离心泵平衡孔泄漏量对轴向力特性影响的研究

发布时间：2018-09-07 12:11

【摘要】：开平衡孔双密封环叶轮具有平衡大部分轴向力的特性,目前仍普遍应用在离心泵中。平衡孔液体的泄漏量对这种叶轮平衡轴向力的能力有着决定性的作用,这不仅影响离心泵的容积效率、轮阻损失和泵腔内的液体压力分布,而且对轴向力的计算都有较大的影响,因此研究平衡孔液体的泄漏量的测量及计算方法就显得格外必要。本文设计了通过调节平衡腔液体压力来测量平衡孔液体泄漏量的试验装置,利用试验测量和数值分析的方法,测试不同平衡孔孔径的试验泵的平衡孔液体泄漏量、泵性能、泵腔和平衡腔液体压力,深入研究了平衡孔液体泄漏量及泄漏量系数的特性及其对泵性能、泵腔压力分布以及平衡腔区域轴向力影响规律。本文主要研究内容如下:1.针对平衡孔孔径对泵性能影响的问题,以IS80-50-315型离心泵为研究对象,通过设计的平衡孔套可以实现在同一个叶轮上改变平衡孔孔径,在不同平衡孔孔径条件下,测量了不同运行工况的试验泵的流量,进口压力、出口压力、转速和输入功率,得到了不同平衡孔孔径和运行工况下试验泵的性能曲线,试验结果表明,不同孔径的平衡孔条件下,试验泵的性能曲线变化规律都相似,且增大平衡孔孔径会影响泵的性能,使其扬程减小,输入功率增大,效率降低,在平衡孔的孔径小于6 mm时,改变平衡孔孔径对离心泵性能影响较小,当平衡孔的孔径大于6 mm时,改变平衡孔孔径对泵性能影响较大。在相同泵扬程下,泵进口液体压力最大差值仅为2.12 kPa,说明平衡孔孔径对泵进口液体压力影响很小。2.针对测量平衡孔实际泄漏量的难题,设计了通过调节平衡腔液体压力来测量平衡孔液体泄漏量装置,测量了在不同运行流量条件下,不同平衡孔孔径的泄漏量,得到了对应的平衡孔泄漏量系数,并引入无量纲的比面积和扬程系数。试验结果表明,平衡孔液体的泄漏量及泄漏量系数与比面积的关系曲线变化具有明显的规律性,平衡孔孔径和比面积增加,平衡孔液体的泄漏量随之增加,其流量系数随之减小;在相同比面积条件下,离心泵的扬程系数越大,通过平衡孔的液体的泄漏量越大,而平衡孔泄漏量系数越小。分析得到的不同扬程系数下,平衡孔流量系数与比面积的关系曲线为计算相似泵的平衡孔泄漏量提供了新的方式。3.试验测量了试验泵在不同工况下平衡腔的液体压力,得到了不同工况下平衡腔区域的轴向力以及轴向力系数。试验结果表明,在相同平衡孔孔径条件下,平衡腔区域的轴向力随离心泵扬程增加而增加;在相同的扬程条件下,平衡孔孔径增大,平衡腔区域轴向力明显降低,但平衡腔区域轴向力的降幅收窄。平衡腔区域的轴向力系数与比面积的关系曲线是非线性曲线,在比面积小于2.5时,其轴向力系数随比面积增大而迅速减小;比面积位于2.5至4.5之间时,轴向力系数曲线趋于平坦,比面积大于4.5时,轴向力系数曲线几乎平行于横坐标。4.建立了试验泵在不同平衡孔孔径条件下的不同运行流量的45个计算模型,通过对试验泵的全流道模型进行了数值计算,得到了试验泵在不同工况下的平衡孔泄漏量和平衡腔轴向力的模拟值,以及平衡孔附近区域和平衡腔的液体速度和压力分布,并与试验结果进行了对比分析。分析得到,试验泵在同一平衡孔孔径的条件下,其平衡孔液体泄漏量的试验值与模拟值都随泵运行流量的增加而逐渐减小;同一运行流量的条件下,随着叶轮平衡孔孔径增大,平衡腔轴向力逐渐减小;平衡孔的存在使平衡腔压力相较于无平衡孔时有数量级的降低,但平衡孔的使用使叶片进口处压力分布变得混乱,叶片背面低压区增大,且平衡孔孔径越小,通过平衡孔液体的流动速度越大。
[Abstract]:The double-ring impeller with balanced holes has the characteristic of balancing most of the axial forces, and is still widely used in centrifugal pumps. The leakage of the balanced holes plays a decisive role in the ability of the impeller to balance the axial forces, which not only affects the volumetric efficiency of the centrifugal pump, the loss of wheel resistance and the distribution of liquid pressure in the pump chamber, but also affects the axial direction. It is necessary to study the measurement and calculation method of the liquid leakage in the balance hole because the calculation of force has great influence. In this paper, a test device is designed to measure the liquid leakage in the balance hole by adjusting the liquid pressure in the balance cavity. The test pump with different balance aperture is tested by means of experimental measurement and numerical analysis. The characteristics of the liquid leakage rate and leakage coefficient of the balanced orifice and their effects on the pump performance, the pressure distribution in the pump cavity and the axial force in the balanced chamber area are studied in detail. Taking IS80-50-315 centrifugal pump as the research object, the balance aperture can be changed on the same impeller by designing the balance aperture sleeve. Under the condition of different balance aperture, the flow rate, inlet pressure, outlet pressure, rotational speed and input power of the test pump under different operation conditions are measured. The different balance aperture and operation worker are obtained. The experimental results show that the performance curves of the test pump are similar under the condition of balanced holes with different apertures, and the performance of the pump will be affected by the increase of balanced aperture, the head will be reduced, the input power will be increased, and the efficiency will be reduced. When the aperture of the balanced aperture is less than 6 mm, the change of the balance aperture will affect the performance of the centrifugal pump. When the hole diameter of the balance hole is larger than 6 mm, the change of the balance hole diameter has a great influence on the pump performance. At the same pump head, the maximum difference of the liquid pressure at the pump inlet is only 2.12 kPa, indicating that the balance hole diameter has little influence on the pump inlet liquid pressure. 2. Aiming at the difficult problem of measuring the actual leakage of the balance hole, the adjustment level is designed. The device for measuring the liquid leakage of the balance hole by the pressure of the liquid in the balance chamber is used to measure the leakage of the balance hole. The leakage coefficient of the balance hole is obtained by measuring the leakage of the liquid in the balance hole with different balanced aperture under different operating flow conditions. The relationship curve has obvious regularity, the balance hole diameter and specific area increase, the balance hole liquid leakage increases, its flow coefficient decreases; under the same area condition, the centrifugal pump head coefficient is bigger, the liquid leakage through the balance hole is bigger, and the balance hole leakage coefficient is smaller. The relationship between the balance hole flow coefficient and specific area provides a new way to calculate the balance hole leakage of similar pumps under different lift coefficients. Under the same balancing aperture, the axial force in the balancing chamber increases with the increase of the head of the centrifugal pump; under the same head condition, the axial force in the balancing chamber decreases obviously with the increase of the balancing aperture, but the decrease amplitude of the axial force in the balancing chamber area narrows. When the specific area is less than 2.5, the axial force coefficient decreases rapidly with the increase of specific area; when the specific area is between 2.5 and 4.5, the curve of axial force coefficient tends to be flat; when the specific area is larger than 4.5, the curve of axial force coefficient is almost parallel to abscissa. 4. A set of 45 meters of test pump under different balanced aperture conditions are established. Computational model, through the numerical calculation of the full-channel model of the test pump, the simulation values of the balance hole leakage and the axial force of the balance chamber under different working conditions, the liquid velocity and pressure distribution near the balance hole and the balance chamber are obtained, and compared with the experimental results. Under the condition of balanced aperture, the experimental and simulated values of liquid leakage in balanced aperture decrease with the increase of pump operating flow rate; under the condition of the same operating flow rate, the axial force of balanced chamber decreases with the increase of balanced aperture of impeller; the existence of balanced aperture makes the pressure of balanced chamber have an order of magnitude compared with that without balanced aperture. However, the pressure distribution at the inlet of the blade becomes confused and the low pressure area on the back of the blade increases with the use of the balancing orifice. The smaller the balancing orifice, the greater the liquid flow velocity through the balancing orifice.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TH311

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