The research of pipeline lifting model in horizontal directional drilling

In recent years, Horizontal Directional Drilling has been the first choice in trenchless engineering of pipeline crossing for its strong environmental adaptability, high efficiency and low cost. In order to reduce the resistance force and avoid pipeline damage in construction, the angle formed by the pipeline axis and hole axis should be lessened when the pipeline is lifted to a height. However, the stress status of the pipeline is very complex during the lifting process. Hence the research of pipeline lifting process is great importance for pipeline safety. In this paper, a finite element model is established to uncover the stress variety law of pipeline during lifting process. And then its reliability was verified by the experimental method. At last, the results of engineering experiment show that the finite element model which is credible can be used to reveal the stress variety law of the pipeline during the lifting process

A family of dual-anion-based sodium superionic conductors for all-solid-state sodium-ion batteries

The sodium (Na) superionic conductor is a key component that could revolutionize the energy density and safety of conventional Na-ion batteries. However, existing Na superionic conductors are primarily based on a single-anion framework, each presenting inherent advantages and disadvantages. Here we introduce a family of amorphous Na-ion conductors (Na2O2-MCly, M = Hf, Zr and Ta) based on the dual-anion framework of oxychloride. Benefiting from a dual-anion chemistry and with the resulting distinctive structures, Na2O2-MCly electrolytes exhibit room-temperature ionic conductivities up to 2.0 mS cm-1, wide electrochemical stability windows and desirable mechanical properties. All-solid-state Na-ion batteries incorporating amorphous Na2O2-HfCl4 electrolyte and a Na0.85Mn0.5Ni0.4Fe0.1O2 cathode exhibit a superior rate capability and long-term cycle stability, with 78% capacity retention after 700 cycles under 0.2 C (1C = 120 mA g-1) at room temperature. The discoveries in this work could trigger a new wave of enthusiasm for exploring new superionic conductors beyond those based on a single-anion framework

Investigation of the Jet Characteristics and Pulse Mechanism of Self-Excited Oscillating Pulsed Jet Nozzle

Self-excited oscillation pulse jet technology is widely used to clean sediment from oil storage tanks. Its successful application is dependent on jet performance. As the cleaning requirements of the oil industry increase, it is necessary to optimise the structure of self-excited oscillation pulsed jet nozzles (SOPJNs) to optimise cleaning and energy efficiencies. In this study, the jet performance of a SOPJN is modelled and analysed based on computational fluid dynamics with consideration of a large eddy simulation and homogeneous cavitation. The modelling results are highly consistent with experimental results. The effects of the SOPJN’s inlet diameter, cavity diameter, cavity length, wall reflection angle, and inlet pressure on the jet’s peak velocity, oscillation frequency, and cavitation number were analysed. The results show that the oscillation frequency decreases with the increase of the inlet diameter d1, cavity diameter D, cavity length L and reflection angle of wall α. Optimisation of the SOPJN inlet diameter, cavity length, and wall reflection angle produced a jet with a high peak velocity and strong cavitation. The optimal nozzle cavity diameter strengthens cavitation, while the peak velocity fluctuates as the cavity diameter increases. The peak velocity increases with the inlet pressure, while the increasing rate of the peak velocity decreases. The results of this study can be used in the design and optimisation of similar nozzle structures for improved pulse jet cleaning.</jats:p

Investigation of the Jet Characteristics and Pulse Mechanism of Self-Excited Oscillating Pulsed Jet Nozzle

Self-excited oscillation pulse jet technology is widely used to clean sediment from oil storage tanks. Its successful application is dependent on jet performance. As the cleaning requirements of the oil industry increase, it is necessary to optimise the structure of self-excited oscillation pulsed jet nozzles (SOPJNs) to optimise cleaning and energy efficiencies. In this study, the jet performance of a SOPJN is modelled and analysed based on computational fluid dynamics with consideration of a large eddy simulation and homogeneous cavitation. The modelling results are highly consistent with experimental results. The effects of the SOPJN’s inlet diameter, cavity diameter, cavity length, wall reflection angle, and inlet pressure on the jet’s peak velocity, oscillation frequency, and cavitation number were analysed. The results show that the oscillation frequency decreases with the increase of the inlet diameter d1, cavity diameter D, cavity length L and reflection angle of wall α. Optimisation of the SOPJN inlet diameter, cavity length, and wall reflection angle produced a jet with a high peak velocity and strong cavitation. The optimal nozzle cavity diameter strengthens cavitation, while the peak velocity fluctuates as the cavity diameter increases. The peak velocity increases with the inlet pressure, while the increasing rate of the peak velocity decreases. The results of this study can be used in the design and optimisation of similar nozzle structures for improved pulse jet cleaning

Phase transformation and flow simulation of weld pools at the crack tips of elbows under pulsed current

ObjectiveIn the base metal repair for elbows using pulsed currents, detour flow typically occurs at the crack tips, resulting in the formation of weld pools due to local temperature increases. The size, flow, and solidification behaviors of these weld pools, have a decisive effect on crack healing. Exploring the evolution patterns of weld pools near elbow cracks under the influence of pulsed currents, along with a further investigation into the healing mechanisms of crack tips and fronts, holds significant importance for the technological advancement of pipe crack repair utilizing pulsed currents. MethodsA finite element model for repairing 90° high-pressure elbows with cracks using pulsed currents was established, based on Comsol software, focusing on NiCr21Mo high-pressure elbows with cracks. This model incorporated a multi-physical field coupling approach that combines “two-phase flow and phase field” within an “electrical-thermal-structural” three-field coupling framework. This integration allows for the simulation of phase transformation and the flow of weld pools. Further analysis explored the evolution patterns of weld pools near cracks in elbows during pulsed current discharge, as well as the phase transformation patterns and flow characteristics of the liquid-phase metal after halting the discharge. ResultsBoth the duration and interval of pulse discharge were identified to be influential to the formation of molten pools associated with cracks.With a pulsed current density set at 2.4×108 A/m2, weld pools formed at the crack tips and fronts in U-shaped columns following current discharge exceeding 0.65 seconds. Beginning at 0.75 seconds of discharge, the melting effect extended from the regions around the cracks into the surrounding areas, and partial evaporation of the liquid-phase metal occurred, both of which are detrimental to crack healing. After the discharge was halted, the metal flow of the weld pools gradually slowed down, with crack healing efficiency peaking within the first 0.001 seconds, followed by complete solidification within 0.008 seconds. Consequently, a pulse interval greater than 0.008 seconds was identified as optimal to prevent adverse effects on the weld pool area during subsequent pulses, thereby enhancing repair performance. ConclusionThe application of pulsed currents results in the formation of U-shaped columnar weld pools at the crack tip, with an increasing volume of liquid-phase material near the cracks as discharge time progresses. To maximize repair effectiveness, it is essential to select an appropriate discharge duration that allows for sufficient phase transformation at the crack tips and fronts, resulting in the formation of weld pools while avoiding solid-liquid phase transitions in surrounding areas. Additionally, the pulse discharge interval should be longer than the solidification time of the liquid metal in the weld pools. Otherwise, repair efficiency may decrease due to smaller weld pool sizes. It is advisable to determine the pulse discharge power, duration, and interval through simulations prior to repairing microcracks in high-pressure elbows using pulsed currents, thereby improving both the accuracy and efficiency of actual elbow crack repairs

THE MECHANICAL ANALYSIS OF PIPELINE LIFTING DURING THE HORIZONTAL DIRECTIONAL CROSSING

If the hoisting position is bad during the engineering application of the lifting pipe,which may bring the serious influence when the pipe smoothly enters the grave,even happen stuck pipe and tube flat accidents. Through the mechanical analysis of the pipe lifting,themathematical model about lifting point position and the grave angle was established,which on the basis of reasonable assumptions. The location of the lifting point 2 affects on the size of the grave angle more than lifting point 1by mathematical model analysis. And then compared with the calculated value of mathematical model and the value of test measurement,the relative error of theoretical calculation value and experimental value that is about 5. 8% was discovered.Therefore,the mathematical model can be used to guide the actual construction

Force Analysis on Coiled Tubing Plug Drilling Operation in Ultra-Deep Well with Long Horizontal Section

For purpose of accurate landing depth prediction and process safety assessment of coiled tubing （CT） plug drilling operation， considering the factors such as wellbore trajectory， buoyant weight of CT， friction of pipe sleeve， CT buckling and boundary conditions of bottomhole assembly （BHA）， based on the soft rope model， a mechanical model of CT operations was constructed by incorporating variable friction factor and CT with variable wall thickness， and taking into account the influence of well fluid drag force. Moreover， the estimates of different models were compared using the actual data from an ultra-deep well S9P1H. The results show that the well fluid drag force leads to enhanced load on CT， while the variable friction factor is conducive to the decreased load on CT， and the variable wall thickness helps reduce the stress on CT and relieve the fatigue of CT， prolonging its service life. The use of CT of 60.3 mm in diameter enables drilling to the bottomhole even at the weight on bit （WOB） of 20 kN and 25 kN， suggesting that the mechanical model incorporating variable friction factor and variable stiffness maximizes the plug drilling capability within the safe range. The research results provide guidance for addressing insufficient extension of CT in plug drilling operation in ultra-deep wells

Calculation and comparison on fracture toughness of specific reliability between ASTM and ISO standards

Abstract Fracture toughness, as a crucial mechanical property, is essential in the research of fatigue crack propagation and fatigue life. Considering the enormous data scatter of the fracture toughness in experiments, a data processing method is proposed to calculate the fracture toughness for the specified reliability. Based on the traditional data processing method shown in the relative standards, the two-dimensional, one-sided tolerance factor is introduced to calculate the influence of the reliability. In addition, by comparing the data processing methods of the fracture toughness presented in the ISO12135:2016 and ASTM E1820-2013 standards, the differences between them were mainly the range of the qualified data, the function of the construction line, and the equation of the regression line. Because the construction lines of the two standards are based on two different material constitutive models, if the constitutive model of material is more aligned with that of the ideal elastic plastic material, the ASTM E1820-2013 standard is recommended; otherwise, the ISO12135:2016 standard is recommended. For 30CrNi2MoVA, the ISO 12135:2016 standard was more suitable, and the error of the JIC obtained by the two standards was about 5%.</jats:p