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畢業(yè)設(shè)計(jì)（論文）題目：100噸通用油壓機(jī)的液壓系統(tǒng)設(shè)計(jì)
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100噸通用油壓機(jī)的液壓系統(tǒng)設(shè)計(jì)
摘要
油壓機(jī)是一種以液壓油為工作介質(zhì)，根據(jù)帕斯卡原理制成的用于傳遞能量以實(shí)現(xiàn)各種工藝的機(jī)器。液壓機(jī)是一種鍛壓機(jī)械，它能完成調(diào)直、冷沖壓、冷擠壓等多種鍛壓工藝。液壓機(jī)的結(jié)構(gòu)形式很多，但通常由橫梁、立柱、工作臺(tái)、滑塊和頂出機(jī)構(gòu)等部件組成。本文為100T通用油壓機(jī)液壓系統(tǒng)設(shè)計(jì)，通過對(duì)油壓機(jī)主缸及頂出缸進(jìn)行工況分析，繪制其速度圖和負(fù)載圖。選擇液壓基本回路，擬定液壓系統(tǒng)原理圖，使主缸能完成快速下行、減速壓制、保壓延時(shí)、泄壓回程、停止的基本工作循環(huán)，頂出缸能實(shí)現(xiàn)頂出、退回、浮動(dòng)壓邊的動(dòng)作，之后對(duì)液壓系統(tǒng)控制過程進(jìn)行分析。確定液壓系統(tǒng)的主要參數(shù)，通過對(duì)壓力、流量等參數(shù)的分析與計(jì)算，對(duì)泵、電機(jī)、控制閥等液壓元件和輔助件進(jìn)行了選擇。本次設(shè)計(jì)采用了集成塊，除去與泵或液壓缸等的連接仍然采用管接頭和管道以外，其它各元件之間的連接都通過集成塊上的通道，其結(jié)構(gòu)更為緊湊，體積也相對(duì)更小，重量也更輕，大大減少管件連接，從而消除了因油管、接頭引起的泄漏、振動(dòng)和噪聲，并且液壓系統(tǒng)安裝 、調(diào)試和維護(hù)方便，壓力損失小，外形美觀。另外對(duì)液壓站進(jìn)行了總體布局。通過液壓系統(tǒng)壓力損失和溫升的驗(yàn)算，本文液壓系統(tǒng)的設(shè)計(jì)可以滿足液壓機(jī)工作循環(huán)的動(dòng)作要求，能夠?qū)崿F(xiàn)塑性材料的成型加工工藝。
關(guān)鍵詞 油壓機(jī)；液壓系統(tǒng)；原理圖；集成塊；液壓站
The design of 100T hydraulic press hydraulic system
Abstract
Hydraulic presses are machines that use liquid as working medium and are made according to the principle of PASCAL to deliver energy to achieve various processes. Hydraulic presses are metal forming machines which can complete various forging technology such as alignment, cold forging, cold extruding and so on. Hydraulic presses have many structural forms but more often than not they are composed of crossbeam, vertical post, work table, slide block and ejector parts. This paper is about the design of 100T hydraulic press's hydraulic system, though the condition analysis of the hydraulic press's main cylinder and ejection cylinder, we can draw their velocity diagrams and load diagrams. Then we choose basic hydraulic circuit to form the hydraulic system schematics. We must make sure the main cylinder can complete the basic working cycle of fast descending, deceleration repression, time delay of press forming, relinef-pressure return and stop, and on the other hand, ejection cylinder can realize the action of ejection, return and floating side pressing. After that, we must analyse the control process of the hydraulic system. Hydraulic system's main parameters are determined and through the analysis and calculation of pressure, flow and other parameters, and then we can go on the choose hydraulic components and auxiliary parts such as pump , motor, filters, control valves. This design adopted the manifold block, and except that the connection of pump and hydraulic cylinder still uses the pipes and pipe joints, the connection of other components all through the channel of the manifold block. Its structure is more compact, volume is relatively smaller, its weight is lighter without pipe connection. What's more, it can eliminate leakage of tubing, connectors, vibration and noise, also, the installation, commissioning and maintenance of hydraulic systrem are convenient, low pressure drop, and it looks more beautiful.The paper has also designed the overall layout of the hydraulic station.what is more this paper have three-dimensional graph of integrated block, hydraulic pressure station, which make it more beautiful and accessible to reader. The hydraulic system can meet the press order cycle action requires and realize the plastic material forging press, stamping cold extrusion, straightening, bending forming process and other contour machining technic through check calculation of hydraulic system pressure loss and the temperature of the hydraulic system.
Key words hydraulic press;hydraulic system;system diagram; manifold block;hydraulic station
5
目 錄
摘要 I
Abstract II
第1章 緒論 1
1.1 研究背景 1
1.2 研究目的與意義 1
1.2.1 研究目的 1
1.2.2 研究意義 2
1.3 研究?jī)?nèi)容 2
第2章 液壓系統(tǒng)設(shè)計(jì)要求和工況分析 3
2.1 明確對(duì)液壓系統(tǒng)的設(shè)計(jì)要求 3
2.2 液壓系統(tǒng)的工況分析 4
2.2.1 液壓機(jī)主缸的工況分析 4
2.2.2 液壓機(jī)頂出缸的工況分析 5
第3章 確定液壓系統(tǒng)主要參數(shù) 7
3.1 確定液壓缸的主要參數(shù) 7
3.1.1初選液壓缸的工作壓力 7
3.1.2 確定液壓缸的主要結(jié)構(gòu)尺寸 7
3.2 計(jì)算系統(tǒng)所需壓力 8
3.3 系統(tǒng)流量的計(jì)算 9
3.3.1 主缸流量的計(jì)算 9
3.3.2. 頂出缸流量的計(jì)算 10
第4章 液壓機(jī)液壓系統(tǒng)原理圖設(shè)計(jì) 11
4.1 系統(tǒng)原理圖的設(shè)計(jì) 11
4.2 液壓系統(tǒng)原理圖的問題 13
4.3 液壓系統(tǒng)的工作原理 14
第5章 液壓元件的選擇 17
5.1 確定液壓泵及驅(qū)動(dòng)電機(jī)的功率 17
5.1.1 確定液壓泵的工作壓力 17
5.1.2 確定液壓泵的最大流量 17
5.1.3 選擇液壓泵的規(guī)格 18
5.1.4 電動(dòng)機(jī)的選擇 18
5.2 閥類元件及輔助元件的選擇 18
5.3 管道尺寸的確定 20
5.4 油箱容積的確定 20
5.5 系統(tǒng)溫升的驗(yàn)算 21
第6章 液壓站結(jié)構(gòu)設(shè)計(jì) 23
6.1 液壓站的結(jié)構(gòu)型式 23
6.2 液壓泵的安裝方式 23
6.3 液壓集成油路的設(shè)計(jì) 23
6.4 液壓油箱的設(shè)計(jì) 24
結(jié)論 27
致謝 28
參考文獻(xiàn) 29
附錄 30
附錄
Pressure transient theory
Before embarking on the analysis of pressure transient phenomena and the derivation of the appropriate wave equations,it will be usefull to describe the general mechanism of pressure propagation by reference to the events fllowing the instantaneous closure of a value postioned at the med-length point of a frictionless pipeline carrying fluid between two reservoirs.The two pipeline sections upstream and downstream of the value are identical in all respects.Transient pressure waves will be propagated in both pipes by valve operation and it will be assumed that rate of value closure precludes the use of rigid column theory.
As the valve is closed,so the fluide approaching its upstream face is retarded with a consequent compression of the flude and an expansion od the pipe cross-section.The increase in pressure at the valve results in a pressure wave being propagated upstream which conveys the retardation of flow to the column of fluid approaching the valve along the upstream pipeline.This pressure wave travels through the fluid at the appropriate sonic velocity,which will be shown to depend on the properties of the fluid and the pipe material.
Similarly,on the downstream side of the valve the retardation of flow results in a reduction in pressure at the valve,with the result that a negative pressure waves is propagated along the downstream pipe which,in turn,retards the fluid flow.It will be assumed that this pressure drop in the downstream pipe is insufficient to reduce the fluid pressure to either its vapour pressure or its dissolved gas release pressure,which may be considerable different.
Thus,closure of the valve results in propagation of pressure waves along both pipes and,although these waves are of different sign relative to the steady pressure in the pipe prior to valve operation,the effect is to retard the flow in both pipe sections.The pipe itself is affected by the wave propagation as the upstream pipe swells as the pressure rise wave passes along it,while the downstream pipe contracts due to the passage of the pressure reducting wave.The magnitude of the deformation of the pipe cross-section depends on the pipe material and can be well demonstrated if,for example,thin-walled rubber tubing is employed.The passage of the pressure wave through the fluid is preceded,in practice,by a strain wave propagating along the pipe wall at a velocity close to the sonic velocity in the pipe material.However,this is a secondary effect and,while knowledge of its existence can explain some parts of a pressure-time trace following valve closure,it has little effect on the pressure levels generated in practical transient situations.
Following valve closure,the subsequent pressure-time history will depend on the conditions prevailing at the boundaries of the system.In order to describe the events following valve closure in the simple pipe system outlined above,it will be easier to refer to a series of diagrams illustrating conditions in the pipe at a number of time steps.
Assuming that valve closure was instantaneous,the fluid adjacent to the valve in each pipe would have been brought to rest and pressure waves conveying this information would have been propagated at each pipe at the appropriate sonic velocity c.At a later time t,the situation is as shown in fig.The wavefronts having moved a distance 1=ct,in each pipe,the deformation of the pipe cross-section will also have traveled a distancel as shown.
The pressure waves reach the reservoirs terminating the pipes at a time t=1/c.at this instant,an unbalanced situation arises at the pipe-reservior junction,as it is clearly impossible for the layer of fluid adjacent to the reservoir inlet to maintain a pressure different to that prevailing at that depth in the reservoir.Hence,a restoring pressure wave having a magnitude suffcient to bring the pipeline pressure back to its value prior to valve closure is transmitted from each reservoit at a time 1/c.For the upstream pipe,this means that a pressure wave is propagated towards the closed valve,reducing the pipe pressure to its original value and restoring the pipe cross-section.The propagation of this wave also preduces a fluid flow from the pipe into the reservoir as the pipe ahead of the moving wave is at a higher pressure than the reservoir.Now,as the system is assumed to be frictionless,the magnitude of this reversed flow will be the exact opposite of the original flow velocity,as shown in fig.
At the downstream reservoir,the converse occurs,resulting in the propagation of a pressure rise wave towards the valve and the establishment of a flow from the downstream reservoir towards the valve.
For the simple pipe considered here,the restoring pressure waves in both pipes reach the valve at a time 21/c.The whole of the upstream pipe has,thus,been returned to its original pressure and a flow has been established out of the pipe.At time 21/c,as the wave has reached the valve,there remains no fluid ahead of the wave to support the reversed flow.A low pressure region,therefore,forms at the valve,destroying the flow and giving rise to a pressure reducing wave which is transmitted upstream from the valve,once again bringing the flow to rest along the pipe and reducing the pressure within the pipe .It is assumed that the pressure drop at the valve is insufficient to reduce the pressure to the fluid vapour pressure.As the system has been assumed to be frictionless,all the waves will have the same absolute magnitude and will be equal to the pressure increment,above steady running pressure,generated by the closure of the valve.If this pressure increment is h,then all the waves propagating will be±h,Thus,the wave propagation upstream from the valve at time 21/c has a value-h,and reduces all points along the pipe to –h below the initial pressure by the time it reachs the upstream reservoir at time 31/c.
Similarly,the restoring wave from the downstream reservoir that reached the valve at time 21/c had established a reversed flow along the downstream pipe towards the closed valve .This is brought to rest at the valve,with a consequent rise in pressure which is transmitted.downstream as a +h wave arriving at the downstream reservoir at 31/c,at which time the whole of the downstream pipe is at pressure +h above the initial pressure whth the fuid at rest.
Thus,at time 31/c an unbalanced situation similar to the situation at t=1/c again arises at the reservoir –pipe junctions with the difference that it is the upstream pipe which is at a pressure below the reservoir pressure and the downstream pipe that is above reservoir pressure .However,the mechanism of restoring wave propagation is identical with that at t=1/c,resulting in a-h wave being transmitted from the upstream reservior,which effectively restores conditions along the pipe to their initial state,and a+h wave being propagated upstream from the downstream reservoir,which establishes a flow out of the downstream pipe.Thus,at time t=41/c when these waves reach the closed valve,the conditions along both pipes are identical to the conditions at t=0,i.e.the instant of valve closure.However ,as the valve is still shut,the established flow cannot be maintained and the cycle described above repeats.
The pipe system chosen to illustrate the cycle of transient propagation was a special case as,for convenience,the pipes upstream and downstream of the valve were identical.In practice,this would be unusual.However,the cycle described would still apply,except that the pressure variations in the two pipes would no longer show the same phase relationship.The period of each individual pressure cycle would be 41/c,where I and c took the appropriate values for each pipe.It is important to note that once the valve is closed the two pipes will respond separately to any further transient propagation.
The period of the pressure cycle described is 41/c.However,a term ofen met in transient analysis is pipe period,this is defined as the time taken for a restoring reflection to arrive at the source of the initial transient propagation and,thus,has a value 21/c.In the case described,the pipe period for both pipes was the same and was the time taken for the reflection of the transient wave propagated by valve from the reservoirs.
From the description of the transient cycle above,it is possible to draw the pressure-time records at points along the pipeline.These variations are arrived at simply by calculating the time at which any one of the±h waves reaches a point in the system assuming a constant propagation velocity c.The major interest in pressure transients lies in methods of limiting excessive pressure rises and one obcious method is to reduce valve speeds.However,reference to fig.illustrates an important point no reduction in generated pressure will occur until the valve closing time exceeds one pipe period.The reduction in peak pressure achieved by slowing the valve before a time 21/c from the start of valve closure and,as no beneficial pressure relief can be achieved if the valve is not open beyond this time.Generally,valve closures in less than a pipe period are referred to as rapid and those taking longer than 21/c are slow.
In the absence of friction,the cycle would continue indefinitely.However ,in practice, friction damps the pressure oscillations within a short period of time .In system where the frictional losses are high,the neglect of frictional effects can result in a serious underestimate of the pressure rise following valve closure.In these case,the head at the valve is considerably lower than the reservoir head.However,as the flow is retarded,so the frictional head loss is reduced along the pipe and the head at the valve increase towards the reservoir value.As each layer of fluid between the valve and the reservoir is brought to rest by the passage of the initial +h wave so a series of secondary positive waves each of a magnitude corresponding to the friction head recoverd is transmitted toward the valve,resulting in the full effect being felt at time 21/c.As the flow reverses in the pipe during time 21/c to 41/c,the opposite effect is recorded at the valve because of the re-establishment of a high friction loss,these variations being shown by lines AB and CD.In certain cases,such as long distance oilpipelines,this effect may contribute the larger part of the pressure rise following valve closure.
In addition to the assumptions made with regard to friction in the cycle description,mention was also made of the condition that the pressure drop waves at no time reduced the pressure in the system to the fluid vapour pressure.If this had occurred,then the fluid column would have separated and the simple cycle described would have been disrupted by the formation of a vapour cavity at the position where the pressure was reduced to vapour level.In the system described,this could happen on the valve’s downstream face at time 0 or on the upstream face at time 21/c.The formation of such a cavity is followed by a period of time when the fluid column moves under the influence of the pressure gradients between the cavity and the system boundaries.The period is normally terminated by the generation of excessive pressure on the final collapse of the cavity.This phenomena is generally referred to as column separation and is frequently made more complex by the release of dissolved gas in the vicinity of the cavity.
Pressure transient propagation may be defined in any closed pipe application by two basic equations,namely the equations of motion and continuity applied to a short segment of the fluid column.The dependent variables are the fluid’s average pressure and velocity at any pipe cross section and the independent variables are time and distance,normally considered positive in the steady flow direction.Friction will be assumed proportional to velicity squared and steady flow friction relationships will be assumed to apply to the unsteady flow cases considered.
壓力沖擊現(xiàn)象
在著手分析壓力沖擊現(xiàn)象和化分合理的流體方程之前，去描繪一般的關(guān)于壓力傳遞的機(jī)械理論。通過參與這個(gè)關(guān)于閥門定位在一個(gè)較長(zhǎng)點(diǎn)幾乎沒有摩擦的管道傳輸液體于兩個(gè)蓄能源之間的結(jié)果之后是必要的。這個(gè)閥門連接的順流管道截面和逆流管道截面考慮是一樣的。壓力沖擊流將通過閥門操作傳遞在兩個(gè)管道之間，并且假設(shè)閥門的關(guān)閉速度不應(yīng)用于堅(jiān)固圓管理論。
如果閥門是關(guān)閉的，而液體的流向是逆方向的，緩慢前進(jìn)，結(jié)果導(dǎo)致液體被壓縮和管道的橫截面膨脹。閥門的壓力增加導(dǎo)致高壓液體逆向流動(dòng)，延長(zhǎng)了液體流過圓管通向閥這段管道的時(shí)間。這種高壓液體的流動(dòng)類似聲音的傳播，是依靠液體和管道材料作為介質(zhì)的。
同樣，閥的順流面流動(dòng)的延遲，將導(dǎo)致減小壓力在閥門處。這個(gè)結(jié)果否定了高壓液體的流動(dòng)是沿著順流管道的，阻止液體流動(dòng)，假設(shè)流體壓力在順流管道是不能減小液體壓力的或者蒸汽壓力或者溶解氣體釋放的壓力，各種愿意的考慮是不同的。
這樣，關(guān)閉著的閥門導(dǎo)致高壓液體的流動(dòng)是沿著管道的，盡管那些流動(dòng)有著各種不同的征兆。相對(duì)于穩(wěn)定的壓力流經(jīng)閥門開啟的管道。這種影響是關(guān)于液體流動(dòng)的延遲在兩種管道截面之間，管道自身受到影響由于液體逆向產(chǎn)生高壓，管壁膨脹。同時(shí)，順流管道縮短，由于流經(jīng)液體的壓力降低，這種管道橫截面的巨大變形是由于管道材料的，并且能夠被證明。例如，使用薄壁型橡膠管材。高壓液體沿著液流前進(jìn)。實(shí)踐證明，由于液體的張力流向沿著管壁，它的速度接近于聲速。在這種管道材料中，然而，這是一種次要作用，當(dāng)認(rèn)識(shí)到它的存在，能夠解釋一部分壓力的傳遞時(shí)間隨著閥門關(guān)閉特點(diǎn)，它幾乎沒有影響到壓力標(biāo)準(zhǔn)應(yīng)用在壓力沖擊現(xiàn)象。
在閥門關(guān)閉之后，這時(shí)是受壓時(shí)間將主要依靠系統(tǒng)的邊界條件，為了描繪閥門關(guān)閉的結(jié)果在同一個(gè)系統(tǒng)上，它將很容易說明在大量的圖表上面，管道在每個(gè)時(shí)間段的情形。
由于閥門的關(guān)閉是瞬時(shí)的，液體接近每一段管道的閥門會(huì)帶來停止，并且高壓液體流動(dòng)情況可能已經(jīng)流過每一段管道。在適應(yīng)的流速c和一段時(shí)間t，這時(shí)液體已經(jīng)流過了一段距離1=ct，在每一段管道內(nèi)，這時(shí)管道的橫截面是變形也有一段距離1。
高壓液體到達(dá)蓄能站通過管道的時(shí)間為t=1/c，在這段距離中出現(xiàn)了一個(gè)不穩(wěn)定的位置，是在管道與蓄能站連接處。由于是不可能出現(xiàn)層流在蓄能站連接處，而保持壓力不同及其它的值在閥門關(guān)閉之前，流過每一個(gè)蓄能站的時(shí)間為1/c，在逆向管道這邊是高壓液體的流動(dòng)朝向閥門的關(guān)閉。減小管壁的壓力到其原值，并且恢復(fù)管壁的橫截面積。這時(shí)液體的流動(dòng)需要產(chǎn)生差值。從管道流向蓄能站，在管道的前段的液體流動(dòng)有比較高的壓力比蓄能站?，F(xiàn)在，由于系統(tǒng)假設(shè)沒有摩擦，這種巨大的逆向流動(dòng)會(huì)有精確的對(duì)比和最初的流動(dòng)速度。
在順流蓄能站，存在相反的情況，導(dǎo)致液體壓力上升流向和確定的順流流向從蓄能站到閥門。
由于這里考慮的是簡(jiǎn)單的管道，恢復(fù)高壓液體在管道和閥門之間的時(shí)間為21/c。整個(gè)逆流管道也是同樣，在返回最初的壓力和流向在管道外也被確定時(shí)間為21/c，由于液體已經(jīng)到達(dá)閥門，意味著沒有液體提前在提供的逆向一個(gè)低的壓力區(qū)域形成在閥門外，破壞了流向和給上升的壓力減小流動(dòng)流向逆方向的閥門。再一次，帶來流動(dòng)的停止沿著管道且減小壓力在管道中。它已經(jīng)被假設(shè)在閥門處壓力下降，減小蒸發(fā)壓力。由于系統(tǒng)已經(jīng)假設(shè)沒有摩擦，所有的液面會(huì)有相同，絕對(duì)的，巨大的壓力增加。在穩(wěn)定的運(yùn)動(dòng)壓力下，會(huì)通過閥門的關(guān)閉產(chǎn)生。如果壓力增長(zhǎng)是h，這時(shí)所有的液面是h，因此，液體逆流經(jīng)過閥門的時(shí)間為21/c，存在一個(gè)值-h,同時(shí)，減少所有沿著管道的點(diǎn)從h降到最初的壓力時(shí)間逆向流動(dòng)到蓄能站的時(shí)間為31/c。
類似的，恢復(fù)液體最初的順流到閥門的時(shí)間為21/c，并且流向從順流管道流向閥門關(guān)閉，這會(huì)在閥門處帶來流動(dòng)停止，導(dǎo)致壓力上升。在整個(gè)順流管道的每一段時(shí)間內(nèi)壓力h上升到最初的壓力在流動(dòng)停止時(shí)。
因此，在31/c時(shí)是一種不穩(wěn)定的情形類似于在t=1/c的情形，出現(xiàn)在蓄能站和管道的連接處存在著不同。即是逆流管道壓力下降到最初壓力和順流管道上升到最初壓力，然而，這種液體流動(dòng)恢復(fù)機(jī)構(gòu)所用時(shí)間是相同的t=1/c。結(jié)果是逆流流向蓄能站，它有效地恢復(fù)環(huán)境沿著管道到它的最初值。當(dāng)液體到達(dá)關(guān)閉的閥門時(shí)，沿著每一段管壁都是相同的時(shí)間t=0，然而，由于閥門一直是關(guān)閉的，這種情形不能保持循環(huán)流動(dòng)周期。
管道系統(tǒng)采用循環(huán)流動(dòng)周期，瞬時(shí)選擇一種專門的機(jī)械情形，管道的順流和逆流對(duì)于閥是一樣的。實(shí)際 ，這是不同的。因而，所描繪的周期將一直被使用，除了壓力變化在兩管道之間不再表示相同相位關(guān)系，每一個(gè)壓力周期的變化將是41/c，那里1和c代表著每一段管道適應(yīng)的時(shí)期，這是重要的標(biāo)記，一旦閥門是關(guān)閉的，這兩個(gè)管道將做出相應(yīng)的流動(dòng)到任何一段距離。
通過上述沖擊周期的描繪，可以劃分壓力-時(shí)間關(guān)系，在某一點(diǎn)沿管道上，這些變化的出現(xiàn)是類似的。通過時(shí)間在任何一點(diǎn)h，液體到達(dá)某一點(diǎn)，系統(tǒng)假設(shè)流動(dòng)速度為一個(gè)常數(shù)c，這主要集中在壓力沖擊依靠的方法是限制壓力的升高和減小閥的啟閉速度。然而，存在著很重要的一點(diǎn)，沒有減小開啟壓力，將發(fā)生直到閥的關(guān)閉時(shí)間先于另一個(gè)管道。減小壓力達(dá)到出現(xiàn)閥門慢速關(guān)閉的結(jié)果先于忽略液體逆流到閥門關(guān)閉。由于沒有影響，返回到閥門時(shí)間21/c前，從閥門開始運(yùn)動(dòng)沒有壓力減小能夠到達(dá)如果閥門沒有打開超過了時(shí)間。一般來說，閥門的關(guān)閉小于管道涉及的速度并且它將比21/c短。
在沒有摩擦的情況下，周期的繼續(xù)是不確定的。然而，實(shí)際中，摩擦力是壓力損失在很短的時(shí)間內(nèi)，系統(tǒng)的摩擦損失越高，忽略摩擦力的影響導(dǎo)致結(jié)果越嚴(yán)重。事實(shí)上，閥門的頂點(diǎn)低相對(duì)于蓄能站頂點(diǎn)。然而，由于緩慢的流動(dòng)，摩擦點(diǎn)的損失減少。沿著管壁并且這個(gè)點(diǎn)向著蓄能站的方向增長(zhǎng)。由于液體的每一層，在閥門和蓄能站中會(huì)帶來停止，通過流動(dòng)最初的液面，所以大多在第二個(gè)液面位置相應(yīng)的摩擦點(diǎn)恢復(fù)流向。閥門導(dǎo)致影響整個(gè)時(shí)間21/c。由于流動(dòng)是相反的在管道中時(shí)間為21/c和41/c。這個(gè)位置影響主要在閥門，由于重新建立一個(gè)新的摩擦損失，在確切的事例中，例如，長(zhǎng)距離油管，在閥門關(guān)閉之前，它將上升一部分壓力。
隨著假設(shè)條件對(duì)摩擦周期的描繪，提及到使壓力下降的條件，如果這些情況發(fā)生，這時(shí)流向圓管已經(jīng)分離出類似的周期描繪，可能中斷通過形成蒸氣壓力減小的位置有蒸氣生成。因此，系統(tǒng)描述可能發(fā)生在閥門的順流時(shí)間0或者逆流時(shí)間21/c形成一個(gè)腔。由于一段時(shí)間液體沿管壁流動(dòng)在一個(gè)壓力梯度下，在這個(gè)腔和系統(tǒng)邊界之間。這種方法是通常由于產(chǎn)生額外壓力在最后的腔中。這種現(xiàn)象一般涉及到像圓管的分離和通常的制作更多的錯(cuò)綜復(fù)雜的由于釋放溶解的氣體在附近的腔中。
沖擊壓力也許被定義為在一些封閉的管道中應(yīng)用，通過兩個(gè)基本的方程，分別是運(yùn)動(dòng)平衡方程和連續(xù)應(yīng)用在一個(gè)短的流體圓管。它依靠可變的流體平均壓力和速度在任何一段管道的橫截面，且不依靠可變的時(shí)間和距離。通?？紤]實(shí)際的穩(wěn)流方向。摩擦力將被假設(shè)與速度平方成比例，并且穩(wěn)流摩擦關(guān)系將被假設(shè)應(yīng)用在非穩(wěn)定事例中。
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