螺旋篦齿-刷式密封泄漏特性实验和数值研究

Experimental and Numerical Investigations on the Leakage Flow Characteristics of Helical-Labyrinth-Brush Seals

为探究刷丝束安装位置对螺旋篦齿-刷式密封泄漏流动特性的影响,基于多孔介质模型和计算流体动力学(CFD)技术,数值研究了刷丝束安装在螺旋篦齿上游或下游两种螺旋篦齿-刷式密封在不同压比(1~1.3)和转速(0~10000r/min)条件下的泄漏流动特性。同时,在压比为1~1.3和转速为0~2000r/min的条件下,实验测量了刷丝束安装在螺旋篦齿上游的密封泄漏流动特性。在实验工况范围内,数值模拟得到的泄漏量和腔室压力与实验值吻合良好。结果表明:泄漏气流主要经刷丝束与转子间隙流入下游;相比刷丝束安装在下游,刷丝束安装在上游时的泄漏量及其对转速变化的敏感度更小。螺旋篦齿和转子环形台阶沿轴向交错排列,导致周向静压分布不均和下游压力高于上游压力;两种密封转子面静态气流作用力的x轴分量方向相反,y轴分量方向也相反,且相比刷丝束安装在下游,刷丝束安装在上游时静态气流作用力的x轴分量绝对值更大,而y轴分量绝对值更小;静态气流作用力的绝对值随压比升高而显著升高,对转速变化不敏感。

To investigate the effect of bristle pack position on the leakage flow characteristics of helical-labyrinth-brush seals,based on the computational fluid dynamic(CFD)analysis and a porous medium model,this paper investigates the leakage flow characteristics of two types of helical-labyrinth-brush seals with a bristle pack element installed upstream or downstream of the helical-labyrinth tooth under various pressure ratios(1-1.3)and rotational speeds(0-10000 r/min).Meanwhile,the leakage flow characteristics of the seal with a bristle pack element installed upstream of the helical-labyrinth tooth are experimentally measured at the pressure ratios of 1-1.3 and rotational speeds of 0-2000 r/min.The CFD-derived leakage flow rate and cavity pressure agree well with the experimental data in the whole range of test conditions.Most of the leakage airflow flow downstream from the clearance between the bristle pack and the rotor.Compared with the seal with a bristle pack element installed downstream,the seal with a bristle pack element installed upstream possesses less leakage flow rate,and the leakage flow rate is less sensitive to the changes in speed.The helical tooth and the annular steps on the rotor are designed with staggered pattern along the axial direction,resulting in an uneven distribution of circumferential static pressure,and the phenomenon that the downstream pressure is higher than the upstream pressure.The x-axis component and y-axis component of static aerodynamic forces of the two seals are in opposite directions.Compared with the seal with a bristle pack element installed downstream,the seal with a bristle pack element installed upstream has a larger absolute value of x-axis component of the static airflow force and a smaller absolute value of yaxis component.The absolute value of static aerodynamic force of the two seals increases significantly with the pressure ratio,and is not sensitive to the speed change.