不同进口条件下向心流转静系盘腔流动特性研究

Flow Characteristics in a Rotor-Stator Cavity with Various Radial Inflow

关键词:  转静系盘腔  向心入流  Batchelor流型  旋转比

Key words:  Rotor-stator cavity  Radial inflow  Batchelor-type  Swirl ratio

摘要:

在典型中小型航空发动机空气系统中，用于高压涡轮冷却、封严的空气一般需要经过离心压气机叶轮背腔，因此掌握以离心压气机叶轮背腔为代表的向心入流转静系盘腔内流动特点及压力分布是保证空气系统各项功能实现的关键。采用数值模拟方法对带有向心入流的转静系盘腔流动开展研究，研究不同来流条件下不同间距比的转静系盘腔流动特点及盘腔内压力分布。结果表明:在间距比G=0.01～0.2内，不同进口条件下盘腔内的流动均为Batchelor流型，即转盘与静盘具有独立边界层，边界层之间为核心区；当径向罗斯比数远小于1时，在核心区内流动满足径向平衡方程，此时盘腔内旋转比分布决定了盘腔内压力分布；对于满足径向平衡方程的此类盘腔，盘腔内流动由进口旋转比[β0]、紊流参数[λT]、间距比G决定；进一步的，得到了不同[β0]，[λT]，G下盘腔出口旋转比及核心区内旋转比变化规律，分析发现小间距比工况下核心区内旋转比满足5/7幂指数关系；大间距比工况下旋转比满足修正5/7幂指数关系，通过得到的旋转比关联式可以计算出盘腔内的压力分布。

Abstract:

In the secondary air system of typical median and small aeroengines， the cooling and rim sealing air for High Pressure Turbine (HPT) is normally drawn through the impeller rear cavity， so the thorough understanding of the flow characteristics and pressure distribution in a rotor-stator cavity with radial inflow， represented by the impeller rear cavity， is the key to realize the functions of secondary air system. The present paper is devoted to the numerical investigations of flow characteristics and pressure distribution in a rotor-stator cavity of different aspect ratio with various radial inflow. Some conclusions are made as following. The basic flow with various radial inflow in the cavity， whose aspect ratio varies between 0.01 and 0.2， belongs to the Batchelor-type family，the two boundary layers adjacent to the disc are separated by a central rotating core. When the radial Rossby number is much smaller than 1， the N-S equation for tangential component of the flow in the rotating core reduces to the balance of the centrifugal force and the radial pressure gradient， therefore the radial distribution of pressure is decided by the central core swirl ratio[β]. The flow in a rotor-stator cavity which satisfies the simplified equation is controlled by the inlet swirl ratio[β0]， turbulent flow parameter[λT]， aspect ratio G. Furthermore， the numerical investigation shows that the radial distribution of[β]can be correlated， in the case of small aspect ratio， according to a 5/7 power-law. On the other hand， in the case of big aspect ratio the radial distribution of β can be correlated according to a modified 5/7 power-law. By acquiring the expression of[β]， the pressure distribution can be calculated in the rotor-stator cavity with a radial inflow.