Nonlinear stress analysis of offshore pipelines during pickup operations

This paper presents a method of analyzing the stresses in a submarine pipeline as it is picked up off the sea floor by barge davits. A nonlinear large-deflection analysis is used and the pipeline is modeled as a series of finite beam segments from the ocean bottom on up. The governing equations are derived and the pipeline configuration satisfying known boundary conditions is determined by an initial-value approach using an iterativetype technique. Boundary conditions at the mudline are identified by modeling the pipeline resting on the ocean bed as a semi-infinite tensioned beam on an elastic foundation. The effects of a nonlinear stress-strain curve for the pipe material are included and both Ramberg-Osgood and Hutchinson formulations are considered. With the technique suggested, any given pickup procedure can be analyzed or a reliable procedure can be developed based on a given allowable pipe stress level and any desired improvement in the final configuration and/or stress levels may be achieved by a variation of the parameters involved. A practical example is examined to demonstrate the applicability of the analysis presented, which should provide a useful tool in either judging or developing a pickup procedure.     

基于BPPID的疏浚管道稳定流速控制

针对疏浚船管道输送过程中泥浆管道流速难以控制,容易造成较大的功耗、磨损甚至会堵管、爆管等风险,本文以疏浚泥泵管道输送实验台为研究对象,提出一种基于BP神经网络的PID控制器,对管道输送流速进行稳定控制。在采用系统辨识方法对实验台进行建模的基础上,将BPPID与传统PID控制器进行仿真对比分析并利用模型实验台分别进行了流速阶跃变化和流速跟踪实验。实验结果表明BPPID控制对突变工况具有自适应自学习能力,为实际挖泥船输泥管道的稳定流速提供借鉴。     

Continual flow pipelines: achieving resource-efficient latency tolerance

With the natural trend toward integration, microprocessors are increasingly supporting multiple cores on a single chip. To keep design effort and costs down, designers of these multicore microprocessors frequently target an entire product range, from mobile laptops to high-end servers. This article discusses a continual flow pipeline (CFP) processor. Such processor architecture can sustain a large number of in-flight instructions (commonly referred to as the instruction window and comprising all instructions renamed but not retired) without requiring the cycle-critical structures to scale up. By keeping these structures small and making the processor core tolerant of memory latencies, a CFP mechanism enables the new core to achieve high single-thread performance, and many of these new cores can be placed on a chip for high throughput. The resulting large instruction window reveals substantial instruction-level parallelism and achieves memory latency tolerance, while the small size of cycle-critical resources permits a high clock frequency     

Nonstationary characteristics of a single-server queue system with nonordinary input flow

A single-server queue system with nonordinary input flow that depends on the queue length is considered. Sufficient existence conditions for the stationary distribution of the queue length provided that the process under study is an eigen process are obtained. Recurrence formulas for the Laplace transform of the nonstationary distributions of the queue length are derived.     

Delta V现场总线控制系统在煤气混合站的应用

介绍了罗斯蒙特Delta V现场总线控制系统及其仪表的特点和在煤气混合站中的应用。     

基于神经网络PID的疏浚管道泥浆流速控制

疏浚作业中,泥浆管道内物料的组成、粒径、浓度等随水下地形土质等变化很大,易造成流速波动甚至堵管、爆管等故障,因此泥浆流速稳定控制对泥浆输送的效率和安全具有重要意义;疏浚管道输送系统具有非线性、大时滞和参数时变等特征,传统PID控制方法效果不佳,故此将BP神经网络和传统PID控制算法相结合,并将其应用于泥浆流速控制中。以河海大学管道输送实验平台为对象,采用受控自回归CAR模型描述泥泵变频器频率与管道泥浆流速之间的关系,通过实验和数值处理对模型进行离线辨识;在此基础上通过仿真对比传统PID、单神经元PID和BP-PID的流速控制性能,发现BP-PID控制器的超调量仅为3.8%,响应时间为11s,控制性能较好;最后通过在体积浓度~10%到~30%泥浆范围内,泥浆浓度小幅度和大幅度增减实验,对流速控制方法进行了验证,结果表明在浓度平缓或剧烈波动时,采用BP-PID控制算法的流速控制系统,均能够在保证输送安全的前提下,快速、稳定地达到目标流速,具有较好的自适应控制性能。     

基于管内声波的输气管道泄漏诊断方法研究

输气管道发生泄漏后如果没有及时发现,将可能造成巨大的生命财产损失及环境污染,因此研究输气管道泄漏监测技术具有非常重要的意义.本文研究基于声波传感器的输气管道泄漏检测和定位问题,首先利用短时傅里叶变换方法找到泄漏声信号的频率特征,然后通过分析某个频段内的信号幅值来判断管道是否发生泄漏.在检测到泄漏后,利用FIR滤波器对特征频段内的声信号进行滤波,最后通过对信号包络的分析实现对泄漏的定位.基于实际管线历史数据的离线实验表明了该方法的有效性.     

Nonlinear control solutions to prevent slugging flow in offshore oil production

Feedback control is an efficient and economical solution to prevent slugging flow regimes in offshore oil production. For this, a choke valve at the topside platform is used as the manipulated variable to control the pressure or the flow rate in the pipeline. The primary challenge for anti-slug controllers is robustness. The lack of robustness is due to changes in inflow conditions, the process nonlinearity, and modeling errors. In particular, the nonlinearity combined with an inverse response behavior makes the control of the topside pressure more difficult. We have conducted nonlinear and linear analysis and evaluated four control designs experimentally with both subsea and topside pressures. The control designs are (1) feedback linearization with measured outputs, (2) gain-scheduling IMC (internal model control) based on identified model, (3) PI control with an adaptive gain based on a static gain model, and (4) state feedback with state estimation by a nonlinear high-gain observer. We compared the robustness of these controllers regarding tolerance to time delay, change of the operating point and inflow disturbances. All the controllers could handle 30% step changes (disturbances) in inflow rates and remained stable. The gain-scheduling controller was more robust against time delay than the other controllers. By applying the high-gain observer, the stabilization was achieved in an acceptable range when only the topside pressure was available. However, the observer diverges when using a subsea pressure measurement which from a controllability point of view should be the easiest controlled variable. Nevertheless, this result agrees with the observability theory.     

Map building method for urban gas pipelines based on landmark detection

This paper presents a map building method for an in-pipe robot to navigate inside urban gas pipelines autonomously, whose configuration is unknown or partially known. In the first, we explain the reason why the navigation in the pipeline is difficult and then, present a method for obtaining a robot’s posture by using a pipeline’s unique geometrical features. The robot can obtain its heading direction by detecting the standardized geometries of pipe elements. Based on the method, we propose a robot controller consisting of discrete and continuous controllers. The discrete controller is activated by pre-defined events and generates appropriate paths for exploration. The continuous controller receives the desired path and physically moves the robot to the desired path. The method is implemented in an in-pipe robot, called MRINSPECT-V and its effectiveness is validated.     

MEMS-based gas flow sensors

Micro-electro-mechanical system (MEMS) devices integrate various mechanical elements, sensors, actuators, and electronics on a single silicon substrate in order to accomplish a multitude of different tasks in a diverse range of fields. The potential for device miniaturization made possible by MEMS micro-fabrication techniques has facilitated the development of many new applications, such as highly compact, non-invasive pressure sensors, accelerometers, gas sensors, etc. Besides their small physical footprint, such devices possess many other advantages compared to their macro-scale counterparts, including greater precision, lower power consumption, more rapid response, and the potential for low-cost batch production. One area in which MEMS technology has attracted particular attention is that of flow measurement. Broadly speaking, existing micro-flow sensors can be categorized as either thermal or non-thermal, depending upon their mode of operation. This paper commences by providing a high level overview of the MEMS field and then describes some of the fundamental thermal and non-thermal micro-flow sensors presented in the literature over the past 30 years or so.     

基于分布式光纤传感器的输气管道泄漏检测方法

针对传统方法难以精确诊断输气管道泄漏的难题,提出采用准分布式光纤B ragg光栅(FBG)传感技术实现天然气管道泄漏的在线监测技术。利用一条FBG光缆作为传感器,并行铺设在天然气管道附近,拾取管道由于泄漏、附近机械施工和人为破坏等事件产生的压力和振动信号,通过匹配光栅法和自动识别技术检测管道泄漏并进行定位。实验结果表明:该方法可以实现对天然气管道泄漏进行诊断并定位。     

多通道气体流量计算机的研制

针对目前流量计算机存在成本过高、计算速度较慢等问题,研制了基于内含矢量浮点单元VFP的S3C6410嵌入式微处理器、Linux操作系统和通过内部串行总线联接多达12个流量采样输入通道的气体流量计算机。主要阐述了该流量计算机的硬件和软件的设计。测试结果表明所设计的气体流量计算机能满足计量精度和实时性的要求。     

A technique implemented in the VOLNA code package to simulate the natural gas flux in pipelines

The paper presents an explicit Lagrangian-Eulerian technique implemented in the VOLNA code package for simulating the transient fluxes of natural gas in pipelines. The test calculations of stationary problems show that the technique has attained the second-order spatial convergence for smooth fluxes and provides acceptable accuracy in practical calculations.     

微小流量pVTt法气体流量标准装置的研制

介绍了20LpVTt法气体流量标准装置的设计原理和方案,并给出了装置中主要参数的测试方法及装置的不确定度评定。     

MEMS气体流量传感器的简易流量测试装置

为了完成所研制的MEMS气体流量传感器样品的流量测试与标定,设计制作了一种由标准流量发生器和传感器信号读出与数据采集电路组成的简易流量测试装置。标准流量发生器由注射器和可更换的砝码组成,利用不同的砝码配重,在注射器出气口产生合适的恒定气体流速。通过理论分析和Ansys有限元数值仿真,验证了简易标准流量发生器的可行性。传感器信号读出与数据采集电路基于内建多路A/D转换器的单片机实现,具有传感器加热电阻器的恒温控制、流量信号的数字检测和显示的功能。采用该简易流量测试装置对自行研制的MEMS气体流量传感器进行了流量测试与标定,获得了待测器件的标定参数、传感器流量测量的绝对误差和相对误差。     

Development and evaluation of an offshore oil and gas Emergency Response Focus Board

IntroductionThe primary objective of this research was to explore the use of an interactive whiteboard as an Emergency Response Focus Board (ERFB) for offshore emergency response teams (ERT) during a training and assessment process.MethodsThirty-seven participants completed simulation testing in a randomized study design with two visual display conditions (static and dynamic display). Outcome measures included speed and accuracy of response to situation awareness questions presented orally during three separate simulation freezes, and self-rating of performance.ResultsResults indicate that the type of ERFB display significantly influenced the speed and accuracy of responses. Qualitative results indicate that situation awareness was increased when using the dynamic ERFB.ConclusionsIt can be concluded that the dynamic ERFB offers an objective measure of performance and as a consequence, it is recommended that dynamic ERFBs be implemented into future offshore emergency response assessment training.Relevance to industryGiven the enormous amount of information available during an emergency, the dynamic ERFB offers an improved system for data logging, consolidation of information, and greater comprehension of relevant resource allocation factors.