【作者】 徐朝晖；

【导师】 陈乃祥；

【作者基本信息】 清华大学 ， 流体机械及工程， 2004， 博士

【摘要】 由于高速离心泵结构紧凑、造价低,在航天等工程领域中有着广泛的应用前景。但随着转速的提高,其运行稳定性愈来愈得到重视,流体诱发压力脉动已成为无法回避的问题。如何在设计阶段预估高速离心泵全流道内流体诱发的压力脉动,优化设计,也就成为一重要课题,这对有效降低高速离心泵的运行风险具有十分重要的意义。本研究为了分析高速离心泵中诱导轮叶片出现裂纹的原因,利用湍流雷诺方程、标准湍流模型、RNG 湍流模型及滑移网格技术,采用自行发展的Fortran语言程序计算了高速离心泵内诱导轮、导流支座和离心叶轮的三维定常湍流流动,利用Fluent程序计算了高速离心泵内全流道的三维非定常湍流流动。高速离心泵内的三维定常湍流流动计算结果不仅为诱导轮内部流场诊断提供数据,还指出了该泵中存在的部件设计问题。但分部件的定常流动计算结果难以透彻分析诱导轮叶片断裂的原因。故本文利用三维非定常流动结果反映了高速离心泵中三级动静干扰对流体流动产生的非定常影响。以此为基础得到了高速离心泵流道内的流体诱发压力脉动。此外导叶扩压器与离心泵叶轮间隙内的流体非定常流动特性充分反映了旋转动轮与静轮间动静干扰问题。为了验证三维定常与非定常湍流计算结果的可信度,本文对所研究的高速离心泵进行了能量试验与压力脉动试验。能量试验测量了高速离心泵在不同工况下的净扬程及工作流量,压力脉动试验测量了诱导轮内的压力脉动信号。经比较,试验结果与计算结果吻合较好。本文利用局部涡动力学法、涡结构分析法和过流部件的损失分析诊断了高速离心泵内流体诱发振动的原因,并校核了传统的损失经验计算公式。涡动力学法是从叶片设计的角度分析诱导轮叶片产生裂纹的涡动力学根源,而涡结构分析法是利用正则化螺旋度法计算各轴向截面的涡结构及涡核位置的分布,来分析诱导轮内的流动。本文将流体压力脉动作为诱导轮叶片动态应力分析的外载荷,利用间接顺序法和模态叠加法计算了诱导轮叶片的三维非定常动态应力分布,其结果进一步说明了叶片出现裂纹的原因。更多还原

【Abstract】 Due to its low price, small size and appropriated structure, the high-speed pump has widely been applied in spaceflight engineering. But with increasing speed, the flow-induced pressure fluctuation of the pump is a severe problem. Cracks in the inducer blades of some foreign spaceflight engines and the high-speed pump of the present work have been found, which are caused by flow-induced pressure fluctuation. Optimizing design and predicting the flow-induced pressure fluctuation of high-speed pump, which is useful to reduce the operation risk of high-speed pump, is a vital subject. To analyze the reason of cracks in the inducer blades, the Reynolds averaged N-S equations, the standard turbulence model, the RNG turbulence model, the sliding mesh technique, Fortran language program and Fluent program have been used to simulate the three-dimensional steady and unsteady turbulent flow in high-speed pump. The calculated results of three-dimensional steady flow not only offer the based dataset for flow diagnoses in the pump, but also indicate the design problem in some parts of the pump as well. The three-dimensional unsteady flow results reflected the influence of three-stage interaction coupled by rotor-stator row to the flow. And based on the results, the flow-induced pressure fluctuation of the high-speed pump is obtained. In the internal flow field of the inducer, the pressure fluctuation frequency of every point was kept consistency coinciding with three times passing frequency of the inducer. In addition, the flow characters in the gap between the static vane and impeller show completely the issue of interaction of rotor-stator rows.The experiment of energy and pressure fluctuation character on the pump is processed in a high-speed pump tig, so that the calculated results are validated. The net head and the discharge of the pump are measured in the energy experiment. And pressure fluctuation in the inducer is measured in the pressure fluctuation experiment. <WP=6>The experimental results are coincidence with the calculated results.In order to diagnose the reason of pressure fluctuation caused by flow in the high-speed pump and to check the validity of loss formulation, vorticity method, normalization helicity and the loss calculation of main part in the pump are presented in the paper. The vorticity method is used to analyze the reason of blades crack in the inducer from vorticity dynamics. And the normalization helicity method is used to calculate the vortex structure in different cross section, and analyze the internal flow field in the inducer.Finally, to analyze cracks on the inducer blades, the pressure fluctuation forces have been used as external force when three-dimensional unsteady stress calculation are conducted. The indirect sequentially coupled physical analysis method and the modal analysis method have been used to calculate the unsteady stress. From the results, the reason of the crack was found.更多还原