动叶端区轴向动量控制体分析方法及其在周向槽机匣处理中的应用

发布时间：2018-03-16 11:15

本文选题：轴流压气机　切入点：周向槽机匣处理　出处：《中国科学院研究生院（工程热物理研究所）》2014年博士论文　论文类型：学位论文

【摘要】：多年来,周向槽机匣处理的扩稳效果和扩稳机理一直是叶轮机械领域持久热议的题目。然而囿于压气机流动失稳的复杂过程及各异性,周向槽机匣处理的设计难以形成普适准则,现阶段周向槽的实际应用设计仍需依靠大量试验建立完备的数据库供以筛选。为缩短研制周期,本文从实际应用角度出发,立足于对动叶端区对压气机流动失稳的影响机理的认识,发展了一种作用于动叶端区的控制体分析方法。基于压气机内部流动的三维数值模拟,锁定动叶端区轴向动量为反映流场稳定性的特征量,通过对动叶端区建立控制体量化提取稳定性特征量,由此比较不同周向槽方案扩稳能力,并利用实验验证了该方法在亚音速压气机环境和跨音速压气机环境下的有效性和准确性。研究表明,绝大多数轴流压气机属于叶尖敏感型,发生失速时主流和叶顶泄漏流的交界面自转子前缘溢出,产生突尖形失速先兆,而推动这一交界面在节流过程中不断向前缘移动的机制是动叶端区的轴向动量平衡。基于这一认识,本文提出,加槽后,主流与泄漏流交界面自前缘溢出的趋势将被抑制,压气机的稳定性边界得以拓宽。这一现象可通过加槽后动叶端区的轴向动量分布反映出来。进而,不同周向槽方案的扩稳能力则可通过对比端区轴向动量的分布判断出来。因此,为捕捉这一密切反映压气机流动稳定性的特征参数,本文提出了在动叶端区建立一系列离散控制体的方法,用以量化压气机动叶端区的轴向动量分布情况。以光壁为基准,可通过比较不同周向槽边界下动叶端区轴向动量分布的改变情况,对其相应的扩稳能力进行定量比较,为周向槽初期工程设计提供初选手段。本文选择一典型的跨音速风扇转子NASA Rotor67为研究示例介绍控制体分析方法的建立。首先利用单通道定常／非定常全三维数值模拟得到压气机内部流场,然后在动叶端区合理的径向范围内设置一系列轴向离散的控制体,提供轴向动量沿转子叶顶轴向的定量分布。同时,依次不断累加控制体单元上的轴向动量,可得到一条形似钟形的动量曲线,简称为“钟形曲线”。该曲线的顶点可视为主流和泄漏流交界面在三维空间上的积分效果。对光壁结构和机匣处理结构节流过程中的钟形曲线予以考察,发现随流量不断减小,钟形曲线的顶点不断前移,这与节流过程中主流／泄漏流交界面前移机制相互吻合。加槽后,在同一流量下,钟形曲线的顶点轴向位置被后推,此时主流／泄漏流交界面在周向平均意义上的位置比光壁更靠近通道下游,这一表现反映了周向槽抑制了主流／泄漏流交界面的前溢趋势,加入处理机匣的压气机仍可保持稳定运行。基于对这一扩稳机理的认识,提出对比光壁近失速状态下不同周向槽方案的钟形曲线,可评估出不同方案的扩稳能力。在提出动叶端区轴向动量的控制体分析用于评估周向槽扩稳能力的方法后,分别在一台亚音速和一台跨音速压气机环境下利用实验进一步证实了这一判断方法的有效性。在实验室自有低速轴流压气机实验台IET-LAC上,利用动叶端区控制体分析方法比较了三组双槽的扩稳能力并通过实验验证了钟形曲线预测的结果正确。选取美国圣母大学跨音速轴流压气机ND-TAC为高速压气机转子研究示例,利用钟形曲线对其设计的七种不同周向槽方案的扩稳能力进行预判,并通过实验证实了七种不同周向槽方案的扩稳裕度提升值与钟形曲线的预估结果完全一致。进一步,借助于在亚音速和跨音速压气机环境下的周向槽实验结果发现,利用钟形曲线的几个要素可以判断周向槽扩稳的水平,并可在同一扩稳水平下进一步区分更细致的扩稳能力高低。考虑到周向槽机匣处理的设计还应兼顾压气机的效率和稳定性,在以量化的轴向动量来描述周向槽对压气机稳定裕度影响的启发下,开展周向槽对转子峰值效率影响的初步研究。根据不可逆损失的严格热力学定义,确定熵产为描述压气机流动损失的特征物理量,并利用气动热力学和流体力学基本公式,推导了用于压气机流动控制体形式的熵产表达式。研究中发现,有槽和无槽情况、不同周向槽处理情况的绝热效率分布在动叶端区体现明显差别。因此,对动叶端区和周向槽内分别建立控制体,量化了峰值效率工况下,不同周向槽方案引起的熵产变化。研究结果表明,周向槽内和动叶端区是压气机内部流场中具有较高流动损失的两个区域；不同轴向位置处的周向槽对叶顶流动损失的影响有显著不同。周向槽改善了动叶端区局部的流动,降低了这一部分的不可逆流动损失,而槽内的复杂流动结构又引起了额外的熵产。周向槽对压气机峰值效率的影响是这两方面作用的综合效果。在上述研究基础上,进一步探讨了周向槽几何对扩稳作用的影响。在若干周向槽的几何因素中,选取了三个有代表性的几何参数——周向槽的槽深、槽数和轴向位置。借助周向槽与叶片通道的唯一接触面——开口面为桥梁,分别考察了不同几何边界下,周向槽内和动叶端区控制体上的轴向动量的分布。研究发现,在三个几何因素中,周向槽的轴向位置对扩稳效果的影响最大。通过对各项轴向力的分析中发现,处理机匣的动叶端区轴向动量分布被改变的根本原因是动叶端区的负载被改变。在以上工作基础上,为跨音压气机J69优化多槽方案。利用动叶端区控制体分析方法快速的对比了多种不同周向槽结构,得到了兼顾扩稳和效率性能的周向槽方案。
[Abstract]:Over the years, the circumferential expansion stabilization effect and steady expansion mechanism of grooved casing treatment has been the field of turbomachinery enduring hot topic. However, due to the compressor flow loss of stability and the complex process of specific design of circumferential grooved casing treatment is difficult to form a universal criterion to design the practical application stage week slot still need to rely on a large number of tests to establish a complete database for screening. In order to shorten the development cycle, from the angle of practical application, based on the blade end zone lost the understanding of the mechanism of stable effect on the compressor flow, the development of a role in the control of tip region body dynamic analysis method. The three-dimensional numerical simulation of compressor based on the flow, locking blade end zone for axial momentum characteristics reflect the flow stability, through the establishment of control volume extraction amount on the dynamic stability characteristics of quantitative tip region, which compared the different circumferential groove design ability and stability. The effectiveness and accuracy of the method in subsonic compressor environment and transonic compressor environment are verified by experiments.
The research shows that the vast majority of axial flow compressor belongs to the tip sensitive interface, stall the mainstream and the tip leakage flow from the rotor leading edge overflow, sudden stall inception and pointed, promote the interface mechanism during throttling to front movement is the axial momentum balance rotor end zone. This understanding, based on adding groove, mainstream and leakage flow interface from the front overflow trend will be suppressed, the stability boundary of compressor can be widened. This phenomenon can be added through the slot after the dynamic axial momentum distribution of leaf end zone reflected. Then, different circumferential grooves for the steady expansion ability can be tell from distribution of axial momentum region. Therefore, to capture this closely reflect the flow stability of the compressor characteristic parameters is presented in this paper method of blade end zone in the establishment of a series of discrete control body, used to The momentum distribution of axial compressor rotor tip region. By the light wall as a benchmark, dynamic changes of the momentum distribution of axial blade end zone to the slot boundaries by comparing different weeks, the steady expansion ability for quantitative comparison, for the week beginning players to slot initial engineering design.
This choice of transonic fan rotor NASA Rotor67 a typical example of the control to establish an analysis method. Firstly, using single channel steady / unsteady numerical simulation to get the compressor internal flow, and then moving in the radial range of tip region within a reasonable set up a series of axial dispersion control, quantitative distribution of axial the rotor tip axial momentum. At the same time, in order to control the constant axial momentum body unit, can get a bell shape curve of momentum, referred to as a "bell curve". The curve of the vertex based visual flow and leakage flow integral effect in the interface of 3D space. Examines light wall structure the bell curve structure and casing treatment in throttling process, found with the flow rate decreases, the bell curve vertex constantly moves forward, and the throttling of the mainstream / leakage flow interface before Shift mechanism coincide with each other. And in the same tank after discharge, the axial position of the bell curve by the back vertex, the mainstream / leakage flow interface in the circumferential direction on average position closer to the wall than the light channel downstream, which reflected the circumferential groove inhibited the mainstream / leakage flow interface before the spill, the compressor can be added with casing to maintain stable operation. Understanding of the steady expansion mechanism based on the comparison of light wall near stall condition under different circumferential groove for bell shaped curve, evaluated the steady expansion ability of different schemes.
In the proposed control body movement of tip region of axial momentum analysis method for assessment of circumferential groove steady expansion ability, respectively in a subsonic and transonic compressor environment using a further experiment confirmed the validity of this judgment method. In the laboratory has a low speed axial compressor test rig IET-LAC. The tip area control analysis compared three sets of double slot expansion stability is verified by experiment results. The bell curve predicts the correct selection of Madonna University transonic compressor ND-TAC high speed compressor rotor research example, the design of seven different circumferential groove scheme to predict the steady expansion ability the bell curve, and confirmed by experiments in seven different circumferential groove scheme expanding stability margin and enhance the value of the bell curve prediction results are completely consistent. Further, with the help of subsonic and transonic Experimental results of circumferential grooves in a fast compressor environment show that several elements of bell shaped curve can be used to identify the level of circumferential trough expansion, and further distinguish the more detailed stabilizing ability at the same level of stability.
Considering the design of circumferential grooved casing treatment should also take into account the efficiency and stability of the compressor, in order to quantify the axial momentum to describe the circumferential groove to inspire the influence to the compressor stability margin, pilot study on the circumferential groove of the rotor peak efficiency influence. According to the strict thermodynamic definition of irreversibility, entropy is determined the production for the characteristics of physical quantity description of compressor flow loss, and the use of pneumatic basic formula of thermodynamics and fluid mechanics, formulas for the entropy expression of compressor flow control form. The study found that there is no groove and groove, the circumferential groove processing the adiabatic efficiency distribution in the rotor end zone reflects obviously the difference. Therefore, on the aerodynamic end zone and circumferential groove respectively to establish the control body, quantify the peak efficiency under the condition of entropy production change different circumferential groove caused. The results show that the circumferential groove and rotor end The two area is the area with higher flow loss of the compressor internal flow in different axial positions; Zhou Xiangcao tip flow loss is significantly different. The circumferential slot improves dynamic flow tip area, reduce this part of the irreversible loss of flow, and complex flow structure inside the tank and cause the extra entropy production. Effects of circumferential grooves on the compressor is the peak efficiency of the comprehensive effect of the two functions.
Based on the above research, to further explore the effect of circumferential groove geometry on the steady expansion effect. In a plurality of circumferential groove geometric factors, selected three representative -- are the geometric parameters of circumferential groove depth of the groove, groove number and axial position. Only by means of contact surface circumferential groove and blade passage the opening of the bridge, the different geometric boundary, the circumferential groove and rotor end control on axial momentum. The study found that in three geometric factors, effects of circumferential grooves on the axial position of the maximum stability enhancement effect. Through the analysis of the force the shaft, the rotor casing end zone momentum distribution is changed is the fundamental reason for the axial load rotor end zone is changed. On the basis of the above work, for transonic compressor J69 optimization scheme. By using the dynamic control of multi slot tip area rapid analytical method for comparing the The circumferential grooves with different circumferential grooves are obtained, and the scheme of circumferential grooves with both stability and efficiency is obtained.

【学位授予单位】：中国科学院研究生院（工程热物理研究所）
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TH453

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