Pipe Bend Research Articles

Developing a Support Vector Regression (SVR) Model for Prediction of Main and Lateral Bending Angles in Laser Tube Bending Process.

The laser tube bending process (LTBP) is a new and powerful manufacturing method for bending tubes more accurately and economically by eliminating the bending die. The irradiated laser beam creates a local plastic deformation area, and the bending of the tube occurs depending on the magnitude of the heat absorbed by the tube and its material characteristics. The main bending angle and lateral bending angle are the output variables of the LTBP. In this study, the output variables are predicted by support vector regression (SVR) modeling, which is an effective methodology in machine learning. The SVR input data is provided by performing 92 experimental tests determined by the design of the experimental techniques. The measurement results are divided into two sub-datasets: 70% for the training dataset, and 30% for the testing dataset. The inputs of the SVR model are process parameters, which can be listed as the laser power, laser beam diameter, scanning speed, irradiation length, irradiation scheme, and the number of irradiations. Two SVR models are developed for the prediction of the output variables separately. The SVR predictor achieved a mean absolute error of 0.021/0.003, a mean absolute percentage error of 1.485/1.849, a root mean square error of 0.039/0.005, and a determination factor of 93.5/90.8% for the main/lateral bending angle. Accordingly, the SVR models prove the possibility of applying SVR to the prediction of the main bending angle and lateral bending angle in LTBP with quite an acceptable accuracy.

A three-dimensional solver for simulating detonation on curvilinear adaptive meshes

A generic solver in a parallel Cartesian adaptive mesh refinement framework is extended to simulate detonations on three-dimensional structured curvilinear meshes. A second-order accurate finite volume method is used with grid-aligned Riemann solvers for thermally perfect gas mixtures. Detailed, multi-step chemical kinetic mechanisms are employed and numerically incorporated with a splitting approach. The adaptive mesh refinement technique is applied to a mapped mesh using modified prolongation and restriction operators. The flux along the coarse-fine interface is considered in a correction procedure to ensure the conservation of the solver. The numerical accuracy, conservation and robustness of the simulations are verified and validated with suitable benchmark tests. The new solver is then used to simulate detonation problems in non-Cartesian geometries. A simulation is conducted of the three-dimensional detonation propagation in a 90-degree pipe bend. A detonation in a round tube is also simulated in a Galilean frame of reference. Both a rectangular mode and a spinning mode are observed in the simulations. In addition, the fundamental problem of detonation wave/boundary layer interaction is studied. The results show that the new solver can simulate high-speed reactive flows efficiently by the combined use of a curvilinear mapping with mesh adaptation.

Design and optimization study of discrete inclined ribs enhanced bend tube based on “Diamond” active cooling thermal protection systems of hypersonic aircraft

When the hypersonic aircraft cruises, the surface will generate huge aerodynamic heating. Aiming at the thermal protection of hypersonic aircraft, this paper presented a study on the thermal–hydraulic and thermodynamic performance of discrete inclined ribs enhanced bend tube based on the designed “Diamond” channel. Meanwhile, a comprehensive numerical investigation was carried out for different models. The fluid velocity was found to vary in the range of 0.1–3.5 m·s−1, with the corresponding Reynolds number ranging from 3600 to 127000. The inlet temperature of heat transfer fluid was set to 253 K. It was visible that double–symmetrical longitudinal swirl was generated under a single upper and lower arrangement (Model D), which led to the best cooling performance on the inner wall. The performance evaluation criteria (PEC) and efficiency evaluation criterion (EEC) reached 0.99–1.18 and 0.66–1.00, respectively. The effect of four geometrical parameters (height–width ratio(H/d), length–width ratio (L/d), group number of ribs (n), and tilt angle (α)) of which the ranges are 0.5–2.5, 1.0–4.0,6–15 and 0°–90°, separately, was explored. The results showed that the inner wall temperature decreased up to 4.4 K when the Reynolds number was 72000. The Nusselt number and friction factor increased about 9.9 %–28.8 % and 16.5 %–111.5 %. Efficiency evaluation criterion reached 0.43–0.96. It was found that the combination of parameters would significantly affect the distribution of longitudinal swirls under the influence of secondary circulation in the bend tube. Moreover, many pairs of small vortices near the wall could improve active thermal protection performance. After obtaining the fitting function through the artificial neural network (ANN), the genetic algorithm (GA) was applied to obtain the Pareto front. The design variable for the L/d = 3.19, n = 11, and α = 14.3° was selected as the optimal solution by the TOPSIS method. When Reynolds number is 72000, the corresponding Tin and ΔP were 261.86 K and 2471.2 Pa. The performance evaluation criteria and efficiency evaluation criterion reached 1.02 and 1.09, respectively. Furthermore, a design variable for the L/d = 3.0, n = 11, and α = 15° was given for ease of engineering. The present work verified the feasibility of realizing heat transfer enhancement by combining the secondary circulation with longitudinal swirls formed by bend tube and discrete inclined ribs and proposed a new design scheme of active cooling thermal protection systems (ACTPS).

Coolant leak rate through fatigue cracked pipe bend: An experimental and design standard based investigation

Leak-Before-Break (LBB) requirement plays a vital role in demonstrating the structural integrity of sodium-cooled Fast Breeder Reactor (FBR) piping system. Crack size at penetration (2CS), crack size that corresponds to detectable coolant leak rate (2CL), and unstable crack size (2CG) are the primary crack parameters associated with the LBB design of FBR piping system. The detectable leak rate through a piping system is directly related to the differential pressure (ΔP) and crack size. The design pressure of FBR piping systems is relatively low, resulting in a high value of CL. Considering the need for an optimum LBB design of the FBR piping system, an experimental approach is adopted to arrive at a realistic estimate of CL. Based on the experiments, a power-law type correlation can be derived to predict the value of CL as a function of ΔP. The evidence from this study points towards the conservatism present in the current FBR LBB design philosophy as per RCC-MRx A16. These observations have several implications for achieving an optimum LBB design criterion for an FBR piping system.

Bending Deformation and Ultimate Moment Calculation of Screen Pipes in Offshore Sand Control Completion

Horizontal wells, extended-reach wells, and multi-branch wells were often used to exploit subsea oil and gas efficiently. However, during the sand control screen completion of those wells, the sand control screen pipe was easily deformed. Failure occurred when passing through the bending section due to the large bending section in the wellbore trajectory. A parametric analysis model of the screen pipe was established based on ABAQUS and Python software under pure bending load first. Then, deformation patterns and mechanisms were identified and discussed. The effects of parameters on the screen pipe bending deformation patterns and the ultimate moment were analyzed. Finally, an empirical formula for calculating the ultimate moment of the screen pipe was established. The results showed that the deformation of the screen pipe was complex, and three deformation patterns were related to the hole parameters. Due to an increase in the diameter and number of circumferential and axial holes, the ultimate moment of the screen pipe gradually decreased, and the circumferential holes had a more significant effect on the ultimate moment than the axial holes. The established empirical formula could accurately calculate the ultimate moment of the screen pipe, and the average difference between the formula and numerical simulation results was 3.25%.

Uniaxial Eccentric Load Behavior of L-CFSST Composite Column

This study presents the mechanical behavior of L-shaped concrete-filled square steel tube (L-CFSST) composite columns under uniaxial eccentric compression. Nine specimens were tested and the effects of eccentricity, steel tube thickness, steel yield strength, and slenderness ratio were investigated regarding failure modes, ultimate load, load-lateral displacement curves, and load-strain curves. Test results showed that, under uniaxial eccentric load, these columns showed favorable mechanical properties and steel tubes showed strong cooperative working performance. There were two types of failure modes for these columns: local buckling of the steel tube or overall bending of the specimen. ABAQUS was used to simulate the loading process and the accuracy of the numerical simulation results was verified by comparing failure characteristics, load-displacement curves, and ultimate bearing capacity with the test results. The N/Nu-M/Mu curves of the columns under uniaxial eccentric load with different parameters were simulated by the finite element method. A simplified formula for predicting the N/Nu-M/Mu relationship was established based on the finite element analysis results, which might be a workable approach for designing L-CFSST composite columns in engineering practice.

Void Fraction of Air-Water Two-Phase Flows in a Vertically Placed Horizontal U-Bend

Experiments on air-water two-phase flows in a horizontal U-bend placed in the vertical plane were carried out to investigate effects of pipe bending on the void fraction. The inner diameter and the bend radius of curvature were 8 and 24.3 mm, respectively, so that the dimensionless bend diameter was 6. The flow patterns dealt with were plug, slug and annular flows. The void fractions in the bend and the straight section were measured by using quick-closing valves and the void fraction distribution was evaluated with an image processing method. The applicability of available correlations for the void fraction in the straight pipe was also discussed. For the straight pipe, the void fractions of the plug and slug flows can be accurately evaluated using the Smith correlation, whereas in the annular flow regime the Cioncolini and Thome correlation and the Mauro et al. liquid film thickness model give better agreement with the data. The bend void fractions in the downward and upward flows agree well with those for the pipe diameter of 26 mm given in literature, implying that the diameter effect on the void fraction is weak. The Usui et al. void fraction correlation gives reasonable evaluation for downward flows.

CFRP cylindrical tubes equipped with thin-walled semi-circular lateral corrugated inner stiffeners subjected to quasi-static latitudinal impact

Recently, versatile tubes with different cross-sectional cores have been suggested to reduce impact failures of protective structures. One method for improving cylindrical tube bending stiffness is using thin-walled corrugated cores. This paper investigates the effects of using semi-circular lateral corrugated stiffeners on the elastic behaviors of the CFRP cylindrical tubes subjected to quasi-static latitudinal impact. Based on suggested bending characteristics, analytical equations of elastic behaviors for the cylindrical tube equipped with a semi-circular lateral corrugated core have been derived. The equations are considered for the CFRP tubes stiffened with 4, 6, 8, and 12 semi-circular lateral corrugated waves. Obtained strain results conducted from low-velocity FEM analysis and impact experiments employing the GOM DIC software verified the derived equations with more than 82% accuracy. Additionally, it is found that the CFRP tube stiffened with a four-wave lateral corrugated core displays a positive impact failure of 74% compared to the non-stiffened tube.

Effect of U-bend on void fraction in subcooled boiling flow

U-bend is very common in heat exchangers to facilitate the pipe arrangement, whereas studies on boiling heat transfer in such a bend pipe flow are quite scare, hindering the accurate design of this heat exchanger type. This work studied subcooled boiling flow in U-bend pipes with emphasis on the point of net vapor generation (PNVG) and the void fraction distribution. A Eulerian−Eulerian two fluid numerical scheme was established and Rensselaer Polytechnic Institute wall boiling model was incorporated. After verifying the model by experimental data, numerical runs were conducted at 10.81 MPa, mass flux of 100–3000 kg/m2s, and heat flux of 100–3000 kW/m2. Results show that net vapor generation was postponed when PNVG located outside of bend section, while close to that of straight tube when it is within the bend. Compared with straight pipe, void fraction in U-bend pipe was initially smaller and eventually larger. This transition occurred at different axial positions as the location or curvature of U-bend varied. The delayed PNVG leading to reduction of void fraction. After PNVG, turbulent kinetic energy induced by secondary flow accelerated bubble departure from the wall thus yielded larger void fraction. A modified Saha-Zuber model was proposed by properly considering the bend influence on PNVG and distribution parameter. The modified model is competent to the prediction of void fraction distribution, and can serve the thermal-hydraulic design of heat exchanger involving U-bend.

Experimental investigation of preheating performance of lithium-ion battery modules in electric vehicles enhanced by bending flat micro heat pipe array

Lithium-ion batteries, the heart of electric vehicles (EVs), are subject to capacity attenuation and lithium plating at low temperatures, which is essential to preheat lithium-ion batteries at low-temperature ambient. In this study, a battery thermal management system (BTMS) was established to achieve integration of preheating and cooling at the module level through a bent flat micro heat pipe array (FMHPA). As a thermal bridge, the bending FMHPAs realize the separation of the coolant and the battery, non-interference of preheating and cooling, and small space occupation. Heat transfer characteristics of bending FMHPA, preheating performance of the BTMS, and the effect of insulation shell were studied experimentally. Results showed that the effective thermal conductivity of Z-shape bending FMHPA is 15,741 Wm-1K−1. The temperature rise rate can reach about 1 ℃/min at the ambient temperatures of −20, −10 and 0 ℃. The temperature differences at both cell and module levels are kept within 5 ℃. The insulation shell with a thickness of 20 mm can increase the temperature rise rate and temperature difference at module level by 41% and 35%, respectively, but with no obvious influence on the active cooling effect at high-temperature ambient.

Numerical investigation of Bi-model slurry transportation through horizontal pipe bend

Numerical investigation of Bi-model slurry transportation through horizontal pipe bend

Study on Hot Deformation Behavior and Bending Forging Process of 7075 Aluminum Alloy

Study on Hot Deformation Behavior and Bending Forging Process of 7075 Aluminum Alloy

Design of a shattered pellet injector and preliminary bench tests of Ne pellet formation for EAST disruption mitigation

Shattered pellet injection (SPI) technology has been demonstrated as a novel effective method for disruption mitigation in tokamaks. To further verify the superiority and reliability of this technology, in this study, a SPI test stand based on in-situ gas formation technology was designed and constructed for Experimental Advanced Superconducting Tokamak (EAST). A pellet producer, a gas feeding system, a pumping system, diagnostic units, and a shatter chamber have been developed and are served as the main components of the SPI test stand. We experimentally demonstrated that the SPI test stand developed in this study can be used for forming and accelerating impurity pellets. On the test stand, Ne pellets with a diameter of ∼5 mm were successfully formed, and their length was varied from ∼7 mm to ∼15 mm by changing the heating power of the heat sinks after the formation of the pellets. The feasibility of pellet shattering was verified using a shatter tube (inner diameter: 15.7 mm) in the shatter chamber. The results showed that Ne pellets with a velocity of ∼150 m/s could be broken into fragments without removing the propellant gas by passing them through a ∼20° bent tube. The SPI test stand developed in this study and the experimental results presented in this paper will serve as the technical basis for developing a reliable SPI system on EAST and will be a good reference for the development of such systems on other fusion devices.

超音波振動による高濃度空気輸送におけるベンド管閉塞防止効果

The vibration mode of bend pipe and the choking prevention effect in dense-phase pneumatic conveying has been investigated experimentally. The vibration mode has been showed that it has four antinodes for longitudinal direction, and eight for pipe cross section as designed, and the vibration amplitude has increased as increasing the input voltage. Therefore, it is possible to adjust the vibration amplitude easily by changing the input voltage. Then, the frictional force between the packed bed and pipe wall has been increased with increasing particle diameter. However, it has been reduced with ultrasonic vibration in spite of kinds of particles and pipe diameter. This means the possibility of choking can be removed with ultrasonic vibration in bend pipe as well as in horizontal pipe.

Application of the Temperature Oscillation Method to Laminar Flow in Straight Horizontal and Curved Minichannels

This work deals with the application of the temperature oscillation method to measure local values of the heat transfer coefficient in laminar flow in a straight horizontal pipe and in a pipe with a bend. This method, applied here for the first time in such experimental conditions, uses a time-varying heat flux as a boundary condition, which is a condition of the third kind. Since an analytical solution for such conditions could not be identified in the existing literature, a numerical study of this problem is applied here. Experimental data for a straight horizontal pipe confirm the numerical results within a reasonable level of error. Experimental measurements on a straight horizontal tube are consistent with predicted results in the literature for both total and local heat transfer coefficient values. The measurements on bent tubes show a very significant influence on the local values compared to the straight tube and in the overall values this change appears as an increase in the heat transfer coefficient.

Expansion of Sandwich Tubes With Metal Foam Core Under Axial Compression

Abstract In order to enhance the load-carrying and energy-absorbing capacity of the energy-absorbing structure, a new energy-absorbing mode of a metal foam-filled sandwich circular tube (MFSC-Tube) expanded by a conical–cylindrical die under axial compression is designed. An analytical model of expansion of the MFSC-Tube under axial compression is established, considering the bending, stretching, and strain hardening of inner and outer tubes as well as compression of the metal foam core. Subsequently, finite element calculations are performed. Both analytical solutions and deformation modes agree well with the finite element calculation results, which proves the validity of the analytical model. The effects of material and geometrical parameters on the expansion of MFSC-Tubes are considered in detail based on the proposed analytical model. It is found that the load-carrying and energy-absorbing capacity of the expansion of the MFSC-Tube can be enhanced by adjusting such parameters as the ratio of the foam thickness to the wall thickness of the metal circular tube and the semi-angle of the die. Last but not least, the specific energy absorption (SEA) of the MFSC-Tube under expansion is significantly improved compared with that of hollow tubes under expansion.

RANS-Based Modelling of Turbulent Flow in Submarine Pipe Bends: Effect of Computational Mesh and Turbulence Modelling

Pipe bend is a critical integral component, widely used in slurry pipeline systems involving various engineering applications, including natural gas hydrate production. The aim of this study is to assess the capability of RANS-based CFD models to capture the main features of the turbulent single-phase flow in pipe bends, in view of the future investigation of the hydrate slurry flow in the same geometry. This is different from the available literature in which only a few accounted for the effects of a combination of computational mesh, turbulence model, and near-wall treatment approach. In this study, three types of mesh configuration were adopted to carry out the computations, namely unstructured mesh and two structured meshes with a uniform and nonuniform inflation layer, respectively. To explore the influence of the turbulence model, standard k-ε, low-Reynolds k-ε, and nonlinear eddy viscosity turbulence model were selected to close RANS equations. Pressure coefficient, mean axial velocity, turbulence intensity, secondary flow velocity, and magnitude of secondary flow were regarded as the critical variables to make a comprehensive sensitivity analysis. Predicted results suggest that turbulent kinetic energy is the most sensitive variable to the computational mesh while others tend to stabilize. The largest difference of turbulence kinetic energy was around 26% between unstructured mesh and structured mesh with a nonuniform inflation layer. Additionally, a fully resolved boundary layer can reduce the sensitivity of mesh on turbulent kinetic energy, especially for a nonlinear turbulence model. However, the large gradient and peak value of turbulence intensity near the inner wall of the bend was not captured by the case with a fully resolved boundary layer, compared with that of the wall function used. Furthermore, it has been confirmed that the same rule was detected also for different curvature ratios, Reynolds numbers, and dimensionless wall distance y+.

Ovality measurement based on scanning point cloud for tube bend deformation analysis

Ovality measurement based on scanning point cloud for tube bend deformation analysis

Effect of bend-induced inlet distortion on a centrifugal compressor performance and stall inception

Bend pipes are usually installed upstream of a centrifugal compressor because of spatial constraints. With the interaction between radial pressure gradient and centrifugal force in bend pipe, a pair of counter-rotating vortices (Dean vortices) is formed after the fluids passed through the bend, and the shape of Dean vortices keeps changing in the straight pipe between the bend and compressor. The effects of the changed Dean vortices on the aerodynamic performance and stall inception of a centrifugal compressor are investigated with an experimentally validated numerical method based on four models, in which the distance of the straight pipe located between the bend and the compressor varies from 0D to 1D through 1/4D and 1/2D. The results show that as the straight pipe length increases from 0D to 1D, both the total pressure deficit at compressor inlet and the flow separations at inlet pipe symmetry plane are enlarged, and the mass flow rate distribution of full-annulus become more fluctuant. As a consequence, the compressor aerodynamic performance degrades and its maximum flow capacity decreases. More importantly, bend-induced inlet distortion has the effect of inducing/suppressing impeller stall inception, it depends on the location and intensity of swirl distortion and total pressure distortion. The low total pressure region located at impeller tip leads to reversed flow and stall inception, while the positive pre-swirl component in swirl distortion decreases the incidence and suppresses stall inception. These results provide a reference for the design of upstream inlet curved pipes of centrifugal compressors.

Numerical Simulation of Robotic Inspection–Induced Flow Field Disturbance in Bends and Tees

The analysis of pipeline flow fields and forces during inspection robot operation is the basis of most pipeline robot studies. In this study, the low-Reynolds-number k-epsilon model was used to numerically simulate the status of the pipeline flow field for an inspection robot operating in a pipe tee and pipe bend, which constituted the experimental group. A pipeline with no robot was set as the control group. The velocity, dynamic pressure, and static pressure of the pipelines were analyzed. A comparison of the results of the experimental and control groups revealed minor changes in the velocity and dynamic pressure of the pipeline flow field when the robot was operating; furthermore, the static pressure was found to increase significantly in the experimental group. Therefore, the presence of an inspection robot increases the load of the pipeline. This conclusion has significance for guiding the working state analysis of inspection robots in complex pipeline environments.