow mechanism of vortex pump, we provide refined flow field simulations for a vortex pump. Performance experiments were conducted to validate the numerical simulation method. The study found that the vortex structure in the non-blade cavity can be regarded as a Rankine-like vortex. The inflow range is limited to the hub diameter (45 mm), smaller than the volute inlet diameter (85 mm). The action radius of the forced vortex gradually decreases from the impeller side to the inlet side. The maximum radius of the forced vortex on the impeller side is determined by the impeller diameter. As the flow rate increases, the action radius of the forced vortex on the inlet side gradually increases, while the axial length of the vortex in the inlet pipe gradually decreases. Based on the study of internal flow, a new flow model is proposed.

Study on the aerodynamic performance of inlet pipe different bending radius of ram air system

In this paper, the bending radius deviation of the intake duct is studied. The computational fluid dynamics (CFD) method is used to evaluate the performance of the inlet by the coupling calculation of the internal and external flow of aircraft. Firstly, the CFD method is used to calculate the theoretical numerical model. The results show that when the pipeline flow is constant and the pipeline R/D decreases, such as from 1.84 to 1.3, the total pressure recovery decreases, especially when the pipeline R/D is less than 1.5, the total pressure recovery decreases rapidly. At the same time, the drag force of the pipeline does not change much, and the flow field of the inlet pipeline is analyzed to analyze the internal reasons for the total pressure recovery and flow rate change with R/D, which has important guiding significance for the application of batch production in future.