基于AMESim的轴流先导式水击卸压阀动态特性分析

轴流先导式水击卸压阀常安装在成品油长输管道上,用于防止由于管道中突然停泵、阀门异常启闭等引起的管线压力骤增而造成的水击现象,从而达到保护管路以及管线中的阀门等设备的目的,对石油运输管线的安全运营起着至关重要的作用。以轴流先导式水击卸压阀作为研究对象,建立了其运动时的数学模型,在AMESim软件中搭建了其仿真模型,模拟实际水击现象,分析了其动态特性,并利用AMESim软件批处理功能分析了不同参数变化对阀门动态特性的影响。

氮气式水击泄压阀试验平台设计和试验研究

为实现对氮气式水击泄压阀的功能和关键性能进行充分研制试验,设计并搭建了一种能够满足工作压力高、流量大等试验条件的液流试验平台,并在试验过程中设计了包含设定压力、响应时间和设定压力误差试验在内的四项试验验证方法。根据所设计方法分别对型号为200YXY-100D的氮气式水击泄压阀主阀在氮气腔压力为1,2,3,4,5 MPa工况下试验平台进行验证试验。结果表明所设计液流试验平台和试验方法能够充分验证氮气式水击泄压阀和氮气供应系统结构强度、密封性能、动作可靠性和整阀系统的可靠性。

先导式水击泄压阀动作原理和密封机理的分析

介绍了先导式水击泄压阀的密封结构和动作过程,并对阀门的密封条件和要求及失效的原因进行了计算和分析,提出阀门在输油管路装置中安全状态运行的性能要求和必要条件。

氮气式水击泄压阀的定制测试及故障处理

介绍了原油长输管道场站所使用的氮气式水击泄压阀的结构、工作原理、定值测试方法及常见故障的处理等。

丹尼尔先导式水击泄压阀阀芯拆装工具的研制

水击泄压阀防止水击损坏管道,在保证管道安全平稳运行方面发挥了重要作用。文章通过研制一种丹尼尔水击泄压阀阀芯拆装工具的方式,解决了水击泄压阀维修过程中密封组套由于工具精度不够造成的损伤,大大提高了丹尼尔水击泄压阀维修作业成功率。

先导式水击泄压阀设定压力关键影响因素确定与验证

【目的】先导式水击泄压阀是用于输油管道防止水击压力破坏的关键设备,研究先导式水击泄压阀设定压力的影响因素有助于准确控制先导式水击泄压阀的设定值。【方法】从先导式水击泄压阀的结构组成与工作原理入手,分别讨论了弹簧力、摩擦力、导阀芯与导阀座密封结构、导阀活塞对先导式水击泄压阀设定压力的影响,得出先导式水击泄压阀设定压力的关键影响因素是导阀弹簧与导阀活塞的配置,并提出确保先导式水击泄压阀设定压力精度的主要措施,建立了试验系统对相关结果进行验证。【结果】当导阀弹簧选定时,在一定范围增大导阀活塞面积有利于提高先导式水击泄压阀设定压力的整体精度;当活塞面积与弹簧不变时,设定压力越大,设定压力精度越高;当导阀活塞面积一定时,增大弹簧力可使先导式水击泄压阀可调整的设定压力范围扩大。在试验验证测试中,通过配置不同的导阀活塞与不同的弹簧,得出在设定压力不变的条件下,随着活塞面积增大,先导式水击泄压阀实际起跳压力越接近设定压力,设定压力精度越高;在活塞大小不变的条件下,设定压力越高,先导式水击泄压阀实际起跳压力越接近设定压力,设定压力精度越高。【结论】为了进一步提升先导式水击泄压阀设定压力的设定精度,建议在工程应用中,结合实际优选弹簧与活塞结构、材质并进行优化组合。

输煤系统节能的探讨

针对目前在输煤系统节能方面存在的问题,对系统设备进行改造,推广采用了新材料、新技术,在现有条件下,尽力提升了输煤系统出力,从具体量化分析节能工程进行了客观的论述,为指导输煤系统节能工作有一定的借鉴意义。

氮气式水击泄压阀设定压力精度的影响因素

为了揭示影响氮气式水击泄压阀设定压力精度的关键因素,从氮气式水击泄压阀的结构组成和工作原理入手,建立了影响氮气式水击泄压阀设定压力临界点处的力学关系方程,分析认为影响氮气式水击泄压阀设定压力精度的主要影响因素是减压阀的精度、环境温度对氮气压力的影响、活塞体所受摩擦力、阀座密封结构的设计及弹簧刚度的稳定性等,进而提出了控制设定压力精度的的方法。根据该理论改进的氮气式水击泄压阀,获得了设定压力精度达到±1%的试验结果。

DANIEL氮气式水击泄压阀的安装和功能维护

DANIEL氮气式水击泄压阀具有流通能力强、反应灵敏、适应性强、安全稳定性好、自动化程度高等特点,可跟踪阀前端水击压力的变化,当输油管道中的介质发生水击,压力达到阀门的设定值时,其能够快速开启,从而有效保护管道。介绍了仪征-长岭原油管道全线十座站场使用的DANIEL氮气式水击泄压阀的结构,工作原理,安装、启用及停用操作过程,阐述了压力设定点的检查过程和试验方法,指出了常见故障,提出了解决方案,可供长输原油管道的管理人员、技术人员和设备维护人员参考。

先导式水击泄压阀泄漏原因及解决措施

为解决先导式水击泄压阀运行过程中频发的泄漏问题,在研究其工作机理的基础上,充分考虑输送介质、管道工艺、环境温度等因素的影响,指出导致泄漏的主要原因为锥状阀芯不能完全复位、阀体密封件和先导阀失效以及环境温度的影响,进而提出了定期保养、安装前置过滤器和排污装置、先导阀专项检查、投运电伴热等解决措施。在先导阀专项检查中提出了采用加压法快速判断先导阀密封件的完好性,并可在检修后进行阀门离线稳压测试和定值测试。实践结果表明:以上措施能够有效消除泄压阀泄漏故障,加压法可缩短解决泄漏故障的时间,降低难度,提高检修效率。

Pressure Variation in the Fluid inside a Tesla Turbine

The recent technological developments being applied to Tesla like turbines for converting fluid energy into mechanical （axis） energy often lead to non-frequently used models. Given a disk shaped machine rotating around its own symmetry axis, part of the machine energy is transferred to the fluid itself, pushing it to the disk periphery. This way the farther the exhaust orifice is from the disk outside contour, the larger will be the pressure loss experienced by the system. This work studies the overall energy balance and momentum exchange between fluid and machine. Simple calculation shows that for total pressure gradients above two bar the machines become inefficient for having tangential velocity whose intensity is 50% higher than the intensity of the jet velocity prior to the interaction. For values of the pressure gradient above 5.7 bar, the machine peripheral velocity is equal to the incident jet velocity. In this case it is not possible to deliver power under permanent regime. Finally it is shown that when the feeding pressure of an impulse turbine is enough for more than one stage, then one should use this option to obtain thermal efficiencies similar to those of reaction machines. The jet of fluid to move a Tesla like turbine should enter the unit as close as possible to the direction tangential to the movement, （i.e., normal to the radius at the considered position）. This fluid should leave the machine right after interacting with it. Any permanence of the fluid after transferring its momentum to the machine can be extremely prejudicial to the system behavior.

A novel experimental system for performance evaluation of water powered percussive rock drill

A set of water powered excavation test system was developed for the comprehensive performance testing and evaluation of water powered percussive rock drill indoors. The whole system contains hydraulic power section, electronic control system, test and data acquisition system, and assistant devices, such as guideway and drilling bench. Parameters of the water powered percussive rock drill can be obtained by analyzing testing data, which contain impact energy, front and back cavity pressure, pressure and flow in each working part, drilling velocity, frequency and energy efficiency etc. The system is applied to test the self-designed water powered percussive rock drill SYYG65. The parameters of water powered percussive rock drill with impact pressure of about 8.9 MPa are 58.93 J for impact energy, and 8.97% for energy efficiency, which prove the effectiveness of system.

Unsteady separation of jet branch by cutout of rotating Pelton bucket

As a part of boundaries for a free curved surface of a Pelton bucket,the cutout is indispensable to secure the smooth entrance of the unsteady inflow of water jet into the rotating bucket.The cutout of the rotating bucket unsteadily separates a free jet into two branches in both space and time:the impinging branch landing on the relevant bucket surface,and the flow-off branch separated by the cutout toward the preceding bucket.In order to investigate the unsteady jet separation by the cutout three-dimensionally,a semicircular free jet was discretized into 641 nodes of boundary-fitted grids.The position P of impinging jet branch landing on the bucket surface was acquired with the relative velocity W and the water depth D at each node.The trailing edge surface of the flow-off jet branch was simultaneously computed unsteadily.The complicate unsteady interaction of the bucket cutout with the branched free jets was clarified visually with the 3D view of illustrations in order to research the unsteady hydraulic performance of Pelton turbines in space and time.

A Twin Unidirectional Impulse Turbine for Wave Energy Conversion

A twin unidirectional impulse turbine has been proposed in order to enhance the performance of wave energy plant. This turbine system uses two unidirectional impulse turbines and their flow direction is different from each other. However, the turbine characteristics have not been clarified to date. The performances of a unidirectional impulse turbine under steady flow conditions were investigated experimentaUy by using a wind tunnel with large piston/cylinder in this study. Then, efficiency of the twin impulse turbine have been estimated by a quasi-steady analysis using experimental results.

Performance studies on an oscillating water column employing a Savonius rotor

A new oscillating water column (OWC) design is proposed in this study to incorporate a simpler Savonius type turbine. Conventional OWC devices employ a bi-directional turbine such as a Wells or an Impulse turbine to extract energy from the air. The disadvantages of the Wells turbine include its inability to self start and stalling. The Savonius turbine is much cheaper and is an effective option at low Reynolds numbers. In the current rectangular OWC device, unlike the circular OWC, the width of entry of the capture chamber can be increased without being influenced by the diameter at the turbine section. To improve its primary capture efficiency, the front and rear walls of the OWC are inclined to minimize reflection. The Savonius rotor characteristics are studied with respect to the change in frequency of the incoming waves. The rotor rpm is sensitive to wave period and primary conversion efficiency while changes in depth only affect the rotor rpm at lower frequencies. The Savonius rotor shows promising results and can be incorporated into large scale OWC devices to reduce costs of the turbine component of the system.

OWC air chamber performance prediction under impulse turbine damping effects

Oscillating water columns(OWCs)are most widely used in coastal wave energy conversion.The air duct opens into the atmosphere through the air turbine,which is the power take-off device,and this results in a pressure drop across the air chamber.However,because of the complex configure of the impulse turbine and its high rotation speed,it is difficult to install it in the experimental simulator and numerical model.Therefore,the turbine damping effects on the operation of the OWC air chamber are induced to predict its performance more accurately.Orifice plates are used as a substitute for the impulse turbine as it generates a similar pressure drop and power output;the experimental and numerical pressure drops and output powers are compared.A 3D numerical wave tank based on the two-phase VOF model is established using the commercial CFD code Fluent,which can predict air flow and pressure variations in the chamber and duct.Water surface elevations,air flow velocity and pressure variation inside the chamber with the orifice plate are studied numerically,and validated by the corresponding experimental data.The air chamber of the Yongsoo OWC pilot plant is used as the engineering project case.The operating performance of the air chamber installed with a 0.428D orifice plate as the substitute for the designed impulse turbine is computed and analyzed.It is found that the turbine damping effects will cause around 30%reduction in the peak values of the pneumatic energy output of the OWC air chamber in the resonant wave domain.

Numerical predictions and stability analysis of cavitating draft tube vortices at high head in a model Francis turbine

Draft tube vortex is one of the main causes of hydraulic instability in hydraulic reaction turbines,in particular Francis turbines.A method of cavitation calculations was proposed to predict the pressure fluctuations induced by draft tube vortices in a model Francis turbine,by solving RANS equations with RNG k-turbulence model and ZGB cavitation model,with modified turbulence viscosity.Three cases with different flow rates at high head were studied.In the study case of part load,two modes of revolutions with the same rotating direction,revolution around the axis of the draft tube cone,and revolution around the core of the vortex rope,can be recognized.The elliptical shaped vortex rope causes anisotropic characteristics of pressure fluctuations around the centerline of the draft tube cone.By analyzing the phase angles of the pressure fluctuations,the role of the vortex rope as an exciter in the oscillating case can be recognized.An analysis of Batchelor instability,i.e.instability in q-vortex like flow structure,has been carried out on the draft tube vortices in these three cases.It can be concluded that the trajectory for study case with part load lies in the region of absolute instability(AI),and it lies in the region of convective instability(CI)for study case with design flow rate.Trajectory for study case with over load lies in the AI region at the inlet of the draft tube,and enters CI region near the end of the elbow.

Pneumatic Performance of Staggered Impulse Turbine for OWC Wave Energy Convertor

A staggered impulse turbine is proposed for asymmetric air flows in Oscillating Water Column wave energy plants, which is expected to enhance the pneumatic power output in a wave cycle. The setting angle of rotor blades is set as 5°. The 3D numerical simulations were conducted under steady conditions using MRF and Mixing Plane model based on CFD software Fluent 12.0. Its mean efficiencies under different velocity amplitude ratios are studied using quasi-steady analysis, which derive corresponding data from the numerical simulation. It is found that the staggered turbine shows better performance than the conventional one under the asymmetrical air flows. Furthermore, its mean efficiency and output-work in a wave period are compared with another unsymmetrical twin impulse turbine system. The results show that the staggered turbine shows better output-work performance than the twin turbine system over the high flow coefficient domain(φ>0.7), which provides more choices to future research on turbine's optimization.