周向单槽位置对轴流压气机稳定性的影响机理研究

发布时间：2018-05-05 19:56

本文选题：轴流压气机 + 周向单槽　；参考：《中国科学院研究生院(工程热物理研究所)》2015年硕士论文

【摘要】：为了深入认识周向槽位置对压气机失速机制的影响规律,本文针对某叶尖敏感的低速单转子轴流压气机开展数值计算研究。计算与实验结果均表明,位于叶片弦长中部的周向单槽机匣扩稳效果最好,位于叶片前缘下游20%-30%轴向弦长位置的周向单槽机匣扩稳效果最差。分别采用叶顶间隙截面熵云图和机匣壁面轴向剪切应力识别叶顶泄漏流/主流交界面的轴向位置,并根据叶顶泄漏流/主流交界面在节流过程中主要存在两种移动规律和失速扰动的周向传播特征,将周向槽分为准模态和突尖两类机匣。对于突尖类周向槽机匣,叶顶泄漏流/主流交界面在节流过程中持续向通道上游方向移动,并在近失速工况到达叶片前缘位置；对压气机进一步节流会导致叶顶泄漏流/主流交界面溢出叶片前缘,形成突尖型失速扰动。对于准模态类周向槽机匣,叶顶泄漏流/主流交界面在大流量工况下位于周向槽下游,并在节流过程中不断向通道上游方向移动；当叶顶泄漏流/主流交界面与周向槽位置相交时,其轴向位置便不再变动,而且在近失速工况仍位于叶片通道内部并不溢出。为了理解这两种不同的叶顶泄漏流/主流交界面的演变规律,选取位于叶片前缘下游20%轴向弦长且扩稳效果最差的准模态类单槽(简称“前槽”)和位于叶片弦长中部且扩稳效果最好的突尖类单槽(简称“中槽”),对其叶顶端区的流场结构进行分析。结果表明：对于前槽机匣,叶顶泄漏流与周向槽在近失速工况下的相互作用最强,形成强烈的叶顶流体喷入和喷出周向槽的现象。这种喷入-喷出流动带来了两方面的效果：一是,喷入槽内的流动增加了叶片压力面附近主流的轴向速度,抑制了叶顶泄漏流穿过周向槽从而到达叶片前缘的可能性,从而解释了近失速工况下叶顶泄漏流/主流交界面位置不再移动的现象；是,在轴向逆压梯度作用下,向槽内喷入-喷出的流体会在槽内卷起逆时针的“周向槽周向涡”,叶顶间隙区域也会在该周向涡的诱导作用下卷起顺时针的“间隙周向涡”。对于中槽机匣的近失速工况,周向槽只与叶顶泄漏流相互作用,形成较弱的喷入-喷出流动,叶顶端区的流动结构与光壁机匣相似。进一步对周向单槽机匣的叶顶端区轴向动量平衡和通道堵塞分布展开分析,认为对于突尖类的单槽机匣,叶顶流场的轴向动量是影响扩稳效果的主要原因。中槽机匣能够最大程度上减弱叶顶区域间隙泄漏流和槽内流体携带的负轴向动量,抑制叶顶泄漏流/主流交界面的前移和溢出,从而实现扩稳。对于准模态类的前槽机匣,间隙周向涡给叶顶流动带来巨大的堵塞,是导致压气机提前失速的关键诱因。
[Abstract]:In order to deeply understand the influence of circumferential groove position on the stall mechanism of compressor, a numerical study was carried out for a low-speed single-rotor axial compressor with sensitive blade tip. The calculated and experimental results show that the circumferential single-slot casing located in the middle of the chord length of the blade is the best, and the circumferential single-slot casing located at the downstream of the leading edge of the blade is the worst. The tip clearance cross-section entropy cloud map and casing wall axial shear stress are used to identify the axial position of the tip leakage flow / mainstream interface, respectively. According to the two main moving laws and the characteristics of circumferential propagation of stall disturbance in the throttling process of the tip leakage flow / mainstream interface, the circumferential groove is divided into two types of casing: quasi mode and sharp tip. For the circumferential groove casing, the tip leakage flow / mainstream interface continuously moves upstream in the throttling process, and reaches the leading edge of the blade in the near stall condition. Further throttling on the compressor will cause the tip leakage flow / mainstream interface to overflow the front edge of the blade and form a sharp stall disturbance. For quasi-modal circumferential groove casing, the tip leakage flow / mainstream interface is located downstream of the circumferential groove under the condition of large flow rate, and moves to the upstream direction of the channel during throttling. When the tip leakage flow / mainstream interface intersects with the circumferential groove position, the axial position does not change, and the blade channel does not overflow in the near stall condition. In order to understand the evolution of the two different tip leakage flow / mainstream interfaces, Quasimodal grooves with 20% axial chord length located downstream of the blade leading edge and the worst expansion effect ("front groove") and protruded tip grooves located in the middle of the chord length of the blade (referred to as "middle groove") are selected. The flow field structure of the top region is analyzed. The results show that the interaction between the tip leakage flow and the circumferential groove is the strongest under the near stall condition for the front groove casing, resulting in a strong phenomenon of the blade top fluid ejecting into and out of the circumferential groove. The effect of this kind of jet flow is twofold: first, the flow in the slot increases the axial velocity of the main stream near the pressure surface of the blade and inhibits the possibility of the tip leakage flowing through the circumferential groove to reach the leading edge of the blade. This explains the fact that the tip leakage flow / mainstream interface is no longer moving under near-stall conditions; that is, under the action of the axial inverse pressure gradient, the fluid ejected into the tank will roll up the "circumferential vortex" counterclockwise in the tank. The tip clearance region will also roll up the clockwise "gap circumferential vortex" under the inducement of the circumferential vortex. For the near stall condition, the circumferential groove only interacts with the leakage flow at the top of the blade, resulting in a weaker jet / ejection flow, and the flow structure of the tip of the blade is similar to that of the light wall casing. The axial momentum balance and channel blockage distribution in the tip region of the circumferential single-slot casing are further analyzed. It is considered that the axial momentum of the tip flow field is the main reason for the stability expansion of the single-slot casing. The midslot casing can reduce the gap leakage flow in the tip of the blade and the negative axial momentum carried by the fluid in the trough to the maximum extent, and restrain the forward movement and overflow of the tip leakage flow / mainstream interface, so as to realize the stability expansion. For quasi-modal front-grooved casing the annular vortex of the clearance brings huge blockage to the blade top flow which is the key cause of the compressor stall ahead of time.
【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】：硕士
【学位授予年份】：2015
【分类号】：V233

【参考文献】