双吸离心泵叶片载荷特性及其应用研究

发布时间：2017-12-31 05:22

本文关键词：双吸离心泵叶片载荷特性及其应用研究　出处：《中国农业大学》2015年博士论文　论文类型：学位论文

【摘要】：在水泵反问题设计方法中,叶片载荷将叶片形状与水泵内部流动特性联系在一起,目前还没有明确的选取方法。本文以比转速在90～180内的双吸离心泵为研究对象,对叶片载荷特性与双吸离心泵性能的关系进行了深入研究。首先分析了叶片载荷曲线在反问题设计方法中的应用过程,建立了三段式载荷曲线的求解方程和计算步骤。在此基础上,针对12台性能优良的双吸离心泵,进行了流动特性分析与叶片载荷曲线的反演计算,建立了载荷曲线参数与水泵水力性能之间的关系。研究发现,前盖板主加载点位置过于靠前会使水泵进口压力降低,直接影响水泵的汽蚀性能；前、后盖板后加载点过于靠前,会使叶轮后部做功能力不足,降低效率,过于靠后则会使叶轮出口处压力梯度较大,产生明显的二次流,影响泵的效率和压力脉动。其中,具有高抗汽蚀特性的双吸离心泵,前盖板主加载点在相对轴面流线坐标上主要分布在0.24～0.65范围内,并随比转速的增加而减小；具有高效率特性的双吸离心泵,前盖板后加载点主要分布在区间0.59～9.75范围内,后盖板后加载点主要分布在0.53～0.67范围内,均随比转速的增加而增大：具有低压力脉动特性的双吸离心泵,前盖板后加载点主要分布在0.75～0.86范围内,后盖板后加载点主要分布在0.69--0.86范围内,均随比转速的增加而减小。基于上述载荷曲线特征,形成了用于指导双吸离心泵叶轮设计的"RNG载荷曲线”。针对在反问题设计过程中出现的叶片扭曲问题,提出了一种在满足前盖板和后盖板载荷曲线要求的前提下,通过调整叶片轴面截线形状,来控制叶片整体平滑度的叶片调控方法——"RNG叶片调控方法”。该方法将所有轴面截线均为下凸型圆弧,圆弧半径按指定规律由进口向出口逐渐增加。由此方法得到的叶片,表面光顺,整体水力性能好。将所建立的RNG载荷曲线和RNG叶片调控方法相结合,形成了用于指导双吸离心泵叶轮水力设计的"RNG加载技术”。根据该项技术,分别以提高效率和降低压力脉动为优化目标,对两台双吸离心泵叶轮进行了改型优化设计。其中,以提高效率为目的叶轮经改型设计后,最优点效率提高了2.4个百分点；以降低压力脉动为目标的叶轮经改型设计后,在设计工况下压力脉动峰峰值降低了约50%,研究成果已经在大型引黄灌溉工程等实际泵站中应用。本文研究成果为双吸离心泵叶轮设计提供了一种新的途径,对提高双吸离心泵效率和运行稳定性具有重要工程意义和应用价值。
[Abstract]:In the inverse problem design method of water pump, the blade load is used to link the blade shape with the flow characteristics of the pump. At present, there is no clear selection method. In this paper, the relationship between the characteristics of blade load and the performance of double suction centrifugal pump is studied. Firstly, the application process of blade load curve in inverse problem design method is analyzed, and the solving equation and calculation steps of three-stage load curve are established. On this basis, 12 dual-suction centrifugal pumps with excellent performance are designed. The relationship between the parameters of the load curve and the hydraulic performance of the pump is established by the analysis of the flow characteristics and the inverse calculation of the blade load curve. If the main loading point of the front cover plate is located too far forward, the inlet pressure of the pump will be reduced, which will directly affect the cavitation performance of the pump. If the front and rear cover plate load point is too forward, the work capacity behind the impeller will be insufficient, and the efficiency will be reduced, and the pressure gradient at the outlet of the impeller will be larger and the secondary flow will be obvious. The efficiency and pressure fluctuation of the pump are affected. Among them, the main loading point of the front cover plate is mainly distributed in the range of 0.24 ~ 0.65 in the relative axial streamline coordinates of the double suction centrifugal pump with high cavitation resistance. And decrease with the increase of specific speed. For the double suction centrifugal pump with high efficiency, the front and back loading points are mainly distributed in the range of 0.59 ~ 9.75, and the rear cover plate's loading points are mainly in the range of 0.53 ~ 0.67. All increase with the increase of specific speed: the double suction centrifugal pump with low pressure pulsation characteristics, the front cover plate after loading point is mainly distributed in the range of 0.75 ~ 0.86. The back loading points of the back cover plate are mainly distributed in the range of 0.69 to 0.86, and all of them decrease with the increase of specific rotational speed, which is based on the above characteristics of load curve. The "RNG load curve" was formed to guide the design of double suction centrifugal pump impeller. In order to solve the problem of blade distortion in the process of inverse problem design, a new method is proposed to adjust the shape of blade axial section on the premise that the load curve of front cover plate and back cover plate can be satisfied. The blade control method "RNG blade control method" is used to control the overall smoothness of the blade. In this method, all axial section lines are convex circular arcs. The arc radius increases gradually from the inlet to the outlet according to the specified law. The blade obtained by this method has a smooth surface and good overall hydraulic performance. By combining the established RNG load curve with the RNG blade control method, a "RNG loading technique" was formed to guide the hydraulic design of the double suction centrifugal pump impeller. In order to improve efficiency and reduce pressure pulsation, two double suction centrifugal pump impellers were modified to optimize the design of the impeller, in which, the purpose of the impeller was to improve the efficiency of the impeller after the modification design. The best efficiency increased by 2.4%; The impeller with the aim of reducing pressure pulsation has been modified and the peak value of pressure pulsation has been reduced by about 50. The research results have been applied in large irrigation projects of Yellow River diversion and other practical pumping stations. The research results in this paper provide a new way for the design of double suction centrifugal pump impeller. It is of great engineering significance and application value to improve the efficiency and operation stability of double suction centrifugal pump.
【学位授予单位】：中国农业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TH311

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