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闫贝翻译 脉动缓冲器工作原理


UNDERSTANDING HOW PULSATION ACCUMULATORS WORK J. C. Wachel and S. M. Price Engineering Dynamics Incorporated San Antonio, Texas 脉动缓冲器工作原理 J. C. Wachel and S. M. Price 工程动力公司 San Antonio, Texa

s ABSTRACT Pulsation accumulators are used in reciprocating pump installations to reduce pump manifold pulsations and to attenuate pulsations transmitted into the piping. The pump and piping system form a complex acoustical system which has many acoustical and mechanical frequencies and the potential for high vibration and component failure problems .Many times the pulsation characteristics of the system are not calculated prior to installation.and an accumulator is selected based on pressure and flow rate criteria.In some cases ,this is acceptable as can be attested by the numerous installations that are installed and have operated successfully without problems.However,many installations do experience high vibrations ,piping and component failures , cavitations in the suction manifold , and generally poor reliability.These problems are often the result of the failure to consider the system’s acoustical characteristics when selecting an accumulator.

摘要
在往复泵中使用缓冲器旨在消减泵的主管线脉动并减缓脉动在管道内的传 播。 泵及其附属管道形成一个复杂的声学系统,该系统具有多阶声学及机械固有 频率,且该系统潜存剧烈振动和管件失效等问题。多数情况下,管路内的脉动特 性在系统安装完成之前是不能计算出的。 缓冲器是依据管道内的压力和液流的评 价准则来选取的。在某些情况下,通过安装很多装置使系统运行平稳,安装得以 认可。然而,这些安装在管路中的装置确承受着剧烈的振动,管道和附件的失效 及吸气主管内的气穴现象等使管路的可靠性较低。 这些问题的产生是由于在选择 缓冲器的时候没有考虑到系统的声学特性所造成的。

The effects of several different types of accumulators in a three pump parallel system were studied using a digital computer program which models the pulsation characteristics of pump and compressor systems.Detailed computer analyses were performed on bladder gas charges appendage and flow-through accumulators,the non-bladder,flow-through,gas-charges accumulators,and all-liquid Helmholtz filters.These results indicate that the off-the-shelf accumulators can be effective in some cases,but can combine with the particular acoustical characteristics of the system to amplify pulsations in other cases,In addition,the interaction between the individual pumps in a parallel installation can cause severe amplification of the pulsations.Guidelines are presented for the selection of pulsation filters for pump systems and the type of analyses that should be performed in the design stage. 本文研究了三台柱塞泵并机系统中几种不同规格的缓冲器的效果, 研究工作 是由对泵和压缩机系统的脉动特性进行建模的计算机程序完成的。 计算机详细地 分析了充满气泡、有流体通过的缓冲器,没有气泡、有气体通过的缓冲器,和全 液体的亥姆赫兹滤波器。 这些结果表明在某些情况下现成的缓冲器是有效的,但 是在另外一些情况下与特殊的系统的声学特性结合起来会放大脉动。此外,在并 机运行的系统中单台泵之间的相互作用会很大程度上增强脉动。 这些结果可以指 导泵系统的脉动过滤器的选择,并且在设计阶段得以应用。 INTRODUCTION Many reciprocating pump installations suffer problems that cause increased maintenance and unreliable operation . Typical problems encountered are high vibrations of the piping and pump and/or failures in the piping,valves,crossheads, connecting rods,crankshafts,and working barrels.Many of these problems can be caused by high pulsation levels. 引言 许多往复泵装置出现的问题是由于不可靠地维护和运行所造成的。所遇到的 典型的问题是泵和管道的剧烈振动,以及管道、阀门、十字结联轴、活塞连杆、 曲轴、工作缸的故障。其中许多是由高的脉动水平引起的。 High pulsations are caused by the interaction of the excitation energy from the pump with the acoustical natural frequencies of the system.The pump and its suction and discharge piping system form a complex acoustical system and will have numerous acoustical natural frequencies. reciprocating pump generates pulsations at A integer multiples of the pump speed.However,outside of the pump manifold the harmonics with significant energy content will generally be at the plunger frequency and its multiples. 高水平的脉动值是由于泵的激发能量与系统的固有声学频率相互作用引起 的。泵和吸液、排液管道构成一个具有众多固有声学频率的复杂系统。一个往复 泵产生脉动量的频率是其转速及整数倍,然而,在泵的主管线以外,包含大量能 量的谐波一般是活塞运动频率的整数倍。

Vibration of the piping and pump is caused by pulsation-induced shaking forces which are a function of the pulsation amplitude and the flow area of the piping.Whenever there is a coincidence of the excitation harmonics with the acoustical natural frequencies of the system, amplification of the pulsations occur and excessive vibrations can be induced.Amplification factors are typically 10-40 for pulsation resonances and 10-20 for mechanical resonances . If the mechanical resonance coincides with an acoustical resonance, a combined amplification factor of 800 could occur.

管道和泵振动是由脉动诱发的激振力引起的, 该力为脉动幅度和管道的通流 面积的函数。 每当激励谐波与该系统的声学固有频率相重合时,脉动值将增大并 诱发剧烈管路振动。脉动产生共振时放大系数通常是 10-40,而机械共振的放大 倍数通常 10-20。 如果机械共振和声共振重合, 它们联合的放大系数可能达到 800. Many pump systems are designed without consideration of the system acoustical pulsation characteristics and no accumulators or acoustical filters are installed. These systems can encounter severe vibrations and failure problems immediately after startup. When excessive vibrations and failures occur, the piping system is typically modified by the addition of accumulators to reduce the pulsations. The accumulator is generally chosen on the basis of the system pressure and the flow rate; however, this may not be sufficient. Hence, accumulator is sometimes successful in reducing the the pulsations and other times it is not. When the selected accumulator does not reduce the pulsations, another brand or type is selected and it may or may not work properly. 许多泵的系统在设计时并未考虑系统的声学脉动特性, 也没有安装缓冲器或声 学滤波器。 这些系统在启动后立刻就会遇到强烈的振动和出现故障。当有过度的 振动和出现失效时, 典型的整改方式是在管道系统中增加缓冲器来减少脉动。缓 冲器一般是基于系统的压力和流量来选取的,但这还不够。所以,缓冲器有时能 够减少脉动,而有时则不能。当所选的缓冲器不能减少脉动时,将选择另一类型 的缓冲器这有可能起到作用也许无效。 It is possible to calculate the effectiveness of any given accumulator in the design stage or for a modification to an existing installation [1,2]. Using a digital computer model which has this capability, the pulsations at any point in a piping system can be predicted. This allows the engineer to design the piping system to minimize the pulsations and the shaking forces. 在设计阶段对任何给定缓冲器及装置中已有缓冲器的修改的有效性进行计 算是可行的[1,2]。使用数字化计算机模型能够预测出管道系统中任意一点的脉 动。这使得工程师可以设计管道系统使脉动和振动力减至最低。

It is difficult to predict the exact effects of accumulators on the pulsation response of systems without a means of analysis, such as the computer program mentioned above. A parametric analysis of a typical system showing the effects of different types of accumulators can provide insight into the system characteristics. This paper will discuss the results of an acoustic analysis of a reciprocating triplex pump system with various accumulators. The pump system studied has three pumps operating in parallel. The effects of the accumulators on the discharge system will be discussed; however, the understanding of the acoustical effects will also be applicable to the suction system. 在没有如上述计算机程序的分析方法时, 系统的脉动响应的精确效果是难以 预测的。 一个能显示出不同种类的缓冲器的效果的典型系统的参数分析使我们对 系统特性有所了解。 本文将讨论含有各种缓冲器的三柱塞往复泵的声学分析。所 研究的泵系统有三台泵并机运行。 我们将对在排出管系中缓冲器的效果进行讨论; 然而,对声学效果的认识也适用于吸入管系。 In order to understand how the accumulator affects the acoustical characteristics of the system, it is necessary to understand how an acoustical wave is propagated. Acoustic pulsations travel at speed of sound in the fluid which, for most liquids, is from 3000 to 5000 feet per second. For the normal frequency range of pump pulsations, it is possible to use plane wave acoustic theory to describe the acoustical standing wave patterns since the pipe diameters are small compared to the wave length of the acoustic wave. The wave length of an acoustical wave is the speed of sound divided by the frequency. The frequencies of interest in pump installations are generally less than 300 Hz. Therefore, the wave lengths are greater than 10 feet. Low frequency harmonics which have the highest energy have wave lengths of 100 feet or more. The acoustical properties of systems having piping with diameters of less than 10 feet can therefore be accurately calculated using plane wave theory. 为了理解缓冲器对系统声学特性的影响,就必须了解声波是如何传播的。声 学 脉 动 在 大 多 数 液 体 内 的 传 播 速 度 可 以 达 到 3000-5000 英 尺 每 秒 (914-1524m/s)。因为管径和声波波长相比很小,所以对于泵的正常脉动频率, 可以使用声学平面波动理论来描述声学驻波的模型。 声波的波长等于声速除以频 率。和泵装置有关的频率一般不超过 300Hz。因此波长大于 10 英尺(3.048m)。 具有高能量的低频谐波的波长大于 100 英尺(30.48m)。 因此利用平面波理论可以 精确的计算出管径不到 10 英尺(3.048m)的管道系统的声学特性。 One important facet of the problem is the relationship between the acoustic speed of sound and the flow velocity of the fluid. The pulsations (acoustic waves) generated from the pump travel with a velocity of 3000-5000 feet per second and typical flow velocities are less than 50 feet per second. Thus the flow velocity will have little or no effect on the acoustical characteristics of the system. The flow velocity can be neglected and the understanding of the effects of the accumulator based on the acoustic wave alone.

问题的一个重要方面是声速和液体流速之间的关系。泵运行产生速度为 3000-5000 英尺每秒的脉动(声波)和小于 50 英尺每秒(15.24m/s)的液流。因 此流速很少或不会对系统的声学特性产生影响。流速可以忽略,可以单独基于声 波来了解缓冲器的效果。 TYPES OF ACCUMULATORS There are several different types of accumulators and acoustical filters which are used to control pulsations in pump systems. Miller [3] described over 30 different kinds, although from an acoustic standpoint, the devices can be divided into the following categories: 1. Appendage accumulator with gas-filed bladder or diaphragm 2. Appendage accumulator with diverter and gas-filed bladder or diaphragm 3. Flow-through accumulator with gas-filed bladder/ diaphragm or gas blanket 4. Resistive accumulator (pressure drop) devices 5. Acoustical filters (Helmholtz type) The acoustical characteristics and the effects of the various types of accumulator on pulsations will be discussed. 缓冲器的种类 在泵系统中用来控制脉动的缓冲器和声学滤波器有若干种不同类型。 Miller[3]描述了 30 多种不同的类型,但是从声学角度来看,这些设备可以划分 为以下类型: 1. 2. 3. 4. 5. 带有气囊或者隔膜的依附型缓冲器 带有分流器和气囊或者隔膜的依附型缓冲器 带有气囊/隔膜或者气层的有液流通过的缓冲器 阻式缓冲器(降压) 声学滤波器(亥姆赫兹型)

下面将讨论不同种类缓冲器的声学特性和对脉动的影响。 Appendage with Gas-Filled Bladder Accumulators that are mounted on the piping through a tee type installation are called appendage or side branch accumulators. Figure I show sketches of the different accumulators. The gas-filled bladder or diaphragm is separated from the flow by a throat or neck from the pipe flow and a volume of liquid beneath the elastic member (Figure 1a and 1b).

带有气囊的依附型缓冲器 安装在管道上通过 T 字形装置的缓冲器被称为附属或旁路缓冲器。 1 显示 图 了不同种类的缓冲器。 气囊或隔膜由颈管或接管与管中液流及弹性部分之下的液 体分开(图 1a 和 1b) 。

(a )

(b)

(c)



BLADER ACCUMULATOR 囊状缓冲器 (d )

DIAPHRAGM ACCUMULATOR 隔膜缓冲器

GAS CHARGED ACCUMULATOR 充气缓冲器

(e)

(f)

DIAPHRAGM ACCUMULATOR WITH ELBOW-TEE 带有 T 形弯头 的隔膜缓冲器

BLADDER ACCUMULATOR WITH DIVERTER

IN-LINE ACCUMULATOR

带有分流器的 囊状缓冲器

内嵌式 缓冲器

(g)

(h)

FLOW THROUGH ACCUMULOTOR WITH BLADDER 有流体通过并带 有气囊的缓冲器 (i)

RESISTIVE

ACCUMULTOR

阻式缓冲器

(j)

ALL-LIQUID ACOUSTIC FILTER VOLUME-CHOKE

ALL-LIQUID ACOUSTIC FILTER VOLUME-CHOKE-VOLUME 全液式双筒节流滤声器

全液式单筒节流滤声器

Acoustically, the appendage accumulator consists of a throat or neck, equivalent to a short length of small diameter pipe,a volume of liquid in contact with the bladder or diaphragm, the elastic spring and mass properties of bladder or diaphragm,and the compliance of the gas volume confined in the bladder. Note that acoustically the bladder and the diaphragm accumulators are identical, in so far as the influence on the acoustical response is concerned. Accumulators are quite effective in many installations since the compliance of the gas above the bladder/diaphragm is equivalent to a large liquid volume.The equivalent liquid volume of a gas volume can be obtained by multiplying the gas volume by the ratio of the liquid to gas density and the speed of sound squared. For many liquid systems, this ratio is near 10000. Therefore a small gas volume can be equivalent to a large liquid surge volume. Due to the geometry of the accumulators(e. g. the throat or neck) these devices are usually more effective at low frequencies than at high frequencies. 在声学上,依附型缓冲器的颈部等同于一小段小径管、和气囊或隔膜有关的 液流、气囊或隔膜的弹性部件及其通性、气囊中可变气体体积。特别注意声学上 气囊缓冲器和隔膜缓冲器是一样的,只是要注意声学响应的影响。因为气囊/隔 膜里面的可变气体等同于很大的液体体积,所以在很多装置中缓冲器是很有效 的。和气体体积对应的液体体积等于气体的体积乘以液体密度对气体密度的比 值,再乘以声速的平方。对于很多液体系统,这个比值接近 10000.因此很小的 气体体积可以转化为大量液体的体积。由于缓冲器的几何结构(例如其颈部) , 这些设备在低频时比在高频时更有效。 A mechanical (electrical) analogy can be derived to help understand the dynamics of accumulators. The throat acts as a mass(inductance) and the volume acts as a spring (capacitor) to provide a resonance frequency. Above this frequency the accumulator will lose much of its effectiveness. For most accumulator designs, this acoustic natural frequency will be less than 100 Hz. 可以引入机械(电)方面类似的东西来帮助理解缓冲器动态。颈部就像质量 (自感) ,容积就像弹簧(电容) ,从而引起共振。超过了这个频率,缓冲器的效 果就会大大减弱。 对于多数缓冲器的设计, 这种声学的固有频率不能超过 100Hz。 The effective liquid volume is very sensitive to the gas volume, since it multiplied by approximately 10000.Therefore, the gas volume must be constantly checked to ensure that the accumulator is properly charged. Although recommendations vary between manufacturers, a general rule of thumb is that the bladder/ diaphragm is charged to 50 percent to 70 percent of the line pressure. The gas is typically injected into the bladder while the system is depressed. However, when the system is pressurized the gas volume will be reduced. 对于气体体积来说, 起作用的液体体积是很灵敏的,这是因为它要乘以一个 接近 10000 的数。因此必须经常检查气体的体积,以保证缓冲器的正常工作。尽 管不同厂商有不同的建议,但是根据一般经验,气囊/隔膜的压强要保持在压强

线的 50%~70%之间。通常在系统没有压强的时候充入气体;但是当系统增压时, 气体的体积会缩小。 The effective gas volume changes with the steady-state line pressure. Mechanical constraints that support the bladder can interfere with the bladder, causing it to become ineffective. The mass and stiffness properties of the bladder can also influence the acoustical characteristics of the accumulator. 实际的气体体积是随着稳定的压力线变化的。 机械的约束导致气囊妨碍其他 气囊,使其失效。气囊的质量和刚度特性也能影响缓冲器的声学特性。 Appendage With Gas-Filled Bladder And Diverter Accumulator manufacturers have recognized that the appendage type devices have limited frequency response capabilities and have experimentally determined that improved high frequency attenuation could be achieved by the use of a diverter which, according to the sales literature, causes the steady state flow to be "diverted" directly into the accumulator, thus improving the attenuation characteristics at the higher frequencies (Figure 1e). Experimental data has been collected to verify the claims [3]. 带有充气气囊和分流器的附属 缓冲器厂家已经认识到依附型设备限制了频率响应能力, 实验显示了使用分 流器能够改善高频衰减,通过说明书可以了解分流器正好将稳态流“分流”到缓 冲器中,从而改善高频的衰减特性(图 1e) 。收集到的实验数据证实了这个论断 [3]。 The authors believe that the improved attenuation of the diverter type appendage accumulators is due to a different acoustical phenomenon and is not related to the diverting of the steady state flow into the accumulator. As discussed earlier, the acoustic wave travels at the speed of sound which is approximately 100 times the flow velocity, thus the effect of the flow velocity is negligible. The additional attenuation of the diverter accumulator is a function of the additional pressure drop of the diverter and the flow velocity vector does not significantly affect the results. Some additional turbulence may be created by the swirling but its primary influence is in the pressure drop. 作者认为对带有分流器的依附型缓冲器衰减的改进, 是由不同的声学现象而 不是相关的转入缓冲器中的稳态流所决定的。正如前面所讨论的,声波的传播速 度是流速的 100 多倍, 所以流速的影响可以忽略不计。带有分流器的缓冲器的额 外衰减是分流器额外压降的函数,而流速对结果没有明显的影响。涡流会引起一 些额外的紊流,但它的主要影响还是在压降方面。

Therefore, to model the diverter, an acoustical resistive element is added to the accumulator system model (Table 1). The acoustical analyses will show that the diverter does improve the acoustical attenuation at specific frequencies, but is accomplished by the pressure drop (damping) and not for the reasons normally presented in some of the sales literature. 因此,为了建立分流器的模型,在缓冲器系统模型中增加一个声阻部件(表 1) 。声学分析表明分流器确实能够改善声学特定频率的衰减,但这是由压降(阻 尼)完成的,而不是通常说明书上提到的原因。

Table 1: Analogies of Dynamic System Components

Mechanical Mass Spring Dashpot

Electrical Inductor Capacitor Resistor

Acoustical Choke Volume ΔP

表 1:类似的动态系统构成要素

机械 质量 弹簧 减震器

电学 感应器 电容 电阻

声学 阻风门 气容 阻力损失

Some appendage accumulator manufacturers recommend that their accumulator be installed in the discharge system with an elbow and tee arrangement such that the steady state flow vector is directly into the appendage accumulator (Figure 1d). This configuration has been tested by the manufacturer and, under certain conditions, was shown to have increased attenuation. Improvements in attenuation obtained by this configuration are attributable to additional pressure drop at the elbow and the tee and not due to the direction of the flow vector. Experimental data may show that, at some speeds, the attenuation is increased; however, this design is undesirable since the addition of the elbow and tee introduces two additional shaking forces in the system [4]. Good design practices would eliminate all unnecessary bends in the piping system.

一些依附型缓冲器厂商建议他们的缓冲器要通过弯头和 T 形接口安装在排 出管系中,这样稳态流直接进入到依附型缓冲器中(图 1d) 。厂商对这装置进行 了测试,结果表明在一定条件下增加了衰减。这种构造使得衰减方面有改进,这 是由于在弯头和 T 形接口处存在额外压降,而不是液流的方向。实验数据可能显 示在某些速度时衰减增加; 但是这种设计是不可取的,因为增加的弯头和 T 形接 口会使系统增加两个额外的振动力[4]。好的设计方案能够消除管道系统中不必 要的弯管。 Flow-Through The appendage type of accumulator attenuates pulsations, but is limited in its frequency response due to the effect of the throat.Improvements in the acoustic attenuation of accumulators can be achieved by the elimination of the throat. By using a flow-through filter with a gas-filled bladder/ diaphragm or using a gas blanket over the liquid without a separating membrane (Figures If and Ig), the throat effects can be minimized and a broader frequency range of attenuation can be obtained. 流通式 依附型的缓冲器减弱了脉动,但是颈部的影响限制了它的频率响应。除去颈 部能很好的实现缓冲器中声衰减的改进。通过使用带有气囊/隔膜的流通式分流 器或是与液体之间无膜的液体上的气层(图 1f 和 1g) ,颈部的影响将最小化, 并得到较大范围频率的衰减。 One disadvantage of the gas blanket design (Figure 1c) is that the gas may be absorbed by the liquid and constant maintenance must be expended to ensure that the accumulator is properly charged. This is also a disadvantage of the gas-filled bladder/ diaphragm accumulator since the gas charge must be checked periodically. 气层设计(图 1c)的一个缺点是气会被液体吸收并且经常维护以确保缓冲 器的正常运行。 因为气充必须经常检查,所以这也是一个气囊/隔膜的不便之处。 Resistive (Pressure Drop) Devices In addition to the accumulators discussed above, resistive devices are used to attenuate pulsations in some piping systems. These accumulators typically will have small volumes, such as a small sphere;however, the major acoustical attenuation is achieved by forcing the flow through small diameter pipes which causes considerable pressure drop (Figure 1h). These devices can be effective for certain system modes (usually high frequency). Some sales literature claim a phenomenon called the fluid flywheel effect which is dependent upon the direction of the fluid flow. Again the velocity of the acoustic wave is so large compared to the steady state velocity that this effect is nearly non-existent, except for increased turbulent pressure drop.

阻式(降压)设备 除了上面所讨论的缓冲器, 阻式设备在一些管道系统中用来减弱脉动。这些 缓冲器具有很小的体积, 就像一个很小的球一样;但是主要的声学衰减是通过液 流经过细径管道而引起压强下降来完成的(图 1h) 。这些设备能有效地确定系统 的模型(通常是高频) 。一些说明书声称液体飞轮效应取决于液流的方向。再说 声波的速度和稳态速度相比是如此之大所以这种效应是几乎不存在的, 除了增加 湍流压降。 Orifices and restriction perforations are also used to achieve attenuation of pulsations and can be quite effective if they are properly placed. Resistive type elements generally work best when they are installed at locations of maximum acoustic particle velocity (at acoustical standing wave pressure nodes). 口和限制孔也可以用来完成脉动的衰减,如果它们的位置很合适就会很有 效。当阻式部件安装在最大声学质点速度的位置时(在声学驻波压力节点) ,它 们能很好的工作。

Acoustical Filters (Helmholtz Type) Acoustical reactive filters (Figures 1i and 1j) which are based upon low pass filter theory have been successfully used for many years. With the improvements in the acoustical modeling capabilities for pump systems, such filters can be optimized to achieve the maximum attenuation with a minimun of pressure drop [1]. The analogous relationship between low pass filters in electrical circuits and piping acoustics was discussed by Ludwig [5] and Hicks [6]. As summarized in Table 1, the liquid volume is analogous to a capacitor and the choke tube is analogous to an inductance. The filter design is based upon the acoustic natural frequency (commonly called the Helmholtz frequency) of the choke tube and the volume. The Helmholtz frequency is usually set at one-half the plunger frequency and the bottle and choke sizes are determined from the allowable pressure drop. 声学滤波器(亥姆霍兹型) 声学反应滤波器(图 1i 和 1j)是以成功运用很多年的低通滤波器理论为基 础的。 随着泵系统的声学模型特性的改善,这些滤波器可以实现以最小的压降达 到最大的衰减[1]。Ludwig[5]和 Hicks[6]讨论了低通滤波器和管道声学之间的 相似关系。正如表 1 总结的那样,液体体积相似于电容,阻风门相似于感应器。 滤波器的设计基于阻气管和其容积的声学固有频率(俗称亥姆霍兹频率) 。亥姆 霍兹频率通常设定为柱塞频率的一半,瓶体和阻风门是由适当的压降所决定的。

Acoustic filters (commonly called all-liquid filters since there is no need for gas volumes) can be designed with a choke tube and either one or two volumes. The added volume increases the Helmholtz natural frequency, but increases the attenuation as a function of frequency. 声学滤波器(俗称全液式滤波器,这是因为不需要气体)可以用一个阻气管 和一个或两个桶。增加的桶能加大亥姆霍兹固有频率,但也增加了频率的衰减。 SYSTEM EFFECTS

Most pulsation problems are caused by a system problem caused by the complex acoustical system consisting of the pump and piping.If no accumulator or filter is in the system, the system will have numerous acoustic natural frequencies and mode shapes. If an accumulator or filter is introduced into the system, there will be a new set of acoustical natural frequencies and mode shapes. Depending on the location of the acoustic resonances and the plunger frequencies,the system may or may not have problems. This is one of the main reasons that a particular type or brand of accumulator will work in one system and not in another. 系统影响 大多数脉动问题是由系统问题引起的, 而系统问题是因为由泵和管道组成的 复杂声学系统引起的。 如果系统中没有缓冲器或是滤波器,该系统就会有许多声 学固有频率和振型。 如果把缓冲器或是滤波器引入该系统,将会出现新的声学固 有频率和振型。根据声共振的位置和柱塞的频率,系统可能有或可能没有问题。 这是一个特定类型或品牌的缓冲器可以在一个系统中工作而不能在另一个系统 中工作的主要原因之一。 When an accumulator or filter is installed near the discharge or suction flange, an acoustical quarter-wave natural frequency is introduced. This quarter-wave mode has the maximum pulsation amplitude at the closed end of the pump manifold and a minimum pulsation amplitude at the entrance to the accumulator. An estimate of this acoustical natural frequency can be made using a simplified system which employs a constant diameter pipe from the end of the manifold to the entrance of the accumulator. The natural frequency would be equal to the speed of sound divided by 4 times the length from the end of the manifold to the entrance of the accumulator.This frequency, generally from 50-300 Hz, has been described by some investigators as an acceleration head frequency [3].

当一个缓冲器或是滤波器安装在排除或吸入法兰附近时,会引入一个 1/4 声波固有频率。 这个 1/4 波形在泵管系的闭端有最大的脉动振幅,而在缓冲器的 入口处有最小的脉动振幅。 这个声学固有频率的估算是通过使用缓冲器入口处主 管带有的一个恒径管的简单系统来实现的。 该固有频率等于声速除以主管尾端到 缓冲器入口处距离的 4 倍。这个通常是 50-100Hz 的频率,通过一些调查被描述 为加速头频率。 The acceleration head concept used on the suction system to calculate the required net positive suction head is an attempt to explain pulsations by a static phenomenon and is not needed if an accurate model of the pump and piping is used to predict the pulsations. If accumulators are used on the suction and discharge systems, each will have a resonant quarter-wave acoustical natural frequency determined by the acoustical length from the end of the manifold to the entrance of the accumulator and is not related to the acceleration head. 在吸入系统中用来估算最后吸头的加速头概念是通过一个恒定现象解释脉 动的尝试,如果一个泵和管系的精确模型用来预测脉动,那么它就不需要了。如 果缓冲器用在吸入和排出系统上, 这两个系统会有一个 1/4 波长声学固有频率的 共振, 它是由主管的尾端到缓冲器的入口处的声学距离所决定的,而和加速头没 有关系。 The quarter-wave mode resonances will normally be excited by the higher plunger harmonics and cause high pulsations in the suction and discharge manifolds. High pulsations in the suction manifold can cause cavitation since the negative peak of the pulsations subtract from the steady state pressure. If the instantaneous pressure drops below the fluid vapor pressure, cavitation occurs. Cavitation in the suction system and high pulsations in the discharge manifold can cause failures of valves, crossheads, connecting rods, the crankshaft,and bearings. As discussed by Wachel [1], this mode can be controlled through the use of an orifice at the pump flange or at the entrance to the accumulator. 1/4 波长共振振型通常是由较高的柱塞谐波激发的,并会在吸入和排出主管 处引起高脉动。 在吸入主管处的高脉动能带来气穴现象是因为稳态流压强减去脉 动的负峰值。如果压强瞬间降到液体蒸汽压强下,就会发生气穴现象。吸入系统 的气穴现象和排出主管的高脉动会引起阀门、 丁字头、 连杆、 曲轴和轴承的故障。 正如 wachel[1]讨论的,这个振型可以通过在泵法兰或缓冲器的入口处使用孔来 控制。 ANALYSIS OF A TYPICAL SYSTEM To evaluate the performance of various design configurations of pulsation accumulators, a simple piping system was analyzed with several accumulator designs, and with acoustic filters. Failures of the accumulators (bladder ruptures, over or under pressures, etc.) were also simulated.

一个典型系统的分析 评估脉动缓冲器的各种设计配置的工作情况, 一个简单管道系统由几个缓冲 器的设计和声学滤波器来分析。 缓冲器的故障 (气囊破裂、 超过或低于压强等等) 也能模仿。 Piping System Description The pump piping system, shown in Figure 2 , is typical of many pump facilities and consists of three triplex reciprocating pumps operating in parallel. The pumps are piped into a common header,which continues with a single line into the pipeline. The upper-case letters at various points in Figure 2 indicate points where system pulsations were computed. For the purposes of this paper, only the test points relevant to the particular point being emphasized will be shown. In addition, the discharge side of this system was considered to be independent of the suction system.2 管道系统的描述 在图 2 中的泵管道系统是很多管道设备和三缸往复泵的典型代表。 泵由管道 连接到母管中, 该母管的管线中保持单行线。图 2 中各点的大写字母显示了系统 脉动计算出的位置。 因为本文的目的,只有和测试点有特定关系的点才能特别显 示。此外,这个系统排出的一边是认为独立于吸入系统的。2

Fig.2

Typical Pump/Piping Discharge System

图 2 典型泵/管道排出系统 Each of the pumps have 3.5 inch diameter plungers and a stroke of 5 inches, and operates at a constant speed of 308 rpm. The total output from each pump is 192 gpm of water at 1000 psia. The speed of sound in pure water at operating temperature is 4860 feet per second. To account for variations in water purity and temperature,the pulsation calculations were made for a ± 15% variation in speed of sound. For clarity, this variation appears on the pulsation plots as a variation in pump operating speed. 每个泵有 3.5 英寸直径的柱塞和 5 英寸的冲程, 并有 308 转/分的恒定转速。 每个泵的输出为 192 加仑/分的水和 1000 磅/平方英寸的压强。处在工作温度时 声音在纯净水中的速度为 4860 英尺/秒。为了说明水纯度和温度的变化,脉动的 计算是由声速变化的±15%得来的。为了说明起见,这个变化正如泵运行速度的 变化一样出现在脉动点。

The results of the acoustic analysis of the piping system with no acoustic treatment are shown in Figure 3. The vertical axis of each plot is independently scaled so that the frequency of the acoustical resonances can be noted. Several acoustic modes are present in the system that cause resonant pulsation levels of 15-30 psi peak to peak. Significant "cross-talk" is also apparent. Cross-talk is caused by acoustic modes that involve more than a single pump, and therefore can transmit energy from one pump to another. The complex pressure waves at most locations in the piping can have peak to peak (p-p) modulations as great as 60 psi, and can be 100 psi at the pump plunger face. A 6 inch pipe in this system could experience shaking forces of 1700 pounds, peak to peak. The necessary pipe clamps required to hold these force levels would be substantial. 没有经过声学处理的管道系统的声学分析结果如图 3 所示。每幅图的纵轴 有独立的刻度, 因此可以得到声学共振的频率。目前在系统中的几个声学模型引 起峰值为 15-30 磅/平方英寸的共振脉动。大量的“串扰”也是清晰可见的。串 扰是由包含多于一个泵的声学模型引起的, 因此可以从一个泵传输能量到另一个 泵。 复合的压强波在管道中的大多数位置有 60 磅/平方英寸这么大的峰值,而在 泵柱塞面则有 100 磅/平方英寸。 这个系统的 6 英寸管道经历 1700 磅峰值的振动 力。必要的管道要固定住就需要保持压强值的恒定。

VERTICAL SCALE PSI (P-P)

HORIZONTAL SCALE

FREOUENCY(Hz)

Fig.3

No Pulsation Treatment

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图 3 无脉动分析

VERTICAL SCALE PSI (P-P)

HORIZONTAL SCALE

FREOUENCY(Hz)

Fig.4

Tee Installation

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图4

T 形装置

By adding a pulsation accumulator device, these pulsations and shaking forces can be reduced to more reasonable levels. The job of the piping designer is to choose a device that will adequately protect the piping and the pump. As will be shown, selection of a device without regard to the system acoustics and all operational parameters can result in a system that is worse than if no pulsation dampener was used. 通过增加脉动缓冲器装置,这些脉动和振动力会降低到一个合适的水平。 管道设计的工作是选择一个能够充分保护管道和泵的设备。 以下将说明设备的选 择如果不考虑系统的声学特性和运行参数,那么系统还不如不使用脉动阻尼器。 Investigation of Accumulator Design This study will begin with the appendage accumulators and their derivatives. Several different configurations will be studied to investigate the design limitations of each, as well as the acoustical phenomenon responsible for their operation. Flow-through devices will be investigated, followed by resistive devices. Finally, acoustic filters(sometimes called all-liquid filters) will be investigated.

缓冲器设计的研究 这项研究由附属缓冲器及其衍生物开始。我们将研究几中不同装置的设计极 限以及它们运行时的声学现象。 首先研究的是由液流通过的设备,其次是阻尼设 备。最后研究的是声学滤波器(有时候也称之为全液式滤波器) 。 Appendage Accumulators The acoustic elements of a typical appendage accumulator consist of a gas volume, a liquid volume,and one or more "neck" elements. The major acoustic effect is due to the gas volume which is typically confined in a bladder or diaphragm. Since the compliance of the gas (a measure of its softness)is roughly 10000 times greater than the compliance of the liquid, the additional liquid volume in the accumulator has little effect on the system acoustic natural frequencies and mode shapes. The throat area provides some inductance and consequently has a large effect on the performance of the accumulator. 附属缓冲器 一个典型附属缓冲器的声学成分包括气体容积、液体容积和一 个或多个“颈部”成分。主要的声学效应是因气囊或隔膜里受限的气体容积而产 生的。因为气体的可塑性(它柔软性的度量)大约是液体可塑性的 10000 倍,所 以缓冲器中额外的液体对系统声学固有频率和振型的影响很小。 颈部区域有一些 自感,因此对缓冲器的性能有很大的影响。

The discharge system was analyzed with a bladder type appendage accumulator at each pump. The accumulators were installed using a pipe tee, as close to the discharge flange as possible(within one foot). The calculated pulsation levels at the plunger face, lateral and header piping are shown in Figure 4.Overall pulsation levels in the piping have been significantly reduced. (Note that the vertical scale is 5 psi full scale.) However, pulsations levels at the pump plunger face were only slightly reduced, due primarily to the creation of an acoustic quarter-wave resonant mode at 190 Hz between the closed end of the pump manifold and the accumulator.Note that system pulsation levels at low frequency have been reduced; however, some new high frequency modes have been created.The inductance of the accumulator neck combines with the compliance of the gas volume to reduce the effectiveness of the appendage accumulators at high frequency. 分析带有一个气囊型附属缓冲器的泵的排出系统。 该缓冲器是用管系来安装 的,尽量接近排出法兰(不超过 1 英尺) 。柱塞正面、侧面和上面计算出来的脉 动值如图 4 所示。总体来说管道中的脉动值有了明显的减少。 (请注意纵坐标的 总标度是 5 磅/平方英寸) 。但是,泵柱塞正面的脉动值只略微减少了一点点,这 主要是因为泵主管的闭端和缓冲器之间产生了一个频率为 190Hz 的 1/4 声学共振 波。我们注意到在低频时系统的脉动值有所减少;但是,一些新的高频模态产生 了。 缓冲器颈部的自感和气体容积的可塑性相结合,可以降低高频时附属缓冲器 的效果。

A general “good design” practice is to locate the accumulator as closely as possible to the pump discharge flange. As the distance between the end of the pump manifold and the accumulator increases,the “manifold resonance” frequency (quarter-wave) decreases. The higher energy content of the lower orders of pump speed will create a higher amplitude response at this resonance3. Since the manifold resonance has a pressure node at the accumulator, it can be controlled effectively with the additions of some damping at the accumulator. 通过“好的设计”的做法是找出尽可能靠近泵排出系统法兰的缓冲器。随着 泵主管尾端和缓冲器之间距离的增加, “管道共振”的频率(1/4 波)会下降。 包含低阶泵速的高能量会在这个共振上引起更高幅度的共振 3。因为管道共振在 缓冲器上有压强节点,所以它能由缓冲器上增加的一些衰减来有效地控制。 Table 1 indicates that acoustic damping can be obtained with a pressure drop. Orifice plates are an effective means for introducing a pressure drop. They are also inexpensive to produce and can be easily added to systems in the design phase or after completion. Therefore,a five psi pressure drop orifice was simulated in the system model at the discharge flange of the pump. The amplitude of the response at the manifold resonance was reduced by 25%.Pulsation levels elsewhere in the system remained essentially constant (Figure 5). 表 1 表明声学衰减可由压降获得。孔板是引入压降的有效手段。此外它们能 够便宜地制造出来, 并且在设计阶段或结束以后能很容易地加入到系统中来。因 此,一个压降为 5 磅/平方英寸的孔模拟在系统模型泵的排出法兰上。管道共振 的振幅减少了 25%。脉动数值在系统中的其他地方依然保持不变。 (图 5) 。 Devices, such as a diverter plate, that introduce pressure drop at the accumulator (Figure le) , also reduce resonant pulsation levels in the manifold. Introducing bends (elbow and tee) in the piping upstream of the accumulator will also provide some pressure drop(Figure 1d). An analysis of such an installation showed that the added pipe length between the pump and the accumulator decreased the frequency of the quarter wave resonance from 190 Hz to 155 Hz.The higher pulsation energies present at lower frequency tended to offset the damping effect from the pressure drop, and the peak calculated pulsation amplitude at the quarter wave resonance increased from 12 to 17 psi p-p. The analyses showed that while some improvements can be obtained at certain pump speeds (the quarter wave resonance may move so that the excitation frequency is on the flank of the resonance, and not the peak) pulsation levels in general will be higher (Figure 6). The results obtained with a straight section of pipe, an orifice plate at the flange, and the accumulator as presented in Figure 4 gave lower pulsations.

例如转向板的设备,在缓冲器中引入压降(图 1e) ,也能降低主管中的脉动 共振强度。 在缓冲器的上游管道引入弯管 (弯头和 T 形管) 也能提供一些压降 (图 1d) 。这样一个装置的分析表明在泵和缓冲器之间增加的管道将共振波的频率从 190Hz 减少到 155Hz。 低频时较高的脉动能量会从压降中抵消阻尼效果, 并且 1/4 波共振的脉动峰值从 12 磅/平方英寸增加到 17 磅/平方英寸。 分析表明某些泵速 得到了一些改善(1/4 波共振会变化,所以激励频率在波腹,而不在波峰) ,而 脉动值一般来说会变高(图 6) 。结果是一段直管、法兰上的一个孔洞、图 4 所 示的缓冲器,会带来较低的脉动。 Effect of Gas-Filled Bladder Volume One disadvantage of appendage accumulators is that, if the bladder fails, the system is without pulsation control. Severe pulsations can result, causing pump and piping damage. Another potentially troublesome characteristic is that the effectiveness of the accumulator can be quite sensitive to changes in the gas volumes. As line pressures change,the volume of gas in the bladder changes, possibly altering system performance. In some cases, the system can be worse than if the accumulator were not present. To illustrate this point, the system was analyzed with a varying amount of gas volume in one of the accumulators . 气囊体积的影响 附属型缓冲器的一个缺点是如果气囊发生故障,系统就 不能对脉动进行控制。 一些脉动会造成泵和管道的损坏。另一个潜在麻烦的特点 是缓冲器的效果对气体体积的变化是很敏感的。随着压强线的变化,气囊中气体 的体积也发生变化,可能就会改变系统的特性。在某些情况下,系统还不如不安 装缓冲器。为了说明这一点,就要分析系统中缓冲器内气体体积的变化。

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE Fig.5 FREOUENCY(Hz)

With 5 psi Orifice

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图5

带有 5 磅/平方英寸的孔

VERTICAL SCALE PSI (P-P)

HORIZONTAL SCALE Fig.6

FREOUENCY(Hz)

Elbow-Tee Installation

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图6

T 形弯头装置

The normal gas volume for this accumulator is 231 in 3. The system was analyzed for gas volumes of 200, 100, 50, 25, 5 and 0 cubic inches and the results are given in Table 2. As the gas volume decreased, a low frequency acoustic mode below the plunger frequency increased. The mode was a function of the distance between the accumulators of the three pumps. As this acoustic mode frequency increased, it moved through the plunger frequency. The pulsation amplitudes due to the first 3 harmonics of plunger frequency (higher harmonics were not significantly affected) at the plunger face, lateral,and header are listed in Table 2 for various gas volumes. 这个缓冲器中正常的气体体积是 231 立方英寸。当气体的体积是 200、100、 50、25、5 和 0 立方英寸时,系统的分析结果如表所示。随着气体体积的减小, 一个低于柱塞频率的低频声学模态有所增强。 该模态是缓冲器和三柱塞泵之间距 离的函数。随着这个声学模态频率的增加,它超过了柱塞频率。由在柱塞正面、 侧面、 上面前 3 次柱塞谐波决定的脉动振幅如表 2 所示,用来表示变化的气体体 积。 Table 2:Effects of Various Gas Volumes
Gas Volume Accumulator 1 (231 in 3) 0 231 200 100 50 25 5 0 0 231 231 231 231 231 231 231 Gas Volume Accumulators 2 & 3 Pulsations Test Point (psi p-p) Plunger Face 75 15 12 9 25 300 200 160 Lateral 40 5 4 5 25 275 190 150 Header 40 5 3 4 22 190 160 140

表 2:各种气体体积的效果
气体体积 缓冲器 1 (231 in 3) 0 231 200 100 50 25 5 0 0 231 231 231 231 231 231 231 气体体积 缓冲器 2 & 3 脉动测试点 (psi p-p) 柱塞正面 75 15 12 9 25 300 200 160 侧面 40 5 4 5 25 275 190 150 上面 40 5 3 4 22 190 160 140

When all the accumulators on all three pumps were equally charged and the gas volume reduced, the pulsations did not get any higher than the system without accumulators.
当三柱塞泵上的缓冲器有同样的变化, 并且气体体积减少时, 脉动不会比没有缓冲器的 系统高。

Appendage accumulators typically have a small diameter section Neck Area of pipe at their entrance. This narrow neck or throat area acoustically acts like a mass in mechanical spring-mass system to limit its high frequency response. The pressure drop associated with the neck will provide some damping. 颈部区域 在缓冲器的入口处通常会有一段小径管。这种狭窄的颈部区域 在声学上就像机械弹簧质量系统中的质量一样限制了它的高频响应。 与颈部有关 的压降会提供一些阻尼。 This effect was analyzed by changing the diameter of the neck(Figure 7). A comparison of the high frequency responses of the original system (Figure 4) with the accumulator to that in Figure 7 shows that the larger the diameter of the neck, the more effective the accumulator is in reducing the pulsations. 通过对颈部口径的改变来分析这种影响 (图 7) 初始系统的高频响应 。 (图 4) 和图 7 中缓冲器的比较显示了颈部口径越大,缓冲器对脉动的减少越有效果。

Flow-Through

Accumulators

An alternative design to appendage accumulators is the flow-through accumulator (Figure 1f and 1g).Their primary advantage is that they have no neck restriction. Some devices have additional liquid volume which can provide some pulsation control in case of a bladder failure. Flow-through accumulators (Figure 1g) are somewhat larger for a given gas volume than are the appendage accumulators and may be more expensive, depending upon the services.The bladder must be supported by various measures, such as cages,cans and internal cords.A comparison of the results of Figure 8 to Figure 4 shows that the pulsations transmitted to the lateral piping from the pump to the header are lower since the attenuation at the higher frequencies is improved. The flow-through accumulator has characteristics very similar to the appendage accumulator with no neck. 流通式缓冲器 另一种附属缓冲器的设计是流通式缓冲器(图 1f 和 1g) 。它们的主要优势 是没有管颈限制。 一些设备有额外的液体容积,这样能保证在气囊失效的情况下 还能控制脉动。流通式缓冲器(图 1g)比起附属缓冲器所给的气体容积稍微大 点,而且可能更贵,这取决于维护。气囊必须用各种措施来支持,例如保持架、 容器、 内部线。 8 和图 4 的对照结果显示从泵的侧管传播到顶端的脉动是低等 图 级的, 这是因为在较高频率的衰减有所改善。流通式缓冲器和无颈附属缓冲器有 非常相似的特性。

VERTICAL SCALE PSI (P-P)

HORIZONTAL SCALE FREOUENCY(Hz)

Fig.7

Neck Enlarged

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图7

管颈扩大式

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.8 Flow-Through

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图8

流通式

Resistance Devices Apart from orifice plate and other flow restriction devices is a class of pulsation accumulators that provide a large resistance and a small liquid volume(Figure 1h).These accumulator usually have so little volume that they can be considered almost entirely as resistance(damping). Therefore,they are most effective when placed at a dynamic pressure node(high dynamic particle velocity). 阻尼设备 除了孔板之外,还有其他的流量限制设备是一类提供大阻尼和小的液体体 积的脉动缓冲器(图 1h) 。这些缓冲器通常有很小的容积,它们几乎被认为是阻 力(阻尼) 。因此,当处于一个动态压强节点是,它们最有效(高动态质点速度) 。

Figure 9 shows the pulsations calculated for the system with a resistance device at the pump discharge flange. To illustrate the effect of the volume,compare the results of Figure 9 to Figure 10 with the volume removed from the model. A mode at 65 Hz,and another at 135 Hz are affected slightly. With the volume removed from the modle at 135Hz is only affected slightly. This behavior indicates that the majority of the attenuation effect is attributable to damping(pressure drop).Since these devices are usually installed at the pump flange,there are usually very few system acoustic acoustic modes that can be attenuated by these devices. The pulsations with this accumulator for the system are not significantly better than the system without treatment(Figure 3). 图 9 显示了在泵的排出法兰安装一个阻尼设备来计算设备的脉动。 为了说明 容积的影响,从模型中除去容积来比较,如图 9 和图 10 的结果。一种情况是在 65Hz,另一种在 135Hz,影响不大。从模型中把容积去掉,就只有在 135Hz 影响 不大。这种现象表明大部分的衰减作用是由阻尼(压降)引起的。由于这些设备 通常安装在泵法兰上, 所以只有极少的系统通过这些设备来使声学模型衰减。带 有这种缓冲器系统的脉动并没有显著优于未经处理的系统(Figure 3) 。

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.9 Resistance Device

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图9

阻尼设备

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.10 Resistance Device—No Volume

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

图 10 Acoustic Filters

阻尼设备—无体积

A properly designed acoustic filter is able to attenuate pulsation energy over a wide frequency range. Acoustic filters are relatively immune to changes in line pressure and once installed, require little, if any, maintenance. However, these filters are generally much larger in size and may have an initial cost higher than offthe-shelf accumulators.

声学滤波器 设计适当的声学滤波器在一个宽频范围内可以使脉动能量衰减。 声学滤波器 不受管线压力的影响,一旦声学滤波器安装好了,如果有必要的,只要很少的维 护。但是这些滤波器通常有较大的尺寸,并且原始成本比现成的要高。 An acoustic filter consists of a choke (a mass element), one or more volumes (spring element), and usually an orifice plate (a damping element) (Figures 1i and 1j). To design an acoustic filter, a cut-off frequency is selected (usually one-half the plunger frequency), and pipe sizes are selected based on the allowable pressure drop, local site requirements, and cost. 声学滤波器由一个阻风门(一个主要部件) 、一个或多个容积(弹性部件) 和一个孔板(一个阻尼部件)组成(图 1i 和 1j) 。为了设计一个声学滤波器, 需要选择一个截止频率(通常是柱塞频率的一半) ,并且管道尺寸的选择基于适 当的压降、所需的局部尺寸和成本。 A volume-choke filter was designed and analyzed for this system.The final filter design consisted of a 7-foot-long bottle with an inside diameter of 35 inches and a 4-foot-long choke tube with an inside diameter of 1.5 inch. A 10 psi orifice was simulated at the pump flange to attenuate the quarter-wave resonance. As shown in Figure 11, maximum pulsations (obtained by the superposition of all harmonics) are calculated to be less than 5 psi in the piping, and less than 10 psi at the plunger face. The acoustic filter attenuates the high frequency excitation such that, outside the choke tubes, only the first two harmonics of plunger frequency are transmitted. 设计一个容阻式滤声器来分析这个系统。最终设计的滤声器由一个 7 英寸 长、内径为 35 英寸的瓶体和一个 4 英尺长、内径为 1.5 英寸的阻气管组成。在 泵法兰上模拟的一个 10 磅/平方英寸的孔用来减弱 1/4 波的共振。 如图 11 所示, 计算出的管道内最大脉动(由所有的谐波叠加而得)低于 5 磅/平方英寸,柱塞 正面的最大脉动低于 10 磅/平方英寸。声学滤波器使高频激励衰减,这样一来, 在软管的外面只传播前两个柱塞谐波。在泵的主管,其他结构也在讨论。使用双 筒式可以获得更大的衰减(图 12) 。图 13 中所示双筒节流滤声器的衰减通过把 单筒滤声器阻风门的内径减少到 1 英寸来匹配。 实践表明双筒很少在液体系统中 用到。通过减少阻气管的直径,亥姆霍兹固有频率会降低,这是因为随着直径减 少, 阻气管的声学质量增加了。 随着亥姆霍兹频率降低, 所选频率的衰减会增加。

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.11 'ID w/4'×1.5' 'choke ALF-VC—7'×35'

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

Fig.11

'ID w/4'×1.5' '阻风门 ALF-VC—7'×35'

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.12 'ID w/4'×1.5' 'choke ALF-VC—2-7'×35'

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

Fig.12

'ID w/4'×1.5' '阻风门 ALF-VC—2-7'×35'

VERTICAL SCALE PSI (P-P) HORIZONTAL SCALE FREOUENCY(Hz) Fig.13 'ID w/4'×1' 'choke ALF-VC—7'×35'

纵坐标

磅/平方英寸 (峰值)

横坐标 频率(Hz)

Fig.13

'ID w/4'×1' '阻风门 ALF-VC—7'×35'

CONCLUSIONS Detailed modeling of a typical pump piping system was performed to develop, a basic understanding of the acoustic behavior of accumulators used in such systems. Based upon the calculations and the application of acoustic theory, the following conclusions can be made. 结论 一个典型泵管系统的细致建模得到了发展, 在这个系统中运用到了缓冲器声 学特性的基本理解。基于声学理论的计算和运用,可以得到一下结论。 1. Accurate calculations of the pulsation at any point in a pump or compressor piping system can be made with computer programs which can simulate the acoustical characteristics of all the acoustical elements in a piping system. Through the use of such programs, it is possible to study the effects of small changes in the acoustical system, such as chang in the accumulator characteristics. 1. 在泵或压缩机管道系统的任意一点脉动的精确计算可由计算机程序得 到,这些计算机程序能够模拟管道系统中的所有声学因素的声学特性。

2. The introduction of an accumulator near the flanges of the suction or discharge manifold creates a new acoustical system.One major resonance that is introduced is a natural frequency which is a function of the distance from the end of the manifold to the entrance of the accumulator and the speed of sound in the fluid, This natural frequency will be excited by the higher plunger harmonics and can cause numerous problems. 2. 引入一个接近吸入或排出主管法兰的缓冲器能够创建一个新的声学系 统。引入的一个主要共振是一个固有频率,该固有频率是主管端头到缓 冲器入口距离和液体中声速的函数。这个固有频率是由较高的柱塞谐波 激发的,并且会导致很多问题。 3. The majority of cavitation problems on suction systems are caused by this acoustical mode since most systems have some kind of accumulator near the pump flange. Using the digital computer program, the onset of cavitation can be accurately calculated and the need for a charge pump properly evaluated. 3. 吸入系统上主要的气穴现象问题是由这个声学模型引起的,这是因为大 多数系统有有一些靠近泵法兰的缓冲器。使用数字化电脑程序,气穴的 成因能够准确地分析出来,电荷泵的需求也能正确地评估出来。 4. The quarter-wave manifold resonances can be attenuated with properly sized orifice plates near the pump or accumulator flanges. 4. 1/4 波的多种共振因泵或缓冲器法兰附近适当尺寸的孔板而衰减。 5. Accumulators with gas-filled bladder/ diaphragm designs can be effective for low frequencies in simple systems. 5. 带有气囊/隔膜设计的缓冲器在简单系统低频时有效。 6. Accumulators with gas charge are sensitive to the gas volume and therefore, should be checked on a regular basis to ensure that the system is working properly. 6. 气充式缓冲器对于气体体积是很灵敏的,因此必须定期检查以确保系统 的正常工作。

7. In multi-pump systems, the units can interact with each other to create severe problems if each of the accumulators with gas charges are not identical. If only one of the accumulators looses its gas charge, the pulsations in all the pumps can be acted. 7.在多泵系统中,如果每个气充式缓冲器不完全相同的话,其中每个都会影 响到其它,从而产生严重的问题。如果只是其中的一个缓冲器跑气了,所 有泵里的脉动就会发生变动。 8. The frequency response of the gas-filled bladder/ diaphragm accumulators is limited by the throat dimensions, i. e., the larger the throat diameter the more effctive the accumulator. 8.气囊/隔膜缓冲器的频率响应受到颈部尺寸的限制,颈部尺寸越大,缓冲 器越有效。 9. The flow-through, gas-filled, or gas blanket accumulators have improved frequency response since the throat restriction is removed. 9.流通式、气充式或气层式缓冲器的频率响应得到了改善。这是因为没有了 颈部限制 10. All-liquid acoustic low pass filters (Helmholtz type) can be designed to achieve nearly any desired attenuation. The filter design is based on the Helmholtz frequency and the allowable pressure drop. All-liquid filters are not sensitive to system pressures since the speed of sound for most liquids does not change significantly with pressure. The attenuation of the filter is increased as the frequency increases; therefore, such designs; will work over large speed ranges. 10.设计的全液式低通滤声器 (亥姆霍兹型) 几乎可以实现所需要的任何衰减。 滤声器的设计是基于亥姆霍兹频率和允许的压降。 全液式滤声器对于系统 压强的反应不灵敏,这是因为大多数液体中的声速不随压强有明显的变 化。滤声器的衰减随着频率的增加而增加;因此这样的设计会有较大的范 围的工作速度。 11. Pumps and their piping systems should be analyzed for their pulsation characteristics before they are built to prevent problems before they occur. For example, a significant number of piping failures reported to the Nuclear Regulatory Committee (NRC) by the nuclear plant operators have occurred in their reciprocating charge pumps [7]. If these systems were properly analyzed in the design stage, most of these failures could have been eliminated.

11. 泵和它们的管道系统在预防问题发生之前就该对它们的脉动特性进行分 析。 例如, 大量的管道故障通过核电运营商报告给核电管制委员会 (NRC) , 这些故障已经出现在他们的往复泵里。如果这些系统在设计阶段进行正 确的分析,大多数故障就不会发生。

Unit Conversions 1 psi=6.895 Kpa 1 in=0.0254m 1 ft=0.3048m 1 in3=1.64×10 5m3


The terms accumulator,dampener,damper,filter,stabilizer,and desurger are used in the industry to describe devices that are used to control pulsations.In this paper the term accumulator will be used to describe such devices.
1

1

缓冲器、阻尼器、风门、滤声器、固定装置和波动消除器在工业中用来构成控制脉动

的设备。在这个论文中缓冲器将用来描述这些设备。

During the idealized pumping process,either the suction or discharge valve is closed.The acoustical properties of the discharge side are therefore effectively isolated from the suction side.Reference [4] provides details concerning the acoustical modeling procedures used for this document. 在理想吸水过程中,吸入和排出阀门都是关着的。排出侧的声学特性有效 地和吸入侧分开。参考书目为这个文件提供了声学建模程序的有关细节。 This phenomenon can cause pulsation levels in the manifold of a quintuplex pump to be higher than those in a triplex pump,even though the generated pulsation energy of a quintuplex pump is lower than that of the triplex pump. 这个现象可能导致在五缸泵主管中的脉动强度比三缸泵主管中的脉动强度 要高,即使五缸泵中脉动产生的能量没有在三缸泵中的高。
3 2

2

3

单位换算

1 psi=6.895 Kpa 1 in=0.0254m 1 ft=0.3048m 1 in3=1.64×10 5m3 Acknowledgment The authors acknowledge the contribution of their colleagues at Engineering Dynamics Incorporated and particularly J. D. Tison who was the major developer of the computer program for analyzing the acoustical characteristics of piping systems. 答谢 作者感谢他们在工程动力公司同事们的帮助, 特别是分析管道声学特性计算 机程序的主要开发者 J.D.Tison。
References 参考文献 1. Wachel, J. C., Szenasi, F. R. , and Denison, S . C. , “Acoustical Analyses Solve Vibration, Failures in Recip Pumps", Oil Gas Journal, August 11, 1986, pp. 58-69. 2. Wachel, J. C ., Szenasi, F. R., and Denison, S. C. , Analysis of Vibralion and Failure Problems in Reciprocating Triplex Pumps for Oil Pipelies, ASME Paper 85-PET-10, 1985. 3. Miller,J.C., “Liquid Dynamics of Reciprocating Pumps—Parts 1 and 2”,The OIL and Gas Journal,April 18,1983. 4. Wachel, J. C. , Szenasi, F. R., et al, Vibrations in Reciprocating Machinery and Piping Systems, EDI Educational Seminar, San Antonio, TX, EDI Report 85-305, October, 1985. 5. Ludwig, M., Design of Pulsalion Dampeners for High Speed Reciprocating Pumps, Division of Transportation, American Petroleum Institute, Vol. 36 [V], 1956, pp. 47-54. 6. Hicks, E. J. and Grant, T. R., "Acoustic Filter Controls Recip Pump Pulsation", The Oil and Gas Journal, January 15, 1979,pp. 67-73. 7. Olson, David E. , "Piping Vibration Experience in Power Plants",Pressure Vessel and Piping Technology 1985, American Society of Mechanical Engineers, 1985, pp. 689-705.



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