泵的概述外文翻譯

1、<p>　　附錄一：外文文獻(xiàn)原文 </p><p>　　Pump's outline</p><p>　　The pump is the application very widespread general machinery, may say that is place of the fluid flow, nearly has the pump

2、 in the work. Moreover, along with science's and technology's development, pump's application domain is expanding rapidly, according to the over-all state statistics, pump's power consumption approximatel

3、y composes the national total output of electrical energy 1/5, obviously the pump is natural consumes energy the wealthy and powerful family. Therefore, raises the pump tech</p><p>　　First. Centrifugal pump&

4、#39;s principle of work</p><p>　　The drive leads impeller revolving through the pump spindle to have the centrifugal force, under the centrifugal action of force, the liquid is flung along the leaf blade flo

5、w channel to the impeller export, the liquid sends in after the volute collection the eduction tube. The liquid obtains the energy from the impeller,  causes the pressure energy and the speed can increase, and depends u

6、pon this energy the hydraulic transport to the operating location. while the liquid is flung which exports</p><p>　　Second, centrifugal pump's structure and main spare part</p><p>　　A centri

7、fugal pump mainly by the pump body, the impeller, the packing ring, the rotation axis, the axis seals parts and so on box to be composed, some centrifugal pumps are also loaded with the guide pulley, the inducer, the bal

8、ance disc and so on. </p><p>　　1. Pump body: Namely pump's shell, including suction chamber and delivery chamber. </p><p>　?、賁uction chamber: Its function is enables the liquid to flow in ev

9、enly the impeller.</p><p>　?、贒elivery chamber: Its function collects the liquid, and sends in it the subordinate impeller or guides the eduction tube, at the same time reduces the liquid the speed, causes th

10、e kinetic energy to further turn the pressure energy. The delivery chamber has the volute and the guide vane two forms. </p><p>　　2. Impeller: It is in the centrifugal pump transmits the energy for the liqui

11、d only part, the impeller with the bond fixation on the axis, leads revolving along with the axis by the prime mover, passes to through the leaf blade prime mover's energy the liquid.</p><p>　　Impeller c

12、lassification: </p><p>　　①According to liquid inflow classification: Single suction impeller </p><p>　　(in impeller's one side has an entrance) and double attracts the impeller (liquid from

13、impeller's lateral symmetry liudao impeller passage). </p><p>　?、贗s opposite according to the liquid in centerline's flow direction classification: Runoff type impeller, axial-flow propeller and inte

14、rflow type impeller. </p><p>　?、跘ccording to impeller's structural style classification: Shrouded impeller, open type impeller and semi-opened impeller.</p><p>　　3. Axis: Is transmits the me

15、chanical energy the important components, the  prime mover's torque passes to the impeller through it. The pump spindle is the pump rotor's major parts, on the axis is loaded with components and so on impeller,

16、axle sleeve, balance disc. The pump spindle depending on the both sides bearing supporting, makes the high speed rotation in the pump, thus the pump spindle in a big way wants the bearing capacity, to be wear-resisting,

17、to be anti-corrosive. Pump spindle's mat</p><p>　　4. Packing ring: Is installs in the rotation impeller and the static pump housing (center-section and guide vane's assembly) between packing assembly

18、. It is function is through controls between the two gap method, increases in the pump between the high and low pressure cavity the fluid flow resistance, reduces divulging. </p><p>　　5. Axle sleeve: The axl

19、e sleeve is uses for to protect the pump spindle, causes it not to corrode and the attrition. When necessity, the axle sleeve may replace. </p><p>　　6. Axis seals: The pump spindle and around packing box bet

20、ween end cover's installs short for axis to seal, mainly prevents in pump's liquid divulging and the air enters in the pump, achieves seals and prevents the air admission to cause the pump cavitation goal. the a

21、xis seals form: Namely has skeleton's rubber seal, the packing seal and the mechanical seal.</p><p>　　7. axial force balancing unit.</p><p>　　Third. Centrifugal pump's prime task paramet

22、er</p><p>　　1. Current capacity: Namely the pump in unit of time discharges the liquid quantity, usually indicated with the Unit of volume that mark Q, the unit has m3/h, m3/s, l/s and so on, </p><

23、;p>　　2. Lifting: The transportation unit weight's liquid (pump suction flange) (pump discharge flange) from the pump inlet place to the pump exit, its energy's increment, indicated with H, the unit is m.

24、 </p><p>　　3. Rotational speed: Pump's rotational speed is the pump each minute revolving number of times, expressed with N. Electrical machinery rotational speed N generally about 2900 n/min. </

25、p><p>　　4. Net positive suction head: Centrifugal pump's net positive suction head is expressed that pump's performance's main parameter,  uses the symbolic representation. </p><p>　　5

26、. Power and efficiency: Pump's power input is shaft power P, is also electric motor's output. Pump's output is the active power.</p><p>　　Fourth, pump proper energy loss</p><p>　　Pum

27、p mechanical energy which obtains from the prime mover, has a part to transform into the liquid energy, but another part because in the pump consumes loses. In the pump all losses may divide into the following several it

28、ems: </p><p>　　1. Hydraulic loss by the liquid in pump impact, the turbulent flow and the surface friction creates. The impact and the eddy current loss are because the liquid flow change direction produces.

29、 The liquid flows through the flow channel general meeting which contacts to present the surface friction, from this produces the energy loss is mainly decided by flow channel's length, the size, the shape, the surfa

30、ce roughness, as well as liquid speed of flow and characteristic.</p><p>　　2. Volumetric loss: volumetric loss was already obtained the energy liquid to have a part to flee the result which in the pump the c

31、lass and leaked outward. Pump's volumetric efficiency is 0.93～0.98 generally. Improves the packing ring and the seal structure, may reduce the leakage, raises the volumetric efficiency. </

32、p><p>　　3. Mechanical loss mechanical loss refers to the impeller lap side and the pump housing friction loss between the liquid, namely the disc loses, as well as pump spindle when packing, bearing and balanci

33、ng unit and so on mechanical part movement friction loss, generally before primarily.</p><p>　　Fifth, pump's speed change--Proportionality law</p><p>　　1. Centrifugal pump's speed change

34、: </p><p>　　A centrifugal pump, when its rotational speed change, its rated flow, lifting and the shaft power will have the change according to the certain proportion relations. At present, uses the frequenc

35、y conversion velocity modulation electrical machinery to realize centrifugal pump's speed change, is a new important energy conservation way.</p><p>　　2. proportionality law expression:</p><p&

36、gt;　　In the formula, Q, H, N-- pump's rated flow, lifting and shaft power The subscript 1,2 express the different rotational speed separately </p><p>　　n-- rotational speed</p><p>　　Sixth, c

37、entrifugal pump's ratio rotation </p><p>　　Compared to the rotation is the comprehensive parameter which derives by the law of similarity, it is the operating mode function, to a pump, the different oper

38、ating mode has differently compared to the rotation, for ease of carries on the comparison to the different type pump's performance and the structure, the application optimum condition (the peak efficiency spot) the

39、ratio rotation represents this pump. </p><p>　　When chooses the pump, may according to job requirement Q, H and unifies electrical machinery's rotational speed, calculates the ns number, determines pump&

40、#39;s type approximately. At that time, used the positive displacement pump generally, at that time, used the centrifugal pump, the interflow pump, the axial flow pump and so on.</p><p>　　Seventh,centrifugal

41、 pump's </p><p>　　cavitation andinspirationcharacteristic </p><p>　　1.Cavitation phenomenons </p><p>　　The pumping station transportation medium's liquid condition and the g

42、as are can transform mutually, the transformed condition is the pressure and the temperature. Under certain temperature, the liquid starts the critical pressure which vaporizes for the vaporization pressure. The temperat

43、ure is higher, the liquid vaporization pressure is higher. Pump when revolution, if its overflow part local region (for example impeller blade import later somewhere), the liquid absolute pressure drops when pu</p>

44、<p>　　2. Cavitation will cause serious results:</p><p>　　(1). has the vibration and the noise.</p><p>　　(2). is influential to pump's operating performance: When the cavitation develo

45、ps the certain extent, the  steam bubble produces massively, will stop up the flow channel, will cause pump's current capacity, lifting, the efficiency and so on obviously to drop.</p><p>　　(3). will ha

46、ve the destruction to flow channel's material quality: Is mainly nearby the leaf blade entrance the metal weary disintegration.</p><p>　　3. centrifugal pump's inspiration characteristic:</p>&

47、lt;p>　　(1). Pump has the cavitation basic condition is: Under leaf blade entrance lowest liquid flow pressure <= this temperature liquid vaporization pressure .</p><p>　　(2). effective net positive suc

48、tion head: The pump entry (potential head is the entire flood peak which zero) the liquid has subtracts the value which the vaporization delivery head remains only, with expression. </p><p>　　(3). pump essen

49、tial net positive suction head: Liquid flow from pump inlet to impeller in minimal pressure point of force K place complete energy loss, with expression. </p><p>　　(4). With and difference and relation: <

50、/p><p>　　>Pump not cavitation </p><p>　　= The pump starts the cavitation </p><p>　　< Pump serious cavitation </p><p>　　(5). regarding a pump, to guarantee that its s

51、afe operation does not have the cavitation, must the net positive suction head also be supposed to add a security allowance regarding the pump, therefore, pump's permission net positive suction head is: </p>&

52、lt;p><b>　　= </b></p><p>　　4. Enhances the centrifugal pump anti-cavitation performance the method to include: </p><p>　　(1). I mprovement machine pump structure, reduces, is machi

53、ne the pump design question. </p><p>　　(2). Enhancement installment effective net positive suction head. Most mainly the most commonly used method uses the irrigation inspiration installment. </p>&l

54、t;p>　　In addition, reduces the inspiration pipeline resistance loss as far as possible, reduces the liquid the saturated steam tension, namely when design inspiration pipeline selects caliber big as far as possible, l

55、ength short, the bend and valve few, transportation liquid temperature as far as possible low and so on measures, may enhance the installment the effective cavitation remainder.</p><p>　　5. axial force balan

56、cing unit</p><p>　　(1). axial force production reason </p><p>　?、貯round because the impeller the both sides the fluid pressure distributed situation different (wheel cap lateral pressure is low,

57、  wheel disk pressure high) causes axial force A1, its direction for from impeller back side direction impeller eye. </p><p>　?、赥he fluid flows in and flows out dynamical reaction A2 which impeller's di

58、rection and the speed different produce, its direction and A1 are opposite, therefore line shaft directive force A=A1-A2, the direction is ordinary and A1 same (general A2 is small).</p><p>　　(2). Axial forc

59、e balanced </p><p>　?、賃ses double attracts the type impeller: The impeller lateral symmetry, the fluid from the both sides inspiration, the axial force automatic counter-balance achieves balanced.</p>

60、<p>　?、贠pens the balancing hole or installs the compensating pipe: </p><p>　　A: Opens several balancing holes in the impeller wheel disk photograph well regarding the induction port place. </p>

61、<p>　　B: After order to avoid the balancing hole, because the mainstream is disturbed increases the hydraulic loss, may suppose the compensating pipe to replace the balancing hole, namely uses an acorn tube leading-

62、in point pressure to the wheel disk back side.</p><p>　?、踀ses the balanced leaf blade: Casts several radial direction muscle piece at the back of the leaf wheel disk, the  muscle piece drives at the back of

63、 the impeller in the gap fluid to accelerate to revolve, increases the centrifugal force, , thus causes at the back of the impeller the pressure obviously to reduce. </p><p>　?、躑sing thrust bearing withstan

64、ding axial force. Generally in the small single suction pump the thrust bearing may withstand the complete axial force, prevents the pump spindle to flee moves.</p><p>　　Eighth. centrifugal pump's operat

65、ing procedure </p><p>　　1. Centrifugal pump starts the inspection </p><p>　　(1) Electrical machinery overhaul, before connecting the shaft coupling, inspects electrical machinery's rotation

66、direction first to be whether correct. </p><p>　　(2) inspection pumps out the inlet line and the attached pipeline, the flange, the valve installs whether to meet the requirement, foot bolt and grounding to

67、be whether good, whether the shaft coupling does install.</p><p>　　(3) jigger inspection, rotates whether normally.</p><p>　　(4) inspection lubricating oil oil level is whether normal, refuels w

68、ithout the oil, and inspects the lubricating oil (fat) oil material nature.</p><p>　　(5) turns on various cooling water valve, and inspects the pipeline to be whether unimpeded. Attention cooling water not s

69、uitable oversized or too small, will create the waste oversized, too small, then the cooling performance will be bad. Generally the cooling current of water becomes the striation </p><p>　　(6) dozen of pumpi

70、ng's inlet valve, closes pump's outlet valve, and turns on the pressure gauge valve. </p><p>　　(7) inspection machine pump's seal condition and oil seal opening. attention: The hot oil pump wants

71、 evenly before the start preheating. </p><p>　　2. centrifugal pump's start </p><p>　　(1) all operates the inlet valve, closes the outlet valve, the starting dynamo.</p><p>　　(2)

72、, when the pump outlet pressure is bigger than the service pressure, inspects each work on six cylinders, turns on the outlet valve gradually.when </p><p>　　(3) starting dynamo, if the start or has time the

73、unusual sound, should the dump inspection, after eliminating the breakdown, immediately only then starts.when </p><p>　　(4) start, pays attention to the human not to face the shaft coupling, by against depar

74、ts offends somebody.</p><p>　　3. the centrifugal pump stops the pump to operate </p><p>　　(1) to close pump's outlet valve slowly.</p><p>　　(2) shuts off electrical machinery

75、9;s power source. </p><p>　　(3) closes the pressure gauge valve.</p><p>　　(4) parking, cannot stop the cooling water immediately, should pump's temperature only then cut off the water supply

76、 falling to 80 degrees below. </p><p>　　(5) according to the need, closes the inlet valve, the pump body blows off.</p><p>　　4. centrifugal pump operates when matters needing attention </p>

77、;<p>　　(1) centrifugal pump when revolution avoids the idle operation. </p><p>　　(2) avoids when closes the outlet valve the long time revolution. </p><p>　　(3) refuses the water used bat

78、tery charger.the </p><p>　　(4) centrifugal pump must in close in outlet valve's situation to start.</p><p><b>　　附錄二：中文翻譯</b></p><p><b>　　泵的概述</b></p&g

79、t;<p>　　泵是應(yīng)用非常廣泛的通用機(jī)械，可以說(shuō)是液體流動(dòng)之處，幾乎都有泵在工作。而且，隨著科學(xué)技術(shù)的發(fā)展，泵的應(yīng)用領(lǐng)域正在迅速擴(kuò)大，根據(jù)國(guó)家統(tǒng)計(jì)，泵的耗電量都約占全國(guó)總發(fā)電量的1/5,可見(jiàn)泵是當(dāng)然的耗能大戶。因而,提高泵技術(shù)水平對(duì)節(jié)約能耗具有重要意義。</p><p>　　一.離心泵的工作原理</p><p>　　驅(qū)動(dòng)機(jī)通過(guò)泵軸帶動(dòng)葉輪旋轉(zhuǎn)產(chǎn)生離心力,在離心力作用下,液體

80、沿葉片流道被甩向葉輪出口,液體經(jīng)蝸殼收集送入排出管。液體從葉輪獲得能量,使壓力能和速度能均增加,并依靠此能量將液體輸送到工作地點(diǎn)。</p><p>　　在液體被甩向葉輪出口的同時(shí),葉輪入口中心處形成了低壓,在吸液罐和葉輪中心處的液體之間就產(chǎn)生了壓差,吸液罐中的液體在這個(gè)壓差作用下,不斷地經(jīng)吸入管路及泵的吸入室進(jìn)入葉輪中。</p><p>　　二、離心泵的結(jié)構(gòu)及主要零部件</p&g

81、t;<p>　　一臺(tái)離心泵主要由泵體、葉輪、密封環(huán)、旋轉(zhuǎn)軸、軸封箱等部件組成,有些離心泵還裝有導(dǎo)輪、誘導(dǎo)輪、平衡盤等。</p><p>　　1.泵體:即泵的殼體,包括吸入室和壓出室。</p><p>　?、傥胧?它的作用是使液體均勻地流進(jìn)葉輪。</p><p>　?、趬撼鍪?它的作用是收集液體,并把它送入下級(jí)葉輪或?qū)蚺懦龉?與此同時(shí)降低液體的速度,

82、使動(dòng)能進(jìn)一步變成壓力能。壓出室有蝸殼和導(dǎo)葉兩種形式。</p><p>　　2．葉輪:它是離心泵內(nèi)傳遞能量給液體的唯一元件,葉輪用鍵固定于軸上，隨軸由原動(dòng)機(jī)帶動(dòng)旋轉(zhuǎn),通過(guò)葉片把原動(dòng)機(jī)的能量傳給液體。</p><p><b>　　葉輪分類:</b></p><p>　?、侔凑找后w流入分類：?jiǎn)挝~輪（在葉輪的一側(cè)有一個(gè)入口）和雙吸葉輪（液體從葉輪的兩

83、側(cè)對(duì)稱地流到葉輪流道中）。</p><p>　?、诎凑找后w相對(duì)于旋轉(zhuǎn)軸線的流動(dòng)方向分類：徑流式葉輪、軸流式葉輪和混流式葉輪。</p><p>　?、郯凑杖~輪的結(jié)構(gòu)形式分類:閉式葉輪、開(kāi)式葉輪和半開(kāi)式葉輪。</p><p>　　3．軸:是傳遞機(jī)械能的重要零件,原動(dòng)機(jī)的扭矩通過(guò)它傳給葉輪。泵軸是泵轉(zhuǎn)子的主要零件，軸上裝有葉輪、軸套、平衡盤等零件。泵軸靠?jī)啥溯S承支承，在

84、泵中作高速回轉(zhuǎn)，因而泵軸要承載能力大、耐磨、耐腐蝕。泵軸的材料一般選用碳素鋼或合金鋼并經(jīng)調(diào)質(zhì)處理。</p><p>　　4.密封環(huán):是安裝在轉(zhuǎn)動(dòng)的葉輪和靜止的泵殼（中段和導(dǎo)葉的組合件）之間的密封裝置。其作用是通過(guò)控制二者之間間隙的方法，增加泵內(nèi)高低壓腔之間液體流動(dòng)的阻力，減少泄漏。</p><p>　　5.軸套：軸套是用來(lái)保護(hù)泵軸的，使之不受腐蝕和磨損。必要時(shí)，軸套可以更換。</p&

85、gt;<p>　　6.軸封：泵軸和前后端蓋間的填料函裝置簡(jiǎn)稱為軸封，主要防止泵中的液體泄漏和空氣進(jìn)入泵中，以達(dá)到密封和防止進(jìn)氣引起泵氣蝕的目的。</p><p>　　軸封的形式：即帶有骨架的橡膠密封、填料密封和機(jī)械密封。</p><p>　　7.軸向力的平衡裝置.</p><p>　　三.離心泵的主要工作參數(shù)</p><p>　

86、　1.流量:即泵在單位時(shí)間內(nèi)排出的液體量,通常用體積單位表示,符號(hào)Q,單位有m3/h,m3/s,l/s等,</p><p>　　2.揚(yáng)程:輸送單位重量的液體從泵入口處(泵進(jìn)口法蘭)到泵出口處(泵出口法蘭),其能量的增值,用H表示,單位為m.</p><p>　　3.轉(zhuǎn)速:泵的轉(zhuǎn)速是泵每分鐘旋轉(zhuǎn)的次數(shù),用N來(lái)表示。電機(jī)轉(zhuǎn)速N一般在2900轉(zhuǎn)/分左右。</p><p>

87、;　　4.汽蝕余量:離心泵的汽蝕余量是表示泵的性能的主要參數(shù),用符號(hào)表示。</p><p>　　5.功率與效率:泵的輸入功率為軸功率P,也就是電動(dòng)機(jī)的輸出功率。泵的輸出功率為有效功率。</p><p><b>　　四、泵內(nèi)能量損失</b></p><p>　　泵從原動(dòng)機(jī)獲得的機(jī)械能，只有一部分轉(zhuǎn)換為液體的能量，而另一部分則由于泵內(nèi)消耗而損失。

88、泵內(nèi)所有損失可分為以下幾項(xiàng)：</p><p>　　1.水力損失 由液體在泵內(nèi)的沖擊、渦流和表面摩擦造成的。沖擊和渦流損失是由于液流改變方向所產(chǎn)生的。液體流經(jīng)所接觸的流道總會(huì)出現(xiàn)表面摩擦，由此而產(chǎn)生的能量損失主要取決于流道的長(zhǎng)短、大小、形狀、表面粗糙度，以及液體的流速和特性。</p><p>　　2.容積損失 容積損失是已經(jīng)得到能量的液體有一部分在泵內(nèi)竄流和向外漏失的結(jié)果。泵的容積效率一

89、般為0．93～0．98。改善密封環(huán)及密封結(jié)構(gòu)，可降低漏失量，提高容積效率。</p><p>　　3.機(jī)械損失 機(jī)械損失指葉輪蓋板側(cè)面與泵殼內(nèi)液體間的摩擦損失，即圓盤損失，以及泵軸在盤根、軸承及平衡裝置等機(jī)械部件運(yùn)動(dòng)時(shí)的摩擦損失，一般以前者為主。</p><p>　　五、泵的變速--比例定律</p><p><b>　　1.離心泵的變速:</b>

90、;</p><p>　　一臺(tái)離心泵,當(dāng)它的轉(zhuǎn)速改變時(shí),其額定流量、揚(yáng)程和軸功率都將按一定比例關(guān)系發(fā)生改變。目前,采用變頻調(diào)速電機(jī)來(lái)實(shí)現(xiàn)離心泵的變速,是一條新的重要的節(jié)能途徑。</p><p>　　2.比例定律的表達(dá)式:</p><p>　　式中,Q、H、N——泵的額定流量、揚(yáng)程和軸功率</p><p>　　下標(biāo)1,2分別表示不同的轉(zhuǎn)速<

91、;/p><p><b>　　n——轉(zhuǎn)速</b></p><p>　　六、 離心泵的比轉(zhuǎn)數(shù)</p><p>　　比轉(zhuǎn)數(shù)是由相似定律導(dǎo)出的綜合性參數(shù)，它是工況的函數(shù)，對(duì)一臺(tái)泵來(lái)說(shuō)，不同的工況就有不同的比轉(zhuǎn)數(shù)，為了便于對(duì)不同類型泵的性能與結(jié)構(gòu)進(jìn)行比較，應(yīng)用最佳工況（最高效率點(diǎn)）的比轉(zhuǎn)數(shù)來(lái)代表這臺(tái)泵。</p><p>　　在選泵時(shí)，

92、可根據(jù)工作需要的Q、H和結(jié)合電機(jī)的轉(zhuǎn)速，計(jì)算出ns數(shù)，大致確定泵的類型。當(dāng)時(shí),一般采用容積式泵, 當(dāng)時(shí),則采用離心泵、混流泵、軸流泵等。</p><p>　　七、離心泵的汽蝕與吸入特性</p><p><b>　　1.汽蝕現(xiàn)象</b></p><p>　　泵所輸送介質(zhì)的液體狀態(tài)和氣體是能夠相互轉(zhuǎn)化的，轉(zhuǎn)化的條件就是壓力和溫度。在一定溫度下，液體

93、開(kāi)始汽化的臨界壓力為汽化壓力。溫度越高，液體的汽化壓力越高。泵在運(yùn)轉(zhuǎn)時(shí)，若其過(guò)流部分的局部區(qū)域（如葉輪葉片進(jìn)口稍后的某處），液體的絕對(duì)壓力下降到所抽送液體當(dāng)時(shí)溫度下的汽化壓力時(shí)，液體便在該處開(kāi)始汽化，形成氣泡（氣泡內(nèi)部的壓力約等于汽化壓力）。這些氣泡隨液流向前運(yùn)動(dòng)至高壓區(qū)時(shí)，氣泡周圍的高壓液體使氣泡急劇地縮小以至凝結(jié)。在氣泡消失的同時(shí)，液體質(zhì)點(diǎn)以高速填充空穴，發(fā)生互相撞擊而形成強(qiáng)烈的水擊，使過(guò)流部件受到腐蝕和破壞。上述過(guò)程稱為汽蝕。&l

94、t;/p><p>　　2.汽蝕會(huì)引起的嚴(yán)重后果:</p><p>　　(1).產(chǎn)生振動(dòng)和噪音。</p><p>　　(2).對(duì)泵的工作性能有影響:當(dāng)汽蝕發(fā)展到一定程度時(shí),汽泡大量產(chǎn)生,會(huì)堵塞流道,使泵的流量、揚(yáng)程、效率等均明顯下降。</p><p>　　(3).對(duì)流道的材質(zhì)會(huì)有破壞:主要是在葉片入口附近金屬的疲勞剝蝕。</p>&

95、lt;p>　　3.離心泵的吸入特性:</p><p>　　(1).泵發(fā)生汽蝕的基本條件是:葉片入口處的最低液流壓力≤該溫度下液體的汽化壓力。</p><p>　　(2).有效汽蝕余量:泵進(jìn)口處（位置水頭為零）液體具有的全水頭減去汽化壓力水頭凈剩的值，用表示。 </p><p>　　(3).泵必需的汽蝕余量:液流從泵入口到葉輪內(nèi)最低壓力點(diǎn)K處的全部能量損失,用表

96、示。</p><p>　　(4).與的區(qū)別和聯(lián)系:</p><p>　　> 泵不汽蝕</p><p>　　= 泵開(kāi)始汽蝕</p><p>　　< 泵嚴(yán)重汽蝕</p><p>　　(5).對(duì)于一臺(tái)泵,為了保證其安全運(yùn)行而不發(fā)生汽蝕,對(duì)于泵的必須汽蝕余量還應(yīng)加一個(gè)安全裕

97、量,于是,泵的允許汽蝕余量為:</p><p><b>　　=</b></p><p>　　4.提高離心泵抗汽蝕性能的方法有:</p><p>　　(1).改進(jìn)機(jī)泵結(jié)構(gòu),降低,屬機(jī)泵設(shè)計(jì)問(wèn)題。</p><p>　　(2).提高裝置內(nèi)的有效汽蝕余量.最主要最常用的方法是采用灌注頭吸入裝置.</p><p

98、>　　此外，盡量減少吸入管路阻力損失，降低液體的飽和蒸汽壓，即在設(shè)計(jì)吸入管路時(shí)盡可能選用管徑大些，長(zhǎng)度短些，彎頭和閥門少些，輸送液體的溫度盡可能低些等措施，都可提高裝置的有效氣蝕余量。</p><p>　　5.軸向力的平衡裝置</p><p>　　(1).軸向力的產(chǎn)生原因</p><p>　　①葉輪前后兩側(cè)因流體壓力分布情況不同(輪蓋側(cè)壓力低,輪盤壓力高)引

99、起的軸向力A1,其方向?yàn)樽匀~輪背側(cè)指向葉輪入口。</p><p>　?、诹黧w流入和流出葉輪的方向和速度不同而產(chǎn)生的動(dòng)反力A2,其方向與A1相反,所以總軸向力A=A1-A2,方向一般與A1相同(一般A2較小)。</p><p>　　(2).軸向力的平衡</p><p>　?、俨捎秒p吸式葉輪:葉輪兩側(cè)對(duì)稱,流體從兩端吸入,軸向力自動(dòng)抵消而達(dá)到平衡。</p>

100、<p>　?、陂_(kāi)平衡孔或裝平衡管:</p><p>　　A:在葉輪輪盤上相對(duì)于吸入口處開(kāi)幾個(gè)平衡孔。</p><p>　　B:為避免開(kāi)平衡孔后,因主流受擾動(dòng)而增加水力損失,可設(shè)平衡管代替平衡孔,即采用一小管引入口壓力至輪盤背側(cè)。</p><p>　　③采用平衡葉片:在葉輪盤背面鑄幾條徑向筋片,筋片帶動(dòng)葉輪背面間隙內(nèi)的流體加速旋轉(zhuǎn),增大離心力,從而使