译文：
1、前言 蒸汽喷射真空泵抽气量大、工作范围宽、结构简单、没有相对运动的部件,是一种用途广泛的真空设备,主要应用于除气、脱色、干燥、脱臭、蒸馏、制冷及输送等方面。特别是其对吸入气体无选择性,在食品生产、石油化工、油脂加工、聚酯生产、含有机溶剂的物料浓缩等场合,与机械真空泵(油泵)相比显示出{zy1}的优点。本文对蒸汽喷射真空泵的影响因素进行了分析,以便为其广泛应用提供参考。 2、蒸汽喷射真空泵的工作原理 蒸汽喷射真空泵是利用流体流动时的静压能与动能相互转换的气体动力学原理来形成真空。具有一定压力的水蒸汽通过拉瓦尔喷嘴喉径时达到声速,到喷嘴的扩散部时,静压能全部转化为动能,达到超声速,同时喷嘴出口处形成真空,被抽气体在压差的作用下,被抽入吸入室,和以超声速的蒸汽一边混合一边进入文丘里管,然后以亚声速从文丘里的扩散管排出,同时混合的气体速度逐渐降低,压力随之升高,而后从排出口排出。如果将几个喷射泵串联起来使用,泵与泵中间加入冷凝器使蒸汽冷凝,便可得到更高的真空度。整台蒸汽喷射真空泵由若干级泵体与冷凝器两大部分组成。各级泵体均由喷嘴、入室及扩压器组成,喷嘴可以是单只,也可以是多只,喷嘴一般采用不锈钢材料,吸入室和扩压器等其它部件可采用不锈钢、铸铁及碳钢等材料。 3、影响真空泵能力的主要因素研究 3.1、对工作蒸汽及其干度的研究 蒸汽压力偏低及压力波动均对真空泵的能力有较大影响,因此蒸汽压力不应低于要求的工作压力,但所用真空泵结构设计已定型,过多提高蒸汽压力并不会增加抽气量及真空度。另外,要确保锅炉供给的蒸汽压力稳定,{zh0}用一台锅炉专门给蒸汽喷射泵提供工作蒸汽,这样蒸汽压力就不会出现波动,真空泵性能稳定。 蒸汽的干度对真空泵的性能也有较大影响,其中含水会引起真空波动,含水过多甚至会抽不起真空,通常的作法是在汽包前加装汽水分离器以获得干度较高的工作蒸汽,同时对蒸汽管路进行有效保温。为取得{zj0}的工作效益,为喷射真空泵提供的工作蒸汽应为5℃~10℃的过热蒸汽。特别是五级泵,对蒸汽的品质要求非常高,含微量水分都可能引起喷嘴的冰塞,造成开第五级喷射器真空度反而下降或没有作用。 3.2、对循环冷却水要求的研究 冷却水供量不足,冷凝器会发热,气流声音变大,真空度迅速下降,甚至蒸汽会返入抽气管。对于列管间冷式冷凝器,应保证供水压力为0.2MPa,供水量应比实际的用量稍微大一点,这样用水的波动会比较平稳。另外,为避免供水量不稳定而引起真空波动,{zh0}采用单独的循环水系统对真空泵的冷凝器进行供水。 冷却水温太高,真空泵能力会下降,有时甚至抽不起真空,一般不超过32℃。另外,冷却水温越高,耗用的蒸汽量越多。 冷却水质对真空泵能力的影响也是一个不可忽视的因素,如果水质差,硬度高,会造成冷凝器积垢甚至堵塞,严重影响热交换性能,使蒸汽难于冷凝,从而影响真空度。所以应保证循环冷却水为纯净的软化水。 3.3、对真空泵系统密封要求的研究 真空泵处于极限状态时,第1级排出的水很少,有时甚至没有。因此,第1级泵有大量水排出,可以认为是系统有泄漏。通常的漏气原因有:垫片没装、装错或损坏,螺栓未拧紧,法兰面损坏,焊缝有沙眼,接头(压力表、真空表等)未装好。 最通用的查漏方法是整个系统通入带压空气,用肥皂水涂在各处。如有泄漏,漏点会有气泡,有时甚至能听到泄漏的声音。检验是否漏气的最终要求是,用0.2MPa压缩空气对真空系统(包括泵体和大气腿)进行汽密性试验,24h压力下降量不超过4.8%。 3.4、对喷嘴要求的研究 喷嘴是影响真空泵性能的重要部件,存在的问题有:喷嘴装错、装歪、堵塞、损坏、腐蚀和泄漏,不管采取何种预防措施,喷嘴的堵塞在所难免。一方面由于安装蒸汽管道时,管道中残存的铁屑及焊渣会堵塞喷嘴;另一方面,真空泵系统停用时,蒸汽管道易生锈,锈斑在使用时掉落堵塞喷嘴。一般来说,第1、2级喷嘴孔径较大,不易堵塞,最易堵塞的是第3、4、5级的喷嘴。喷嘴是否堵塞可通过触摸泵头和冷凝器的温度来确认。 4、蒸汽喷射真空泵的故障处理 蒸汽喷射真空泵在使用过程中有时会出现抽真空时太长、真空度不稳定或达不到真空度要求的情况,必对故障查找原因、分析处理。通常要进行以下的故障分析: (1)真空测量装置(包括真空表、真空计、测试罩)是否有故障或失效; (2)工作蒸汽供应是否正常,包括压力、温度、干燥度、疏水情况、波动情况等,尤其要检查压力表在长时间使用后读数是否准确; (3)循环冷却水供应是否正常,包括水温、水压、水量、水质等; (4)生产系统是否出现异常,包括系统泄漏、系统产生过量气体、工艺设备性能下降等; (5)真空泵系统本身是否有故障,包括泵系统泄漏、喷嘴堵塞或损坏、喉管直径磨损增大、扩压管的收缩段和排出口积垢、大气腿泄漏或积垢堵塞、冷凝器积垢堵塞、抽气管道积液等。

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原文：
1 Introduction Steam jet vacuum pump capacity, working range, simple structure, there is no relative motion of parts, is a widely used vacuum equipment, mainly used in addition to gas, bleaching, drying, deodorization, distillation, refrigeration, and transportation and so on. In particular, its non-selective gas inhalation, in food production, petrochemicals, oil processing, polyester production, concentration of materials containing organic solvents such occasions, and mechanical vacuum pump (oil pump) showed remarkable advantages compared to. In this paper, the influence of steam jet vacuum pump factors are analyzed in order to provide a reference for its wide application. 2, the working principle of steam jet vacuum pump Steam jet vacuum pump is used when the fluid flow between the static pressure change with the kinetic energy of gas dynamics to form a vacuum. A certain pressure of water vapor through the Laval nozzle throat diameter reached the speed of sound, to the proliferation of the Department of the nozzle, the static pressure can all be converted into kinetic energy, reaching supersonic, while the vacuum formed at the nozzle exit, was pumping gas at the pressure under the action of , have been drawn into the suction chamber, and a supersonic speed, the steam side of the mixed side into the Venturi tube, and then subsonic from the Venturi diffuser discharge, while a mixed gas velocity decreases, pressure, with an increasing, then from the discharge outlet discharge. If you use several jet pumps connected in series, pump and pump condenser to the steam condensate to join the middle can be a higher vacuum. Full steam jet vacuum pump and condenser pump consists of several levels of two major components. Levels by the pump nozzle, burglary, and the composition of diffuser and nozzle can be alone, it can be more just, usually stainless steel nozzle, suction chamber and the diffuser can be used, and other parts of stainless steel, cast iron and carbon steel and other material. 3, the main factors affect the ability of vacuum 3.1 The work of the steam and dry Degree Low vapor pressure and pressure fluctuations on the pump's ability to have greater impact, so the vapor pressure should not be less than the required working pressure, but the structural design has been finalized with a vacuum pump, too much steam pressure increase would not increase the volume and the vacuum exhaust degree. In addition, to ensure the supply of steam boiler pressure stability, it is best to use a steam boiler dedicated to steam jet pump to provide work, so that the steam pressure will not fluctuate, vacuum pumps and stable performance. Dryness of steam on the vacuum pump was also affected, of which water will cause the vacuum fluctuations, excessive water pumping can not afford even a vacuum, the usual practice is pre-installed in the drum separator for dry high degree of working steam, while the effective insulation of steam pipes. To obtain the best effectiveness of the work, the work provided for the steam jet vacuum pump should be 5 ℃ ~ 10 ℃ of superheated steam. In particular, five pumps, steam quality requirement is very high, contained traces of moisture can cause ice jam the nozzle, resulting in a fifth-level jet vacuum the worse or no effect. 3.2, on the circulation of cooling water required Insufficient supply of cooling water, condenser will heat, air sound bigger, the vacuum decreased rapidly, and even back into the exhaust steam pipe. The inter-cooled condenser tube, should ensure that water pressure is 0.2MPa, water supply should be slightly larger than the actual amount that it would be more stable water fluctuations. Moreover, to avoid water supply caused by instability in the vacuum fluctuations, the best use of a separate circulating water system's condenser water pumps. Cooling water temperature is too high, vacuum pump capacity will decline, and sometimes can not afford to vacuum pumping, generally no more than 32 ℃. In addition, the higher the cooling water temperature, the more the consumption of steam. Cooling water capacity of the vacuum pump is also a factor can not be ignored, if poor water quality, high hardness, will cause the condenser fouling or blockage, seriously affect the heat exchange performance, making it difficult condensing steam, thus affecting the vacuum. Therefore, we should ensure that cooling water is pure demineralized water. 3.3, on the sealing requirements of vacuum pump system Vacuum in the limit state, the first a small discharge of water, sometimes not. Therefore, the first a large number of water discharge pump can be considered the system for leaks. Usually the leakage of factors: gasket not installed, install the wrong or damaged, bolts not tightened, the flange surface damage, weld with trachoma, joints (pressure gauges, vacuum table, etc.) is not installed well. The most common leak is to access the system with pressure air, coated with soap and water everywhere. If leaks, bubbles will leak, and sometimes can hear the sound leakage. Test whether the leak of the final requirement is that the vacuum with 0.2MPa compressed air system (including pump and air leg) for vapor tightness test, 24h pressure drop does not exceed 4.8%. 3.4, the requirements of the nozzle Nozzle is an important component affecting pump performance, the problems are: nozzle placed incorrectly installed distorted, blocked, damaged, corrosion and leakage, no matter what preventive measures to plug the nozzle is inevitable. On the one hand because steam pipe installed, the pipe and welding slag remaining iron will plug the nozzle; other hand, the vacuum pump system out, the steam pipe rust, rust plug in using drop nozzles. In general, larger nozzle diameter 1,2 level, easy to plug, plug is most likely the first level of the nozzles 3,4,5. Nozzle is blocked and the pump head can touch the condenser temperature to confirm. 4, steam jet vacuum pump troubleshooting Steam jet vacuum pump in the course of time can sometimes be too long vacuum, vacuum vacuum instability or fail situation demands, will find the reasons of the failure, analysis. Usually the fault of the following: (1) vacuum measuring devices (including the vacuum table, vacuum gauges, test cover) whether there is malfunction or failure; (2) working steam supply is normal, including pressure, temperature, dryness, drainage conditions, fluctuations, etc., particularly in a long time to check the pressure gauge reading is accurate after use; (3) cooling water supply is normal, including temperature, pressure, water quantity, water quality, etc.; (Four) whether there is abnormal production systems, including system leaks, the system produces excess gas, process equipment performance degradation, etc.; (5) vacuum pump system itself is faulty, including the pump system leaks, blocked or damaged nozzle, pipe diameter, increasing wear and tear, contraction of the diffuser pipe outlet section and fouling, air leakage or leg plug fouling, condenser product plug fouling, exhaust pipes effusions.