基于合成射流的多工况条件下叶片扩压器分离流动控制机理研究

Based on the study on the interaction between the unsteady synthetic jets and the cross flow in the vaned diffuser, the separation flow control mechanism of synthetic jets is revealed, and the control method for restraining and suspending the separation in the vaned diffuser under multi-points conditions is established. Coupled with the measurement with stereoscopic particle image velocimetry, the unsteady flow analysis method, which is suitable for the turbomachinery stage condition, is used to study the effects of slot position, jet angle, actuation frequency and actuation on the performances of the diffuser and stage. Based on the numerical analysis and measured data, the coherent flow structures in the unsteady flow fields of vaned diffuser under different conditions are extracted by the proper orthogonal decomposition (POD) method, and the interaction mechanism between the synthetic jets and the separation vortex in the vaned diffuser is indicated. The numerical and experimental investigations on the flexibility of synthetic jets separation flow control to the operating condition are performed, and the effective control method for the separation control under different conditions in the vaned diffuser is proposed. The study not only possesses high academic significance for the further exploration to the flow control mechanism in the turbomachinery, but also provides the academic support for the improvement of the centrifugal compressor aerodynamic performance, which provides an important guide for practical engineering application.

通过研究非定常合成射流与叶片扩压器通流之间的相互作用机制，揭示合成射流对分离流动控制的机理，并建立合成射流抑制或延迟叶片扩压器多工况条件下分离流动的控制方法。采用叶轮机械级环境下的非定常数值分析方法，并结合三维PIV等实验测试，研究真实机器流动条件下合成射流的开孔位置、射流角度、激励频率和激励强度等对扩压器及压气机级性能的影响；对数值模拟和实验测量流动数据，采用本征正交分解(POD)方法，分析不同工况下叶片扩压器内非定常流动中有重要影响的相干结构，揭示合成射流与叶片扩压器内分离涡之间的相互作用机理；通过变工况下合成射流分离流动控制对其适应性问题进行数值和实验研究，提出合成射流对叶片扩压器内变工况条件下的流动分离进行有效调控的方法。项目研究对于深入认识叶轮机械内分离流动主动控制机理具有良好的学术意义，同时也为进一步提升离心压气机气动性能提供理论支撑，具有重要的工程应用指导价值。

本项目开展了不同工况下离心压气机叶片扩压器内非定常流动演化特征的数值和实验研究，并采用合成射流控制翼型、叶栅和叶片扩压器内的分离流动，探索了离心压气机内流动在不同工况下的分离流动的定常/非定常特征，获得了合成射流激励参数对流动结构和流动损失的影响规律。项目所获得的成果主要包括：（1）在现象揭示层面，揭示了不同工况下离心压气机叶片扩压器内部的非定常流动特征：主、分流叶片出口回流区强度的差异性造成两种流道出口流动掺混强度不同，进而在叶片扩压器入口诱发具有叶轮通道扫掠频率特征的非定常扰动；蜗壳的几何非轴对称性对扩压器叶片压力面瞬时压力的影响在小流量和设计流量工况下主要体现在对频率为叶轮主叶片与分流叶片的通过频率幅值的影响，而在大流量工况下，叶轮主轴旋转频率的幅值也出现较大的非轴对称性；叶片扩压器角涡结构对尖峰先兆的诱导起重要作用，喉部附近角涡的阻塞导致吸力面前缘尖峰先兆扰动‘漏斗’状初始结构的形成。（2）在机理阐释层面，揭示了合成射流对多工况下叶片扩压器流动分离控制的相关机理：合成射流的吹、吸过程增加边界层流体的切向动量，有效抑制叶片吸力面的流动分离，减少由于分离泡和周围高速流体的剪切作用以及下游分离泡破碎、掺混所造成的流动损失，并由于叶片流道的有效通流面积增加，扩压能力得到增强。.截至目前，通过项目研究共发表SCI国际期刊论文7篇，EI收录论文17篇，申请发明专利1项，培养博士研究生3名、硕士研究生4名。.