【作者】 李松；

【导师】 郑群；

【作者基本信息】 哈尔滨工程大学 ， 轮机工程， 2011， 硕士

【摘要】 三维、粘性、非定常是叶轮机械内部实际流动的固有特性,非定常特性对叶轮机械内部流动的热功转换具有重要影响,因此研究其内部叶栅的非定常干扰对于改善高负荷涡轮的性能具有重要意义,对非定常特性的认识和研究直接关系到叶轮机械的发展。本文采用区域缩放法、结构化网格、双时间步法、标准k-epsilon湍流模型以及滑移界面法对某高性能涡轮级进行了数值模拟,并分析了涡轮级内的三维非定常流动。传统的叶轮机械设计方法已取得了很大的成功。这些设计和分析方法中引入了一个重要假设,即动叶和静叶都是在相对定常环境下工作。由于在高负荷以及偏离设计工况情况下,忽略非定常流的影响,采用定常假设作出的工程设计并不完全可靠,偏差较大因此涡轮级内的非定常流场数值模拟是现阶段计算流体力学研究的重要领域。本文通过对叶轮机内非定常流动的研究,详细讨论了叶排间干扰对涡轮级气动性能的影响。涡轮级内常见的非定常现象包括：激波、尾迹、脱落涡、壁角涡、通道涡以及泄露涡等。在每个静叶通道内可以观察到周期性的流动。在跨音速工况下,涡轮级静叶尾缘会出现激波,该激波会对下游动叶通道内的流动产生周期性的影响。该涡轮级内的涡运动包括：静叶叶片尾缘附面层引起的脱落涡；根脚区两个端壁附面层相互干扰形成的壁角涡；动叶通道内转子旋转运动产生的通道涡；存在叶尖漏流时出现的泄露涡。在定常和非定常模拟中,均可观察到同样形式的顶部泄漏涡。本文对上游尾迹与涡轮叶栅通道涡的相互作用机理进行了分析,探讨了非定常流动物理本质,发掘非定常流的潜力,为发展非定常设计手段提供思路。数值计算表明：上游尾迹的非定常作用一方面增强了叶栅通道涡,使得流动损失增大；另一方面能够一定程度上抑制通道涡沿着流动方向的发展,对控制损失起到正面作用,端区的综合非定常效应取决于两者之间的平衡。本文数值模拟使用的是商业计算流体力学软件Ansys-CFX,通过数值模拟可对高性能涡轮级内的非定常流动有定性的了解,数值模拟的结果可为涡轮级的非定常优化以及设计提供一定的参考。更多还原

【Abstract】 The internal flow of turbo-machinery is intrinsically three-dimensional, viscous and unsteady, the unsteady characters of the internal flow have an important influence on the thermal power conversion, and investigate the unsteady interactions in turbine cascade is meaningful for improving the performance of high loading turbine. So its study and research related to the development of turbo-machinery directly. In this paper a transonic high-pressure turbine stage was modeled and simulated using domain scaling method, structured grid, dual time step method, standard k-epsilon turbulence model and sliding interface to analyze the three-dimensional unsteady flow in the High Performance Test Turbine stage.Traditional methods of turbo-machinery design have made a great success. These methods are based on such an important assumption that rotors and stators operate in relative steady flow conditions. As the unsteady fluctuation of flow field is neglected, deviation from real case is thus raised by the steady design methods particularly in the case of high-load and of design condition. Turbine stages of the unsteady flow field numerical simulation is at the present stage of the important areas of computational fluid dynamics research. The work in the present dissertation aims at exploiting unsteady flow phenomena to extract useful information for unsteady design methods. The paper presents the investigation of the effects of blade row interaction on the aerodynamics of the turbine stage in detail. The unsteady phenomena include the shockwave, wake, shedding vortex, endwall vortex, passage vortex and leakage vortex, etc. Periodic flow is observed for each vane passing period. A stator trailing edge shock appears as the turbine stage is operating at transonic conditions. The shock alters the flow condition in the rotor section periodically. The vortex simulated in this article include the shedding vortex induced by the vane trailing edge boundary layer, the endwall vortex generated by the endwall boundary layer interaction, the passage vortex generated by the rotor rotation, and the leakage vortex generated by the tip clearance flow. The same patterns in tip leakage flow structures were observed in both unsteady and steady simulations. The upstream wake-passage vortex interactions in turbine cascade were simulated, and the flow mechanisms were analyzed. Numerical simulations were applied as main tool to study unsteady flow phenomena. Numerical results indicate that periodic upstream wakes can enhance the vorticity of passage vortex, which increases losses. On the other hand, upstream wakes can suppress the streamwise vorticity development of passage vortex to some extent, which reduces losses. The combined unsteady effect in the endwall region depends on the balance of above two factors.The CFD code used to simulate the fluid field is the commercial software Ansys-CFX. Through the numerical simulation, it can make a qualitative looking of unsteady flow in the turbine stage and the numerical result can provide an objective for the unsteady optimization and the design of turbines.更多还原