基于环面叶栅的静叶clocking效应的研究

发布时间：2018-06-13 09:36

本文选题：轴流压气机 + 非定常作用　；参考：《上海交通大学》2012年硕士论文

【摘要】：叶轮机械内部流动是典型的强三维非定常流动,对这种流动的深入理解和研究对提高叶轮机械气动性能及工作可靠性有非常重要的意义。国内外大量的实验及数值分析发现时序效应可以带来气动效率的提高,但由于实验测量在高速旋转的叶轮机械内部测量的局限性,所以大多数情形都是通过数值分析来研究叶轮机械内部时序效应机理。过去的数值分析往往采用对流道进行约化的处理手法来研究时序效应,而时序效应作为一种由于上游叶片周向分布不均导致对下游的差异化影响,这样的处理往往难以让人信服。所以本文采用了一种全周向环面叶栅计算方法来研究时序效应。本文是以商业的CFD数值模拟为工具,针对试验用压气机及轴流透平模型,提出环面叶栅网格计算来研究轴流叶轮机械的时序效应:在50%叶高位置进行网格划分,并选取了一个2级(静/转/静/转)轴流实验用压气机进行了二维叶栅、三维单通道以及全流道环面叶栅非定常数值模拟,并就三者的计算结果进行的比较分析,发现全流道环面叶栅计算具有流场信息全优点。为了进一步了解轴向间距的改变对机器性能的影响,本文针对轴流压气机这一模型,通过改变第一级动叶在静叶间的轴向相对位置,来研究动叶相对轴向位置变化对时序效应的影响。同时针对一个Hannover大学多级透平中的2.5级(静/转/静/转/静)轴流透平,通过环面叶栅计算方法进行了流场计算,分析了clocking效应对2.5级轴流透平气动性能的影响。通过本文数值计算结果分析静叶在不同的时序位置下,附面层所受的不同扰动以及下游静叶壁面处附面层的影响情况,总结出时序效应的一些基本规律:(一)后排静叶受到上游来流尾迹的周向不均匀影响是产生时序效应的主要原因,动静交界处周期性变化的压力场所产生的势扰动的对下游叶片附面层的发展有显著影响。时序位置的改变,会使扰动产生有益迭加,从而减小了动叶表面的流动损失,从而实现气动效率的提高。(二)通过全通道环面叶栅计算结果证实了时序效应的前缘干涉理论:当上游静叶的尾迹冲击到叶片前缘,由于是低能流体的尾迹与同为低能流体的边界层发生掺混,其掺混损失小,对应气动效率就高,反之与主流高能流体的掺混损失大,气动效率低。关于环面叶栅网格计算这一方法,适用于周向分布不均的时序效应研究,并且不需要对叶片数目进行约化处理就能对所有流道进行非定常分析。这为使用较少的计算时间研究多级叶排连算成为可能,其非定常计算结果由于引入了多叶栅通道的计算,在各叶栅通道流场细节捕捉及反映各流道相互影响及压力波动上比单通道计算结果反映更加周全,结果可信度高,有一定的工程实用价值。
[Abstract]:The internal flow of impeller is a typical strong three-dimensional unsteady flow. It is very important to understand and study the flow in depth to improve the aerodynamic performance and reliability of impeller machinery. A large number of experiments and numerical analysis at home and abroad have found that the timing effect can bring about the increase of aerodynamic efficiency, but due to the limitation of the experimental measurement in the internal measurement of high-speed rotating impeller machinery. So in most cases, the mechanism of internal timing effect of impeller machinery is studied by numerical analysis. In the past numerical analysis often used the method of reducing the flow channel to study the timing effect. As a result of the uneven distribution of upstream blades the timing effect caused by the downstream differential effect. Such treatment is often unconvincing. In this paper, an all-circumferential annular cascade method is used to study the temporal effect. In this paper, the commercial CFD numerical simulation is used as a tool, aiming at the experimental compressor and axial turbine model, the annular cascade grid calculation is proposed to study the sequential effect of axial flow impeller machinery: mesh division is carried out at 50% blade height. A 2-stage (static / rotating / static / rotating) axial flow experimental compressor is selected to carry out the unsteady numerical simulation of two-dimensional cascade, three-dimensional single-channel and full-channel toroidal cascade, and the results are compared and analyzed. It is found that the calculation of full flow channel annular cascade has the advantage of full flow field information. In order to further understand the influence of the change of axial spacing on the performance of the machine, this paper aims at the axial compressor model by changing the axial relative position of the first stage moving blade between the static blades. To study the influence of the relative axial position of the moving blade on the timing effect. At the same time, the flow field of a 2.5 stage (static / rotating / static) axial turbine in a multistage turbine of Hannover University is calculated by the toroidal cascade calculation method. The effect of clocking effect on the aerodynamic performance of the 2.5 stage axial turbine is analyzed. The numerical results of this paper are used to analyze the influence of the boundary layer on the boundary layer and the boundary layer at the wall of the downstream stator blade under different time series positions. Some basic laws of time series effect are summarized. The main reason for the time series effect is that the back row static blade is affected by the circumferential inhomogeneous effect of upstream flow wake. The potential disturbance produced by the periodically varying pressure site at the static and static junction has a significant effect on the development of the boundary layer of the downstream blade. The change of time sequence position will result in beneficial superposition of the disturbance, which will reduce the flow loss on the moving blade surface and achieve the increase of aerodynamic efficiency. (2) through the calculation results of the full-channel annular cascade, the leading edge interference theory of the time-series effect is confirmed: when the wake of the upstream static blade hits the vane leading edge, the wake of the low-energy fluid is mixed with the boundary layer which is the same as the low-energy fluid. Its mixing loss is small, the corresponding aerodynamic efficiency is high, on the contrary, the mixing loss with mainstream high-energy fluid is large and the aerodynamic efficiency is low. The method of grid calculation for annular cascades is suitable for the study of time-series effects with uneven circumferential distribution, and unsteady analysis of all channels can be carried out without reducing the number of blades. This makes it possible to use less computing time to study the multistage blade arrangement, and the unsteady calculation results are due to the introduction of multi-cascade channel calculation. The flow field details of each cascade channel can be captured and reflected in detail, and the pressure fluctuation of each channel is more comprehensive than that of single channel calculation, and the results are of high reliability and practical value in engineering.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2012
【分类号】：TH45

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