Unsteady Aerodynamic characteristics of Turbine Cascade in Negatively Stalled Region

在一个均匀的入口流中，在一个涡轮级联中，通过数字分析获得了不稳定的空气动力学特征，使用漩涡方法，以及级联中的流动性特征被讨论。粒子性重要性是在研究涡轮机级联在负堵塞的流动区域中工作的流动性特征。流量被假定为两个维度和不复杂的，数字结果与两个维度风隧道实验的结果进行了部分比较，在固定级联的叶片上的表面压力分布也被测量，下游摇摆流动也是由不稳定的流量探测器制造的。一种类型的涡轮机喷嘴级联被选定为分析对象，主要结果被汇总为后续：“当一个涡轮机喷嘴级联被放置在一个大的消极因素下，导致边缘分离出现在刀片压力表面上，而分离的流水线沿着下游平滑地沿着刀片表面流动。”从理论上看，从领先边缘遮蔽的静止涡流的行为完全不同，因为在压缩机级联的情况下，涡流现象如此不稳定，因为旋转停滞并不明显。实验性地测量了压力分布在负填充刀片表面上，同意井的数值计算通过涡流方法输送出来。涡轮喷嘴级联的小梯度角度分布是由其决定的，并且不稳定的航空动力和时刻通过改变频率和叶片间角度来计算的。停滞的闪光灯被发现在结果上。它被结合在一起，使消极停滞的涡轮喷嘴级联的流动性特征更像是那些可能的流动器的相同级联。这很可能是在一个强大的加速流动通道的涡轮喷嘴级联中的停滞流动的本质。

Unsteady aerodynamic characteristics of an turbine cascade oscillating in a uniform inlet flow were obtained by numerical analyzes with use of the vortex method, and the flutter characteristics of the cascade were discussed. Particular importance was put in studying the flutter characteristics of the turbine cascade working in negatively stalled flow region. Flow was assumed two-dimensional and incompressible, and the numerical results were partly compared with the results of two-dimensional wind tunnel experiment, where surface pressure distributions on the blades of stationary cascade were measured, and the downstream wake flow traverses were also made by unsteady flow probes.A typical turbine nozzle cascade was selected as the object of analysis, and the main results are summarized as follows :・When a turbine nozzle cascade is placed under a large negative incidence, the leading edge separation appears on the blade pressure surface and the separation stream line goes downstream smoothly along the blade surface.・Accordingly, the behavior of stalled vortices shed from the leading edge is completely different from that of vortices in the case of compressor cascades, and the unsteady flow phenomena such as rotating stall do not appear.・Experimentally measured pressure distributions on the negatively stalled blade surface agreed well with the numerical calculation carried out by the vortex method.・Small amplitude angular oscillation of the turbine nozzle cascade was considered, and the unsteady aerodynamic forces and moment were calculated with changing reduced frequency and inter-blade phase angle for wide ranges. Occurrence of stall flutter was discussed on the results.・It was concluded that the flutter characteristics of the negatively stalled turbine nozzle cascade is rather similar to those of potential flutter of the same cascade. This is probably due to the nature of the stalled flow in a strong accelerating flow channel of the turbine nozzle cascade.