刷式密封泄漏特性数值方法研究与实验验证

Numerical Method and Experimental Verification for Leakage Flow Characteristics of Brush Seals

从数值方法和实验测试两方面研究刷式密封的泄漏流动特性。分别建立刷式密封稳态多孔介质模型和瞬态三维流固耦合模型,设计搭建了刷式密封泄漏特性实验台,用实验方法研究了进出口压比和密封间隙对刷式密封泄漏特性的影响,对比验证了两种数值方法的准确性,分析比较了两种数值方法的优缺点。在此基础上,用数值方法研究了刷式密封流场特性,分析了刷丝束内部轴向和径向的压力分布特性以及刷丝的"吹闭效应"。研究结果表明:刷式密封瞬态三维流固耦合模型比多孔介质模型求解精度更高,与实验结果更贴近,但求解时间较长;多孔介质模型计算时间短,但该方法需要对孔隙率和阻力系数进行修正,求解不具有普适性;密封间隙一定时,泄漏量随压比的增大而近似呈线性增大;压降主要发生在刷丝束区域,刷丝束轴向压力分布不均,前排刷丝束之间压力梯度较大;径向压力沿轴向分布不均,末排刷丝束径向压力梯度较大,径向压差的存在是产生"吹闭效应"的重要原因。

The leakage flow characteristics of the brush seals were studied using the numerical methods and the experimental test. The steady-state porous medium model and the transient three-dimensional fluid-solid coupling model of the brush seals were established respectively. Experimental platform for analyzing the leakage flow characteristics was established, and experiments were conducted to test the leakage of brush seals with different pressure ratios and seal clearances. The accuracy of the two numerical methods was compared and verified, and their advantages and disadvantages were also analyzed and compared. Based on this, the flow field characteristics of the brush seals were numerically studied, and the axial and radial pressure distribution characteristics, including the “blowing down” of bristles, were analyzed. The results showed that the accuracy of transient three-dimensional fluid-solid coupling model of brush seals was better than that of porous medium model, and its result was in better agreement with the experimental results, however, it would cost more time. The method of the porous medium model cost less time, but modification of porosity and drag coefficient was required, and its solving applicability was limited. When the seal clearance was fixed, the leakage of the brush seals increased approximately linearly with the increase of the pressure ratio. The pressure drop occurs mainly in the region of bristles bundle, and the axial pressure distribution was uneven with larger pressure gradient among the front bristles. The radial pressure gradient of the rear bristles was relatively large, and the existence of radial pressure difference was an important cause of the “blowing down” effect.