Tube Parameters Research Articles

CFD Investigation into Flow Characteristics of a Special Splash Lubrication in Light Helicopters

Lubricating oil flow characteristics are the primary concern in the main reducer of light helicopters. To improve the lubricating performance of the main reducer, a special lubrication system is innovatively constructed by adding two oil-guiding tubes to the hub of the output gear, and the influence of the oil-guiding tubes is investigated through CFD (computational fluid dynamics) techniques. A CFD model of the gearbox integrated with the VOF (volume of fluid) technique was established to explore the flow characteristics of the oil–air two-phase flow inside the gearing system. To validate the proposed CFD model, a specialized testing rig is devised and manufactured to examine the features of oil distribution. The effects of the structure parameters of the oil-guiding tubes and operating conditions on the lubrication performance are explored. Comparing experimental and numerical findings reveals that the inner diameter of the oil-guiding tube and the rotational speed of the driven gear have a significant influence on the lubrication performance. In contrast, the length of the installation end of the oil-guiding tube, its angle, and the oil-immersion depth show little impact.

Numerical investigation on heat transfer and pressure drop characteristics of moisture separator reheater with porous media method

The geometry structure of the Moisture separator reheater is very complex, which makes it almost impossible to calculate the whole domain and analyze the physical characteristics. To get the three-dimensional physical property distribution of the moisture separator reheaters, the porous media method is used to simplify the geometry. The 1-dimensional and 3-dimensional coupling theory is adopted into the calculation, for the primary side inside the finned tubes is iterated as the one-dimensional distribution, and the secondary side outside the finned tubes are treated as three dimensional. The whole process of conducting the porous media methods is illustrated with the value. Both the calculated and experimental results of the pressure drop are about 10 kPa in the 1st and 2nd reheaters. The calculation results provide a design and safety evaluation of the moisture separator reheater, as the three-dimensional physical distribution is got through the porous media calculation. With different input parameters such like the arrangement of the finned tubes, the calculated results of heat transfer and pressure drop will be different, and the calculated results are helpful to the design and optimization of the finned tube reheaters. This will help design a set of finned tube parameters.

Probabilistic model of torsion capacity of randomly corroded circular steel tube

The torsion capacity is one of the key parameters of circular steel tubes (CSTs). Corrosion can obviously decrease the torsion capacity of CSTs. The aim of this work is to quantify the influence of corrosion on the torsion capacity. The applicability of derived conclusion for CSTs with different D/t ratio is investigated. The random local corrosion which is most common in accrual condition is adopted. The geometrical imperfection on the torsion capacity of corroded CSTs is also revealed. The corroded thickness t c/t is assumed to follow different probabilistic distributions and then the influence of distribution model is analyzed. The changing rule of residual torsion capacity along with mass loss ratio is presented. The probabilistic distribution model of reduction factor of torsion capacity Θ followed normal distribution and the analytical method to determine the probabilistic distribution model is proposed and verified. The numerical case indicated that the analytical method can accurately predict the random model of Θ.

基于响应面法的谷子流体排种器搅拌技术参数优化

Fluid seeding is a new technology for drought resistance, water saving and yield increase in modern agriculture. To improve the uniformity of fluid seed metering of millet, the mechanical stirring device was added to the metering device, and the single-factor tests were carried out on the size parameters of the pump tube, the installation position and the parameters of mechanical stirring. The stirring speed, the ratio between the length of stirring paddle and the diameter of seed box and distance between the pump tube and the stirring paddle were selected as independent variables, and the right rate of hill distance, right rate of seeds per hill and rate of no seed hill were selected as response values. According to the test design principle of Central Composite Design, a response surface analysis method was used to establish mathematical models between each experimental factor and performance index, and the influencing factors of fluid seed metering were analyzed. The single-factor test results showed that when the pump tube was installed on the side of the seed box, and its inner diameter and wall thickness were 4.8 mm and 1.6 mm, respectively, the seeding performance was better. The response surface test results showed that the selected factors all have an influence on the performance of millet fluid seed metering, and the optimal stirring parameters were the stirring speed of 30 r/s, the ratio between the length of stirring paddle and the diameter of seed box of 0.69, and distance between the pump tube and the stirring paddle of 0.11 cm. The verification test was conducted under these parameters, and the right rate of hill distance, right rate of seeds per hill and rate of no seed hill were 94.14%, 84.24%, and 2.21%, respectively, and the error from the predicted values was less than 4%. The performance indexes of fluid seed metering were improved compared with the fluid seed metering device without stirring device, indicating that the optimized stirring parameters can improve the performance indexes of millet fluid seed metering. This study can provide a reference for the research and development of key technologies and equipment for precision fluid seed metering of millet.

Energy absorption of discretely assembled composite self-locked systems

Impact accidents cause great damage to lives and devices due to strong destructiveness and weak predictability, and accordingly, flexibility and modifiability are essential in the design of novel impact-resistant structures. To achieve this goal, two newly-designed energy absorption systems were proposed in this paper, which could be discretely assembled without boundary constraints. Quasi-static experiments and finite element method (FEM) simulations were carried out to reveal the deformation mechanism and test the usability, based on which the analytical solutions of the crushing force of the models were established adopting plastic hinge analysis and energy method. Parametric study of multiple-tube systems was conducted to reveal the effects of foam porosity and inner tube parameters on dynamic response, and the optimal design was summarized, achieving the energy absorption efficiency of 39%. The functionally graded design of composite self-locked (CSL) systems was explored, and it was proven that the system with positive stiffness gradient was optimal.

Performance Study of Origami Crash Tubes Based on Energy Dissipation History

Thin-walled tubes are widely used as energy-absorbing components in traffic vehicles, which can absorb part of the energy in time by using the plastic deformation of the components during collision so as to reduce the damage of the vehicle body and improve the overall safety and reliability of traffic vehicles. The prefolded design of thin-walled tube components can guide it to achieve the ideal energy dissipation performance according to the preset damage path, so the related research based on origami tubes has attracted a lot of attention. Since the geometry of the origami tubes is controlled by many parameters and stress and deformation is a complex nonlinear damage process, most of the previous studies adopted the method of case analysis to carry out numerical simulation and experimental verification of the relevant influence parameters. This paper makes a new exploration of this kind of problem and focuses on solving the related technical problems in three aspects: 1. The automatic model modeling and 3D display based on parameters are proposed; 2. System integration using Python programming to automatically generate the data files of ABAQUS for finite element simulation was realized, and we sorted the finite element analysis results into an artificial intelligence analysis data set; 3. Clustering analysis of the energy consumption history of the data set is carried out using a machine learning algorithm, and the key design parameters that affect the energy consumption history are studied in depth. The sensitivity of the energy absorption performance of the origami tubes with multi-morphology patterns to the crease spacing is studied, and it is shown that the concave–convex crease spacing distribution with a distance larger than 18 mm could be used to activate specific crushing modes. In the optimal case, its initial peak force is reduced by 66.6% compared to uniformly spaced creases, while the average crushing force is essentially the same. Furthermore, this paper finds a new path to optimizing the design of parameters for origami tubes including a multi-morphology origami pattern from the perspective of energy dissipation.

Experimental and Numerical Analysis on the Impact Wear Behavior of TP316H Steel.

In this work, the contact force model and experiment methods were used to study the dynamic response and impact wear behavior of TP316H steel. The Flore model and the classic Hertz model were selected for comparison with the experimental results, and the model was revised according to the section parameters of the TP316H tube. The results show that there is a large difference between the models without considering the effect of structural stiffness on the impact system and the test results, whereas the revised model has a good agreement. With the rise in impact mass, the coefficient of restitution increases from 0.65 to 0.78, whereas the energy dissipation and wear volume decrease. Spalling, delamination, plastic deformation, and oxidative wear are the main impact wear mechanism of TP316H steel.

An Overview on Bipolar Junction Transistor as a Sensor for X-ray Beams Used in Medical Diagnosis.

Although not manufactured to be used under X-ray photons, the commercial bipolar junction transistor (BJT) is an electronic device that can be used as an ionizing radiation sensor. In this article an overview on the BJT and its principle of operation were made for the purpose of better understanding how such a semiconductor device behaves when under diagnostic X-ray beam. Therefore, it addresses some topics such as the structure of the device, the bias configuration when operating in active mode, and so on. Even knowing that the most complete theory to describe the “transistor effect” is based on quantum theory (the energy band theory of solids), here it is preferable to take a simpler experimental approach to clearly understand the operation of the BJT. In electronics, the BJT is used as a current amplifier, and depending on the bias and point of view it also becomes a voltage amplifier. In the analysis of BJT under an X-ray beam, in addition to its operation as a sensor to measure the dose or some diagnostic X-ray tube parameter, it has also led to technological innovation in the technique of digital data storage based on the effect of radiation.

Tetracycline (TC) degradation via hydrodynamic cavitation (HC) combined Fenton's reagent: Optimizing geometric and operation parameters

In this study, the tetracycline degradation was conducted by using hydrodynamic cavitation (HC) device. The influences of Venturi tube parameters (divergence angle, throat length and convergent angle) and the operation conditions (inlet pressure (1.0-5.0 bar), initial tetracycline concentration (5.0-20 mg/L) and addition of some common inorganic anions) on tetracycline degradation were investigated. The results showed that a strong HC effect can be obtained when the Venturi tube with 22° half convergent angle, 2.0 mm throat length and 6.0° half divergence angle is used. The tetracycline degradation ratio can reach 83.17% when inlet pressure and initial concentration were 3.0 bar and 5.0 mg/L, respectively. The tetracycline HC degradation can be intensified by CO32− but inhibited by NO3− and SO42−. Liquid Chromatography-Mass Spectrometry result shows that tetracycline can be decomposed into small molecules in HC process. Total organic carbon reduction testifies that tetracycline can be effectively mineralized into H2O, CO2 and inorganic ions. The addition of Fenton's reagent can further enhance the tetracycline HC degradation efficiency. It is speculated that HC technology assisted by Fenton's reagent can be used for large-scale treatment of antibiotic wastewater.

Influence of the Venturi Tube Geometry on Fine Bubble Generation

Venturi tube fine bubble generator has been focused in the recent studies due to its simple structure, high generation efficiency and low power consumption. The generated fine bubbles with the properties such as cleaning, sterilization, disinfection, and deodorization, have been applied in many fields including the environment, agriculture, food, medical fields, etc. In this work, an oral irrigator utilizing fine bubble technology for oral purification is developed. The venturi tube is embedded in irrigator for fine bubble generation. We design venturi tubes with different geometrical combinations to improve the performance of fine bubble generation including bubble size and volume by experiment and numerical simulation. In the experiment, the flow states in the nozzle are photographed with a high-speed camera, and the area ratios of the bubbles in the tank are calculated to analyze the production volume of the bubbles. In numerical simulation, the models with the same geometrical parameters are made and Ansys Fluent is used to implement 3D CFD simulation to analyze the internal flow state and evaluate the generation performance. Both the experimental results and simulation results show that the generation performance is dependent on the geometrical parameters of venturi tube, and the venturi tubes with divergent angle of 1.2°, divergent length of 40 mm, and the one with divergent angle of 5°, divergent length of 20 mm demonstrate the best performance compared with others.

Dynamics of morphometric parameters of the structures intestinal tube of the middle part of the human digestive tract in the embryonic period

Dynamics of morphometric parameters of the structures intestinal tube of the middle part of the human digestive tract in the embryonic period

A MOSFET-Based Method for Measuring Peak Kilovoltage (kVp) in Diagnostic X-Ray Beams

Peak kilovoltage (kVp) is an X-ray tube parameter that can influence the radiograph image quality and therefore, if the kVp is different from the nominal value, it can provide an unnecessary radiation dose to the patient if the examination has to be repeated. Therefore, some radiation protection institutions and health organizations (ICRP, IAEA) make recommendations to monitor kVp in medical diagnostic X-ray equipment in clinics and hospitals. There are some methods for measuring kVp in diagnostic X-ray beams, and the most common is the well-known two-sensor method, which uses two filters to attenuate the radiation beam, and it is based on the measurement of each identical sensor. The purpose of this article is to present a method for non-invasive measurement of kVp in medical diagnostic X-ray beams using the MOSFET device. Actually, MOSFET is well known as a detector for ionizing radiation dosimetry mainly in radiotherapy beams. Recently, MOSFET has also been used as dosimeter in diagnostic X-ray beams. In this work it will be shown a kVp measurement technique with MOSFET, which does not use the attenuation factor of the radiation filters, but instead takes advantage of the effect of the device package itself, known as the buildup cap effect. The results show that even with damage to the device exposed to radiation, MOSFET can be used as sensor for kVp measurement.

Burst characteristics of advanced accident-tolerant FeCrAl cladding under temperature transient testing

Assessment of burst characteristics of accident-tolerant fuel (ATF) claddings is essential to evaluate the safety margins of nuclear reactors, and better understanding can enable accelerated licensing for reactor concepts that include the new materials. Therefore, this study investigated the burst behavior of an ATF candidate of C26M, which is an iron–chromium–aluminum alloy (FeCrAl) under transient testing like the simulated loss-of-coolant accident (LOCA) conditions, except the water-quenching phase, in light-water reactors (LWRs).The effect of LOCA specimen length was assessed in terms of post-burst tube parameters. No critical length effect was determined on the burst pressure, burst location, and burst size measurements. Burst temperature showed larger variation likely due to its measurement approach used in this study. The post-test diametral strain was identified as the critical parameter to reduce the specimen length as compared to tube burst length or width. Postmortem optical metrology and digital image correlation were employed to determine the local strain-state during the simulated LOCA, which showed the loading path was close to equibiaxial conditions in regions away from the burst location, rather than internally pressurized conditions (or “plane-strain” tension).Pst-test microstructural characterizations of the FeCrAl revealed that ductile damage was present at the edge of the outer radial surface while the rest of the material was ruptured via cleavage at LOCA burst temperatures. Furthermore, internal grain boundary cracks were observed at locations away from the tube burst region. This behavior was considered to occur during the cooling down period of the simulated LOCA test. Overall, this study aimed to provide essential data for fuel performance code development by considering micromechanics of the deformation and failure.

Revisit the Pitot static tubes in the standards

A Pitot tube is a popular device used for the measurements of flow fields. To control the accuracy of the Pitot tube coefficient, the international standard organization (ISO), the American Society for Testing and Materials (ASTM), and the Japanese Industrial Standards (JIS) issued guidelines that recommended the shape and working conditions of these devices. However, many Pitot tubes on the market do not follow these guidelines. In the present study, various types of Pitot tubes in the market were tested at the National Metrology Institute of Japan (NMIJ) to determine the effects of the geometry and flow characteristics. The results revealed certain limitations in the existing ISO and JIS standards, specifically with regard to the recommended design parameters of the AMCA Pitot tube, the reference coefficient value for the JIS Pitot tube, and the redefinition and limitation of Reynolds numbers pertaining to Pitot tube working conditions.

Process parameter optimization for thin-walled tube push-bending using response surface methodology

In this paper, the response surface methodology (RSM) and finite element (FE) simulation were applied to optimize the push-bending process parameters of the thin-walled tube with polyurethane mandrel. The objective of the present work is to predict the optimal set of process parameters including the length to diameter ratio of the mandrel (L/D), the friction coefficient between die and tube ( $${\mu }_{1}$$ ), the friction coefficient between polyurethane and tube ( $${\mu }_{2}$$ ), and Poisson’s ratio of polyurethane ( $$\upsilon$$ ) to obtain qualified bent tubes. Three empirical models were developed to describe the relationship between process parameters and quality parameters of the bent tubes. In addition, the significant factors affecting the forming quality were analyzed using analysis of variance (ANOVA) of each model. Response surfaces were constructed to study the effect of each process parameter on the quality of the bent tubes. Finally, the process optimization window with the maximum thinning rate ( $$\varphi$$ ) less than 20%, the maximum thickening rate ( $$\psi$$ ) less than 17%, and the maximum cross-section ovality ( $$\xi$$ ) less than 5% of the bent tube was established. Qualified bent tubes with diameter of 144 mm, wall thickness of 2 mm, and bending radius of 280 mm were formed experimentally by following the established process window.

Influence of HIV infection and alcohol abuse on the morphological structure of the uterine tube

Chronic alcoholism and HIV infection inevitably worsen the prognosis of the course of any pathology. The aim of our work was to determine the influence of HIV infection and alcohol abuse on the morphological structure of fallopian tubes. To achieve the goal, sectional material was selected from 50 women, who were divided into two groups. The first (main) group included 25 women who were HIV-infected and abused alcohol. The control group consisted of sectional material of 25 women without HIV infection and alcohol addiction. As a result of the study, it was determined that the presence of chronic alcoholism in HIV-infected women significantly affects both the morphometric parameters of the fallopian tube and its histological structure. Significant pathological changes are determined in each of the studied indicators. It was found that in the main group compared to the control group, the length of the ampullary section decreases (from [79.47±0.51]×10-3 m to [69.91±0.78]×10-3 m), the outer diameter in the area of the transition of the isthmus to the ampullary department (from [6.81±0.23]×10-3 m to [5.66±0.38]×10-3 m), the area of the lumen of the ampullary department decreases (from [9.44±0.44]×10-6 m2 to [7.66±0.55]×10-6 m2); the height of the epithelial layer, measured histologically, is also reduced (from [92.01±4.03]×10-6 m to [65.41±3.20]×10-6 m); the volume of connective tissue in the muscle layer, on the contrary, increased (from [5.61±1.01]% to [17.39±3.81]%). It was concluded that the combination of chronic alcoholism and HIV infection in women can to cause sharply pronounced irreversible changes in both the macro- and microscopic structure of the organ under study. Keywords: HIV infection, chronic alcoholism, fallopian tube.

Energy Absorption Characteristics of a CFRP-Al Hybrid Thin-Walled Circular Tube under Axial Crushing

Thin-walled tubes have gained wide applications in aerospace, automobile and other engineering fields due to their excellent energy absorption and lightweight properties. In this study, a novel method of entropy-weighted TOPSIS was adopted to study the energy absorption characteristics of a thin-walled circular tube under axial crushing. Three types of thin-walled circular tubes, namely, aluminum (Al) tubes, carbon-fiber-reinforced plastics (CFRP) tubes and CFRP-Al hybrid thin-walled tubes, were fabricated. Quasi-static axial crushing tests were then carried out for these specimens, and their failure modes and energy absorption performance were analyzed. The CFRP material parameters were obtained through tensile, compression and in-plane shear tests of CFRP laminates. The finite element models for the quasi-static axial crushing of these three types of circular tubes were established. The accuracy of the finite element models was verified by comparing the simulation results with the test results. On this basis, the effects of the geometric dimension and ply parameters of a CFRP-Al hybrid thin-walled circular tube on the axial crushing energy absorption characteristics were studied based on an orthogonal design and entropy-weighted TOPSIS method. The results showed that Al tube thickness, CFRP ply thickness and orientation have great effect on the energy absorption performance of a CFRP-Al hybrid thin-walled circular tube, whereas the tube diameter and length have little effect. The energy absorption capability of a CFRP-Al hybrid tube can be improved by increasing the thickness of the Al tube and the CFRP tube as well as the number of ±45° plies.

R410A flow condensation inside two dimensional micro-fin tubes and three dimensional dimple tubes

Condensation heat transfer characteristics were experimentally investigated inside two dimensional helix micro fin (HX) tubes, three-dimensional dimple (1EHT) tubes and smooth (ST) tubes; while using R410A, for a variety of operating conditions and tube parameters. Tubes evaluated had a length of 2 m, with outer diameters of 9.52 and 12.7 mm; tube materials included copper and stainless steel. Experimental procedure was verified using a single-phase heat balance; with a comparison of results (enhanced tubes to smooth tube) being performed. The condensation experiments were performed at a saturated temperature of 35–45 °C; for the vapor quality range from 0.1 to 0.9; with mass fluxes that ranged from 70 to 450 kg m−2 s−1. Additionally, the effect of various parameters (mass flux, mean vapor quality, saturation temperature, tube thermal conductivity, tube diameter, and surface structure) on the tube side condensation heat transfer was evaluated.For the test conditions considered here the HTC enhancement ratio is in the range from 1.15 to 2.05 for the 1EHT tube and for the HX tube it ranged from 1.18 to 1.69; while the performance factor (PF takes into account the pressure drop) is 1.02–1.57 (1EHT) and 1.23–1.78 (HX). Heat transfer performance of the smooth tube was determined to be slightly affected by the thermal conductivity of the tube; however, for enhanced tubes there is a more dramatic increase in the HTC for an increase of thermal conductivity. Additionally, better heat transfer performance is demonstrated for smaller diameter tubes. Finally, the enhancement effect of the experimental parameters on the enhanced tubes was quantified through the use of a newly introduced evaluation factor.

Research on the Tensile Mechanical Properties of a Braided Corrugated Hose and Its Axial Stiffness Model

Braided corrugated hoses are widely used in displacement compensation and vibration absorption environments due to their excellent flexibility and energy dissipation properties; however, the axial stiffness has rarely been discussed before as an important physical property of braided corrugated hoses. In this paper, the theoretical axial stiffness model for braided corrugated hoses is established based on the energy method and the theory of the curved beam. The influences of the braiding parameters of the metallic braided tube and the structural parameters of the bellows on the axial stiffness are also discussed. Through finite element tensile testing, the axial stiffness curves of the braided corrugated hose under different braiding angles and different wire diameters are obtained. The theoretical axial stiffness model is in good agreement with the simulation experiment, which reflects the nonlinear effects of the braiding angle and wire diameter on the braided corrugated hose. This paper provides an accurate method and basis for the design of braided corrugated hoses in the future.

Experimental and numerical modal analysis of wall tubes in the coal‐fired boiler or radiant syngas cooler

AbstractThe slag deposited on the wall tubes in the coal‐fired boiler or radiant syngas cooler (RSC) of the entrained flow gasifier could reduce the heat transfer efficiency and degrade the tubes by corrosion. During the operation of the boiler or RSC, the rapping‐off‐ash method is an effective method to remove slag deposits, especially in a high‐pressure environment. The operating parameters of the rapping‐off‐ash method are related to the modal parameters of wall tubes, including the natural frequency, damping ratio, and mode shapes. In this study, modal parameters of wall tubes composed of three single tubes and fins were experimentally determined through the modal test analysis under both empty and water‐filled conditions. The dynamic characteristics of wall tubes were extracted by using the roving hammer‐impact test and the frequency response function (FRF). A numerical simulation based on the finite element method in ABAQUS was conducted to compare with the experimental modal analysis. The first five natural modes ranged from 14 to 154 Hz, and the maximum vibration or torsion locations of wall tubes under the corresponding mode frequencies were investigated. The water inside the wall tubes could reduce the stiffness of the structure and decrease the values of natural frequency.