A liquid loading prediction method of gas pipeline based on machine learning

The liquid loading is one of the most frequently encountered phenomena in the transportation of gas pipeline,reducing the transmission efficiency and threatening the flow assurance.However,most of the traditional mechanism models are semi-empirical models,and have to be resolved under different working conditions with complex calculation process.The development of big data technology and artificial intelligence provides the possibility to establish data-driven models.This paper aims to establish a liquid loading prediction model for natural gas pipeline with high generalization ability based on machine learning.First,according to the characteristics of actual gas pipeline,a variety of reasonable combinations of working conditions such as different gas velocity,pipe diameters,water contents and outlet pressures were set,and multiple undulating pipeline topography with different elevation differences was established.Then a large number of simulations were performed by simulator OLGA to obtain the data required for machine learning.After data preprocessing,six supervised learning algorithms,including support vector machine(SVM),decision tree(DT),random forest(RF),artificial neural network(ANN),plain Bayesian classification(NBC),and K nearest neighbor algorithm(KNN),were compared to evaluate the performance of liquid loading prediction.Finally,the RF and KNN with better performance were selected for parameter tuning and then used to the actual pipeline for liquid loading location prediction.Compared with OLGA simulation,the established data-driven model not only improves calculation efficiency and reduces workload,but also can provide technical support for gas pipeline flow assurance.

On the Development of a Model for the Prediction of Liquid Loading in Gas Wells with an Inclined Section

The ability to predict liquid loading in horizontal gas wells is of great importance for determining the time of drainage and optimizing the related production technology.In the present work,we describe the outcomes of experiments conducted using air-water mixtures in a horizontal well.The results show that the configuration with an inclined section is the most susceptible to liquid loading.Laboratory experiments in an inclined pipe were also conducted to analyze the variation of the critical gas flow rate under different angles,pressure and liquid volume(taking the equal liquid volume at inlet and outlet as the criterion for judging on the critical state).According to these results,the related angle of the inclined section ranges from 45°to 60°.Finally,a modified approach based on the Belfroid model has been used to predict the critical gas flow rate for the inclined section.After comparison with field data,this modified model shows an accuracy of 96%,indicating that it has better performances with respect to other models used in the past to predict liquid loading.

Mode selection of Lamb waves for the evaluation of solid plates with liquid loading

This paper studies the mode selection of Lamb waves for evaluating solid plates with liquid loading. For this purpose, the Lamb wave selected should have the features such as zero normal displacement components at the plate surface in contact with liquid, small dispersion, and maximum group velocity. It is found that when the phase velocity of Lamb wave is equal to the longitudinal wave velocity of the plate material, its normal displacement at the plate surface is always zero. Through the numerical analyses, the specific S2 Lamb wave that has zero normal displacement component at the plate surface, small dispersion and maximum group velocity compared with the other Lamb waves has been found. With respect to the specific S2 Lamb wave, some experimental examinations have been carried out. It is found that the liquid loading on the plate surface has less influence on the specific S2 Lamb wave signal but it can effectively eliminate the other signals. Moreover, the specific S2 Lamb wave selected exhibits the capability of detecting multiple defects in the solid plate with the liquid loading. It can be concluded that the specific S2 Lamb wave selected is suitable for the evaluation of solid plates with liquid loading.

Research and Development of Gadolinium Loaded Liquid Scintillator for Daya Bay Neutrino Experiment

Daya Bay reactor anti-neutrino experiment is designed to measure an important parameter, θ13, of neutrino by using anti-neutrino created by Daya Bay and Ling Ao nuclear power plants. The experiment need 200 tonnes gadolinium loaded liquid scintillator (Gd-LS) as target. The purpose of this research is to develop suitable Gd-LS candidates for this experiment, which should have long attenuation length, high light yield, long term stability, and should be compatible with the material used to build the containers. Two kinds of Gd-LS were developed using carboxylic acids 2-ethylhexanoic acid (EHA) and 3, 5, 5-trimethylhexanoic acid (TMHA) as complexing ligands and mesitylene and linear alkyl benzene (LAB) as scintillator solvents. Four Gd-LS samples with different Gd content and complexing ligands were prepared and characterized. The relative light yields and the stabilities of all samples are satisfying, and the values of attenuation length show that TMHA is a better ligand than EHA.

A novel 4π Gd-loaded liquid scintillator detection system

With a Geant4 software package based on the Monte Carlo method, a multi-cell 4π detection system is designed, which consists of 40 Gadolinium-loaded liquid scintillation detectors. These detectors, associated with a fission chamber in its geometrical center, constitute a platform. This platform is mainly used for the measurement of a fissionable nucleus(n, 2n) reaction cross section. In order to properly determine the experimental set-up, we carry out a systematic numerical simulation using our model which is established by the Geant4 software package. This work provides rich and valuable reference data for experiments on the fissionable nucleus(n, 2n) cross section measurement in the future.

Study on the Optimization of Agaricus bisporus Liquid Spawn Production Process

On the basis of single-factor experiment, an orthogonal experiment was carried out with culture temperature, initial pH, inoculation amount and liquid loading volume as factors at three levels. With the mycelium biomass as an index, the optimal secondary liquid seed culture conditions were obtained： culture temperature 27 ℃, initial pH 6.5, inoculation amount 13%, liquid loading volume 100 ml. Under the optimized conditions, mycelium biomass reached the maximum.

A new model for predicting the critical liquid-carrying velocity in inclined gas wells

Based on the assumption of gas-liquid stratified flow pattern in inclined gas wells,considering the influence of wettability and surface tension on the circumferential distribution of liquid film along the wellbore wall,the influence of the change of the gas-liquid interface configuration on the potential energy,kinetic energy and surface free energy of the two-phase system per unit length of the tube is investigated,and a new model for calculating the gas-liquid distribution at critical conditions is developed by using the principle of minimum energy.Considering the influence of the inclination angle,the calculation model of interfacial friction factor is established,and finally closed the governing equations.The interface shape is more vulnerable to wettability and surface tension at a low liquid holdup,resulting in a curved interface configuration.The interface is more curved when the smaller is the pipe diameter,or the smaller the liquid holdup,or the smaller the deviation angle,or the greater gas velocity,or the greater the gas density.The critical liquid-carrying velocity increases nonlinearly and then decreases with the increase of inclination angle.The inclination corresponding to the maximum critical liquid-carrying velocity increases with the increase of the diameter of the wellbore,and it is also affected by the fluid properties of the gas phase and liquid phase.The mean relative errors for critical liquid-carrying velocity and critical pressure gradient are 1.19%and 3.02%,respectively,and the misclassification rate is 2.38%in the field trial,implying the new model can provide a valid judgement on the liquid loading in inclined gas wells.

Contribution of tuned liquid column gas dampers to the performance of offshore wind turbines under wind, wave, and seismic excitations

The main intention of the present study is to reduce wind, wave, and seismic induced vibrations of jacket- type offshore wind turbines （JOWTs） through a newly developed vibration absorber, called tuned liquid column gas damper （TLCGD）. Using a Simulink-based model, an analytical model is developed to simulate global behavior of JOWTs under different dynamic excitations. The study is followed by a parametric study to explore efficiency of the TLCGD in terms of nacelle acceleration reduction under wind, wave, and earthquake loads. Study results indicate that optimum frequency of the TLCGD is rather insensitive to excitation type. In addition, while the gain in vibration control from TLCGDs with higher mass ratios is generally more pronounced, heavy TLCGDs are more sensitive to their tuned frequency such that ill-regulated TLCGD with high mass ratio can lead to destructive results. It is revealed that a well regulated TLCGD has noticeable contribution to the dynamic response of the JOWT under any excitation.

Influence of Particles on the Loading Capacity and the Temperature Rise of Water Film in Ultra-high Speed Hybrid Bearing

Ultra-high speed machining technology enables high efficiency, high precision and high integrity of machined surface. Previous researches of hybrid bearing rarely consider influences of solid particles in lubricant and ultra-high speed of hybrid bearing, which cannot be ignored under the high speed and micro-space conditions of ultra-high speed water-lubricated hybrid bearing. Considering the impact of solid particles in lubricant, turbulence and temperature viscosity effects of lubricant, the influences of particles on pressure distribution, loading capacity and the temperature rise of the lubricant film with four-step-cavity ultra-high speed water-lubricated hybrid bearing are presented in the paper. The results show that loading capacity of the hybrid bearing can be affected by changing the viscosity of the lubricant, and large particles can improve the bearing loading capacity higher. The impact of water film temperature rise produced by solid particles in lubricant is related with particle diameter and minimum film thickness. Compared with the soft particles, hard particles cause the more increasing of water film temperature rise and loading capacity. When the speed of hybrid bearing increases, the impact of solid particles on hybrid bearing becomes increasingly apparent, especially for ultra-high speed water-lubricated hybrid bearing. This research presents influences of solid particles on the loading capacity and the temperature rise of water film in ultra-high speed hybrid bearings, the research conclusions provide a new method to evaluate the influence of solid particles in lubricant of ultra-high speed water-lubricated hybrid bearing, which is important to performance calculation of ultra-high speed hybrid bearings, design of filtration system, and safe operation of ultra-high speed hybrid bearings.

柱塞气举排水采气研究现状及展望

气井积液是大部分天然气井在开发中后期存在的主要问题,排水采气工艺是排出井底积液并恢复和提高气井产量的关键技术之一。柱塞气举是一种可以高效排出井底积液的间歇生产工艺,该工艺具有结构简单、成本低等优点,适用于低产井和高气液比井,是目前我国最主要的排水采气技术之一。为此,系统地从柱塞类型及应用场景、柱塞气举速度模型、工作制度优化及故障诊断、新型柱塞气举工艺4个方面进行研究综述,分析了不同模型的优缺点,并总结了8种新型柱塞的特点和应用场景,进而针对目前气井生产效率低和井底积液难排出的情况,展望了柱塞气举工艺的技术发展方向。研究结果表明:(1)相比于国外,中国柱塞气举工艺应用广泛,发展较为成熟,新型柱塞气举工艺的发展进一步扩大了其应用范围。(2)速度模型可精确模拟柱塞在井筒中的运动状态;工作制度优化逐步向智能化发展。(3)目前仍存在柱塞气举工艺智能化程度低和无法适应复杂油气井生产的问题。结论认为,柱塞气举工艺下一步发展应聚焦4个方向:智能化技术的应用、适应复杂井条件下的技术开发、结合其他采气工艺的复合应用、基于气藏—井筒—地面一体化的井群制度优化。该研究成果对进一步推动国内柱塞气举相关研究与应用,具有较好的参考作用,并可以为柱塞气举未来发展方向提供指导。

一种新的水平气井临界携液气流速预测模型

气井中积液现象为井筒中液体的回流和聚集,是气井中严重的生产问题之一,会导致产量降低,甚至造成停产。气井积液预测能力对于保证气井正产生产和优化相关生产工艺具有重要意义。为了及时采取适当的对策防止积液现象的发生,准确预测和识别积液点至关重要。使用空气-水混合物在管径为60 mm的管道中进行了压力为0.2 MPa和0.5 MPa时0~90°倾角的室内实验,分析了在不同角度、压力和液体流量下临界气体流量的变化,随着角度的增大,临界气量先增大后减小,倾斜段是最难携液的井段,且55°倾角是最难携液的角度。在液膜受力分析的基础上,考虑到倾斜气井井壁的液膜分布不均匀,采用SHEKHAR的最大液膜厚度分布关系式进行计算,考虑到气芯中液滴载荷和液膜夹带的平衡,建立了一种新的水平气井临界携液气流速预测模型。利用实验数据和现场数据将新模型与LUO模型、BARNEA模型和LIU模型进行比较,新模型计算结果与现场数据吻合最好,准确率为91%,表明该模型比其他积液预测模型具有更好的性能,可用于对水平气井积液的判断。

风荷载作用下储罐罐壁的力学性能

为研究大型钢制储罐在风荷载作用下的力学特性,借助有限元软件ABAQUS,建立了静力风荷载作用下储罐有限元模型,对比分析裸罐(不含抗风结构)与加强罐(含抗风结构)在风荷载作用下迎风面与侧风面罐壁的应力与变形结果,以及储液对储罐抗风性能的影响。结果表明:迎风面罐壁受风压力作用,罐壁内凹,侧风面罐壁受风吸力影响,罐壁外凸;风荷载对空罐影响较大,抗风结构可以有效地减弱空罐状态下罐壁顶部的变形;充液状态下,风荷载对罐壁的作用效果不明显,在储液压力作用下罐壁最容易破坏的位置出现在距离罐底高度2.42 m处。

气井积液临界气速预测新方法

气井产生积液后,气体流速不足以将液体完全提升到地面,可能导致气井停产。准确预测气井临界气速可以提醒操作人员及时采取措施以预防积液发生。基于环状流最小气液界面剪切应力准则,结合管壁均匀液膜速度流场解析解,建立了临界气速预测新模型。该模型通过联立环状流的液相流量与气相动量方程得到气液界面剪切应力表达式,令其导数为零求解临界气速,简化了积液模型的求解流程。新模型考虑了井斜角、管径、压力和气芯中液滴夹带等因素对积液临界气速的影响。收集国内外不同文献中的室内实验数据以及现场生产数据,评估新模型和其他具有代表性的积液模型预测临界气速的精度,表明新模型要优于其他积液模型。对于管径为1 in、2 in、3 in、4 in、6 in垂直和倾斜管道实验室积液实验,新模型预测平均相对误差为1%;对于管径为2.441 in~4.28 in的直井和管径为1.75 in~6.18 in、井斜角为13°~64°的斜井,新模型预测的临界气速较生产数据平均相对误差不超过23%。

基于液膜反转的定向井临界携液模型研究

气井积液是苏里格区块大斜井开采中后期面临的一个重要难题,目前适用于定向井的临界携液模型研究较少,且常用携液模型忽略了管径、液体流速和角度的影响。借助多相管流实验开展了定向井携液机理实验,分析了管径、角度、液体流速等因素对气井积液的影响规律,并根据液膜反转机理,在BELFROID模型和WALLIS模型基础上,利用实验数据拟合出了WALLIS模型中参数C和m的计算方法,并考虑管径、气体密度、液体密度、角度、液体表观流速、重力加速度等参数,建立了新的临界携液模型,新模型在预测VEEKEN文献中62口积液气井时结果显示,准确率为91.94%,新模型的建立不仅是液膜反转理论的进一步完善,同时也为定向井积液时机的预测提供理论支撑。

不同负载下液化换能器动态电阻特性研究

针对液化超声中超声振子在不同负载下工作导致的换能器发热不同,进而影响换能器工作效率和使用寿命问题,从理论和实验方面研究了工作在串联谐振点的换能器在不同负载环境下的动态电阻变化和发热特性。研究获得了不同液体负载条件如不同液体温度、液体黏稠度、浸入深度、液体密度等下,换能器的动态电阻变化与换能器发热量的映射关系。针对串联谐振频率下的换能器,通过理论计算得到了动态电阻与电压电流关系。针对阻抗分析仪驱动功率较低,不能准确测试换能器有载时的动态电阻变化趋势的缺点,设计了一种测试换能器有载时的动态电阻变化趋势的方案。基于频率追踪芯片实现了频率追踪电路,保证了超声换能器工作频率始终处于换能器串联谐振点。本研究可为提升工作在复杂负载环境下的超声电源可靠性提供参考。

CAFeⅡ装置低温恒温器热负荷分析

低温恒温器作为超导直线加速器的最小加速单元,其在低温下的热力学性能将直接影响低温系统的运行成本和效率。低温恒温器的热负荷包括静态热负荷和动态热负荷。研究了低温恒温器的冷屏、超导腔、调谐器、耦合器、绝热支撑等主要元件的传热过程,对影响热负荷的关键因素进行了分析。结果表明,CAFeⅡ低温恒温器热负荷能够满足设计指标要求,为超导直线加速器稳定运行奠定了基础。

冲击载荷下蓄液结构动响应及防护机理的研究进展

工程实际中,飞机油箱、船舶液舱、油液储罐等各类蓄液结构可能面临炸药爆炸冲击波、弹丸侵彻等冲击载荷的威胁。在冲击载荷作用下,蓄液结构的动响应受载荷特性、结构形式、充液方式等多种因素影响,相应的结构防护机理涉及多相介质的流固耦合、波在不同介质中的传播、液体介质的空化、结构动态力学特性等多个科学问题。针对冲击载荷下蓄液结构的动响应及防护机理,总结了工程领域中典型的蓄液结构形式,分析了各类蓄液结构在爆炸冲击波、弹体侵彻及其联合作用等载荷下的结构动响应过程、结构破坏模式、载荷耗散过程、能量转化与吸收过程,总结了蓄液结构的冲击动响应特性,归纳了蓄液结构对各类冲击载荷的防护机理,从结构构型、结构动响应、理论研究方法、抗冲击防护技术等方面对蓄液结构抗冲击防护研究进行了展望。

多工况下的液驱多维力加载装置主轴速度控制

不同工况引起加载力之间的耦合效应降低了速度控制效果,为了更加精准控制不同工况下的主轴速度,提出一种多工况下的液驱多维力加载装置主轴速度控制方法。计算多工况下的液驱多维力加载装置主轴速度,以此作为控制器设计输入。在多种工况下,将液驱多维力加载装置主轴输入和输出速度之间的差值作为输入信号,通过模糊推理算法改进经典PID控制器,通过模糊检测调整改进后的控制器组建模糊自适应PID控制器,实现速度自适应控制。通过实验测试证明,所提方法可以精准地完成液驱多维力加载装置主轴速度控制,受工况影响较小。

Analysis of one-dimensional consolidation of soft soils with non-Darcian flow caused by non-Newtonian liquid

Based on non-Darcian flow caused by non-Newtonian liquid, the theory of one-dimensional (1D) consolidation was modified to consider variation in the total vertical stress with depth and time. The finite difference method (FDM) was adopted to obtain numerical solutions for excess pore water pressure and average degree of consolidation. When non-Darcian flow is degenerated into Darcian flow, a comparison between numerical solutions and analytical solutions was made to verify reliability of finite difference solutions. Finally, taking into account the ramp time-dependent loading, consolidation behaviors with non-Darcian flow under various parameters were analyzed. Thus, a comprehensive analysis of 1D consolidation combined with non-Darcian flow caused by non-Newtonian liquid was conducted in this paper.

型槽参数对斜直线槽液膜密封性能的影响

为进一步探索斜直线型槽对密封性能的影响机制,基于质量守恒边界并定义液膜密度比,建立斜直线槽液膜密封动压润滑模型;采用有限差分离散方程,对比分析液膜空化理论与实验值,验证计算模型与程序准确性;研究斜直线型槽参数包括槽数、槽深、径向和周向槽宽比对密封性能的影响。结果表明:不同倾斜角时,在临界范围内,增加槽数或增大槽深均有助于提升液膜承载力、增大泄漏量并有效降低液膜空化,尤其在较大倾斜角下;在一定范围内,虽均增大径向和周向槽宽比可提升液膜承载力、促进液膜空化发生及增大泄漏量,但影响规律不尽相同。以提升液膜承载力为目标,得出的最优型槽参数为槽数42、槽深25μm、径向和周向槽宽比分别为0.7和0.6。