DBD等离子体诱导涡结构控制附面层流动研究

发布时间：2018-01-03 05:24

本文关键词：DBD等离子体诱导涡结构控制附面层流动研究　出处：《哈尔滨工业大学》2017年博士论文　论文类型：学位论文

【摘要】：随着主动流动控制技术的快速发展,介质阻挡放电(DBD)等离子体流动控制技术作为一种新型的主动流动控制技术,已在全球范围内引起了研究者们的关注。DBD等离子体激励器作为一种主动流动控制设备,具有输入能量少、结构简单(无需移动部件)、控制灵活、反应快速等优点。随着研究的开展,等离子体激励器被逐步地应用在流动分离、转捩流动、湍流流动以及气膜冷却等流动控制领域,并实现了较好地控制效果。本文首先利用PIV实验测试技术开展了等离子体对平板壁面附近流动特性影响的研究。实验结果表明,等离子体激励器对流场的诱导作用能够显著增加近壁区内的流动速度,速度增幅?U最大可达来流速度的8.8%,而最大影响范围?δ约为附面层厚度的60%,二者均出现在激励器正极中心附近处;等离子体对流场的影响幅度与来流速度、激励电压的大小有关,来流速度相同时,近壁区附近等离子体的影响范围随激励电压的增加而增加;激励电压相同时,影响范围随来流速度的增加而下降。其次,基于公开的凸包实验数据对比讨论了不同亚格子模型的特点,并利用PIV实验结果修正了Shyy等人提出的电场线性化简化模型中的模型参数,从而建立了平板近壁区流场等离子体流动控制的大涡模拟方法。通过对DBD等离子体激励器作用下的平板流场进行模拟发现,等离子体对近壁区流动的影响主要体现在:一方面是通过其对激励器附近局部区域低能流体的直接“加能”作用而实现的,另一方面则是利用生成的“诱导涡”增强了主流区与近壁区流体之间的能量交换所导致。随后采用大涡模拟方法将DBD等离子体激励器简化模型和流动控制方程耦合联立求解,探讨了DBD等离子体作用下的平板、凸包流动的流场结构特点。通过对流场的分析表明,在DBD等离子体激励器作用下,流场壁面附近区域形成了一系列的正负“涡对”结构,“涡对”的产生促进了壁面附近区域内流体与主流流体之间的能量交换。在平板流动中,诱导“涡对”有效地提高了附面层内的流体速度,但其在向下游迁移的过程中不断地远离壁面,对流动的控制作用不断减弱。在凸包流动中,诱导“涡对”的迁移可以促使分离区内低能流体向下游的移动,从而减小了分离区的大小,甚至消除分离。最后开展了利用DBD等离子体激励器诱导“流向涡”,进行气膜冷却流场流动结构控制的研究。基于前文的仿真模型探讨了单激励器以及多激励器作用下的流场“流向涡”的分布,分析了“流向涡”的发展同激励器的激励强度、激励器极板间距以及激励器极板长度之间的关系。研究结果表明,DBD等离子体激励器诱导出的壁面射流流经壁面后与来流发生作用,从而诱导卷曲形成“流向涡”,该“流向涡”在向下游迁移的过程中不断膨胀并远离壁面。而相向布置的等离子体激励器诱导流动发生卷曲从而形成相向运动的“流向涡”。“流向涡”之间的互相作用,促进了其在法向方向的迁移。通过Q准则的等值面分布识别出吹风比M=1.0的条件下,冷却孔出口附近以及下游区域的大涡拟序结构。涡结构中主要以发卡涡的分布为主,流向截面内表现为旋向相反的涡对结构(CVP)。发卡涡在向下游迁移的过程中,其明显存在向着法向以及展向方向发展的速度。这也从侧面反映出冷却射流的核心区向周围扩散,逐步远离壁面的趋势。这种趋势不利于冷却气体对高温部件的表面进行冷却。此外,研究过程中深入分析了不同等离子体激励器布置形式对气膜冷却效果的改善作用。在对计算结果的分析中建立了不同等离子体激励器布置形式下,冷却孔附近大涡拟序结构的发展演化规律,通过探讨流场参数的分布规律获得了“诱导涡”对冷却流场涡结构的控制机制。常规的等离子体激励器通过诱导壁面射流,有效地减弱了冷却孔出口下游近壁区的涡强度,导致涡破碎现象提前发生。但壁面射流在流场下游逐渐远离壁面的特性却不可避免的增强冷却气体沿法向迁移的能力,使得其对壁面的冷却效果有所下降。诱导流向涡结构的布置形式,能够诱导冷却气体产生三维的涡结构,该涡结构与气膜孔下游的大涡结构相互抑制,能够有效地减弱冷却气膜在法向方向的运动能力,促进冷却气流的核心区向壁面偏移,有效地改善了冷却气体对高温部件表面的冷却性能。
[Abstract]:With the rapid development of active flow control technology, dielectric barrier discharge (DBD) plasma flow control as a new type of active flow control technology, has attracted attention in the global scope of.DBD plasma actuator researchers as a kind of active flow control equipment, with less input energy and simple structure (without moving parts), flexible control, fast response and other advantages. With the development of the studies, the plasma actuator is gradually used in flow separation, transition flow, turbulent flow and gas film cooling control field, and achieve a better control effect. This paper uses PIV test technology to carry out research on the influence of flow characteristics near the plasma flat wall. Experimental results show that the flow field induced by the plasma actuator can significantly increase the flow velocity in the near wall region, speed Increase? U maximum flow rate of 8.8%, while the maximum range of influence? Delta is about the thickness of boundary layer 60%, two are in the vicinity of the center of positive influence amplitude exciter; plasma on the flow field and the flow velocity, the excitation voltage on the size of the flow at the same speed, the influence range of the near wall near the plasma increases with excitation voltage; voltage phase at the same time, influence range with the flow velocity increased. Secondly, comparing the convex hull of public experiment data is discussed based on the characteristics of different sub grid model, and use the PIV test results of the correction of the electric field of linear Shyy et al proposed simplified model parameter model in, so as to establish a flat near wall region flow plasma flow control method of large eddy simulation. Simulation found by plate flow of DBD plasma actuator under the action of plasma in recent The effect of wall flow is mainly reflected in: on the one hand by the actuator near the local area of low-energy fluid directly "add" and realize the function, the other is using the "vortex" enhances the main flow region and near wall fluid between the exchange of energy caused by the later. Eddy simulation methods DBD plasma actuator flow control equations of the simplified model and the coupled simultaneous solution, discusses the tablet DBD under the action of plasma, the flow structure characteristics of convex hull flow. Through the analysis of the flow field in the DBD show that the plasma actuator under the action of regional flow field near the wall to form a series of positive and negative "vortex on the structure." on promoting the emergence of vortex "between the near wall region of fluid and mainstream fluid exchange of energy. In the plate flow, the vortex induced to effectively improve the flow of the boundary layer Speed, but in the process of migration to downstream continuously away from the wall, the weakening effect on the flow. In the convex hull "vortex flow, induced migration of" can promote the separation zone of low-energy fluid downward movement, thereby reducing the size of the separation zone, and even eliminate the separation. Finally we carry out the use of DBD plasma actuator induced "streamwise vortex", studied the film cooling flow control structure. The distribution of flow field simulation model of the above "single actuator and actuator under the action of streamwise vortex" based on the analysis of the development of streamwise vortex "incentive strength with the actuator, the relationship between the actuator and the plate spacing the actuator plate length. The results show that the wall jet DBD plasma actuator induced through the wall and flow effect, thereby inducing formation of streamwise vortex" curl "The" vortex "in the process of migration to downstream in the ever expanding and away from the wall. The opposite arrangement of the plasma actuator flow induced curling to form the opposite movement" vortex "." the interaction between the streamwise vortex ", the migration direction in law promoted by Q rules. The equivalent surface distribution to identify the blowing ratio M=1.0 under the conditions of large vortex cooling holes near the outlet and downstream regions of the coherent structures. The vortex structure is mainly in the distribution of Hairpin Vortex dominated flow section in the form of reverse rotating vortex on the structure (CVP). In the process of Hairpin Vortex downstream migration in the there was normal and spanwise direction toward the speed of development. This is also reflected from the side of the core area of cooling jet to spread around, step away from the wall surface trend. This trend is not conducive to the surface of the cooling gas of high temperature components Cooling. In addition, in the course of the study, in-depth analysis of the effects of different plasma actuator arrangement on film cooling effect. In the analysis of the calculation results of the established different plasma actuator arrangement, cooling holes near the large eddy coherent structure evolution law of development, through the distribution of flow field parameters obtained "control the mechanism of vortex induced vortex cooling structure. The plasma actuator induced by conventional wall jet, effectively reduced the intensity of vortex near wall region downstream of the cooling hole outlet, leading to vortex breakdown phenomena occur in advance. But the wall jet in the downstream flow gradually away from the wall surface properties are enhanced cooling gas inevitably along the normal direction the ability of migration, the decline of the cooling effect. The wall layout induced streamwise vortex structure, can induce the cooling gas to produce three-dimensional The vortex structure, mutual inhibition of large vortex structures downstream of the vortex structure and film hole, can effectively weaken the cooling gas film in the normal direction of the athletic ability, promote the core area of the wall offset of cooling airflow, and effectively improve the performance of cooling gas on surface of the high temperature parts.

【学位授予单位】：哈尔滨工业大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O53

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