液压驱动压裂泵液压系统设计及其脉动的抑制

针对传统机械式压裂泵冲次高、易损件寿命短等缺点,提出了液压驱动式压裂泵,设计了"半开半闭式液压系统",建立了仿真模型,搭建了试验样机,结果表明:仿真模型准确,液压驱动式压裂泵也可以实现高压输出,受液压缸泄露、魏氏效应、系统固有换向时间的影响,压裂泵存在压力和流量脉动,且随负载压力的增大而增大。根据压力和流量脉动特点,设计了一套由柱塞缸、气缸和蓄能器组等构成的气缸式蓄能器脉动抑制装置,结果表明:该装置能显著抑制压力和流量脉动;且脉动随蓄能器容积或预充气压力的增大而减小;在该装置的作用下,液压驱动式三缸压裂泵的压力脉动等效于机械式五缸压裂泵。     

柱塞泵压力脉动随机动力特性分析及实验研究

考虑流体流动、转子转动等随机性引起的压力脉动波动特性,提出了柱塞泵压力脉动的随机动力学表达式,并通过三柱塞泵-管道系统实验获得压力脉动随机参数的概率分布规律为极值I型分布。根据所提出压力脉动随机动力学表达式,应用蒙特-卡罗方法进行管道动力响应分析,通过与实验数据对比验证了所提出表达式的合理性。根据实验及数值分析结果发现泵输出压力脉动与管道位移响应均服从极值I型分布,随机压力脉动频率特性中出现和实验一致的1/3倍频。管道动力响应数值分析结果与实验吻合良好,证明所提出的表达式能够准确模拟柱塞泵管道系统内压力脉动随机动力特性,对管道系统的安全性和可靠性设计具有重要的应用价值。     

甲胺泵管路振动故障分析

对某炼化厂的高压甲胺泵的管路振动进行了测试分析,通过对各个管路系统的不同测点的振动频谱分析,给出了导致甲胺泵管路振动过大的起因是压力脉动频率与管线的固有频率接近的结果,提出了相应的减振措施.     

伴随气泡和气穴的低压液压管路瞬态分析

利用流体动力学原理,基于低压液压管路瞬态脉动过程中气泡和气穴同时存在的假设,在连续方程和运动方程的基础上,建立了低压液压管路中伴随气泡和气穴的瞬态脉动数学模型,给出了摩擦阻力项数学模型以及气泡和气穴的体积计算数学模型。并采用有限差分法和Matlab/Simulink,对一段等径水平直管道中有气泡和气穴产生时的压力瞬态脉动特性进行了仿真分析和实验研究。瞬态压力脉动波的仿真结果与实验数据的比较表明:所提出的伴随气泡和气穴的低压液压管路瞬态数学模型是合理的,仿真方法是可行的。     

离心泵流动诱发振动特性数值计算分析

建立了一种适用于离心泵等叶轮机械流动诱发振动工程计算的数值模型和方法流程。基于URANS方程求解泵内流场,在流场非定常计算过程中输出叶轮所受时域脉动压力,将脉动压力通过FFT转换到频谱并以之作为泵组结构的振动激励源,采用隐式有限元方法进行泵组结构振动响应的计算。计算方法通过测试得到验证,可以用于离心泵流动诱发振动特性的计算评估和低噪声设计。完成了原型和改进型船用海水泵在设计工况下流动诱发振动响应的计算,分析了两型泵流场、振动激励源和振动响应等特性。计算表明,泵的改型设计显著减小泵内压力脉动以及振动激励源,改型泵振动小于原泵。     

管路脉动有源控制邻频插值次级通道建模方法

管路脉动有源控制系统中,泵源工作时产生的线谱噪声会对次级通道辨识结果造成较大误差。为解决泵源运行状态下次级通道建模的问题,理论分析了泵源关闭和启动两种状态下给次级通道建模造成的影响。设计了邻频插值次级通道建模的方法,有效地避开了线谱噪声源。该方法首先辨识得到待建模频率点ω_0处相邻两侧频率点的次级通道模型,并提取两侧频率点处模型的幅值和相位,对其线性插值作为ω_0处次级通道的幅值和相位特征。在管路脉动有源控制实验系统中,利用邻频插值建模方法进行了建模实验,验证了方法的可行性,并将模型应用在改进后的FxLMS算法中,在实验系统中取得了多根线谱均在25 dB以上稳定的控制效果。     

泵—马达液压传动系统中的压力拍振分析

在泵—马达液压传动系统中,由于泵和马达的周期性吸油排油,不可避免地存在流量脉动,当泵和马达脉动的频率相接近时,系统会发生压力拍振现象。建立泵-马达传动系统的压力脉动数学模型,从理论上分析压力拍振的周期和幅值特点。采用集中参数法建立泵-马达传动系统的仿真模型,并通过仿真和试验分析系统压力拍振的规律,结果表明当泵和马达脉动频率比较接近时会发生压力拍振且拍振幅值随频率接近程度增加而增加。在压力拍振机理分析的基础上,提出合理选取传动比和柱塞数目可以有效抑制系统压力拍振。     

考虑管路效应的负载敏感泵动态特性分析

以多路阀和负载敏感泵组成的负载敏感控制回路在工程机械中得到了广泛应用,其中负载敏感泵与负载及管路之间的耦合作用很容易引起输出压力和流量的脉动,轻则影响执行器的控制精度,重则导致管道破裂或变量泵提前损坏。针对这一问题,详细分析了带多路执行器的负载敏感泵的动态特性,其中特别研究了管路参数对系统动态特性的影响,为此类系统的设计和调试提供参考。     

一种管路压力脉动抑制装置优化设计及试验分析

针对船舶系统柱塞水泵等辅机设备管路压力脉动大的问题,设计出一种基于蓄能器吸能和孔板滤波原理的管路压力脉动抑制装置。根据压力脉动抑制装置工作原理,对蓄能器容积、蓄能器充气压力、开孔角度、开孔数量、孔径等参数进行优化设计,并对研制出的样机进行试验。试验结果表明：管路压力脉动抑制装置对不同频谱的压力脉动均具有较好的衰减效果,输出压力1 MPa～2.5 MPa时,柱塞泵出口管路压力脉动衰减率达50 %以上。     

液压系统的共振现象及其处理

液压系统的共振现象及其处理陈奎生（武汉钢铁学院）在液压系统中，当管网的固有频率与泵源的脉动频率（或倍频）及溢流阀的谐振频率接近时，系统可能会出现共振现象，结果导致压力急剧波动，溢流阀产生强烈的振动、撞击、哨叫声、甚至发生破坏性后果。在此笔者根据调试实...     

Evaluierung von Abpumpkurven am Beispiel einer Glimmentladungsquelle

Evaluation of pumpdown curves illustrated for a glow discharge source In the present state, the GLOW DISCHARGE OPTICAL EMISSION SPECTROMETRY (= GD‐OES) is distinguished by an extraordinary quick material analysis. The analysis time (gross time of analysis 2 ‐ 5 minutes) is determined mainly by the pumping time of the source of the equipment, the reliability of the spectral analysis is ‐ especially in the case of thin films (film thickness < 100 nm) ‐ determined by the cleanness of the gas in the source and the surface of the source. In the case of the used commercial spectrometer equipment it was possible to reduce the evacuation time and the final pressure in the source for improvement of the cleanness of the gas at the place of the analysis with the help of a proper conduction of the venting and pumping process and by a proper dimensioning and construction of the pumping set of the equipment. An automatic and computer aided evaluation of the pressure vs. time run in the source chamber gives advises to the user of the equipment about possible leaks (caused e.g. by the wear of sealing) in the equipment or about contamination of inner surfaces, because the pressure vs. time run in the chamber is determined by parameters which are characteristic of the equipment (e.g. effective pumping speed, leak rate, and outgassing or desorption rate). By variation of these parameters the calculated pressure vs. time run is fitted to the experimental measured pressure vs. time curve. Parameters found by this method are important characteristics describing the situation of the equipment (source and pumping set). On the base of these results the user of the device can carry out a leakage detection or clean or replace components of the instrument in time. This check of the device increases the reproducibility of the analysis of materials.     

An equivalent pressure source for the heart

A technique is described for the representation of the left ventricle as a one-port source characterized by a generator pressure and an internal impedance. The Fourier components of the pressure and impedance are determined from phasor analysis performed on recorded time-domain functions of pressure and flow under two conditions of loading. One condition is the quiescent state corresponding to normal operation of the circulatory system, and the other is obtained by use of a phase-shift balloon pump situated in the descending thoracic aorta. The use of the balloon pump for determining source parameters is novel. The Fourier components of pressure and impedance are determined for the first five harmonics of the quiescent pulse rate. Heart failure is simulated by ligation of all branches of the anterior descending coronary artery. The source parameters have been found to vary considerably between normal and failing hearts. Valve impedance and the impedance at the root of the aorta were also measured. The generator time-domain pressure waveforms were determined from the Fourier components. Effects of long duration pumping, upon the source parameters were found. The ratio of the calculated magnitudes of internal to external or load impedance indicates the possibility of considering the heart as a pressure source.     

Dynamical model of total and partial pressures in a vacuum system due to intermittent desorption

The dynamical characteristics of a vacuum system in respect of pressure are critical for studying the dynamical desorption processes such as those produced by mechanically stimulated desorption in vacuum. In the present work, a mathematical model of the instant pressure in a vacuum system has been developed assuming an intermittent square-wave desorbed gas flow. In this case, the duration of the pressure transient is proposed to be used as a generalized criterion of the rate of the desorbed gas flow and, consequently, of the instant pressure behaviour. The dependences of the transient duration on the pumping speed, system volume, molar mass of the desorbed gas as well as on the period and the on-off ratio of the desorption process have been revealed. The developed model made no assumptions on the physical nature of the gas source, i.e. desorption, leaking, etc., and can be used for different applications.     

Controlling of material analysers of the GD-OES type with help of pump-down curves

Today, material analysis in industry and research centres is very often performed by the glow-discharge optical emission spectrometry (GD-OES), which allows an extraordinarily quick material analysis (average time of analysis: 2-5 min) and a determination mainly by the pumping time of the glow discharge source. The reliability of the analysis is, especially in the case of thin films (film thickness <100 nm), determined by the purity of the discharge gas and of the surface of the source and sample.We could reduce the ultimate pressure and increase the purity of the gas at the place of analysis by improving the dimensions and construction of the pumping set, and the conduction of the pumping and venting process of a given commercial spectrometer device.Moreover, an automatic and computer-aided evaluation of the pressure vs. time run in the source chamber can inform the user about possible leaks or contamination of inner surfaces. For this purpose, it is possible to use the control computer of commercial equipment and the data acquisition system of the GD-OES instrument. Thus, one can receive important hints from the p-t plot regarding the equipment and can start leak detection, cleaning of the source chamber or replacing of components in time.     

A reliability method for optimization of [+,−]n fiber reinforced composite pipes

This paper presents damage strength optimization of laminates using a reliability-based method. Two complementary analyses are developed: the first is a mechanical analysis of damage behavior using a thermodynamics framework that determines the failure criterion; the second is a reliability method which takes not only randomness, but also statistical uncertainties into account for failure probability calculation. This method is based on a first order reliability method that requires the resolution of a constrained problem of optimization. To solve this problem, a hybrid algorithm, combining evolutionary computation techniques with deterministic procedure is presented. Filament-wound pipe optimization under pressure is discussed as a working example.     

Reliability formulation for composite laminates subjected to first-ply failure

Methods formulated on the basis of the concept of first-ply failure and the structural reliability theory are presented for the reliability analysis of laminated composite plates. In the reliability formulation, an appropriate phenomenological failure criterion is used to establish the limit state equation of the laminated composite plates, and different numerical techniques are employed to evaluate the reliability of the plates. Experimental investigations of lamina strengths and first-ply failure loads of laminated composite plates were performed. Baseline probability distributions of lamina strength parameters constructed from the test data are used to study the reliability of the laminated plates. The accuracy of the proposed models in reliability assessment of the laminated plates are verified by the experimental results on first-ply failure load distributions.     

Breaking the pumping speed barrier in mass spectrometry: discontinuous atmospheric pressure interface

The performance of mass spectrometers with limited pumping capacity is shown to be improved through use of a discontinuous atmospheric pressure interface (DAPI). A proof-of-concept DAPI interface was designed and characterized using a miniature rectilinear ion trap mass spectrometer. The interface consists of a simple capillary directly connecting the atmospheric pressure ion source to the vacuum mass analyzer region; it has no ion optical elements and no differential pumping stages. Gases carrying ionized analytes were pulsed into the mass analyzer for short periods at high flow rates rather than being continuously introduced at lower flow rates; this procedure maximized ion transfer. The use of DAPI provides a simple solution to the problem of coupling an atmospheric pressure ionization source to a miniature instrument with limited pumping capacity. Data were recorded using various atmospheric pressure ionization sources, including electrospray ionization (ESI), nano-ESI, atmospheric pressure chemical ionization (APCI), and desorption electrospray ionization (DESI) sources. The interface was opened briefly for ion introduction during each scan. With the use of the 18 W pumping system of the Mini 10, limits of detection in the low part-per-billion levels were achieved and unit resolution mass spectra were recorded.     

On the basically single-type excitation source of resonance in the wind tunnel and in the hydroturbine channel of a hydraulic power plant

We have investigated the spectra of pressure pulsations in the near field of the open working section of the wind tunnel with a vortex flow behind the tunnel blower formed like the flow behind the hydroturbine of a hydraulic power plant. We have made a comparison between the measurement data for pressure pulsations and the air stream velocity in tunnels of the above type and in tunnels in which a large-scale vortex structure behind the blower is not formed. It has been established that the large-scale vortex formation in the incompressible medium behind the blade system in the wind tunnel is a source of narrow-band acoustic radiation capable of exciting resonance self-oscillations in the tunnel channel.     

A FRACTURE AND SEVERITY ANALYSIS OF COMPOSITE CERAMICS

Ceramic composite crucibles failed when they were operated under extreme conditions of temperature and heating rate. To analyze the failure causes, fracture stress and fracture toughness values were ascertained and previously reported. Moreover, a new failure criterion for ceramics was proposed based on the existence of a crack-tip process zone. A probabilistic failure assessment curve was proposed to evaluate quantitatively the reliability of ceramics. By using the above data and theories, a fracture and severity analysis for crucibles has been completed. Some manufacturing techniques are proposed to improve reliability during service.     

毛乌素沙漠风积砂动强度特性试验研究

随着陕北油气资源的不断勘探和开发,毛乌素沙漠地区风积砂的岩土工程特性问题逐渐成为当地工程建设的制约因素。该文在均等固结条件下,采用孔压破坏标准,对毛乌素沙漠饱和风积砂进行了不同干密度和不同围压下的固结不排水等幅循环动三轴强度试验。在试验基础上,得到了不同密度不同围压下的风积砂动强度曲线和动孔隙水压力发展曲线。针对天然气压缩机的类无限循环动荷载特性,探讨了无限循环荷载作用下毛乌素沙漠饱和风积砂的动强度问题。并基于摩尔-库仑强度准则获得了适用于毛乌素沙漠风积砂在无限循环荷载作用下的等效动抗剪强度参数及破坏判据。